Oscar Laurent

Cyril Chelle-Michou

Jean-François Moyen

Simon Couzinié
email: simon.couzinie@univ-st-etienne.fr

Marc Poujol

Michaël Mintrone

Pierre Bouilhol

Adrien Vezinet

Linda Marko

• Armin Zeh

Olivier Vanderhaeghe

Arnaud Villaros

Véronique Gardien

Cadomian S-type granites as basement rocks of the Variscan belt (Massif Central, France): Implications for the crustal evolution of the north Gondwana margin

Keywords: crust evolution, zircon UPbHf isotopes, Cadomian orogeny, Variscan orogeny, collisional magmatism, French Massif Central. Chapter North Gondwana margin Cadomian orogeny Variscan orogeny

The formation of the continental crust is a major consequence of Earth dierentiation.

Understanding how the crust formed and evolved through time is paramount to locate the vast mineral deposits hosted therein and address its inuence on the global climate, ultimately aecting the development of terrestrial life. Recent advances on the topic of continental crust evolution beneted from improvements of analytical techniques enabling in situ measurements of UPbHfO isotope compositions in zircon, a widespread accessory mineral of continental igneous rocks. The time constrains derived from the U Pb chronometer coupled with the petrogenetic information retrieved from HfO isotope signatures are currently used to unravel the diversity and succession of magmatic events aecting the continental crust at the regional and global scales.

This study reconstructs the evolutionary path followed by the crust segment today exposed in the eastern part of the French Massif Central (FMC), a portion of the Variscan belt of Western Europe, with the aim to investigate the potential aws of the zircon record of crust evolution. In this scope, the origin and geodynamic signicance of the constituent FMC lithological units are tackled by combining conventional petrological observations with zircon UPbHfO isotope data. The results obtained following this integrated approach are then confronted to the conclusions that would have been drawn solely from zircon isotopic signatures, taken out of their petrological context, as is commonly performed in studies investigating crust evolution. The oldest rocks of the FMC correspond to Ediacaran (590550 Ma) meta-sediments deposited in back-arc basins along the northern Gondwana margin. Such basins were fed by a mixed detritus originating from the adjacent Cadomian magmatic arc and a distal Gondwana source, presumably the Sahara Metacraton. Partial melting of these meta-sediments at the Ediacaran/Cambrian boundary led to voluminous S-type granitic magmatism, pinpointing a rst major crust reworking event in the FMC. The origin of anatexis likely stems from the transient thickening of the hot, back-arc crust caused by the attening of the Cadomian subduction. Subordinate melting of the depleted backarc mantle at that time is also documented. During the Lower Paleozoic, rifting of the northern Gondwana provoked coeval crust and (limited) mantle melting. Mantle-derived igneous rocks show markedly diverse trace element and isotopic signatures, consistent with a very heterogeneous mantle source pervasively modied by the Cadomian subduction. Finally, the Variscan collision resulted in crustal melting as evidenced by the emplacement of S-type granites and the formation of migmatite domes, the spatial distribution of which being partly controlled by the crustal architecture inherited from pre-orogenic events. Synchronous intrusion of mac mantle-derived magmas and their dierentiates testify for Variscan post-collisional new continental crust production in the FMC.

Two major inconsistencies exist between these results and the zircon record. First, zircon Hf model ages would point to substantial Mesoproterozoic crust formation in the FMC whereas more than 60% of the crust is actually Neoproterozoic in age. Second, new additions to the continental crust volume during the Variscan orogeny are not recorded even though 5 to 10% of the exposed crust formed at that time. The origin of both discrepancies inherently lies in the mixed isotopic signature carried by many zircon grains. Such equivocal information can only be detected when additional petrological constrains on the zircon host rocks are available and provide guidance in interpreting the zircon record of crust evolution.

thought at rst glance. Dare not forget anyone! If so, my apologies... This section will be full of french language interludes, depending on the person(s) considered.

I will start rst with the members of the committee. Thanks for having accepted to evaluate this work and, for some of you, having travelled quite a distance for the defence.

Mes remerciements vont ensuite à Jean-François Moyen. Tellement de choses se sont passées depuis notre première rencontre un soir d'orage n aout 2011 à la Part-Dieu (ce n'est pas l'accroche d'un lm de série B, le lecteur pourra s'assurer de la véracité de ces faits auprès des intéressés). Six ans plus tard, je tiens à te remercier pour la grande liberté que tu m'as laissé dans l'accomplissement de mes travaux, ton soutien/conance quand je me suis engagé dans tous ces (multiples) projets et pour avoir partagé ton expertise sur le magmatisme granitique. J'ai particulièrement apprécié toutes nos discussions de synthèse (à tendances agrégatives) sur la typologie des granites.

My sincere gratitude goes to Gary Stevens. Thanks for your patience and the time you spent sharing your knowledge on experimental and granite petrology. It was a great experience to interact with you on these topics and I have learnt a lot through this.

I also wish to express my gratitude to the Stellies group. Thanks Sara for having shared with me the experimental despair and scientic excitement that goes along with this peculiar activity (I did not nd any alternative way of saying it). It was a pleasure to work with you at the lab and solve some thermodynamics. Andrew "Toodle-oo" thanks so much for having improved my understanding and wording of english so well! Telling kak with you was delighting, especially at lunch time or with a good craft at ... Craft. To the artists and computer scientists: thanks to Nora, Rentzia, Nicola, Pieter and Albert for all the everlasting discussions about life and so many topics (special thanks to the guys for having kindly accommodated me). Shawn merci beaucoup! for your kindness and good mood. Francesco the Italian Stallion is greatly acknowledged for having saved me while I was locked inside the geology building along with a potential fugitive. I very much enjoyed our chats they helped a lot to unwind! un grand merci à Cynthia pour tous les moments passés à Lombardi, Cassis, sur la N1 ("Turn around! Turn around!"), Dorp Street Deli ou sur le Rooiplein. Tu as grandement contribué à mon acclimatation sud-africaine et malgré tous les petits troubles au labo, on aura quand même bien rigolé. J'en prote pour remercier Sylvain pour nous avoir envoyé du rêve pendant 15 jours avec deux loustics que j'évoquerai un peu plus tard...(et pour avoir créé THE nickname le plus utilisé durant ma thèse). My thanks also go to the CAF and Geology managers, whose help and encouragements during my stays were greatly appreciated (Madelaine, Herschel, Angelique, Mareli, Rianna, George, Loxie, Jeanne). Dorothy is thanked for making the admin tasks so easy. Thanks to Thomas for being such a pleasant tennis challenger and for the fun we had at quizznight (this includes Valby). I must say a massive merci! to Matthew/Matt/Matiou for all the great moments we have spent together since january 2014 when we rst met in Grahamstown. Thanks so much for having organized so many things while I was in South Africa: hiking, playing cricket with Ben (gasp...), snorkeling, quizznighting, listening to crazy bands (including at ParkO ), maintaining a scientic thrill with all the Rcrust and S-type discussions, having Whiskey parties at your parents' (thanks to them and Corbin for their kindness... but don't tell me kak!). It was basically awesome! Finally, thanks for sharing your views on so many topics, it is really inspiring.

Un retour en France maintenant. Tout d'abord, un grand merci aux amis castrais (Flo, Sophie, Bobi)! Nos escapades plus ou moins lointaines (Sivens, Verdon, Réunion, etc...) m'ont à chaque fois fait le plus grand bien. Merci aussi de m'avoir fait (re)rencontrer des personnes vraiment sympas (qui se reconnaitront). Le temps est venu, ma foi, de châtier un temps soit peu mon language s'agissant d'aborder la situation dudit Docteur Arnaud J. You know how much I owe you buddy! Ainsi, je vous prie d'agréer, monsieur, l'expression de mes remerciements les plus sincères. Nos discussions, des plus ranées, égayent mon quotidien depuis fort longtemps déjà, puissent le druide de Cubservies, le Marshall de Stellies et le mazout de la Salvetat en témoigner. J'en prote pour remercier Emelyne, Marie et Amaury pour ces agréables moments passés en sud-afriquie, à Paris ou dans la Montagne Noire (berceau de la civilisation)! Au tour des Lyonnais d'y passer. Mes remerciements vont tout d'abord au Docteur Alexandre A. dont la justesse de raisonnement n'a que peu d'égal. Ce fut un plaisir d'échanger sur tant de sujets. J'ai aussi énormément appris et clarié de concepts à travers nos discussion. Merci à toi. Un grand merci aussi à Jean-Loup qui, depuis 7 ans déjà, partage une grande variété de moments/pensées/émotions avec moi. Un petit mot pour la promo ENS 2010 (Hélène, Gaelle Number 4, Amo, Fatma et al.) que j'ai pu revoir au compte-gouttes pendant ces 3 ans. Merci au Docteur (lui aussi!) Paul Anto. from Ariège (je te mets dans les Lyonnais car je t'ai rencontré à cette époque) pour cette mémorable conférence à Florianopolis. On se sera vraiment bien marré! Mes remerciements vont également au Professeur Olivier "of the letter" et à Clara pour leur bonne humeur, leur accueil toujours chaleureux et nos longues discussions introspectives qui sont une source d'enrichissement personnel certain. Pour terminer l'étape lyonnaise, je tiens à remercier les locataires du R6 (Véro, Gwelt, Manu, Maxime, Arnaud, Ivan, David, Marianne, Hervé...) et de la prépa agreg pour leur accueil et leur patience.

Récupérer un Simon qui sort de 5 mois d'écriture c'est pas de la tarte ! J'enchaine ainsi avec les Stéphaniens (bah oui fallait bien que je la fasse, Juan Miguel Moulin-style!). Je remercie en premier lieu toutes les personnes de la FST qui, par leur bonne humeur, professionalisme et bienveillance, ont rendu mon expérience au labo agréable. Pour citer quelques coupables je pense entre autres au duo Anne-Marie/Pascal, à Colette, Anne-Sab, Anne-Mag, Damien, Bertrand, Marie, Véronique, Peter, Adélie, Lucile et al. Parmi les étudiants qui se sont succédés merci à Pierre (PyPy) et Théo qui m'ont bien aidé sur le terrain et en magnétisme. Je vais faire des "special thanks" à Jérôme qui a partagé "l'expérience Chasseradès" avec moi. Merci pour ta patience sur le terrain, tes conseils et ta gentillesse. Special thanks aussi pour June qui a été d'un grand soutien pendant ces 3 ans. Merci pour tout mate! Je fais un paragraphe pour les "historiques", ceux qui ont hanté le bureau des thésards (certains le canapé) pendant si longtemps. J'ai nommé Gaëlle ("On va manger"), Gautier et Boguie. Merci pour ces moments passés un peu partout (au bureau, sur le terrain, en conf, à Stellies). Merci au nouvel arrivant Antonin "Justinho" qui a pour notre plus grand bonheur élevé le niveau d'humour parmi nous! Et enn le champion en titre, qui franchit tous les cols hors catégorie (y compris les voies blanches à bloc à brac), sans qui ces 3 ans de thèse n'auraient pas été ce qu'ils ont été, j'ai nommé l'illustre Dotorre Adrien Vezinete (prononcer vézinété). Je voulais faire une phrase stylée en mode "Si son fromage se rapporte à son plumage..." mais je n'ai pas réussi à la nir. Je resterais donc correct et me contenterais de te remercier sincèrement pour tous ces moments passés ensemble.

C'est le tour des papys ingueurs ! La génération 79-86 qui m'a accompagné durant ce périple que fût la thèse (et pour certains déjà bien avant). Merci à Arnaud Vill. "l'homme qui voit tout fondre plus vite que son ombre" pour ta bonne humeur, ton soutien quand des oiseaux de mauvaise augure tournaient autour de moi et pour toutes les discussions qu'on a pu avoir sur la complexité extrême de la nature. Merci à Cyril Che.-Mich. avec qui on se sera bien éclaté à refaire le monde... Néoproterozoique! Merci à Luc-SD pour sa prise en charge sociale du Simon "en rédaction" (broyer du caillou y a que ça de vrai pour se détendre). On aura bien rigolé à Gambon et dans le Velay Han Solo! Les Special Thanks sont de retour pour Pierre lo bouiol (lieu-dit commune de Prévenchères). Merci pour tout ce que tu m'as appris, ta gentillesse et ton soutien/disponibilité lors de la rédaction. Ce fut un plaisir de travailler avec toi. Un autre Special pour Oscar LauLau.

Tu as plus qu'intensément contribué à l'accomplissement de ce travail. Merci d'avoir ainsi partagé ton savoir et de m'avoir apporté ton soutien permanent et inconditionnel.

Merci également pour ton accueil à Frankfurt/Zuerich et pour les discussions multiples (sérieuses comme imitatoires) qu'on a pu avoir ces 4 dernières années.

Looks like the French interlude was quite long. One last drop of English though for Vojt¥ch Janou²ek, for his kindness and the tremendous job he and his colleagues have done with GCDkit, this way I shall say that he substantially contributed to the achievement of my PhD! Thank you.

Il est certains de mes professeurs qui, par leurs enseignements et conseils, m'ont particulièrement inspiré et, de fait, ont indirectement contribué à la réalisation de ce travail. Je voudrais ainsi sincèrement remercier mes enseignants de classe préparatoire Christine V., Olivier L. et Olivier A. ainsi que Hervé B. de l'ENS de Lyon.

Last but not least, merci à toute ma famille pour leur soutien ainsi qu'à Marine pour son innie patience, son aide sur le terrain (notamment sa perception redoutable des linéations) et son soutien au quotidien durant la rédaction. Un grand Merci! 3 Meta-igneous rocks of the Upper Gneiss Unit in the Monts-du-Lyonnais area By denition, the continental crust is the section of the continental lithosphere lying above the Moho seismic discontinuity and laterally bounded by the continental slope, at the transition zone with the low-lying oceanic crust [START_REF] Davidson | The signicance of Phanerozoic arc magmatism in generating continental crust[END_REF]Rudnick and Gao, 2003). The continental crust has an average thickness of ∼ 35 40 km [START_REF] Mooney | CRUST 5.1: A global crustal model at 5°Ö 5°[END_REF] and multi-methods studies based on surface heat ow measurements, seismic proles and large-scale geochemical surveys concluded that it has a bulk andesite/diorite composition [START_REF] Christensen | Seismic velocity structure and composition of the continental crust: A global view[END_REF][START_REF] Gao | Chemical composition of the continental crust as revealed by studies in East China[END_REF][START_REF] Holbrook | The seismic velocity structure of the deep continental crust[END_REF][START_REF] Rudnick | Nature and composition of the continental crust: a lower crustal perspective[END_REF]Rudnick and Gao, 2003;[START_REF] Wedepohl | The composition of the continental crust[END_REF]. A similar conclusion was drawn by [START_REF] Taylor | Island arc models and the composition of the continental crust[END_REF] and Taylor and McLennan (1985;1995) but these authors' estimates relied on a partisan mode of new crust formation and not uniquely on quantiable geological observations.

Based on seismic data, the continental crust may be subdivided into three layers of contrasted P-wave velocities and chemical compositions (see Fig. 1.1): the upper and middle crusts (each corresponding to c. 30% of the bulk section, sometimes grouped together) are granodioritic while the lower crust (the remaining 40%) has a gabbroic composition [START_REF] Christensen | Seismic velocity structure and composition of the continental crust: A global view[END_REF][START_REF] Gao | Chemical composition of the continental crust as revealed by studies in East China[END_REF][START_REF] Rudnick | Nature and composition of the continental crust: a lower crustal perspective[END_REF]Rudnick and Gao, 2003;[START_REF] Wedepohl | The composition of the continental crust[END_REF]. The boundary between these crustal domains is sometimes underlined by the so-called Conrad seismic discontinuity (Fig. 1.1).

The upper crust typically features volcanic, plutonic and sedimentary lithologies which metamorphosed equivalents (up to the amphibolite-facies) are common in the middle crust. The lower crust is built up by granulite-facies meta-igneous (mostly gabbroic) and metasedimentary rocks (Rudnick and Gao, 2003). Coupled to its lithospheric mantle root, the silica-rich continental crust forms thick, buoyant and poorly subductable masses at the surface of the Earth.

1.1.2 From mantle to continental crust...

The continental crust has been extracted from the Earth mantle for more than 4 billion years [START_REF] Bowring | Priscoan (4.00-4.03 Ga) orthogneisses from northwestern Canada[END_REF][START_REF] Iizuka | 4.2 Ga zircon xenocryst in an Acasta gneiss from northwestern Canada: Evidence for early continental crust[END_REF]. Importantly, rocks of granodiorite compositions are not in equilibrium with the mantle, meaning that the upper and middle crusts must originate from the dierentiation of a basaltic precursor (the most common magma type formed by mantle melting). Such process may occur through: (i) fractionation of primary basaltic magmas, (ii) melting of pre-existing mac lithologies or/and (iii) weathering and erosion of similar rocks [START_REF] Anderson | Parental basalts in subduction zones: Implications for continental evolution[END_REF][START_REF] Rudnick | Nature and composition of the continental crust: a lower crustal perspective[END_REF][START_REF] Taylor | The geochemical evolution of the continental crust[END_REF], even though the latter eect has proven less signicant than magmatic processes (Hawkesworth and Kemp, 2006a). In this manuscript, the term crustal dierentiation, generally taken as the whole set of phenomena that leads [START_REF] Chapman | Thermal gradients in the continental crust[END_REF]. The "Upper Crust" gathers both the upper and middle crusts described in text. Figure from [START_REF] Wedepohl | The composition of the continental crust[END_REF].

to a stratied crust section, is strictly used in a crust evolution perspective and will refer to the conversion of basaltic precursors into upper/middle crustal intermediate/felsic lithologies via the above-mentioned processes.

Clearly, the basaltic ux from the mantle contrasts with the bulk crust andesite composition and entails that formation of new crust necessarily requires a mac component to return back to the mantle, most probably via the foundering of dense cumulates and/or residues left after upper/middle crust extraction [START_REF] Arndt | An open boundary between lower continental crust and mantle: its role in crust formation and crustal recycling[END_REF][START_REF] Davidson | The signicance of Phanerozoic arc magmatism in generating continental crust[END_REF][START_REF] Kay | Creation and destruction of the lower continental crust[END_REF][START_REF] Rudnick | Making continental crust[END_REF]Rudnick and Gao, 2003;[START_REF] Taylor | Island arc models and the composition of the continental crust[END_REF]Taylor and McLennan, 1985;[START_REF] Zandt | Active foundering of a continental arc root beneath the southern Sierra Nevada in California[END_REF]. This would also account for the fact that the lower crust composition is not complementary to that of the upper/middle crust (Hawkesworth and Kemp, 2006a).

1.1.3 ...in a one-or two-stage process?

Production of new continental crust necessitates: (i) addition of mantle-derived magmas to a pre-existing crustal volume; (ii) dierentiation of the basaltic precursor; (iii) foundering of mac residual materials in the mantle. These successive steps may occur concurrently or be temporally decoupled leading to two contrasted views on how new crust is formed.

A rst model taken as "one-stage" or "island-arc" argues that accretionary orogens (in the sense of [START_REF] Scholl | Implications of estimated magmatic additions and recyling losses at the subduction zones of accretionary (non collisional) and collisional (suturing) orogens[END_REF] are the main locus of new crust production, at least in Phanerozoic times [START_REF] Arculus | Origins of the Continental Crust[END_REF]Hawkesworth and Kemp, 2006a;[START_REF] Vogel | Silicic ignimbrites within the Costa Rican volcanic front: evidence for the formation of continental crust[END_REF]. There, melting of the mantle wedge supplies large volumes of basaltic magma which evolve by fractional crystallization (and possible assimilation) in the arc crust towards granodiorite compositions meanwhile the mac dense cumulates are delaminated in the mantle (see Kelemen et al., 2003, and references therein). In other words, new, dierentiated crust forms in a short time span, in a single geodynamic setting. This model is supported by the fact that some trace element ratios displayed the bulk continental crust markedly resemble that of island arc basalts (IAB, see [START_REF] Arculus | Origins of the Continental Crust[END_REF]. Besides, estimates of the magma volumes erupted in dierent settings indicate that convergent margins host the largest input of mantle-derived magmas, thus most likely to generate substantial amounts of new crust.

Alternatively, a "two-stage" model postulates that the processes at stake in the generation of new continental crust do not operate synchronously (at geological time scale).

A rst mantle melting event would supply basaltic magmas to the continental crust [START_REF] Downes | The nature of the lower continental crust of Europe: petrological and geochemical evidence from xenoliths[END_REF] or a transient reservoir such as oceanic plateaux [START_REF] Albarede | The growth of continental crust[END_REF] and the MOR oceanic crust (Niu et al., 2013). After a period of geological quiescence, changes in the magmatic/tectonic regime e.g. continentcontinent collision or oceanic plateau accretion would provoke melting and associated dierentiation of the basaltic precursor (Niu et al., 2013), forming new continental crust. Delamination of dense mac residua would take place synchronously [START_REF] Arndt | An open boundary between lower continental crust and mantle: its role in crust formation and crustal recycling[END_REF]. This way, the model temporally separates the mantle extraction stage from the dierentiation stage (melting plus foundering of the most mac components).

Crust recycling, growth and reworking

The inherent dynamics of subduction zones promote the foundering of upper-crustal, intermediate to acid lithologies in the mantle by sediment subduction and subduction erosion [START_REF] Clift | Controls on tectonic accretion versus erosion in subduction zones: Implications for the origin and recycling of the continental crust[END_REF][START_REF] Stern | Subduction erosion: Rates, mechanisms, and its role in arc magmatism and the evolution of the continental crust and mantle[END_REF][START_REF] Von Huene | Tectonic erosion along the Japan and Peru convergent margins[END_REF]. Such phenomenon clearly destroys continental crust materials and is referred to as crust recycling. The latter do not encompass the loss in the mantle of mac cumulates/residues left after crustal dierentiation, independently necessary to account for the bulk crust composition.

The extent of crust recycling would be as high that the net gain to the crust volume (the dierence between crust formation and destruction) would currently be null [START_REF] Clift | Crustal redistribution, crustmantle recycling and Phanerozoic evolution of the continental crust[END_REF][START_REF] Scholl | Implications of estimated magmatic additions and recyling losses at the subduction zones of accretionary (non collisional) and collisional (suturing) orogens[END_REF]Stern and Scholl, 2010). In the following, crustal growth will be regarded as the positive imbalance between new crust production and crust destruction, after subtraction of the baseline mac cumulates/residues foundering.

Lastly, crust reworking is taken as the magmatic processes that re-shape pre-existing, dierentiated crustal lithologies, i.e. sediments and intermediate/felsic igneous rocks. Reworking does not participate to crust dierentiation from a crust evolution perspective (see previous section). Nevertheless, the upwards transport of crust-derived magmas certainly reinforces the continental crust chemical layering and contributes to its stabilisation by concentrating the incompatible, heat-producing elements in its uppermost part [START_REF] Michaut | Secular cooling and thermal structure of continental lithosphere[END_REF]. Weathering and sedimentation are not included in this denition of crust reworking because erosion of basaltic rocks do participate to the dierentiation of the crust.

How to track crustal growth If the continental crust is not currently growing, the present-day 7.2 × 10 9 km 3 of crustal materials provide unambiguous evidence for past crustal growth. Challenging questions are: when was the continental crust extracted from the mantle and at which pace? Was crustal growth a continuous or discrete process?

Addressing them converts into estimating the crustal residence time of each fragment of the present-day crust, i.e. when was it rst incorporated to the crustal volume, before being potentially reworked during subsequent geological events? If the very rst seed of newborn crust is a mantle-derived basaltic magma, new additions to the continental crust are best pinpointed by the crystallization of intermediate to acid magmatic rocks originating from such basaltic precursors (Hawkesworth and Kemp, 2006a;b), i.e. by the crust dierentiation stage. On these grounds, recent advances on the topic of crustal growth beneted from the study of zircon ZrSiO 4 , primarily encountered as an accessory mineral of intermediate to acid igneous rocks (Hoskin et al., 2000). Such advances are summarized in the next section.

The zircon record of crust evolution

The reader can found detailed discussions on this topic in the excellent reviews of Hawkesworth et al. (2010); [START_REF] Cawood | The continental record and the generation of continental crust[END_REF] and [START_REF] Roberts | The zircon archive of continent formation through time[END_REF].

Zircon UPbHfO isotope compositions

UPb geochronology

When zircon crystallizes, it incorporates U but virtually no Pb and thus can be dated via the UPb geochronometer. This mineral is extremely resilient to weathering, erosion, transport, and high-grade metamorphism (see discussion in Mezger and Krogstad, 1997) so that it preserves the record of the earliest events on Earth [START_REF] Amelin | Nature of the Earth's earliest crust from hafnium isotopes in single detrital zircons[END_REF]. In the past 20 years, the improvement of laser ablation techniques enabled to routinely date in situ portions of zircon crystals (Jackson et al., 2004;[START_REF] Hirata | U-Pb isotope geochronology of zircon: Evaluation of the laser probe-inductively coupled plasma mass spectrometry technique[END_REF]. Such strong spatial control coupled to high quality cathodoluminescence imaging of the grain interiors allows to unravel complex zircon crystallization histories (e.g. [START_REF] Vavra | Internal morphology, habit and UThPb microanalysis of amphibolite-to-granulite facies zircons: geochronology of the Ivrea Zone (Southern Alps)[END_REF].

HfO isotopes

Zircon accommodates noticeable amounts of Hf in its lattice (up to the %) but few Lu [START_REF] Fujimaki | Partition coecients of Hf, Zr, and REE between zircon, apatite, and liquid[END_REF], such that in situ measurements of the YbLuHf isotope compositions allows to retrieve the zircon 176 Hf/ 177 Hf ratio which is close to that of the melt/uid from which the zircon crystallized [START_REF] Fisher | Accurate Hf isotope determinations of complex zircons using the laser ablation split stream method[END_REF][START_REF] Grin | Zircon chemistry and magma mixing, SE China: In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes[END_REF]Hawkesworth and Kemp, 2006a;Woodhead et al., 2004). As Lu/Hf ratios are fractionated during mantle melting (Lu is more compatible than Hf ), extracted crustal materials and mantle residues develop contrasted time-integrated Hf isotope signatures (reported as ε Hf normalized to the CHUR, Bouvier et al., 2008;[START_REF] Patchett | Evolution of the continental crust and mantle heterogeneity: evidence from Hf isotopes[END_REF] with the crust becoming less radiogenic and the mantle more radiogenic than the CHUR. This way, the 176 Hf/ 177 Hf ratio of a magmatic zircon grain recalculated at the time its crystallization is a rst-order indicator of the crust-vs. mantle-origin of the local magma batch surrounding the newly formed mineral (Fig. 1.2).

Furthermore, the zircon oxygen isotope composition, notably the 18 O/ 16 O (expressed as δ 18 O normalized to the SMOW, see [START_REF] Valley | Oxygen isotopes in zircon[END_REF] can also be measured by laser uorination or ion microprobe and allows to retrieve the δ 18 O of the host magma [START_REF] King | Oxygen isotope ratios of Archean plutonic zircons from granitegreenstone belts of the Superior Province: indicator of magmatic source[END_REF][START_REF] Valley | Oxygen isotopes in zircon[END_REF][START_REF] Valley | 4.4 billion years of crustal maturation: oxygen isotope ratios of magmatic zircon[END_REF]. The mantle is fairly homogeneous in terms of O isotopes [START_REF] Eiler | Oxygen isotope variations of basaltic lavas and upper mantle rocks[END_REF] and shows a value of +5.3 ± 0.6 (2σ, Valley et al., 1998). Materials that experienced low-T supra-crustal weathering show higher δ 18 O than the mantle while interaction with high-T uids yields lower δ 18 O (see Fig. 1.3).

A window onto the source of granitic magmas Altogether, zircon Hf(O) isotope compositions yielded new constraints on the petrogenesis of intermediate to acid igneous rocks, pinpointing the respective contributions of the crust and the mantle in the evolution of several magma types (Appleby et al., 2009;Belousova et al., 2006;[START_REF] Goodge | Origin of Mesoproterozoic A-type granites in Laurentia: Hf isotope evidence[END_REF][START_REF] Grin | Zircon chemistry and magma mixing, SE China: In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes[END_REF]Hawkesworth and Kemp, 2006a;[START_REF] Kemp | Hf isotopes in zircon reveal contrasting sources and crystallization histories for alkaline to peralkaline granites of Temora, southeastern Australia[END_REF]2007;[START_REF] Murgulov | Crustal evolution in the Georgetown Inlier, North Queensland, Australia: a detrital zircon grain study[END_REF][START_REF] Pietranik | Heterogeneous zircon cargo in voluminous late Paleozoic rhyolites: Hf, O isotope and Zr/Hf records of plutonic to volcanic magma evolution[END_REF].

These studies interpreted the spread of 176 Hf/ 177 Hf ratios displayed by magmatic zircons at the time of crystallization as reecting the mixing, at source or during emplacement, between crust-and mantle-derived materials, even though such views have been challenged (e.g. Farina et al., 2014;Villaros et al., 2012).

From there emerged the idea that zircon grains preserve the best record of the origins of magmatic rocks as they allow to track processes otherwise undepictable by "traditional" whole-rock geochemical studies. On these grounds, many workers attempted to Figure 1.2: Zircon Hf isotope systematics and calculation of "depleted mantle model ages" for a zircon grain crystallized at 1.5 Ga. Several values are used for the 176 Lu/ 177 Hf ratio of the host material. A 176 Lu/ 177 Hf of 0.021 is rather typical of a mac igneous rock and 0.015 of upper crustal lithologies. Inspired from [START_REF] Roberts | The zircon archive of continent formation through time[END_REF].

decipher the evolution of the continental crust by considering the Hf(O) systematics of detrital and magmatic zircon grains out of their rock matrix [START_REF] Belousova | Rejuvenation vs. recycling of Archean crust in the Gawler Craton, South Australia: Evidence from UPb and Hf isotopes in detrital zircon[END_REF]2010;[START_REF] Condie | UPb isotopic ages and Hf isotopic composition of single zircons: The search for juvenile Precambrian continental crust[END_REF][START_REF] Stern | Subduction erosion: Rates, mechanisms, and its role in arc magmatism and the evolution of the continental crust and mantle[END_REF]Dhuime et al., 2012;Hawkesworth and Kemp, 2006;[START_REF] Iizuka | Detrital zircon evidence for Hf isotopic evolution of granitoid crust and continental growth[END_REF]Kemp et al., 2006;2015;[START_REF] Kirkland | Constraints and deception in the isotopic record; the crustal evolution of the west Musgrave Province, central Australia[END_REF]Naeraa et al., 2012;[START_REF] Pietranik | Episodic, mac crust formation from 4.5 to 2.8 Ga: New evidence from detrital zircons, Slave craton, Canada[END_REF][START_REF] Roberts | Increased loss of continental crust during supercontinent amalgamation[END_REF][START_REF] Spencer | Not all supercontinents are created equal: Gondwana-Rodinia case study[END_REF][START_REF] Wang | Growth rate of the preserved continental crust: II. Constraints from Hf and O isotopes in detrital zircons from Greater Russian Rivers[END_REF][START_REF] Zeh | Baltica-and Gondwana-derived sediments in the Mid-German Crystalline Rise (Central Europe): Implications for the closure of the Rheic ocean[END_REF][START_REF] Zeh | The oldest zircons of AfricaTheir UPbHfO isotope and trace element systematics, and implications for Hadean to Archean crustmantle evolution[END_REF]. The methodology and main results are summarized hereafter.

Timing of crustal growth from zircon UPbHf(O) data

The present-day age distribution of crustal materials at the surface of the Earth (Fig.

1.4) reects the time-integrated end-product of the crustal growth process. That being said, part of the today-exposed continental crust is built up from materials that have been reworked, i.e. their geological age does not reect that of extraction from the mantle. This is the case for (meta-)sediments, which encompass crustal materials formed before erosion and deposition, and also for crust-derived granitoids that typically re-shape preexisting crustal lithologies.

UPb age distributions

The original idea behind this approach is that zircon being mostly encountered in intermediate to felsic igneous rocks (Hoskin et al., 2000), the distribution of crystallization ages would record periods of marked crustal dierentiation and new additions to the continental crust volume. Many workers built up databases of UPb crystallizations ages for zircon grains extracted from both today-exposed magmatic rocks and detrital (meta-)sediments in an attempt to be as representative as possible of the Earth geological record. Detrital zircons are regarded as repositories of the pre-erosive magmatic history of the detritus they are hosted by. [START_REF] Rino | Major episodic increases of continental crustal growth determined from zircon ages of river sands; implications for mantle overturns in the Early Precambrian[END_REF] proposed to lter the signal of crust recycling out by: (i) discarding metamorphic zircon grains and, (ii) only focusing on the core of grains showing evidence for multiple crystallization events. The age retrieved from the core is taken as representative of that of the genuine crustal material before reworking. A rst-order criterion to discriminate between metamorphic and magmatic zircon grains is given by the zircon Th/U ratios measured concomitantly on the same UPb spot (Rubatto et al., Figure 1.3: Ranges of δ 18 O observed in dierent crustal and mantle reservoirs. Figure from [START_REF] Roberts | The zircon archive of continent formation through time[END_REF].

2001 ;[START_REF] Rubatto | Zircon trace element geochemistry: partitioning with garnet and the link between UPb ages and metamorphism[END_REF].

The resulting distribution shows marked peaks at c. 0.3, 0.6, 1.0, 1.9 and 2.7 Ga [START_REF] Rino | Major episodic increases of continental crustal growth determined from zircon ages of river sands; implications for mantle overturns in the Early Precambrian[END_REF] and converts into a step-like crustal growth curve with periods of signicant and short-lived additions to the crustal volume (Fig. 1.4). Importantly, statistical analyses of the UPb databases of [START_REF] Condie | Episodic zircon age spectra of orogenic granitoids: The supercontinent connection and continental growth[END_REF] and [START_REF] Voice | Quantifying the timing and rate of crustal evolution: Global compilation of radiometrically dated detrital zircon grains[END_REF] yielded identical results than [START_REF] Rino | Major episodic increases of continental crustal growth determined from zircon ages of river sands; implications for mantle overturns in the Early Precambrian[END_REF]'s, even though the formers did not apply any lter to minimize the impact of crust reworking ages. It comes from this that either [START_REF] Rino | Major episodic increases of continental crustal growth determined from zircon ages of river sands; implications for mantle overturns in the Early Precambrian[END_REF]'s procedure is inecient or crust recycling is a second-order feature within zircon UPb age databases. The latter possibility has not been fully investigated but petrological evidence for voluminous silica-rich magmas originating from melting of pre-existing, dierentiated crustal lithologies (typically intermediate to acid igneous and metasedimentary protoliths, e.g. [START_REF] Chappell | Two contrasting granite types[END_REF]2001) strongly suggests that a substantial proportion of the UPb dates attests to crust reworking and not new crust formation.

An alternative approach consisted in focusing only on grains extracted from todayexposed igneous rocks as conclusions on the magma origin could be drawn from wholerock major, trace element and SrNd-Hf isotope data. This way, [START_REF] Condie | Episodic continental growth and supercontinents: a mantle avalanche connection?[END_REF] and [START_REF] Condie | Episodic zircon age spectra of orogenic granitoids: The supercontinent connection and continental growth[END_REF] showed that the age distributions of (putatively) mantle-derived granitoids does feature the same peaks observed by [START_REF] Rino | Major episodic increases of continental crustal growth determined from zircon ages of river sands; implications for mantle overturns in the Early Precambrian[END_REF]. Yet, limitations of such method are of two types: (i) there is still an ongoing debate around the source of some magma types (see for instance the case of I-type granites, [START_REF] Clemens | The enigmatic sources of I-type granites: The peritectic connexion[END_REF] references therein); (ii) sampling of igneous rocks is in essence biased [START_REF] Condie | Episodic zircon age spectra of orogenic granitoids: The supercontinent connection and continental growth[END_REF] and the contribution of rocks which have been eroded and their detritus mixed in sedimentary basins cannot be accounted for, even though such detritus still takes part of the continental crust.

Following the puzzling results of UPb database analyses, several studies relied on another potential indicator of the genuine signal of new crust formation: the Hf model ages.

Hf model ages

The 176 Hf/ 177 Hf(t) ratio of each zircon grain can be converted into a crustal residence model age corresponding to the time at which the crustal source of the zircon-hosting 2004) and [START_REF] Condie | Episodic zircon age spectra of orogenic granitoids: The supercontinent connection and continental growth[END_REF], on Hf model ages from Belousova et al. (2010) and Dhuime et al. (2012), on the age of present-day continental areas from [START_REF] Hurley | Pre-drift continental nuclei[END_REF]. Are also depicted the main periods of supercontinent amalgamation (from Campbell and Allen, 2008). Figure inspired from [START_REF] Roberts | The zircon archive of continent formation through time[END_REF].

magma would have been extracted from the mantle. Such calculations assume that a precursor crustal material was formed at time T with a given 176 Lu/ 177 Hf ratio. Radioactive decay led to a time-dependent increase of its bulk 176 Hf/ 177 Hf. Reworking of the precur- sor material at time t produced silica-rich melts that crystallized zircon, encapsulating its 176 Hf/ 177 Hf(t). Provided an assumption on the value of the precursor 176 Lu/ 177 Hf ratio, it becomes possible to retrieve the time T at which the precursor and a reference mantle were at isotopic equilibrium, thus bracketing the timing of new crust formation (Fig. 1.2). The reference mantle most often considered is the Depleted Mantle, for which a range of compositions have been described [START_REF] Grin | The Hf isotope composition of cratonic mantle: LAM-MC-ICPMS analysis of zircon megacrysts in kimberlites[END_REF]Naeraa et al., 2012).

Resulting model ages are accordingly termed "depleted mantle model ages" (T DM ).

However, petrogenetic studies conducted on several granite types and mentioned above revealed that the zircon HfO systematics may record the sampling of reservoirs with contrasted isotope compositions. When this is the case, the Hf model age retrieved from each zircon grain is arguably of mixed origin and thus meaningless from a crust evolution perspective (Arndt and Goldstein, 1987). Besides, mixing trends cannot be identied when looking at detrital zircon populations. Consequently, Hawkesworth and Kemp (2006a) and Kemp et al. (2006) suggested to use the δ 18 O of the zircon domain analysed for UPbHf isotopes as a tool to identify the presence of mixed components in the magma from which the grain crystallized. This way, excluding analyses with δ 18 O >6.5, presumably reecting the reworking of supra-crustal sedimentary materials in the magma, retrieved model ages would selectively indicate the time at which new crust was formed and hitherto preserved, thus contributing to crustal growth.

Many studies interrogated the ever-growing zircon UPbHf(O) isotope databases and observed that the distributions of Hf model ages (with or without screening out high δ 18 O grains) dier from that of UPb crystallization ages (Belousova et al., 2010;Dhuime et al., 2012;2017;Hawkesworth and Kemp, 2006;[START_REF] Iizuka | Detrital zircon evidence for Hf isotopic evolution of granitoid crust and continental growth[END_REF]Kemp et al., 2006;[START_REF] Wang | Growth rate of the preserved continental crust: II. Constraints from Hf and O isotopes in detrital zircons from Greater Russian Rivers[END_REF]. Clearly, crustal growth curves derived from Hf model ages rather point to a continuous increase of the crust volume with a potential inexion at 3 Ga expressing a slowdown in the rate of crustal growth (Fig. 1.4).

ε Hf -time relationships

An alternative approach to decipher the timing and mechanisms of crust evolution consists in estimating the age and evolutionary path of a given crust segment. The associated methodology relies on the regional temporal evolution of the ε Hf (t) displayed by detrital and/or magmatic zircon grains from a set of crustal lithologies. For instance, episodic oscillations of the ε Hf (t) has been linked to variations of the mantle-derived magma supply and new crust production, in line with the regional geodynamic evolution [START_REF] Boekhout | A Hf-isotope perspective on continent formation in the south Peruvian Andes[END_REF]Kemp et al., 2009). A similar interpretation has been proposed at the global scale by [START_REF] Roberts | Increased loss of continental crust during supercontinent amalgamation[END_REF].

Besides, identication ε Hf -time arrays is regarded as reecting inner-crustal reworking processes, the age of the original crustal precursor corresponding to the array intercept with the evolutionary trend of the Depleted Mantle reservoir [START_REF] Block | Paleoproterozoic juvenile crust formation and stabilisation in the south-eastern West African Craton (Ghana); New insights from UPbHf zircon data and geochemistry[END_REF][START_REF] Eglinger | New insights into the crustal growth of the Paleoproterozoic margin of the Archean Kéména-Man domain, West African craton (Guinea): Implications for gold mineral system[END_REF]Kemp et al., 2009;[START_REF] Marschall | The Annandagstoppane Granite, East Antarctica: Evidence for Archaean Intracrustal Recycling in the Kaapvaal-Grunehogna Craton from Zircon O and Hf Isotopes[END_REF][START_REF] Petersson | Mesoproterozoic continental growth: UPbHfO zircon record in the Idefjorden Terrane, Sveconorwegian Orogen[END_REF][START_REF] Zeh | Hafnium isotope record of the Ancient Gneiss Complex, Swaziland, southern Africa: evidence for Archaean crust-mantle formation and crust reworking between 3.66 and 2.73 Ga[END_REF]. Furthermore, a spread in ε Hf (t) at a given age between the evolutionary trends of two crustal reservoirs is taken as: (i) evidence for mixing between both end-members (Linnemann et al., 2014;Orejana et al., 2015;[START_REF] Petersson | Zircon UPbHf evidence for subduction related crustal growth and reworking of Archaean crust within the Palaeoproterozoic Birimian terrane, West African Craton, SE Ghana[END_REF]2017); or, (ii) a genuine record of continuous crust production with reworking at the given time t and preservation of the original model age range (Lancaster et al., 2011).

Enhanced crust production or preservation bias

In the following, a controversial aspect of the zircon UPbH(O) record of crust evolution is addressed through the prism of the YingYang conceptualization developed by Stern and Scholl (2010), i.e. net crustal growth occurs when there is a positive imbalance between new crust formation and crust destruction. Figure from Campbell and Allen (2008).

A rst range of models consider that UPb age peaks reect periods of enhanced crust production to such an extent that it substantially outweighed crustal losses [START_REF] Condie | Episodic continental growth and supercontinents: a mantle avalanche connection?[END_REF]2004;[START_REF] Iizuka | Detrital zircon evidence for Hf isotopic evolution of granitoid crust and continental growth[END_REF][START_REF] Rino | Major episodic increases of continental crustal growth determined from zircon ages of river sands; implications for mantle overturns in the Early Precambrian[END_REF]. This view is supported by the coeval peak of mantle-derived magma additions [START_REF] Condie | Episodic continental growth and supercontinents: a mantle avalanche connection?[END_REF][START_REF] Condie | Episodic zircon age spectra of orogenic granitoids: The supercontinent connection and continental growth[END_REF]. As a matter of fact, such periods of juvenile magmatic are-ups would match those of supercontinent amalgamation (Campbell and Allen, 2008), suggesting causality (Fig. 1.5).

At the other side of the spectrum, several studies consider that there was no substantial burst of crust production during supercontinent assembly [START_REF] Condie | Episodic zircon age spectra of orogenic granitoids: The supercontinent connection and continental growth[END_REF]Condie et al., 2011;[START_REF] Condie | Growth of continental crust: a balance between preservation and recycling[END_REF]Hawkesworth et al., 2009;Lancaster et al., 2011;Spencer et al., 2015). These workers advocate that the age peaks rather reect the high preservation potential of igneous rocks formed during continent collision episodes and would thus be of little signicance in unravelling the timing of crustal growth. This viewpoint relies on the examination of the relative magma productivity and preservation potential of materials formed at each step of the supercontinent cycle (e.g. Hawkesworth et al., 2009). From this, magmatic rocks generated at the end of the subduction stage and during the main collision would be best preserved due to their location in the core of newly formed continental masses (Hawkesworth et al., 2010).

Such conclusion has been challenged by Stern and Scholl (2010) who argued that collisional episodes result in a marked loss of the continental crust volume, incompatible with an over-representation of collisional events in the geological record. In support to this interpretation would be the systematic negative excursion of the average ε Hf (t)

during periods of super-continent assembly [START_REF] Gardiner | The juvenile hafnium isotope signal as a record of supercontinent cycles[END_REF][START_REF] Roberts | Increased loss of continental crust during supercontinent amalgamation[END_REF][START_REF] Voice | Quantifying the timing and rate of crustal evolution: Global compilation of radiometrically dated detrital zircon grains[END_REF].

The discussion on the relative balance between crust production and its recycling back to the mantle throughout Earth history is extremely challenging to conduct, both at the regional and global scale for several reasons summarized below.

Some complications

The detrital zircon age distribution is often taken as representative of the timing of intermediate to acid magmatism, arguably related to crust production and dierentiation.

Yet, eroded igneous rocks do not contribute evenly to the detrital record as they do not have the same amount of zircon to deliver (Dickinson, 2008;[START_REF] Moecher | Dierential zircon fertility of source terranes and natural bias in the detrital zircon record: Implications for sedimentary provenance analysis[END_REF] clearly introducing a bias in the detrital record. Besides, results retrieved from the model age approach are severely conditioned by (see discussion in Payne et al., 2016;[START_REF] Roberts | The zircon archive of continent formation through time[END_REF]): (i) the 176 Lu/ 177 Hf ratio considered for the zircon crustal host; (ii) the reference model mantle composition retained; (iii) the premise that zircon Hf(O) isotope composition considered alone is a good repository of the petrogenesis of its host magma (Fig. 1.6, see also [START_REF] Nebel | The eect of sediment recycling in subduction zones on the Hf isotope character of new arc crust, Banda arc, Indonesia[END_REF][START_REF] Roberts | Sedimentary recycling in arc magmas: geochemical and UPbHfO constraints on the Mesoproterozoic Suldal Arc, SW Norway[END_REF]. The eect of such uncertainties are very dicult to monitor at the global scale even though [START_REF] Dhuime | Continental growth seen through the sedimentary record[END_REF] recently advocated that the two former are negligible.

Figure 1.6: Illustration of one caveat of the zircon HfO approach. Compilation of 2586 magmatic rocks for which both zircon HfO isotopes and a petrogenetic model are available. Taken out of their context, zircon HfO isotopes fail to unravel the mantle vs. crust (or mixed) origin of the magma from which the zircon crystallized. Figure from Payne et al. (2016).

Rationale

As demonstrated in the previous section, unravelling regional to global crust evolution from zircon UPbHfO isotope compositions is a promising approach. Yet, its design is quite recent as most studies have been conducted in the past 10 years. Consequently, some aspects of the methodology still require evaluation (see section 1.2.4). As a matter of fact, the approach has proven most ecient and the uncertainties best accounted for when additional petrological constraints were available on the zircon host rocks [START_REF] Block | Paleoproterozoic juvenile crust formation and stabilisation in the south-eastern West African Craton (Ghana); New insights from UPbHf zircon data and geochemistry[END_REF][START_REF] Eglinger | New insights into the crustal growth of the Paleoproterozoic margin of the Archean Kéména-Man domain, West African craton (Guinea): Implications for gold mineral system[END_REF]Kemp et al., 2009;Laurent and Zeh, 2015;[START_REF] Nebel | The eect of sediment recycling in subduction zones on the Hf isotope character of new arc crust, Banda arc, Indonesia[END_REF][START_REF] Roberts | Sedimentary recycling in arc magmas: geochemical and UPbHfO constraints on the Mesoproterozoic Suldal Arc, SW Norway[END_REF][START_REF] Zeh | Archaean to Proterozoic Crustal Evolution in the Central Zone of the Limpopo Belt (South Africa-Botswana): Constraints from Combined U-Pb and Lu-Hf Isotope Analyses of Zircon[END_REF].

The work presented in this manuscript focuses on a c. 30,000 km 2 area located in the eastern part of the Massif Central (France), one of the largest exposure of the Variscan belt in Europe. A critical feature of this geological region is that it would have been sequentially shaped by both the Neoproterozoic Cadomian accretionary and the Paleozoic Variscan collisional orogenies thus oering the opportunity to investigate the relative extent of crust production/reworking in both geodynamic settings.

A new set of zircon UPb (N=2,715), Hf (N=347) and O (N=131) isotope compositions in close conjunction with geochemical, structural and monazite geochronological data from regional magmatic et metamorphic lithologies is used to: (i) reconstruct the history and evolution of this crust segment; (ii) address the nature and potential aws of the zircon record of crust evolution.

1.4 Geological background 1.4.1 The Variscan belt of Western Europe

General overview

The Variscan belt of Western Europe is part of the Paleozoic Peri-Atlantic collisional orogenic system extending over 5000 km from the Ouachitas in the USA to the Caucasus (Matte, 1986a;b;1991). It developed as a result of the convergence between Gondwana and LaurentiaBaltica [START_REF] Franke | Variscan plate tectonics in Central Europe -current ideas and open questions[END_REF]2000;Kroner and Romer, 2013;Matte, 1986a) leading to the assembly of Pangea, the latest supercontinent on Earth (Rogers and Santosh, 2003).

NS shortening would have been accommodated by the closure of at least two oceanic domains (Fig. 1.7) (i) the GaliciaMassif Central, between Gondwana and the microcontinent Armorica; and (ii) the Rheic ocean, between Armorica and Avalonia, another continental ribbon docked to the LaurentiaBaltica landmass during the Caledonian orogeny [START_REF] Franke | The mid-European segment of the Variscides: tectonostratigraphic units, terrane boundaries and plate tectonic evolution[END_REF][START_REF] Matte | Accretionary history and crustal evolution of the Variscan belt in Western Europe[END_REF]2001;[START_REF] Rey | The Scandinavian Caledonides and their relationship to the Variscan belt[END_REF]. Diachronic and assymetric subductions (towards the North for the GMC, South for the Rheic, see Fig. 1.7) resulted in the Variscan belt showing a "fan-like" shape (Fig. 1.8) with north-verging and southverging thrusts on each side of the sandwiched Armorica block [START_REF] Matte | The Variscan collage and orogeny (480-290 Ma) and the tectonic denition of the Armorica microplate: a review[END_REF]. Large and coeval lateral displacements are also evidenced by crustal-scale strike-slip dextral shear zones [START_REF] Arthaud | Les décrochements tardi-hercyniens du Sud-Ouest de l'Europe. Géométrie et essai de reconstitution des conditions de la déformation[END_REF]1977;Kroner and Romer, 2013).

Since the 70's, the Variscan belt has been recognized as an ancient analogue of the Himalayan orogen [START_REF] Burg | Tectogénèse comparée de deux segments de chaîne de collision: Le Sud du Tibet (suture du Tsangpo); la chaîne hercynienne en Europe (sutures du Massif Central[END_REF][START_REF] Dewey | Tibetan, Variscan, and Precambrian basement reactivation: products of continental collision[END_REF][START_REF] Girardeau | Ophiolites et chaines de collision: exemples des chaines Himalaya-Tibet et Hercyniennes. Etude petro-structurale des ophiolites et de leurs encaissants: interpretations géodynamiques[END_REF][START_REF] Mattauer | Failles normales ductiles et grands chevauchements. Une nouvelle analogie entre l'Himalaya et la chaîne hercynienne du Massif Central français[END_REF][START_REF] Matte | Terrane boundaries in the Bohemian Massif: Result of large-scale Variscan shearing[END_REF][START_REF] Ménard | Collapse of a Hercynian Tibetan Plateau into a late Palaeozoic European Basin and Range province[END_REF] with the Variscan high-grade rocks being regarded as the eroded roots of an orogenic plateau, a structure not accessible for sampling in Tibet where it can only be probed through geophysical methods. This way, our knowledge on mountain belt dynamics clearly beneted from the inter-comparisons between both orogens (see Maierová et al., 2016 and references therein). Main subdivisions and terrain aliations Figure 1.9 depicts the inferred crustal origin of the blocks involved in the Variscan orogeny. Terrains exposed in the northern domain of the belt belonged to the Avalonia micro-continent [START_REF] Henderson | Gondwanan basement terranes of the VariscanAppalachian orogen: Baltican, Saharan and West African hafnium isotopic ngerprints in Avalonia, Iberia and the Armorican Terranes[END_REF][START_REF] Linnemann | The Cambrian to Devonian odyssey of the Brabant Massif within Avalonia: A review with new zircon ages, geochemistry, SmNd isotopes, stratigraphy and palaeogeography[END_REF]. Sandwiched between the GaliciaMassif Central and Rheic suture zones lies the Armorica micro-continent.

Both crustal blocks were originally part of the northern margin of Gondwana, from which they presumably got rifted apart in the CambrianOrdovician [START_REF] Ballèvre | Geochronology and geochemistry of Ordovician felsic volcanism in the Southern Armorican Massif (Variscan belt, France): Implications for the breakup of Gondwana[END_REF]Nance and Murphy, 1994;Nance et al., 2010) forming the so-called peri-Gondwana terranes. The southern domain is ascribed to be derived from the Gondwana mainland or other smaller peri-Gondwana terranes (Ballèvre et al., 2014). Importantly, as the constituents of the Variscan belt belonged to the northern margin of Gondwana, they would have been aected, at varied extent, by the Cadomian accretionary orogen (see Garfunkel, 2015 and references therein).

Within the crustal blocks, regional "zones" have been delineated based on both metamorphic grade and location with respect to the sutures [START_REF] Franke | Variscan plate tectonics in Central Europe -current ideas and open questions[END_REF]. For instance, the Moldanubian Zone of the Gondwana crustal block is regarded as an allochtonous unit as it features ophiolites and high-pressure metamorphic rocks (see Lardeaux et al., 2014 and references therein). The Armorica dispute

It must be stressed that many debates still surround the number of micro-continents and associated suture zones together with their respective locations [START_REF] Ballèvre | Palaeozoic history of the Armorican Massif: Models for the tectonic evolution of the suture zones[END_REF]2014;Faryad et al., 2013;[START_REF] Faryad | New evidence of blueschist facies rocks and their geotectonic implication for Variscan suture(s) in the Bohemian Massif[END_REF]Lardeaux et al., 2014;Linnemann et al., 2004;[START_REF] Martínez Catalán | Space and time in the tectonic evolution of the northwestern Iberian Massif: Implications for the Variscan belt[END_REF]2009;[START_REF] Schulmann | Anatomy of a diuse cryptic suture zone: An example from the Bohemian Massif, European Variscides[END_REF][START_REF] Sláma | How far did the Cadomian terranes travel from Gondwana during early Palaeozoic? A critical reappraisal based on detrital zircon geochronology[END_REF]. One of the most elusive aspect of the paleogeography and geodynamic evolution of the Variscan belt lies in the existence/absence of true GaliciaMassif Central oceanic domains (with a c. 4000 m deep oceanic oor). Indeed, palaeoclimatic and paleobiogeographical data argue against the existence of a wide oceanic domain and rather support a close connection between Armorica and Gondwana [START_REF] Paris | Early Palaeozoic palaeobiogeography of the Variscan regions[END_REF][START_REF] Robardet | The Armorica `microplate': fact or ction? Critical review of the concept and contradictory palaeobiogeographical data[END_REF]. Similarly, examination of the detrital zircon record of Cambrian to Devonian sediments indicate that the same sources were available throughout this period, inconsistent with opening of a true oceanic domain (Linnemann et al., 2004;[START_REF] Sláma | How far did the Cadomian terranes travel from Gondwana during early Palaeozoic? A critical reappraisal based on detrital zircon geochronology[END_REF]. Even though recent models for the evolution of the belt (e.g. Kroner and Romer, 2013) consider Armorica as the attenuated Gondwana continental margin (referred to as "Armorican Spur" therein), there is still no consensus on this topic.

The French Massif Central

The study area is part of the French Massif Central which best exposes the Moldanubian Zone of the Variscan belt, i.e. a crustal domain where both allochtonous and (para)authochonous units have been described. The rst historical map emphasizing the existence of metamorphic nappes is depicted Fig. 1.10 along with the regional names attributed to each geological region (Ledru et al., 1989). The main contours of this map remain valid almost 30 yrs after, for updated versions, the reader is referred to Chantraine et al. (1996) and Faure et al. (2009).

The nappe stack

The French Massif Central displays a dominantly south-verging stack of metamorphic nappes built up from the early Devonian to the early Carboniferous (Faure et al., 2009;Ledru et al., 1989) and composed of (see Fig. 1.10 for the regional denominations, Fig.

1.11 and Fig. 1.12):

amphibolite-to greenschist-facies upper allochthonous units (UAU), e.g. the Thiviers-Payzac, Leyme, Gartempe, Génis, Brévenne formations (Leloix et al., 1999;[START_REF] Duguet | PT paths reconstruction of a collisional event: The example of the Thiviers-Payzac Unit in the Variscan French Massif Central[END_REF];

the Upper Gneiss Unit (UGU) which comprises amphibolite-to granulite-facies ortho-and paragneisses [START_REF] Dufour | Granulite facies metamorphism and retrogressive evolution of the Monts du Lyonnais metabasites (Massif Central, France)[END_REF][START_REF] Forestier | Métamorphisme hercynien et antéhercynien dans le bassin du haut-Allier (Massif Central français)[END_REF][START_REF] Forestier | Découverte de niveaux d'amphibolites à pargasite, anorthite, corindon et saphirine dans les schistes cristallins de la vallée du Haut-Allier. Existence du faciès granulite dans le Massif Central Français[END_REF]Gardien et al., 1990; Figure 1.9: Simplied map of the Variscan belt of Europe, are depicted the main lithotectonic subdivisions (after [START_REF] Franke | Variscan plate tectonics in Central Europe -current ideas and open questions[END_REF], the location of suture zones and origin of the crustal blocks (after Ballèvre et al., 2014 and[START_REF] Henderson | Gondwanan basement terranes of the VariscanAppalachian orogen: Baltican, Saharan and West African hafnium isotopic ngerprints in Avalonia, Iberia and the Armorican Terranes[END_REF]. Abbreviations: O.-M.Z.: Ossa-Morena Zone; S.P.Z.: South-Portuguese Zone; GMC: GaliciaMassif Central suture. Adapted from Ballèvre et al. (2014). [START_REF] Lardeaux | Granulites à kornérupine et décompression postorogénique des Monts du Lyonnais (M.C.F.)[END_REF]2001;Schulz, 2014) and typically shows at its base a bimodal meta-igneous association referred to as Leptynite-Amphibolite Complex or LAC [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF][START_REF] Downes | Isotope and traceelement heterogeneities in high-grade basic metamorphic rocks of Marvejols: Tectonic implications for the Hercynian suture zone of the French Massif Central[END_REF][START_REF] Forestier | Métamorphisme hercynien et antéhercynien dans le bassin du haut-Allier (Massif Central français)[END_REF][START_REF] Giraud | Geochemistry of leptyno-amphibolite complex from Haut-Allier (French Massif Central)[END_REF][START_REF] Santallier | Les complexes leptyno-amphioliques (C.L.A.) : revue critique et suggestions pour un meilleur emploi de ce terme[END_REF] that contains relicts of eclogite-facies metamorphism [START_REF] Bellot | Episodic exhumation of HP rocks inferred from structural data and P-T paths from the southwestern Massif Central (Variscan belt, France)[END_REF]Berger et al., 2010a;b;[START_REF] Bouchardon | Evaluation des conditions de Pression-Température du "top" métamorphique des éclogites du Lévézou (Rouergue, Massif Central français)[END_REF]1989;[START_REF] Delor | Découverte d'éclogites à glaucophane dans la klippe de Najac (Massif Central, France) : nouveaux témoins océaniques d'un stade haute pression dans la chaîne de collision varisque[END_REF]1987;[START_REF] Gardien | Découverte d'éclogites dans la synforme de Maclas : extension de l'unité supérieure des gneiss à l'Est du Massif Central[END_REF]Gardien, 1993;[START_REF] Godard | Découverte d'éclogites, de péridotites à spinelle et d'amphibolites à anorthite, spinelle et corindon dans le Morvan[END_REF]Lardeaux et al., 2001;[START_REF] Lasnier | Découverte de roches éclogitiques dans le groupe leptyno-amphibolique des monts du Lyonnais (Massif central français)[END_REF][START_REF] Mercier | Découverte d'éclogites dans l'Artense (M.C.F.) Implications pour la dénition des nappes à l'Est du Sillon Houiller[END_REF];

the Lower Gneiss Unit (LGU), an assemblage of amphibolite-facies micaschists, ortho-and paragneisses together with scarce amphibolites (Briand et al., 1992;Ledru et al., 2001); the lower-grade Parautochthonous Unit (PAU) made up largely of greenschist-to amphibolite-facies metasediments, e.g. the Cévennes schists and the Montagne Noire northern ank [START_REF] Burg | Inverted metamorphic zonation and Variscan thrust tectonics in the Rouergue area (Massif Central, France): P-T-t record from mineral to regional scale[END_REF][START_REF] Duguet | Successive shearing tectonics during the Hercynian collisional evolution of the southwestern French Massif Central[END_REF][START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF];

a Fold-and-Thrust Belt of very low metamorphic grade, e.g. the Montagne Noire southern ank and the Vigan schists (Alabouvette et al., 1988;[START_REF] Doublier | Age and grade of metamorphism in the eastern Monts de Lacaune Implications for the collisional accretion in Variscan externides (French Massif Central)[END_REF]2015;Guérangé-Lozes and Burg, 1990;[START_REF] Wiederer | Low-grade metamorphism in the Montagne Noire (S-France): Conodont Alteration Index (CAI) in Palaeozoic carbonates and implications for the exhumation of a hot metamorphic core complex[END_REF] The relationships between each unit may dier from a domain to another (Fig. 1.12).

Tectonicmetamorphicmagmatic evolution

The evolution of the FMC has been deciphered through the examination of the tectonic relationships between the dierent nappes and their PT conditions attained at peak Figure 1.10: Geographic location of the main geological regions and sketch map of the main nappes in the French Massif Central. Figure and caption taken (and adapted) from Ledru et al. (1989). 1: Visean sediments; 2: undierentiated granite bodies; 3: epizonal upper units (a) Thiviers-Payzac and Génis, (b) Brévenne; 4: Upper Gneiss Unit; 5: Lower Gneiss Unit; 6: Parautochtonous Unit; 7: Fold-and-Thrust-Belt; 8: thrusts (370390 Ma); 9: thrusts and transcurrent shear zones (360340 Ma); 10: thrusts and transcurrent shear zones (340320 Ma).

Figure 1.11: Summary of main metamorphic (after Montel et al., 1992) and deformation phases (after Faure et al., 2009) recognized in the French Massif Central. Further descriptions of the inverted Barrowian sequence can be found in [START_REF] Burg | Inverted metamorphic zonation and large scale thrusting in the Variscan belt: An example in the French Massif central[END_REF]1989) and [START_REF] Schulz | Zoned garnets in metapelites and P-T-deformation path interpretation of the Variscan inverted metamorphic sequence of Haut-Allier, French Massif Central[END_REF]2001); [START_REF] Schulz | EMP-monazite age controls on P-T paths of garnet metapelites in the Variscan inverted metamorphic sequence of La Sioule, French Massif Central[END_REF]. Figure courtesy of J.-F. Moyen. metamorphism. Six main deformational phases have been retained (see [START_REF] Faure | L'évolution polycyclique de la chaîne hercynienne[END_REF]2009 and references therein):

an early stage D 0 of oceanic and continental subduction took place at 420400 Ma, presumably related to the closure of the GaliciaMassif Central Ocean and recorded by the eclogites of the LeptyniteAmphibolite Complex.

exhumation of the HP rocks was associated with top-to-the S D 1 thrusting of the Upper Gneiss Unit over the Lower Gneiss Unit (and Parautochtonous Unit in the Limousin and Sioule areas), developing an inverted Barrowian metamorphic sequence (Fig. 1.11). Deformation and MPM(H)T metamorphism have been dated between 380360 Ma. Following Montel et al. (1992), HP metamorphism and subsequent decompression-related anatexis experienced by the Upper Gneiss Unit during D 0 and D 1 are termed "M1" (see Fig. 1.11). The earliest dramatic magmatic event observed in the Massif Central correspond to the c. 360 Ma "Tonalite Belt" (Fig. 1.11) featuring gabbro-tonalite-granodiorite, amphibole-bearing calc-alkaline plutons [START_REF] Bernard-Griths | The tonalite belt of Limousin (French Central Massif ) : U-Pb zircon ages and tectonic implications[END_REF][START_REF] Peier | Données nouvelles sur la ligne tonalitique du Limousin et les "diorites quartziques" qui la composent[END_REF][START_REF] Shaw | The quartz-diorites of Limousin: Elemental and isotopic evidence for Devono-Carboniferous subduction in the Hercynian belt of the French Massif Central[END_REF]. Coeval volcanics are observed in the Brévenne (Pin and Paquette, 1997;2002) and Somme formations [START_REF] Delfour | Données lithostratigraphiques et géochimiques sur le Dévono-Dinantien de la partie sud du faisceau du Morvan (nord-est du Massif central français)[END_REF].

a pervasive top-to-the NW D 2 deformation reworked the early nappe stack and transported the Upper Allochtonous Units and in some cases the Parautochtonous Unit above the Upper Gneiss Unit, still under MPMT metamorphic conditions (Fig. 1.12 and 1.11). D 2 would have occurred at 360345 Ma.

D 3 is a dual event typied by syn-orogenic crustal extension and acid volcanism in the northern FMC [START_REF] Binon | A Rb-Sr and U-Pb isotopic study of two granite massifs from Montagne bourbonnaise (NE Massif central, France)[END_REF]) meanwhile top-to-the S thrusts developed to the South in the Parautochtonous Units. D 3 has been dated at 345325 Ma and marks the onset of voluminous granitic magmatism in the Massif Central (with granites representing more than a third of the today-exposed lithologies). D 4 and D 5 events are characterized by general extension and localized transpres- sion coeval to LPHT metamorphism ("M3" of Montel et al., 1992) and granite intrusions. Activation of strike-slip to normal shear zones controlled the exhumation of migmatite domes (Montagne Noire, Velay) representing extruded portions of partially molten middle crust (Ledru et al., 2001;[START_REF] Whitney | Syn-collapse eclogite metamorphism and exhumation of deep crust in a migmatite dome: The PTt record of the youngest Variscan eclogite (Montagne Noire, French Massif Central)[END_REF]. The evolution of the Velay dome is typied by isobaric heating corresponding to the low-pressure granulite-facies "M4" metamorphic event (Fig. 1.11).

Geodynamic interpretations

According to Faure et al. (2009), the D 0 and D 1 events would reect the closure of the GaliciaMassif Central ocean and docking of the Armorica micro-continent to the Gondwana mainland, generating major top-to-the S thrusts. Such interpretation is supported by the existence of an ophiolitic association in the Limousin area [START_REF] Dubuisson | Evidence for a lost ocean in Variscan terranes of the western Massif Central, France[END_REF] and (U)HP metabasic eclogites throughout the Massif Central (Berger et al., 2010a;b;Lardeaux et al., 2001;[START_REF] Matte | The Variscan collage and orogeny (480-290 Ma) and the tectonic denition of the Armorica microplate: a review[END_REF][START_REF] Mercier | Découverte d'éclogites dans l'Artense (M.C.F.) Implications pour la dénition des nappes à l'Est du Sillon Houiller[END_REF]Paquette et al., 1995). Yet, Silurian magmatic rocks that would testify for the existence of a subduction arc are lacking and the absence of Silurian zircon grains in the detrital record of the Devonian to Permian sediments suggests a period of magmatic quiescence [START_REF] Lin | Detrital zircon age distribution from Devonian and Carboniferous sandstone in the Southern Variscan Fold-and-Thrust belt (Montagne Noire, French Massif Central), and their bearings on the Variscan belt evolution[END_REF][START_REF] Pfeifer | Permian exhumation of the Montagne Noire core complex recorded in the Graissessac-Lodève Basin[END_REF]. Consequently, at our present state of knowledge, the signicance of D 0 and D 1 remains elusive.

The D 2 top-to-the NW shearing event is attributed to the collision between Laurentia BalticaAvalonia (forming Laurussia) to the North and GondwanaArmorica to the South, in line with the closure of the Rheic ocean (Faure et al., 2009;2017). The "Tonalite Belt" and calc-alkaline volcanics in the Morvan would represent the remnants of a magmatic arc developed on GondwanaArmorica in response to the south-directed subduction of the Rheic ocean (Faure et al., 2009;Lardeaux et al., 2014). A back-arc setting is preferred for the coeval bimodal volcanics of the Brévenne formation (Pin and Paquette, 1997;2002).

D 3 coeval extension and compression in the northern and southern FMC, respectively, may be attributed to the growth and southwards lateral expansion of an orogenic plateau (Vanderhaeghe, Gardien, Moyen, Gébelin, Laurent, Couzinié, Chelle-Michou, and Villaros, Vanderhaeghe et al.) which existence is besides supported by paleontological and sedimentological data [START_REF] Becq-Giraudon | Hercynian high-altitude phenomena in the French Massif Central: tectonic implications[END_REF]. D 4 and D 5 events would correspond to syn-to post-orogenic collapse of the belt in line with general extension and widespread magmatism (Burg et al., 1994). 1.5 Some analytical considerations 1.5.1 Error estimation associated with UPb dating

An adequate estimation of the error associated to an UPb age is critical to correctly address its geological signicance. Errors are of two types. First, the internal error accounts for the intrinsic dispersion of the measured value during the analytical run.

It is solely based on counting statistics and often corresponds to a standard error, i.e.

the standard deviation of the measured value divided by the square root of the number of measurements. Such internal errors aect each individual analysis and monitor the precision of each of those.

Second, systematic errors refer to the uncertainties in a set of external parameters considered in the UPb data processing that may generate a bias in the results [START_REF] Paton | Improved laser ablation U-Pb zircon geochronology through robust downhole fractionation correction[END_REF]. Those are indicators of the accuracy of the analyses. They notably include the uncertainties on [START_REF] Gehrels | Enhanced precision, accuracy, eciency, and spatial resolution of U-Pb ages by laser ablation-multicollector-inductively coupled plasma-mass spectrometry[END_REF]: (i) the decay constants for 238 U and 235 U; (ii) the isotope ratios of the primary standard (GJ1 in all the analytical sessions conducted in this thesis); (iii) the overall validity of the applied corrections (notably the monitoring of the downhole U/Pb fractionation).

The uncertainties on the decay constants are 0.107% and 0.136% for 238 U and 235 U, respectively [START_REF] Jaey | Precision measurement of half-lives and specic activities of 235 U and 238[END_REF]. Uncertainties on GJ1 were set at 0.5% in the following.

The average uncertainty of the corrections was estimated based on the obtained isotope ratios/ages for the secondary standards. For each of those, the average age obtained in the course of our analyses departs from the recommended IDTIMS value by less than 1% (< 0.6% for BB-16).

Systematic errors must be propagated to any UPb date calculation based on several individual analyses (Concordia date, weighted average date, Concordia intercept), yielding an estimate of both precision and accuracy and allowing to compare dates obtained during dierent analytical sessions. Error propagation has been conducted by quadratic addition of the internal error and the systematic errors listed above.

The add-on Isoplot/Ex v. [START_REF] Magni | Delamination versus break-off: the fate of continental collision[END_REF].15 (Ludwig, 2008) for MS Excel ® calculates an uncer- tainty on dates based solely on the individual errors of the measurements, accordingly retained as an estimate of the internal error. The uncertainties on the decay constants can also be propagated automatically by Isoplot, which has been done in this work. Consequently, the internal error displayed in the Wetherill and Tera-Wasserburg diagrams does actually encompass a systematic error component. To calculate a Variscan date, the uncertainty on the corrections was estimated based on Ple²ovice (1% uncertainty). For

Cadomian dates, the uncertainty on BB-16 was considered (0.6 %). Resulting systematic errors range between 0.8 and 1.12 %. Such systematic error propagation has not been conducted in the published articles (sections 2.1 and 6.3) but is followed in unpublished data.

Inter-comparison of data from dierent laboratories

The data presented in this thesis have been obtained in the course of several analytical sessions, in dierent laboratories using specic equipment (e.g. sector-eld vs. quadrupole ICPMS) and contrasted data processing schemes. For instance, UPb data acquired in Frankfürt-am-Main (GUF) and Stellenbosch (SUN) were processed using an in-house

Excel spreadsheet (Gerdes and Zeh, 2006). In contrast, data reduction in Rennes relies on GLITTER ® (Van Achterbergh et al., 2001). Finally, data obtained at ETH Zurich were processed with the Igor Pro Iolite v2.5 software [START_REF] Hellstrom | Iolite: Software for spatially resolved LA-(quad and MC) ICP-MS analysis[END_REF], using the VizualAge data reduction scheme [START_REF] Petrus | VizualAge: A novel approach to laser ablation ICP-MS U-Pb geochronology data reduction[END_REF]. A similar situation is encountered for LuHf analyses, between GUF and Clermont-Ferrand (with specic in-house spreadsheets). Despite the dierent specications and data reduction procedures, the accuracy of each generated dataset can be monitored by examining the results obtained on secondary reference materials (Fig. 1.13 and 1.14).

Figure 1.13: UPb Concordia ages obtained for secondary reference materials in the course of each analytical session. Plotted uncertainties are the quadratic additions of internal (at 2σ or 95% condence, in which case the symbol is shaded) and systematic errors. The purple bars depict the IDTIMS ages and associated errors for Ple²ovice (Sláma et al., 2008a), Temora [START_REF] Black | TEMORA 1: a new zircon standard for phanerozoic UPb geochronology[END_REF]2004), BB-16 (Santos et al., in press) and 91500 [START_REF] Wiedenbeck | Three natural zircon standards for U-Th-Pb, Lu-Hf, trace element and REE analyses[END_REF]2004). Note the age scale breaks.

UPb data First, all but one analyses yielded UPb ages identical within error to the IDTIMS value ± 1%. In each analytical session, at least one secondary standard shows the expected UPb age, within uncertainties. Consequently, the 9 datasets are considered as equivalent and inter-comparable. During the 2016 sessions conducted at GUF, two statistically dierent Concordia dates were calculated from the measurements conducted on the Ple²ovice reference material, at c. 335 and 344 Ma. Standard BB-16 analysed in the same sessions yielded reproducible and accurate results meaning that the two Ple²ovice dates are unlikely to be analytical artefacts. This may suggest the presence of older domains in the Ple²ovice grains but has not been investigated further.

Figure 1.14: 176 Hf/ 177 Hf ratios obtained for secondary reference materials in the course of each analytical session. The grey bands depict the reference values for Ple²ovice (Sláma et al., 2008a), 91500 [START_REF] Blichert-Toft | The Hf isotopic composition of zircon reference material 91500[END_REF], Temora (Woodhead et al., 2004), Mud Tank [START_REF] Woodhead | A preliminary appraisal of seven natural zircon reference materials for in situ Hf isotope determination[END_REF], BB-16 (Santos et al., in press) and GJ-1 (Morel et al., 2008).

LuHf data Measurements performed on secondary standards at GUF yielded identical results throughout both sessions. Analyses from Clermont-Ferrand (LMV) are less consistent as periodic oscillations in the measured ratios can be observed during the run. Such dispersion has been taken into account while processing the sample data by propagating the reproducibility of GJ-1, the least reproducible reference material, to the internal errors of each individual measurement. At rst glance, the GUF data would seem more accurate but this is due to the instrumental oset correction developed at GUF but not at LMV. Overall, the observed oset would result in an overestimation of the ε Hf (t) by 0.7 to 1.3 ε-unit, depending on the reference material considered. I believe that this oset will not alter the validity of the reasoning developed in this thesis because: (i) the associated error is of the same order of magnitude than the analytical uncertainties for individual measurements; and (ii) analyses have been performed on a large number of detrital zircon grains with the aim to draw general conclusions on the origin and nature of the detritus, insensitive to such limited oset.

This manuscript is divided in three main parts.

Part I focuses on the pre-Variscan evolution of the French Massif Central. Chapter 2 and 3 present comprehensive petrogenetic studies of the constituent rocks from the Lower and Upper Gneiss Units, respectively. Chapter 4 is a review of the pre-Variscan magmatic record in the French Massif Central with a particular emphasis on the disputed CambrianOrdovician geodynamic scenario.

Part II is a characterization of the timing, source and structural framework of Variscan post-collisional magmatism in the Massif Central. Chapter 5 describes the diversity of post-collisional magmas and provides chronological and petrological constraints. Chapter 6 is a structural and geochronological study conducted on a migmatite dome.

Part III has been written as a general discussion. Chapter 7 addresses the formation and dierentiation of the continental crust in the French Massif Central seen through the prism of the zircon record.

Part I

Pre-Variscan evolution of the eastern French Massif Central

Introduction

Accretionary orogens develop along oceanic and continental active margins, feature volumetrically abundant mantle-derived magmatism and are accordingly considered as the main locus of continental crust production (Cawood et al., 2009;Jagoutz and Kelemen, 2015;[START_REF] Reymer | Phanerozoic addition rates to the continental crust and crustal growth[END_REF]Taylor and McLennan, 1985). Conversely, collisional orogens juxtapose stable portions of continental lithospheric blocks and are rather seen as domains of extensive crust reworking through partial melting of pre-existing crustal rocks [START_REF] Dewey | Shortening of continental lithosphere: the neotectonics of Eastern Anatoliaa young collision zone[END_REF]Harris Lithos 286-287 (2017) 16-34 et al., 1986;Hawkesworth et al., 2009Hawkesworth et al., , 2010)). However, recent studies have refined and nuanced these end-member scenarios by pointing out that new crust may also be produced at the end of continental collision (Couzinié et al., 2016;Moyen et al., 2017;Niu et al., 2013) and likewise, that crust reworking also takes place in arc systems (Collins and Richards, 2008;Zurbriggen, 2015). Therefore, assessing the relative importance of each phenomenon in both geodynamic settings is paramount to understand the modes of continental crust formation and evolution through time.

Terranes formerly belonging to the northern Gondwana margin (Fig. 1, see review in Stampfli et al., 2013) are ideal targets to address this issue because they have sequentially been affected by: (i) the Cadomian Western Pacific-type marginal orogenic system, of Cryogenian-Ediacaran age (Chelle-Michou et al., 2017;Garfunkel, 2015;Linnemann et al., 2014;Nance et al., 1991); followed by, (ii) the Variscan orogeny, a major late Paleozoic continental collision episode resulting from the convergence between Laurussia and Gondwana (Kroner and Romer, 2013;Matte, 1986) and culminating with the assembly of Pangea, the latest supercontinent of Earth's history (Rogers and Santosh, 2003).

The French Massif Central (FMC) shows one of the largest exposures of the inner part of the Variscan orogen (Lardeaux et al., 2014) and isotopic evidence from the voluminous Variscan crust-derived granitoids demonstrate that such magmatism extensively reworked a continental crust of Neoproterozoic to early Paleozoic ancestry (Melleton et al., 2010;Moyen et al., 2017;Pin and Duthou, 1990;Turpin et al., 1990). However, the nature of this pre-Variscan crust as well as the geodynamic setting in which it formed is still a matter of debate. For instance, it remains unclear to what extent the crust segment today exposed in the FMC was impacted by the Cadomian orogeny (see discussion in Garfunkel (2015)). From this perspective, a better knowledge of the age, structure, lithological composition and configuration of the pre-Variscan crust in the FMC would: (i) provide new constraints on the late Ediacaran/early Paleozoic paleogeography and geodynamics of the northern Gondwana margin; (ii) improve our understanding of the rate and timing of crustal growth in Western Europe.

In the eastern part of the FMC, the Variscan nappes feature high-grade gneisses and, in particular, large amounts of meta-igneous rocks, which have likely witnessed one or several pre-Variscan magmatic episodes. Somewhat outdated radiometric dating from these orthogneisses (Caen-Vachette, 1979;[START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF] as well as detrital and inherited zircon data from metasedimentary rocks (Chelle-Michou et al., 2017) and Variscan granitoids (Laurent et al., 2017) respectively, suggest that they emplaced close to the Proterozoic-Paleozoic boundary at ca. 545 Ma. Yet, these meta-igneous rocks lack modern and/or direct geochronological data, in contrast to the western FMC where such work has been undertaken (Alexandre, 2007;Alexandrov et al., 2001;Melleton et al., 2010). Similarly, the nature, petrogenesis and geodynamic Fig. 1. Sketch map of the crustal blocks involved in the Variscan orogeny, adapted from Ballèvre et al. (2014). Yellow star highlights the location of the study area. Oceanic sutures: GMC, Galicia-Massif-Central Ocean. Regional subdivisions: NAM, North Armorican Massif; L, Limousin (Western Massif Central); EMC, Eastern Massif Central. Shear zones: SH, Sillon Houiller (coal line). significance of the FMC orthogneisses are poorly constrained. The aim of this contribution is therefore to decipher the age and origin of the pre-Variscan orthogneiss units in the Velay area using field observations, whole-rock geochemistry, LA-ICP-MS zircon U-Pb dating and LA-MC-ICP-MS zircon Lu-Hf isotope measurements. This new dataset demonstrates that the pre-orogenic evolution of this part of the FMC is dominated by late Ediacaran events and features the emplacement at shallow crustal levels of a large (~1800 km 2 ) S-type granite batholith, most likely formed by melting of an Ediacaran back-arc supracrustal sequence at the end of the Cadomian orogeny. This pinpoints the importance of crust reworking in accretionary orogens, even in domains lacking significant volumes of ancient basement.

Geological setting

The French Massif Central and its pre-Variscan evolution

The French Massif Central displays a south-verging stack of metamorphic nappes built up from the early Devonian to the early Carboniferous and composed from top to bottom of (Faure et al., 2009b, Ledru et al., 1989, and references therein): (i) amphibolite-to greenschistfacies upper allochthonous units (UAU: Thiviers-Payzac, Leyme, Gartempe, S t -Sernin-sur-Rance, Génis, Brévenne); (ii) the Upper Gneiss Unit (UGU) which comprises amphibolite-to granulite-facies orthoand paragneisses and typically shows at its base a bimodal metaigneous association ("Leptynite-Amphibolite Complex" or LAC) that contains relicts of eclogite-facies metamorphism; (iii) the Lower Gneiss Unit (LGU), an assemblage of amphibolite-facies micaschists, ortho-and paragneisses together with scarce amphibolites; (iv) the lower-grade Parautochthonous Unit (PAU) made up largely of greenschist-to amphibolite-facies meta-sediments (e.g. Cévennes schists); and (v) a Fold-and-Thrust Belt of very low metamorphic grade (Montagne Noire nappes, Vigan schists). The Variscan tectonic-metamorphic evolution encompasses (Burg et al., 1994;Faure et al., 2009b): (i) an early (late Silurian to early Devonian) event corresponding to the closure of several oceanic domains and coeval HP metamorphism; (ii) late Devonian nappe stacking and crustal thickening ending up in the growth and lateral flow of an orogenic plateau during the early Carboniferous; (iii) gravitational collapse via the activation of low-angle detachment faults marked by the development of migmatite domes in the late Carboniferous.

The pre-Variscan sedimentary materials that build up the low-grade nappes (UAU, PAU and Fold-and-Thrust Belt) are mostly late Ediacaran to early Ordovician in age as shown by paleontological data (Fournier-Vinas and Debat, 1970;Guérangé-Lozes and Burg, 1990;[START_REF] Reitz | Upper Proterozoic microfossils in low-grade phyllites of the Brévenne-unit, NE Massif Central (France)[END_REF] and dating of interlayered volcanics (Faure et al., 2009a;Lescuyer and Cocherie, 1992). In higher-grade, gneissic units (UGU and LGU), detrital zircon studies (Chelle-Michou et al., 2017;Melleton et al., 2010) together with field relationships between meta-sediments and adjacent dated orthogneisses suggest maximum depositional ages ranging from the early Ediacaran to the Cambrian (Ledru et al., 1994;Melleton et al., 2010). The conspicuous presence of volcanic rocks (meta-tuffs, meta-lavas) throughout the stratigraphic pile exposed in low-grade units [START_REF] Alvaro | Stratigraphic review of the Cambrian-Lower Ordovician volcano-sedimentary complexes from the northern Montagne Noire[END_REF]Marini, 1987;[START_REF] Pouclet | Cambrian-early Ordovician volcanism across the South Armorican and Occitan domains of the Variscan Belt in France: continental break-up and rifting of the northern Gondwana margin[END_REF] and the existence of several orthogneiss massifs of similar ages within the high-grade domains (Alexandre, 2007;Duthou et al., 1984;Melleton et al., 2010;Roger et al., 2015) testify for a protracted magmatic activity from the late Ediacaran to the late Ordovician. Petrogenetic studies attest to the tapping of two contrasting reservoirs throughout this period: (i) the asthenospheric/lithospheric mantle, source of the metabasites from the low-grade units and the LAC (Briand et al., 1992;Marini, 1987;Pin and Marini, 1993;[START_REF] Pouclet | Cambrian-early Ordovician volcanism across the South Armorican and Occitan domains of the Variscan Belt in France: continental break-up and rifting of the northern Gondwana margin[END_REF]; (ii) preexisting crustal lithologies (Alexandre, 2007;Melleton et al., 2010) as a source of felsic magmas. Coeval sedimentation, crust-and mantle-derived magmatism have been attributed to long-lived continental extension ending up in the formation of a hyperextended margin during the Ordovician (Lardeaux et al., 2014). Collectively, these data suggest that the pre-Variscan crust of the FMC is not older than Neoproterozoic in age (Chelle-Michou et al., 2017).

The Velay dome

In the eastern Massif Central, the Variscan nappe stack (and notably the LGU; Fig. 3) is reworked by the formation of a 120 × 80 km granitemigmatite complex, referred to as the Velay dome. It corresponds to partially molten middle crust which exhumation was controlled on its northern edge by the Pilat low-angle detachment shear zone, typically showing top-to-the-NE sense of shear dated at 313 ± 6 Ma by 39 Ar/ 40 Ar on syntectonic biotite (Gardien et al., 1997;Malavielle et al., 1990). On its southern edge, the dome is overturned to the south (Lagarde and Dallain, 1994) onto the PAU, from which it is separated by a top-to-the south normal shear zone dated at 310 ± 5 Ma (Bouilhol et al., 2006). The Velay Dome consists of several lithologies including (Fig. 1): (i) ortho-and paragneisses ranging from unmolten to diatexitic (Montel et al., 1992) together with very scarce amphibolites (Briand et al., 1992); (ii) a set of peraluminous granitoids comprising early laccoliths (Ledru et al., 2001) and the heterogeneous biotitecordierite-bearing "Velay" granite (Williamson et al., 1992). The migmatites and associated granites result from several successive melting events (Montel et al., 1992) over a period of 35 Ma, from c. 335 to 300 Ma (Couzinié et al., 2014;Laurent et al., 2017).

Here we define the Velay Orthogneiss Formation (VOF) as a consistent lithological unit gathering all pre-Variscan meta-igneous felsic rocks that crop out in the dome. The VOF can be divided into three main geographic sub-domains (Fig. 2): (i) the Pilat orthogneisses, exposed along the northeastern part of the dome; (ii) the Vivarais area, where meta-igneous rocks and paragneisses represent the weakly molten roof of the dome (Lagarde and Dallain, 1994); (iii) the "Arc-de-Fix" orthogneisses (R'Kha [START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF], which form a crescent outlining the western and southern parts of the dome. Collectively, the VOF covers an exposed area of ~1800 km 2 . Field observations show that the VOF is intrusive within the adjacent paragneisses (Ledru et al., 1994, Fig. 3).

Typical lithologies of the VOF are (based on our field survey and unpublished French PhD theses from the 70s-80s, referenced in Supplementary text): (i) a volumetrically dominant biotite ± muscovite ± sillimanite augen gneiss (Fig. 4a) featuring pluricentimetric K-feldspar porphyroblasts and accessory garnet, allanite, ilmenite, apatite and zircon; (ii) a muscovite ± biotite ± garnet fine-grained leucogneiss (locally called "leptynite") with similar accessory minerals; (iii) a volumetrically subordinate biotite ± cordierite/garnet medium-grained banded orthogneiss. The leucogneisses occasionally occur as plurimetric enclaves or boudins within the augen gneiss (Fig. 4b), but most often form concordant bodies embedded within it (Fig. 4c,d). The contact between both lithologies can be sharp and locally underlined by a thin biotite selvage (Fig. 4c), or gradational, in which case leucogneisses appear as counterparts of the augen gneisses lacking biotite and Kfeldspar porphyroclasts. All rock types are deformed by the Variscan tectonics, especially the augen gneiss that shows a well-developed foliation locally up to mylonitic grade (Fig. 4d), and locally display evidence for partial melting such as disruption of the foliation associated with segregation of leucosomes (especially close to the margins and at the roof of the Velay dome). The Vivarais gneisses tend to be more migmatitic (metatexite to diatexite) than the Arc-de-Fix (typically unmolten to metatexitic).

Studies on the VOF have concluded that augen gneisses in the Arc de Fix, Vivarais and Pilat domains correspond to former porphyritic granitoids (Ledru et al., 2001). Previous geochronological investigations suggest that those granitoids were emplaced in the early Cambrian as the Arc-de-Fix gneisses yielded a zircon Pb evaporation age of 533 ± 23 Ma (Mougeot et al., 1997) and a whole-rock Rb-Sr age of 528 ± 9 Ma (R'Kha [START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF]. EPMA dating of inherited monazites in a migmatitic augen gneiss yielded similar results (543 ± 25 Ma; Be Mezeme et al. (2006)). The origin and age of leucogneisses are still disputed. In the Arc-de-Fix domain, they are thought to be part of the same magmatic suite of the augen gneiss protolith and would thus correspond to early Cambrian meta-leucogranites (R'Kha [START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF]. In the Vivarais area, Chenevoy et al. (1986) also proposed a leucogranite protolith. In the Pilat domains, leucogneisses are rather regarded as former rhyolites or rhyolitic tuffs of late Ediacaran age (545 ± 14 Ma;Caen-Vachette (1979)). Geological map of the Velay dome area. The extent of Variscan partial melting of the metamorphic lithologies is not shown for sake of clarity. Redrawn after Ledru et al. (2001) and regional geological maps of France at scale 1/50000. Literature geochronological data: 1, 528 ± 9 Ma, Rb-Sr whole-rock (R'Kha [START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF]; 2, 543 ± 25 Ma, U-Th-Pb monazite (Be Mezeme et al., 2006); 3, 533 ± 23 Ma, zircon Pb evaporation (Mougeot et al., 1997);4, 545 ± 14 Ma, Rb-Sr whole-rock (Caen-Vachette, 1979).

Materials and methods

Whole-rock geochemistry

We collected 35 samples of unmolten augen gneisses, banded gneisses and leucogneisses from the three domains mentioned above. Location, GPS coordinates and description of investigated samples are presented Table S1. Whole-rock major and trace element contents were obtained from the ALS Global firm (details on the procedure and accuracy/reproducibility in Supplementary text). A database of VOF samples was compiled using this new dataset and analyses from the literature (see Table S2), carefully filtering out: (i) migmatitic samples, based on petrographic descriptions; and (ii) samples that experienced alteration and/or LILE (Large Ion Lithophile Elements) mobility during Variscan metamorphism, by calculating the weathering index (W) of Ohta and Arai (2007) and considering a cut-off value of W = 30% (see Supplementary text and Fig. S1). A total of 270 major element analyses were retained accordingly (including the newly obtained data). We will further consider that the retained VOF samples experienced nearly closed-system metamorphism during the Variscan orogeny, such that their chemical compositions reflect those of their igneous protoliths. This assumption is supported by (i) their position close to, or overlapping with the "igneous trend" in the MFW diagram of Ohta and Arai (2007), suggesting limited element mobility (Fig. S1); and (ii) the fact that 22 samples from the VOF analyzed for Rb-Sr isotopes (Caen-Vachette, 1979, and[START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF]) define a whole-rock isochron clearly yielding a pre-Variscan (Cambrian) date (see Supplementary text and Fig. S2), specifically identical (within uncertainties) to our zircon U-Pb dating results (see Section 4.2).

U-Pb geochronology

We selected four samples from the VOF for U-Pb dating, to constrain the age(s) of the igneous protolith(s). In this perspective, we focused the sampling in the Arc de Fix domain (Fig. 2) that is the least affected by the Variscan anatexis. Dated samples correspond to two augen gneisses (MM06 and MM11) and two leucogneisses (MM09 and MM10) representative of the main facies observed in the VOF. Their textures range from granoblastic to grano-lepidoblastic and porphyroclastic (for the augen gneisses, see Fig. 4a andc). Mineralogical assemblages are described Table 1 and representative annotated thin section photomicrographs can be found in the Supplementary text (Fig. S3). Rock samples were crushed using standard procedures (jaw crusher, ring mill) and sieved to b 500 μm. Zircons were concentrated using conventional techniques (panning, heavy liquids, magnetic separation) and hand-picked under a binocular microscope. Selected grains were subsequently cast in epoxy resin and polished to expose their interiors. The internal structures were characterized by back-scattered electron (BSE) and cathodoluminescence (CL) imaging using (i) a Jeol JSM-6400 SEM at the Ecole des Mines de St-Etienne for BSE and (ii) a Jeol JSM-5910 SEM at the Laboratoire Magmas et Volcans (Clermont-Ferrand) for CL.

Leptynite

U-Pb geochronology was conducted by in-situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) at Géosciences Rennes using a ESI NWR193UC Excimer laser coupled to a quadrupole Agilent 7700x ICP-MS equipped with a dual pumping system to enhance sensitivity. The instrumental conditions are reported in Table S3.

The ablated material was carried into helium, and then admixed with nitrogen (Paquette et al., 2014) and argon, before injection into the plasma source. The alignment of the instrument and mass calibration was performed before each analytical session using the NIST SRM 612 reference glass, by inspecting the 238 U signal and by minimizing the ThO + /Th + ratio (b0.5%). During the course of an analysis, the signals of 204 (Pb + Hg), 206 Pb, 207 Pb, 208 Pb and 238 U masses are acquired. The occurrence of common Pb in the sample can be monitored by the evolution of the 204 (Pb + Hg) signal intensity, but no common Pb correction was applied owing to the large isobaric interference with Hg. The 235 U signal is calculated from 238 U on the basis of the ratio 238 U/ 235 U = 137.88. Single analyses consisted of 20s of background integration followed by 60s integration with the laser firing and then a 10 s wash-out delay. Ablation spot diameters of 20-35 μm with repetition rates of 3 Hz were used depending on the grain size. Data were corrected for U-Pb and Th-Pb fractionation and for mass bias by standard bracketing with repeated measurements of the GJ-1 zircon standard (Jackson et al., 2004). Along with the unknowns, the zircon standard Plešovice (337.13 ± 0.37 Ma, Sláma et al. (2008)) was measured to monitor accuracy of the analyses and produced a Concordia age of 337.0 ± 1.8 Ma (N = 20, MSWD C + E = 0.21). Data reduction was carried out with the GLITTER® software package developed by the Macquarie Research Ltd. (Van Achterbergh et al., 2001). Concordia ages and diagrams were generated using Isoplot/Ex (Ludwig, 2008). Further information on the protocol can be found in [START_REF] Ballouard | Tectonic record, magmatic history and hydrothermal alteration in the Hercynian Guérande leucogranite, Armorican Massif, France[END_REF]. The full set of results is available as Supplementary material (Tables S4 for standards and S5 for samples).

Zircon Lu-Hf isotope determination

Measurements were performed on magmatic zircons previously analyzed for U-Pb dating at GUF, using a Thermo-Finnigan Neptune multicollector ICP-MS attached to a Resolution M-50193 nm Ar-F excimer laser ablation system, equipped with a two-volume Laurin Technic ablation cell. Laser spots with diameters of 40 or 60 μm were drilled "on top" of the existing spots already analyzed for U-Pb dating or in the same domain as identified on the basis of CL images (Fig. 5), with repetition rates of 4 Hz and an energy density of 5 to 6 J•cm -2 . He was used as a carrier gas (~0.6 L•min -1 ) and make-up gas consisting of high-purity Ar (~0.75 L•min -1 ) and N 2 (~0.07 L•min -1 ) was admixed to the carrier gas to improve sensitivity. Post-ablation homogenization is performed by fluxing the gases through a Resolution Instruments Squid® tubing. Data were acquired using multi-collector static mode, during 58 s of measurement characterized by 1.052 s integration time (55 baseline-corrected ratios). 172 Yb, 173 Yb and 175 Lu masses were monitored to allow the correction of isobaric interferences ( 176 Yb and 176 Lu on 176 Hf). Instrumental mass bias for Yb isotopes (calculation of β Yb ) was monitored for each measurement using an exponential law, and corrected to the natural ratio 172 Yb/ 173 Yb = 1.35351. Mass fractionation of Lu isotopes was assumed identical to that of Yb isotopes (β Lu = β Yb ). The isobaric interferences were subsequently corrected to mass bias-corrected 176 Yb/ 173 Yb = 0.79502 and 176 Lu/ 175 Lu = 0.02656 (see Gerdes and Zeh, 2006). Mass bias for Hf isotopes (β Hf ) was determined using an exponential law and normalized to 179 Hf/ 177 Hf = 0.7325. Accuracy and external reproducibility of the method were controlled by repeated analyses of reference zircon standards GJ-1 (Jackson et al., 2004;Morel et al., 2008), Plešovice (Sláma et al., 2008), and Temora (Woodhead et al., 2004) (see Table S6 for results on the standards). The quoted uncertainties on 176 Hf/ 177 Hf ratios and εHf(t) are quadratic additions of within-run precision of each measurement with the external reproducibility (2 S.D.) of the reference zircon standard GJ-1 (~70 ppm). Data reduction was carried out using an in-house MS Excel© spreadsheet (Gerdes andZeh, 2006, 2009).

Calculation of initial 176 Hf/ 177 Hf ratios was performed using the individual 176 Lu/ 177 Hf ratio of each measurement, a decay constant of λ 176 Lu = 1.867 × 10 -11 [START_REF] Scherer | Calibration of the Lutetium-Hafnium clock[END_REF]Söderlund et al., 2004) and the emplacement age obtained by U-Pb zircon dating. For the calculation of the εHf(t), parameters of the chondritic uniform reservoir (CHUR) recommended by Bouvier et al. (2008) were used ( 176 Lu/ 177 Hf = 0.0336; 176 Hf/ 177 Hf = 0.282785). Two-step depleted mantle (DM) Hf model ages (T DM2 C ) were calculated using a DM model considering linear regression from present-day depleted mantle as recommended by Griffin et al. (2002), i.e. 176 Lu/ 177 Hf = 0.0384 and 176 Hf/ 177 Hf = 0.28325, and an average 176 Lu/ 177 Hf of 0.0113 for the crustal reservoir.

Results

Geochemistry

Regardless of the rock type, samples from the VOF are all very silicic (SiO 2 N 68 wt%) and have a granitic (s.s.) composition (Fig. 6a). More specifically, they show high A/CNK (1.05 to 1.4) and A/NK (1.1 to 1.6) implying that their protoliths are peraluminous granites (Fig. 6b). The very high values displayed by some samples (A/CNK in the range 1.4 Couzinié et al. / Lithos 286-287 (2017) 16-34 Fig. 5. Representative cathodoluminescence images of zircon grains from samples of the Velay Orthogneiss Formation. The locations of laser spots (white and yellow circles for U-Pb and Lu-Hf analyses respectively) are indicated along with the spot name (zXX). The corresponding 206 Pb/ 238 U dates are quoted with ± 2σ uncertainty, in Ma. All displayed analyses are concordant at N98% (except those in italic). Hf isotope data are reported using the εHf calculated at the emplacement age of the corresponding sample, quoted with ±2σ uncertainty.

22

S. Couzinié et al. / Lithos 286-287 (2017) [16][17][18][19][20][21][22][23][24][25][START_REF] Faure | Pin and Lancelot[END_REF][27][28][29][START_REF] Marchand | [END_REF][31][START_REF] Berger | [END_REF][33][34] to 1.8) probably reflect alkali losses during amphibolite-facies metamorphism (not identified by the abovementioned filtering procedure, see Section 3.1). Mg# is highly scattered (2 to 60, Fig. 6c). Leucogneisses are SiO 2 richer (N 74 wt%) and have lower and variable Mg# (b 30) compared to augen gneisses (SiO 2 = 69-75 wt.%; Mg# = 30-55). Banded gneisses span in composition between those two endmembers. As a whole, VOF compositions remarkably mimic that of Variscan S-type granites from the eastern Massif Central (Fig. 6a,b,c). We investigated possible systematic differences between the three domains (Pilat, Arcde-Fix and Vivarais) of the VOF. We used linear discrimination analysis (LDA) on major elements, a statistical tool calculating the linear combination of variables that maximizes the difference between three previously defined sets of data (Fig. 6d). LDA was computed using the open-source R language [START_REF] Ihaka | R: a language for data analysis and graphics[END_REF] and the package MASS [START_REF] Venables | Modern Applied Statistics with S[END_REF]. We followed the method of [START_REF] Aitchison | The Statistical Analysis of Compositional Data[END_REF] and implemented the compositional variables X (Al 2 O 3 , MgO, FeO t , TiO 2 , CaO, Na 2 O, K 2 O) as log(X/SiO 2 ) ratios. No systematic difference is observed and samples from all three regions have statistically similar major elements compositions. Like for major oxides, trace element compositions of VOF samples are very homogeneous between the three domains (Fig. 7). Augen gneisses show a slight enrichment in Light Rare Earth Elements (La/ Yb: mostly 6-14), flat Heavy Rare Earth Elements patterns (Dy/Yb: 1.3-3) together with a negative Eu anomaly (Fig. 7a). Leucogneisses are less enriched in LREE (La/Yb: mostly 2-6), have similar HREE patterns and a more pronounced Eu anomaly (Fig. 7a). Banded gneisses seem significantly depleted in HREE compared to the other lithologies (La/Yb: 25 to 50), but this difference may not be statistically significant given that trace elements are only available for two samples. All rock types have multi-element patterns characterized by significant negative Ba-Sr, Nb-Ta and Ti anomalies and positive Pb and U anomalies (Fig. 7b). As a whole leucogneisses are depleted in all incompatible elements compared to augen gneisses with the exception of Nb-Ta (constant) and Rb-U (enriched in the leucogneisses).

U-Pb dating

Zircon textures

Fig. 5 shows representative CL images of zircon crystals from the investigated VOF samples. Zircon grains are idiomorphic to subidiomorphic, display aspect ratios between 1.5 and 3.5 and show welldeveloped pyramidal tips (Fig. 5a,b). Grains range in size from 200 to 350 μm in augen gneisses and are notably smaller in leucogneisses (150-250 μm). Core-rim relationships are commonly observed (Fig. 5). They often consist of CL-dark or bright sub-idiomorphic to rounded cores, mantled by a rim showing typical oscillatory zoning. A careful examination of CL images reveals the existence of small textural discontinuities in such oscillatory zoning, with truncations and irregular (Middlemost, 1994); (b) A/CNK vs. A/NK Shand's diagram [START_REF] Shand | Eruptive Rocks[END_REF]; (c) Mg# vs. SiO 2 . All diagrams were plotted using the GCDkit software [START_REF] Janoušek | Interpretation of whole-rock geochemical data in igneous geochemistry: introducing geochemical data toolkit (GCDkit)[END_REF]; (d) Results of linear discrimination analysis (LDA). More than 80% of the data are indistinguishable from one another. Data for Variscan S-type granites are from Moyen et al. (2017). surfaces being common. Finally, few grains display very CL-bright narrow (b 10 μm) rims (see Fig. 5d).

Sample MM06

This sample is a typical "Arc-de-Fix" augen gneiss collected from the cliff along the RD40 road below the village of S t -Privat-d'Allier (Figs. 2 and4a). Twenty-six analyses were performed on 24 zircon grains. Three cores yield concordant Neoproterozoic 238 U/ 206 Pb dates at 559.7 ± 13.4, 660.3 ± 15.2 and 721.4 ± 16.9 Ma respectively (errors quoted at 2σ, Table S5). Plotted in the Tera-Wasserburg diagram, 21 analyses from rims or grains devoid of any core trend along a mixing line between radiogenic and common Pb compositions. This trend has a lower intercept at 540.5 ± 3.2 Ma (MSWD = 0.26) and an identical Concordia date of 541.8 ± 3.1 Ma (MSWD C + E = 0.34, Fig. 8a) is calculated out of the 16 statistically equivalent concordant analyses. Two spots (z10 and z20) have 206 Pb/ 238 U dates of c. 510 Ma that are statistically different from those of the main population, and were therefore not included in the calculation. There is no systematic relationship between 238 U/ 206 Pb dates and Th/U ratios which range between 0.02 and 0.64. This observation is also valid for the three other samples.

Sample MM11

Sample MM11 is an augen gneiss collected at the "Col de Meyrand" (Fig. 4a). Out of 28 analyses, 7 correspond to zircon cores. Five yielded concordant Neoproterozoic 206 Pb/ 238 U dates ranging from 580.7 ± 14.1 Ma (z30) to 1077.1 ± 25.0 Ma (z33) and two discordant 207 Pb/ 206 Pb dates of 860 Ma and 2100 Ma (Fig. 8b). In the Tera-Wasserburg diagram, a total of 18 spots from zircon rims and core-free grains define a trend with a lower intercept at 541.2 ± 3.6 Ma (MSWD = 0.34), which slope is mostly controlled by discordant spot z38. Excluding the latter and the slightly discordant spot z44, an identical Concordia date of 542.5 ± 3.1 Ma (MSWD C + E = 0.43, Fig. 8b) can be calculated out of 16 analyses. Three spots yielded significantly younger 206 Pb/ 238 U dates (two are discordant and one concordant with a 206 Pb/ 238 U date of 502.6 ± 12.1 Ma) that were thus not included in the calculations.

Sample MM10

MM10 is a leucogneiss collected at the "Pont-du-Bon-Dieu" along the RD6 road south of Labastide-Puylaurent. It features an intricate association with mylonitic augen gneiss (see Fig. 4d). Sixty-five analyses were performed, out of which 12 spots on zircon cores gave concordant Neoproterozoic 206 Pb/ 238 U dates ranging from 560.3 ± 13.2 Ma (z88) to 657.8 ± 14.5 Ma (z136) and 805.8 ± 17.5 Ma (z137) to 921.7 ± 20.6 Ma (z130, Table S5). Three discordant analyses, also from zircon cores, yielded older Paleoproterozoic 207 Pb/ 206 Pb dates of 1600, 1900 and 2400 Ma. Twenty-eight spots from zircon rims or grains without cores trend along a mixing line between radiogenic and common Pb with a lower intercept at 540.7 ± 2.7 Ma (MSWD = 0.11). Considering the concordant analyses only (n = 26), a Concordia date of 541.4 ± 2.3 Ma (MSWD C + E = 0.38, Fig. 8c) can be calculated. Thirteen concordant spots have 206 Pb/ 238 U dates ranging between 523.4 ± 11.1 Ma and 482.4 ± 11.1 Ma. Those were not included in the calculations because as argued below (see Section 5.1), they would correspond to radiogenic Pb loss from the main population at c. 541 Ma.

Sample MM09

Sample MM09 is a leucogneiss boudin stretched within an augen gneiss matrix and exposed along the D906 road south of Langogne (Fig. 4b). Out of 25 analyses, 3 correspond to zircon cores: one displays a concordant 206 Pb/ 238 U date of 686.7 ± 16.3 Ma and two show similar discordant Paleoproterozoic 207 Pb/ 206 Pb dates of 1700 Ma (Table S5).

From the remaining data obtained on rims and core-free zircons, nine concordant spots define a Concordia date of 545.9 ± 4.3 Ma (MSWD C + E = 1.05, Fig. 8d); the rest of the data show younger 206 Pb/ 238 U dates and are notably discordant, with the exception of two concordant spots having 206 Pb/ 238 U dates of 509.9 ± 12.2 Ma and 516.7 ± 12.4 Ma respectively.

Lu -Hf isotope data

Zircon Lu-Hf analyses obtained for augen gneisses MM06 and MM11 are displayed in Table S6. Only magmatic zircon grains and rims were analyzed. Therefore, initial Hf isotope compositions were calculated using the intrusion age determined for each sample (see Section 4.2). The 176 Hf/ 177 Hf(t) ratios of magmatic zircons from augen gneiss MM06 range from 0.282376 ± 0.000023 to 0.282487 ± 0.000036 (2 S.E.standard error), corresponding to εHf(t) of -2.4 to 1.6 with a chondritic average value of -0.2 ± 2.9 (2 S.D.standard deviation; Fig. 9a andTable 1). Augen gneiss sample MM11 shows a tighter range of zircon 176 Hf/ 177 Hf(t), from 0.282407 ± 0.000027 to 0.282462 ± 0.000025 (2 S.E.standard error) equivalent to εHf(t) of -1.3 to 0.7 (Fig. 9a) and yielding an identical average εHf(t) at -0.2 ± 1.2 (2 S.D.standard deviation; Table 1).

Discussion

Interpretation of the U-Pb data and orthogneisses emplacement ages

All investigated samples are characterized by a largely dominant population of zircon grains having statistically equivalent and concordant 206 Pb/ 238 U dates between 550-540 Ma, which we interpret as the crystallization ages of the VOF granitic protoliths. This interpretation is supported by (i) the fact that these data were obtained on zircon rims or grains devoid of any core; (ii) the typical magmatic oscillatory zoning showed by the analyzed domains (Fig. 7); and (iii) the well-developed {211} pyramids of these crystals, which are characteristic of zircon grown in peraluminous granitic magmas (Belousova et al., 2006;[START_REF] Pupin | Zircon and granite petrology[END_REF], in line with whole-rock geochemistry of the investigated samples (Fig. 5b).

From this perspective, we interpret the 28 analyses obtained from zircon cores, showing notably older 238 U/ 206 Pb dates (from 560 Ma up to 1100 Ma, 75% of which being N 95% concordant), as reflecting zircon inheritance from the source of these (meta)granites or xenocrysts sampled from the country-rocks during magma ascent and emplacement. The presence of these inherited cores and xenocrysts is significant because they occur in all of the four investigated samples (Fig. 8) and represent a non-negligible proportion of the dataset (ca. 19%). In addition, CL images hint the presence of more small, strongly resorbed or irregular cores (see Fig. 7c close to z134 or 7d close to z78) that could not be analyzed by LA-ICP-MS.

A significant amount of zircon analyses (including 17 concordant ones) show 206 Pb/ 238 U dates younger than the 550-540 Ma crystallization age, in the range 523 to 482 Ma. These are well represented in the leucogneiss samples (Fig. 8), particularly MM10 (Fig. 8c). We argue that these dates do not correspond to any geological event but rather result from recent radiogenic Pb loss affecting the main, 545-540 Ma-old zircon population. Firstly, these dates are often associated with incoherent core-rim relationships (cores having younger 238 U/ 206 Pb dates than their associated rims, see for instance zircons 93, 103 and 106, Fig. 7c). Second, recent Pb loss is represented by horizontal lines in the Tera-Wasserburg diagram because it does not affect 207 Pb/ 206 Pb ratios (Fig. 8c). The weak curvature of the Concordia at Paleozoic times implies that the Discordia and Concordia curves are nearly parallel so that any c. 540 Ma-old zircon having experienced a limited Pb loss would still be sub-concordant within uncertainty.

Following the abovementioned interpretations, the igneous protoliths of all the investigated VOF samples show overlapping emplacement ages of c. 542 Ma, at the Ediacaran/Cambrian boundary (541 ± 1 Ma, [START_REF] Finney | The ICS international chronostratigraphic chart[END_REF]. This age is close to, yet significantly older than the Cambrian Rb/Sr date of 528 ± 9 Ma obtained by R'Kha [START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF] on Arc de Fix augen gneisses. It complies with the zircon Pb evaporation age of 533 ± 22 Ma (Mougeot et al., 1997) and the chemical U-Th-Pb monazite date of 543 ± 25 Ma (Be Mezeme et al., 2006) both obtained on unmolten to anatectic Arc de Fix augen gneisses. It is also identical to the whole-rock Rb-Sr age of 545 ± 14 Ma determined by Caen-Vachette (1979) for the Pilat leucogneisses.

Petrogenesis of the magmatic suite

The VOF samples display remarkable geochemical homogeneity, regardless of their geographic provenance. Their composition is consistent with the chemistry of peraluminous S-type granites (see Fig. 6). Moreover, zircon grains from augen-and leucogneisses have similar, low aspect ratios which comply with a plutonic origin for the protoliths of both rocks (Corfu et al., 2003), and morphologies typical of crystals formed in S-type granitic magmas (Belousova et al., 2006;[START_REF] Pupin | Zircon and granite petrology[END_REF] (Fig. 5). Furthermore, the obtained emplacement ages for the four samples (545-540 Ma) are overlapping within analytical uncertainties. All these lines of evidence indicate that the VOF represents a former, large S-type granitic batholith emplaced at the Ediacaran/Cambrian boundary that was subsequently deformed and dismembered by Variscan tectonics. The aim of this section is to characterize its petrogenesis.

Given the narrow range of silica contents (mostly 70-76 wt%) and the apparent similar chemical composition of investigated samples, we plotted the geochemical data using the principal component approach. This procedure helps pinpointing petrogenetic trends [START_REF] Buccianti | The complex nature of potassic and ultrapotassic magmatism in Central-Southern Italy: a multivariate analysis of major element data[END_REF]Janoušek et al., 2004). Principal components were calculated using the internal routine of the GCDkit software [START_REF] Janoušek | Interpretation of whole-rock geochemical data in igneous geochemistry: introducing geochemical data toolkit (GCDkit)[END_REF] after recasting the chemical compositions to 100% in the system SiO 2 -Al 2 O 3 -MgO-FeO-TiO 2 -CaO-Na 2 O-K 2 O. The first three principal components account for 86% of the cumulative variance of the system. As principal component 1 (P.Comp 1 ) mostly opposes silica vs. compatible elements contents (MgO, FeO, TiO 2 , CaO), the most silicic rocks (i.e., the leucogneisses) feature high P.Comp 1 values (Fig. 10). Similar to trends observed in major elements diagrams, the banded gneisses' compositions spread between an augen gneiss and a leucogneiss endmember.

Source of the magmatic suite

The complete absence of mafic or even intermediate meta-igneous rocks in the VOF together with the observation of inherited zircon cores in the dated samples precludes the formation of the magmatic suite by fractionation of mantle-derived magmas. This absence rather suggests that the granitic magmas originated from melting of pre-existing crustal lithologies. The low CaO contents (0.2-1.5 wt%) displayed by samples from the VOF discard amphibole-rich mafic rocks as a potential source material [START_REF] Coldwell | Deep crustal melting in the Peruvian Andes: felsic magma generation during delamination and uplift[END_REF][START_REF] Sisson | Voluminous granitic magmas from common basaltic sources[END_REF], such that meta-sediments and meta-intermediate to felsic igneous rocks are most adequate as potential sources.

Fig. 11 compares the composition of VOF samples to primary liquids formed by melting of a range of meta-sedimentary and meta-igneous crustal lithologies. Relevant melting conditions correspond to a range of crustal pressures from 3 to 15 kbar and temperatures b900 °C in agreement with (i) the absence of magmatic orthopyroxene in the investigated suite [START_REF] Frost | On charnockites[END_REF]; (ii) first-order estimates given by zircon saturation thermometry, the persistence of inherited zircon cores in the dated samples indicating maximum magma temperatures of 780 ± 15 °C upon emplacement (calculated with the equation of Boehnke et al. (2013)) and therefore, melting temperatures that cannot have been in excess of 840-885 °C considering a maximum melting pressure of 15 kbar and reasonable adiabats (i.e. between 4 and 7 °C/kbar; Annen et al., 2006;[START_REF] Clemens | Ascent mechanisms of granitic magmas: causes and consequences[END_REF][START_REF] Holtz | Maximum and minimum water content of granitic melts-implications for chemical and physical properties of ascending magmas[END_REF]. Experimental melt compositions are projected on the principal component framework determined from statistical analysis of the VOF samples (Fig. 10). The considered experimental studies together with respective starting materials and P-T conditions are summarized in Table 2.

Clearly, tonalites and metaluminous granodiorites are inappropriate source rocks because melts derived from those lithologies have respectively lower Mg# (Fig. 11f) and/or lower K 2 O/Na 2 O (Fig. 11h) than natural samples. Peraluminous granodiorite melts display more adequate compositions but can only account for a small part of the natural samples variability centered on P.Comp 1 ~0 (Fig. 11). By contrast, melting of quartz-rich to quartz-poor pelites, greywackes and volcanoclastic rocks generates a range of primary melt compositions that fairly reproduce the compositional scatter of the augen-and part of the banded gneisses, i.e. samples with -4 b P.Comp 1 b 0.5. This is in line with the VOF samples displaying a geochemical affinity to S-type granites (see Fig. 6) that derive from melting of such lithologies (Chappell and White, 2001). Therefore, it is reasonable to consider that the granitic protoliths of augen-and banded gneisses from the VOF represent liquids which originated from melting of a heterogeneous sedimentary sequence at 750 b T b 900 °C and 3 b P b 15 kbars. This is consistent with the wide range of inherited zircon ages, scattering from 560 to 1100 Ma (Fig. 8), which points to an Ediacaran depositional age for the source sediments.

Importantly, leucogneiss samples (with P.Comp 1 N 0.5) clearly differ from any investigated experimental melt composition. Two nonexclusive scenarios may account for their origin: (i) leucogneisses derive from source materials and/or at P-T conditions not represented in our database; or (ii) they result from fractionation of the granitic magmas at the origin of augen-and banded gneisses with P.Comp 1 b 0.5. The first hypothesis is unlikely, since the range of investigated source materials (Table 2) is fairly representative of the most common felsic sources in the crust, and the investigated temperature range (680-900 °C) encompasses a wide domain of melting conditions, from water-present melting (c. 650-700 °C) to muscovite dehydration melting (c. 720-750 °C) and biotite dehydration melting (c. 850-875 °C). The feasibility of the fractionation hypothesis is tested hereafter.

Leucogneiss petrogenesis

In this section, we investigate whether leucogneisses could be derived from fractionation of the magma at the origin of the augen gneisses. Fig. 12a and b depicts the chemical evolution of a magma fractionating minerals typically found in peraluminous S-type granites: K-feldspar, oligoclase, biotite, muscovite, cordierite, garnet [START_REF] Bea | Differentiation of strongly peraluminous, phosphorus granites: the Pedrobernardo pluton, central Spain[END_REF][START_REF] Tartèse | Differentiation of peraluminous leucogranites "en route" to the surface[END_REF]. Fractionation vectors are calculated using mass balance for major elements, and Rayleigh-type fractionation together with partition coefficients for traces (cordierite could not be modeled for traces due to the lack of available partitioning data). In terms of major elements, fractionation of an augen gneiss-like liquid to a leucogneiss composition cannot be driven by muscovite, nor K-feldspar, as both result in too high values for PComp.3 (Fig. 12b). Leucogneisses are better reproduced by concomitant fractionation of plagioclase and a ferromagnesian phase (biotite, garnet and/or cordierite, Fig. 12a,b). The low Ba-Sr contents displayed by leucogneisses can result from fractionation of either a K-feldspar dominated assemblage (however, this is ruled out by major elements), or a polymineralic assemblage comprising 40% biotite and 60% plagioclase (Fig. 12c). Fractionation of plagioclase is also in agreement with the more pronounced Eu anomaly displayed by leucogneisses (Fig. 6). The decrease in HREE and Y contents from augen gneisses to leucogneisses could result from fractionation of a small amount of garnet, zircon or xenotime [START_REF] Bea | Residence of REE, Y, Th and U in granites and crustal protoliths; implications for the chemistry of crustal melts[END_REF]. The same observation for LREE could originate from minor fractionation of apatite and/or monazite [START_REF] Bea | Residence of REE, Y, Th and U in granites and crustal protoliths; implications for the chemistry of crustal melts[END_REF]. As a result, fractionation of a Pl + Bt (+ accessory phases) assemblage from an augen gneiss-like magma satisfactorily accounts for the composition of leucogneisses.

Emplacement depth

Leucogneisses are highly silicic (SiO 2 generally ranging between 74 and 77 wt.%), mostly contain quartz + feldspar, and, as demonstrated above, correspond to residual melts after fractionation of a Pl + Bt assemblage out of a magma similar to augen gneisses. Therefore, the leucogneisses compositions should be very close to that of the minimum or eutectic in the haplogranitic system. The position of this minimum/eutectic in the ternary Qz-Ab-Or diagram is a function of the water activity and the pressure of crystallization (Johannes and Holtz, 1996). At a given pressure, decreasing water activity (corresponding to H 2 O-undersaturated melts) shifts the position of the minimum/eutectic towards the Qz-Or join keeping the normative Qz proportion constant (Johannes and Holtz, 1996). The latter is therefore strictly pressure-dependent and is an indicator of the pressure of magma crystallization. In this section, we aim at retrieving the depth of emplacement/crystallization of the batholith by comparing the compositions of leucogneisses to that of the haplogranitic minimum/eutectic as predicted by experimental data.

Experimental data on the Qz-Ab-Or-H 2 O system have been compiled by [START_REF] Blundy | Ascent-driven crystallisation of dacite magmas at Mount St Helens, 1980-1986[END_REF]. We projected natural leucogneiss compositions following the recommendations of the same authors by: (i) calculating the CIPW norm; (ii) correcting the effect of the normative component on the position of the natural melt in the ternary diagram. Only samples with measured Fe 2 O 3 /FeO ratios were retained (total of 66 analyses) to ensure calculation of accurate normative values. Leucogneisses from the VOF cluster around the minimal melt compositions expected at pressures of 0.5-2 kbars and water-saturated conditions (a H2O = 1, Fig. 13). Few samples show higher Qz modal values which could result from limited sub-solidus chemical modifications or the presence of quartz veinlets.

Since leucogneisses and augen gneisses are intimately associated in the field (see Section 2.2), a pressure of crystallization for the whole batholith of 0.5-2 kbars can be inferred. This corresponds to depths of ~2 to 7 km and suggests that the VOF S-type granites emplaced at shallow crustal levels. 2). Experimental data are projected on the principal component framework. Same legend as Fig. 4.

Interpretation of Lu -Hf data

The εHf(t) variability within a given sample is small (b4 and even b 2 εHf-units in MM11) and of the same order of magnitude than the analytical uncertainties (i.e. ±1.1εHf-units), indicating that zircons crystallized from a magma with relatively homogeneous Hf isotope composition. Both samples reveal identical average εHf(t) clustering around the chondritic value, taken as representative of that of the magma at the time of crystallization.

Clearly, a chondritic mantle source for the magmas at the origin of the VOF must be discarded because geochemical data are rather in line with a sedimentary source (see Section 5.2.1). Accordingly, the chondritic value could originate from the melting of an isotopically homogeneous sedimentary reservoir that would itself rework continental crust extracted from the Depleted Mantle (DM) at ~1.3 Ga (calculated model age with a crustal 176 Lu/ 177 Hf of 0.0113, from Taylor and McLennan (1985)). However, there is no crust of that specific age in the north Gondwana margin, where crust production occurred Stevens (1995), Patino-Douce and[START_REF] Patiño-Douce | Phase equilibria and melt productivity in the pelitic system: implications for the origin of peraluminous granitoids and aluminous granulites[END_REF], [START_REF] Vielzeuf | Experimental determination of the fluid-absent melting relations in the pelitic system[END_REF] 5-10 825-900 Greywacke Patino-Douce and Harris (1998), Stevens (1995), Patino-Douce and [START_REF] Patiño-Douce | Effects of P, f(O 2 ) and Mg/Fe ratio on dehydration-melting of model metagreywackes[END_REF], Montel and Vielzeuf (1997) 3-10 800-900 Metaluminous granodiorite [START_REF] Bogaerts | Phase Equilibria of the Lyngdal Granodiorite (Norway): Implications for the Origin of Metaluminous Ferroan Granitoids[END_REF] 3.7-4.1 775-900 Peraluminous granodiorite Holtz and Johannes (1991) 3-5 700-800 Tonalite [START_REF] Watkins | Archaean TTGs as sources of younger granitic magmas: melting of sodic metatonalites at 0.6-1.2 GPa[END_REF] 6-12 680-900 Metavolcanoclastic rock Skjerlie and Johnson (1996) 10-15 850-900

PComp

Bt Grt

PComp S8). Same legend as Fig. 4. Larger symbols correspond to dated samples. 29 S. Couzinié et al. / Lithos 286-287 (2017) 16-34 in the Archean , Paleoproterozoic (1.8-2.2 Ga) and Neoproterozoic (0.6-0.7 Ga) (Gerdes and Zeh, 2006;Linnemann et al., 2014;Nance et al., 1991). As a result, the chondritic signature of the VOF parental magmas most probably stems from the melting of a sedimentary source composed of a mixture of the three above-mentioned reservoirs, including at least 50% of Neoproterozoic juvenile crust (as proposed for Variscan S-type granites from the same area (Moyen et al., 2017;Turpin et al., 1990). Ediacaran metasediments throughout the Variscan belt of Western Europe are characterized by a very large spread of detrital zircon εHf(t), specifically ranging from c. +10 down to c. -40 at 600 Ma (Fig. 9b), interpreted as reflecting the contribution of terrigenous material from both juvenile Neoproterozoic crust (such as the Arabian-Nubian Shield) and ancient, Paleoproterozoic to Archean crust from Gondwana (Chelle-Michou et al., 2017;Linnemann et al., 2014;Orejana et al., 2015). Therefore, the Ediacaran metasediments represent adequate sources for the VOF granites. The U-Pb dates of inherited zircons in the VOF samples strongly support this interpretation, since those are dominantly in the range 560-900 Ma (20 analyses out of 28, i.e. 71%) that is typical for detrital zircons in Ediacarian metasediments of the northern Gondwana margin (Chelle-Michou et al., 2017;Linnemann et al., 2014;Orejana et al., 2015;[START_REF] Teixeira | Combined U-Pb geochronology and Lu-Hf isotope systematics by LAM-ICPMS of zircons from granites and metasedimentary rocks of Carrazeda de Ansiães and Sabugal areas, Portugal, to constrain granite sources[END_REF]; see also Fig. 8).

The Hf isotope homogeneity displayed by the parental magmas of the VOF (Fig. 9b) is rather uncommon for S-type granites, which magmatic zircons commonly show larger variations of εHf(t), most often of ~10 epsilon-units (Appleby et al., 2009;Farina et al., 2014;[START_REF] Teixeira | Combined U-Pb geochronology and Lu-Hf isotope systematics by LAM-ICPMS of zircons from granites and metasedimentary rocks of Carrazeda de Ansiães and Sabugal areas, Portugal, to constrain granite sources[END_REF]Villaros et al., 2012). Based on the natural case of the Cape Granite Suite in South Africa, Villaros et al. (2012) proposed that the Hf isotope scatter observed in S-type granites results from the dissolution at emplacement level of inherited detrital zircons in the melt phase. Such grains being isotopically disparate, their dissolution creates small-scale Hf isotopic heterogeneities captured by newly formed zircon when the melt crystallizes. However, Farina et al. (2014) showed that the cooling history of the magmatic body exerts a strong control on this process, with fast cooling rates (≥ 0.0125 °C/yr) leading to rapid zircon saturation. In that case, especially if some zircon has already been dissolved during melting and/or transport and the Hf isotopic composition was homogenized thereby, igneous zircons crystallized at the emplacement level would not show strong Hf isotope heterogeneities (i.e. about 1 εHf unit even though the initial inherited zircons showed compositional variation in excess of 10 εHf units; Farina et al., 2014). It is therefore likely that the parental magmas of the VOF experienced such a process, i.e. (i) inherited zircon dissolution during melting and/or ascent in the crust; (ii) coeval homogenization of Hf isotopic compositions in the melt; and (iii) limited further dissolution at the emplacement level (if any).

Liquids formed by melting of sedimentary lithologies at 750-850 °C can dissolve up to 115-390 ppm Zr (calculated using the equation of Boehnke et al., 2013 and the composition of experimental melts from the compilation presented in Table 2), which corresponds to 14 to 48% dissolution of detrital zircons present in the sedimentary source lithology, assuming a source composition of ca. 200 ppm Zr (close to the average composition of the upper crust, Rudnick and Gao, 2003), that all Zr is hosted in detrital zircons and an average melt fraction of ca. 25% (derived from experimental data listed in Table 2). Consistently, Zr concentrations in augen and banded gneisses from the VOF range mostly from ca. 50 to 180 ppm, indicating that they would have left the source in a Zr-undersaturated state after dissolution of maximum 6-23% detrital zircon (and probably much less, given the presence of inherited zircons in the VOF samples) using the same parameters as above. Close to their liquidus, the resulting melts would have readily undergone homogenization through advection and elemental/isotopic diffusion. Conversely, zircon saturation temperatures of the VOF samples are around 780 °C (see Section 5.2.1), meaning that they would have very rapidly reached saturation upon emplacement and cooling, especially considering that they emplaced at relatively shallow crustal levels (≤7 km, see Section 5.2.3). This would have indeed promoted fast cooling rates and in turn, limited dissolution (if any) of the remaining inherited zircon cores (Farina et al., 2014). All lines of evidence therefore suggest that the unusually homogeneous zircon Hf isotopic composition of the S-type VOF granites result from a combination of Zr-undersaturated conditions during melting and transport in the crust followed by early saturation upon emplacement owing to rapid cooling at shallow crustal levels.

Geodynamic setting of late Ediacaran magmatism in the French Massif Central

A compilation of available geochronological data (n = 74 dated samples) shows that pre-Variscan magmatism in the French Massif Central spanned over 150 Ma from the Ediacaran (c. 600 Ma) to the late Ordovician (c. 450 Ma) and possibly the Early Silurian (Fig. 14). The age pattern shows a bimodal distribution reflecting the existence of two pulses of magmatic activity at c. 475 Ma (Ordovician) and c. 540 Ma (Ediacaran/Cambrian boundary). As outlined before, Ordovician magmatic activity in the FMC is interpreted as reflecting longlived extension of the Northern Gondwana margin that culminated in rifting and the opening of small-scale oceanic basins (Lardeaux et al., 2014). However, at the scale of the Variscan belt, the significance of this Ordovician event is much discussed and contrasted geodynamic settings have been proposed such as an active margin environment with a fore-arc accretionary complex (Zurbriggen, 2015) and continental subduction (Villaseca et al., 2016).

The existence of the Ediacaran/Cambrian peak together with its origin and significance has not been addressed in the FMC. By that time, the crust segment today exposed in the FMC was located along the northern margin of Gondwana (Stampfli et al., 2013) and was therefore likely affected by the Cadomian orogeny, a Cryogenian-Ediacaran Western Pacific-type marginal orogenic system (Nance et al., 1991). Accordingly, remnants of Cadomian granitoid rocks have been described in several parts of the Variscan belt (see review in Garfunkel (2015)). In the following, we compare the Cadomian magmatic record of the eastern FMC to that of the closest crustal block shaped by the Cadomian orogeny but nearly devoid of Variscan imprint: the Mancellian Domain of the North Armorican Massif (Fig. 1). Today located 500 km NW of the Velay Dome, it preserves an excellent record of the Cadomian orogenic evolution (Ballèvre et al., 2001;Chantraine et al., 2001) and the Minima/eutectics (black squares) as compiled by [START_REF] Blundy | Ascent-driven crystallisation of dacite magmas at Mount St Helens, 1980-1986[END_REF]. Shift of minima/eutectic positions with decreasing water activity from Johannes and Holtz (1996).

developed comparison would better constrain the origin and geodynamic setting of late Ediacaran magmatism in the FMC.

The Mancellian Domain comprises two main lithological units: (i) a terrigenous sedimentary sequence of Ediacaran ("Brioverian") age, interpreted as a turbidite-type back-arc to retro-arc basin (Ballèvre et al., 2001;Linnemann et al., 2014); (ii) a range of granitoids which intrude the sediments and develop thermal aureoles that suggest emplacement depths lower than 6 km (Ballèvre et al., 2001). Available ages on this magmatism range between 550 and 540 Ma (Egal et al., 1996(Egal et al., , 2011;;Peucat, 1986). This configuration clearly resembles that observed in the LGU of the eastern FMC (Ledru et al., 2001). As demonstrated above, orthogneisses correspond to a late Ediacaran S-type granitic suite emplaced at shallow crustal levels (2-7 km). Field observations clearly indicate that the VOF is intrusive within the regional paragneisses (Ledru et al., 1994). Consequently, our dating results on the VOF importantly constrain a minimum deposition age of 545 Ma for the sedimentary protoliths of the paragneisses, besides consistent with constraints based on the age of the youngest detrital zircons in these rocks (Chelle-Michou et al., 2017). We thus propose that Velay paragneisses are akin to the Brioverian sediments and that the VOF is the counterpart of the Mancellian granitoids.

However, when compared to the VOF, Mancellian plutonic rocks show a larger petrographic diversity as they include mafic to intermediate rocks which are not observed in the VOF. Accordingly, the Mancellian suite displays a larger scatter in SiO 2 contents (49-78 wt%) than the VOF (69-79 wt%) (Fig. 15a). Moreover, the dominant phase of the Mancellian suite is a granodiorite as opposed to a granite and leucogranites only form subordinate massifs. The Mancellian granodiorites trend between two endmembers in the ternary CaO - (Laurent et al., 2014) (Fig. 15b). This observation suggests a dual origin by: (i) melting of sedimentary materials in agreement with petrographic (Brown, 1995) and isotopic data (D'Lemos and Brown, 1993); (ii) involvement of K-rich mantle-derived magmas (Fig. 15b), either as a component of the source (remelting of underplated mafic rocks) and/or via magma mixing/mingling as suggested by the occurrence of mafic microgranular enclaves [START_REF] Jonin | Un batholite fini-précambrien : le batholite mancellien (Massif armoricain, France)[END_REF] and the presence of mafic/intermediate calc-alkaline rocks as part of the suite (Le [START_REF] Gall | Petrology of late Cadomian magmatism in the northern Armorican Massif; the Ernee and Tregomar mafic and ultramafic complexes[END_REF]. Leucogranites have been interpreted as sediment-derived melts produced under high a (H2O) conditions and are not genetically linked to the granodiorites (Brown, 1995). As a result, the respective petrogenesis of Mancellian and VOF granitoid suites contrast by the extent of mantle contribution (respectively significant vs. lacking) and the relative role played by fractionation in accounting for the most felsic compositions.

K 2 O/Na 2 O - Al 2 O 3 /(FeO t + MgO) diagram
The proposed geodynamic setting for Mancellian magmatism corresponds to the post-570 Ma inversion of a back-arc basin (the Brioverian sequence) in a transpressional regime coeval with collision between the Cadomian arc and the Gondwana continent (Chantraine et al., 2001;Dallmeyer et al., 1991;Linnemann et al., 2014). Given the evidence for limited thickening (maximum crustal thickness of ~40 km according to Ballèvre et al., 2001) and the presence of a mantle component in the Mancellian suite, crustal melting is considered to have been triggered by the underplating of mafic magmas (Ballèvre et al., 2001;Dissler et al., 1988;Linnemann et al., 2014). In contrast, the lack of substantial evidence for mantle-derived magmatism in the VOF despite its large surface (~1800 km 2 ), especially the invariably (leuco)granitic character and high SiO 2 content (N68 wt.%) of the samples (see Fig. 6), rules out mafic magma underplating as a potential heat source. The Cadomian back-arc basin corresponded to stretched and thinned continental crust (Brown and D'Lemos, 1991;Chantraine et al., 2001; Yz ( 20)

Pt ( 8) AF ( 9) AF ( 6) AF ( 6) AF ( 6) AF ( 6)

Ap [START_REF] Faure | Pin and Lancelot[END_REF] Ap ( 26) Ap ( 26)

M t M (26)
Ba [START_REF] Faure | Pin and Lancelot[END_REF] Ap [START_REF] Faure | Pin and Lancelot[END_REF] Ap [START_REF] Faure | Pin and Lancelot[END_REF] Pe [START_REF] Faure | Pin and Lancelot[END_REF] Tr ( 28) AC ( 22)

Me ( 16) Th ( 37)

Th (21) PV (16) S t Y (21)
Tu ( 16) Au ( 16) Ch ( 21)

Me ( 25) Sa ( 24)

La ( 21)

Mu (12)
S t E ( 38)

PL (39)

He ( 39) So ( 33) Se ( 7)

Ps ( 15)

Cp ( 5)

Pa ( 1)

Pi ( 11)

Vr ( 17) MC ( 16) Ru ( 4)

Ro ( 27) Ma ( 27) Ma ( 27) Ma ( 27) LB ( 29) LB ( 29) LB ( 29)

RA [START_REF] Berger | [END_REF] Lv ( 34) Lv ( 34)

Po ( 18)

Xi ( 36)

Re ( 19) SS ( 16)

CV ( 16)

Mr (30)
S t Ay ( 13) Tr ( 28) LB ( 29) Rd ( 2 Linnemann et al., 2014) and by analogy with modern back-arc settings, high mantle heat flow was expected in this crust segment (Currie and Hyndman, 2006). As demonstrated by Clark et al. (2011), thermal relaxation following stacking of back-arc units generates temperatures in the middle crust in excess of 750 °C, compatible with extensive melting of sedimentary lithologies and with the conditions of formation inferred for the VOF parental magmas based on experimental constraints and zircon saturation (see above). Therefore, limited thickening of anomalously warm Cadomian back-arc basins would have triggered significant crustal melting (Brown and D'Lemos, 1991). As a result, we propose that the VOF is a lateral equivalent of the Mancellian batholith in an area unaffected by mantle melting during the Cadomian back-arc basin inversion. Several reasons can explain the apparent lack of coeval mantlederived magmatism including: (i) previous depletion of the underlying mantle during back-arc spreading as evidenced by the 590-570 Ma tholeiitic to calc-alkaline mafic magmatism observed in parts of the Northern Armorican Massif (Chantraine et al., 2001;Linnemann et al., 2014); or (ii) lateral variations in the Cadomian subducting slab dynamics with localized break-off that strongly affected the thermal regime of the back-arc mantle (Nance et al., 2010).

Conclusion

Remnants of a Cadomian basement are described in the Velay area (eastern French Massif Central) where an S-type granitic suite intruded Ediacaran sediments at c. 542 Ma. The main phase of this large (~1800 km 2 ) batholith corresponded to a porphyritic granite (transformed into an augen gneiss during the Variscan orogeny) while some magmas evolved by fractional crystallization towards leucogranitic compositions (corresponding to the present-day leucogneisses). Such voluminous magmatism was likely caused by the inversion of a backarc basin domain at the end of the Cadomian orogeny, leading to limited stacking of supracrustal sequences in a high thermal regime that favored significant melting. This is supported by the homogeneous εHf(t) of the VOF zircons compared with their inferred protoliths (sediments derived from various Gondwana-related reservoirs with extremely contrasted isotopic signatures) which points to dissolution of detrital zircons in the source and rapid cooling upon emplacement. From a crust evolution perspective, the Cadomian magmatism in the Velay area was strictly crust-derived and thus attests to substantial reworking of older crust away from a proper continent-continent collision zone. Conversely, there is currently no compelling evidence for Cadomian crust production in the FMC.

Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.lithos.2017.06.001. (Middlemost, 1994) (Laurent et al., 2014). The fields represent the composition of melts derived from a range of potential sources. MME: mafic microgranular enclaves.

; (b) ternary CaO -K 2 O/Na 2 O -Al 2 O 3 /(FeO t + MgO) diagram
2.2 Metasediments in and around the Velay dome

Introduction

The French Massif Central crust segment typically lacks any remnant of old Precambrian rocks, neither at surface level (Melleton et al., 2010;[START_REF] Roques | Substratum antéhercynien et collision hercynienne dans le Massif central français[END_REF] nor in the lower crustal xenoliths sampled by Cenozoic volcanoes (Féménias et al., 2003;[START_REF] Rossi | Variscan to eo-Alpine events recorded in European lower-crust zircons sampled from the French Massif Central and Corsica, France[END_REF]Supply, 1981). Excluding geochronological results obtained by the multi-grain zircon UPb IDTIMS method, likely to yield mixed ages, the oldest igneous rocks from the FMC correspond to the c. 540 Ma-old meta-granites from the Velay Orthogneiss Formation (see above). In the Velay dome, metasediments constitute the country-rocks within which the VOF (meta)granites emplaced (Ledru et al., 1994). The age pattern of inherited grains/xenocrysts in the VOF and younger Variscan granitoids suggests that the Velay metasediments were deposited in the Ediacaran (Couzinié et al., 2014;Chelle-Michou et al., 2017;Laurent et al., 2017). Therefore, such lithologies would correspond to the most ancient autochtonous rocks of the eastern FMC and would have recorded the earliest events that formed the FMC crust.

This section provides a new set of UPbHf measurements performed on detrital zircon grains extracted from four Velay metasediments. It aims at providing further constraints on: (i) the maximum depositional ages of the protoliths; (ii) the origin and nature of the detritus that fed the sedimentary basins and ultimately built up the rst continental crust of the FMC.

Investigated samples

The sampling strategy was designed to cover the most typical metasedimentary formations in and around the Velay dome. Data are already available for the eastern ank of the dome (Chelle-Michou et al., 2017) which has accordingly not been re-sampled.

Geochemical data for the investigated samples are available in the Appendix Table B1. This sample was collected along the N82 road, at the southern exit of Saint Etienne (GPS coordinates: 45.40051,4.4165). It belongs to a 40 cm-thick meta-sandstone (quartzite) body interbedded within amphibolite-facies meta-pelites. The latter are generally referred to as "Pilat micaschists" [START_REF] Chenevoy | Notice explicative, Carte géol[END_REF][START_REF] Gardien | Reliques de grenat et de staurotide dans la série métamorphique de basse pression du Mont Pilat (Massif Central français) : témonis d'une évolution tectonométamorphique polyphasée[END_REF] and form a constituent lithology of the Lower Gneiss Unit in the northern part of the Velay dome. PIL-16-01 is very silicic (SiO 2 > 87%) and dominantly composed of quartz and muscovite with subordinate amounts of feldspar, FeTi oxides and zircon (Fig. 2.2a). This specimen was sampled along the D51 road, between the villages of ChavaniacLafayette and Jax (45.16402, 3.60390). It corresponds to a meter-thick quartz-rich layer within the "Senouire" amphibolite-facies micaschists, a typical metasedimentary unit of the western ank of the dome (Ledru et al., 1994). The rock is mostly composed of quartz and biotite with minor amounts of muscovite, garnet, plagioclase, FeTi oxides and zircon (Fig. 2.2b).

CHA-16-02 Collected in the southwestern part of the dome, near the village of Chasseradès, this sample arguably corresponds to a meta-arkose because of: (i) its moderate SiO 2 /Al 2 O 3 and Fe 2 O 3 /K 2 O ratios (< 6 and 0.7 respectively ; Herron, 1988); (ii) the high modal proportion of feldspar which, together with quartz, builds up most of the rock.

Other minerals include garnet, muscovite, FeTi oxides and zircon (Fig. 2.2c). The 20 cm-thick meta-arkose layer is closely associated with amphibolite-facies micaschists [START_REF] Briand | Notice explicative, Carte géol[END_REF]Négron, 1979;[START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF]. Ledru et al. (2001), [START_REF] Mintrone | Constraining the duration of metamorphic events by modeling of phase equilibrium and diusion in garnet[END_REF] and regional geological maps of France at scale 1/50,000. This sample was taken from a regionally famous outcrop known as "Pontde-Bayzan" in the bed of the Ardèche river, west of the Lalevade-d'Ardèche village (described in [START_REF] Barraud | Analogue models of melt-ow networks in folding migmatites[END_REF]Be Mezeme et al., 2005a andMontel et al., 1992). PdB-16-01 is an anatectic paragneiss similar to those encountered in the southern part of the dome [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]. Only the melanocratic part of the sample, presumably corresponding to paleosome or residuum in the sense of [START_REF] Sawyer | Atlas of Migmatites[END_REF], was selected for detrital zircon analysis. The mineral assemblage consists of quartz, plagioclase, alkali-felspar and biotite with accessory zircon, monazite and apatite (Fig. 2.2d).

Analytical techniques

Zircon grains were separated from the powdered rock samples at Saint-Etienne University using conventional techniques described section 2.1, subsequently cast into epoxy mounts and polished down to an equatorial grain section. CL-imaging was performed at the Laboratoire Magmas et Volcans in Clermont-Ferrand (France) using a Jeol JSM-5910 SEM. Selected grains were dated by LAICPMS at ETH Zürich (see Appendix B.3.3 for analytical notes and Tables B6 andB9 for standards and samples results). In situ Hf isotope measurements were also performed at the Laboratoire Magmas et Volcans. The analytical procedure is reported Appendix B.4.2 and Table B10. The full set of results (standards and samples) is available Tables B13 andB14.

Zircon description

Zircon grains in the four investigated samples are mostly colorless, some being pinkish or yellowish. Their shapes vary from rounded (notably in sample PIL-16-01) to sub-idiomorphic (sample PdB-16-01) with aspect ratios between 1:1 (rounded) and 1:3.

Grains range in size from 50 to 160 µm, the shortest being encountered in . Cathodoluminescence images reveal very diverse internal structures (Fig. 2.3). Oscillatory or patchy, broad zoning is common in many grains (see for instance in PdB-16-01, Fig. 2.3d) even though some appear homogeneous (e.g. Fig. 2.3a). Importantly, core-rim relationships are typically lacking, with very few crystals showing narrow CL-bright or dark rims (< 10 µm-large, see zircon 2 and 3, Fig. 2.3a, or zircon 2, Fig. 2.3b). Secondary textures include healed cracks and fractures (e.g. zircon 3, Fig. 2.3a) and zones of blurred oscillatory zoning (e.g. zircon 7, Fig. 2.3c). We did not specically target any zircon population in the course of the UPb dating sessions in an attempt to be representative of the overall diversity. Apart from two exceptions, all analysed zircon yielded Th/U ratios > 0.08 which supports a magmatic origin for those grains [START_REF] Rubatto | Zircon trace element geochemistry: partitioning with garnet and the link between UPb ages and metamorphism[END_REF][START_REF] Rubatto | Zircon and monazite response to prograde metamorphism in the Reynolds range, central Australia[END_REF].

Zircon Hf isotope compositions

The zircon grains analysed for LuHf isotopes were selected based on the date distribution, trying to capture the diversity of each zircon population. The results are depicted PIL-16-01 Twenty-two 550665 Ma zircon grains show very diverse ε Hf (t), from +8.7 (#3) down to -10.5 (#15). One late Tonian grain has a radiogenic ε Hf (t) of +4.6 (#8).

Early Tonian to late Stenian zircons have also variable Hf isotope signatures with 3 grains displaying ε Hf (t) of -11.9, +1.6 and +10.8 ε-unit (#29, #20 and #22, respectively). Five Paleoproterozoic zircons range between -7.4 (#11) and +4.0 (#19) ε-unit. Three Neoarchean grains are chondritic to suprachondritic, with ε Hf (t) ranging from -0.4 (#2) up to +4.1 (#17).

CHA-16-02 The Hf isotope signature of 32 EdiacaranCryogenian zircons (565720 Ma) is highly scattered with ε Hf (t) ranging from -16.9 (#18) up to +12.7 (#24).

Seven TonianStenian (n=6) and Paleoproterozoic grains (n=1) display chondritic to supra-chondritic ε Hf (t) (between +0.5 and +12.3, #33 and #6, respectively). Three Neoarchean zircons are nearly chondritic with ε Hf (t) ranging between -2.0 (#29) and +1.2 (#21). 2017). The yellow eld depicts the composition of intruding meta-granites from the Velay Orthogneiss Formation (see above). The ε Hf (t) range for the Depleted Mantle reservoir is bracketed by the models of Naeraa et al. (2012) and [START_REF] Grin | Zircon chemistry and magma mixing, SE China: In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes[END_REF]. The dotted arrow represent the isotopic evolution of continental crust (calculated using an average crustal 176 Lu/ 177 Hf ratio of 0.0113). Data for the northern Armorican Massif are from D'Lemos and Brown (1993); [START_REF] Samson | UPb geochronology and SmNd isotopic composition of Proterozoic gneisses, Channel Islands, UK[END_REF] and [START_REF] Samson | UPb geochronology and HfNd isotope compositions of the oldest Neoproterozoic crust within the Cadomian orogen: new evidence for a unique juvenile terrane[END_REF].

PdB

Depositional ages

Field relationships indicate that (meta)granites from the Velay Orthogneiss Formation (VOF) are intrusive within the (meta)sediments (Ledru et al., 1994). [START_REF] Díez Fernández | UPb ages of detrital zircons from the Basal allochthonous units of NW Iberia: Provenance and paleoposition on the northern margin of Gondwana during the Neoproterozoic and Paleozoic[END_REF]Fernández-Suárez et al., 2000;[START_REF] Fernandez-Suarez | The importance of along-margin terrane transport in northern Gondwana: insights from detrital zircon parentage in Neoproterozoic rocks from Iberia and Brittany[END_REF][START_REF] Henderson | Gondwanan basement terranes of the VariscanAppalachian orogen: Baltican, Saharan and West African hafnium isotopic ngerprints in Avalonia, Iberia and the Armorican Terranes[END_REF][START_REF] Linnemann | The Cadomian Orogeny and the opening of the Rheic Ocean: The diacrony of geotectonic processes constrained by LA-ICP-MS UPb zircon dating (Ossa-Morena and Saxo-Thuringian Zones, Iberian and Bohemian Massifs)[END_REF]Orejana et al., 2015;[START_REF] Pereira | The provenance of Late Ediacaran and Early Ordovician siliciclastic rocks in the Southwest Central Iberian Zone: Constraints from detrital zircon data on northern Gondwana margin evolution during the late Neoproterozoic[END_REF], Northern Armorican [START_REF] Ballouard | Origine, évolution et exhumation des leucogranites peralumineux de la chaîne hercynienne armoricaine : implication sur la métallogénie de l'uranium[END_REF][START_REF] Fernandez-Suarez | The importance of along-margin terrane transport in northern Gondwana: insights from detrital zircon parentage in Neoproterozoic rocks from Iberia and Brittany[END_REF][START_REF] Gougeon | Trace Fossils from the Brioverian (EdiacaranFortunian) in Brittany (NW France)[END_REF][START_REF] Miller | UPb geochronological constraints on the timing of plutonism, volcanism, and sedimentation, Jersey, Channel Islands, UK[END_REF][START_REF] Samson | Neoproterozoic palaeogeography of the Cadomia and Avalon terranes: constraints from detrital zircon U-Pb ages[END_REF] and Bohemian [START_REF] Drost | Provenance of Neoproterozoic and early Paleozoic siliciclastic rocks of the Teplá-Barrandian unit (Bohemian Massif ): Evidence from UPb detrital zircon ages[END_REF]Gerdes and Zeh, 2006;[START_REF] Hajná | Time scales and mechanisms of growth of active margins of Gondwana: A model based on detrital zircon ages from the Neoproterozoic to Cambrian Blovice accretionary complex, Bohemian Massif[END_REF]Linnemann et al., 2004;2008;2014;[START_REF] Sláma | Transition from island-arc to passive setting on the continental margin of Gondwana: UPb zircon dating of Neoproterozoic metaconglomerates from the SE margin of the TepláBarrandian Unit, Bohemian Massif[END_REF][START_REF] Sláma | How far did the Cadomian terranes travel from Gondwana during early Palaeozoic? A critical reappraisal based on detrital zircon geochronology[END_REF] massifs documented the predominance of EdiacaranCryogenian grains with additional populations of TonianStenian (7201100 Ma), Paleoproterozoic

(1.82.1 Ga) and Archean (2.4-2.7, sometimes up to 3.45 Ga) age. Typical is the absence of Mesoproterozoic detrital record with a clear gap between 1.2 and 1.6 Ga.

Mixed origin of the detritus Multi-methods studies (encompassing geochemistry, petrography, sedimentology, geochronology) have demonstrated that Ediacaran sediments deposited along the northern margin of Gondwana were of mixed origin: a fraction of the detritus originated from the erosion of the AvalonianCadomian magmatic arc and the rest was supplied by an old Gondwana-derived source [START_REF] Dabard | Zircon typology combined with Sm-Nd whole-rock isotope analysis to study Brioverian sediments from the Armorican Massif[END_REF][START_REF] Denis | Sandstone petrography and geochemistry of late Proterozoic sediments of the Armorican Massif (France) A key to basin development during the Cadomian orogeny[END_REF][START_REF] Drost | Provenance of Neoproterozoic and early Paleozoic siliciclastic rocks of the Teplá-Barrandian unit (Bohemian Massif ): Evidence from UPb detrital zircon ages[END_REF][START_REF] Linnemann | From Cadomian subduction to Early Palaeozoic rifting[END_REF]2008;2014;Nance and Murphy, 1994;Orejana et al., 2015;[START_REF] Pereira | The provenance of Late Ediacaran and Early Ordovician siliciclastic rocks in the Southwest Central Iberian Zone: Constraints from detrital zircon data on northern Gondwana margin evolution during the late Neoproterozoic[END_REF][START_REF] Rabu | The Brioverian (Upper Proterozoic) and the Cadomian orogeny in the Armorican Massif[END_REF].

The proximal source The inferred proximal source, the AvalonianCadomian magmatic arc, crops out in the northern Armorican Massif (France and British Channel Islands, see Ballèvre et al., 2001;Brown, 1995;Chantraine et al., 2001;[START_REF] D'lemos | The Cadomian orogeny in the North Armorican Massif: a brief review[END_REF]Dissler et al., 1988;[START_REF] Dupret | Cadomian geodynamic evolution of the northeastern Armorican Massif (Normandy and Maine)[END_REF][START_REF] Strachan | Neoproterozoic evolution of an active plate margin: North Armorican Massif, France[END_REF]. Even though the rocks today exposed are unlikely to correspond to those eroded at Ediacaran times, they can still provide constraints on the nature, age pattern and isotopic signature of the proximal detritus. In this crust segment, igneous rocks include: (i) late Cryogenian to early Ediacaran calc-alkaline suites comprising basic, intermediate and acid components with radiogenic NdHf isotope signature, taken as evidence for arcback-arc magmatism [START_REF] Auvray | Discussion on tectonothermal chronology of early Cadomian arc development in Guernsey and Sark, Channel Islands[END_REF][START_REF] Brown | Cadomian magmatism in the North Armorican Massif[END_REF]D'Lemos and Brown, 1993;Dallmeyer et al., 1991;Egal et al., 1996;[START_REF] Graviou | Late Precambrian M-type granitoid genesis in the Cadomian belt of NW France[END_REF][START_REF] Guerrot | U-Pb geochronology of the Upper Proterozoic Cadomian orogeny in the northern Armorican Massif, France[END_REF][START_REF] Miller | UPb geochronological constraints on the timing of plutonism, volcanism, and sedimentation, Jersey, Channel Islands, UK[END_REF][START_REF] Nagy | UPb geochronological constraints on the timing of Brioverian sedimentation and regional deformation in the St. Brieuc region of the Neoproterozoic Cadomian orogen, northern France[END_REF][START_REF] Power | Late Precambrian foliated plutonic complexes of the Channel Islands and La Hague: early Cadomian plutonism[END_REF][START_REF] Samson | UPb geochronology and HfNd isotope compositions of the oldest Neoproterozoic crust within the Cadomian orogen: new evidence for a unique juvenile terrane[END_REF]; (ii) late Ediacaran migmatites and peraluminous granitoids (the Mancellian batholith), thought to have been generated during inversion of the back-arc and coeval arccontinent collision [START_REF] Brown | Cadomian magmatism in the North Armorican Massif[END_REF]Brown and D'Lemos, 1991;D'Lemos and Brown, 1993;Egal et al., 1996;[START_REF] Stern | Subduction erosion: Rates, mechanisms, and its role in arc magmatism and the evolution of the continental crust and mantle[END_REF]Peucat, 1986). Paleoproterozoic and Tonian crustal rocks (Icartian and Port Morvan gneisses, respectively) are also documented [START_REF] Calvez | Two billion years old relicts in the Hercynian Belt of Western Europe[END_REF]Egal et al., 1996;[START_REF] Inglis | UPb geochronological constraints on the tectonothermal evolution of the Paleoproterozoic basement of Cadomia, La Hague, NW France[END_REF][START_REF] Samson | UPb geochronology and SmNd isotopic composition of Proterozoic gneisses, Channel Islands, UK[END_REF][START_REF] Samson | UPb geochronology and HfNd isotope compositions of the oldest Neoproterozoic crust within the Cadomian orogen: new evidence for a unique juvenile terrane[END_REF]. They are regarded either as the constituent autochtonous crust on which the Cadomian arcbackarc was formed (Chantraine et al., 2001;Dissler et al., 1988) or as exotic blocks accreted to the arc in the early Ediacaran (Linnemann et al., 2014;[START_REF] Samson | UPb geochronology and HfNd isotope compositions of the oldest Neoproterozoic crust within the Cadomian orogen: new evidence for a unique juvenile terrane[END_REF].

The ε Hf (t) of various Cadomian intrusions are depicted Fig. 2.6 (from Hf isotope studies or recalculated from Nd isotopes based on the relation ε Hf (t) = 1.36 ε N d (t) + 3 determined by Vervoort et al., 1999). Magmas emplaced in the time period 750625 Ma have supra-chondritic, DM-like Hf isotope signatures. A clear shift towards less radiogenic source compositions occurred in the Ediacaran as magmas younger than 625 Ma show a broad range of inferred ε Hf (t) from +5 down to sub-chondritic values of -11. This pattern is similar to that observed in the detrital zircon record of the Velay metasediments (Fig.

2.6).

As a direct consequence of this, the 750555 Ma zircon population encountered in Ediacaran metasediments from the FMC could adequately originate from a proximal Cadomian arc source akin to the northern Armorican Massif.

The case of early TonianStenian and Archean zircons is more problematic. Indeed, there is no rock of that age in the Armorican Massif. Besides, in this area, Paleoproterozoic granitoids have suprachondritic, DM-like, ε Hf (t) which are more elevated than those observed in detrital zircons from the FMC Ediacaran (meta)sediments. These observations require the existence of a dierent, more distal source i.e. the main Gondwana land [START_REF] Drost | Provenance of Neoproterozoic and early Paleozoic siliciclastic rocks of the Teplá-Barrandian unit (Bohemian Massif ): Evidence from UPb detrital zircon ages[END_REF][START_REF] Linnemann | The Cadomian Orogeny and the opening of the Rheic Ocean: The diacrony of geotectonic processes constrained by LA-ICP-MS UPb zircon dating (Ossa-Morena and Saxo-Thuringian Zones, Iberian and Bohemian Massifs)[END_REF]2014;Orejana et al., 2015;[START_REF] Pereira | The provenance of Late Ediacaran and Early Ordovician siliciclastic rocks in the Southwest Central Iberian Zone: Constraints from detrital zircon data on northern Gondwana margin evolution during the late Neoproterozoic[END_REF].

The distal source In the following, we address the nature and origin of the distal source based on the zircon age pattern and isotope signature of both Neoproterozoic detritus [START_REF] Abati | Detrital zircon ages of Neoproterozoic sequences of the Moroccan Anti-Atlas belt[END_REF]2012;[START_REF] Avigad | The detrital zircon UPbHf ngerprint of the northern ArabianNubian Shield as reected by a Late Ediacaran arkosic wedge (Zenim Formation; subsurface Israel)[END_REF][START_REF] Meinhold | Evidence from detrital zircons for recycling of Mesoproterozoic and Neoproterozoic crust recorded in Paleozoic and Mesozoic sandstones of southern Libya[END_REF][START_REF] Morag | 1000580 Ma crustal evolution in the northern Arabian-Nubian Shield revealed by UPbHf of detrital zircons from late Neoproterozoic sediments (Elat area, Israel)[END_REF] and today-exposed igneous rocks [START_REF] Block | Paleoproterozoic juvenile crust formation and stabilisation in the south-eastern West African Craton (Ghana); New insights from UPbHf zircon data and geochemistry[END_REF][START_REF] Eglinger | New insights into the crustal growth of the Paleoproterozoic margin of the Archean Kéména-Man domain, West African craton (Guinea): Implications for gold mineral system[END_REF][START_REF] Küster | Zircon geochronology and Sr, Nd, Pb isotope geochemistry of granitoids from Bayuda Desert and Sabaloka (Sudan): Evidence for a Bayudian event (920900 Ma) preceding the Pan-African orogenic cycle (860590 Ma) at the eastern boundary of the Saharan Metacraton[END_REF][START_REF] Morag | Crustal evolution and recycling in the northern Arabian-Nubian Shield: New perspectives from zircon LuHf and UPb systematics[END_REF]Stern et al., 2010) from several segments of the Gondwana (West African Craton, Saharan Metacraton and Arabian Nubian Shield). We selectively reason on the early TonianStenian, Paleoproterozoic and Neoarchean zircon populations (UPb date > 800 Ma) since those are the only ones for which a distal origin is ensured. Importantly, there is no rock older than Tonian in the Arabian Nubian Shield [START_REF] Morag | Crustal evolution and recycling in the northern Arabian-Nubian Shield: New perspectives from zircon LuHf and UPb systematics[END_REF][START_REF] Stern | Crustal evolution in the East African Orogen: a neodymium isotopic perspective[END_REF] and olderthan800 Ma zircon grains are very scarce [START_REF] Avigad | The detrital zircon UPbHf ngerprint of the northern ArabianNubian Shield as reected by a Late Ediacaran arkosic wedge (Zenim Formation; subsurface Israel)[END_REF][START_REF] Morag | 1000580 Ma crustal evolution in the northern Arabian-Nubian Shield revealed by UPbHf of detrital zircons from late Neoproterozoic sediments (Elat area, Israel)[END_REF]Stern et al., 2010) which discards this area as a potential source region. The West African craton (WAC) exposes Paleoproterozoic and Neoarchean rocks which zircon UPbHf isotope compositions match that of detrital grains from our samples [START_REF] Block | Paleoproterozoic juvenile crust formation and stabilisation in the south-eastern West African Craton (Ghana); New insights from UPbHf zircon data and geochemistry[END_REF]Eglinger et al., 2017 and unpublished data from O. Laurent). However, there is no evidence for early TonianStenian magmatic activity in the WAC [START_REF] Ennih | The boundaries of the West African craton, with special reference to the basement of the Moroccan metacratonic Anti-Atlas belt[END_REF]. Similarly, Ediacaran metasediments deposited in the vicinity of the WAC do feature Paleoproterozoic and Neoarchean zircon populations of adequate Hf isotope signature but lack any early TonianStenian grain [START_REF] Abati | Detrital zircon ages of Neoproterozoic sequences of the Moroccan Anti-Atlas belt[END_REF]2012). This entails that the WAC alone cannot be the distal source of late Ediacaran sediments from the eastern FMC. Little is known about the Saharan Metacraton. Early Tonian igneous rocks with both supra and subchondritic Nd isotope signatures are documented by [START_REF] Küster | Zircon geochronology and Sr, Nd, Pb isotope geochemistry of granitoids from Bayuda Desert and Sabaloka (Sudan): Evidence for a Bayudian event (920900 Ma) preceding the Pan-African orogenic cycle (860590 Ma) at the eastern boundary of the Saharan Metacraton[END_REF]. [START_REF] Meinhold | Evidence from detrital zircons for recycling of Mesoproterozoic and Neoproterozoic crust recorded in Paleozoic and Mesozoic sandstones of southern Libya[END_REF] report the existence of early TonianStenian, Paleoproterozoic and Neoarchean zircon populations in a Neoproterozoic metasediment indicating that this area could have contributed to the detritus that fed the late Ediacaran basins of the FMC. Yet, the lack of Hf isotope data hinders further conclusions. Finally, involvement of crustal materials transported from very distant sources (central and southern Gondwana) may have been possible, as advocated for CambrianOrdovician sediments from northern Gondwana [START_REF] Avigad | Origin of northern Gondwana Cambrian sandstone revealed by detrital zircon SHRIMP dating[END_REF]2012;[START_REF] Altumi | U Pb LAICPMS detrital zircon ages from the Cambrian of Al Qarqaf Arch, central-western Libya: Provenance of the West Gondwanan sand sea at the dawn of the early Palaeozoic[END_REF][START_REF] Kolodner | Provenance of north Gondwana CambrianOrdovician sandstone: UPb SHRIMP dating of detrital zircons from Israel and Jordan[END_REF][START_REF] Linnemann | Sands of West Gondwana: An archive of secular magmatism and plate interactions A case study from the Cambro-Ordovician section of the Tassili Ouan Ahaggar (Algerian Sahara) using UPbLA-ICP-MS detrital zircon ages[END_REF][START_REF] Meinhold | Evidence from detrital zircons for recycling of Mesoproterozoic and Neoproterozoic crust recorded in Paleozoic and Mesozoic sandstones of southern Libya[END_REF]2013;Morag et al., 2011a).

Relative proportions of proximal vs. distal sources A total of 31% of detrital zircon UPb dates are older than 800 Ma (161/519 including the data of Chelle-Michou et al., 2017). Assuming that each eroded rock had a similar zircon content (same "fertility" in the sense of Dickinson, 2008), this yields a minimum estimate of the proportion of detritus derived from the Gondwana mainland, presumably the Saharan Metacraton.

The compilation of [START_REF] Abdelsalam | The Saharan Metacraton[END_REF] demonstrate that CryogenianEdiacaran rocks with DM-like Nd isotope signatures today crop out in this crust segment. Yet, the youngest igneous rock emplacement age obtained by modern dating techniques (UPb on accessory minerals) are 578 ± 15 [START_REF] Sultan | Geochronologic and isotopic evidence for involvement of pre-Pan-African crust in the Nubian Shield, Egypt[END_REF] and even 591 ± 5 Ma when measurements performed by dissolution of multi-grain fractions are excluded. Therefore, metasediments zircon grains younger than 591 Ma most probably originate from the proximal Cadomian arc source. Such grains represent 13% of the dataset (68/519 including the data of Chelle-Michou et al., 2017). As a result, the proportion of detritus originating from distal Gondwana-land sources is bracketed between 3187%. Renement of this rst-order estimate is hampered by our current knowledge of the structure and composition of both the Cadomian arc and the Saharan Metacraton.

Additional observations suggest that the actual value should be closer to 31 than 87%. Indeed, sample PdB-16-01 displays markedly dierent zircon UPb date pattern and Hf isotope signatures compared to other metasediments from the Lower Gneiss Unit, even though their protoliths were presumably deposited in the same basin and time period. This is indicative of brutal changes in the nature of the detritus sources through time.

Such feature is consistent with a detritus originating from catchments submitted to high denudations rates, as would be the case of a continental arc. Consequently, it is very likely that the proximal Cadomian arc did supply an important fraction of the detritus that fed the late Ediacaran basins of Lower Gneiss Unit in the FMC.

Geodynamic inferences

Evolution of the Ediacaran back-arc basin

Several authors argued that late Ediacaran sediments from the north Gondwana margin were deposited in back-arc basins located at the rear of the Cadomian subduction (Fernández-Suárez et al., 2000;Linnemann et al., 2004;2008;2014;Orejana et al., 2015;[START_REF] Pereira | The provenance of Late Ediacaran and Early Ordovician siliciclastic rocks in the Southwest Central Iberian Zone: Constraints from detrital zircon data on northern Gondwana margin evolution during the late Neoproterozoic[END_REF]. This conclusion is based on reconstructed plate motions since the Ediacaran [START_REF] Stampi | The formation of Pangea[END_REF], the present-day location of the Cadomian magmatic arc and the mixed nature of the detritus pinpointing the existence of both a nearby active margin and an evolved mature source by that time (Fig. 2.7).

In the French Massif Central, the pre-Variscan history of the Lower Gneiss Unit features the deposition of detrital sediments in the time period 550590 Ma, i.e the late Ediacaran. The actual thickness of the sedimentary pile is dicult to estimate due to Variscan tectonics but was likely pluri-kilometric. Sediments were intruded by S-type granitic magmas at c. 540545 Ma (see previous section). As a matter of fact, the oldest Figure 2.7: Interpretative geodynamic sketches illustrating the Ediacaran evolution of the crust segment to which the French Massif Central belongs. Inspired from Collins and Richards (2008). See text for discussion. The Riverie meta-tonalites are introduced section 3.5. emplacement age determined for the VOF meta-granites and the age of the youngest zircon population encountered in metasediments are identical within errors (545.9 ± 4.3 and 553.2 ± 5.3 Ma, respectively). This points to a very short time span between sedimentation and crust-derived magmatism. Such situation is typically observed in accretionary orogenic settings where protracted periods of lithospheric extension and associated sedimentation (Fig. 2.7a) are punctuated by contractional events (Fig. 2.7b) leading to crust thickening and followed by anatexis [START_REF] Barker | The 50 Ma granodiorite of the Eastern Gulf of Alaska: melting in an accretionary prism in the forearc[END_REF]Cawood et al., 2009;[START_REF] Collins | Hot orogens, tectonic switching, and creation of continental crust[END_REF]Collins and Richards, 2008;[START_REF] Crook | Fore-arc evolution and continental growth: a general model[END_REF]Kemp et al., 2009;Zurbriggen, 2015). Therefore, geochronological constraints further support a late Ediacaran back-arc location for the crust segment today exposed in the Lower Gneiss Unit of the FMC. S-type granites from the VOF emplaced c. 30 Ma after a thickening episode that aected the northern margin of Gondwana (see section 2.1), dated at 580570 Ma in the North Armorican massif (Ballèvre et al., 2001;[START_REF] Strachan | Neoproterozoic evolution of an active plate margin: North Armorican Massif, France[END_REF]. Contraction in the upper plate would have been promoted by the shallowing of the Cadomian subduction angle [START_REF] Collins | Hot orogens, tectonic switching, and creation of continental crust[END_REF][START_REF] Strachan | Neoproterozoic evolution of an active plate margin: North Armorican Massif, France[END_REF]. The inferred time span (30 Ma) between thickening and magmatism is consistent with that predicted by numerical models (Clark et al., 2011). In this frame, metasediments would have been deposited during the postcontraction relaxation period, between 570 and 550 Ma. Sample PdB-16-01 lacks any detrital zircon younger than c. 590 Ma and its deposition may pre-date the thickening event.

A glimpse of the Cadomian arc evolution? Detrital zircon grains from the Velay metasediments record a marked change in their Hf isotope composition at c. 640 Ma with a drift towards less radiogenic ε Hf (t). Assuming that a signicant proportion of the CryogenianEdiacaran detritus originates from the proximal Cadomian arc (see section 2.2.8), such drift could be explained by the sudden incorporation of an isotopically evolved, old crustal component in youngerthan640 Ma arc magmas. Mixing would have occurred in the source, by addition of crust-derived material in the mantle [START_REF] Nebel | The eect of sediment recycling in subduction zones on the Hf isotope character of new arc crust, Banda arc, Indonesia[END_REF]Plank, 2005;[START_REF] Roberts | Sedimentary recycling in arc magmas: geochemical and UPbHfO constraints on the Mesoproterozoic Suldal Arc, SW Norway[END_REF], or during magma ascent [START_REF] Laumonier | Experimental simulation of magma mixing at high pressure[END_REF]a).

A similar pattern has been described in the Kohistan-Ladakh Batholith of the Himalayan belt by Bouilhol et al. (2013). In this oceanic arc developed above the Tethyan ocean, early granitoids show suprachondritic NdHf isotope signatures which abruptly become subchondritic at 5040 Ma. According to these authors, such change would reect the collision of the India plate with the arc and resulting tapping of a continental crust-derived Indian source in addition to the mantle wedge. Following this, the c. 640 Ma drift observed in the detrital zircon record may be correlated to the accretion of an outboard-sitting exotic crustal terrane to the early Cadomian arc. The c. 2.0 Ga Icartian gneisses of the North Armorican Massif are good candidates because they are today located in the fore-arc region (Linnemann et al., 2014). Besides, those gneisses experienced amphibolite-facies metamorphism and were intruded by a set of leucogranites by 620605 Ma [START_REF] Samson | UPb geochronology and SmNd isotopic composition of Proterozoic gneisses, Channel Islands, UK[END_REF], consistent with an late Cryogenianearly Ediacaran accretion to the arc.

Amphibolites

Introduction

Investigating the origin of meta-igneous rocks is of primary importance in order to decipher the pre-orogenic history of the French Massif Central. In the Lower Gneiss Unit, the presence of igneous metabasites clearly testies for the existence of mantle melting episode(s) before the onset of the Variscan orogeny. Such rocks constitute very scarce massifs with a maximal thickness of 60 m and lateral extension of 23 km [START_REF] Chenevoy | Notice explicative, Carte géol[END_REF]. They are intercalated within meta-greywackes (see Weisbrod, 1970 andNégron, 1979, for the Arc de Fix domain; Yousif, 1980, for the Vivarais and Pilat domains) or enclaved within the Velay granites (e.g. [START_REF] Vitel | Granulite-facies-amphibolite facies transition in basic enclaves of the Velay granite (French Massif Central)[END_REF].

The metabasites were deformed and equilibrated in the amphibolite-to granulitefacies during the Variscan orogeny [START_REF] Vitel | Granulite-facies-amphibolite facies transition in basic enclaves of the Velay granite (French Massif Central)[END_REF]. Most rocks are layered and relic gabbroic textures have been described locally (Lochon, 1985;[START_REF] Yousif | Les amphibolites de la série métamorphique de basse pression du Vivarais occidental et du Mont Pilat : étude lithostratigraphique, pétrographique et géochimique[END_REF]. That being said, identifying the nature of the protolith has proven impossible in most cases. Previous geochemical studies have concluded that the amphibolites have major and trace elements compositions akin to alkali basalts (Briand et al., 1992;Chenevoy et al., 1986;[START_REF] Ouali | Caractérisation géochimique des paléomagmatites de quelques unités lithotectoniques du Massif Central français : Implications géodynamiques[END_REF]Pin and Marini, 1993).

The age of the melting event is unknown and all authors considered the metagreywacke host as indicative of an intra-continental setting for basic magmatism (Briand et al., 1992;Pin and Marini, 1993). They postulated that the LGU amphibolites are CambrianOrdovician in age by analogy with the stratigraphically well-dated volcanosedimentary successions of the lower-grade Parautochtonous Unit and Fold-and-Thrust Belt. There, metabasites transitional between enriched tholeiites and alkali basalts have been described in the Lower Paleozoic strata [START_REF] Alsac | Magmatic characteristics of Ordovician basic volcanism in the Saint-Salvi-de-Carcavès nappe (Tarn, Aveyron, France)[END_REF][START_REF] Lépine | Evidence for early Cambrian alkaline metabasites from the gold-bearing district of Salsigne (Montagne Noire, South Massif Central, France)[END_REF]Marini, 1987;1988;Pouclet et al., in press).

In order to put further constraints on the geochemical signature of the LGU metabasites and ascertain the validity of the CambrianOrdovician age, additional samples have been collected for whole-rock major and trace element determinations and zircon UPb dating. One layered metabasite (MM01) was sampled near the village of Rochepaule and three others (MM02 to 04) at the nearby Fromentoux farm (Fig. 2.1). The outcrops and mineralogy of the metabasites are described in [START_REF] Yousif | Les amphibolites de la série métamorphique de basse pression du Vivarais occidental et du Mont Pilat : étude lithostratigraphique, pétrographique et géochimique[END_REF].

Geochemistry and petrogenesis

The whole-rock major and trace element compositions of the four samples were obtained from the ALS Global rm. A geochemical database was built up from this new dataset and the literature (Briand et al., 1992;[START_REF] Molina | Etude géologique des terrains cristallins de la région de St-Agrève (Ardèche)[END_REF][START_REF] Ouali | Caractérisation géochimique des paléomagmatites de quelques unités lithotectoniques du Massif Central français : Implications géodynamiques[END_REF]Pin and Marini, 1993;Weisbrod, 1970;[START_REF] Yousif | Les amphibolites de la série métamorphique de basse pression du Vivarais occidental et du Mont Pilat : étude lithostratigraphique, pétrographique et géochimique[END_REF]. After screening out altered samples (high LOI and high W index of Ohta and Arai, 2007), a total of 113 analyses were retained (14 of which include trace element compositions). (1980). The fractionation trends for each series are from [START_REF] Debon | Evolution of Mg/Fe ratios in Late Variscan plutonic rocks from the External Crystalline Massifs of the Alps (France, Italy, Switzerland)[END_REF].

In the R 1 R 2 diagram of De La Roche et al. (1980), metabasites plot in a variety of elds, mostly those of ultramac rocks, alkali gabbros, gabbros, monzogabbros and syenogabbros (Fig. 2.8). They dominantly dene an alkalic trend and subordinately a subalkaline trend [START_REF] Debon | Evolution of Mg/Fe ratios in Late Variscan plutonic rocks from the External Crystalline Massifs of the Alps (France, Italy, Switzerland)[END_REF]. All rocks are enriched in Th, LREE, Zr but depleted in HREE with respect to NMORBs and lack any negative Nb anomaly (Fig. 2.9). In the ThNb proxy diagram [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF], they accordingly plot in the mantle array and dominantly cluster around the OIB endmember (Fig. 2.10a). In the TiNb proxy diagram (Fig. 2.10b), LGU metabasites plot within the OIB array and dene a trend between a high Nb/Yb and Th/Yb endmember (Nb/Yb = 10; Th/Yb = 1) and a very high Nb/Yb and Th/Yb endmember (Nb/Yb = 30; Th/Yb = 2.5). The two remaining samples have ratios akin to OIBs (Sun and McDonough, 1989). (Sun and McDonough, 1989) for the metabasites of the Lower Gneiss Unit. The grey eld depicts the composition of samples from the litterature.

These observations conrm that the LGU metabasites mostly dene an alkaline series as already advocated by Briand et al. (1992). The existence of the subalkaline series is questionable. Indeed, in the R 1 R 2 diagram, alkali loss during metamorphism would dis- place sample compositions towards higher R 1 values at constant R 2 . Therefore, samples from the main alkaline population experiencing limited alkali loss unidentied by our screening technique would create an artefactual subalkaline series. Such interpretation is supported by the fact that one sample from the literature (THUE, south of the Velay dome, reported by Pin and Marini, 1993) shows trace element compositions akin to alkali basalts yet is part of the subalkaline trend in the R 1 R 2 diagram.

The enrichment in LREE and more generally HFSE compared to NMORBs is indicative of low melting degrees and/or an enriched mantle source [START_REF] Pearce | Trace element geochemistry of volcanic rocks: Applications for massive sulphide exploration[END_REF]2014).

The depletion in HREE, evidenced by the high TiO 2 /Yb ratios, most likely originates from melting of a mantle source containing residual garnet and hence melting depths in excess of 5070 km [START_REF] Ziberna | Garnet and spinel in fertile and depleted mantle: insights from thermodynamic modelling[END_REF]. The trend in the NbTi proxy diagram could attest to a range of melting degrees at constant pressure [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF]. Altogether, these geochemical proxies support an origin of the LGU metabasite protoliths by melting of a deep asthenospheric source or, alternatively, a lithospheric mantle source that did not previously interact with slab-derived uids.

Zircon UPb dating

In order to constrain the emplacement age of the LGU metabasite protoliths, one sample (MM03) was selected for zircon UPb dating. Zircon grains were separated from the powdered rock at Saint-Etienne University using conventional techniques described section 2.1, subsequently cast into epoxy mounts and polished down to an equatorial grain section. CL-imaging were performed at the Laboratoire Magmas et Volcans in Clermont-Ferrand (France) using a Jeol JSM-5910 SEM. Selected grains were dated by LAICPMS at ETH Zürich (see Appendix B.3.3 for analytical notes and Tables B6 andB9 for standards and samples results).

Zircon textures

Zircon grains from sample MM03 are xenomorphic with rounded to oval shapes and low aspect ratios (between 1 and 2). The grain edges are almost always corroded and irregular (Fig. 2.11). CL-dark cores (see zircon grains 3,5 and 6) are surrounded by poorly luminescent rims displaying sector zoning. Such zoning is locally blurred in domains of

Results

Thirty-eight spots were drilled on 23 grains. Nine analyses are markedly discordant (concordance: 1455%) and will not be discussed further. Eleven measurements performed on zircon domains displaying sector zoning and faint luminescence yielded 206 Pb/ 238 U dates between 318 ± 3 and 304 ± 4 Ma (Fig. 2.12a). A Concordia date of 307.8 ± 3.7 Ma (with a MSWD C+E of 1.5) can be calculated out of the seven youngest, equivalent and concordant analyses. All eleven have markedly low Th/U ratios, always <0.1 and often <0.06 (Fig.

Interpretation

Zircon grains and rims showing UPb dates younger than 318 Ma are poorly luminescent, display sector zoning and have low Th/U. Such features are typically observed in metamorphic zircon (re)crystallized at subsolidus conditions (Corfu et al., 2003;[START_REF] Hoskin | Metamorphic zircon formation by solid-state recrystallization of protolith igneous zircon[END_REF][START_REF] Vavra | Internal morphology, habit and UThPb microanalysis of amphibolite-to-granulite facies zircons: geochronology of the Ivrea Zone (Southern Alps)[END_REF]. Therefore, I interpret the Concordia date of 307.8 ± 3.7 Ma as the age of peak metamorphic conditions. At the regional scale, this age is very well documented and corresponds to: (i) the anatexis of surrounding paragneisses from the Lower Gneiss Unit, dated at 307.4 ± 2.3 Ma (Chelle-Michou et al., 2017); (ii) intrusion of mantle mantle-derived magmas ("vaugnerites") at 307.8 ± 1.6 and 307.3 Ma ± 1.3 Ma (Laurent et al., 2017); (iii) emplacement of the Velay granite at 307.5 Ma ± 2.0 Ma (Chelle-Michou et al., 2017). The CL-dark cores can have two dierent origins. First, they would have crystallized during the emplacement of the igneous protolith. Alternatively, they could correspond to xenocrysts entrained within the basaltic parental magma during emplacement in the continental crust and not fully dissolved. In the rst case, 496 ± 13 Ma would represent the intrusion age of the mac magmatic protolith. Such result is consistent with other studies that reported the existence of similar tholeitic transitional to alkaline basic magmatic rocks of similar age in the low-grade units of the FMC [START_REF] Alsac | Magmatic characteristics of Ordovician basic volcanism in the Saint-Salvi-de-Carcavès nappe (Tarn, Aveyron, France)[END_REF][START_REF] Béziat | Magmatic characteristics of Cambrian volcanites from the western Monts de Lacaune area (Montagne Noire, south Massif Central, France)[END_REF][START_REF] Lépine | Evidence for early Cambrian alkaline metabasites from the gold-bearing district of Salsigne (Montagne Noire, South Massif Central, France)[END_REF]Marini, 1987;1988;Pouclet et al., in press).

Conclusion

The pre-Variscan rocks of the Lower Gneiss Unit mostly record Neoproterozoic events.

Metasediments were deposited between 590 and 545 Ma in a back-arc basin supplied by a detritus originating from both a (present-day)north-sitting magmatic arc and the main Gondwana-land, presumably the Saharan Metacraton. Contractional events probably related to the shallowing of the Cadomian subduction angle resulted in burial and thickening of the thin, anomalously warm back-arc crust, itself dominated by sedimentary lithologies. This resulted in a voluminous magmatic event marked by the c. 540 Ma intrusion of a set of S-type porphyritic and leucogranites, protoliths of the Velay Orthogneiss Formation. Some amphibolite bodies from the LGU may represent Cambrian gabbros/basalts but their scarcity strikingly contrasts with the voluminous Cambrian Ordovician magmatism observed in the LGU of the western FMC Melleton et al. (2010).

Chapter 3 Meta-igneous rocks of the Upper Gneiss Unit in the Monts-du-Lyonnais area

Introduction

In the eastern Massif Central, one of the largest and best exposure of the Upper Gneiss Unit is found in the Monts-du-Lyonnais area, North of the Velay dome. Such domain was thus specically targeted in order to: (i) better characterize the pre-Variscan history of this metamorphic nappe, and ultimately (ii) get insights on the crustal evolution of the terrains today exposed in the Variscan belt.

The Upper Gneiss Unit mostly equilibrated in the amphibolite-facies (Dufour, 1982;Feybesse et al., 1995;Gardien et al., 1990). The volumetrically dominant lithological component corresponds to a set of orthogneisses, referred to as Lyonnais Orthogneiss Formation in the following, but garnetbiotitesillimanite paragneisses are particularly abundant in the southern and western parts of the Monts-du-Lyonnais (Fig. 3.1). Following the studies of [START_REF] Peterlongo | Les terrains cristallins des Monts du Lyonnais (Massif central français)[END_REF] and [START_REF] Forestier | Métamorphisme hercynien et antéhercynien dans le bassin du haut-Allier (Massif Central français)[END_REF], I recognize hereafter the LeptyniteAmphibolite Complex (LAC) as its southern domain (i) comprising a large variety of metamorphic lithologies including leucocratic ne-grained orthogneisses of the Lyonnais Orthogneiss Formation, paragneisses, metabasic rocks, amphibole-bearing gneisses, marbles, garnet-bearing peridotites and (ii) featuring petrological relics of an early high-pressure metamorphic event [START_REF] Blanc | Les roches basiques et ultrabasiques des Monts du Lyonnais. Etude pétrographique, minéralogique et géochimique[END_REF][START_REF] Dufour | Eclogites et granulites dans les Monts du Lyonnais : une évolution métamorphique plurifaciale éohercynienne[END_REF][START_REF] Dufour | Granulite facies metamorphism and retrogressive evolution of the Monts du Lyonnais metabasites (Massif Central, France)[END_REF]Gardien et al., 1990;1988;[START_REF] Lardeaux | Granulites à kornérupine et décompression postorogénique des Monts du Lyonnais (M.C.F.)[END_REF][START_REF] Lasnier | Découverte de roches éclogitiques dans le groupe leptyno-amphibolique des monts du Lyonnais (Massif central français)[END_REF]. Such denition is also that retained by [START_REF] Lasnier | Découverte de roches éclogitiques dans le groupe leptyno-amphibolique des monts du Lyonnais (Massif central français)[END_REF]; [START_REF] Blanc | Les roches basiques et ultrabasiques des Monts du Lyonnais. Etude pétrographique, minéralogique et géochimique[END_REF] and [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF]. The LAC would correspond to a Franciscan-type "subduction mélange" zone created during the northwards subduction of the GaliciaMassif Central ocean (Lardeaux et al., 2014).

In this chapter are typied the nature and origin of the meta-igneous rocks from the Upper Gneiss Unit based on a literature review (mostly unpublished PhD theses from the 80's) and a new set of samples on which were conducted geochemical (major and trace element together with zircon Hf isotope compositions) and geochronological investigations. A geochemical database for metamorphic lithologies was built up from the literature [START_REF] Blanc | Les roches basiques et ultrabasiques des Monts du Lyonnais. Etude pétrographique, minéralogique et géochimique[END_REF][START_REF] Davoine | Sur la géochimie et l'évolution métamorphique des leptynites des monts du Lyon-nais, comparaison avec des leptynites du mont Pilat (Massif central français)[END_REF]Dufour, 1982;[START_REF] Ouali | Caractérisation géochimique des paléomagmatites de quelques unités lithotectoniques du Massif Central français : Implications géodynamiques[END_REF], unpublished analyses (courtesy of J.-F. Moyen, A.-C. Ganzhorn and V. Gardien) and a new dataset from rocks I sampled during my eld survey (n=7). The total number of analyses is 430.

First, the geochemical database was screened to discard metasedimentary lithologies and altered samples. This has been done by a careful consideration of petrological descriptions and by calculation of the W index of Ohta and Arai (2007). The MFW plot of these authors clearly outlines the lithologies that experienced surface weathering (Fig.

3.2)

. They accordingly departs from the igneous trend dened by unaltered meta-igneous rocks. A total of 393 analyses was thus retained for further interpretations. [START_REF] Chiron | Notice explicative, Carte géol[END_REF], Dufour (1982) and Feybesse et al. (1995).

Figure 3.2: MFW plot (Ohta and Arai, 2007) for the Monts-du-Lyonnais metamorphic rocks. The distinction between metasedimentary and meta-igneous lithologies, based on petrological descriptions, is conrmed thereby. Overall, meta-igneous rocks experienced limited weathering.

The Lyonnais Orthogneiss Formation

Petrography

The orthogneisses correspond to amphibolite-facies meta-felsic rocks with the mineralogy Qz + Pg + Kf + Bt ± Grt ± Sill ± Ms + Ap + Ilm + Zrc ± All (mineral abbreviations from [START_REF] Whitney | Abbreviations for names of rock-forming minerals[END_REF]. Besides, hornblende and titanite have been locally described by Dufour (1982). Several facies coexist from a poorly deformed coarse-grained augen gneiss with microcline porphyroblasts to a strongly deformed medium-grained banded gneiss. A ne-grained leucocratic facies (locally called leptynite) is particularly abundant in the LeptyniteAmphibolite Complex. There, the orthogneisses feature meter to decameter-scale boudins of mac to felsic granulite-facies meta-igneous rocks (Dufour, 1982;Duthou et al., 1981).

In some cases (especially for the felsic rocks), it has proven dicult to classify the analysed sample as amphibolite-or granulite-facies for lack of comprehensive petrological description. When this problem occurred, the rock was arbitrarily attributed to the main "orthogneiss" group. Therefore, our database for the main amphibolite-facies orthogneiss unit may still contain a few mislabelled granulite-facies igneous rocks.

Volcanic vs. plutonic origin

Previous investigations on igneous textures and zircon typology have concluded that the augen, banded and at least part of the leucogneisses are former plutonic rocks (Dufour, 1982). Based on faint chemical dierences, Dufour (1982) regarded some leucogneisses from the LeptyniteAmphibolite Complex (the "ortholeptynites") as former volcanites.

Given the petrographic continuity, similar chemistry and whole-rock RbSr ages (see below) of all orthogneisses in the UGU, we will further consider them as meta-plutonic rocks.

The presence of few metasedimentary enclaves within the orthogneisses has been reported by Dufour (1982). At the "Crêt de Py Froid" locality, melanocratic enclaves with igneous textures that strongly recall mac microgranular enclaves (MME) can be observed. Yet, they have never been studied or even mentioned in the literature.

Geochemistry

All orthogneisses (n=157) plot in or very close to the eld of granites in the Na 2 O+K 2 O vs. SiO 2 classication diagram (Middlemost, 1994, Fig. 3.3a). Consistently, most ana- lyses plot in the eld of rhyolite and dacite in the diagram of [START_REF] Winchester | Geochemical discrimination of dierent magma series and their dierenciation products using immobile elements[END_REF], modied by Pearce (1996) (Fig. 3.3b). The consistency between major and trace elementbased classications, together with the low W index (<25) and the fact that orthogneisses still dene pre-Variscan whole-rock RbSr ages (see next section) collectively suggest that the meta-igneous rocks experienced closed-system metamorphism with limited alkali loss.

As a result, they do correspond to meta-granites.

Apart from very few outliers, the meta-granites are potassic (K 2 O: 46 wt.%) and plot in the high-K calc-alkaline to shoshonite elds in the K 2 O vs. SiO 2 diagram (Pecerillo and Taylor, 1976, Fig. 3.3c). They are metaluminous (A/CNK: 0.9 to 1, 10% of the dataset) to mildly peraluminous (A/CNK: 1 to 1.2). In the BA diagram [START_REF] Debon | A chemical-mineralogical classication of common plutonic rocks and associations[END_REF][START_REF] Villaseca | A re-examination of the typology of peraluminous granite types in intracontinental orogenic belts[END_REF], a large number of samples plot in the felsic-peraluminous eld and dene a trend towards lowperaluminous compositions (Figure 3.3d). The normative feldspar diagram [START_REF] O'connor | A classication for Quartz-rich igneous rocks based on feldspar ratios[END_REF] reassesses the meta-granitic nature of the orthogneisses, highlighting their low normative anorthite contents.

Age

The Monts-du-Lyonnais orthogneisses have been the subject of several geochronological investigations summarized Table 3.1. The three youngest dates are equivalent and yield a weighted average emplacement age for the igneous protolith of 469.6 ± 5.7 Ma (2σ, MSWD = 1.6). The signicance of the older date of c. 500 Ma remains uncertain.

The analysed rocks were sampled at the Yzeron quarry which features a great variety of orthogneiss facies which could include older and non-cogenetic rocks.

Isotope geochemistry

As evidenced above, the whole rock RbSr isotope data from Dufour (1982) and the zircon Pb evaporation measurements of Feybesse et al. (1995) yield consistent and identical emplacement ages for the protoliths of the orthogneisses. This is indicative of limited disturbance of the RbSr isotopic system by hydrothermal and/or weathering processes.

As a result, the initial 87 Sr/ 86 Sr (I Sr ) ratio of each sample was recalculated at the em- placement age of 470 Ma.

Figure 3.4 shows the variability of I Sr in the Monts du Lyonnais orthogneisses (data from Dufour, 1982). Most of the data plot along a mixing line between a high-Sr, low I Sr (0.706) endmember and a low-Sr, high I Sr (0.712) endmember.

Figure 3.4: Initial 87 Sr/ 86 Sr (I Sr ) as a function of 1/Sr (in ppm) for the Lyonnais Orthogneiss Formation samples (in grey) and embedded felsic granulite boudins and massifs (in green). Data from Dufour (1982) and Duthou et al. (1981). Fractionation of plagioclase decreases the Sr content of the melt but keeps the I Sr constant.

Petrogenesis

In this section, I attempt to characterize the petrogenesis of the Lyonnais Orthogneiss Formation (LOF) via a comparison with its well-characterized Lower Gneiss Unit counterpart: the Velay Orthogneiss Formation (section 2.1).

Figure 3.3 highlights their overall similar chemical compositions. Both are dominantly composed of K-rich granites including high-SiO 2 (>75%) components. Some subtle dif- ferences can be pinpointed. The LOF granites are statistically less peraluminous than the VOF (average A/CNK of 1.07 against 1.18 for the VOF, Fig. 3.5a). Accordingly, they feature rare amphibole-bearing facies and dene a low-peraluminous trend in the BA diagram while the VOF trends towards high-peraluminous compositions. Moreover, the LOF granites tend to be poorer in P (average of 0.14 vs. 0.24 wt.%, Fig. 3.5b). In the ternary CaOK 2 O/Na 2 OAl 2 O 3 /(FeO t +MgO) diagram (Laurent et al., 2014), the compositions of 85% of the LOF samples overlap with the VOF's and spread within the elds of sediment-and tonalite-derived melts. The remaining 15% depart from the VOF and trend towards the compositions of melts derived from high-K mac lithologies (Fig.

3.5c

). Trace-elements data are available for only four leucogneisses from the LOF. In Whalen's discrimination diagrams [START_REF] Whalen | A-type granites: geochemical characteristics, discrimination and petrogenesis[END_REF], two samples clearly plot in the eld of fractionated I-& S-type granites, within the trend dened by the VOF samples, while two others plot close to the eld of A-type granites (Fig. 3.5d). Lastly, it must be stressed that the LOF likely contains MME whereas such enclaves have never been observed within the VOF.

Collectively, the above-mentioned observations suggest that the petrogenesis of LOF and VOF igneous protoliths slightly diers. Of importance are the negative slope displayed by the LOF in the BA diagram (Fig. 3.3d) together with its lower A/CNK values and P 2 O 5 contents, features generally observed in I-type granitic suites (Villaseca et al., 1998). There is no clear consensus on the origin of such suites as they may form by: (i) mixing between crust-and mantle-derived magmas [START_REF] Metcalfe | Isotopic disequilibrium among commingled hybrid magmas: evidence for a two-stage magma mixing-commingling process in the Mt. Perkins pluton, Arizona[END_REF][START_REF] Zorpi | Magma mingling, zoning and emplacement in calc-alkaline granitoid plutons[END_REF]; (ii) fractionation of mantle-derived magmas (Sisson et al., 2005); (iii) melting of mac rocks [START_REF] Ratajeski | Experimental and geochemical evidence for derivation of the El Capitan Granite, California, by partial melting of hydrous gabbroic lower crust[END_REF]; (iv) melting of crustal lithologies such as meta-volcanic rocks of intermediate composition (andesite to dacite) and immature clastic sediments derived from them [START_REF] Clemens | The enigmatic sources of I-type granites: The peritectic connexion[END_REF].

The fact that the LOF granites share some characteristics with I-type granites can be interpreted in the light of our current knowledge of the eastern FMC pre-Variscan et al., 2014), the elds represent the composition of melts derived from a range of potential sources; (d) discrimination diagrams of [START_REF] Whalen | A-type granites: geochemical characteristics, discrimination and petrogenesis[END_REF]. A stands for A-type granites, OTG for ordinary-type granites (I-, S-and M-types) and FG for fractionated granites. The red eld depicts the compositional range of >95% of the VOF samples.

The amphibolites/eclogites

Field occurrences

Metabasic igneous rocks in the Monts-du-Lyonnais UGU have been studied by Lasnier (1968), [START_REF] Corant | Les éclogites et roches associées des massifs basiques de Saint-Joseph (monts du Lyonnais, Massif central français)[END_REF], [START_REF] Blanc | Les roches basiques et ultrabasiques des Monts du Lyonnais. Etude pétrographique, minéralogique et géochimique[END_REF], [START_REF] Costa | 40 Ar 39 Ar chronology of Variscan tectonometamorphic events in an exhumed crustal nappe: the Monts du Lyonnais complex (Massif Central, France)[END_REF]), Dufour (1982), [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF] and Lardeaux et al. (2001). They crop out in the Leptynite Amphibolite Complex in two dierent settings:

intimately associated with amphibole-bearing gneisses in a 1.5x30 km consistent massif referred to as the "Riverie band". There, metabasites bear amphibolitefacies mineral assemblages and no eclogite-facies rock, even as relic, has ever been described.

as small massifs or boudins stretched within the foliation of garnet and sillimanitebearing paragneisses. Because of poor outcropping conditions, the contact between metabasites and surrounding gneisses is seldom exposed. Zones where abundant metabasite bodies crop out (often as loose blocks in the elds) are labelled "bands" in the literature (i.e. La Gachet, Saint-Joseph, Chagnon bands) even though their petrographic continuity is not ascertained. Unlike the Riverie band, those bodies rather correspond to swarms of boudins than a single massif. There, amphibolitefacies rocks often correspond to retrogressed eclogites.

Geochemical data

Most studies have dealt with the metamorphic evolution of the metabasites and only Coffrant and [START_REF] Corant | Les éclogites et roches associées des massifs basiques de Saint-Joseph (monts du Lyonnais, Massif central français)[END_REF], [START_REF] Blanc | Les roches basiques et ultrabasiques des Monts du Lyonnais. Etude pétrographique, minéralogique et géochimique[END_REF], [START_REF] Ouali | Caractérisation géochimique des paléomagmatites de quelques unités lithotectoniques du Massif Central français : Implications géodynamiques[END_REF] and [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF] investigated their origin and geodynamic signicance. Among them, [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF] and Ouali In the TAS diagram (Middlemost, 1994), metabasic rocks show chemical compositions akin to troctolites, gabbros and gabbroic diorites (Fig. 3.3). In the classication diagram of [START_REF] Winchester | Geochemical discrimination of dierent magma series and their dierenciation products using immobile elements[END_REF] modied by [START_REF] Pearce | Trace element geochemistry of volcanic rocks: Applications for massive sulphide exploration[END_REF], originally designed to classify rocks without relying on uid mobile major elements, they plot within the elds of basalts, andesites/basaltic andesites and alkali basalts. K 2 O contents are variable and range from 0.05 to 1.2 wt.% and sometimes up to 2 wt% (Fig.

). Therefore, they mainly plot in the tholeite and calc-alkaline series elds in Pecerillo's diagram [START_REF] Pecerillo | Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, Northern Turkey[END_REF].

Variability between and within the dierent massifs

The aim of this section is to identify dierent magmatic suites and their potential geographic repartition within the Monts-du-Lyonnais metabasites. We address this point using a set of 61 specimens for which the sampling location is known (from our new dataset and literature data). In the following, all samples are assumed to be close to melt compositions as major and trace element contents are not consistent with a cumulative origin:

Al 2 O 3 <18 wt.%, Sc <60 ppm, Mg# between 40 and 70, Ni <150 ppm, Eu/Eu* between 0.8 and 1.4 (see [START_REF] Pearce | Trace element geochemistry of volcanic rocks: Applications for massive sulphide exploration[END_REF]. We also considered that uid immobile trace element compositions were not substantially modied by high-grade metamorphism. Overall, the dataset can be divided into four subgroups based on the incompatible, immobile element patterns.

Group I Metabasites from Group I are found in both the small bodies (N=7) and the Riverie band (N=4). They are slightly to markedly enriched in LREE with respect to NMORBs and display a negative Nb anomaly (coupled with negative ZrTi anomalies in some cases, Fig. 3.6a and c). Such metabasites are similar to the "LREE-enriched tholeiites" of [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF] but the magnitude of the LREE enrichment can be higher than observed by these authors (notably in the small bodies). In the ThNb proxy diagram (Fig. 3.7a), Group I metabasites plot within the volcanic arc array. In the TiNb proxy diagram (Fig. 3.7b), they scatter in the MORB array between N and EMORBs compositions. In the VTi proxy diagram of [START_REF] Shervais | TiV plots and the petrogenesis of modern and ophiolitic lavas[END_REF], most samples feature high Ti/V ratios (between 20 and 50) apart from two specimens bearing a strongly negative Ti anomaly (LY01a and LY02).

Group II Samples from Group II are typied by their at to LREE-enriched patterns devoid of negative Nb anomaly. Among them, sample CHG (from a small body) is (Sun and McDonough, 1989) for the metabasites of the Upper Gneiss Unit in the Monts-du-Lyonnais area. See text for a discussion on the dierences between each group. The blue elds depict the compositional range of LREE-enriched tholeiites (in a) and "transitional" alkali basalts (in c) identied by [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF] and [START_REF] Ouali | Caractérisation géochimique des paléomagmatites de quelques unités lithotectoniques du Massif Central français : Implications géodynamiques[END_REF] among the small bodies. The red eld shows the compositional range of LREE-enriched tholeiites from the Riverie band [START_REF] Ouali | Caractérisation géochimique des paléomagmatites de quelques unités lithotectoniques du Massif Central français : Implications géodynamiques[END_REF][START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF]. Black line is the composition of the bulk continental crust (Rudnick and Gao, 2003).

(Fig. 3.7a and b). As for Group I rocks, their trace element ratios span between those of N and EMORBs.

Group III Group III gathers specimens showing a steep pattern with enrichment in LREE, depletion in HREE and no Nb anomaly (represented in our new dataset by sample LY08). Rocks from Group III are akin to the "transitional basalts" of [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF].

In the ThNb proxy diagram (Fig. This diagram is based on the change in V redox state when the mantle is uxed by slab-derived uids. V becomes more incompatible and resulting magmas have characteristic high V/Ti ratios. Lower V/Ti ratios would be symptomatic of a more distal position with respect to the slab. Bulk continental crust from Rudnick and Gao (2003). [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF]. This would require that the mantle source interacted at some point of its history with slabderived uids as those are selectively depleted in Nb and Zr [START_REF] Ayers | Solubility of apatite, monazite, zircon, and rutile in supercritical uids with implications for subduction zone geochemistry[END_REF]Hermann and Rubatto, 2009;[START_REF] Spandler | Experimental constraints on element mobility from subducted sediments using high-P synthetic uid/melt inclusions[END_REF][START_REF] Tatsumi | Chemical characteristics of uid phase released from a subducted lithosphere and origin of arc magmas: evidence from high-pressure experiments and natural rocks[END_REF]. Alternatively, contamination of a MORB magma by incompatible element-rich materials bearing a negative Nb anomaly would result in a similar selective Th enrichment. This way, the samples would plot in the volcanic arc array even if they erupted far away from a active margin. The continental crust would constitute an adequate contaminant (Taylor and McLennan, 1985) especially for basalts erupted in attenuated continental settings such as a continent-ocean transitions [START_REF] Pearce | Trace element geochemistry of volcanic rocks: Applications for massive sulphide exploration[END_REF]2014).

Melting depth and signicance of varied Nb/Yb All samples with a negative Nb anomaly bear low TiO 2 /Yb ratios (<0.6) and plot within the MORB array in the TiNb proxy diagram (Fig. 3.7b). This suggests shallow melting depths or high melting degrees (so that garnet would have been exhausted if initially present in the source). The large scatter in Nb/Yb and TiO 2 /Yb ratios can be interpreted in two contrasted ways. The incompatible elements Nb, Zr, Ti and Yb being markedly conservative during subduction, ratios of these elements would be diagnostic of the composition of the mantle source before addition of the slab-derived component [START_REF] Escuder Viruete | Magmatic relationships and ages of Caribbean Island arc tholeiites, boninites and related felsic rocks, Dominican Republic[END_REF][START_REF] Pearce | Tectonic implications of the composition of volcanic arc magmas[END_REF][START_REF] Pearce | Trace element geochemistry of volcanic rocks: Applications for massive sulphide exploration[END_REF]2008). Accordingly, the large scatter observed would indicate that the mantle was intrinsically heterogeneous before metasomatism and melting. Alternatively, considering that the Nb anomaly results from magma contamination, the wide range of Nb/Yb ratios would rather indicate the existence of a variety of contaminants and/or diverse rates of contamination.

Group I The moderate V/Ti ratios (between 20 and 50) displayed by most Group I samples bearing a Nb anomaly (Fig. 3.7c) do not provide self-consistent evidence for uid-assisted mantle melting. Indeed MORB magmas show an identical range of V/Ti ratios [START_REF] Shervais | TiV plots and the petrogenesis of modern and ophiolitic lavas[END_REF] that would keep unaected by crustal contamination because the continental crust has: (i) V/Ti ratios similar to that of the MORBs; (ii) lower V and Ti contents than MORB magmas (Rudnick and Gao, 2003;Taylor and McLennan, 1985).

Consequently, discriminating (at least partly) between source enrichment (driven by slabderived uids) and magma contamination is impossible from trace element compositions alone and would require radiogenic isotope data (SmNd and/or LuHf ).

Group IV Given the very low HFSE contents of Group IV samples (one order of magnitude lower than N-MORBs for Nb), it is very unlikely that trace element compositions were substantially modied by assimilation of crustal rocks during ascent and emplacement. This way, trace element ratios would correspond to those of the mantle source.

Elevated Th/Nb (Fig. 3.7a) point to the presence of a slab-derived component in the mantle source, consistent with high Ti/V ratios (Fig. 3.7c) symptomatic of oxidizing, uid-assisted melting conditions [START_REF] Shervais | TiV plots and the petrogenesis of modern and ophiolitic lavas[END_REF]. Importantly, samples from Group IV show lower Nb/Yb than N-MORB which would attest to strong depletion of their mantle source, probably due to high melting degrees, before re-enrichment by slab-derived uids (Berger et al., 2010a;[START_REF] Escuder Viruete | Magmatic relationships and ages of Caribbean Island arc tholeiites, boninites and related felsic rocks, Dominican Republic[END_REF][START_REF] Marchesi | Migration and accumulation of ultra-depleted subduction-related melts in the Massif du Sud ophiolite (New Caledonia)[END_REF]. Such signature is typically encountered in fore-arc and back-arc basalts [START_REF] Pearce | Immobile element ngerprinting of ophiolites[END_REF]. An intrusion age of 545 Ma is proposed based on the petrological study of the presumably aliated amphibole-bearing gneisses (see section 3.5).

Samples devoid of Nb anomaly: Group II and III Group II and III samples plot in the MORBOIB array of the ThNb proxy diagram and lack evidence for interaction with a crustal component, either at source level (addition of slab-derived uids) or during ascent and emplacement (via contamination by crustal country-rocks). Therefore, they can be interpreted as pristine mantle melts.

Group II specimens have low TiO 2 /Yb ratios (Fig. 3.7b) diagnostic of shallow melt- ing [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF]. Besides, they span in composition between the N and EMORBs endmembers. MORB-like magmas are generally produced via melting of depleted to enriched asthenospheric mantle domains in the spinel peridotite facies [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF].

Such situation is observed in oceanic ridges and continental rifts (provided that crustal contamination during magma ascent is marginal). The age of this magmatism remains unknown.

In contrast Group III rocks display elevated Nb/Yb and Th/Yb ratios and plot close to the OIB reservoir. Such an observation attests to higher melting depths with garnet being present in the residue [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF][START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF] A comment on the potential usefulness of radiogenic isotope data Metasomatized mantle domains are particularly prone to melting due to their lower solidus temperature than normal peridotites (Condamine and Médard, 2014;Gaetani and Grove, 1998;[START_REF] Hirose | Hydrous partial melting of lherzolite at 1 GPa: the eect of H2O on the genesis of basaltic magmas[END_REF][START_REF] Hirose | Melting experiments on lherzolite KLB-1 under hydrous conditions and generation of high-magnesian andesitic melts[END_REF][START_REF] Hirschmann | Dehydration melting of nominally anhydrous mantle: The primacy of partitioning[END_REF]Mallik et al., 2015). Therefore, the time lapse between enrichment and melting is generally too short to generate a substantial deviation in radiogenic isotope compositions in the mantle source, despite the change in Sm/Nd and Lu/Hf ratios caused by the slab-derived uids.

As a result, if the metasomatizing uid dominantly originates from the igneous part of the oceanic crust, the subduction-zone mantle-derived magmas would bear radiogenic isotope compositions akin to that of the oceanic crust (namely ε N d and ε Hf 0). Highly radiogenic Nd and Hf signatures of the metabasites bearing a negative Nb anomaly would thus typify melting of a mantle domain that interacted with slab-derived uids shortly prior to melting.

Conversely, a non-radiogenic signature would be non-specic and could stem from two contrasted scenarios: (i) melting of a mantle metasomatized by slab-derived uids including a substantial contribution from non-radiogenic subducted sediments [START_REF] Hidalgo | Role of crustal and slab components in the Northern Volcanic Zone of the Andes (Ecuador) constrained by SrNdO isotopes[END_REF][START_REF] Nebel | The eect of sediment recycling in subduction zones on the Hf isotope character of new arc crust, Banda arc, Indonesia[END_REF][START_REF] Roberts | Sedimentary recycling in arc magmas: geochemical and UPbHfO constraints on the Mesoproterozoic Suldal Arc, SW Norway[END_REF]; (ii) contamination of a primitive highly radiogenic magma by non-radiogenic continental crust (see for instance Pin and Marini, 1993).

The granulite-facies igneous rocks

Granulite-facies rocks crop out exclusively in the LeptyniteAmphibolite Complex as meter-scale boudins or decameter-scale massifs stretched within the foliation of the LOF leucogneisses (Dufour, 1982;Duthou et al., 1981). They bear typical granulite-facies assemblages [START_REF] Dufour | Granulite facies metamorphism and retrogressive evolution of the Monts du Lyonnais metabasites (Massif Central, France)[END_REF][START_REF] Lardeaux | Granulites à kornérupine et décompression postorogénique des Monts du Lyonnais (M.C.F.)[END_REF]:

Gt + Cpx + Opx + Pg + Rt + Qz for mac rocks.

Qz + Pg + Gt + Kf ± Als ± Opx ± Krn for felsic rocks.

Thermobarometry estimates bracketed the PT conditions of peak metamorphism at 830

± 30 °C for 9 ± 1 kbar [START_REF] Dufour | Granulite facies metamorphism and retrogressive evolution of the Monts du Lyonnais metabasites (Massif Central, France)[END_REF].

Whole-rock major element analyses were obtained by [START_REF] Blanc | Les roches basiques et ultrabasiques des Monts du Lyonnais. Etude pétrographique, minéralogique et géochimique[END_REF], Dufour (1982) and [START_REF] Downes | Isotopic and trace-element arguments for the lower-crustal origin of hercynien granitoids and pre-hercynian orthogneisses, Massif Central (France)[END_REF]. Granulites span over a wide range of compositions (Fig.

3.3a

) from gabbro (N=13) to gabbroic/monzo-diorite (N=4), (qz-) monzonite (N=4) and granite (N=4). Yet, they do not clearly dene a magmatic series in the K 2 O vs. SiO 2 diagram as gabbros plot either in the calc-alkaline or the shoshonite eld and intermediate rocks in the high-K calc-alkaline eld (Fig. 3.3c). Granitic rocks are moderately to very rich in K 2 O (34 or 67 wt.% respectively). In the BA diagram of Debon and Le Fort (1983) modied by [START_REF] Villaseca | A re-examination of the typology of peraluminous granite types in intracontinental orogenic belts[END_REF], granitic rocks plot in the eld of felsic-peraluminous rocks while intermediate samples trend towards metaluminous compositions (Fig. 3.3d).

The felsic granulites have been dated by Duthou et al. (1981) and yielded a whole-rock RbSr isochron age of 497 ± 8 Ma. This age is close to that of the host amphibolitefacies orthogneisses. Initial 87 Sr/ 86 Sr (I Sr ) ratios were accordingly recalculated at the emplacement age of the LOF. With the exception of one sample with very high I Sr , the felsic granulites show a spread in I Sr values similar to that of the host orthogneisses (see Fig. 3.4). Nd isotope compositions were also obtained on two samples by [START_REF] Downes | Isotopic and trace-element arguments for the lower-crustal origin of hercynien granitoids and pre-hercynian orthogneisses, Massif Central (France)[END_REF]. Recalculated ε N d at 470 Ma yield non-radiogenic values of -2 and -5.2, respectively. Altogether, isotopic data suggest that the granitic protoliths of the felsic granulites originated from melting of pre-existing crustal lithologies. Since the felsic granulites display similar age, chemical compositions and isotopic signatures than their host orthogneisses, they probably represent a higher-grade equivalent of the LOF.

As a result, this suggests that the bulk of the orthogneisses from the LAC experienced an early granulite-facies metamorphic event and was subsequently re-equilibrated in the amphibolite facies. Relics of the early metamorphic stage would have only been preserved in low-strain or uid-absent domains (Austrheim, 1986(Austrheim, 1987;;[START_REF] Barrientos | Inltration vs. thermal overprinting of epidote blueschists, Ile de Groix, France[END_REF].

Such reasoning holds true for the basic granulites as well. Their major element compositions are akin to the amphibolites/eclogites from the LAC. [START_REF] Dufour | Eclogites et granulites dans les Monts du Lyonnais : une évolution métamorphique plurifaciale éohercynienne[END_REF] described relict Na-rich augite in equilibrium with garnet within a basic granulite. According to these authors, this would testify for early equilibration in the eclogite-facies.

Therefore, the PT path of the basic rocks would feature an early eclogite-facies stage followed by an increase of temperature leading to equilibration in the granulite-facies and ultimately retromorphosis in the amphibolite-facies. Thus, the basic granulites embedded in the LAC orthogneisses would share the same origin than the amphibolites/eclogites but dier by their equilibration at higher T during peak metamorphism.

The origin of intermediate granulite samples remains uncertain. They may represent metasedimentary residues or dierentiates of the K-rich gabbros which is in better agreement with their low W indexes (Ohta and Arai, 2007). Additional geochemical and geochronological data are needed to constrain their origin and signicance.

3.5

The amphibole-bearing gneisses

Field description

The amphibole-bearing gneisses are mostly found within the "Riverie band" of the LAC and are intimately associated with the above-mentioned amphibolites (Feybesse et al., 1995). They are best exposed in the former Riverie quarry at the place known as "Les

Roches", today a climbing spot (Fig. 3.1). There, amphibole-bearing gneisses display a conspicuous vertical foliation and embed several 20 cm to 3 m-large boudins of amphibolites (Fig. 3.8). Segregation of plagioclasequartzamphibole leucocratic layers or patches with characteristic igneous textures is attributed to limited anatexis of both protoliths. Deformation and partial melting are assumed to be Variscan in age and would result from burial, metamorphism and subsequent exhumation of the LAC rocks. The origin, age and signicance of amphibole-bearing gneisses from the Monts-du-Lyonnais LAC have never been investigated.

Petrography

The amphibole-bearing gneisses feature a primary mineral assemblage consisting of Pg + Qz + Amp ± Bt ± Kfs + Mag + Ap + Zrc + Fe sulphides (Fig. 3.10, abbreviations from [START_REF] Whitney | Abbreviations for names of rock-forming minerals[END_REF]. Plagioclase is andesine or oligoclase (An 25 , representative mineral analyses are presented Table 3.3, see also Appendix Table B2). Amphibole has a magnesio-hornblende composition (Tab. 3.3,Fig. 3.9). Some amphibole grains are altered and converted into a Chl + Cal + Rt assemblage (Fig. 3.10b). Biotite is also frequently chloritized. Table 3.3: Representative mineral analyses of the main phases from samples RV-1 and RV-2. Calculation of the structural formula for calcic amphiboles was based on 23 oxygens and Fe 2+ /Fe 3+ estimated assuming a total of 13 cations. Biotite formula were calculated on a 22 oxygen basis, assuming all iron is ferrous.

Geochemistry

In the TAS diagram (Middlemost, 1994), amphibole-bearing gneisses range in composition between diorites and granites (Fig. 3.3a). Importantly, they tend to dene a tholeiite series in the SiO 2 K 2 O diagram (Pecerillo and Taylor, 1976) and are metalu- minous to slightly peraluminous (Fig. 3.3c and d). In line with their low K 2 O contents, the amphibole-bearing gneisses plot in the eld of tonalites in the normative felsdpar diagram (O'Connor, 1965, Fig. 3.3e). Therefore, they will be referred to as meta-tonalites in the following.

Immobile trace elements patterns normalized to N-MORB basalts shed light on the overall low trace element contents of the meta-tonalites.

Zircon textures

Representative CL-images of zircon grains from both samples are displayed Fig. 3.11.

Zircon grains are idiomorphic to sub-idiomorphic, range in lengths between 70 and 200 µm and often show aspect ratios higher than 2 with well-developed pyramidal tips. Few grains have lower aspect ratios (down to 1.1, see zircons 5 and 6, Fig. [START_REF] Magni | Delamination versus break-off: the fate of continental collision[END_REF]Fig. 3.11b). Yet, both analyses show very low Th/U ratios as typically observed in recrystallized metamorphic zircon [START_REF] Hoskin | Metamorphic zircon formation by solid-state recrystallization of protolith igneous zircon[END_REF][START_REF] Vavra | Internal morphology, habit and UThPb microanalysis of amphibolite-to-granulite facies zircons: geochronology of the Ivrea Zone (Southern Alps)[END_REF]. Moreover, the zircon rim on which analyses a65 and a66

were performed yielded a ε Hf at 361 Ma of 6.6 ± 1.2. This value connects with the main zircon population at c. 545 Ma along an evolutionary trend characterized by a 176 Lu/ 177 Hf ratio of 0.002 (Fig. 3.13), characteristic of zircon grains. Such observation is consistent with a closed-system evolution of the 176 Hf/ 177 Hf ratio. All these lines of evidence support a resetting of the UPb chronometer at c. 360 Ma in this zircon domain, leaving the Hf isotope signature unaected because Hf is a constituent chemical element in zircon [START_REF] Hoskin | Metamorphic zircon formation by solid-state recrystallization of protolith igneous zircon[END_REF]. Discordance of analysis a66 likely originates from coeval common Pb incorporation and subsequent limited Pb loss. Resetting of the UPb chronometer would have been provoked by the metamorphic event developed during the thrusting of the UGU above the LGU, dated in the Lot area at c. 355 Ma (ArAr on biotite, see [START_REF] Costa | Age radiométrique 39 Ar-40 Ar du métamorphisme des séries du Lot et du charriage du groupe leptyno-amphibolique de Marvejols (M.C.F.)[END_REF].

Hf isotope composition of the parental magma The ε Hf (t) variability exhibited by magmatic zircon within a given sample is small (<2 ε Hf -units) and of the same order of magnitude than analytical uncertainties (i.e. ± 1.4 ε Hf -units). This indicate that zircon crystallized from a magma with homogeneous Hf isotope composition. Both samples reveal identical average ε Hf (t) of c. 10.6, taken as representative of that of the magma at the time of crystallization, that falls in the range of expected values for the Depleted Mantle reservoir [START_REF] Grin | Zircon chemistry and magma mixing, SE China: In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes[END_REF]Naeraa et al., 2012).

Petrogenesis

Source of the magmatic suite The low K 2 O (0.11.1 wt.%) and intermediate SiO 2

(6164 wt.%) contents displayed by the meta-tonalites (see Fig. 3.3) indicate that their parental magmas cannot derive from melting of the continental crust which is notably enriched in both these incompatible elements. Similarly, the presence of magnetite suggests that the parental magmas were relatively oxidized which is at odds with an origin by melting of the continental crust as the latter generally produces melts evolving at low f O 2 [START_REF] Ishihara | The magnetite-series and ilmenite-series granitic rocks[END_REF]. The Depleted Mantle-like Hf isotope signature of the parental magma entails that (meta)tonalites could represent: (i) dierentiates of a basaltic magma; or (ii) primary melts of a mac K-poor igneous source extracted from the DM shortly prior to melting. Both hypotheses are in line with the lack of inherited zircon core within both samples. In any case, the radiogenic Hf isotope signature together with the low K 2 O and trace element contents demonstrate that crustal contamination during magma ascent and emplacement was unsignicant.

The Riverie meta-tonalites show major element compositions akin to the Archean TTG (tonalite-trondhjemite-granodiorite) suites for which an origin by melting of mac rocks is proposed [START_REF] Martin | An overview of adakite, tonalitetrondhjemitegranodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution[END_REF]. Whatever the geodynamic setting in which it takes place, melting basic rocks to produce tonalites requires very high temperatures (>920°C, [START_REF] Beard | Dehydration melting and water-saturated melting of basaltic and andesitic greenstones and amphibolites at 1, 3 and 6.9 kb[END_REF]Rapp and Watson, 1995;[START_REF] Rushmer | Partial melting of two amphibolites: contrasting experimental results under uidabsent conditions[END_REF][START_REF] Sen | Dehydration melting of a basaltic composition amphibolite at 1.5 and 2.0 GPa: implications for the origin of adakites[END_REF] or elevated H 2 O concentrations in the source (> 2 wt%, Sisson et al., 2005).

Such UHT conditions are unusual in the Phanerozoic and never reported elsewhere in the basement rocks of the FMC. For instance, in the LGU, the voluminous VOF metagranites originated from melting of pre-existing crustal lithologies at T < 850°C. Besides, eld exposures of the LAC indicate that metabasic rocks are intimately associated with the tonalites and, if genetically related, would more likely represent coeval magmatic products than the source rocks of the tonalite suite. Therefore, the fractionation hypothesis is preferred and further discussed hereafter.

A genetic link between metabasites and tonalites from the LAC? As mentioned above, meta-tonalites have similar LREE, Th and Nb contents than Group I and II amphibolites and are even depleted in HREE (Fig. 3.14). It entails that the latter cannot correspond to the parental basic magmas from which the tonalites were dierentiated because tonalites would have been way more enriched in incompatible trace elements if fractional crystallization had proceeded. Group IV metabasite (samples MG01 and MG04, see section 3.3) are markedly poorer in most incompatible elements than the tonalites and may correspond to the parental magmas. Forward geochemical modelling has been performed to evaluate the feasibility of this hypothesis. First, a set of crystallization experiments for a primary melt which composition matches that of MG1 and MG4 was selected. Was retained the study of [START_REF] Blatter | Crystallization of oxidized, moderately hydrous arc basalt at mid-to lower-crustal pressures: implications for andesite genesis[END_REF] who investigated the phase relationships and residual melt compositions of 01SB-872, a natural basalt from the Cascades magmatic arc. This starting material features SiO 2 , Al 2 O 3 , K 2 O and MgO contents identical to metabasites MG01 and 04 but is lower in CaO and higher in Na 2 O, FeO t and TiO 2 (Table 3. 4).

Equilibration of a 01SB-872 magma at c. 9501000°C and 94 kbar yields melts which compositions adequately match that of the Riverie meta-tonalites even though the experimental melts tend to have overall higher Al 2 O 3 and K 2 O contents. At these PT conditions, melt fractions range from 0.12 to 0.2 [START_REF] Blatter | Crystallization of oxidized, moderately hydrous arc basalt at mid-to lower-crustal pressures: implications for andesite genesis[END_REF]. The phase proportions retrieved by [START_REF] Blatter | Crystallization of oxidized, moderately hydrous arc basalt at mid-to lower-crustal pressures: implications for andesite genesis[END_REF] and a set of partition coecients were used to calculate the trace element composition of the tonalite melts. Ti behaviour was not modelled because fractionation of magnetite can easily account for the negative Ti anomaly of the tonalites as is commonly observed during the dierentiation of basaltic magmas [START_REF] Grove | Fractional crystallization and mantle-melting controls on calc-alkaline dierentiation trends[END_REF]. We only considered clinopyroxene, orthopyroxene, amphibole and plagioclase as trace element hosting phases. We used the minimal and maximal partition For amphibole, we chose the self-consistent dataset of [START_REF] Sisson | Hornblende-melt trace-element partitioning measured by ion microprobe[END_REF]. Nb is from [START_REF] Adam | Proton microprobe determined partitioning of Rb, Sr, Ba, Y, Zr, Nb and Ta between experimentally produced amphiboles and silicate melts with variable F content[END_REF] and Th was set at 0.1. Gd and Tb were not modelled for lack of available partitioning data in the relevant chemical system. Experiments 2364, 2381, 2370 and 2376 from [START_REF] Blatter | Crystallization of oxidized, moderately hydrous arc basalt at mid-to lower-crustal pressures: implications for andesite genesis[END_REF] were selected and yield a range of potential trace element compositions for the dierentiates. The latter match the composition of the tonalites for HREE but fail to reproduce the enrichment in LREE and Th relative to N-MORBs (Fig.

3.14b).

Nature of the parental melt Reverse modelling has been performed to estimate the trace element composition of the parental basaltic magma which fractionation would produce the Riverie meta-tonalites. In each of the four experiments of [START_REF] Blatter | Crystallization of oxidized, moderately hydrous arc basalt at mid-to lower-crustal pressures: implications for andesite genesis[END_REF], the trace element content of the tonalite melt is set to that of the average of the natural samples. The composition of the parental basaltic magma is then retrieved by least-square regression using the observed phase proportions and the above-mentioned set of partition coecients. The four experiments and varied partitioning data yield a range of possible trace element contents for the primary melt. Figure 3.14c shows that the calculated primary basaltic melt would have been depleted relative to N-MORBs in all incompatible elements except for Th. Its immobile trace element pattern normalized to N-MORBS would have featured negative Nb and Zr negative anomalies and a slight enrichment in LREE with respect to HREE. This pattern clearly resembles that of samples MG01 and MG04 but the mantle source of the parental melt would have been less

depleted with respect to N-MORBs.

Conclusion

Given the uncertainties of the developed approach (values of partition coecients, internal errors on trace element concentrations, melt proportions constrained based on a starting material with slightly dierent major element compositions than the investigated samples), it is reasonable to consider that, at rst order, the Riverie metatonalites formed by fractionation of basaltic magmas akin to those at the origin of Group IV metabasites. 3.5.9 Geodynamic setting and other occurrences within the Variscan belt

As discussed in section 3.3, Group IV metabasites show geochemical characteristics typically observed in fore-arc and back-arc basalts [START_REF] Escuder Viruete | Magmatic relationships and ages of Caribbean Island arc tholeiites, boninites and related felsic rocks, Dominican Republic[END_REF][START_REF] Marchesi | Migration and accumulation of ultra-depleted subduction-related melts in the Massif du Sud ophiolite (New Caledonia)[END_REF][START_REF] Pearce | Immobile element ngerprinting of ophiolites[END_REF]. Reconstructed plate motions since the Ediacaran [START_REF] Stampi | The formation of Pangea[END_REF] and the today-location of the Cadomian magmatic arc (to the North of the FMC) support a back-arc rather than a fore-arc setting for the FMC crust segment in the late Ediacaran/early Cambrian (see discussion in Chapter 2). Therefore, both

Group IV metabasites and their aliated meta-tonalites from the Monts-du-Lyonnais Upper Gneiss Unit would testify for a c. 545 Ma mantle melting event in the Cadomian back-arc (Fig. 2.7c).

This situation markedly contrasts with that observed in the Lower Gneiss Unit where late Cadomian magmatism was strictly crust-derived and entails that the Upper and Lower Gneiss Units had dierent geographical locations by that time. The UGU may have had an outboard position with respect to the LGU in which case the thermal regime of its underlying mantle would have been more strongly aected by the Cadomian slab break-o (Nance et al., 2010), up to partial melting (Fig. 2.7c).

Low K 2 O, amphibole-bearing meta-granitoids such as the Riverie meta-tonalites are very scarce within the Variscan belt. [START_REF] Seyler | Magmatologie des séries volcaniques métamorphiques L'exemple des métavolcanites cambro-ordoviciennes, en particulier alcalines, du socle provençal[END_REF] reports the existence of biotite-and amphibole-bearing gneisses in the LAC of the Maures Massif, south-east of the FMC, and referred to as "mixed formation". Their major and trace element contents [START_REF] Innocent | Contribution des isotopes à longue période à la connaissance de l'altération de la croûte continentale[END_REF] clearly resemble that of Riverie meta-tonalites. Besides, isotope dilution UPb dating of zircon fractions yielded an upper intercept date of 548 +15/-7 Ma interpreted as the emplacement age of the igneous protolith [START_REF] Innocent | Datation U-Pb sur zircons à 548 Ma de leptynites des Maures centrales. Signication géodynamique des complexes leptyno-amphibolitiques de l'Europe varisque[END_REF], identical to the ones obtained for the Riverie meta-tonalites. However, the Maures tonalites feature nonradiogenic whole-rock Nd isotope compositions which markedly contrasts with the highly radiogenic Hf isotope signature of their Riverie counterparts. Such observation entails that both rock groups did not derive from melting of a similar mantle source and hinders any attempt to correlate the Maures massif with the eastern part of the FMC.

Conclusion

The geochemical investigations conducted on the meta-igneous units of the Monts-du-Lyonnais UGU highlight the existence of three main magmatic suites: (i) basaltic mag- have originally been identied based on their contrasted tectonic-metamorphic evolutions during the Variscan orogeny (Ledru et al., 1989). These include the existence/absence of an early high-pressure event (recorded by eclogite-facies rocks) and varied temperatures/pressures reached at peak metamorphism. As outlined in the introductory section, examination of the three largest and best studied exposures of the French Massif Central (the Velay, Lot/Rouergue and Limousin areas) reveal that the structural relationships between the UGU, LGU and PAU units dier from a domain to another. In this section, we review the lithological composition and pre-orogenic magmatic histories of each nappe from the three domains in order to evaluate: (i) their lateral continuity in terms of pre-Variscan history; (ii) the potential role played by inherited, pre-orogenic features on the Variscan evolution.

Data compilation All metamorphic units from the FMC are typically composed of both metasedimentary and meta-igneous lithologies. Figure 4.1 is a compilation of emplacement ages obtained on meta-igneous rocks from the dierent nappes. The UGU and PAU from the Limousin are not considered because the available geochronological dataset is very limited and hampers to draw any large-scale picture. The depositional age of the (meta)sediments for each unit is estimated based on (i) paleontological data (Fournier-Vinas and Debat, 1970;Guérangé-Lozes and Burg, 1990) ; (ii) eld relationships, when already dated (meta)plutonic bodies clearly feature intrusive contacts with adjacent (meta)sediments; (iii) dating of interlayered volcanics (Faure et al., 2009;Lescuyer and Cocherie, 1992); (iv) detrital zircon studies (Melleton et al., 2010). Results of this compilation are summarized on a structural sketch for each of the three investigated domains (Fig. 4.2).

Upper vs. Lower Gneiss Units East of the Sillon Houiller fault, examination of the pre-Variscan magmatic record (Fig. 4.1) reveals contrasting age patterns between the UGU and the LGU. Indeed, the LGU was almost exclusively aected by Cadomian magmatism and lacks any major Ordovician imprint (Fig. 4.3). The opposite situation is displayed by the UGU which dominantly records the Ordovician magmatic event (Fig. 4.3). Therefore, in this part of the FMC, a direct linkage exists between the pre-Variscan history of the crust segment and its evolution during the Variscan orogeny. Such conclusion might only been altered in the Rouergue area where most igneous rocks from the LGU have been dated with the UPb isotope dilution method on zircon multi-grain Figure 4.1: Compilation of available intrusion ages for pre-Variscan plutonic and volcanic rocks in the French Massif Central. In this compilation, the PAU of the Rouergue, Lot and Velay areas also includes the low-grade "Fold-and-Thrust Belt" and the Saint-Sernin-sur-Rance nappe of Faure et al. (2009) and thus refers to all low-grade metamorphic units a similar structural position. fractions (Fig. 4.1). In this case, dissolution of grains with inherited cores may yield erroneous older emplacement ages. That being said, based on the well-documented case of the Velay dome, it is very likely that the contrasted age patterns of the UGU and

LGU reect their dierent paleogeographical positions by the Ordovician. Accordingly, both units experienced contrasted metamorphic evolutions at Variscan times. This also supports an allochtonous origin for the UGU, independently postulated based on its metamorphic record [START_REF] Burg | A cross section through the French Massif Central and the scope of its Variscan geodynamic evolution[END_REF][START_REF] Burg | Inverted metamorphic zonation and large scale thrusting in the Variscan belt: An example in the French Massif central[END_REF].

The Sillon Houiller East/West dichotomy The LGU in the Limousin area records a protracted CambrianOrdovician magmatic event (Fig. 4.1) which age pattern does not match that of its counterpart East of the Sillon Houiller but rather resembles the UGU from the same area (Fig. 4.3). This entails that the LGUs experienced contrasted pre-Variscan evolutions on both sides of the Sillon Houiller. Such structure is often described as a transfer fault nucleated during Variscan orogenic collapse in response to variable extension rates (Burg et al., 1994;[START_REF] Lapierre | Potassic late orogenic Stephanian volcanism in the Southwest French Massif central (Decazeville, Figeac, Lacapelle-Marival basins): an example for mantle metasomatism along strike-slip faults?[END_REF]). Yet, it may also correspond to a lithospheric-scale structure that demarcates two crust segments having contrasted pre-Variscan histories. Alternatively, the discrepancy in the LGUs pre-Variscan magmatic record may stem from the existence of a distinct stack of nappes on both sides of the Sillon Houiller. Such hypothesis is backed up by the fact that the relics of eclogitefacies metamorphism are observed in the LGU only West of the Sillon Houiller (see introductory section). [START_REF] Dubuisson | Multiple Variscan nappes in Limousin, western Massif Central, France: geophysical constraints to the geological model and geodynamic implications[END_REF] and [START_REF] Berger | Origin and tectonic signicance of corundum-kyanite-sapphirine amphibolites from the Variscan French Massif Central[END_REF] provide further constraints to this point by highlighting that the Limousin LGU features additional lithological components including an ophiolitic unit, underlying micaschists and HP-UHP metabasites. They even propose a dierent nappe subdivision scheme, based on that observed in the Armorican Massif [START_REF] Ballèvre | Palaeozoic history of the Armorican Massif: Models for the tectonic evolution of the suture zones[END_REF]. As a result, the age compilation presented in this study together with recent metamorphic investigations suggest that the nappes cannot be correlated on both sides of the Sillon Houiller. Signicance of the Parautochtonous Units In the easternmost part of the FMC (Velay area), the PAU corresponds to the so-called "Cévennes" and "Vigan" schists, a former Paleozoic sedimentary sequence (see for instance Faure et al., 2009, Fig. 4.1).

Consequently, the PAU (meta)sediments likely represent the (paleo)cover of the LGU Precambrian lithologies (Velay Orthogneiss Formation and associated metasediments, see Chapter 1) because of their: (i) structural position overlying the LGU (Bouilhol et al., 2006;[START_REF] Faure | Tectonic evolution of the Cévennes para-autochtonous domain of the Hercynian French Massif Central and its bearing on ore deposits formation[END_REF], (ii) low metamorphic grade symptomatic of limited burial and transport [START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF].

A

General overview

The geodynamic evolution of the North Gondwana margin at CambrianOrdovician times has been very much debated in the past 20 years and contrasted scenarios have been proposed:

the pre-Mesozoic basement of the eastern Alps would feature relics of an Ordovician accretionary orogen (Zurbriggen, 2015). Conversely, in the western Alps, the coeval Chamrousse ophiolite [START_REF] Ménot | 496 My age of plagiogranites in the Chamrousse ophiolite complex (external crystalline massifs in the French Alps): evidence of a Lower Paleozoic oceanization[END_REF][START_REF] Pin | A SmNd isotopic study of 500 Ma old oceanic crust in the Variscan belt of Western Europe: the Chamrousse ophiolite complex, Western Alps (France)[END_REF] would correspond to an oceanic domain formed in a back-arc setting above the SE-directed subduction of the Iapetus ocean [START_REF] Guillot | Paleozoic evolution of the External Crystalline Massifs of the Western Alps[END_REF].

In the Iberian massif, a continental arc setting has been proposed by [START_REF] Valverde-Vaquero | New UPb ages for Early Ordovician magmatism in Central Spain[END_REF] and would have been followed by back-arc rifting [START_REF] Abati | Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain[END_REF][START_REF] Díez Fernández | UPb ages of detrital zircons from the Basal allochthonous units of NW Iberia: Provenance and paleoposition on the northern margin of Gondwana during the Neoproterozoic and Paleozoic[END_REF]. Similarly, Villaseca et al. (2016) argue for a at subduction and thickening on a still ongoing Cadomian belt followed by passive margin development. On the other hand, [START_REF] Nance | The Rheic Ocean: Origin, Evolution, and Signicance[END_REF], [START_REF] Murphy | Probing crustal and mantle lithosphere origin through Ordovician volcanic rocks along the Iberian passive margin of Gondwana[END_REF] and Díez [START_REF] Montes | Role of the Ollo de Sapo massive felsic volcanism of NW Iberia in the Early Ordovician dynamics of northern Gondwana[END_REF] advocate a continental rifting event away from any subduction zone inuence.

in the Armorican Massif, a similar opposition between continental arc [START_REF] Jégouzo | Caractérisation et signication géodynamique des orthogneiss calco-alcalins d'âge ordovicien de Bretagne méridionale[END_REF] and subduction-unrelated continental rifting [START_REF] Ballèvre | Geochronology and geochemistry of Ordovician felsic volcanism in the Southern Armorican Massif (Variscan belt, France): Implications for the breakup of Gondwana[END_REF] is observed.

in the Maures massif, rifting would have been provoked by a mantle plume [START_REF] Briand | Felsic (A-type)basic (plume-induced) Early Palaeozoic bimodal magmatism in the Maures Massif (southeastern France)[END_REF].

Geological information from the Massif Central

Sedimentology The Variscan low-grade metamorphic units (Parautochtonous Units and Fold-and-Thrust Belt) preserve an excellent sedimentological record throughout the Lower Paleozoic.

In the northern and southern anks of the Montagne Noire, the carbonate-bearing early Cambrian to early Ordovician strata would correspond to inner shelf sediments [START_REF] Álvaro | Nouveau découpage stratigraphique des séries cambriennes des nappes de Pardailhan et du Minervois (versant sud de la Montagne Noire, France)[END_REF]2003;2014;Guérangé-Lozes and Burg, 1990;[START_REF] Lescuyer | Action concertée : les minéralisations PbZn de Montagne Noire et leurs relations avec leux encaissant cambrien carbonaté sur quelques exemples du versant nord (La Rabasse, Brusque, Les Comtes) et du versant sud (Bibaud, Tête Rousse)[END_REF]. Of importance are the stratigraphic gap between the Lower and Upper Ordovician and associated Sardic unconformity presumed to reect uplift and subsequent erosion (Javier Álvaro et al., 2016). Inlling of the negative paleo-reliefs would have started in the Upper Ordovician (Javier Álvaro et al., 2016). The sedimentological record together with the lack of folding and limited uplift (<2 km) during the Sardic event collectively point to an extensional setting in the CambrianOrdovician period [START_REF] Álvaro | Late Ordovician (post-Sardic) rifting branches in the North Gondwanan Montagne Noire and Mouthoumet massifs of southern France[END_REF]Guérangé-Lozes and Burg, 1990).

Magmatic activity Continuous magmatic activity is recorded throughout the Lower Paleozoic as evidenced by: (i) volcanic complexes in the low-grade Variscan parautochton units [START_REF] Alsac | Magmatic characteristics of Ordovician basic volcanism in the Saint-Salvi-de-Carcavès nappe (Tarn, Aveyron, France)[END_REF][START_REF] Álvaro | Stratigraphic review of the Cambrian-Lower Ordovician volcanosedimentary complexes from the northern Montagne Noire[END_REF][START_REF] Béziat | Magmatic characteristics of Cambrian volcanites from the western Monts de Lacaune area (Montagne Noire, south Massif Central, France)[END_REF]1993;[START_REF] Lépine | Evidence for early Cambrian alkaline metabasites from the gold-bearing district of Salsigne (Montagne Noire, South Massif Central, France)[END_REF]Marini, 1987;1988;Pouclet et al., in press); (ii) orthogneisses in the high-grade

Variscan units (see Alexandre, 2007, Melleton et al., 2010 and the previous chapters);

(iii) magmatic zircon grains of that age present as detritus in younger Devonian to Permian sedimentary formations [START_REF] Lin | Detrital zircon age distribution from Devonian and Carboniferous sandstone in the Southern Variscan Fold-and-Thrust belt (Montagne Noire, French Massif Central), and their bearings on the Variscan belt evolution[END_REF][START_REF] Pfeifer | Permian exhumation of the Montagne Noire core complex recorded in the Graissessac-Lodève Basin[END_REF]. Magmatic products encompass basic to felsic rocks.

Geotectonic discrimination Metabasic rocks cropping out in high-grade metamorphic units of the French Massif Central have been the subject of numerous geochemical investigations in order to (i) characterize their mantle source(s) and (ii) reconstruct the geodynamic setting in which magmatism took place (Berger et al., 2010a;[START_REF] Bodinier | Etude géochimique du massif basique et ultrabasique de Najac (Aveyron). Conséquences géotectoniques[END_REF][START_REF] Bodinier | Reliques d'un bassin d'arrière-arc subducté, puis obducté dans la région de Marvejols (Massif central)[END_REF][START_REF] Briand | Les métabasites de la série de Marvejols (Massif central) : témoins d'un magmatisme tholéïtique d'arrière-arc cambro-ordovicien[END_REF][START_REF] Briand | Diversité géochimique des métabasites des groupes leptyno-amphiboliques du Rouergue et de Marvejols (Massif central). Origine et implications[END_REF]1991;1992;1995;[START_REF] Downes | Isotope and traceelement heterogeneities in high-grade basic metamorphic rocks of Marvejols: Tectonic implications for the Hercynian suture zone of the French Massif Central[END_REF][START_REF] Giraud | Geochemistry of leptyno-amphibolite complex from Haut-Allier (French Massif Central)[END_REF][START_REF] Piboule | Utilisation de l'analyse factorielle discriminante pour la reconnaissance de la nature des magmas parents des amphibolites. Application à quelques métabasites du Rouergue et du Limousin (Massif Central français)[END_REF]1979;[START_REF] Piboule | Geochemistry of eclogites and associated rocks of the southeastern area of the French Massif Central: origin of the protoliths[END_REF]Pin and Marini, 1993). Those studies yielded contrasting results and point to melting of a range of sources from a deep/enriched to shallow/depleted asthenospheric mantle, sometimes bearing a strong "subduction component" (Berger et al., 2010a;[START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF][START_REF] Downes | Isotope and traceelement heterogeneities in high-grade basic metamorphic rocks of Marvejols: Tectonic implications for the Hercynian suture zone of the French Massif Central[END_REF]Pin and Marini, 1993). Similarly, a varied set of Cambrian

Ordovician geodynamic scenarios has been inferred from them and include:

the existence of an intra-oceanic supra-subduction zone, the metabasites being produced in a island-arc or back-arc setting (Berger et al., 2010a).

a back-arc basin [START_REF] Downes | Isotope and traceelement heterogeneities in high-grade basic metamorphic rocks of Marvejols: Tectonic implications for the Hercynian suture zone of the French Massif Central[END_REF][START_REF] Giraud | Geochemistry of leptyno-amphibolite complex from Haut-Allier (French Massif Central)[END_REF], probably developed on stretched continental crust [START_REF] Briand | Les métabasites de la série de Marvejols (Massif central) : témoins d'un magmatisme tholéïtique d'arrière-arc cambro-ordovicien[END_REF][START_REF] Briand | Geochemistry and tectonic implications of two Ordovician bimodal igneous complexes, southern French Massif Central[END_REF]1995;[START_REF] Piboule | Geochemistry of eclogites and associated rocks of the southeastern area of the French Massif Central: origin of the protoliths[END_REF].

a continental rift away from the inuence of a subduction zone [START_REF] Chèvremont | Notice explicative, Carte géol[END_REF]Pin and Marini, 1993).

Inferences from the metabasite geochemistry

Rationale All geochemical studies of the metabasites cropping out in high-grade units have been conducted at a regional scale, focusing on a specic domain or formation. In this section, I put further constraints on their mantle source(s) and their geodynamic signicance based on the examination of the metabasite geochemical record at a larger scale, that of the whole FMC.

Material and methods In this scope, a geochemical database was built based on a literature survey and the newly obtained results presented sections 2.3 and 3.3. It gathers amphibolite-, eclogite-and granulite-facies basic rocks for which the full set of major and trace element compositions is available. In order to discard fractionates, cumulates and altered samples, the same procedure as explained section 2.3 and 3.3 was applied. We retained 21 samples from the Haut-Allier area [START_REF] Giraud | Geochemistry of leptyno-amphibolite complex from Haut-Allier (French Massif Central)[END_REF], 41 from the Montsdu-Lyonnais (data from [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF]Ouali, 1993 and this study), 36 from the Lot area [START_REF] Briand | Geochemistry and tectonic implications of two Ordovician bimodal igneous complexes, southern French Massif Central[END_REF][START_REF] Downes | Isotope and traceelement heterogeneities in high-grade basic metamorphic rocks of Marvejols: Tectonic implications for the Hercynian suture zone of the French Massif Central[END_REF]Pin and Marini, 1993) and 16 from the Velay dome (data from Briand et al., 1992;Pin and Marini, 1993 and this study).

We also selected 17 samples from several massifs of the Limousin domain, in the western Massif Central (Berger et al., 2010a;[START_REF] Chèvremont | Notice explicative, Carte géol[END_REF], which yields a total of 131 metabasites. Isotopic data are available for 21 of them. A selected set of geochemical diagrams based on immobile trace element ratios is used to discuss the petrogenesis of the metabasic rocks, assumed to represent basaltic melt compositions. This diagrams are those of [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF] and [START_REF] Shervais | TiV plots and the petrogenesis of modern and ophiolitic lavas[END_REF] and have already been presented sections 2.3 and 3.3.

Summary of geochronological results Few geochronological investigations have been performed on the metabasites from our database. In the Lot area, zircon fractions extracted from a meta-gabbro yielded a TIMS UPb age of 484 ± 7 Ma (Pin and Lancelot, 1982) interpreted as the emplacement age of the magmatic protolith. In the Rouergue area, a norite and an eclogite (not represented in our database) have been dated by stepwise Pb-evaporation of single zircon grains and isotope dilution of zircon fractions (Paquette et al., 1995). Both methods yielded identical results and an emplacement age of c. 480 Ma is inferred for the protolith of both rocks. In the Limousin area, Berger et al. (2010a) obtained an emplacement age of 473 ± 6 Ma for the protolith of an eclogite by LAICPMS dating of zircon cores. Identical ages obtained by the same method are reported by Chelle-Michou et al. (2017) for amphibolite-facies metabasic to intermediate rocks from the Doux massif (also not represented in our database). Finally, few samples from the Monts-du-Lyonnais area are probably as old as 545 Ma (see discussion section 3.5). All these lines of evidence suggest that the metabasites correspond to magmatic rocks formed during a late Ediacaran to early Ordovician magmatic episode (Berger et al., 2010a;Chelle-Michou et al., 2017;Paquette et al., 1995;Pin, 1979;Pin and Lancelot, 1982).

Trace element geochemistry to lithospheric mantle source [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF].

In the TiNb proxy diagram (Fig. 4.4b), 1/4 of the samples show high TiO 2 ratios and consistently plot in the OIB array. They trend from N/EMORB towards OIB compositions which attest to increasing amounts of residual garnet and hence melting of a deeper mantle source (see discussion in [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF].

Samples with high Th/Nb ratios and suspected to have originated from a mantle source that interacted with slab-derived uids are plotted in the VTi proxy diagram (Fig. 4.4c). Some display low Ti/V ratios (close to 10) which are indicative of melting under notably oxidizing conditions [START_REF] Shervais | TiV plots and the petrogenesis of modern and ophiolitic lavas[END_REF]. Such low ratios cannot originate from contamination of the magmas by the continental crust during ascent because the latter has higher Ti/V (between 20 and 50, see Taylor and McLennan, 1985). If the uidenriched mantle source hypothesis is correct, then the wide range of Ti/V ratios (from 10 to 60) attests to melting under varied oxygen fugacities conditions. In supra-subduction zone ophiolites, such range is interpreted in terms of distance to the subducting slab (the main uid source) with low Ti/V magmas being produced in the arc and those with moderate to high Ti/V in a back-arc setting [START_REF] Pearce | Immobile element ngerprinting of ophiolites[END_REF]. (2008). The isotopic composition of metasomatizing uids derived from the oceanic igneous crust is assumed to be close to that of the Depleted Mantle (value from [START_REF] Liew | Precambrian crustal components, plutonic associations, plate environment of the Hercynian Fold Belt of central Europe: Indications from a Nd and Sr isotopic study[END_REF]. Red curve: results of binary mixing model of a basaltic melt PB (Nd, Th and Nb contents set as average of N and EMORBs, from Sun and McDonough, 1989; ε N d (t) of +7) assimilating upper and lower continental crust (UCC and LCC, Nd, Th and Nb contents from Rudnick and Gao, 2003; ε N d (t) of -5, average of the FMC crust, from Turpin et al., 1990;[START_REF] Simien | Nd isotopes in the stratigraphic record of the Montagne Noire (French Massif Central): No signicant Paleozoic juvenile inputs, and pre-Hercynian paleogeography[END_REF][START_REF] Downes | Isotopic and trace-element arguments for the lower-crustal origin of hercynien granitoids and pre-hercynian orthogneisses, Massif Central (France)[END_REF]Pin andDuthou, 1990 andWilliamson et al., 1992). Blue curve: results of mass-balance, binary mixing models between the local mantle LM (ε N d (t)=+7, corresponding to that of the most radiogenic metabasite; Nd, Th and Nb contents from Workman and Hart, 2005) and (i) the GLOSS (Global Subducting Sediment, Plank and Langmuir, 1998), (ii) the LCC (Rudnick and Gao, 2003), both assumed to show an average ε N d (t) of -5 (see above). Percentages represent the proportion of UCC/LCC/GLOSS in the respective mixtures.

Nd isotope data

Samples from subset A have low Th/Nb ratios and originated from melting of a mantle source that did not interact at any time with slab-derived uids [START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF].

As a result, the ε N d (t) of c. +6 can be taken as representative of that of the regional mantle devoid of slab-derived component. On the other hand, samples from subset B and C display high Th/Nb ratios which would result from: (i) the presence of a slab-derived component in the mantle source; or (ii) contamination by the continental crust during ascent. In the case of subset B samples, the highly radiogenic (between +6 and +9) ε N d (t) discards the continental crust as a contaminant since this would have driven the ε N d (t) towards non-radiogenic values. Therefore, the mantle source of samples from subset B did interact with slab-derived uids shortly prior to melting. A similar conclusion was drawn by Berger et al. (2010a) using the Limousin dataset.

Deciphering the case of subset C samples has proven more dicult. Pin and Marini (1993) interpreted their slightly radiogenic to non-radiogenic Nd isotope composition as reecting crustal contamination during magma ascent/emplacement. Yet, binary mixing models of continental crust assimilation indicate that incorporation of more than 20%

(and probably 40%) of crustal material is required to account for the non-radiogenic values of subset C metabasites (Fig. 4.4d). Such substantial contamination is hampered by thermodynamic considerations [START_REF] Glazner | Thermal limitations on incorporation of wall rock into magma[END_REF] and the fact that resulting contaminated magmas would certainly not be mac anymore.

As samples from subset B provide unequivocal evidence for interaction of the mantle with slab-derived uids, an alternative to the model of Pin and Marini (1993) would be to consider that rocks from subset C originated from melting of a mantle metasomatized by sediment-derived uids (or melts). Such situation is observed in arc settings where the Nd isotope composition of subducting sediments is transferred to the overlying mantle [START_REF] Hidalgo | Role of crustal and slab components in the Northern Volcanic Zone of the Andes (Ecuador) constrained by SrNdO isotopes[END_REF]. Similar conclusions have been drawn for Hf isotopes (see [START_REF] Nebel | The eect of sediment recycling in subduction zones on the Hf isotope character of new arc crust, Banda arc, Indonesia[END_REF]Roberts et al., 2013 and section 5.3). In this case, binary mixing models show that the signature of subset C samples could accordingly stem from the incorporation of 5% percent of crustal material in their mantle source (Fig. 4.4d).

Discussion

The set of geochemical proxies and isotopic data presented above unambiguously points to markedly varied melting degrees, redox conditions, depths of melting (presence of residual garnet) and source compositions (including the existence of mantle domains that interacted with slab-derived uids) for the magmatism at the origin of the metabasite protoliths. Such diversity is observed at the scale of the whole Massif Central and to a lesser extent within each massif (see [START_REF] Downes | Isotope and traceelement heterogeneities in high-grade basic metamorphic rocks of Marvejols: Tectonic implications for the Hercynian suture zone of the French Massif Central[END_REF][START_REF] Briand | Geochemistry and tectonic implications of two Ordovician bimodal igneous complexes, southern French Massif Central[END_REF]1995 and section 2.3).

The variable trace element ratios and isotope compositions are best explained by melting of a very heterogeneous mantle source that would readily correspond to the subcontinental lithospheric mantle present beneath the FMC crust segment during the CambrianOrdovician. Today inaccessible, the chemical properties of this reservoir can only be inferred from the regional geological context and the study of mantle xenoliths sampled by the Cenozoic volcanoes of the eastern FMC [START_REF] Downes | Mantle domains in the lithosphere beneath the French Massif Central: trace element and isotopic evidence from mantle clinopyroxenes[END_REF][START_REF] Hutchison | Chemical variation among French ultramac xenoliths evidence for a heterogeneous upper mantle[END_REF][START_REF] Lenoir | Contrasting lithospheric mantle domains beneath the Massif Central (France) revealed by geochemistry of peridotite xenoliths[END_REF]. Such peridotites provide critical information on the origin and evolution of the SCLM. First, clinopyroxene Nd isotope data show that the SCLM do not record any geological event older than 0.6 Ma (Wittig et al., 2007). Second, sulde

Re/Os geochronology demonstrates that the oldest melt depletion event experienced by the SCLM would be c. 0.9 Ga-old [START_REF] Harvey | Unravelling the eects of melt depletion and secondary inltration on mantle ReOs isotopes beneath the French Massif Central[END_REF]. Altogether, these results indicate that the SCLM of the FMC likely formed during the Cadomian orogeny.

Given the back-arc setting retained for the FMC by the late Ediacaran (e.g. Chelle-Michou et al., 2017 and Chapter 2), the newly formed SCLM would have featured a range of chemical compositions reecting the variable extent of (i) mantle depletion through melt extraction, and (ii) incorporation of a "subduction component" (corresponding to igneous oceanic crust-and/or sediment-derived uids). Melting of such a "patchy" mantle in the CambrianOrdovician adequately explains the wide range of Nb/Yb and Ti/V ratios and the prevalence of samples with high Th/Nb. Variations of the TiO 2 /Yb ratios would result from low melting degrees of the deeper parts of this source (at pressures >3 GPa). As rocks with the highest TiO 2 /Yb also display low MORBOIB-like Th/Nb, the base of this lithospheric mantle may have been less altered by Cadomian slab-derived uids. Alternatively the source of these rocks may correspond to the uppermost part of the asthenosphere. Finally, the radiogenic Nd isotope compositions at 480 Ma displayed by high Th/Nb samples (subset B) would stem from the short time span between mantle enrichment and mantle melting (c. 100 Ma).

Chemical inheritance of the Cadomian subduction in the lithospheric mantle, yet mentioned by [START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF], has never been taken into account while interpreting the chemistry of CambrianOrdovician metabasites. Such model provides an alternative to the back-arc setting advocated by most studies (Berger et al., 2010a;[START_REF] Briand | Les métabasites de la série de Marvejols (Massif central) : témoins d'un magmatisme tholéïtique d'arrière-arc cambro-ordovicien[END_REF][START_REF] Briand | Geochemistry and tectonic implications of two Ordovician bimodal igneous complexes, southern French Massif Central[END_REF][START_REF] Downes | Isotope and traceelement heterogeneities in high-grade basic metamorphic rocks of Marvejols: Tectonic implications for the Hercynian suture zone of the French Massif Central[END_REF][START_REF] Giraud | Geochemistry of leptyno-amphibolite complex from Haut-Allier (French Massif Central)[END_REF][START_REF] Piboule | Geochemistry of eclogites and associated rocks of the southeastern area of the French Massif Central: origin of the protoliths[END_REF]. Importantly, it resolves the problem of the yet unlocated Cambrian

Ordovician subduction zone, which existence is critical in the "back-arc" model. As a result, a lithospheric thinning and associated melting event, coeval with the extensional setting recorded in the overlying crust, would adequately explain the chemistry of the CambrianOrdovician metabasites of the FMC. Therefore, such magmatic activity most probably results from rifting of the North Gondwana margin away from a subduction zone inuence, as proposed by Pin and Marini (1993) and [START_REF] Chèvremont | Notice explicative, Carte géol[END_REF] [START_REF] Demange | Notice explicative, Carte géol[END_REF][START_REF] Downes | Isotopic and trace-element arguments for the lower-crustal origin of hercynien granitoids and pre-hercynian orthogneisses, Massif Central (France)[END_REF][START_REF] Lotout | Ordovician magmatism in the Lévézou massif (French Massif Central): tectonic and geodynamic implications[END_REF]Turpin et al., 1990, and section 3.2). Second, geochronological studies have highlighted the systematic occurrence of inherited zircon grains in dated samples (Chelle-Michou et al., 2017;[START_REF] Lotout | Ordovician magmatism in the Lévézou massif (French Massif Central): tectonic and geodynamic implications[END_REF]Melleton et al., 2010;Pitra et al., 2012;[START_REF] Roger | Première datation UPb des orthogneiss ÷illés de la zone axiale de la Montagne noire (Sud du Massif central) : nouveaux témoins du magmatisme ordovicien dans la chaîne Varisque[END_REF]2015;[START_REF] Trap | Timing and duration of partial melting and magmatism in the Variscan Montagne Noire gneiss dome (French Massif Central)[END_REF]. Third, coeval basic enclaves or associated igneous rocks are scarce in the orthogneiss massifs [START_REF] Demange | Notice explicative, Carte géol[END_REF][START_REF] Lotout | Ordovician magmatism in the Lévézou massif (French Massif Central): tectonic and geodynamic implications[END_REF] which again points to a crustal source for the felsic magmas (Didier et al., 1982).

What triggered partial melting of the crust?

A striking feature of the CambrianOrdovician bimodal magmatism lies in the fact that mac rocks are very subordinate in volume with respect to the felsic massifs. As a direct consequence of this, melting of the continental crust by basaltic magma underplating and associated heat advection must be disregarded. Indeed, numerical models indicate that in such scenario the relative proportions of crust-vs. mantle-derived magmas should be 1:9 [START_REF] Annen | Eects of repetitive emplacement of basaltic intrusions on thermal evolution and melt generation in the crust[END_REF]Annen et al., 2006;Petford and Gallagher, 2001). Similarly, melting of a thickened continental crust has to be rejected because the sedimentological record rather indicates an extensional, shallow marine environment and does not provide any evidence for signicant crustal thickening (Javier [START_REF] Álvaro | Late Ordovician (post-Sardic) rifting branches in the North Gondwanan Montagne Noire and Mouthoumet massifs of southern France[END_REF]Guérangé-Lozes and Burg, 1990). Therefore, question is how to sustain high heat regimes in the crust throughout the CambrianOrdovician. The solution to this issue might dwell in the intrinsic nature of the CambrianOrdovician crust.

Thermal resilience The crust segment exposed in the FMC comprises a thick sedimentary succession deposited during the late-Ediacaran (see section 2.2) in a back-arc basin. High geothermal gradients are observed in such setting because of strong convection in the back-arc mantle (Currie and Hyndman, 2006). When subduction and thus convection cease, the lithosphere cools down by conduction and the geotherm becomes similar to that observed in inactive tectonic domains. Numerical models yield constraints on the duration of the transient cooling state and demonstrate that the crust and lithospheric mantle are still notably warm c. 100 Ma after subduction has ceased and the slab broke o (Currie and Hyndman, 2006). As a result, the CambrianOrdovician crust of the FMC would have still exhibited a thermal imprint of the Cadomian activity, meaning that it likely displayed a steep thermal gradient by that time.

Radioactive heat production As illustrated section 2.2, the Ediacaran detritus originated from: (i) arc crust extracted from the mantle in the CryogenianEdiacaran; (ii) Proterozoic to Archean continental rocks from the Gondwana mainland. Erosion of the latter likely produced a detritus rich in K, Th and U, the main heat producing elements in the continental crust [START_REF] Birch | Heat from radioactivity[END_REF]. Accordingly, a compilation of whole-rock chemical compositions (N=24) of low-to medium-grade Ediacaran metasediments from the eastern Massif Central (data courtesy of J.-F. Moyen and D. Garcia) highlights that those rocks have elevated average K 2 O (3.4 wt.%), U (5.9 ppm) and Th (14.4 ppm) contents. A heat production of 3043 µW/m 3 was calculated for such average crustal composition at 500

Ma based on these concentrations, the equation of [START_REF] Kramers | Crustal heat production and style of metamorphism: a comparison between two Archean high grade provinces in the Limpopo Belt, southern Africa[END_REF], the constants of [START_REF] Rybach | Radioactive heat production in rocks and its relation to other petrophysical parameters[END_REF] and an average density of 2700 kg/m 3 . Such value is c. 40% higher than those derived from average upper crustal compositions, calculated using the same procedure, which yield 1789 µW/m 3 (based on Rudnick and Gao, 2003), 1795 µW/m 3 (based on [START_REF] Wedepohl | The composition of the continental crust[END_REF] and 1888 µW/m 3 (based on Taylor and McLennan, 1985).

Consequently, the Ediacaran sediments constituted layers or horizons of notably high radioactive heat production.

Synergetic eects

The CambrianOrdovician crust of the FMC would have thus featured: (i) a rather steep geotherm, vestige of the high thermal regime of the late Cadomian period; (ii) sedimentary layers with anomalously high radioactive heat production.

Therefore, thermal subsidence and burial of radioactive element-rich layers in such a warm crust segment would have generated thermal anomalies and triggered local anatexis of metasediments at c. 480 Ma, some 50 Ma after the Cadomian subduction ceased.

Such model is adapted from that of [START_REF] Sandiford | High geothermal gradient metamorphism during thermal subsidence[END_REF], initially designed to account for high geothermal gradients observed in high-temperature, low-pressure metamorphic terranes. It readily explains the scarcity of coeval mantle-derived magmas because the thermal trigger of crustal melting lies in the crust itself.

Conclusion

Contrasted CambrianOrdovician geodynamic models have been proposed for the crust segment today exposed in the FMC. Among them, the back-arc setting model has proven very popular (Berger et al., 2010a;[START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF][START_REF] Downes | Isotope and traceelement heterogeneities in high-grade basic metamorphic rocks of Marvejols: Tectonic implications for the Hercynian suture zone of the French Massif Central[END_REF]Pin and Marini, 1993). Yet, a careful examination of the literature together with new geochemical data on basic igneous rocks discards any CambrianOrdovician subduction zone inuence in the FMC for several reasons:

there is no compelling evidence for the presence of an active subduction zone nearby the FMC by the Ordovician;

the "subduction component" present in the mantle source of basic rocks would have been inherited from the pre-dating Cadomian subduction;

anatexis leading to voluminous crust-derived granitic magmas was neither triggered by mac magmas underplating nor the consequence of a thickening episode, as generally observed in back-arc basins (Collins and Richards, 2008).

In contrast, the extensional continental rift setting readily complies with a large set of geological observations and is in notable agreement with the sedimentary, tectonic and magmatic records which are summarized

Introduction

Following crustal thickening, the final stages of continental collision, associated with lateral extension or orogenic collapse, are periods of intense magmatic activity characterized by emplacement of granitoids derived from both crustal and mantle sources (Liégeois et al. 1998;[START_REF] Bonin | Do coeval mafic and felsic magmas in post-collisional to withinplate regimes necessarily imply two contrasting, mantle and crustal, sources? A review[END_REF][START_REF] Clemens | Sources of post-orogenic calcalkaline magmas: the Arrochar and Garabal Hill-Glen Fyne complexes[END_REF][START_REF] Vanderhaeghe | The thermal-mechanical evolution of crustal orogenic belts at convergent plate boundaries: a reappraisal of the orogenic cycle[END_REF]Laurent et al. 2014a). Granitoid magmas represent major heat and mass transfers from the lower to the upper crust, contributing to crustal differentiation, thermal maturation and ore deposits [START_REF] Petford | Granite magma formation, transport and emplacement in the Earth's crust[END_REF][START_REF] Kemp | Granitic perspectives on the generation and secular evolution of the continental crust[END_REF][START_REF] Hou | Metallogenesis of the Tibetan collisional orogen: a review and introduction to the special issue[END_REF]. Voluminous layers of partially molten rocks at mid to lower crustal levels, as evidenced in modern orogens by geophysical investigations [START_REF] Nelson | Partially molten middle crust beneath southern Tibet: synthesis of project INDEPTH results[END_REF][START_REF] Schilling | Quantifying partial melt fraction in the crust beneath the central Andes and the Tibetan Plateau[END_REF], influence the thermomechanical behavior of the orogenic crust and its coupling to the lithospheric mantle (Brown 2001;Vanderhaeghe and Teyssier 2001;[START_REF] Schulmann | Vertical extrusion and horizontal channel flow of orogenic lower crust: key exhumation mechanisms in large hot orogens?[END_REF]Vanderhaeghe 2009;[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]. In addition, the mafic magmas emplaced during these periods and their derivatives may represent significant additions to the preexisting continental volume (Laurent et al. 2013;Couzinié et al. 2016;Moyen et al. in press). Therefore, late-to post-collisional magmatism is of primary interest to understand (i) the mechanisms of heat and mass transfer in the lithosphere; (ii) the geodynamic evolution at convergent plate boundaries; and (iii) continental crust formation and differentiation. The Paleozoic Variscan belt of western Europe is often referred to as a "hot" orogen [START_REF] Schulmann | Vertical extrusion and horizontal channel flow of orogenic lower crust: key exhumation mechanisms in large hot orogens?[END_REF]) characterized by the emplacement of abundant and diverse granitoid magmas, especially at the end of the continental collision sensu stricto and throughout late-orogenic collapse (Pin and Duthou 1990;[START_REF] Finger | Variscan granitoids of central Europe: their typology, potential sources and tectonothermal relations[END_REF]Gardien et al. 1997;Fernández-Suárez et al. 2000;[START_REF] Janoušek | Modelling diverse processes in the petrogenesis of a composite Batholith: the Central Bohemian Pluton, Central European Hercynides[END_REF][START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF]). In the French Massif Central (FMC), the late-Variscan collapse led to the formation of the 305-300 Ma Velay granite-migmatite complex (Montel et al. 1992;Mougeot et al. 1997;Couzinié et al. 2014), a roughly circular dome of >100 km diameter and >6000 km 2 (Fig. 1), consisting of migmatites cored by a heterogeneous cordierite-bearing granite (Ledru et al. 2001;[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]. It is suggested that the Velay dome was formed in response to a long-lived (>40 Ma) period of HT metamorphism and partial melting of the orogenic crust [START_REF] Vanderhaeghe | Exhumation of migmatites in two collapsed orogens: Canadian cordillera and French Variscides[END_REF]Ledru et al. 2001;Vanderhaeghe and Teyssier 2001;[START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF], first through limited low-temperature, possibly water-present melting between ca. 340 and 314 Ma; and second through high-temperature, extensive biotite breakdown melting at 310-300 Ma (Montel et al. 1992;Mougeot et al. 1997;Barbey et al. 1999[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Couzinié et al. 2014).

Field relationships indicate that voluminous granitoid plutons and batholiths were emplaced before, during and after its formation (Ledru et al. 2001;Faure et al. 2009). Indeed, available geochronological data hint that granite formation lasted for several tens of million years between the early Carboniferous (340 ± 20 Ma) and early Permian (295 ± 15 Ma) (Duthou et al. 1984;Montel et al. 1992;[START_REF] Briand | Felsic (A-type)basic (plume-induced) Early Palaeozoic bimodal magmatism in the Maures Massif (southeastern France)[END_REF]Bé Mézème et al. 2006; Table 1). Moreover, granitoids are associated with volumetrically minor, but spatially ubiquitous mafic magmas, i.e., potassic to ultrapotassic diorites, gabbros and/or lamprophyres, locally referred to as "vaugnerites" (Sabatier 1991;[START_REF] Solgadi | The relative roles of crustal anatexis and mantle-derived magmas: generation of Synorogenic, Hercynian granites in the Livradois area, French Massif Central[END_REF][START_REF] Scarrow | Shoshonites, vaungerites and potassic lamprophyres: similarities and differences between 'ultra'-high-K rocks[END_REF][START_REF] Von Raumer | Durbachites-Vaugnerites-a geodynamic marker in the central European Variscan orogen[END_REF]Couzinié et al. 2014Couzinié et al. , 2016)). Several questions arise from those observations. First, the genesis of large volumes of granite throughout the Carboniferous apparently contradicts the model proposed by some authors for the formation of the Velay dome, which implies that crustal anatexis was limited prior to 310 Ma and only produced significant amounts of granitic magmas at 310-300 Ma (Montel et al. 1992;Ledru et al. 2001). It has also been proposed that the formation of these granites and their ascent through the crust explains the temperature increase associated with the formation of the Velay dome at 310-300 Ma [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF], but then the problem translates to the origin of the heat source responsible for the genesis of the granites [START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF]. Second, the role played by mafic magmas in the late-orogenic evolution is poorly understood; in particular, it is not yet clear whether the mafic magmas are responsible for crustal melting, or whether they represent a side effect of the processes at the origin of crustal anatexis.

To be addressed, those problems require a reliable geochronological framework for both granitic and mafic magmatism. Such a dataset is still lacking in the eastern FMC, where most available ages are either imprecise and possibly inaccurate radiometric dates based on whole-rock isochrons (Rb-Sr or Sm-Nd) or recent U-Pb dates but focused on small areas or specific plutons. This prevents a largescale and systematic understanding of the magmatic evolution and questions the existence of long-lived granitic emplacement prior to the formation of the Velay complex, since this may only be an artifact of the large uncertainties on the existing ages. In fact, the most recent U-Pb ages obtained on igneous rocks in the eastern FMC are almost exclusively in the range 310-300 Ma (Brichau et al. 2008;François 2009;[START_REF] Gardien | Thermal maturation and exhumation of a middle orogenic crust in the Livradois area (French Massif Central)[END_REF][START_REF] Barbarin | Notice explicative, Carte géol[END_REF]Didier et al. 2013;Couzinié et al. 2014), i.e., coeval with the migmatites and granites of the Velay dome. Furthermore, only a handful of ages are available so far on the mafic rocks [START_REF] Aït-Malek | Petrology, geochemistry and U/Pb geochronology of acid-basic associations: examples from SE Velay (French Massif Central) and western anti-Atlas (Morocco)[END_REF]Couzinié et al. 2014).

The aim of this study is therefore to provide a self-consistent geochronological dataset on both granites and mafic rocks in the eastern FMC. For this purpose, we sampled a total of 18 granitoids and 15 vaugnerites, representative of the lithological diversity observed at the regional scale, and performed U-Pb dating on individual zircons (and monazites for some samples) by laser ablation, sector field inductively coupled plasma mass spectrometry (LA-SF-ICP-MS). The results are used to discuss (i) the petrogenesis of the magmas; (ii) the nature of the heat source at the origin of late-Variscan magmatism in the eastern FMC; and (iii) its significance for the geological and tectonic evolution of the orogen.

Geological setting

The French Massif Central (FMC)

The Variscan belt of Western Europe (Fig. 1a) belongs to a Paleozoic orogenic system that results from convergence between Laurussia, Gondwana and several intervening microcontinents (Matte 1986;Kroner and Romer 2013;Stampfli et al. 2013), which ended up with the assembly of Pangea. The FMC is part of the inner domain of this belt (Lardeaux et al. 2014), referred to as the "Moldanubian" zone, and represents a reworked crustal domain that was previously formed along the northern margin of Gondwana (Faure et al. 2009;Melleton et al. 2010).

The FMC hosts a south-verging Devonian to early Carboniferous nappe pile (Ledru et al. 1989;Faure et al. 2009) that became dismembered by late Carboniferous ductile and brittle strike-slip shear zones and detachments accommodating late-orogenic extension and collapse [START_REF] Malavieille | Collapse of the thickened Variscan crust in the French Massif Central: Mont Pilat extensional shear zone and St. Etienne Late Carboniferous basin[END_REF]Faure 1995;Gardien et al. 1997). In the eastern FMC (Fig. 1b), this pile is made up from top to bottom (north to south) by: 1. The Brévenne unit, a greenschist-facies volcano-sedimentary basin [START_REF] Feybesse | La série de la Brévenne (Massif Central français): une unité dévonienne charriée sur le complexe métamorphique des Monts du Lyonnais à la fin de la collision varisque[END_REF]) of late Devonian age (366 ± 5 Ma; Pin and Paquette 1997), presumably a back-arc system formed as a result of the southwards subduction of the Rheic Ocean (Lardeaux et al. 2014). 2. The Upper Gneiss Unit (UGU) consists of high-grade, migmatitic ortho-and paragneisses whose protoliths are early Ordovician in age (Duthou et al. 1984;Melleton et al. 2010;[START_REF] Chelle-Michou | New U-Pb and Hf zircon data from the eastern Massif Central: from Gondwana to Pangea in a nutshell[END_REF]Lotout et al. in press). The base of the UGU is characterized by the presence of (i) the leptynite-amphibolite complex (LAC), a bimodal Ordovician (487-478 Ma) magmatic association (Pin and Lancelot 1982;[START_REF] Briand | Geochemistry and tectonic implications of two Ordovician bimodal igneous complexes, southern French Massif Central[END_REF] proposed to represent an ocean-continent transition zone (Lardeaux et al. 2014); and (ii) relics of (U)HP metamorphic rocks (Gardien et al. 1990;[START_REF] Mercier | On the tectonic significance of retrograde P-T-t paths in eclogites of the French Massif Central[END_REF]Gardien 1993;Lardeaux et al. 2001) (Dupraz and Didier 1988;Ledru et al. 2001). 4. The Para-autochthonous Unit (PAU), dominantly made up of greenschist-to lower amphibolite-facies metasediments (Cévennes schists; Faure et al. 1999) deposited between the Neoproterozoic and the early Cambrian (Caron 1994;Melleton et al. 2010).

The tectono-metamorphic evolution of the eastern FMC can be summarized as follows. An early (D-M 0 ) (U)HP metamorphic event attributed to northward subduction was dated between 432 and 408 Ma (Pin and Lancelot 1982;Ducrot et al. 1983;Paquette et al. 1995;Do Couto et al. 2015) and recorded by the eclogitic relics (at the base of the UGU and in the LAC). The UGU experienced anatexis (M 1 ) coeval with exhumation of the (U)HP units and topto-the-SW shearing (D 1 ) (Faure et al. 2008(Faure et al. , 2009) ) between 384 ± 16 Ma (Duthou et al. 1994) and360 ± 4 Ma (Gardien et al. 2011). The UGU was subsequently juxtaposed to the north to the Brévenne unit during top-to-the-NW (D-M 2 ) thrusting (Leloix et al. 1999) at ~360-350 Ma [START_REF] Faure | Late Visean thermal event in the northern part of the French Massif Central: new 40 Ar/ 39 Ar and Rb-Sr isotopic constraints on the Hercynian syn-orogenic extension[END_REF]. This episode is also recorded in the western part of the FMC (Limousin area) by 360 ± 4 Ma top-to-the-NW thrusting [START_REF] Melleton | Monazite U-Th/Pb chemical dating of the Early Carboniferous syn-kinematic MP/MT metamorphism in the Variscan French Massif Central[END_REF]) and corresponds to the main event of nappe stacking (Faure et al. 2009). The early Carboniferous D 3 event corresponds to the onset of syn-orogenic extension in the northern part of the FMC, as recorded by 340-330-Ma-old volcano-sedimentary sequences (Bruguier et al. 1998), while crustal thickening was still ongoing in the southern domain, especially the PAU which experienced top-to-the-S thrusting [START_REF] Arnaud | Microstructures des mylonites schisteuses : cartographie des chevauchements varisques dans les Cévennes et détermination de leur cinématique[END_REF]Caron 1994). Subsequently, the nappe pile, specifically the LGU, was extensively reworked by a pervasive Carboniferous LP-HT event that culminated with the rise of the Velay dome (Ledru et al. 2001). This reworking process was proposed to happen in two steps (Montel et al. 1992;[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]): (i) limited anatexis in the LGU with biotite remaining stable 428 Int J Earth Sci (Geol Rundsch) (2017) 106:421-451 1 3 (T < 750 °C), at ages between 329 ± 5 Ma (Bé Mézème et al. 2006) and 314 ± 5 Ma (Mougeot et al. 1997); and (ii) widespread biotite dehydration melting (760 < T < 850 °C) that affected the whole middle crust and gave rise to the formation of the Velay dome proper at 301-305 Ma (Couzinié et al. 2014). Those late Carboniferous events are attributed to N(W)-S(E)-directed late-orogenic extension (D 4-5 ) associated with large-scale crustal detachments and formation of detrital coal-bearing basins [START_REF] Malavieille | Collapse of the thickened Variscan crust in the French Massif Central: Mont Pilat extensional shear zone and St. Etienne Late Carboniferous basin[END_REF]Faure et al. 2009).

Petrographic-geochemical characteristics of late-Variscan igneous rocks in the eastern FMC

Exposure in the eastern FMC is largely dominated by Carboniferous plutonic rocks intruding the metamorphic lithologies described earlier (Fig. 1b). Based on existing petrographic descriptions and classifications [START_REF] Didier | Les granites du Massif Central Français. Etude comparée des leucogranites et des granodiorites[END_REF]Didier et al. 1982;Barbarin 1983Barbarin , 1992[START_REF] Barbarin | A review of the relationships between granitoid types, their origins and their geodynamic environments[END_REF][START_REF] Stussi | Le magmatisme orogénique granitique de la chaîne varisque française. Typologie chimique et répartition spatiale[END_REF][START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF]Moyen et al. in press), four types of plutonic rocks can be distinguished (Fig. 1b) (nomenclature after Barbarin 1999):

1. Peraluminous to slightly metaluminous, biotite-and sometimes cordierite-bearing granitoids ("CPG") are the most abundant (Fig. 1b). They can be separated in two subgroups: (i) K-feldspar porphyritic, cordieritepoor plutons and batholiths (Margeride, Chaise-Dieu, Tournon) characterized by the presence of microgranular mafic enclaves (MMEs; Didier et al. 1982) and (ii) the cordierite-rich, heterogeneous Velay granite, which is closely associated with LGU migmatites and fre-quently contains large enclaves of the previous, cordierite-poorer type [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Ledru et al. 2001;Williamson et al. 1997). CPG are granites and granodiorites (Fig. 2a) with a peraluminous character (Fig. 2b) and elevated contents in SiO 2 (>65 wt%) and K 2 O (3-7 wt%) (Fig. 2c). Those characteristics, together with Sr-Nd isotopic data, reflect that the CPG result from partial melting of the local crust (Duthou et al. 1984;Pin and Duthou 1990;Downes et al. 1997;Williamson et al. 1997). 2. Peraluminous, two-mica or muscovite-bearing (leuco-) granites ("MPG"), generally occurring as dykes and small laccoliths intrusive in the Velay complex (Ledru et al. 2001;Didier et al. 2013) as well as rare plutons (L'Hermitage, Saint-Christophe-d'Allier). The MPG show a tighter compositional range than the CPG. They are granites sensu stricto (Fig. 2a) with a clearer peraluminous character (Fig. 2b) and restricted to SiO 2 contents >70 wt% (Fig. 2b-c), pointing to a crustal source (Pin and Duthou 1990;[START_REF] Barbarin | A review of the relationships between granitoid types, their origins and their geodynamic environments[END_REF]) (Fig. 2d). 3. Weakly peraluminous to metaluminous, K-feldspar porphyritic, biotite-± amphibole-bearing granites, granodiorites and quartz-diorites ("KCG"). They either form large plutons (Saint-Julien-la-Vêtre, Pont-de-Montvert, Aigoual) or enclaves within the Velay complex, of various sizes (a few cm across to pluri-kilometric screens like the Gumières enclave; [START_REF] Barbarin | Notice explicative, Carte géol[END_REF]. The composition of the KCG largely overlaps that of the CPG, yet they are on average slightly more "mafic" than the latter (average SiO 2 and FeO t + MgO of KCG are ~69 and ~4.0 wt%, respectively, against ~72 and ~2.5 wt% for CPG) (Fig. 2). This makes KCG chemically intermediate between vaugnerites and MPG-CPG (Fig. 2) and led several authors to propose that they result from magma mixing between vaugnerites and crustal melts (Downes et al. 1997;[START_REF] Solgadi | The relative roles of crustal anatexis and mantle-derived magmas: generation of Synorogenic, Hercynian granites in the Livradois area, French Massif Central[END_REF]). 4. A suite of metaluminous, biotite-, amphibole-± clinopyroxene-bearing intermediate to mafic rocks locally called "vaugnerites", which are akin to Mg-K magmatic rocks such as appinites, durbachites and lamprophyres (Sabatier 1991;[START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF][START_REF] Scarrow | Shoshonites, vaungerites and potassic lamprophyres: similarities and differences between 'ultra'-high-K rocks[END_REF][START_REF] Von Raumer | Durbachites-Vaugnerites-a geodynamic marker in the central European Variscan orogen[END_REF]Couzinié et al. 2014Couzinié et al. , 2016)). Although they do not form mappable bodies at the scale of Fig. 1b, they are regionally ubiquitous and occur as enclaves (0.1-100 m in size) in the granitoids (Didier et al. 1982;Ledru et al. 2001), kilometric stocks and lamprophyric dykes. They form a compositionally heterogeneous group of gabbroic to dioritic rocks (Fig. 2a), yet all characterized by metaluminous affinities (Fig. 2b), lower SiO 2 (45-65 wt%) and higher FeO t + MgO (up to 25 wt%) than coexisting granitoids, together with high-K to shoshonitic affinities (K 2 O = 1.5-6.0 wt%) and richness in incompatible trace elements (Sr + Ba, but also REE and HFSE) (Fig. 2c,d). This dual geochemical character clearly points to an enriched (metasomatized) lithospheric mantle source (Sabatier 1991;[START_REF] Solgadi | The relative roles of crustal anatexis and mantle-derived magmas: generation of Synorogenic, Hercynian granites in the Livradois area, French Massif Central[END_REF][START_REF] Von Raumer | Durbachites-Vaugnerites-a geodynamic marker in the central European Variscan orogen[END_REF]Couzinié et al. 2014Couzinié et al. , 2016)).

Analytical methods

We selected 33 samples for U-Pb dating, collected throughout the eastern MCF (Fig. 1b) and representative of the geochemical diversity reported earlier (Table 1; Fig. 1b). Samples weighing 5-10 kg were reduced using jaw and disk mills and sieved to <500 µm. Heavy minerals were extracted by using conventional concentration techniques (shaking table, magnetic separator, heavy liquids). Between 50 and 100 zircon grains per sample, but also monazite wherever available, were handpicked, set in 1-inch epoxy mounts and polished to expose their interiors. The internal structures of these grains were characterized by cathodoluminescence (CL) and back-scattered electron (BSE) imaging prior to LA-SF-ICP-MS dating using (i) a Jeol JSM-6490 scanning electron microscope (SEM) equipped with a Gatan MiniCL at Goethe University Frankfurt (GUF) for the granite samples and (ii) a ZEISS EVO-150 SEM at University of Granada (Spain) for the vaugnerite samples. U-Pb isotopic analyses were carried out at GUF by laser ablation using a Resolution M-50 (Resonetics) 193-nm ArF excimer laser system attached to Thermo Finnigan Element 2 sector field ICP-MS. A detailed description of the analytical techniques is available in the Supplementary Material. The data were corrected offline for background signal, common Pb, instrumental mass discrimination and downhole Pb/U fractionation using an in-house MS Excel© spreadsheet (Gerdes andZeh 2006, 2009). For both zircon and monazite analyses, the corrections and determination of U, Th and Pb compositions were performed using normalization to standard zircon GJ-1. Reference materials Plešovice, OG-1 and BB (for zircon sessions) and Moacir, Manangoutry and in-house WM (for monazite sessions) were used as secondary standards to check the accuracy of the corrections, and all provide ages in good agreement with the reference values (see supplementary material Table S1). Age calculations and data plotting were performed using the Isoplot toolkit (Ludwig 2008) v.4.15 for MS Excel©. The complete dataset is available as supplementary material (Table S2).

Results

Zircon textures

Figure 3 shows representative CL and BSE images of zircons from igneous plutonic rocks of the eastern FMC. Zircon characteristics depend on the rock type considered. The MPG and CPG show heterogeneous zircon populations, having a range of sizes (from 50 up to 500 µm) and shapes (aspect ratios between 1.5 and 8), some of them being obvious xenocrysts (broken or irregular edges crosscutting the internal zoning). Grains with clear core-rim relationships are very common in both granitoid types: they show rounded or sub-idiomorphic CL-bright cores with oscillatory zoning, wrapped by CL-darker rims (Fig. 3a). The rims often show irregular or very fine oscillatory zoning, occasionally with porous textures and/or inclusions, and are generally wider (>50 µm) in CPG than in MPG (<50 µm) (Fig. 3a). The CPG and MPG also contain core-free, 1 3 idiomorphic to xenomorphic crystals (scarce in MPG but dominant in CPG). These are relatively CL-dark, and show irregular or banded zoning patterns (Fig. 3a). A notable exception among the CPG is sample OL-13-06 (Margeride granite), of which zircons are relatively CL-bright, and display a well-developed oscillatory zoning and distinct aspect ratios (Fig. 3a).

Zircon grains in the KCGs are less diverse than in the CPG and MPG, and seldom show core-rim relationships (if any). Resorbed cores occasionally occur in samples SDZ (Fig. 3b) and PMV, and a single xenocryst was found in sample SGC-12-49B (Fig. 3b). The crystals are usually 100-350 µm long, form idiomorphic prisms with aspect ratios between 1.5 and 3, and reveal a concentric oscillatory zoning. They are CL-brighter than the zircons from the CPG and MPG (Fig. 3b). Zircon populations in vaugnerites are very homogeneous within a given sample, without any core-rim relationships (except sample SC13-14; Fig. 3b). The crystals range in size from 70 to 500 µm and display various shapes, from short prismatic to needle-shaped (aspect ratios between 1.5 and 6). In most samples, the grains appear CL-dark and display striped or sector zoning, but in two SiO 2 -richer samples (quartz-syenites PRC-53 and PRC-54), oscillatory zoning is predominant (Fig. 3b). Back-scattered electron (BSE) images of monazite grains from the four samples in which this mineral was investigated are reported in the Supplementary Material.

U-Pb dates

Zircon populations were dated in 33 samples and monazite grains in four of them . A detailed description of the data, statistics, as well as the complete set of Concordia diagrams, is available in the Supplementary Material. The most important points arising from this description, together with representative Concordia diagrams, are reported hereafter.

Based on the combination of U-Pb dating results and zircon textures, the investigated samples can be subdivided into three major groups (Table 1):

-1 9 3 ± 1 4 0
Cores & Xen.

( ) showing examples of zircon analyses from samples of "group 2" (V = vaugnerite), i.e., showing a single generation of zircon (i.e., scarce or no core-rim relationships) but scattered 206 Pb/ 238 U dates with a Carboniferous upper intercept age, and a lower intercept at or close to zero within uncertainty. The inset in the bottom right of b represents a close-up to the analyses from two zircon cores, reported as shaded ellipses. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb. The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept. All ages are quoted to 2σ level of uncertainty 1 3

• Group 1 (Fig. 4) samples are characterized by (i) zircons with the absence of any core-rim relationship; and (ii) zircon U-Pb analyses yielding a single generation of Carboniferous (to early Permian) U-Pb dates, the majority of which (>65% and commonly up to 85%) being identical within uncertainties and concordant. This includes most vaugnerite samples as well as two KCG (OL-13-24 and PRC-56). • Group 2 (Fig. 5 Figure 7 compiles the data obtained from zircon cores in samples of groups 2 and 3. Out of 170 analyses, 106 are >90% concordant, with only few of them having dates >800 Ma (n = 12). The others reveal a nearly continuous date spectrum between 740 and 340 Ma, with a major peak at 540 ± 20 Ma (n = 45; 42% of all concordant data), and minor peaks at 475 ± 20 Ma (n = 12); 625 ± 10 Ma (n = 6); 375 ± 10 Ma (n = 8); and 340 ± 10 Ma (n = 5). There are additional minor peaks at 850 ± 15 Ma (n = 3) and ~955 Ma (n = 2), and a few grains reveal (mostly discordant) dates between ~1025 and ~2600 Ma.

Discussion

From date to age: interpretation of U-Pb data

In the following, the signification of zircon U-Pb dates obtained in each group of samples presented in the previous section is discussed, on the basis of zircon textures and U-Pb data. These interpretations are summarized in Table 1, where the deduced emplacement ages are reported.

• Samples from group 1 contain no zircon cores and are characterized by a population of concordant U-Pb dates that, with the exception of few outliers, are identical within uncertainties (Fig. 4). Therefore, the Concordia dates calculated from such data can be considered as representative of the emplacement age for samples of this group. This includes the KCG samples OL-13-24 (321. Zircons from these samples can be considered as essentially undisturbed by any post-magmatic event.

• Zircon analyses in samples from group 2 yield Carboniferous dates that are generally concordant within uncertainty, but cannot be combined into a single date, as they show a wide range in 206 Pb/ 238 U ratios (Fig. 5). Such zircons, or at least part of them, most probably underwent post-magmatic disturbance of the U-Pb isotopic system. This likely took place through diffusion, fluid-driven dissolution-recrystallization or diffusionreaction processes (Gerdes and Zeh 2009) such that the resulting scatter in 206 Pb/ 238 U dates can be explained by variable extent of radiogenic Pb loss (Fig. 5). This assumption is supported by (i) the fact that most samples have lower intercept ages at about zero within uncertainty; and (ii) the observation that the analyses with the youngest 206 Pb/ 238 U dates often correspond to U-rich, metamict domains and/or porous zones rich in common Pb (Figs. 3,5; see also Supplementary Material) that are particularly prone to Pb loss (Mezger and Krogstad 1997;[START_REF] Geisler | Leaching and differential recrystallization of metamict zircon under experimental conditions[END_REF]. Following this interpretation, the upper intercepts of these "Discordia" trends should represent the crystallization age of the samples. This upper intercept date is always identical within uncertainties to the (more precise) Concordia date calculated by using the equivalent analyses with the highest 206 Pb/ 238 U ratios (Figs. 5,6). The latter is thus considered as the best estimate for the crystallization age of the samples. This interpretation applies to the CPG sample OL-13-06 (312.9 ± 2.0 Ma), the KCG samples PMV (302.5 ± 0.9 Ma), SDZ (337.4 ± 1.0 Ma) and SGC-12-49B (298.9 ± 1.8 Ma) as well as the vaugnerite samples 533-2 (307.3 ± 1.3 Ma), PRC-53 (318.9 ± 1.8 Ma), PRC-54 (320.5 ± 1.8 Ma), SC-13-05 (309.4 ± 1.5 Ma) and SC-13-14 (335.7 ± 2.1 Ma). • Finally, samples from group 3 clearly contain complex zircon populations, in which the grains were formed by several, distinct crystallization events. This is well illustrated by core-rim relationships, with cores and rims having significantly different ages (Figs. 3a,6). The most straightforward interpretation is that (i) zircon Cores & Xen. cores represent either xenocrysts or crystals inherited from a zircon-bearing source material; and (ii) zircon rims, or grains devoid of any core, crystallized from the magma. The latter generally show the same distribution of U-Pb dates as zircon from samples of group 2, i.e., a range of apparent 206 Pb/ 238 U dates from a Carboniferous upper intercept and a lower intercept around zero. We thus apply the same interpretation as for group 2 samples, i.e., that such trends reflect the crystallization of zircon during emplacement of the host granitic magma, followed by recent loss of radiogenic Pb. This group includes all the MPG samples: HER (325.7 ± 1.3 Ma), OL-13-08 (311.0 ± 1.1 Ma) and OL-13-09 (312.7 ± 2.3 Ma); and most CPG samples: CHZ (332.0 ± 2.0 Ma), OL-13-11 (314.5 ± 1.7 Ma), OL-13-14 (318.3 ± 2.6 Ma), OL-13-21 (336.9 ± 1.8 Ma), TN-10 (321.9 ± 1.3 Ma), TN-19 (321.1 ± 1.1 Ma) and TOU-01 (322.2 ± 1.5 Ma). [START_REF] Respaut | Géochronologie et géochimie isotopique U-Pb de la minéralisation uranifère de la mine des Pierres Plantées (Lozère) et de son encaissant: le massif granitique de la Margeride[END_REF] on the Margeride granite.

The ages of ~320 Ma obtained on laccoliths from the eastern flank of the Velay dome (Tournon granite and associated intrusions; samples TN-10, TN-19 and TOU-01) are slightly younger than the Rb-Sr wholerock isochron age of 337 ± 13 Ma obtained by Batias and Duthou (1979), but their data also include samples from the Vienne pluton further north, for which no zircon age is available. showing examples of zircon analyses from samples of "group 3", i.e., showing several generations of zircon crystallization (core-rim relationships) and scattered 206 Pb/ 238 U dates with a Carboniferous upper intercept age, and a lower intercept at or close to zero within uncertainty. Insets in the bottom right represent the close-up to the analyses from zircon cores or xenocrysts ("Xen."), reported as shaded ellipses. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb. The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty ◂ 1 3

Finally, the monazite age of 302.8 ± 1.3 Ma obtained from the Velay granite at the Pont-Rouge quarry (sample PRC-57) is in line with the existing data obtained by different methods, including whole-rock Rb-Sr [START_REF] Caen-Vachette | Ages radiométriques des granites anatectiques et tardimigmatitique du Velay (Massif Central français)[END_REF] and monazite U-Th-Pb dating by ID-TIMS (Mougeot et al. 1997) or LA-ICP-MS (Couzinié et al. 2014), all pointing to crystallization ages in the range 305-300 Ma. 2. MPG In the northern part of the study area, the age of 327 Ma obtained for the Hermitage granite (sample HER) is identical to a whole-rock Rb-Sr isochron age of 329 ± 14 Ma (C. Pin, unpublished data mentioned in [START_REF] Didier | Notice explicative, Carte géologique de la France (1/50 000 e ), feuille Noirétable (nr. 695)[END_REF]. This age also complies with structural observations, since the Hermitage granite is a syn-kinematic intrusion emplaced along a WNW-ESEtrending dextral, strike-slip shear zone attributed to the D 3 deformation event (Barbarin 1983) that was most likely active at ~327 Ma, in agreement with a general NW-SW-directed stretching recorded throughout the FMC at that time (Faure et al. 2009).

In the Margeride area, the U-Pb ages of 311-309 and 313 Ma obtained for the Grandrieu leucogranite (sample OL-13-08) and Saint-Christophe-d'Allier pluton (sample OL-13-09), respectively, overlap with existing U-Pb ID-TIMS monazite ages of 305 ± 14 (Isnard 1996) and 305 ± 9 Ma (Lafon and Respaut 1988) for those two intrusions. Our ages are also identical within uncertainties to that of the Margeride granite (Table 1), which is crosscut by the Grandrieu granite in the field. This means that the two magmatic events were close enough in time such that they cannot be distinguished with respect to analytical uncertainties. 3. KCG The age of 337.4 ± 1.0 Ma obtained for the Salten-Donzy pluton (sample SDZ) is the first to document the absolute age of this intrusion. It is identical to whole-rock Rb-Sr isochron ages of 339 ± 8 and 322 ± 32 Ma obtained from granites flanking NE-SWtrending dextral shear zones in the Lyonnais mountains (Gay et al. 1981) and close to the ages of vaugnerite samples obtained from the same area (336-334 Ma; see below). For the Saint-Julien-la-Vêtre pluton (sample SJV), the obtained age of 330.1 ± 1.3 Ma is consistent with an early Rb-Sr whole-rock isochron age of 340 ± 20 Ma (C. Pin, unpublished data quoted in [START_REF] Didier | Notice explicative, Carte géologique de la France (1/50 000 e ), feuille Noirétable (nr. 695)[END_REF]) and field relationships, since the pluton is intruded by the significantly younger (325.7 ± 1.3 Ma-old) Hermitage granite (Barbarin 1983;[START_REF] Didier | Notice explicative, Carte géologique de la France (1/50 000 e ), feuille Noirétable (nr. 695)[END_REF]). The age of ~321 Ma obtained for the Gumières quartzdiorite (sample OL-13-24) is notably older than that obtained by [START_REF] Be Mezeme | Structural, AMS and geochronological study of a laccolith emplaced during Late Variscan orogenic extension: the Rocles pluton (SE French Massif Central)[END_REF] using the same technique (313 ± 2 Ma; U-Pb LA-ICP-MS on zircon). Excluding dating problems, this discrepancy might result from sampling of different lithologies in the composite Gumières Massif, which consists of porphyritic granodiorite associated with minor quartz-diorite, equigranular granite and dikes of the surrounding Velay granite [START_REF] Barbarin | Notice explicative, Carte géol[END_REF]. The sample dated by [START_REF] Be Mezeme | Structural, AMS and geochronological study of a laccolith emplaced during Late Variscan orogenic extension: the Rocles pluton (SE French Massif Central)[END_REF] may derive from the dominant biotite-bearing porphyritic granodiorite, whereas our sample is clearly more mafic (amphibole-bearing) and would thus derive from a dioritic enclave within this granodiorite, which are common yet not easy to identify given the scarcity of exposed contacts [START_REF] Barbarin | Notice explicative, Carte géol[END_REF]. Another enclave within the Velay granite, sample PRC-56, yielded an age of 332.1 ± 0.7 Ma that is roughly equivalent to that of a suite of orthoclase-rich granites cropping out along the eastern margin of the Velay complex in the Vivarais area, dated at 353 ± 21 Ma (Rb-Sr whole-rock isochron) and 341 +8/-5 (U-Pb ID-TIMS on zircon, upper intercept age with two subconcordant spots at ~335 Ma) [START_REF] Briand | Felsic (A-type)basic (plume-induced) Early Palaeozoic bimodal magmatism in the Maures Massif (southeastern France)[END_REF].

To the south of the Velay complex, in the Cévennes area, the age of 299 Ma obtained on sample SGC-12-49B from the Largentière granite is identical within uncertainties to that obtained by Couzinié et al. (2014) for the same granite (304.1 ± 6.3 Ma; U-Pb LA-ICP-MS on zircon) and also close to that of sample PMV from the Pont-de-Montvert pluton (302.5 ± 0.9 Ma). Both ages are identical within uncertainties to ages of 301 ± 4 and 307 ± 11 Ma (zircon and monazite U-Pb ID-TIMS) in the Mont-Lozère and Aigoual granitic complexes (Brichau et al. 2008;François 2009). Moreover, they overlap with Ar-Ar ages of 306-301 Ma obtained from aplitic-pegmatitic dykes and Au-mineralized quartz veins in the vicinity of the Mont-Lozère complex (Chauvet et al. 2011). 4. Vaugnerites Our new age data suggest that the vaugnerites in the eastern FMC intruded over >35 Ma, between 335.7 ± 2.1 Ma (SC-13-14) and 299.1 ± 1.3 Ma (LR-31). This period is much longer than previously suggested [START_REF] Aït-Malek | Petrology, geochemistry and U/Pb geochronology of acid-basic associations: examples from SE Velay (French Massif Central) and western anti-Atlas (Morocco)[END_REF]Couzinié et al. 2014). In the northern part of the study area, the new emplace-ment ages of ~335 Ma for the syn-kinematic vaugnerite dikes/bodies in the Lyonnais area (SC-13-14 and SC-13-19) are consistent with existing Rb-Sr data of 339 ± 8 and 322 ± 32 Ma obtained from nearby (and, as shown by magma mixing relationships, coeval) granites (Gay et al. 1981).

In the western and central parts of the Velay complex, no absolute ages were available so far for vaugnerite intrusions. (Couzinié et al. 2014).

Significance of inherited zircon ages

Zircon xenocrysts from CPG and MPG reveal an age spectrum characterized by abundant early Paleozoic to Neoproterozoic ages between ~450 and ~740 Ma (with more prominent peaks at ~475, ~540 and ~625 Ma), together with very minor Grenville (955-1025 Ma) and Paleoproterozoic to early Archean ages (1800-2600 Ma) (Fig. 7). Such an age spectrum is similar to that of zircons from ortho-and paragneisses of the UGU and LGU in the FMC 438 Int J Earth Sci (Geol Rundsch) (2017) 106:421-451 1 3 (Melleton et al. 2010;[START_REF] Chelle-Michou | New U-Pb and Hf zircon data from the eastern Massif Central: from Gondwana to Pangea in a nutshell[END_REF], which are the country rocks and, most likely, the sources of CPG and MPG (Williamson et al. 1996(Williamson et al. , 1997;;Downes et al. 1997;Barbey et al. 1999[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]. Thus, it is clear that these zircons were inherited from the regional nappe units, either during melting or emplacement.

The observed age spectrum is very similar to the age distribution of detrital zircons from many Paleozoic (Cambrian to Devonian) sedimentary rocks throughout western Europe (Zeh et al. 2001;[START_REF] Kober | SHRIMP dating of zircons from high-grade metasediments of the Schwarzwald/SW-Germany and implications for the evolution of the Moldanubian basement[END_REF]Linnemann et al. 2004[START_REF] Linnemann | The continuum between Cadomian orogenesis and opening of the Rheic Ocean: Constraints from LA-ICP-MS U-Pb zircon dating and analysis of plate-tectonic setting (Saxo-Thuringian zone, northeastern Bohemian Massif, Germany)[END_REF]Linnemann et al. , 2014;;Gerdes and Zeh 2006) and has also been reported in inherited zircons from Variscan granites of the Iberian Massif (Castiñeiras et al. 2008;[START_REF] Fernández-Suárez | Iberian late-Variscan granitoids: some considerations on crustal sources and the significance of "mantle extraction ages[END_REF]. This age distribution is generally interpreted to reflect zircon derived from the Avalonian-Cadomian belt (and its cratonic hinterland), forming a ca. 10,000-km-long cordillera at the northern margin of Gondwana during Neoproterozoic to Cambrian times (see Nance et al. 1991;Nance and Murphy 1994;Fernández-Suárez et al. 2000;Zeh et al. 2001;Linnemann et al. 2014;and references therein). During the early Ordovician (490-470 Ma), this cordillera became dispersed, with individual microterranes (e.g., Avalonia, Amorica, Alpine terranes, etc.) drifting to the north and re-assembled subsequently during the Variscan orogeny at 360-320 Ma [START_REF] Nance | A Cordilleran model for the evolution of Avalonia[END_REF][START_REF] Von Raumer | Organization of pre-Variscan basement areas at the north-Gondwanan margin[END_REF][START_REF] Linnemann | The continuum between Cadomian orogenesis and opening of the Rheic Ocean: Constraints from LA-ICP-MS U-Pb zircon dating and analysis of plate-tectonic setting (Saxo-Thuringian zone, northeastern Bohemian Massif, Germany)[END_REF]Faure et al. 2009;Stampfli et al. 2013). The age peaks of the inherited zircons from the eastern FMC granitoids can be ascribed to several well-known events throughout this evolution, notably the formation of an arc-back-arc system at ca. 660-560 Ma; its evolution into an Andean-type continental margin at 550-530 Ma and its subsequent breakup at 530-480 Ma, resulting in the opening of the Rheic Ocean (see Ballèvre et al. 2001;[START_REF] Nance | A Cordilleran model for the evolution of Avalonia[END_REF]Nance et al. , 2010;;Linnemann et al. 2004, 2007 andreferences therein). The two youngest peaks at middle Devonian (390-370 Ma) and early Carboniferous ages (360-340 Ma) correspond respectively to subduction processes related to the closure of the Rheic Ocean [START_REF] Zeh | Baltica-and Gondwana-derived sediments in the Mid-German Crystalline Rise (Central Europe): Implications for the closure of the Rheic ocean[END_REF] and to the Variscan collision (Faure et al. 2009). The latter period is characterized by important crustal melting, granulite-facies metamorphism (Duthou et al. 1994;[START_REF] Gardien | Thermal maturation and exhumation of a middle orogenic crust in the Livradois area (French Massif Central)[END_REF]) and emplacement of arc-like, calc-alkaline gabbros and granitoids in the Morvan and Limousin areas (Bernard-Griffiths et al. 1985;Pin and Paquette 2002).

Zircon constraints on granitoid petrogenesis

Zircon constraints on CPG and MPG petrogenesis

These granitoids contain abundant, rounded to subhedral zircon cores with pre-Variscan ages, commonly wrapped by rims formed during the Variscan magmatic episode (Figs. 3,6 and 7). These characteristics are in good agreement with previous interpretation that the MPG and CPG are of crustal origin (Williamson et al. 1996(Williamson et al. , 1997;;Downes et al. 1997;Barbey et al. 1999) and formed at relatively low temperatures, specifically below magmatic Zr saturation. Considering that the pre-Variscan zircons in CPG and MPG were inherited from the source rock during melting, Zr saturation temperatures would provide a first-order estimate of maximum magma temperatures. These temperatures, calculated using the Zr saturation thermometer of Watson and Harrison (1983), are in the range 720-787 °C for the MPG and 761-842 °C for CPG (Fig. 8). Such values are consistent with results of previous melting experiments carried on metasedimentary rocks at mid-crustal pressures [START_REF] Vielzeuf | Experimental determination of the fluid-absent melting relations in the pelitic system[END_REF][START_REF] Patiño-Douce | Phase equilibria and melt productivity in the pelitic system: implications for the origin of peraluminous granitoids and aluminous granulites[END_REF][START_REF] Gardien | Experimental melting of biotite + plagioclase + quartz ± muscovite assemblages and implications for crustal melting[END_REF][START_REF] Patiño-Douce | Experimental constraints on Himalayan anatexis[END_REF][START_REF] Pickering | Fluid-absent melting behavior of a two-mica metapelite: experimental constraints on the origin of black hills granite[END_REF], which produced granitic liquids that match the compositions of CPG and MPG at 700-850 °C (Fig. 8). The generally lower Zr saturation (1995,1996), Patiño-Douce and Johnston (1991), [START_REF] Pickering | Fluid-absent melting behavior of a two-mica metapelite: experimental constraints on the origin of black hills granite[END_REF], [START_REF] Vielzeuf | Experimental determination of the fluid-absent melting relations in the pelitic system[END_REF] and Vielzeuf and Montel (1994) for metasediments; [START_REF] Beard | Dehydration melting and water-saturated melting of basaltic and andesitic greenstones and amphibolites at 1, 3 and 6.9 kb[END_REF], [START_REF] Bogaerts | Phase Equilibria of the Lyngdal Granodiorite (Norway): Implications for the Origin of Metaluminous Ferroan Granitoids[END_REF], Patiño-Douce and [START_REF] Patiño-Douce | Dehydration-melting of biotite gneiss and quartz amphibolite from 3 to 15 kbar[END_REF], Rapp and Watson (1995), [START_REF] Rapp | Partial melting of amphibolite/eclogite and the origin of Archaean trondhjemites and tonalites[END_REF], [START_REF] Singh | Dehydration melting of tonalites. 2. Compositions of melts and solids[END_REF], Sisson et al. (2005), [START_REF] Skjerlie | Vapour-absentmelting from 10 to 20 kbar of crustal rocks that containmultiple hydrous phases: implications for anatexis in the deep to very deep continental crust and active continental margins[END_REF]; [START_REF] Tatsumi | Tholeiitic versus calc-alkalic differentiation and evolution of arc crust: constraints from melting experiments on a basalt from the Izu-Bonin-Mariana Arc[END_REF], [START_REF] Watkins | Archaean TTGs as sources of younger granitic magmas: melting of sodic metatonalites at 0.6-1.2 GPa[END_REF] and Wolf and Wyllie (1994) for igneous rocks. The arrows associated with the symbols indicate whether the calculated T Zr sat represents maximum magma temperatures (arrow down, if source-inherited zircons are present) or minimum ones (arrow up, few or no inherited zircons)

1 3

temperatures obtained for the MPG could be explained either by water-present melting (Williamson et al. 1996) or muscovite breakdown melting (720-770 °C at 7 kbar; Patiño-Douce and Harris 1998). In contrast, the higher temperatures obtained for the CPG exceed that of muscovite dehydration melting and thus require biotite dehydration melting (800-870 °C; Vielzeuf and Montel 1994;Patiño-Douce andBeard 1995, 1996), in good agreement with the previous interpretations of Barbey et al. (1999[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF] and Moyen et al. (in press).

On the other hand, the respective contribution of pre-Variscan ortho-and paragneisses of the FMC in the source of MPG and CPG is the matter of several discussions (Turpin et al. 1990;Williamson et al. 1996Williamson et al. , 1997;;Downes et al. 1997;Moyen et al. in press). It is worthwhile noting that ortho-and paragneisses of the FMC reveal important differences in their age spectra. Zircon grains from the orthogneisses show two prominent age peaks at ~475 Ma (early Ordovician) and ~540 Ma (early Cambrian) (Fig. 9a), corresponding to the magmatic ages of their respective protoliths (Caen-Vachette 1979;Pin and Lancelot 1982;Duthou et al. 1984;Lafon 1986;[START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF]Alexandrov et al. 2001;Alexandre 2007;Melleton et al. 2010;[START_REF] Chelle-Michou | New U-Pb and Hf zircon data from the eastern Massif Central: from Gondwana to Pangea in a nutshell[END_REF][START_REF] Mintrone | Le Massif Central avant la chaîne Varisque: caractérisation des orthogneiss du début du Primaire[END_REF], whereas detrital zircons from the paragneisses show the same peak at 475 Ma, in addition to a wide Neoproterozoic age cluster between 560 and 650 Ma, with a distinctive "tail" until 1000 Ma (Fig. 9b) (Melleton et al. 2010;[START_REF] Chelle-Michou | New U-Pb and Hf zircon data from the eastern Massif Central: from Gondwana to Pangea in a nutshell[END_REF]. The inherited zircon age spectra of both CPG and MPG (Fig. 9c,d) are intermediate between those two end-members, with a prominent age peak at ~540 Ma like in orthogneisses together with a significant number of Neoproterozoic zircon grains (mostly at 560-650 and up to 1000 Ma), typical of paragneisses (Fig. 9c,d).

A striking difference, though, is the limited number of Ordovician (~475 Ma) inherited zircons in the CPG and MPG, as already noted in the case of the Velay granite (Couzinié et al. 2014;[START_REF] Chelle-Michou | New U-Pb and Hf zircon data from the eastern Massif Central: from Gondwana to Pangea in a nutshell[END_REF]. It must be emphasized that the age spectra presented in Fig. 9 for the MCF ortho-and paragneisses result from the compilation of data from all lithostratigraphic units (PAU, UGU, LGU) and both the eastern and western parts of the FMC. In fact, there are clear differences in the zircon age distributions between the UGU and LGU in the eastern FMC, the most relevant one being that Ordovician ages are restricted to the UGU and LAC (Pin 1979a;Pin and Lancelot 1982;[START_REF] Chelle-Michou | New U-Pb and Hf zircon data from the eastern Massif Central: from Gondwana to Pangea in a nutshell[END_REF] whereas in the LGU, both the youngest detrital zircon grains in paragneisses and the magmatic protoliths of orthogneisses have Cambrian ages at 545-520 Ma (Caen-Vachette 1979;Duthou et al. 1984;[START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF][START_REF] Chelle-Michou | New U-Pb and Hf zircon data from the eastern Massif Central: from Gondwana to Pangea in a nutshell[END_REF][START_REF] Mintrone | Le Massif Central avant la chaîne Varisque: caractérisation des orthogneiss du début du Primaire[END_REF]. We therefore interpret the limited number of Ordovician inherited zircons from the CPG and MPG to reflect a source region rooted in the LGU, where zircons younger than 520 Ma are scarce.

All lines of evidence suggest that the source of both CPG and MPG consists of a mixed assemblage of para-and orthogneisses from the LGU. The CPG (including the Velay granite) formed by biotite dehydration melting at high temperature (≥800 °C), whereas MPG formed at lower temperature (<800 °C) through muscovite breakdown or waterpresent melting.

Zircon constraints on KCG and vaugnerite petrogenesis

Xenocrysts in KCGs and vaugnerites are very scarce (n = 9, among 21 samples). The estimated Zr saturation temperatures for these rocks are ≤850 °C (Fig. 8), i.e., much lower than presumed magma temperature for vaugnerites (>1000 °C; Montel and Weisbrod 1986), which may indicate that potential zircon xenocrysts in the magma were dissolved because of Zr undersaturation. These potential xenocrysts were probably assimilated from the wallrock in which the mafic magma percolated (e.g., in sample SC- [13][14], rather than inherited from a crustal source. These magmas indeed have "crust-like" trace element and Nd-Hf isotopic compositions, yet their very high FeO t + MgO (most often >10 wt%; Fig. 8) and low SiO 2 contents preclude either a crustal origin or crustal contamination of a basaltic melt (Turpin et al. 1988;Couzinié et al. 2016). Instead, vaugnerites are more likely to be derived from an "enriched" mantle source metasomatized by 10-25% of crust-derived materials (see Couzinié et al. 2016 for a more detailed discussion about the origin of these rocks).

A crust-dominated origin for the KCGs is precluded by their high FeO t + MgO contents (>6 wt%) that would require an igneous mafic source (amphibolites, which are scare in the LGU) and melting temperatures ≥950 °C (Fig. 8) that are unrealistically high (Moyen et al. in press). These observations could indicate that KCG derive from interactions (mixing, mingling) between Zr-saturated crustal melts (similar to CPG and MPG) and a hot, mantle-derived, Zr-undersaturated vaugnerite magma (Downes et al. 1997;[START_REF] Solgadi | The relative roles of crustal anatexis and mantle-derived magmas: generation of Synorogenic, Hercynian granites in the Livradois area, French Massif Central[END_REF], thereby triggering the partial to total dissolution of inherited zircons. Such mixing between vaugnerites and CPG/MPG is supported by the intermediate composition of KCG between the two end-members (Figs. 2,8). Alternatively, the high SiO 2 content of the KCG (~69 wt%) could be explained also by a high degree of fractionation of vaugnerite magma, in agreement with the close spatial and petrographic relationships between these rocks (Barbarin 1988) and geochemical constraints (Moyen et al. in press). In either case, the involvement of mantle-derived, vaugnerite magma is required to explain the composition of the KCG.

The Carboniferous thermal anomaly in the eastern FMC: evidence for lithospheric mantle delamination

Our new geochronological data indicate that the late-Variscan plutonic rocks of the eastern FMC emplaced between ~339 and ~298 Ma (when uncertainties are considered) (Fig. 10). This dataset thus represents the first, self-consistent and unambiguous evidence that magmatic activity lasted throughout the entire late Carboniferous for ~40 Ma, as proposed by earlier studies [START_REF] Vanderhaeghe | Exhumation of migmatites in two collapsed orogens: Canadian cordillera and French Variscides[END_REF]Vanderhaeghe and Teyssier 2001;Ledru et al. 2001;[START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF]Faure et al. 2009). The estimated timescales for the magmatism in the FMC are much longer than those assessed for the evolution of magma from source to emplacement (production, segregation, ascent and crystallization) that commonly lasts no more than 5 Ma (Harris et al. 2000;[START_REF] Petford | Granite magma formation, transport and emplacement in the Earth's crust[END_REF]Annen et al. 2006;[START_REF] Walker | Geology and geochronology of the Spirit Mountain batholith, southern Nevada: implications for timescales and physical processes of batholith construction[END_REF][START_REF] Saint-Blanquat | Multiscale magmatic cyclicity, duration of pluton construction, and the paradoxical relationship between tectonism and plutonism in continental arcs[END_REF]. Thus, the ~40-Ma-long magmatism necessarily implies the existence of a long-lived thermal anomaly, to sustain a high heat flux and crustal anatexis throughout the Carboniferous [START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF][START_REF] Vanderhaeghe | The thermal-mechanical evolution of crustal orogenic belts at convergent plate boundaries: a reappraisal of the orogenic cycle[END_REF].

In fact, such a protracted Carboniferous thermal anomaly in the eastern FMC was already suggested on the basis of studies on metamorphic rocks, indicating an early, M 3 -metamorphic episode characterized by incipient partial melting of the metamorphic nappe pile at P-T conditions of 5-6 kbar and 720-750 °C between ~330 and ~310 Ma (Montel et al. 1992;Mougeot et al. 1997;Barbey et al. 1999[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Cocherie et al. 2005;Bé Mézème et al. 2006;Bouilhol et al. 2006), followed by biotite dehydration melting at P-T conditions of 4-5 kbar and 750-850 °C at 305-301 Ma (M 4 -metamoprhic episode; [START_REF] Caen-Vachette | Ages radiométriques des granites anatectiques et tardimigmatitique du Velay (Massif Central français)[END_REF]Montel et al. 1992;Mougeot et al. 1997;Barbey et al. 1999[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Couzinié et al. 2014). The M 4 event required a higher apparent geothermal gradient than the M 3 episode and corresponds to the formation of the Velay granite-migmatite dome. In the past, limited partial melting during the M 3 episode 1 3 has been attributed mainly to enhanced radioactive heat production, due to accumulation of radioactive elements in the over-thickened orogenic crust (e.g., [START_REF] Vanderhaeghe | Exhumation of migmatites in two collapsed orogens: Canadian cordillera and French Variscides[END_REF][START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF], possibly coupled to limited heat advection from the intrusion of vaugnerites. The higher, apparent geothermal gradient during the M 4 episode was assumed to result from two factors: first, the transfer of magmas from lower/middle to upper crustal levels during the formation of the Velay dome [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF], and second, the emplacement of mantlederived (vaugnerite) melts (Williamson et al. 1992(Williamson et al. , 1997;;Ledru et al. 2001;[START_REF] Rossi | Les magmatismes paléozoïques. La chaîne Varisque[END_REF]. ,8). The groups of samples (CPG, MPG, KCG and vaugnerites) are sorted according to the respective contribution of crustal and mantle sources to their petrogenesis (see "Discussion"). On the right-hand side are represented major time markers in the Variscan evolution of the eastern FMC, including collision-related M 2 metamorphism [START_REF] Gardien | Reliques de grenat et de staurotide dans la série métamorphique de basse pression du Mont Pilat (Massif Central français) : témonis d'une évolution tectonométamorphique polyphasée[END_REF]Caron 1994;Faure et al. 2009;[START_REF] Melleton | Monazite U-Th/Pb chemical dating of the Early Carboniferous syn-kinematic MP/MT metamorphism in the Variscan French Massif Central[END_REF]Schulz 2014), the two anatectic episodes M 3 and M 4 -the latter being related to the development of the Velay dome (Montel et al. 1992;Barbey et al. 1999[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Couzinié et al. 2014) and development of "Stephanian" (upper Pennsylvanian), intramontane coal-bearing basins [START_REF] Malavieille | Collapse of the thickened Variscan crust in the French Massif Central: Mont Pilat extensional shear zone and St. Etienne Late Carboniferous basin[END_REF]Faure et al. 2009) Three problems, however, rise from these hypotheses:

1. As pointed out by [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF], M 3 melting was necessarily more intense in the lower crust than it is recorded at the present level of exposure, in order to explain the formation and emplacement of the widespread 337-312-Ma-old CPG plutons (Fig. 10) for the origin of which biotite dehydration melting (T > 800 °C) is required.

The geochronological data obtained in this study

show that vaugnerites ± KCG (338-298 Ma) and CPG + MPG (339-302 Ma) emplaced synchronously throughout the Carboniferous (Fig. 10), rather than successively, as would be expected if crustal melt production was caused by mafic magmatic underplating (first vaugnerites ± KCG, second CPG + MPG ± KCG). 3. Thermal modeling indicates that crustal melt productivity induced by heat advection from the intrusion or underplating of mantle-derived basalt rarely exceeds 10% of the whole volume of mafic magma (Petford and Gallagher 2001;[START_REF] Annen | Eects of repetitive emplacement of basaltic intrusions on thermal evolution and melt generation in the crust[END_REF]Annen et al. 2006). This entails that the volume of basalt must have been nine times larger than the final volume of crust-derived granites. In the case of the eastern FMC, such a high ratio appears unrealistic because vaugnerites are largely subordinate in volume relative to the granites (Couzinié et al. 2016). There is evidence from lower crustal xenoliths brought up by Cenozoic volcanoes that mafic igneous rocks are present in the lower crust of the eastern FMC [START_REF] Dostal | Geochemistry and petrology of meta-igneous granulitic xenoliths in Neogene volcanic rocks of the Massif Central, France-implications for the lower crust[END_REF]Downes et al. 1990). However, available age constraints on these rocks suggest that they would represent a Permian (300-250 Ma-old) underplating event (Supply 1981;[START_REF] Costa | Lower crustal rejuvenation and growth during post-thickening collapse: insights from a crustal cross section through a Variscan metamorphic core complex[END_REF]Féménias et al. 2003) and could therefore not be responsible for the heat anomaly at the origin of Carboniferous magmatism.

Thus, mantle-derived magmas unlikely represent the main heat source for crustal melting and the genesis of the voluminous CPG and MPG, during neither M 3 , nor M 4 , and an alternative hypothesis must be sought. The close association in both space and time of crust-derived granites and vaugnerites in the eastern FMC suggests that they are all the "byproducts" of one-and-the-same, lithospheric-scale geodynamic process. This process would be ideally represented by lithospheric mantle delamination, accompanied by the ascent of hot (>1200 °C) asthenospheric mantle up to the crust-mantle boundary (Moho). Thermo-mechanical modeling (van Hunen and Allen 2011; [START_REF] Duretz | Slab detachment during continental collision: influence of crustal rheology and interactions with lithospheric delamination[END_REF][START_REF] Magni | Delamination versus break-off: the fate of continental collision[END_REF]) and geological observations from other orogenic systems (Black and Liégeois 1993;[START_REF] Coulon | Post-collisional transition from calc-alkaline to alkaline volcanism during the Neogene in Oranie (Algeria): magmatic expression of a slab breakoff[END_REF][START_REF] Guo | Post-collisional, K-rich mafic magmatism in south Tibet: constraints on Indian slab-to-wedge transport processes and plateau uplift[END_REF]Laurent et al. 2014b) show that this process is common at the final stages of continental collision. Lithospheric mantle delamination was also suggested to explain the Carboniferous record in other parts of the Variscan belt [START_REF] Henk | Syn-convergent high temperature metamorphism and magmatism in the Variscides: a discussion of potential heat sources[END_REF][START_REF] Von Raumer | Durbachites-Vaugnerites-a geodynamic marker in the central European Variscan orogen[END_REF]Denèle et al. 2014) and is backed by geophysical data, since the mantle underneath the eastern FMC is characterized by low P-wave velocities interpreted as reflecting the removal of the Variscan orogenic roots (Averbuch and Piromallo 2012). Thermal modeling demonstrated that an anomalously high heat flux through the Moho (equivalent to that of the convective mantle) triggers widespread lower crustal melting and magma transfer to the middle crust, accounting for high geothermal gradients and granulitefacies metamorphism (apparent geotherm of >50 °C km -1 ) within 25-35 Ma [START_REF] Depine | Near-isothermal conditions in the middle and lower crust induced by melt migration[END_REF]. The increase in temperature is maximum in the case of conjunct crustal thickening enhancing radioactive heating and thinning of the lithospheric mantle causing an increase of the heat flux at the base of the crust [START_REF] Vanderhaeghe | Crustal-scale mass transfer, geotherm and topography at convergent plate boundaries[END_REF]. This scenario is very consistent with geological and geochronological data from the eastern FMC showing the same incubation time between the intrusion of the first vaugnerites and granites at about 337 Ma and the rise of the Velay granite-migmatite dome at 310-300 Ma (Fig. 10) associated with the apparently higher-temperature "M 4 " episode.

Consequences for the Variscan tectonic evolution of the eastern FMC

The magmatic rocks in the eastern FMC reveal a clear temporal vs. spatial evolution (Fig. 11). All magma types (CPG, MPG, KCG and vaugnerites) can indeed be found throughout the entire FMC, but their emplacement ages decrease systematically from north to south between 340 and 305 Ma (Fig. 11). The CPGs, KCGs and vaugnerites in the northernmost part of the FMC (Forez, Livradois and Lyonnais mountains) emplaced at 337 to 330 Ma; the youngest intrusion is represented by the Hermitage MPG pluton at ~326 Ma (Fig. 11). Further south, the CPG laccoliths that flank both the eastern (Tournon, Dunières) and western (Chaise-Dieu, Almance) sides of the Velay dome, as well as the large enclaves of CPG, KCG and vaugnerites in the latter, emplaced between 332 and 315 Ma, mostly at 320 Ma (Fig. 11). The Margeride batholith at the SW end of the Velay dome (the Margeride granite itself plus associated MPG and vaugnerites) intruded at 313-309 Ma; and finally, emplacement of the KCG plutons and abundant vaugnerites in the southernmost Cévénnes domain took place at even younger ages of 307-298 Ma (Fig. 11).

We propose that the observed zonal pattern results from the progressive, southward migration of the thermal anomaly, which was responsible for coeval and protracted crustand mantle-derived magmatism. This migrating thermal anomaly can be explained by asymmetric delamination of 1 3 the subcontinental lithospheric mantle beneath the FMC, starting to the north and propagating southwards. Heat conduction from the inflowing asthenosphere triggered the partial melting of the lithospheric mantle enriched in incompatible elements during previous subduction (Couzinié et al. 2016;[START_REF] Von Raumer | Durbachites-Vaugnerites-a geodynamic marker in the central European Variscan orogen[END_REF]) and caused formation of modest volumes of vaugnerite magmas. Such lithospheric mantle source could have either been part of the delaminating slab or represented by slivers that remained mechanically coupled to the lower crust during delamination. Concurrently, enhanced mantle heat flux through the Moho caused widespread lower crustal melting and the formation of granitic magmas (CPG + MPG). Interactions between those two magmatic end-members, and/or differentiation of vaugnerite magmas, led to the formation of KCG.

On the other hand, the granites and migmatites forming the core of the Velay complex span nearly the entire area covered by the other intrusions, but in contrast to the latter reveal no age zoning. These rocks rather crystallized within a short period of time at 305-300 Ma, regardless the latitude (Fig. 11). Our new age of 302.8 ± 1.3 Ma from the Pont-Rouge quarry, in the central-northern part of the dome, is indeed within uncertainties of, or very close to, the monazite U-Pb ages of 301 ± 5 (Mougeot et al. 1997), 303.7 ± 3.1 and 305.9 ± 1.4 Ma (Couzinié et al. 2014) from its southern part; and the zircon U-Pb ages of 307.5 ± 2.0 Ma (Chelle-Michou et al. 2015) and 304 ± 4 Ma [START_REF] Be Mezeme | Structural, AMS and geochronological study of a laccolith emplaced during Late Variscan orogenic extension: the Rocles pluton (SE French Massif Central)[END_REF]) obtained in the eastern and northern edges of the complex, respectively. The lack of "age zoning" in the Velay dome at the temporal resolution of existing data suggests that it represents a partially molten, middle to lower crustal layer rapidly exhumed during the late Carboniferous [START_REF] Vanderhaeghe | Exhumation of migmatites in two collapsed orogens: Canadian cordillera and French Variscides[END_REF]. Prolonged lower to middle crust melting started above the widening "asthenospheric window," which was formed during progressive southward lithospheric mantle delamination. This caused a rheologic weakening of the lower crust, which eventually led to lateral crustal flow, thinning and collapse of the orogenic crust, and the exhumation of the partially molten crust in the core of domes like the Velay complex (Vanderhaeghe and Teyssier 2001;[START_REF] Vanderhaeghe | The thermal-mechanical evolution of crustal orogenic belts at convergent plate boundaries: a reappraisal of the orogenic cycle[END_REF]. In this perspective, the 305-300 Ma age cluster obtained in the Velay granite and migmatites does not necessarily correspond to a "catastrophic" melting event (Couzinié et al. 2014). Instead, it simply reflects the final exhumation and cooling of these rocks below their solidus, as a natural outcome of the whole delamination process.

The occurrence of southward lithospheric mantle delamination in the eastern FMC during the Carboniferous can be considered in the scope of existing geodynamic scenarios for this part of the Variscan belt. Faure et al. (2009) stressed out that there are two possible, competing models that may explain the present-day structure of the FMC: 1. A "monocyclic" model (e.g., Lardeaux et al. 2001) considering a single, northward-directed subduction from the Silurian to the late Devonian. In this context, the suggested southwards lithospheric delamination wit-nessed by the Carboniferous magmatic evolution could simply reflect the rollback of the lithospheric mantle (Fig. 12a), in response to decoupling with the overlying continental crust while convergence was still active [START_REF] Vanderhaeghe | Crustal-scale mass transfer, geotherm and topography at convergent plate boundaries[END_REF][START_REF] Duretz | Slab detachment during continental collision: influence of crustal rheology and interactions with lithospheric delamination[END_REF][START_REF] Magni | Delamination versus break-off: the fate of continental collision[END_REF]). 2. A "polycyclic" model (e.g., Faure et al. 2005) in which northward-directed subduction during the Ordovician and early Silurian ("Eo-Variscan" cycle, Armorica-Gondwana collision) was followed by Devonian, southward-directed subduction that accommodated the closure of the Rheic Ocean ("Variscan" cycle, Laurussia-[Armorica + Gondwana] collision). In this case, thermo-mechanical models of mature continental collision suggest that if the lithospheric mantle of the lower (i.e., subducting) plate is retreating, it causes a "retro-delamination" of the lithosphere underneath the overriding plate and asthenospheric upwelling [START_REF] Gray | Geodynamic models of mature continental collision: evolution of an orogen from lithospheric subduction to continental retreat/delamination[END_REF], equally accounting for southward lithosphere delamination under the eastern FMC (Fig. 12b). The two models have their strengths and weaknesses.

Morvan

The "monocyclic" model (Fig. 12a) is supported by the presence of (U)HP rocks at the base of the UGU (late Devonian migmatites with embedded eclogite boudins) that would represent remnants of the northward-subducted oceanic and continental crust (Lardeaux et al. 2001). Moreover, the rheological weakening and buoyancy of partially molten, subducted continental crust strongly enhances its decoupling with the lithospheric mantle and subsequent exhumation, as typically observed in numerical models [START_REF] Duretz | Slab detachment during continental collision: influence of crustal rheology and interactions with lithospheric delamination[END_REF] and natural case studies [START_REF] Labrousse | Continental exhumation triggered by partial melting at high pressure[END_REF]). This would have readily triggered southward delamination of the lithospheric mantle in the context of ongoing convergence, which is supported by the fact that the orogenic front propagated southwards during the Carboniferous (Faure et al. 2009). However, the timing of exhumation of the (U)HP rocks at the base of the UGU is poorly constrained and could be as early as 360 Ma (Lardeaux et al. 2001). Thus, if this hypothesis was correct, there is a time lapse of ≥20 Ma between the end of continental subduction and the beginning of magmatism related to delamination (~340 Ma in the eastern FMC), which is difficult to explain since the response time between delamination and melting of the crust through asthenospheric heat advection would be much shorter, i.e., ≤10 Ma (Arnold et al. 2001;[START_REF] Depine | Near-isothermal conditions in the middle and lower crust induced by melt migration[END_REF].

On the other hand, the "polycyclic" model involving southward subduction during the Devonian (Fig. 12b) is consistent with arc magmatism in the Morvan and Limousin areas at 360-350 Ma and the development of the Brévenne trough as a back-arc basin (Pin and Paquette 1997;Faure et al. 2009;Lardeaux et al. 2014). It also avoids the problem of a too long time lapse between the onsets of delamination and magmatism: "retro-delamination" starting at ~350 Ma (the youngest documented subductionrelated magmas being dated at 355 ± 2 Ma; Bernard-Griffiths et al. 1985) more realistically accounts for the onset of widespread magmatism at ~340 Ma in the eastern FMC. Nevertheless, this scenario implies that the asthenosphere window underneath the crust would have been much larger than in the previous one, specifically extending further north beyond the Brévenne basin, up to the Morvan area (Fig. 12b). This is problematic because in these domains, there is so far no evidence for any sequential emplacement of igneous rocks like that documented here, or even for any magmatic event younger than ~330 Ma.

More detailed investigations are therefore required to decipher between these two scenarios; at present we consider that both are equally likely to explain the observed southward lithosphere delamination and associated magmatism in the eastern FMC during the Carboniferous.

Conclusions

Variscan plutonic rocks from the eastern FMC were derived from two end-member sources: (i) a mixture of felsic lithologies (ortho-and paragneisses) from the local nappe pile (especially the Lower Gneiss Unit, in line with the predominance of late Ediacaran to early Cambrian ages in inherited zircon patterns), resulting in the formation of cordierite-and muscovite-bearing peraluminous granites (CPG and MPG); and (ii) an enriched (metasomatized) lithospheric mantle, source of the vaugnerites. The K-feldspar porphyritic, calc-alkaline granites and granodiorites (KCG) result from either interactions between these two end-members or fractionation from vaugnerite magmas.

Zircon and monazite U-Pb ages from these rocks testify for a long-lasting (~40 Ma) period of crust-and mantlederived magmatism in the eastern FMC, as is reflected by the coeval emplacement of granites between 337.4 ± 1.0 and 298.9 ± 1.8 Ma, and vaugnerites between 335.7 ± 2.1 and 299.1 ± 1.3 Ma. Coeval and protracted crust-and mantle-derived magmatism points to the existence of a longlived lithospheric-scale thermal anomaly, which probably formed in response to the delamination of the lithospheric mantle and asthenosphere upwelling beneath the eastern FMC during the late Carboniferous. Moreover, the spatial distribution of the dated samples indicates that delamination started at about 340 Ma in the northern part of the area and propagated southwards until 300 Ma. This may be explained either by (i) the progressive "retreat" of a lithospheric mantle slab following northward-directed subduction or (ii) "retro-delamination" of the lithosphere associated with southward-directed subduction. N45 dextral strike-slip shear zones (Feybesse et al., 1995;Gay et al., 1981). Those granitoids are of primary interest as they mark the latest stage of regional polyphase ductile deformation, thought to have occured at T < 600°C, and thus post-date eclogite-, granulite-and amphibolite-facies metamorphism [START_REF] Costa | 40 Ar 39 Ar chronology of Variscan tectonometamorphic events in an exhumed crustal nappe: the Monts du Lyonnais complex (Massif Central, France)[END_REF]Feybesse et al., 1995;Gardien et al., 1990;[START_REF] Lardeaux | Granulites à kornérupine et décompression postorogénique des Monts du Lyonnais (M.C.F.)[END_REF]2001).

Therefore, determination of their emplacement age would provide critical constrains on the P-T-t paths experienced by the Upper Gneiss Unit in the Monts-du-Lyonnais area. ArAr dating of biotite and muscovite yielded cooling ages in the range 345340

Ma [START_REF] Costa | 40 Ar 39 Ar chronology of Variscan tectonometamorphic events in an exhumed crustal nappe: the Monts du Lyonnais complex (Massif Central, France)[END_REF] slightly older than the age obtained via the whole-rock RbSr geochronometer (332 ± 10 Ma, Gay et al., 1981). Section 5.1 presents new geochronological data from vaugnerites closely associated with the synkinematic granitoids and regarded as coeval by Michon (1979) and Sabatier (1984). The inferred zircon UPb emplacement ages of 335.7 ± 2.1 and 333.9 ± 1.4 are in better agreement with the RbSr results. To clarify the actual age of synkinematic magmatism, an additional granitoid sample was collected for zircon UPb age determination. Sample RV-3 was taken from in the former Riverie quarry at the place known as "Les Roches" (see Part I). It corresponds to a 10-cm thick biotite-bearing granite vein concordant in the foliation of amphibolebearing gneisses. Constituent minerals are Qz, Pg (An 2 5, see Appendix Table B3), Kfs and Bt. Amphibole is typically lacking.

Polished 150 µm-thick sections were made and zircon identied by making automated Zr maps using a Merlin SEM at SUN. UPb dating was conducted in situ on the thick sections after BSECL imaging of the previously located grains (using the same SEM).

Zircon grains are very small, often < 60 µm in length, and show a broad range of aspect ratios, from 1:2 to 1:9. Inherited cores are extremely scarce and, when observed, CLbrighter than the rims. The latter often display typical oscillatory zoning even though a few grains appear homogeneous.

UPb results and emplacement age

LAICPMS UPb dating was conducted at SUN with a spot diameter of 20 µm (26th of October 2016, with the assistance of Riana Rossouw, see Appendix B.3.2 for analytical procedures and Tables B5 andB8

Conclusion

This newly obtained emplacement age conrms that: (i) vaugnerites and granites from the southern Monts-du-Lyonnais area are coeval; (ii) the late increment of deformation, probably at the origin of the N45-trending regional foliation, is as young as c. 335 Ma and post-dates peak metamorphism which age has been independently estimated in this same outcrop at c. 360 Ma (see Part I).

Introduction

The formation of the continental crust is a major consequence of planetary differentiation and played a key role in the evolu-tion of climate and life (Campbell and Allen, 2008;[START_REF] Lowe | Geologic evidence for Archean atmospheric and climatic evolution: fluctuating levels of CO 2 , CH 4 , and O 2 with an overriding tectonic control[END_REF]. The mechanisms and rates of continental formation are therefore fundamental parameters to be addressed and have long been a matter of controversy [START_REF] Arndt | Formation and evolution of the continental crust[END_REF]Hawkesworth et al., 2010). The formation of new continental crust requires two fundamental conditions to be fulfilled, regardless of the tectonic setting in which it takes place: (1) genesis (and differentiation) of mantle-derived igneous material; and (2) long-term incorporation and preservation of this material into the pre-existing continen- tal volume (Condie et al., 2011;Hawkesworth et al., 2009;Stern and Scholl, 2010). Radiogenic isotope systems like Rb/Sr, Sm/Nd and Lu/Hf are extensively used to track crust-forming events, and it is consensually assumed that the radiogenic isotope composition of newly-formed crust is identical to that of the depleted mantle (DM) [START_REF] Mcculloch | Sm-Nd and Rb-Sr chronology of continental crust formation[END_REF][START_REF] Patchett | Evolution of continental crust and mantle heterogeneity: evidence from Hf isotopes[END_REF]Vervoort and Blichert-Toft, 1999).

In this respect, the study of continental growth recently benefited from advances in analytical techniques enabling in situ isotopic measurements in zircon, a widespread accessory mineral of continental igneous rocks. Because zircon is able to survive several metamorphic, igneous and sedimentary cycles and contains a wealth of isotopic information (U-Pb, Lu-Hf, O isotopes), it represents an outstanding archive of crust formation and evolution (Bouilhol et al., 2013;[START_REF] Bouilhol | Timing of juvenile arc crust formation and evolution in the Sapat Complex (Kohistan-Pakistan)[END_REF]Condie et al., 2011;[START_REF] Roberts | The zircon archive of continent formation through time[END_REF]. The analyses of U-Pb and Lu-Hf isotope compositions within the same zircon give access to both the age and the Hf isotopic signature of the magma in which it crystallized (Griffin et al., 2002;Woodhead et al., 2004). The latter is converted into a crustal residence ("model") age corresponding to the time at which the crustal source of the zirconhosting magma would have been extracted from the DM (Kemp et al., 2006). The coupled analysis of O isotopes has been proposed to discriminate between zircons crystallized from magmas having a sedimentary source (δ 18 O > 6.5h; Kemp et al., 2006;Valley et al., 1998) and thus, meaningless "mixed" model ages (Arndt and Goldstein, 1987), from those having an ultimately mantle-derived source (δ 18 O ∼ 5.5 ± 1.0h) and supposed to yield reliable model ages (Hawkesworth and Kemp, 2006). Accordingly, statistical analyses of U-Pb-Hf(-O) isotopic databases from both igneous and detrital zircons were extensively used to quantify the timing, amount and mechanisms of continental crust formation through time (Belousova et al., 2010;Dhuime et al., 2012;Hawkesworth and Kemp, 2006;Lancaster et al., 2011).

Nevertheless, the reliability of this approach has recently been questioned, especially because incorporation in the mantle of continental crust-derived materials (subducted supracrustal lithologies and/or any fluid/melt generated from them) may significantly blur the zircon Hf-O isotope signatures, a problem that has not been thoroughly taken into account in crustal evolution models (Payne et al., 2016;[START_REF] Roberts | Sedimentary recycling in arc magmas: geochemical and U-Pb-Hf-O constraints on the Mesoproterozoic Suldal Arc, SW Norway[END_REF][START_REF] Roberts | The zircon archive of continent formation through time[END_REF]. Mafic magmas emplaced shortly after continental collision represent a typical, yet poorly considered case: although of unambiguous mantle origin [START_REF] Bonin | Do coeval mafic and felsic magmas in post-collisional to withinplate regimes necessarily imply two contrasting, mantle and crustal, sources? A review[END_REF], they display "crustal" wholerock radiogenic isotopes compositions [START_REF] Nelson | Isotopic characteristics of potassic rocks: evidence for the involvement of subducted sediments in magma genesis[END_REF]Turpin et al., 1988) and zircon Hf isotopic signatures (e.g. [START_REF] Heilimo | Neoarchean crustal recycling and mantle metasomatism: Hf-Nd-Pb-O isotope evidence from sanukitoids of the Fennoscandian shield[END_REF]Laurent and Zeh, 2015;[START_REF] Liu | Postcollisional potassic and ultrapotassic rocks in southern Tibet: mantle and crustal origins in response to India-Asia collision and convergence[END_REF][START_REF] Siebel | Zircon Hf isotope perspective on the origin of granitic rocks from eastern Bavaria, SW Bohemian Massif[END_REF]Zhao et al., 2013). Although such mafic magmas are ubiquitous amongst orogenic systems since the late Archean and may be the parent of volumetrically important granite suites [START_REF] Fowler | Mixed Caledonian appinite magmas: implications for lamprophyre fractionation and high Ba-Sr granite genesis[END_REF]Laurent et al., 2013), little attention has been paid so far to their role in the formation of new crust, as well as the impact of their ambiguous isotopic signatures on continental evolution models.

This study aims to review the characteristics and petrogenesis of post-collisional mafic magmas; propose a unified model to explain their origin; quantify to what extent they contribute to the formation of new crust; and address the potential biases introduced by their zircon Hf-O isotopic signature in global, zirconbased crustal evolution models. We address these issues using: (i) a new, comprehensive geochemical and zircon Hf-O isotopic dataset of post-collisional mafic magmas from the Variscan French Massif Central, and (ii) a global compilation of geochemical data from similar rocks over geological time.

Post-Collisional Mafic Magmas (PCMM)

Geological setting

Hereafter, the post-collisional period is referred to as the stage of the orogenic cycle immediately following the docking of two continental masses. Voluminous magmatism, often referred to as "syn-to post-collisional" [START_REF] Bonin | Do coeval mafic and felsic magmas in post-collisional to withinplate regimes necessarily imply two contrasting, mantle and crustal, sources? A review[END_REF], takes place at that stage. The corresponding volcanic/plutonic rocks belong to two contrasting suites: (i) a peraluminous silicic suite, originating from melting of the local crust; and (ii) a mafic-felsic high-K calc-alkaline association in which the felsic material is generally regarded as the result of differentiation of the mafic parental melt, with varying contributions (assimilation/mixing) from the older crust [START_REF] Bonin | Do coeval mafic and felsic magmas in post-collisional to withinplate regimes necessarily imply two contrasting, mantle and crustal, sources? A review[END_REF][START_REF] Küster | Post-collisional potassic granitoids from the southern and northwestern parts of the Late Neoproterozoic East African Orogen: a review[END_REF]Laurent et al., 2013;Liégeois et al., 1998;Moyen et al., in press). In this contribution, we focus on the genesis of the mafic parents of the high-K calc-alkaline suite that will be referred to as Post-Collisional Mafic Magmas (PCMM) hereafter. PCMM have been recognized in most orogenic systems since the late Archean, especially those corresponding to the amalgamation of the main supercontinents in Earth history (Table 1; see also [START_REF] Murphy | Appinite suites: a record of the role of water in the genesis, transport, emplacement and crystallization of magma[END_REF]. Because of their peculiar characteristics, they are often mentioned using local, non-IUGS nomenclature (Table 1) that hampers a comprehensive view of their global significance.

Case study: the Variscan French Massif Central

The Variscan belt of western Europe (Fig. 1a) was formed during the assembly of Pangea, as a result of the convergence between Laurussia and Gondwana from 420 to 295 Ma. In the eastern French Massif Central (FMC), continental collision took place 184 S. Couzinié et al. / Earth and Planetary Science Letters 456 (2016) 182-195 Chantraine et al. (1996). Post-collisional mafic magmas (triangles) and their derivatives (granite bodies in blue) are highlighted. The inset shows the location of the study area within the Massif Central. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) at c. 360-340 Ma and was followed by orogenic extension and collapse. The latter stage was associated with significant crustal melting resulting in widespread granite magmatism and the formation of granite-migmatite domes (e.g. Velay Complex) (Ledru et al., 2001 and references therein). PCMM are present throughout the Variscan belt [START_REF] Von Raumer | Durbachites-Vaugnerites -a geodynamic marker in the central European Variscan orogen[END_REF]. In the eastern FMC, they intruded the crust from c. 335 to 300 Ma (Couzinié et al., 2014;Laurent et al., 2015), forming meter-to hectometer-sized (monzo)diorite to monzonite bodies in granites/migmatites; and dykes at shallower crustal levels (Couzinié et al., 2014). These rocks consist of an assemblage of plagioclase, amphibole, biotite and clinopyroxene; with orthopyroxene, K-feldspar and quartz in subordinate and various proportions (Sabatier, 1991). Accessory minerals include apatite, allanite, titanite and zircon. Like in other PCMM occurrences worldwide (e.g. Laurent et al., 2014a;[START_REF] Murphy | Appinite suites: a record of the role of water in the genesis, transport, emplacement and crystallization of magma[END_REF], the predominance of biotite and/or amphibole as main mafic minerals points to high H 2 O contents in the original magma. In the FMC, a suite of K-rich calc-alkaline granitoids demonstrably results from differentiation of PCCM with little or no input from the older crust (Moyen et al., in press). In this area, PCMM and their derivatives represent ≈10% of the exposed surface (Moyen et al., in press).

Samples, methods and data compilation

In this study, we present new whole-rock geochemical data and a new zircon Lu-Hf and O isotope dataset on PCMM from the eastern FMC (Fig. 1b). The whole-rock major and trace element compositions of 27 samples are reported in the Supplementary Material (Table S1). The Hf isotopic composition of zircons from 12 samples was measured by laser ablation -multicollector -inductively coupled plasma -mass spectrometry (LA-MC-ICP-MS) at Goethe Universität Frankfurt, Germany, after imaging of internal zircon structures (cathodoluminescence and back-scattered electron images) by scanning electron microscopy. The zircons were previously analyzed for U-Pb isotopes by LA-ICP-MS for age determination (Laurent et al., 2015). Out of the 12 samples investigated for Hf isotopes, zircons from 8 samples were also analyzed for O isotopes by SHRIMP at the University of Granada, Spain. The nature and ages of the investigated samples are detailed in Table 2; the Supplementary Material contains details about analytical methods, results of standard measurements (Table S2 for Hf and S4 for O) and the complete datasets (Table S3 for Hf, Table S5 for O).

We also present a compilation of data from PCMM worldwide, available in the Supplementary Materials and including whole-rock geochemistry (N samples = 1647; Table S6) and zircon Hf (N spots = 2425; Table S7) and O (N spots = 633; Table S8) isotopes.

Whole-rock geochemistry and Hf-O isotope composition of PCMM

Whole-rock geochemistry

PCMM all share similar geochemical features (Fig. 2). They are mafic to intermediate (44 to 63 wt.% SiO 2 ) and dominantly plot in the high-K calc-alkaline to shoshonite fields (Fig. 2a). PCMM typically show a dual geochemical signature characterized by richness in both compatible and incompatible elements [START_REF] Fowler | Phanerozoic sanukitoids from Caledonian Scotland: implications for Archean subduction[END_REF][START_REF] Holub | Ultrapotassic plutonic rocks of the durbachite series in the Bohemian Massif: petrology, geochemistry and petrogenetic interpretation[END_REF]Laurent et al., 2014b). In PCMM from the FMC, this is best illustrated by high contents in both K 2 O (1.0-7.5 wt.%) and FeO t + MgO (7-25 wt.%) (Fig. 2b). Likewise, both Ba + Sr (0.1-0.6 wt.%) and Ni + Cr contents (50-1000 ppm) are very high (Fig. 2c). Notably, there is no correlation whatsoever between compatible and incompatible elements (Fig. 2b,c). PCMM display high LREE and HFSE contents (Fig. 2d), together with crustlike incompatible trace element patterns systematically characterized by negative Nb-Ta and Ti anomalies (Fig. 2e). Strikingly, these rocks are markedly enriched in most incompatible elements (LILE, LREE, HFSE) relative to the bulk continental crust (Fig. 2e).

Hf isotopes

A compilation of available zircon Hf isotopic data from PCMM in various orogenic systems is presented in Fig. 3a. Apart from a few exceptions, such zircons display (sub-)chondritic εHf (t) , clearly , 1995); the fields correspond to the 1st to 3rd quartile range of samples from the eastern FMC (in blue) and each other orogenic system (in grey), respectively. BCC stands for the Bulk Continental Crust (values from Rudnick and Gao, 2003), OIB for Ocean Island Basalts (values from Sun and McDonough, 1989), N-MORB for Normal-type Ocean Ridge Basalts (values from Sun and McDonough, 1989). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

differing from that of DM at the time of magma formation. This typical feature of PCMM is well reflected by rocks from the eastern FMC (Fig. 3b and Table 2). Zircon grains from such rocks show simple internal structures, without core-rim relationships and yield a single population of concordant U-Pb ages (Couzinié et al., 2014;Laurent et al., 2015). This argues for a single event of zircon forma-tion during magma crystallization and limited or no host-rock assimilation. Hence, the initial Hf isotopic composition ( 176 Hf/ 177 Hf t ), can reliably be considered as representative of that of the magma at the time of zircon crystallization. The newly-obtained zircon Hf dataset for PCMM from the FMC can be divided into two subsets (Table 1). Subset A comprises the four oldest samples of the investigated dataset (309-320 Ma). The zircon 176 Hf/ 177 Hf t ratios of samples from subset A range from 0.282319 ± 0.000032 to 0.282480 ± 0.000028 (2 S.E. -standard error), corresponding to subchondritic εHf (t) of -3.7 to -9.4 (Fig. 3b). Subset B includes the younger samples, all having ages in the range 299-310 Ma. Their zircons have 176 Hf/ 177 Hf t ranging between 0.282441 ± 0.000026 and 0.282562 ± 0.000026 (2 S.E.) corresponding to subchondritic εHf t of -1.1 to -5.0 (Fig. 3b). The εHf t variability within a given sample is small (always <3 εHf-units) and in most cases close to the analytical uncertainties (i.e. ±1.1 εHf-units), indicating that zircons crystallized from a magma with homogeneous Hf isotope composition. Although some overlap occurs between the two groups, zircons from samples of subset A have more variable (the scatter is always >4 εHf-units for a given sample) and generally less radiogenic 176 Hf/ 177 Hf t than samples from subset B, with most grains having εHf t lower than -5 and down to -9.4 (Fig. 3b). Because of this large dispersion, the average εHf t calculated for each sample of subset A is probably of little geological significance and the scatter may rather correspond to heterogeneous Hf isotope composition of the original magma.

Oxygen isotopes

Fig. 4a summarizes available in situ O isotopes measurements on PCMM zircons. The δ 18 O SMOW of zircons from PCMM are highly variable and range from +2.5 to +10h. They are often out of the range of δ 18 O SMOW expected for zircons crystallizing from mantle-derived magmas, especially in the most recent (Himalayan, Variscan and Caledonian) orogens (Fig. 4a).

All zircon data from PCMM of the eastern FMC show high δ 18 O SMOW values (Fig. 4b), mostly between 6.39 ± 0.32 and 8.92 ± 0.26h (2 S.E. -standard error) with a few spots with even higher δ 18 O SMOW up to 9.97 ± 0.24. The variability per sample is typically large, >0.6h (2 S.D.), i.e. well above the range of analytical uncertainties (<0.3h; see Table S5). This argues for heterogeneous O isotope compositions of the magmas at the time of zircon crystallization.

Discussion

Petrogenesis of PCMM in the FMC

Source vs. emplacement processes

The most mafic components of the PCMM suite in the FMC display low SiO 2 (<53%), with high MgO + FeO t (>12%) and transition element (Cr > 250 ppm. Ni > 120 ppm) contents. This demonstrates that the parental melt cannot be derived from crustal lithologies, but rather equilibrated with a(n) (ultra)mafic residue (i.e. peridotite/pyroxenite) [START_REF] Holub | Ultrapotassic plutonic rocks of the durbachite series in the Bohemian Massif: petrology, geochemistry and petrogenetic interpretation[END_REF]Sabatier, 1991). From that perspective, the high incompatible element contents and "crustlike" Hf-O isotopic signatures of PCMM could result from two distinct processes: (i) evolution of an incompatible element-poor, mantle-derived basaltic melt by fractionation and/or assimilation of crustal lithologies (i.e. AFC processes); or (ii) partial melting of a mantle source already enriched in K 2 O, H 2 O and LILE. Several lines of evidence indicate that AFC cannot explain the geochemical signature of PCMM:

(1) Even starting from an "enriched" basaltic composition (i.e.

OIB-like), considerable amounts of crystallization (>50%) are required to drive the incompatible element contents to the elevated concentrations observed in PCMM, such that the final melt would certainly not be mafic any more (Fig. 5a). ( 2) Assimilation of continental crust during magma emplacement is precluded by the lower incompatible element contents of the most widespread crustal lithologies compared with PCMM, which holds true for both the FMC case and the global perspective (inset Fig. 5a).

(3) Even assuming that a crustal contaminant with the adequate trace element composition exists in the FMC and that only limited fractionation (≤20%) took place so that the final magma remained mafic, AFC calculations show that driving the Hf isotopic composition of a DM-derived basalt to that of the PCMM would require a crustal contaminant with εHf 310 Ma of -50 (Fig. 6a), corresponding to an early Archean crustal component (model age >3.6 Ga). This is extremely unlikely in the case of the FMC where the oldest crust is early Paleozoic to Neoproterozoic in age (Melleton et al., 2010). S8. The δ 18 O for the mantle is from Valley et al. (1998). Arrows for supra-crustal weathered materials and ridge-altered materials according to [START_REF] Bindeman | Oxygen isotopes in mantle and crustal magmas as revealed by single crystal analysis[END_REF].

(b) Zircon oxygen isotope composition of PCMM from the eastern French Massif Central. For each sample are displayed the mean and 2 S.D. confidence level. Error bars are the analytical standard errors of each measurement plotted at 2σ .

In contrast, PCMM plausibly represent primary melts derived from an anomalously K 2 O-, LILE-and H 2 O-rich mantle. Indeed, experimental melting of phlogopite-and/or amphibole-bearing (i.e. K-rich) peridotites, particularly spinel-lherzolites, yields melts with major element compositions matching those of PCMM from the FMC (Fig. 5b) [START_REF] Conceição | Derivation of potassic (shoshonitic) magmas by decompression melting of phlogopite + pargasite lherzolite[END_REF]Condamine and Médard, 2014;[START_REF] Green | Experimental petrology of peridotites, including effects of water and carbon on melting in the Earth's upper mantle[END_REF][START_REF] Mengel | Stability of amphibole and phlogopite in metasomatized peridotite under water-saturated and water-undersaturated conditions[END_REF][START_REF] Thibault | Experimental investigation of melts from a carbonated phlogopite lherzolite: implications for metasomatism in the continental lithospheric mantle[END_REF]. Importantly, experiments conducted with mixed peridotite + felsic (granitoid) starting materials produce melts of similar compositions (Mallik et al., 2015;[START_REF] Prouteau | Evidence for mantle metasomatism by hydrous silicic melts derived from subducted oceanic crust[END_REF][START_REF] Rapp | Continent formation in the Archean and chemical evolution of the cratonic lithosphere: melt-rock reaction experiments at 3-4 GPa and petrogenesis of Archean Mg-diorites (sanukitoids)[END_REF]. The two sets of experiments are equivalent from a petro-geochemical point of view because, in the second approach, the mixture yields a phlogopite-and/or amphibole-bearing peridotite/pyroxenite in equilibrium with a mafic K-rich melt. Therefore, experimental evidence unequivocally shows that hybridization between peridotite and a felsic component is required to explain the major-element composition of PCMM (irrespective of the hybridization mechanism and the exact nature of the felsic component, which are discussed in §4.1.2).

The same conclusion can be drawn for trace elements. We calculated the REE contents of a melt generated from a hybrid source consisting of 75-90% DM and 10-25% of a LREE-rich component (having the composition of the bulk continental crust). Fig. 5c shows that the resulting melts (for 5 to 20% melting) match the composition of PCMM from the FMC, again with a better fit for a spinel-facies source.

Therefore, we propose that PCMM in the FMC result from partial melting, at <2 GPa, of a phlogopite-/amphibole-bearing peri-dotite (or pyroxenite) corresponding to mantle domains enriched in K 2 O, H 2 O and other incompatible elements.

Mechanism of mantle enrichment and nature of the metasomatic agent

Considering that they reflect the composition of the hybrid mantle source, the observed negative εHf t signatures in PCMM zircons can be explained by two distinct scenarios: (i) contamination of the mantle (with εHf t >> 0) by crustal material with strongly negative Hf isotope composition (εHf t << 0) shortly prior to PCMM formation; or (ii) a long time span between mantle contamination (by any material having low 176 Lu/ 177 Hf) and PCMM formation, whereby the initial decrease of the mantle 176 Lu/ 177 Hf ratio leads to a time-integrated, non-radiogenic Hf isotope composition. Several lines of evidence clearly favor the first hypothesis. Firstly, the mantle beneath the FMC (sampled as xenoliths in Cenozoic volcanoes) do not show evidence for any geological event older than ca. 0.6 Ga (Wittig et al., 2007), which is also the age of the oldest autochtonous crust (Melleton et al., 2010).

In contrast, the strongly negative εHf t of PCMM zircons in the FMC would require the involvement of much older mantle, of at least Mesoproterozoic age (>1.1 Ga, considering an unlikely 176 Lu/ 177 Hf = 0 for the source). Secondly, prior to the emplacement of PCMM in the late Carboniferous (330-300 Ma), other mafic magmas were emplaced throughout the FMC during the late Devonian and early Carboniferous (380-360 Ma) and contrastingly show positive bulk-rock εNd t (+1 to +5, up to +8) (Pin andPaquette, 1997, 2002), indicative of a depleted mantle origin. If any long-term enriched mantle could have survived underneath the FMC, it is difficult to envisage that it would have been sampled by magmatism at ca. 330-300 Ma, but not at 380-360 Ma, especially since "enriched" upper mantle domains are particularly prone to melting (solidus temperatures as low as 1025-1075 • C at 1 GPa; [START_REF] Conceição | Derivation of potassic (shoshonitic) magmas by decompression melting of phlogopite + pargasite lherzolite[END_REF]Condamine and Médard, 2014). Thirdly, PCMM of the FMC only post-date by 50-100 Ma an episode of Silurian-Devonian tectonic accretion and subduction of continental/oceanic units belonging to the northern margin of Gondwana (Faure et al., 2008;Melleton et al., 2010). Such units, now exposed as migmatitic ortho-and paragneisses containing eclogitic relics, were buried at depths >100 km and underwent HP partial melting (Faure et al., 2008;Lardeaux et al., 2001;Pin and Lancelot, 1982), thereby providing a straightforward way to metasomatize the mantle with crustal-derived K-, H 2 O-and LILE-rich material. The same model was proposed to explain the occurrence of PCMM in the Variscan Bohemian Massif [START_REF] Janoušek | The causal link between HP-HT metamorphism and ultrapotassic magmatism in collisional orogens: case study from the Moldanubian Zone of the Bohemian Massif[END_REF], the Himalayas (Campbell et al., 2014;Guo et al., 2014) and the Dabie-Sulu orogen (Zhao et al., 2013).

Importantly, mass balance calculations show that binary mixing between (i) 80-90% DM and (ii) 10-20% of a crustal component with εHf t = -10 and δ 18 O = +20h readily explains the Hf-O isotopic composition of PCMM zircons in the FMC (Fig. 6b).

High δ 18 O is typically observed in subducted continental sedimentary materials having experienced a low-T weathering cycle, e.g. the East Indonesian (δ 18 O = +15 to +24; [START_REF] Vroon | Oxygen isotope systematics of the Banda Arc: low δ 18 O despite involvement of subducted continental material in magma genesis[END_REF] or Lesser Antilles (δ 18 O = +19 to +21; [START_REF] Davidson | Crustal contamination versus subduction zone enrichment: examples from the Lesser Antilles and implications for mantle source compositions of island arc volcanic rocks[END_REF] sediments.

Moreover, the pre-Variscan crust of the FMC is dominated by paragneisses (and meta-granitoids derived from melting of the latter) corresponding to former sediments of the north Gondwana margin, which are characterized by Archean (2.5-3.3 Ga), Paleoproterozoic (1.8-2.2 Ga) and Neoproterozoic (0.5-0.7 Ga) detritus, as indicated by age patterns of detrital zircon grains [START_REF] Albert | Provenance of the HP-HT subducted margin in the Variscan belt (Cabo Ortegal Complex, NW Iberian Massif)[END_REF]Linnemann et al., 2014). Fig. 7a shows that a mixture of these three crustal components, including at least 45-85% of Paleoproterozoic-Archean crust, would readily account for the inferred Hf isotopic signature (εHf 310 Ma = -10; T DM = 1.8 Ga) of the crustal material in the hybrid mantle source. In fact, the bulk Hf budget carried by detrital zircons in the pre-Variscan crust of the FMC is consistently characterized by an average εHf 310Ma of ca. -10 (Fig. 7b). This observation clearly supports that the hybrid source of PCMM in the FMC results from interactions between mantle peridotite and subducted pre-Variscan continental shelf sediments of the former north Gondwana margin.

Further constraints on the nature of the crust-derived materials and how they were incorporated in the mantle can be placed by considering bulk rock Th/La ratios, which are not significantly fractionated during mantle melting (Plank, 2005). Indeed, the source of PCMM samples with the highest Th/La and δ 18 O and lowest εHf t (Subset A) was likely metasomatized by felsic melts derived (100*MgO/(FeO t + MgO) [mol]) showing no particular correlation, precluding any significant role played by fractionation or crustal assimilation/contamination. The green arrow shows the evolution of a primary melt (La = 37 ppm, similar to OIB, Sun and McDonough (1989); Mg# = 70) for 50% fractional crystallization of a 25% clinopyroxene + 10% plagioclase + 60% biotite + 5% olivine assemblage (Mg# = 77), supposedly controlling the liquid line of descent of PCMM (mineral proportions and compositions from Parat et al., 2009). Partition coefficients are from [START_REF] Lee | Extension of lattice strain theory to mineral/mineral rare-earth element partitioning: an approach for assessing disequilibrium and developing internally consistent partition coefficients between olivine, orthopyroxene, clinopyroxene and basaltic melt[END_REF] for olivine and clinopyroxene, from [START_REF] Grégoire | Trace element residence and partitioning in mantle xenoliths metasomatized by highly alkaline, silicate-and carbonate-rich melts (Kerguelen Islands, Indian Ocean)[END_REF] for phlogopite, from [START_REF] Mckenzie | Partial melt distributions from inversion of rare Earth element concentrations[END_REF] for garnet and plagioclase. Inset: La contents of FMC samples compared with those of the local upper (Moyen et al., in press) and lower (Downes et al., 1990) crust. (b) Major element ratios of PCMM and comparison with experimental liquids obtained by (i) melting of metasomatized, phlogopite-and/or amphibole-bearing peridotites [START_REF] Conceição | Derivation of potassic (shoshonitic) magmas by decompression melting of phlogopite + pargasite lherzolite[END_REF]Condamine and Médard, 2014;[START_REF] Green | Experimental petrology of peridotites, including effects of water and carbon on melting in the Earth's upper mantle[END_REF][START_REF] Mengel | Stability of amphibole and phlogopite in metasomatized peridotite under water-saturated and water-undersaturated conditions[END_REF][START_REF] Thibault | Experimental investigation of melts from a carbonated phlogopite lherzolite: implications for metasomatism in the continental lithospheric mantle[END_REF]; (ii) melting of phlogopite-free peridotites (Gaetani and Grove, 1998; Tenner et al., 2012); and (iii) mixed peridotite + felsic granitoid sources (Mallik et al., 2015;[START_REF] Prouteau | Evidence for mantle metasomatism by hydrous silicic melts derived from subducted oceanic crust[END_REF][START_REF] Rapp | Continent formation in the Archean and chemical evolution of the cratonic lithosphere: melt-rock reaction experiments at 3-4 GPa and petrogenesis of Archean Mg-diorites (sanukitoids)[END_REF]. The temperatures (in • C) and melt fractions (in %) indicated in the field of spinel phlogopite peridotite correspond to the experimental conditions and results of Condamine and Médard (2014). The arrow shows the variation of elemental ratios for 20% fractional crystallization of the assemblage mentioned above. (c) La/Yb vs. La plot with batch melting models (curves) of spinel and garnet phlogopite peridotite. Source compositions correspond to the Depleted Mantle (Workman and Hart, 2005) mixed with 10% to 25% Bulk Continental Crust (Rudnick and Gao, 2003) (black and gray stars, respectively). Partition coefficients for olivine, clinopyroxene and phlogopite as mentioned above, orthopyroxene from [START_REF] Lee | Extension of lattice strain theory to mineral/mineral rare-earth element partitioning: an approach for assessing disequilibrium and developing internally consistent partition coefficients between olivine, orthopyroxene, clinopyroxene and basaltic melt[END_REF]. Modal proportions in the residue are recalculated from Condamine and Médard (2014) for spinel peridotite (olivine 0.69, orthopyroxene 0.15, clinopyroxene 0.08, phlogopite 0.07, spinel 0.01) and [START_REF] Thibault | Experimental investigation of melts from a carbonated phlogopite lherzolite: implications for metasomatism in the continental lithospheric mantle[END_REF] for garnet peridotite (olivine 0.25, orthopyroxene 0.5, clinopyroxene 0.15, phlogopite 0.03, garnet 0.07). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) 190 S. Couzinié et al. / Earth and Planetary Science Letters 456 (2016) 182-195 from terrigenous sediments (Fig. 6c,d), which is consistent with the fact that subducted rocks in the FMC underwent melting at HP (Faure et al., 2008;Pin and Lancelot, 1982). The other samples (Subset B) are better explained by mixing between DM and a bulk continental crust composition (Fig. 6c,d), possibly resulting from mechanical mélanges during the subduction of the continental units. Importantly, compositions corresponding to average, bulk lower crust (low Th/La) cannot account for the observed compositions, even if we consider that such material had high δ 18 O and low εHf t (Fig. 6c,d), showing that subduction of supracrustal material is required.

A unified model for PCMM petrogenesis

As outlined earlier, PCMM worldwide share a common geotectonic, petrographic identity and similar geochemical and Hf-O isotopic characteristics, which argues for a common origin. The fact that our samples from the FMC are chemically representative of the diversity of PCMM worldwide (Fig. 3) suggests that the general features of the petrogenetic model proposed above can be reasonably extended to all PCMM suites.

Consistently, many workers advocated that the particular geochemistry of PCMM necessarily requires an enriched mantle source [START_REF] Fowler | Phanerozoic sanukitoids from Caledonian Scotland: implications for Archean subduction[END_REF]Guo et al., 2014;[START_REF] Laurent | Geochemistry and petrogenesis of high-K "sanukitoids" from the Bulai pluton, Cenral Limpopo Belt, South Africa: implications for geodynamic changes at the Archaean-Proterozoic boundary[END_REF]Laurent et al., 2014a;Laurent et al., 2014b;Liégeois et al., 1998;[START_REF] Murphy | Appinite suites: a record of the role of water in the genesis, transport, emplacement and crystallization of magma[END_REF][START_REF] Prelevic | Ultrapotassic mafic rocks as geochemical proxies for post-collisional dynamics of orogenic lithospheric mantle: the case of Southwestern Anatolia[END_REF][START_REF] Von Raumer | Durbachites-Vaugnerites -a geodynamic marker in the central European Variscan orogen[END_REF][START_REF] Williams | Nature of the source regions for post-collisional, potassic magmatism in southern and northern Tibet from geochemical variations and inverse trace element modelling[END_REF]. Moreover, the presence of continental crustderived material in such a source has often been proposed to explain the non-DM and "crustal" isotopic signatures of these rocks (Guo et al., 2014;Laurent et al., 2014b;[START_REF] Nelson | Isotopic characteristics of potassic rocks: evidence for the involvement of subducted sediments in magma genesis[END_REF][START_REF] Prelevic | Ultrapotassic mafic rocks as geochemical proxies for post-collisional dynamics of orogenic lithospheric mantle: the case of Southwestern Anatolia[END_REF]. Given the generally higher δ 18 O of PCMM zircons compared with mantle material (Fig. 4a), it is likely that these crustal materials are most often represented by supracrustal rocks. Finally, mantle enrichment shortly prior to PCMM genesis seems to be the rule because, like in the FMC, PCMM emplacement systematically post-dates by <50 Ma an oceanic and/or continental subduction stage, for instance in the late Archean terranes (Laurent et al., 2014a) and in the Himalayan [START_REF] Chung | Tibetan tectonic evolution inferred from spatial and temporal variations in post-collisional magmatism[END_REF], Caledonian [START_REF] Atherton | Slab breakoff: a model for Caledonian, Late Granite syn-collisional magmatism in the orthotectonic (metamorphic) zone of Scotland and Donegal, Ireland[END_REF] and Svecofennian [START_REF] Andersson | 1.8 Ga magmatism in the Fennoscandian Shield; lateral variations in subcontinental mantle enrichment[END_REF] orogens.

Therefore, we propose that PCMM are derived from: (i) interactions between subducted continental material (most often of supracrustal origin), or melts/fluids generated from them, and mantle peridotite; and (ii) subsequent melting of the resulting hybrid source shortly thereafter. Mantle enrichment through the subduction of continental units at the onset of collision (Campbell et al., 2014;Guo et al., 2014;[START_REF] Janoušek | The causal link between HP-HT metamorphism and ultrapotassic magmatism in collisional orogens: case study from the Moldanubian Zone of the Bohemian Massif[END_REF]Zhao et al., 2013) would be the most appropriate scenario to account for the short time lapse between the two steps; the systematic occurrence of PCMM in collision belts; and the more evolved isotopic composition and greater incompatible element contents of PCMM compared with classical arc magmas (related to oceanic subduction).

Quantifying crust and mantle contributions in post-collisional mafic magmas

The aim of this section is to quantify the respective mass fraction of mantle-vs. crust-derived elements in the "hybrid" mantle source of PCMM. This will be used in turn to determine the mass and Hart (2005)) and three different crustal materials, all characterized by εHf (t) = -10 and δ 18 O = +20 (adjusted to fit the data for a maximum mantle contamination rate of ca. 20%): (i) a melt derived from HP melting of terrigenous sediment (Hf contents [4.3 ppm] and Th/La [0.43] from Plank and Langmuir, 1998, corrected from HP melting using average partition coefficients of Hermann and Rubatto (2009)); (ii) Lower and (iii) Bulk Continental Crust (Rudnick and Gao, 2003). O contents are from [START_REF] Roberts | Sedimentary recycling in arc magmas: geochemical and U-Pb-Hf-O constraints on the Mesoproterozoic Suldal Arc, SW Norway[END_REF]. Light blue lines denote the percentage of crustal component in the mixture. Errors bars for samples are 2 S.D. All εHf t are calculated at 310 Ma (average age of PCMM in the eastern FMC). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) fraction of PCMM that derives from the mantle, which is a critical parameter to unravel their contribution to crustal growth.

As demonstrated above, the hybrid mantle source of PCMM is formed by interactions between mantle peridotite and crustal materials (fluid, melt or solid). These interactions may result in different cases in nature, e.g. a mechanical mixture of peridotite and meta-sedimentary/meta-igneous crustal rocks; a peridotite containing veins formed by reaction with percolating liquids; or a metasomatized rock where the added material is distributed in newly-crystallized phases (pyroxenes, amphibole, phlogopite). Irrespective of the nature of the metasomatic agent, the finite mass of each chemical element within any of these "hybrid" sources will be partitioned between the fraction that was already present in the original mantle prior to the interactions and that supplied by the added crust-derived material. The dual geochemistry of PCMM shows that they sampled both groups of elements, regardless the exact physical nature of the source and melting process. Therefore, for each chemical element, the mass fraction of "crust" vs. "mantle" atoms in the source of PCMM can be approximated using a simple binary mixing model based on mass-balance, assuming reasonable compositions for the two components (respectively Bulk Continental Crust and DM). Although simplistic, this calculation has the advantage of relying on few parameters, i.e. the mass fractions of the two end-members and their compositions, which in the case of crust-mantle mixing are not so critical given the huge concentration contrast between the two for most elements.

For each chemical element, we define x crust as the mass fraction of atoms that originates from crust-derived materials. Fig. 8 shows that in a hybrid mantle containing 10 to 25% crustal component, x crust varies for each element, incompatible elements being dominantly controlled by the crustal component (x crust being as high as 99% for Rb, Ba, Th, U as the initial mantle contains very little of these) whilst compatible elements mostly come from the mantle (e.g. 97% of the MgO, Cr and Ni is of mantle origin). Importantly, the five most abundant major oxides in the source (SiO 2 , Al 2 O 3 , MgO, FeO, CaO; ca. 95% of the bulk mass) are dominantly of mantle origin (x crust is generally <30%) because of the limited concentration contrast (less than one order of magnitude) between mantle and crust and the low mass fraction of the crustal component in the hybrid source (Fig. 8). As a direct and critical consequence of this, assuming that the proportion of "crust" vs. "mantle" atoms for each element does not change during melting of the hybrid source, the bulk mass fraction of PCMM that derives from the crustal component is low. Typically, for three representative PCMM samples (from a Late-Archean terrane and the Variscan and Himalayan orogens), it lies between 15-21% and 31-38%, for respectively 10% and 25% of crustal materials in the hybrid source (see Fig. 8), meaning that >62% of the bulk mass of these samples are of mantle origin and thus represent new additions to the crust.

This first-order calculation implicitly presumes that "crust" and "mantle" atoms of each element are equally distributed over mineral phases in the hybrid source so that x crust keeps constant during melting. This is likely over-simplistic for trace elements, especially the dominantly crust-derived elements that would be preferentially partitioned into the phases formed via metasomatic reactions such as pyroxenes, amphibole and phlogopite [START_REF] Prouteau | Evidence for mantle metasomatism by hydrous silicic melts derived from subducted oceanic crust[END_REF][START_REF] Rapp | Continent formation in the Archean and chemical evolution of the cratonic lithosphere: melt-rock reaction experiments at 3-4 GPa and petrogenesis of Archean Mg-diorites (sanukitoids)[END_REF], which in turn preferentially contribute to melting reactions (Condamine and Médard, 2014;Mallik et al., 2015). However, for major oxides, x crust likely remains constant throughout the process. Indeed, metasomatic reactions would randomly use both "crust" and "mantle" elements to form new minerals and, even if not, solid-state diffusion, phase recrystallization and mixing enhanced by high-temperature deformation [START_REF] Linckens | Dynamic recrystallization and phase mixing in experimentally deformed peridotite[END_REF] would smooth any significant difference of x crust from a mineral to another. Moreover, even considering an artificial two-fold increase in the proportion of "crustal" SiO 2 and Al 2 O 3 between a highly-enriched mantle composition (25% crustal component) and the melt owing to their potential concentration in newly formed phlogopite, amphibole and pyroxene, the mass fraction of crust-derived elements in the three PCMM samples used for calculation would not exceed 50-63%. These are definitely maximum values since this scenario is somewhat extreme. Therefore, it is reasonable to conclude that the proportion of reworked crustal materials in PCMM does not exceed 63% and is most often, as calculated earlier, between 15 and 38%.

Paradoxically, most PCMM (especially the three specimens used in the calculations) display markedly negative zircon εHf t . Then, from an Hf isotope perspective alone, those rocks apparently cor-192 S. Couzinié et al. / Earth and Planetary Science Letters 456 (2016) 182-195 Fig. 8. Plot of the "x crust " parameter for major oxides (panel (a), sorted as a function of their abundance in PCMM) and trace elements (panel (b), reported by increasing compatibility). x crust is defined as the mass fraction of any element i controlled by the crustal component in a hybrid mantle source consisting of Depleted Mantle (Workman and Hart, 2005) +10 (black line) to 25% (grey line) crustal material (Bulk Continental Crust, Rudnick and Gao, 2003), calculated as follows:

x i crust = f crust [i] crust /(f crust [i] crust + (1 -f crust )[i] DM )
where [i] depicts the concentration of element i and f crust the proportion of crustal component in the hybrid source. The blue field represents the bulk fraction of crust-derived elements ( X crust ) in mafic magmas derived from such a source, calculated for three representative samples of PCMM suites: 533-2 (this study); MAT-60 (Laurent et al., 2014b); and 08YR05 [START_REF] Liu | Postcollisional potassic and ultrapotassic rocks in southern Tibet: mantle and crustal origins in response to India-Asia collision and convergence[END_REF]. The calculation has been performed by (i) weighting the concentrations of all elements in each sample by the corresponding values of x crust , and (ii) summing up the resulting values. See text for discussion.

X crust = n i=1 x i crust • [i] PCMM .
respond to pure reworking of former crustal lithologies. This discrepancy simply results from the large dominance of the crustal component on the incompatible trace element budget (including the radiogenic tracers Sr, Nd, Hf, Pb) in the hybrid source (Fig. 8). Typically, the Hf budget in the source of PCMM consists of 72-89% non-radiogenic "crustal" Hf and only 11-28% radiogenic "mantle" Hf. Therefore, as long as incompatible element tracers are considered, PCMM would bear a "crustal" signature and the mantle contribution to their origin, although dominant in terms of mass, would be invisible.

Consequences for crustal growth

As demonstrated earlier (Table 1), PCMM have been emplaced during or at the end of continental collision since the late Archean [START_REF] Bonin | Do coeval mafic and felsic magmas in post-collisional to withinplate regimes necessarily imply two contrasting, mantle and crustal, sources? A review[END_REF][START_REF] Fowler | Phanerozoic sanukitoids from Caledonian Scotland: implications for Archean subduction[END_REF]Laurent et al., 2014a), specifically at each stage of supercontinent amalgamation. They are therefore a systematic magmatic feature of the orogenic cycle, just as MORB, arc magmas or collisional granites are, and their significance for global crustal evolution must be addressed.

Although the surface expression of PCMM is limited, it has been demonstrated in several settings that they would actually represent the parental magmas of much more voluminous granitoid suites via fractionation [START_REF] Fowler | Mixed Caledonian appinite magmas: implications for lamprophyre fractionation and high Ba-Sr granite genesis[END_REF][START_REF] Küster | Post-collisional potassic granitoids from the southern and northwestern parts of the Late Neoproterozoic East African Orogen: a review[END_REF]Laurent et al., 2013;Moyen et al., in press) and/or limited interaction with coeval crustal melts [START_REF] Clemens | Sources of post-orogenic calcalkaline magmas: the Arrochar and Garabal Hill-Glen Fyne complexes[END_REF]Janoušek et al., 2004;Laurent et al., 2014a;Parat et al., 2009). In terms of mass balance, these two processes are antagonists: silicic liquids will represent only a fraction of the initial mass of mafic magma in the case of fractionation, whereas interaction with crustal material represents a mass addition to PCMM to form granitoids. Hence, it is reasonable to consider that in a given orogenic system, the initial volume of PCMM was roughly equivalent to that of their genetically related granitoids. According to Moyen et al. (in press), PCMM-derived granitoids represent ca. 10% of exposed rocks in the Variscan belt; given that 62 to 85% of the bulk mass of PCMM consist of elements extracted from the mantle (see section 4.3), and assuming that surface exposure reflects the repartition of lithologies at depth, then 6.2 to 8.5% of the bulk mass of the Variscan crust represents new additions from the mantle by PCMM.

At first glance, this estimate appears modest in comparison with arc settings, in which the large majority of the bulk crustal volume is derived from the differentiation of mantle-derived mafic magmas (Jagoutz and Kelemen, 2015). However, mantle-derived magmatic rocks only become long-term additions to the continental volume if they are subsequently preserved: while a small fraction of arc granitoids may be captured in collisional orogens (Condie et al., 2011), the majority of them are readily recycled into the mantle shortly after their formation owing to sediment subduction and/or subduction erosion (Stern and Scholl, 2010). In contrast, PCMM and derivatives represent small volumes of only partly mantle-derived magmas, but because they are shielded in the core of newly formed continental masses, they have a much greater preservation potential in the geological record (Hawkesworth et al., 2010). As a result, they may represent significant contributors to long-term crustal growth.

Recently, the problem of crustal growth through time has been extensively addressed via the statistical analysis of global zircon Hf (Belousova et al., 2010;Condie et al., 2011) or coupled Hf-O (Dhuime et al., 2012) isotopic databases: Hf model ages are used to determine the timing of crust formation, and O isotopes to distinguish zircons formed in granitoids reworking a "juvenile" source (δ 18 O = 5.5 ± 1.0h) or a "mixed" sedimentary source (δ 18 O > 6.5h) (e.g. Hawkesworth and Kemp, 2006). The reliability of this approach has been questioned recently, especially because Hf and O isotopes in zircon reflect in most cases the contribution of multiple components in the origin of their host magma (magma mixing, heterogeneous sources, crustal contamination) (Payne et al., 2016;[START_REF] Roberts | The zircon archive of continent formation through time[END_REF]. The case of PCMM raises an even more problematic issue, showing that igneous material representing a non-negligible contribution to long-term crustal growth may not have DM-like Hf isotope compositions and "pristine mantle" O isotope compositions because of the small proportions of crustal (possibly sedimentary) material in their hybrid mantle source.

Several lines of evidence suggest that, despite their limited volume, zircons from PCMM and derivatives represent a sizeable proportion of global detrital zircon databases. First, because of their selective preservation (Hawkesworth et al., 2010), zircons from collision-related igneous rocks dominate the detrital populations in sedimentary rocks wherever recent or ancient orogenic crust is present in the catchment area (Spencer et al., 2015). Second, because of their high Zr contents (370 ppm in average in the eastern FMC), rocks from the PCMM suite have a higher zircon fertility factor ("ZFF" of Dickinson, 2008) than other collisional granites (150 ppm Zr in the eastern FMC; Moyen et al., in press).

Third, magmatic zircons from these rocks show a greater proportion (∼80%) of concordant U-Pb ages compared to those of purely crust-derived ("S-type") granites (∼50%) (Couzinié et al., 2014;Laurent et al., 2015), such that in a detrital zircon population, the probability to discard zircons from PCMM and derivatives because of U-Pb discordance (Nemchin and Cawood, 2005) is smaller than for S-type granites. To illustrate the two latter issues, the erosion of the Variscan crust, assuming that the latter consists of 10% PCMM-derived granitoids (ZFF = 2.5; 80% U-Pb concordance); 30% crust-derived granites (ZFF = 1; 50% U-Pb concordance); and 60% of metamorphic and sedimentary rocks (ZFF = 1; 67% U-Pb concordance), would yield a detrital zircon population in which the final, U-Pb concordant dataset contains a minimum of 27% data from PCMM-derived material -notwithstanding the likely possibility that metamorphic and sedimentary rocks may contain zircons from reworked, earlier PCMM and related granites, exactly for the same reasons.

Therefore, zircons derived from PCMM, their differentiated products and any igneous and sedimentary material derived from them, would significantly bias the crustal growth signal of global detrital zircon databases, in two distinct ways:

(1) Zircons from any PCMM crystallized at time t would have been either discarded (non-mantle δ 18 O resulting from the involvement of sedimentary components) or attributed to ancient events of crust formation because of non-radiogenic Hf isotope compositions (and old Hf model ages). Although the latter feature certainly reflects reworking of older crust to some extent, this reworking is over-estimated because the mantle contribution at time t cannot be resolved by Hf isotopes alone (see section 4.3).

(2) If PCMM-derived crustal material is reworked by later magmatic events, then the calculation of model ages based on DM for zircons formed in these younger magmas is inappropriate since their crustal source had a non-DM Hf isotopic composition.

Both would have the same global effect, i.e. skewing crustal growth models towards an over-estimation of ancient crustal growth with respect to younger crust formation. Specifically, because PCMM are present on Earth since the late Archean (Table 1), post-Archean crustal growth rates may be significantly underestimated. In the following, we consider that inherited zircon grains in MPG/CPG are dominantly restitic and were incorporated in the magma at source level [START_REF] Clemens | S-type granitic magmaspetrogenetic issues, models and evidence[END_REF] thus providing a faithful record of the source age pattern. Apart for one grain, c. 470 Ma-old inherited zircons have Hf isotope compositions closer to UGU gneisses than amphibolites favouring a gneissic source, in line with the chemistry of MPG/CPG granites (Moyen et al., 2017a).

Conclusions

Meta-igneous vs. metasedimentary source

Overall, these comparisons suggest that the source of MPG/CPG is mixed and composed of: (i) meta-granites of the VOF; (ii) metasediments of the LGU; (iii) a metamorphic lithology which zircon age pattern resembles that of UGU gneisses. It is unlikely that the UGU itself is present in the source region of MPG/CPG. Indeed, metamorphic and structural investigations clearly support an allochtonous origin of the nappe which would have been rooted further north with respect to the Velay dome [START_REF] Burg | Inverted metamorphic zonation and large scale thrusting in the Variscan belt: An example in the French Massif central[END_REF]1989). An alternative would be to consider that early Variscan thrusting resulted in the imbrication of crust slices with contrasted pre-Variscan histories so that a crust segment having recorded Ordovician magmatic events would lie structurally below the

LGU. Such possibility is supported by UPb dating conducted on metasedimentary lower crustal xenoliths scavenged by Cenozoic volcanoes [START_REF] Rossi | Variscan to eo-Alpine events recorded in European lower-crust zircons sampled from the French Massif Central and Corsica, France[END_REF]. In addition to grains showing "Variscan" dates, these authors report the presence of older zircons with concordant 206 Pb/ 238 U dates ranging from 629 ± 56 Ma down to 436 ± 12 Ma. Such material would adequately correspond to the UGU-alike component. Yet, limited available data do not allow to further test this hypothesis.

Rough estimates of the proportion of the three above-mentioned components may be retrieved via the following procedure. The set of inherited zircon grains is divided into three subsets: late CambrianOrdovician (445530 Ma), Ediacaranearly Cambrian (530560) and older dates (> 560 Ma). Each subset is assumed to exclusively originate from one of the three inferred source components, respectively the "UGU-alike" material, the VOF meta-granites and the LGU metasediments. A zircon "fertility" factor (ZFF of Dickinson, 2008) is attributed to each source based on their average Zr content, provided that all Zr is hosted in zircon. Our chemical survey (see Chapter 2 and Appendix Table B1) indicate that the VOF meta-granites and LGU metasediments have average Zr concentrations of 104 and 260 ppm resulting in ZFF of 1 and 2.5, respectively. The ZFF of the "UGU-alike" material was set free to vary between these two values. Resulting proportions in the source of MPG/CPG are 1022 % for the "UGU-alike" component, 5565 % for the VOF and 2226 % for the LGU metasediments. Such rst-order calculation implicitly requires that all three sources melt synchronously and produce magmatic liquids of similar compositions so that each zircon grain, no matter its origin, has the same probability to survive dissolution. Of course, such assumption is highly simplistic and entails that the results are only crude estimates.

Conclusion

Examination of the inherited zircon record in Variscan peraluminous granites suggests that one of the constituent lithology of the FMC crust segment (the Velay Orthogneiss Formation) was selectively reworked during the post-collisional magmatic episode. Several hypotheses can be formulated to account for this. First, this may reect the mass distribution of each crustal component at depth, the VOF being volumetrically dominant as observed at present-day outcropping level. Alternatively, such apparent pattern may arise from contrasted zircon behaviour in metasedimentary vs. meta-igneous derived magma batches. These hypotheses can be tested by further examining the root zone of granite magmas i.e. migmatite terrains. This is further discussed in the next Chapter which provides a comprehensive case study of a migmatite dome from the southern part of the Velay Complex.

Chapter 6

Post-collisional exhumation of the partially molten crust: a case study from the Masméjean migmatite dome Partial melting of the continental crust generates incompatible element-rich, mobile and buoyant melts that rise upwards to the surface and ultimately lead to the chemical layering of the crust [START_REF] Sawyer | Melt segregation in the continental crust[END_REF][START_REF] Sawyer | When the Continental Crust Melts[END_REF][START_REF] Vielzeuf | Granites, granulites, and crustal dierentiation[END_REF]. Migmatites are crustal rocks that preserve evidence for the concomitant presence of a melt and a residual solid phase in their framework and are thus regarded as the source of crustderived magmas [START_REF] Brown | The generation, segregation, ascent and emplacement of granite magma: the migmatite-to-crustally-derived granite connection in thickened orogens[END_REF][START_REF] Clemens | The granulite -granite connexion[END_REF]. Such rocks are abundant in orogenic domains where they often crop out in gneiss domes. Those are typically composed of a core built up by high-grade, commonly anatectic, metamorphic lithologies (plus granites) featuring a domal foliation and are mantled by rocks of lower metamorphic grade [START_REF] Teyssier | Gneiss domes and orogeny[END_REF]Whitney et al., 2004a). The concurrence of dome formation and anatexis has been interpreted as reecting the vertical ow of partially molten middle to lower crustal layers [START_REF] Tirel | Thermomechanical modeling of extensional gneiss domes[END_REF]Whitney et al., 2004b) and suggests that doming is intimately linked with the process of continental crust reworking.

Anatectic gneiss domes are generated in a range of regional strain conditions, from extensional (in metamorphic core complexes, where dome formation is controlled by localized extension in the upper crust, e.g. [START_REF] Brun | Extensional gneiss domes and detachement fault systems : structure and kinematics[END_REF][START_REF] Chen | The Kangmar Dome: A Metamorphic Core Complex in Southern Xizang (Tibet)[END_REF][START_REF] Escuder Viruete | P-T paths derived from garnet growth zoning in an extensional setting: an example from the Tormes Gneiss Dome (Iberian massif, Spain)[END_REF] to compressional (buckle folds, e.g. [START_REF] Burg | Exhumation during crustal folding in the Namche-Barwa syntaxis[END_REF]2004;[START_REF] Típská | Complex metamorphic zonation of the Thaya dome: result of buckling and gravitational collapse of an imbricated nappe sequence[END_REF][START_REF] Zeitler | Synchronous anatexis, metamorphism, and rapid denudation at Nanga Parbat (Pakistan Himalaya)[END_REF]. In both cases, diapirism, which refers to the buoyancy-driven ascending ow that counteracts inverted density gradients [START_REF] Biot | Theory of gravity instability with variable overburden and compaction[END_REF][START_REF] Weinberg | Polydiapirs: multiwavelength gravity structures[END_REF], would proceed during doming since partially molten rocks are less dense than their overlying roof units [START_REF] Bouhallier | Strain patterns in Archaean dome-and-basin structures: The Dharwar craton (Karnataka, South India)[END_REF][START_REF] Burg | Structures and way-up criteria in migmatites, with application to the Velay dome (French massif Central)[END_REF][START_REF] Calvert | Diapiric ascent and cooling of a sillimanite gneiss dome revealed by 40 Ar/ 39 Ar thermochronology: the Kigluaik Mountains[END_REF][START_REF] Kruckenberg | Flow of partially molten crust and the internal dynamics of a migmatite dome, Naxos, Greece[END_REF][START_REF] Soula | Thrustrelated, diapiric, and extensional doming in a frontal orogenic wedge: example of the Montagne Noire, Southern French Hercynian Belt[END_REF][START_REF] Weinberg | Diapiric ascent of magmas through power law crust and mantle[END_REF]Whitney et al., 2004b).

Diapirism may strongly shape migmatite domes as it generates a set of positive feedback scenarios (Whitney et al., 2004b). Vertical transfer of anatectic rocks during doming provokes near-isothermal decompression which enhances melting [START_REF] Rey | The role of partial melting and extensional strain rates in the development of metamorphic core complexes[END_REF]Whitney et al., 2004a). At increasing melt fractions, the viscosity drop and rheological transitions towards a magma behavior (Vanderhaeghe and Teyssier, 2001;Vanderhaeghe, 2009;[START_REF] Vigneresse | Rheological transitions during partial melting and crystallization with application to felsic magma segregation and transfer[END_REF] would ease the en-masse vertical ow of the partially molten crust and establish it as a self-sustained process. Numerical models show that buoyancy-driven ow does control the structure of extensional domes submitted to slow free-boundary extension [START_REF] Rey | Viscous collision in channel explains double domes in metamorphic core complexes[END_REF], a setting observed in the collapse of orogenic plateaux associated with divergence [START_REF] Rey | Gravitational collapse of the continental crust: denition, regimes and modes[END_REF]. Yet, such models do not investigate the case where dome formation is related to collapse at xed-boundary conditions.

This situation features substantial potential energy transfer between adjacent crustal domains [START_REF] Rey | Gravitational collapse of the continental crust: denition, regimes and modes[END_REF] partly accommodated by strike-slip tectonics which role during doming remains unclear (Lagarde and Dallain, 1994).

In this chapter, I attempt to: (i) evaluate the respective contributions of the regional strain eld vs. buoyancy-driven partially molten crust dynamics in determining the shape of migmatite domes formed during orogenic collapse; (ii) identify the parameters that control their regional distribution; (iii) characterize the petrogenesis of exhumed migmatites and associated granites; and (iv) investigate the behaviour of the

Geological setting

The Masméjean dome is located at the intersection between three main Variscan lithotectonic units from the eastern French Massif Central (Fig. 6.1 and 6.2). To the North-East, it anks the southern part of the Velay Complex, a 120x80 km granitemigmatite poly-diapiric dome that nucleated during orogenic collapse and is attributed to the Lower Gneiss Unit of Ledru et al. (1989) (see review in Ledru et al., 2001). The Margeride granite crops out to the West and corresponds to the largest intrusive batholith of the French Massif Central (Chantraine et al., 1996). To the South, lies one of the peripheral parautochton complexes (PAU) dened by Ledru et al. (1989).

The Velay Complex

General architecture The Velay Complex is an asymmetric granitemigmatite dome bounded to the North by a ductile extensional shear zone showing top-to-the N sense of shear (Malavielle et al., 1990) and referred hereafter as "Pilat Shear Zone" (Fig. 6.1).

The timing of its activity and associated dome exhumation is bracketed by the intrusion of the syntectonic "Goure d'Enfer" granite [START_REF] Vitel | Le granite du Goure d'Enfer (Massif central français). Pétrologie d'un marqueur tectonique varisque[END_REF] dated at 322 ± 9 (RbSr on whole-rock, [START_REF] Caen-Vachette | Age radiométrique du granite syntectonique du Goure d'Enfer et du métamorphisme hercynien dans la série de basse pression du Pilat[END_REF] and 301.8 ± 3.1 Ma (UPb on zircon, C. Chelle-Michou, personal communication). To the East, at-lying migmatites represent the dome roof, which is seen intruding the overlying Upper Gneiss Unit [START_REF] Anthonioz | Intérêt de l'analyse des déformations dans l'encaissant d'un granite pour interpréter la mise en place de la masse plutonique et ses relations avec le contexte : les cas du "dôme diapirique" hercynien du Velay (Massif Central français)[END_REF][START_REF] Lagarde | Contexte tetonique de la fusion crustale postcollision dans la chaîne hercynienne : l'exemple du complexe anatectique du Velay (Massif central français)[END_REF]Lagarde and Dallain, 1994;Ledru et al., 2001). The western and southern margins are steeply dipping with the dome being locally overturned to the South [START_REF] Burg | Structures and way-up criteria in migmatites, with application to the Velay dome (French massif Central)[END_REF]Lagarde and Dallain, 1994;Ledru et al., 2001). The strain pattern in the dome core features: (i) concentric structures regarded as intrusive, diapiric eects; (ii) vertical wrench ductile NS sinistral and NESW dextral shear zones (Dupraz and Didier, 1988;[START_REF] Lagarde | Contexte tetonique de la fusion crustale postcollision dans la chaîne hercynienne : l'exemple du complexe anatectique du Velay (Massif central français)[END_REF]Lagarde and Dallain, 1994;Ledru et al., 2001).

Tectonicmetamorphic evolution of its southern margin Recent river incision resulted in the southern margin being the best-exposed part of the dome (Fig. 6.2) and this area has accordingly been the subject of numerous studies reviewed in [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]. The southernmost part of the Velay Complex, separated from the main granite migmatite mass by the La Souche fault, corresponds to an EW trending sub-dome referred to as "Tanargue" dome in the following (Fig. 6.2). 2006); [START_REF] Briand | Carte géol[END_REF]; Choubert and Girod (1974a); [START_REF] Couturié | Carte géol. France (1/50 000[END_REF]; [START_REF] Dallain | Textural evolution in the transition from subsolidus annealing to melting process, Velay Dome, French Massif Central[END_REF]; [START_REF] Dumas | Le métamorphisme régional des Cévennes occidentales (Massif Central français) : une conséquence de la mise en place du dôme anatectique vellave[END_REF]; [START_REF] Faure | Le pluton du Pont-de-Montvert : un granite syntectonique extravasé vers l'Est pendant le désépaississement crustal varisque du Massif Central français[END_REF]; Faure (1995); [START_REF] Gèze | Carte géol[END_REF]1980); Négron (1979); [START_REF] Talbot | Emplacement in an extensional setting of the Mont LozèreBorne granitic complex (SE France) inferred from comprehensive AMS, structural and gravity studies[END_REF]2005); [START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF]; [START_REF] Viard | Lithostratigraphie et pétrologie des formations métamorphiques du versant nord du mont Lozère[END_REF] and [START_REF] Weisbrod | Carte géol[END_REF]. Abbreviations: M, Masméjean dome; T, Tanargue dome; p-j, PradesJaujac basin; b, Bessèges basin.

Constituent metamorphic rocks of the southern part of the Velay Complex include (Weisbrod, 1970): Ediacaran paragneisses from the "Série Cévenole" and late-Ediacaran orthogneisses from the "Série Ardéchoise" which are part of the "Velay Orthogneiss Formation" (see section 2.1). Scarce amphibolites corresponding to meta-alkali basalts are locally observed [START_REF] Bambier | Notice explicative, Carte géol[END_REF]Pin and Marini, 1993).

The main regional S n foliation is reworked by prominent NW-SE to E-W trending folds aecting all lithologies, with second-order asymmetric chevrons showing southdipping to vertical long limbs and horizontal short limbs [START_REF] Anthonioz | Analyse tectonique du socle de l'Ardèche (Massif Central français). Une lecture nouvelle d'un segment de la chaîne hercynienne[END_REF][START_REF] Macaudière | Grandes nappes synschisteuses collisionnelles dans la catazone hercynienne des Cévennes médianes (Massif Central, France)[END_REF][START_REF] Marignac | Evolution tectonométamorphique d'un segment de l'orogène hercynien : les Cévennes médianes, Massif Central français[END_REF]. Folding was synchronous with limited M 3 anatexis [START_REF] Laumonier | Relations entre tectoniques superposées, migmatisations et mise en place des granites sur l'exemple de la bordure sud du dôme du Velay (région de Laviolle, Ardèche, France)[END_REF][START_REF] Macaudière | Le stade initial de fusion dans le développement des dômes anatectiques : le dôme du Velay (Massif Central français)[END_REF] at T ∼ 720°C and P = 0.50.6 GPa (Ait Malek et al., 1995;[START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Montel et al., 1992). M 3 migmatites are generally metatexites (Fig. 6.2) and anatexis has been dated between 331 ± 4 (UThPb EPMA age on monazite, Be Mezeme et al., 2005a, Fig. 6.3 and 6.4) and 315 ± 5 Ma (UPb IDTIMS on monazite, Mougeot et al., 1997, Fig. 6.3 and 6.4).

A more intense M 4 melting event at T ≥ 800°C and P ∼ 0.4 GPa [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Montel et al., 1992) developed coevally to the intrusion of the Velay granite (Dupraz and Didier, 1988;[START_REF] Lagarde | Contexte tetonique de la fusion crustale postcollision dans la chaîne hercynienne : l'exemple du complexe anatectique du Velay (Massif central français)[END_REF][START_REF] Weisbrod | Relations pétrogénétiques entre les migmatites oeilées et le granite du Velay (Massif central français)[END_REF], dated at 305.9 ± 1.7 Ma (LA ICPMS UPb age on monazite, Couzinié et al., 2014, Fig. 6.3 and 6.4) and 301 ± 5 Ma (IDTIMS UPb age on monazite, Mougeot et al., 1997, Fig. 6.3 and 6.4). M 4 migmatites are mostly diatexites (Fig. 6.2).

The last increment of melting resulted in the intrusion of the so-called "late-migmatitic granites" between 307 ± and P = 0.40.6 GPa [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Montel et al., 1986). Given their overlapping emplacement ages, undistinguishable within errors, the main Velay phase and the "late-migmatitic granites" are grouped together in Fig. 6.2. Potassic diorites (locally called "vaugnerites") originating from melting of the orogenic mantle (see section 5.3) are commonly observed within the dome and yielded identical within error emplacement ages between 307.4 ± 3.9 and 305.8 ± 4.1 Ma (UPb zircon, Couzinié et al., 2014, andLaurent et al., 2017, taking into account systematic errors, Fig. 6.3 and6.4).

Contact between the migmatite dome and the overlying Cévennes schists

The contact corresponds to a high-temperature mylonite (Fig. 6.2) referred to as "Metamorphic Mylonitic Vellave Zone (MMVZ, Bouilhol et al., 2006). In the BtSil zone, the deformation features: (i) a non-negligible pure shear component and (ii) stretching lineation perpendicular to the domeschists contact with a top-to-the S sense of a shear (Bouilhol et al., 2006). According to these authors, this pattern would reect the diapiric ascent of the migmatite dome piercing through its metasedimentary cover and accounts for the constriction of the AndCrdBt zone in the Cévennes schists (see below and Fig.

6.2)

. At the contact between migmatites and schists lies the Rocles syntectonic granite [START_REF] Weisbrod | Relations structurales et chronologiques entre le magmatisme basique, les granitisations et l'évolution tectonométamorphique tardihercynienne dans les Cévennes Médianes, Massif Central Français[END_REF] showing a well-dened ENEWSW trending magnetic lineation (Be [START_REF] Be Mezeme | Structural, AMS and geochronological study of a laccolith emplaced during Late Variscan orogenic extension: the Rocles pluton (SE French Massif Central)[END_REF] and for which a range of ages have been obtained, from 325 ± 5 Ma (UThPb EPMA dating of monazite, Be Mezeme et al., 2006) Timing of dome exhumation Top-to-the S shearing in the MMVZ has been dated at 310.7 ± 2 Ma and cooling at 307.5 ± 3.4 Ma (monazite EPMA UThPb and biotite ArAr ages, respectively, Bouilhol et al., 2006, Fig. 6.3). Migmatites and granites are unconformably overlain by the PradesJaujac detrital basin and found within its basal conglomerate (Bouilhol et al., 2006). The zircon UPb age of 296 ± 6.8 Ma (SIMS, Bruguier et al., 2003, Fig. 6.3 and 6.4) obtained from bentonites indicate that highgrade rocks were already exposed at surface level by that time. This is consistent with the migmatites and granite UPb apatite cooling ages ranging between 292 ± 6 and 286 ± 5 Ma (Mougeot et al., 1997, Fig. 6.3 and 6.4).

The Cévennes schists

Lithologies The Cévennes schists are composed of two main litho-tectonic units. The "Joyeuse/Cézarenque" series are built up by greenschist-facies metasediments and calcalkaline Bt-bearing augen gneisses [START_REF] Crevola | Origine granitique des gneiss de la Cézarenque (Cévennes, Massif Central) : identication de plusieurs faciès plutoniques originels[END_REF][START_REF] Elmi | Notice explicative, Carte géol[END_REF]) of unknown age. The "Cévenole" series comprise greenschist-to amphibolite-facies micaschists and quartzites corresponding to a metamorphosed CambrianOrdovician terrigenous sedimentary sequence (Faure et al., 2009).

Intruding granitoids The Cévennes schists are intruded by a set of igneous rocks:

the Signaux batholith [START_REF] Brichau | New age constraints on emplacement of the Cévenol granitoids, South French Massif Central[END_REF], itself composed of the Laubies adamellite, the Finiels and Bougès granites. Those granitoids are peraluminous, show magmatic muscovite and/or cordierite (Guérangé-Lozes and [START_REF] Guérangé-Lozes | Notice explicative, Carte géol[END_REF][START_REF] Sabourdy | Premiers résultats de l'étude géochimique des granites grenus à biotite et à deux micas du Mont Lozere (Massif Central français)[END_REF] and thus belong to the MPG/CPG types of [START_REF] Barbarin | A review of the relationships between granitoid types, their origins and their geodynamic environments[END_REF], hence their crustal origin.

the Pont-de-Monvert, Rabeyrals, Borne and Largentière plutons. All these granitoids are Kfs-porphyritic, contain mac amphibole-bearing enclaves (Guérangé-Lozes and [START_REF] Guérangé-Lozes | Notice explicative, Carte géol[END_REF] and are intimately associated with vaugnerites (Couzinié et al., 2014) suggesting that they belong to the KCG type of [START_REF] Barbarin | A review of the relationships between granitoid types, their origins and their geodynamic environments[END_REF]. They would thus represent mac magma dierentiates (Laurent et al., 2017;Moyen et al., 2017a).

plutonic to volcanic (lamprophyre and rhyolite) dykes. These rocks are locally widespread, for instance east of the Borne granite or south of the Mont-Lozère pluton (Alabouvette et al., 1988;[START_REF] Chauvet | Geochronological and geochemical characterization of magmatic-hydrothermal events within the Southern Variscan external domain (Cévennes area, France)[END_REF]Laurent et al., 2017;[START_REF] Weisbrod | Carte géol[END_REF].

Structures Polyphase deformation aected the Cévennes schists. Early top-to-the WNW thrusting (D 1 , Table 6.1) generated kilometer-scale folds with a NS to NESW axial planar foliation [START_REF] Arthaud | La direction des plis couchés penniques de la phase majeure hercynienne est subméridienne dans les Cévennes méridionales[END_REF][START_REF] Brouder | Les étapes de formation d'un édice hercynien polyphasé : les Cévennes (Massif central, France)[END_REF]. NW-SE trending stretching lineations with a top-to-the-NW sense of shear are described in the eastern Cévennes (Bouilhol et al., 2006). This event would have juxtaposed the "Joyeuse/Cézarenque" series over the "Cévenole" series [START_REF] Barbey | Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France)[END_REF]Bouilhol et al., 2006). Both units were subsequently aected by top-to-the SSW shearing (D 2 ) coeval with the development of EW trending folds overturned to the South [START_REF] Arnaud | Shear structures and microstructures in micaschists: the Variscan Cévennes duplex (French Massif Central)[END_REF][START_REF] Arthaud | La direction des plis couchés penniques de la phase majeure hercynienne est subméridienne dans les Cévennes méridionales[END_REF][START_REF] Brouder | De la présence de nappes-plis de style pennique dans une série métamorphique hercynienne[END_REF]Faure et al., 1999;2001;[START_REF] Lacassin | Analyse de la déformation hercynienne majeure des gneiss de la Cézarenque (Cévennes, Massif-Central)[END_REF]. Close to the Tanargue dome, the micaschists display a NESW trending stretching lineation but with a top-to-the NE sense of shear (Bouilhol et al., 2006;[START_REF] Faure | Tectonic evolution of the Cévennes para-autochtonous domain of the Hercynian French Massif Central and its bearing on ore deposits formation[END_REF] pinpointing an apparent transport of the metasediments over the Velay dome (D 2 v). Intrusion of the Rocles granite would be coeval to this deformation phase (Be [START_REF] Be Mezeme | Structural, AMS and geochronological study of a laccolith emplaced during Late Variscan orogenic extension: the Rocles pluton (SE French Massif Central)[END_REF]. Finally, a late ductile deformation increment (D 3 ) featuring WNWESE trending lineations would have developed in an extensional context (Faure, 1995;Faure et al., 1999;2001).

Shear criteria indicate top-to-the-ESE and top-to-the WNW transport in the eastern and western Cévennes, respectively (Faure et al., 1999;2001). Structural studies were conducted on the Pont-de-Monvert and Borne plutons using conventional [START_REF] Faure | Le pluton du Pont-de-Montvert : un granite syntectonique extravasé vers l'Est pendant le désépaississement crustal varisque du Massif Central français[END_REF]Faure, 1995) and magnetic (AMS) methods together with gravimetry [START_REF] Faure | Tectonic evolution of the Cévennes para-autochtonous domain of the Hercynian French Massif Central and its bearing on ore deposits formation[END_REF][START_REF] Talbot | AMS study of the Pont-de-Montvert-Borne porphyritic granite pluton (French Massif Central) and its tectonic implications[END_REF]2004). They identied a magma feeding zone west of the Pont-de-Montvert granite and showed that this pluton expanded eastwards in a regional EW extensional context. The Borne pluton would rather be tabular and shows a ENEWSW trending horizontal magmatic lineation (Fig. 6.2).

Because of their petrological similarities, the Borne and Pont-de-Montvert plutons have often been regarded as formerly being part of single batholith subsequently dismembered by the NS trending Villefort fault (Fig. 6.2, [START_REF] Arthaud | Les décrochements tardi-hercyniens du Sud-Ouest de l'Europe. Géométrie et essai de reconstitution des conditions de la déformation[END_REF][START_REF] Deroin | Fracturation tardi-hercynienne et détritisme associé : chronologie des évènements dans les massifs granitiques cévenols décrochés par la faille de Villefort (Mont Lozère et Borne, Massif Central, France)[END_REF][START_REF] Lapadu-Hargues | Les massifs de la Margeride et du mont Lozère et leurs bordures[END_REF]. Using both batholiths as passive markers, a lateral displacement of 12 km has been proposed (Deroin and Prost, 1993a;[START_REF] Deroin | Cartographie géologique en Velay : aspects méthodologiques de l'étude par télédétection et présentation des résultats[END_REF][START_REF] Lapadu-Hargues | Les massifs de la Margeride et du mont Lozère et leurs bordures[END_REF]. Finally, EW trending dextral to inverse faults (i.e. the Goulet and Orcières faults) were active in the Cenozoic [START_REF] Briand | Notice explicative, Carte géol[END_REF].

Metamorphism and chronological constraints Caron (1994) investigated the "Joyeuse/Cézarenque" series and reported a set of biotite, muscovite and amphibole ArAr ages that cluster around 340 Ma (Fig. 6.3 and 6.4). In this area, deformation during both the D 1 and D 2 events occurred under greenschist-facies conditions (Elmi et al., 1974).

Given the closure temperatures of the analysed minerals, the date of c. 340 Ma may correspond either to the age of top-to-the NW shearing or top-to-the SSW thrusting (Table 6.1).

Largely disputed are the temporal relationships between top-to-the SSW thrusting and the regional metamorphism of the Cévennes schists. [START_REF] Arnaud | Microstructures des mylonites schisteuses : cartographie des chevauchements varisques dans les Cévennes et détermination de leur cinématique[END_REF]; [START_REF] Arnaud | Shear structures and microstructures in micaschists: the Variscan Cévennes duplex (French Massif Central)[END_REF] and Faure et al. (1999;2001) argued that both were coeval and regarded regional metamorphism as a prograde Barrowian sequence. In contrast, [START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF] showed that mineral isograds actually cut across the main thrusts and that metamorphism post-dates D 2 .

Figure 6.2 highlights that the AndCrdBt zones coalesce at the scale of the whole northern Cévennes, outlining a single amphibolite-facies domain wrapping around the Velay dome [START_REF] Weisbrod | Les conditions du métamorphisme dans les Cévennes médianes (Massif Central, France)[END_REF]) and intruding granites (Bouilhol et al., 2006). The latter developed thermal aureoles marked by the restoration of And and Crd blasts, indicating that intruded micaschists were part of the regional AndCrdBt zone [START_REF] Briand | Notice explicative, Carte géol[END_REF]. As a direct consequence of this, granite magmatism was coeval or postdated regional metamorphism. Available geochronological constraints on igneous rocks and their metamorphic aureoles (Fig. 6.3) argue for a protracted magmatic activity with emplacement of the Cévennes granitoids over a period of c. 15 Ma from 316 ± 4 (Ma intrusion of the Bougès granite, IDTIMS UPb monazite age of Isnard, 1996) to 298.9 ±

3.8 Ma (intrusion of the Largentière granite, LAICPMS UPb zircon age, recalculated from Laurent et al., 2017, Fig. 6.3 and 6.4).

In the vicinity of the Velay dome, top-to-the NE shearing (the D 2v event) has been dated in situ by Bouilhol et al. (2006) on syntectonic muscovite at c. 320 Ma (Fig. 6.3, Table 6.1). Following Rakib's interpretation, the muscovite ages of c. 320 Ma probably represent the age of the regional greenschist-to amphibolite-facies metamorphism, thus implying that the D 2 thrusting event is older than 320 Ma. The younger ArAr biotite ages of 310307 Ma obtained by Bouilhol et al. (2006) close to the dome would correspond to cooling ages. D 3 extensional deformation would have been coeval to the intrusion of the Pont-de- Montvert and Borne granites (Faure, 1995;Faure et al., 1999;2001). Available ages for the former are inconsistent with a biotite ArAr cooling age of 310.8 ± 4 Ma (François, 2009), statistically dierent and older than the zircon UPb date of 302.5 ± 3.5 Ma (LAICPMS, recalculated from Laurent et al., 2017). Similarly, emplacement of the Borne granite is poorly constrained by a wholerock RbSr date of 315 ± 5 Ma [START_REF] Mialhe | Le massif granitique de la Borne (Cévennes). Etude pétrographique, géochimique, géochronologique et structurale[END_REF]. According to Bouilhol et al. (2006), the D 3 event postdated the intrusion of the Borne granite and led to the formation of the Bessèges coal basin (Fig. 6.

2). Zircon

UPb dating of bentonite in the latter yielded an age of 297.4 ± 4.4 Ma (Bruguier et al., 2003, Fig. 6.3 and 6.4) bracketing the age of D 3 between c. 315 and 300 Ma.

The Margeride pluton

The Margeride pluton is composed of several granitoid types (Couturié, 1977;[START_REF] Choubert | Notice explicative, Carte géol[END_REF][START_REF] Couturié | Notice explicative, Carte géol. France (1/50 000[END_REF]Lafon and Respaut, 1988):

a largely dominant Bt-bearing, Kfs-porphyritic, peraluminous granite. potassic diorites ("vaugnerites") showing mingling and mixing textures with the main phase. muscovite-bearing leucogranites (i.e. the Grandrieu massif ) cutting across the main phase.

late microgranite, lamprophyre and rhyolite dykes.

Recent geochronological investigations (Laurent et al., 2017) yielded intrusion ages identical within uncertainties for the porphyritic phase, the vaugnerites and the leucogranites, between 313.2 ± 4.3 Ma and 309.4 ± 3.8 Ma (recalculated considering systematic errors). This batholith has also been the subject of structural studies using conventional and magnetic data together with gravimetric investigations (Feybesse et al., 1995;[START_REF] Laboue | Etude structurale du massif de la Margeride[END_REF][START_REF] Talbot | Pull-apart emplacement of the Margeride granitic complex (French Massif Central). Implications for the late evolution of the Variscan orogen[END_REF]. The nearly at-lying magmatic foliation displayed by the porphyritic granites complies with an extensional setting while NWSE trending magmatic lineations with top-to-the SE sense of shear point to SEdirected expansion during magma emplacement (Feybesse et al., 1995;[START_REF] Talbot | Pull-apart emplacement of the Margeride granitic complex (French Massif Central). Implications for the late evolution of the Variscan orogen[END_REF].

The Masméjean dome

The Masméjean dome was rst described by [START_REF] Lapadu-Hargues | Les massifs de la Margeride et du mont Lozère et leurs bordures[END_REF] and subsequently investigated by [START_REF] Anthonioz | Intérêt de l'analyse des déformations dans l'encaissant d'un granite pour interpréter la mise en place de la masse plutonique et ses relations avec le contexte : les cas du "dôme diapirique" hercynien du Velay (Massif Central français)[END_REF]; Be Mezeme et al. (2006); [START_REF] Briand | Notice explicative, Carte géol[END_REF][START_REF] Faure | Tectonic evolution of the Cévennes para-autochtonous domain of the Hercynian French Massif Central and its bearing on ore deposits formation[END_REF]; Négron (1979) and [START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF]. The geological map presented Fig. 6.5

was drawn based on these works and our own eld survey.

General overview and constituent lithologies The Masméjean dome is a triangular shaped antiform showing gently dipping southwestern and northwestern anks that contrast with the steep eastern ank (Fig. 6.5). The dome is built up by an anatectic orthogneiss core mantled by an association of unmolten amphibolite-facies orthogneisses and metasediments. One orthogneiss sample has been dated section 2.1 and yielded a zircon UPb emplacement age of 541.4 ± 4.9 Ma (taking into account systematic errors, Fig. 6.3 and 6.4). Be Mezeme et al. (2006) obtained EPMA monazite ages of 323 ± 3 Ma and 543 ± 25 Ma from an anatectic orthogneiss which they interpret as reecting the timing of partial melting and protolith emplacement, respectively. A single plurimetric amphibolite body was observed near the place known as Les Orts [START_REF] Briand | Notice explicative, Carte géol[END_REF].

Metasedimentary lithologies comprise paragneisses, micaschists and quartzites assumed to derive from a range of protoliths including greywackes, pelites and sandstones [START_REF] Briand | Notice explicative, Carte géol[END_REF]Négron, 1979). The metasediments structurally overlay the orthogneisses or constitute metric to kilometric rafts embedded into them.

Our map diers from those of [START_REF] Briand | Carte géol[END_REF] and Négron (1979) as it emphasizes the existence of hectometer-scale granite sills outlining the contact between migmatites and metasediments in the eastern ank of the antiform (Fig. 6.5). Those correspond to the "granulites de ségrégation" of [START_REF] Lapadu-Hargues | Les massifs de la Margeride et du mont Lozère et leurs bordures[END_REF] and will be referred to as "Villefort granites" hereafter. Post-tectonic leucogranite, microgranite to rhyolite dykes are frequently observed in and out of the anatectic domain. Be Mezeme et al. (2006) reported an EPMA monazite age of 333 ± 6 Ma for a granite dyke but did not quote the exact GPS coordinates. Finally, Variscan igneous and metamorphic rocks are unconformably overlain by Lower Jurassic shallow marine limestones [START_REF] Briand | Notice explicative, Carte géol[END_REF].

Relationships between the Masméjean dome and adjacent units Near Labastide-Puylaurent, the steep NS foliation of the eastern ank of the Masméjean dome gradually rotates to an NESW and then EW trend matching that displayed by the Tanargue migmatites [START_REF] Briand | Carte géol[END_REF][START_REF] Lapadu-Hargues | Les massifs de la Margeride et du mont Lozère et leurs bordures[END_REF]. The persistence of anatexis indicates that a petrological continuity exists between the Masméjean dome and the southern part of the Velay Complex (Be Mezeme et al., 2006).

To the South, the Masméjean dome is brought to contact with the Cévennes schists by the Goulet strike-slip to inverse Pyrenean fault [START_REF] Briand | Notice explicative, Carte géol[END_REF]. To the east, the contact is gradual yet locally dissected by the Villefort fault and notably features the above-mentioned granite sills. SW of Prévenchères, anatectic orthogneisses similar to those observed in the dome constitute the core of a kilometric antiform within the Cévennes schists [START_REF] Briand | Carte géol[END_REF]Négron, 1979;[START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF]. Altogether, these observations suggest that the constitutive lithologies of the Masméjean dome were located structurally below the Cévennes schists.

Finally, the Margeride batholith is intrusive within amphibolite-facies metasediments from the northwestern ank of the dome and developed a limited contact metamorphic aureole [START_REF] Briand | Carte géol[END_REF].

6.2 Structural analysis and kinematic criteria Figure 6.5: Geological map at scale 1/80,000 of the Masméjean dome. Drawn after our survey and the works of [START_REF] Briand | Carte géol[END_REF]; Négron (1979); [START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF] and [START_REF] Weisbrod | Carte géol[END_REF]. A, B and C refer to the edges of the cross-sections Fig. 6.6. Unmolten rocks from southwestern ank have been intruded by several types of granitic magmas, forming dykes cutting across the foliation or sills concordant within it (Fig. 6.10d, e, f ). Importantly, top-to-the NEENE shearing was coeval to post-dated granitic magmatism as documented by folded granite veinlets within metasediments (see Fig. 6.9c). Locally, S n shows non-penetrative surface lineations associated with top-to-

the SE shearing at the brittle-ductile transition (Fig. 6.10e).

The northwestern ank of the dome

In this domain, stretching lineations are very scarce and, when observed, gently plunge to the NW. Locally, a top-to-the SE sense of shear has been determined (Fig. 6.11). Local folds with vertical axial planes and gently NW-plunging hinges aected orthogneisses.

The eastern ank of the dome

The S n foliation is NS trending and steeply dipping towards the E (on average at 55 • ).

Migmatites are overlain by quartz-rich paragneisses intruded by numerous granite sills, the "granulites de segregation" of Lapadu-Hargues ( 1947 dominantly NS trending and horizontal while a subordinate population gently plunges to the ESE (Fig. 6.8b). Left-lateral sense of shear is marked by asymmetric quartz aggregates and shear bands (Fig. 6.12c,d,e,f ).

Most lithologies are aected by brittle deformation along NS steeply dipping fracture and fault planes, related to the Villefort fault activity [START_REF] Deroin | Fracturation tardi-hercynienne et détritisme associé : chronologie des évènements dans les massifs granitiques cévenols décrochés par la faille de Villefort (Mont Lozère et Borne, Massif Central, France)[END_REF]Deroin and Prost, 1993a;[START_REF] Lapadu-Hargues | Les massifs de la Margeride et du mont Lozère et leurs bordures[END_REF]. Horizontal non penetrative lineations (striations) have been described by [START_REF] Deroin | Fracturation tardi-hercynienne et détritisme associé : chronologie des évènements dans les massifs granitiques cévenols décrochés par la faille de Villefort (Mont Lozère et Borne, Massif Central, France)[END_REF] and probably represent the latest increments of strike-slip deformation. The present-day dierential altitude of the Triassic unconformity on both sides of the fault (200-300 m higher to the west) suggests a late normal movement where the footwall moved up to the west. This is supported by results of apatite ssion track thermochronology documenting an inverse elevationage prole across the fault [START_REF] Barbarand | Burial and exhumation history of south-eastern Massif Central (France) constrained by apatite ssion-track thermochronology[END_REF].

Altogether, these observations indicate that the eastern ank of the Masméjean dome constitutes a wrench corridor marked by an early phase of ductile strike-slip deformation continued at brittle conditions during exhumation. Post-Variscan reactivation as a normal fault, most likely related to Pyrenean events, uplifted the western compartment including the Masméjean dome by c. 200 m. In the following, this structure will be referred to as "Villefort Shear Zone" (VSZ). The magnetic fabrics of the granite sills cartographically aligned along the VSZ are presented section 6.2.3.

Field observations and petrography of the core migmatites

The dome core typically features migmatites developed at the expense of orthogneisses (most often augen). Best exposures are found at the Puylaurent dam (where samples CHA-15-17 and 65 were collected, see Fig. 6.5). They dominantly consist in stromatic metatexites featuring: (i) 10 mm large in-situ leucosomes of granitic texture and composition with an assemblage Qz+Pg+Kfs±Bt±Ms±Sil; and (ii) narrow 1 to 2 mm large melanosomes consisting in Bt±Ms (Fig. 6.13a,b and 6.14). A second generation of muscovite formed during retrogression at the expense of sillimanite (when present, see Fig.

6.14a

). Biotite was locally converted into chlorite at subsolidus conditions. Accessory phases include rutile, ilmenite, apatite and zircon.

In-situ leucosome distribution within fold hinges (Fig. 6.13d) presumably reects the collection of anatectic liquids in low-strain domains during syn-anatectic deformation.

The presence of larger, 10 cm thick concordant to discordant in-source leucosomes (in the sense of Sawyer, 2008, see Fig. 6.13a,b) is taken as evidence for melt mobility and coalescence, associated Bt-and Kfs-rich layers being regarded as residual domains. Granitic veins showing intricate and gradual transitions with their host metatexites are common (e.g. Fig. 6.13e,f ) and would represent former melt percolation channels/pathways.

Rafts of quartz-rich paragneiss resisters have been observed in several parts of the dome together with scarce intrusions of vaugnerites (Fig. 6.13d). The latter are intricately associated with Qz+Pg+Bt pegmatites, presumably corresponding to: (i) fractionated magmatic liquids derived from them (Montel and Weisbrod, 1986); or (ii) local melts from surrounding lithologies formed as a result of mac magma intrusion.

Along the western and eastern limbs, the metatexite eld foliation trajectories (when they can be reasonably mapped) tend to mimick that of the dome mantle (Fig. 6.2)

and feature a similar asymmetry (steeply vs. gently dipping eastern/western anks, respectively). In the dome core, the migmatite foliation turns horizontal and cascading folds admitting the foliation as axial plane have been observed. In contrast, linear fabrics were not identied.

AMS study of the dome core

Why AMS?

For the past 15 years, the study of gneiss domes has beneted from the spatial analysis of the anisotropy of magnetic susceptibility in migmatites [START_REF] Bascou | Contribution of AMS measurements in understanding the migmatitic terrains of Pointe Géologie, Terre Adélie (East-Antarctica)[END_REF][START_REF] Cavalcante | Strain distribution across a partially molten middle crust: Insights from the AMS mapping of the Carlos Chagas Anatexite, Araçuaí belt (East Brazil)[END_REF][START_REF] Charles | The Montagne Noire migmatitic dome emplacement (French Massif Central): new insights from petrofabric and AMS studies[END_REF][START_REF] Ferré | Magnetic susceptibility anisotropy: A new petrofabric tool in migmatites[END_REF][START_REF] Ferré | Paramagnetic and ferromagnetic anisotropy of magnetic susceptibility in migmatites: measurements in high and low elds and kinematic implications[END_REF][START_REF] Kruckenberg | Viscoplastic ow in migmatites deduced from fabric anisotropy: An example from the Naxos dome, Greece[END_REF][START_REF] Stern | Subduction erosion: Rates, mechanisms, and its role in arc magmatism and the evolution of the continental crust and mantle[END_REF][START_REF] Parsons | Orogenparallel deformation of the Himalayan midcrust: Insights from structural and magnetic fabric analyses of the Greater Himalayan Sequence, Annapurna-Dhaulagiri Himalaya, central Nepal[END_REF][START_REF] Teyssier | Flow of partially molten crust and origin of detachments during collapse of the Cordilleran Orogen[END_REF][START_REF] Viegas | Fabrics of migmatites and the relationships between partial melting and deformation in high-grade transpressional shear zones: The Espinho Branco anatexite (Borborema Province, NE Brazil)[END_REF]. One of the reason for this lies in the fact that mineral and/or stretching lineations are very dicult to observe in migmatites. The ability to measure a magnetic lineation is thus highly informative as it allows to retrieve the transport/ow direction within the dome anatectic cores. Similarly, AMS studies have proven very successful in deciphering the internal fabrics of granite bodies, otherwise very challenging to image for lack of prominent tectonic markers.

Many studies since the 80's have shown that the magnetic fabrics of molten rocks depend on both the regional strain pattern and the internal buoyancy-driven magma dynamics [START_REF] Benn | Syn-Acadian emplacement model for the South Mountain batholith, Meguma terrane, Nova Scotia: Magnetic fabric and structural analyses[END_REF]2001;[START_REF] Bouchez | Two-stage deformation of the Mont-Louis-Andorra granite pluton (Variscan Pyrenees) inferred from magnetic susceptibility anisotropy[END_REF][START_REF] Gleizes | Variscan granites of the Pyrenees revisited: their role as syntectonic markers of the orogen[END_REF][START_REF] Guillet | Anisotropy of magnetic susceptibility and magmatic structures in the Guérande granite massif (France)[END_REF]. In order to better constrain the strain pattern of the inner, anatectic part of the Masméjean dome, an AMS study has been conducted focusing on the core migmatites and the granite bodies cartographically aligned along the eastern ank of the dome.

Sampling and analytical methods

One hundred and two rock cores of 2.5 cm in diameter were collected at 11 sites with a gasoline-powered drill. Investigated rocks correspond to 6 metatexites and 5 Villefort granites (out of which 3 have been analysed for zircon and monazite UPb isotopes).

Cores were oriented with a magnetic compass and subsequently cut in the lab to obtain specimens of standard size (2.2 cm in length; N specimen = 145). Magnetic fabric measure- ments were performed at Saint-Etienne University using a AGICO MFK1 Kappabridge magnetic susceptometer (Agico, Brno). The revealed AMS ellipsoid is dened by the three principal axes K 1 , K 2 and K 3 (K 1 ≥ K 2 ≥ K 3 ) mutually orthogonal. The parameters P' and T [START_REF] Jelínek | Characterization of the magnetic fabric of rocks[END_REF] were calculated to describe respectively the anisotropy and the shape of the fabric. Data retrieved from a group of specimen were processed using normalized tensor variability statistics [START_REF] Hext | The estimation of second-order tensors, with related tests and designs[END_REF][START_REF] Jelínek | Statistical processing of anisotropy of magnetic susceptibility measured on groups of specimen[END_REF]. The results of all magnetic measurements are reported Table B18.

Magnetic mineralogy

Bulk magnetic susceptibilities (K m ) are very low (mostly <150.10 -6 SI in granites, <100.10 -6 SI in migmatites, see Fig. 6.15) and in the typical range of Al-rich crust- derived granites [START_REF] Bouchez | Anisotropie de susceptibilité magnétique et fabrique des granites[END_REF]. Besides, there is no correlation between the degree of magnetic anisotropy P' and the bulk susceptibility (Fig. 6.16b). These features indicate that the magnetic susceptibility is controlled by paramagnetic minerals [START_REF] Borradaile | Tectonic applications of magnetic susceptibility and its anisotropy[END_REF][START_REF] Charles | The Montagne Noire migmatitic dome emplacement (French Massif Central): new insights from petrofabric and AMS studies[END_REF][START_REF] Kruckenberg | Viscoplastic ow in migmatites deduced from fabric anisotropy: An example from the Naxos dome, Greece[END_REF][START_REF] Rochette | Rock magnetism and the interpretation of anisotropy of magnetic susceptibility[END_REF]. The lack of magnetite in our specimens has been conrmed by thermomagnetic KT curves.

Amongst paramagnetic minerals characterized by a high magnetic susceptibility (Borradaile and Henry, 1997), ilmenite was observed as (i) isolated grains in the specimen matrices; and, (ii) exsolutions within biotite/chlorite cleavage planes. Biotite is ubiquitously present in all specimens while garnet is particularly abundant in the Villefort granite sampled at site 10.

Magnetic fabrics

AMS parameters Rocks sampled at each site show low degrees of anisotropy (Fig. 6.16a), between 1.05 (0.5%) and 1.18 (1.8%) with an AMS ellipsoid shape being triaxial (T close to 0) in two Villefort granites (at site 5, dated sample CHA-15-41, and site 10) Structures in metatexites In metatexites, the magnetic foliation (which pole is dened by K 3 , Fig. 6.17) pattern is consistent with that retrieved from eld observations:

(i) gently dipping towards the SW in the southwestern ank (S4 and 9) and the ENE in the eastern ank (S6); (ii) sub-horizontal in the inner core (S3 and 11). Metatexites sampled along the western ank display a vertical NNWtrending foliation (S7). When clearly dened, magnetic lineations (direction of K 1 ) are horizontal, NNW-trending in the western ank (S7) and plunge to the WSW in both the SW ank (S4 and 9) and the southern part of the inner core (S3).

Structures in granites Granites cropping out along the Villefort shear zone feature very contrasted AMS ellipsoids (Fig. 6.17 Finally, the poorly anisotropic Grt-bearing granite S10 tends to show a vertical magnetic foliation and an EW magnetic lineation.

Origin of the observed fabrics

Magnetic foliation poles are well-dened in all but one investigated site (S10). A the mineral scale, the <001> direction of biotite crystals corresponds to that of K 3 (Borradaile and Alford, 1987; Kruckenberg et al., 2010; Martín-Hernández and Hirt, 2003; Viegas et al., 2013; Zapletal, 1990). Therefore, since biotite is the most abundant paramagnetic mineral, the magnetic foliation would reect the subparallel alignment of biotite crystals and thus the sample eld foliation. Figure 6.17: Projection of AMS data obtained for each sampling site of the Masméjean dome. AMS ellipsoid principal axes are projected onto lower hemisphere (equal area projection) and shown with 95% condence ellipses. Same legend as Fig. 6.5. Full set of data presented Table B18.

In the absence of magnetite, the magnetic lineation may originate from: (i) preferred shape orientation of ilmenite grains [START_REF] Bascou | Titanohematite lattice-preferred orientation and magnetic anisotropy in high-temperature mylonites[END_REF][START_REF] Bolle | Anisotropy of magnetic susceptibility versus lattice-and shape-preferred orientation in the Lac Tio hemo-ilmenite ore body (Grenville province, Quebec)[END_REF][START_REF] Borradaile | Tectonic applications of magnetic susceptibility and its anisotropy[END_REF] or (ii) the zone axis distribution of biotite crystals [START_REF] Kruckenberg | Viscoplastic ow in migmatites deduced from fabric anisotropy: An example from the Naxos dome, Greece[END_REF]. To test the rst hypothesis, thin sections were made in the K 1 K 2 plane of cores showing a well-dened magnetic lineation. They did not provide evidence for any preferred orientation of ilmenite crystals which are randomly oriented. Therefore, zone axis orientation of biotite crystals is preferred. In this frame, the concurrence of welldened magnetic foliation and lineation, as observed in samples from sites 3, 4, 5, 7 and 9, would originate from the presence of an anastomosed network of biotite folia [START_REF] Kruckenberg | Viscoplastic ow in migmatites deduced from fabric anisotropy: An example from the Naxos dome, Greece[END_REF].

The low anisotropy of the AMS ellipsoid displayed by the granite from site 10 most likely originates from the local predominance of garnet over biotite. Indeed, garnet features elevated bulk magnetic susceptibilities, of the same order of magnitude than biotite, but characteristically low anisotropy degrees [START_REF] Rochette | Rock magnetism and the interpretation of anisotropy of magnetic susceptibility[END_REF]. Consequently, the presence of garnet would substantially smoothen the anisotropic signal carried by biotite.

Interpretation

Migmatites In metatexites, the magnetic foliation and lineation would record the visco-plastic ow planes and direction of ow, respectively [START_REF] Kruckenberg | Viscoplastic ow in migmatites deduced from fabric anisotropy: An example from the Naxos dome, Greece[END_REF].

Following this, the set of gently dipping magnetic lineations observed in the SW part of the dome (S4 and 9) may reect the NEE-directed upward ow of the migmatites, leading to dome exhumation. Horizontal lineation in the dome core (S3) possibly indicates non-coaxial attening or could alternatively be "inherited" from an early exhumation stage along the SW ank. Importantly, the magnetic pattern observed in the northern part of the dome markedly diers from that of the southern and eastern parts as only scarce evidence for horizontal NNWSSE-directed ow are preserved (S7). In the two remaining sites (S6 and 11), no preferred ow direction can be identied which supports a coaxial deformation regime. Consequently, the bulk of dome exhumation would have taken place in its southern part.

Villefort granites The vertical magnetic foliation displayed by granite S5 is consistent with the observed magmatic layering and suggests that the magnetic fabric reects magmatic ow structures [START_REF] Bouchez | Anisotropie de susceptibilité magnétique et fabrique des granites[END_REF]. This way, the at-lying magnetic lineation would indicate syn-magmatic horizontal shearing and entail that S5 granite intrusion was coeval to wrenching along the Villefort Shear Zone. The magnetic foliations of granites S1, 2 and 8 are concordant to oblique with respect to that of the VSZ and these samples lack any magnetic lineation. It suggests that those bodies intruded and crystallized during a period of tectonic quiescence or after the end of the VSZ activity.

Conclusion

The dome is asymmetric in several respects: (i) eld and magnetic foliations are gently vs.

steeply dipping in its western and eastern parts, respectively; (ii) the AndBtCrd metamorphic zone is markedly narrower to the East, with the transition between migmatites and greenschist-facies rocks occurring in 100m; (iii) granite bodies are dominantly observed in its eastern ank. Such asymmetry is governed by ductile left-lateral shearing along the Villefort Shear Zone and entails that the latter controlled the dome shape and acted as a drain for anatectic liquids produced in the dome core.

AMS measurements performed on the core migmatites suggest that bulk ow and associated exhumation was focused in the southwestern part of the dome and mostly proceeded along shallow SW-dipping planes with a bulk transport towards the NE at an angle of c. 30 • . In addition, foliation attening and the presence of cascading folds attest to vertical expansion, i.e. ination of the dome core in line with buoyancy-driven ow [START_REF] Brun | Extensional gneiss domes and detachement fault systems : structure and kinematics[END_REF][START_REF] Chen | The Kangmar Dome: A Metamorphic Core Complex in Southern Xizang (Tibet)[END_REF][START_REF] Escuder Viruete | P-T paths derived from garnet growth zoning in an extensional setting: an example from the Tormes Gneiss Dome (Iberian massif, Spain)[END_REF].

Importantly, kinematic criteria indicate that the southwestern dome mantle was pervasively aected by top-to-the NE shearing resulting in the development of Smylonites, notably at the paragneiss/orthogneiss interface. Structural observations thus point to an apparent thrusting of the mantle over the core. Similar relationships have been reported

in the adjacent Tanargue dome (Bouilhol et al., 2006) and, at a regional scale, top-to-the NE shearing is attributed to the D 2 v tectonic-metamorphic event, presumably as old as 320 Ma (Be [START_REF] Be Mezeme | Structural, AMS and geochronological study of a laccolith emplaced during Late Variscan orogenic extension: the Rocles pluton (SE French Massif Central)[END_REF]Bouilhol et al., 2006).

A geochronological survey was conducted to address the timing of: (i) top-to-the NE shearing; (ii) wrenching along the Villefort Shear Zone; (iii) anatexis within the dome core; (iv) exhumation and brittleductile top-to-the S deformation. We targeted a range of igneous rocks, from orthogneisses to migmatites and granite dykes which relationships with respect to the main deformation phases were previously ascertained. The GPS coordinates of each sample can be found in Appendix Table B1.

6.3 UPb geochronology 6.3.1 Investigated samples Orthogneisses Two orthogneisses were selected in order to test whether they are aliated to the late Ediacaran meta-granites of the Velay Orthogneiss Formation (section 2.1) or represent early Variscan pre-kinematic granitoids as proposed by Dupraz and Didier (1988). In any case, they predate the main deformation event responsible for the foliation development. The Rocles pluton The current view of the Rocles granite being syntectonic with respect to the D 2v deformation (Fig. 6.2) partly relies on EPMA monazite ages (Be Mezeme et al., 2006; 2007). To ascertain the validity of those, sample ROC-16-01 was collected at the hamlet of Le Travers. This specimen is a Grt-and Bt-bearing granite showing a magmatic foliation (Fig. 6.10g).

Migmatites

Several migmatites developed at the expense of meta-igneous rocks were selected to constrain the age of partial melting in the Masméjean dome and the adjacent Tanargue area (Fig. 6.5). Samples CHA-15-47 and CHA-15-48 were taken from the disused quarry at the western exit of Saint-Laurent-les-Bains and respectively correspond to a bulk metatexite and an in-source leucosome embedded within it. Specimen CHA-15-43 is an in-source leucosome within at-lying metatexites from the dome core. It was sampled on the cli overhanging the railway at the Masméjean village. In-source leucosome CHA-15-63 was collected at the place known as Charbonneire in the northern part of the dome. Specimens CHA-15-17, CHA-15-65M and CHA-15-65L were all sampled right below the Puylaurent dam and respectively correspond to a bulk metatexite, a melanosome and in-source leucosome.

Analytical techniques

Zircon grains were separated from the powdered rock samples at Saint-Etienne University using conventional techniques described in section Les Orts granite sill sheared at the brittleductile transition Zircon grains from this sample range in size from 100 to 300 µm and show aspect ratios between 2 and 6. They are generally euhedral even though some crystals are broken. Very few zircon cores have been observed (Fig.

Post-tectonic granite dykes

Both dykes yielded very diverse zircon crystals with a range of shapes (aspect ratios between 1.1 and 3), sizes (60300 µm) and corerim relationships (large cores surrounded by thin CL-dark rims, core-free grains, cores surrounded by multiple growth zones). Not a single concordant Variscan date was obtained and all analysed grains are thus interpreted as being source-inherited or xenocrysts incorporated during magma ascent. Montel et al. (1992). Yet, as those dates are discordant they will not be further interpreted. The date of 291.8 ± 4.7 Ma obtained on the Saint-Laurent-les-Bains migmatite is dicult to interpret. It would most probably represent the age of an hydrothermal event, possibly related to the formation of the uorite lodes and veins recognized nearby Saint-Laurent-les-Bains [START_REF] Elmi | Notice explicative, Carte géol[END_REF][START_REF] Weisbrod | Carte géol[END_REF] showing very intricate contacts between the granite and its host paragneiss (Fig. 6.10a), inconsistent with the granitic magma intruding an already cooled-down basement (see the UPb apatite cooling ages mentioned above). Therefore, the discordant date of 309

± 10 Ma is retained as the age of magma crystallization while that of 359 ± 11 Ma, highly discordant, may be related to an early metamorphic event.

Petrogenetic constraints on syn-doming crustal melting

The observation of in-source leucosomes and granite veins within the Masméjean migmatites attests to melt mobility and associated mass and heat transfer during doming. This section addresses the modes of melt production in the Masméjean dome and notably the linkage between migmatites and granites. For this purpose, a total of 25 new major and trace element whole-rock compositions were obtained for samples from the Masméjean dome and its close surroundings: 13 granites, 4 orthogneisses and 8 migmatites (3 bulk metatexites and 5 in source-leucosomes). Additional measurements on regional orthogneisses (N=20) from section 2.1 were added to the dataset (all analyses available in Appendix Table B1).

PT conditions of anatexis in the migmatites

First-order thermodynamic modelling was performed to investigate the PT conditions of melting in the dome core. Field observations (Fig. 6.13) and UPb zircon data (see previous section) indicate that augen gneisses from the Velay Orthogneiss Formation arguably constitute the protolith of the migmatites. Accordingly, a representative augen gneiss composition was chosen out of our database (SC-14-33) and pseudosections were calculated by Gibbs energy minimisation using PerpleX [START_REF] Connolly | Computation of phase equilibria by linear programming: A tool for geodynamic modeling and its application to subduction zone decarbonation[END_REF] The range of PT conditions investigated is 0.20.8 GPa for 600850 • C. Solutions models selected are: Bio(TCC) for biotite [START_REF] Taj£manová | A thermodynamic model for titanium and ferric iron solution in biotite[END_REF], Pl(h) and San for plagioclase and K-feldspar [START_REF] Newton | Thermodynamics of the garnet-plagioclase-Al2SiO5quartz geobarometer[END_REF], Mica(CHA1) for white mica [START_REF] Auzanneau | Titanium in phengite: a geobarometer for high temperature eclogites[END_REF][START_REF] Coggon | Mixing properties of phengitic micas and revised garnetphengite thermobarometers[END_REF], melt(HP) for anatectic melt [START_REF] White | Calculation of partial melting equilibria in the system Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O (NCKFMASH)[END_REF], hCrd for cordierite and Opx(HP) for orthopyroxene [START_REF] Powell | Relating formulations of the thermodynamics of mineral solid solutions: Activity modeling of pyroxenes, amphiboles, and micas[END_REF], Gt(WPH) and Ilm(WPH) for garnet and ilmenite [START_REF] White | The eect of TiO2 and Fe2O3 on metapelitic assemblages at greenschist and amphibolite facies conditions: mineral equilibria calculations in the system K2OFeOMgOAl2O3SiO2H2OTiO2Fe2O3[END_REF].

SC-14-33 composition was recast to anhydrous and the H 2 O concentration subse- quently adjusted to obtain a fully hydrated subsolidus system (maximal water content without subsolidus H 2 O oversaturation) at 0.5 GPa Following petrographic observations (see section 6.2.2), the paragenesis inferred at peak metamorphic conditions for the migmatites is: melt+Qz+Kfs+Pg+Bt±Sil±Ms ±Ilm±Ru+Ap+Zrc. The stability eld of this mineral assemblage is bounded at low temperature by the solidus and at high temperature (and/or low pressure) by biotitebreakdown and associated appearance of garnet and/or cordierite (Fig. 6.27). As none of these minerals have been observed, we conclude that partial melting in the Masméjean dome took place at 0.75 < P < 0.3 GPa and 650 < T < 730 • C, consistent with the estimates of [START_REF] Dallain | Textural evolution in the transition from subsolidus annealing to melting process, Velay Dome, French Massif Central[END_REF] and Montel et al. (1992).

Melt production would have occurred through water-present and muscovite dehydration-melting, generating sillimanite and K-feldspar as by-products [START_REF] Clemens | Constraints on melting and magma production in the crust[END_REF][START_REF] Dallain | Textural evolution in the transition from subsolidus annealing to melting process, Velay Dome, French Massif Central[END_REF]Patiño Douce and Harris, 1998;[START_REF] Thompson | Dehydration melting of pelitic rocks and the generation of H2O-undersaturated granitic liquids[END_REF]. Importantly, low melt productivity is expected at these PT conditions with as little as 24 wt.% melt being produced.

Granite petrogenesis

Geochemistry and typology

Granites from the Masméjean dome are peraluminous (Fig. 6.28a) and dene a trend between the felsic and highly peraluminous elds in the BA diagram [START_REF] Debon | A chemical-mineralogical classication of common plutonic rocks and associations[END_REF][START_REF] Villaseca | A re-examination of the typology of peraluminous granite types in intracontinental orogenic belts[END_REF], indicative of an anity to Stype granites [START_REF] Clemens | S-type granitic magmaspetrogenetic issues, models and evidence[END_REF][START_REF] Chappell | Two contrasting granite types[END_REF][START_REF] Villaseca | A re-examination of the typology of peraluminous granite types in intracontinental orogenic belts[END_REF]. If they share similar major element compositions with meta-granites from the Velay Orthogneiss Formation, they distinctively show higher Nb/Y ratios (Fig. 6.28b). Metatexites mostly overlap in composition with unmolten orthogneisses apart for an enrichment in Nb, possibly related to biotite accumulation (Fig. 6.28d). In-source leucosomes are felsic peraluminous, Nb depleted and typically lack any Eu anomaly (Eu/Eu* close to 1).

Inherited zircon evidence for an orthogneiss source

Granites from the Masméjean dome and more generally from the southern border of the Velay dome contain abundant inherited/xenocrystic zircon grains (see Couzinié et al., 2014;Laurent et al., 2017, and this study). The distribution of 206 Pb/ 238 U dates mea- sured on such grains is unimodal and features a marked peak at c. 545 Ma with few older (mostly EdiacaranCryogenian) and younger (Ordovician to Carboniferous) dates (Fig. 6.29).

Assuming that most xenocrysts were incorporated in the magma at source level, the perfect match between the granite inherited date distribution and that of the Velay Orthogneiss Formation indicates that the latter constitutes the source of most granite magmas emplaced in the Masméjean dome and its surroundings. Subordinate involvement of regional metasediments is supported by the presence of 560680 Ma-old xenocrysts, even though c. 50% of those grains actually correspond to cores wrapped around by c. 545

Ma-old rims, suggesting they rather belonged to the source of the VOF meta-granites (see section 2.1). The origin of the three Ordovician zircon dates remains unknown as no rock of that age has been described in this region. Finally, DevonianCarboniferous grains would have recorded early Variscan metamorphic/magmatic events aecting the local basement (Faure et al., 2009) before being incorporated in the magma at the origin of the Masméjean granites.

Low orthogneiss fertility: the X H2O issue

The inherited zircon age pattern supports an orthogneiss source for regional granites.

As those are spatially associated to the Masméjean and southern Velay migmatites, the genetic linkage between anatexites and granites must be addressed. Thermodynamic modelling shows that at peak metamorphic conditions, the melt productivity of augen gneisses at fully hydrated conditions is low (maximum of 4% wt.%). Such value is notably lower than the liquid percolation threshold (LPT, 8 vol.% melt, [START_REF] Vigneresse | Rheological transitions during partial melting and crystallization with application to felsic magma segregation and transfer[END_REF] above which melt can escape its source and collect. Yet, eld observations support the existence of former melt-enriched (in-source leucosome) and melt-depleted (biotite-rich melanosome) domains which clearly attest to ecient melt transfer and mobility in the Masméjean migmatites (Fig. 6.13a,b), potentially up to form Masméjean granite bodies. Such inconsistency between eld observations and the model predictions may have two origins. First, melt coalescence is a deformation-assisted process [START_REF] Macaudière | Le stade initial de fusion dans le développement des dômes anatectiques : le dôme du Velay (Massif Central français)[END_REF][START_REF] Mclellan | Migmatite structures in the Central Gneiss Complex, Boca de Quadra, Alaska[END_REF][START_REF] Sawyer | Atlas of Migmatites[END_REF] meaning that pure/simple shearing may be sucient to expel liquids out of their solid matrix, even at (very) low melt fractions. An alternative view would be to consider that the "fully hydrated system" assumption is wrong and that anatexis was aqueous uid-assisted (see Weinberg and Hasalová, 2015 and refer- ences therein). Elevated X H2O in the bulk composition does not substantially aect the stability eld of the main mineral assemblages but results in a dramatic increase of the melt productivity (Fig. 6.30). This partly stems from the overall "eutectic" composition of the orthogneiss source, with quartz and feldspars being dissolved in the melt phase via the reaction Qz + Kfs + Pl + H 2 O = melt, only limited by water availability (Johannes and Holtz, 1996; Holtz and Johannes, 1991).

Increasing the H 2 O content of the source orthogneiss may proceed via inux of: (i) meteoric water, percolating down to the middle crust [START_REF] Wickham | Stable isotopic evidence for large-scale seawater inltration in a regional metamorphic terrane; the Trois Seigneurs Massif, Pyrenees, France[END_REF]; (ii) metamorphic water, originating from the dehydration of deeper lithologies [START_REF] Cartwright | Changes in stable isotope ratios of metapeUtes and marbles during regional metamorphism, Mount Lofty Ranges, South Australia: implications for crustal scale uid ow[END_REF][START_REF] Sawyer | Migmatites formed by water-uxed partial melting of a leucogranodiorite protolith: Microstructures in the residual rocks and source of the uid[END_REF], (iii) magmatic water conveyed by uprising, hydrous melts [START_REF] Weinberg | Water-uxed melting of the continental crust: A review[END_REF]. Evidence for case (i) are very scarce in the geological record (see review in [START_REF] Weinberg | Water-uxed melting of the continental crust: A review[END_REF]. In case (ii), release of aqueous uids in the deep crust is likely to immediately promote partial melting so that H 2 O would be transferred upsection dissolved in a melt phase [START_REF] Sawyer | Migmatites formed by water-uxed partial melting of a leucogranodiorite protolith: Microstructures in the residual rocks and source of the uid[END_REF] hence getting to case (iii).

Following [START_REF] Weinberg | Water-uxed melting of the continental crust: A review[END_REF], we envisage a situation where the intrusion of a water-rich magma creates a local water activity gradient in the middle crust. This promotes H 2 O transfer from the melt to its country-rocks which would in turn initiate or enhance anatexis. Such model would adequately explain the apparent elevated melt volumes in migmatites, higher than predicted for subsolidus full hydration, and the spatial and temporal relationships between anatexis and granitic magmatism (see Fig. 6.13e,f ).

Given the scarcity of mac igneous rocks in the Masméjean dome, the intruding hydrous magmas were most likely of granite composition. Their inferred elevated H 2 O contents suggests that they derive from the fractionation of a water-rich parental magma akin to vaugnerites (Parat et al., 2009). If our model is correct, granites from the Masméjean dome would intrinsically be of mixed origin: a fraction of their mass corresponds to collected, local anatectic liquids while the rest originates from fractionated mantlederived magmas.

In order to test this hypothesis, we performed forward modelling to estimate the major and trace element compositions of anatectic liquids generated from orthogneiss melting for a range of PTX H2O conditions and compared them to the natural granite compositions.

Figure 6.30: TX H2O pseudosection calculated using a representative augen gneiss composition. White lines are melt isopleths (with numbers indicating melt wt.%). For sake of clarity, isopleths were not drawn in the eld Bt+Pl+Kfs+Ms+Qz+melt+H 2 O. Mineral abbreviations after [START_REF] Whitney | Abbreviations for names of rock-forming minerals[END_REF].

Forward modelling of granite genesis

Phase proportions and melt compositions were calculated along three P-T paths consisting in isobaric heating from 680 to 800 • C at 0.4, 0.5 and 0.6 GPa, using the same representative augen gneiss composition as above (Table 6.2). Calculations were performed in closed-system, i.e. with no melt extraction (the melt is always in equilibrium with the solid residue). Three initial water contents were considered for the bulk starting composition: 0.53, 1.6 and 2.6 wt.% H 2 O. Melt Ba, Sr and Nb contents were calculated at each step along the PT path using: (i) the phase proportions retrieved from each step along the Tt path; and (ii) a set of partition coecients for felsic systems compiled by [START_REF] Laurent | Les changements géodynamiques à la transition Archéen-Protérozoïque : étude des granitoïdes de la marge Nord du craton du Kaapvaal (Afrique du Sud)[END_REF].

Results are depicted Fig. 6.28. First, four in-source leucosomes out of ve show dierent chemical compositions than predicted by the model for anatectic melts. Their low Nb contents and elevated Eu/Eu* collectively suggest that they correspond to plagioclaserich and biotite-poor cumulates. Five granite samples with low Ba + Sr would adequately correspond to pristine anatectic melts generated at T <760 • C for a large range of X H2O contents (from 0.53 to 2.6 wt.%) and T >760 • C but elevated X H2O (1.6 to 2.6 wt.%).

Importantly, melting at high temperature under fully hydrated conditions (X H2O = 0.53 wt.%) fails to reproduce natural composition has it generates melts with high Nb concentrations (Fig. 6.28d). In addition, the composition of 6 granites can be reasonably modelled as a mixture between local anatectic melts and 2080% KCG magmas (Fig.

6.28c,d).

Two samples are richer in Ba+Sr, possibly related to local K-feldspar accumulation.

To conclude, geochemical modelling supports a mixed origin for the Masméjean granites with a fraction corresponding to local pristine anatectic melts formed at T <730 760

• C and the remaining being akin to KCG magmas. This way, elevated melt contents in metatexites most probably stem from the addition of external water, supplied by intruding mantle-derived KCG magmas.

6.4.3 Dierential response to water ingress: role of inherited structures in controlling doming

The previous section illustrates how water diusion from hydrous mantle-derived magmas would trigger substantial anatexis at moderate temperatures. In the case of the Masméjean dome, the dramatic eects of water ingress inherently stems from the unlimited availability of the cardinal minerals Qz+Pg+Kfs involved in the "eutectic" melting reaction (Holtz and Johannes, 1991;Johannes and Holtz, 1996). In other words, melting would have been markedly enhanced because of the granitic nature of the VOF protolith.

The control exerted by the source composition and mineralogy on this phenomenon can be apprehended by comparing the melt productivities of ortho and paragneisses at 0.5

GPa when the water content increases due to interaction with KCG magmas.

Figure 6.31 shows that regional metagreywackes (reference material CEV, see Vielzeuf andMontel, 1994 andMontel andVielzeuf, 1997) produce very limited amounts of melts below 720

• C and are always less fertile than the VOF orthogneiss (twice as less on av- erage) at elevated X H2O . This feature simply reects the absence of Kfs at subsolidus conditions (Montel and Vielzeuf, 1997;Vielzeuf and Montel, 1994), hampering substantial melt production by the "eutectic" melting reaction. In metagreywackes, Kfs is the limiting reactant and not H 2 O as in the orthogneiss.

Importantly, these rst-order calculations suggest that enhanced anatexis by water ingress is restricted to migmatites developed at the expense of meta-igneous lithologies, such as the VOF. This would adequately explain why the Masméjean dome is cored by orthogneisses. As anatexis and dome formation are intimately linked, both from a spatial and temporal point of view [START_REF] Rey | The role of partial melting and extensional strain rates in the development of metamorphic core complexes[END_REF][START_REF] Tirel | Thermomechanical modeling of extensional gneiss domes[END_REF]Whitney et al., 2004b), doming would only proceed in orthogneiss-dominated terrains.

Figure 6.31: Comparison of respective melt productivities (in wt.%) for the Velay Orthogneiss Formation (augen gneiss sample SC-14-33) and a regional representative metagreywacke (CEV, Vielzeuf and Montel, 1994) with increasing water contents at a pressure of 0.5 GPa. Melt isopleths for the greywacke calculated using the same procedure as section 6.4.1.

Zircon behaviour during orthogneiss melting

A striking feature of the UPb zircon dataset is the comprehensive lack of Variscan grain in the migmatites. The same remark holds true for several granite bodies in and around the dome. This section addresses the origin of such scant Variscan zircon record.

Maximum Zr uptake in the melt fraction

In this section, we will consider that new zircon growth during anatexis exclusively results from the dissolution of pre-existing protolith zircon grains and re-precipitation of new grains (or overgrowths) from the melt phase [START_REF] Watson | Dissolution, growth and survival of zircons during crustal fusion: kinetic principals, geological models and implications for isotopic inheritance[END_REF]. Zircon neoformation by Ostwald ripening [START_REF] Nemchin | Ostwald ripening as a possible mechanism for zircon overgrowth formation during anatexis: Theoretical constraints, a numerical model, and its application to pelitic migmatites of the Tickalara Metamorphics, northwestern Australia[END_REF] was not investigated. Experimental studies have determined the maximal amount of Zr that can be accommodated in a melt until it reaches zircon saturation, which depends on the temperature and melt chemistry (Boehnke et al., 2013;Watson and Harrison, 1983). Following this, it is possible to predict the maximal Zr content of felsic melts generated from the VOF orthogneisses in a range of PT H2O conditions. Figures 6.32 and 6.33 depict the maximal Zr content of melts produced from the same representative augen gneiss composition used in the modelling section 6.4. Such value strongly depends on the temperature of melting but little on the bulk water content of the protolith.

Assuming that all Zr in the orthogneiss is hosted in zircon, it becomes possible to calculate the proportion of the orthogneiss zircon budget that has to be dissolved in order to saturate the melt phase. The results are reported Fig. 6.34 and 6.35. Importantly, low and high bulk H 2 O systems show contrasted behaviours. At low water content (Fig. 6.34), saturation of melt fractions >10 wt.% requires substantial zircon dissolution, up to 50 wt.% of the source zircon budget for only 20 wt.% melt in the migmatite. In contrast, at high H 2 O content, saturation of elevated melt fractions can be reached through limited zircon dissolution. For instance, incorporation of 10 wt.% of the orthogneiss zircon pool can suce to saturate a 24 wt.% melt fraction at 690 • C.

Such dierences arise from the fact that attaining substantial melt fractions at low H 2 O content requires elevated temperature (Fig. 6.32) and is correlated to an increase in the melt M parameter (Boehnke et al., 2013;[START_REF] Miller | Hot and cold granites? Implications of zircon saturation temperatures and preservation of inheritance[END_REF]. Both aspects result in higher maximal melt Zr content (Fig. 6.32) thus entailing extensive dissolution of the source budget. In contrast, there is little change in the M parameter value at elevated H 2 O content because melt chemistry is buered by the reaction Qz+Kfs+Pg+H 2 O=melt (Holtz and Johannes, 1991;Johannes and Holtz, 1996). The maximal melt Zr content remains low (<90 ppm) and the melt phase can be saturated via limited dissolution of the zircon pool in the source.

To conclude, these results suggest that the amount of new magmatic zircon in a migmatite is a rst-order estimate of the temperature of melting and the water content of the system. Figure 6.35: Calculated proportion (white lines, in wt.%) of the orthogneiss zircon budget to be dissolved in order to saturate the melt phase. The average Zr content of the protolith was set to 115 ppm for. Dotted lines and bold numbers are melt isopleths and melt contents in wt.%, respectively. Pressure is 0.5 GPa.

Additional complications

Calculations performed in the previous section considered an idealized and simplied case where the migmatite behaves as a closed-system, i.e. melt is retained within its source. Yet, melt loss events deplete or enrich the restite in Zr (depending on the melt Zr content vs. that of the protolith) which, in turn, aects further zircon dissolution in the residual melts (e.g. [START_REF] Kelsey | Thermobarometric modelling of zircon and monazite growth in melt-bearing systems: examples using model metapelitic and metapsammitic granulites[END_REF][START_REF] Yakymchuk | Behaviour of zircon and monazite during crustal melting[END_REF].

Another range of parameters not investigated in our model are the kinetics eects as we assumed permanent meltsolid equilibrium. Importantly, the dissolution of zircon grains is controlled by the diusion of Zr in the melt fraction [START_REF] Watson | Dissolution, growth and survival of zircons during crustal fusion: kinetic principals, geological models and implications for isotopic inheritance[END_REF]. Therefore, rapid withdrawal of anatectic melts out of the source may result in a disequilibrium between melt and the solid residual matrix (Harris et al., 2000;[START_REF] Sawyer | Disequilibrium melting and the rate of meltresiduum separation during migmatization of mac rocks from the Grenville Front, Quebec[END_REF][START_REF] Watt | Chemical characteristics of migmatites: Accessory phase distribution and evidence for fast melt segregation rates[END_REF], hampering substantial zircon dissolution before melt extraction. However, disequilibrium melting might not always be the rule (e.g. [START_REF] Rubatto | Zircon and monazite response to prograde metamorphism in the Reynolds range, central Australia[END_REF].

Finally, it was assumed that all zircon (and hence all Zr) from the protolith was part of the "reactive system", i.e. was not occluded in unreactive minerals during partial melting.

Yet, biotite hosts notable amounts of zircon grains in metamorphic rocks [START_REF] Clemens | S-type granitic magmaspetrogenetic issues, models and evidence[END_REF] meaning that, during melting at temperatures lower than that required for extensive biotite breakdown, part of the protolith zircon budget cannot physically interact with the melt and is in essence out of equilibrium [START_REF] Bea | Behavior of accessory phases and redistribution of Zr, REE, Y, Th, and U during metamorphism and partial melting of metapelites in the lower crust: An example from the Kinzigite Formation of Ivrea-Verbano, NW Italy[END_REF][START_REF] Skrzypek | The origin of zircon and the signicance of UPb ages in high-grade metamorphic rocks: a case study from the Variscan orogenic root (Vosges Mountains, NE France)[END_REF].

Application to the Masméjean migmatites and granites

At melting conditions relevant for the Masméjean case study, i.e. T < 730

• C, saturation of the migmatite melt fraction would be achieved through limited zircon dissolution corresponding to c. 10 wt.% of the orthogneiss budget for a reasonable maximal melt content of 20 wt.%. Therefore, if the melt fraction crystallized in situ, one could expect c. 10 wt.% of the zircon grains (or grain domains) to have recorded the melting event.

Such value is clearly a maximum estimate as it presumes a closed-system behaviour with full equilibration between melt and residue.

Following this, the lack of Variscan zircon in the Masméjean metatexites would result from the conjunction of: (i) low zircon solubility in the melt phase at the inferred P TX H2O conditions of melting (Fig. 6.32 and 6.33), entailing that a maximum of only 10 wt.% of the grains would be magmatic and record anatexis; (ii) selective retention of zircon grains in biotite, as melting occurred at T < 780

• C (onset of biotite dehydration melting, Vielzeuf and Montel, 1994); (iii) kinetics eects, with the potentially short-lived evolution at elevated melt fractions preventing meltresidue equilibration; and, (iv) melt loss events, further hindering the probability to retrieve newly grown Variscan grains, critical for melanosome CHA-15-65M.

In the case of granitic magmas, the scarcity or even absence of Variscan zircon in some specimen suggests that the Zr content of the melt phase was insucient to precipitate substantial amounts of new zircon. In this frame, it is most likely that the melts left their sources in a Zr-undersaturated state and did not further dissolve inherited grains or xenocrysts at emplacement levels, possibly because of fast cooling rates [START_REF] Bindeman | Zircon survival, rebirth and recycling during crustal melting, magma crystallization, and mixing based on numerical modelling[END_REF][START_REF] Watson | Dissolution, growth and survival of zircons during crustal fusion: kinetic principals, geological models and implications for isotopic inheritance[END_REF].

Melt Zr-undersaturation would also adequately explain the absence of magmatic grains in the in-source leucosomes. Indeed, as geochemical data support a cumulative origin, crystallization of major minerals from the melt phase would have reduced the melt volume and thus entailed precipitation of new zircon if the melt had been saturated.

Consequently, a combination of several factors probably accounts for the scant zircon record of Variscan crustal melting. Importantly, the apparent Zr-undersaturation of crust-derived melts suggests that meltresidue equilibrium during anatexis was not achieved.

6.6 Formation of the Masméjean dome 6.6.1 Pre-to early-doming tectonic regime Metamorphic rocks from the AndCrdBt and GrtChl zones record a regional pervasive top-to-the NE shearing event (D 2v ) that is well documented in the southwestern ank of the Masméjean dome. New geochronological constraints on the Rocles syntectonic granite (Fig. 6.26), in conjunction with literature data (Be Mezeme et al., 2006;2007;Bouilhol et al., 2006), indicate that top-to-the NE shearing probably lasted between 325315 Ma. The end of this tectonic episode is bracketed by intrusion of the c. 315-310

Ma-old Margeride granite which occurred under NWSE extension [START_REF] Talbot | Pull-apart emplacement of the Margeride granitic complex (French Massif Central). Implications for the late evolution of the Variscan orogen[END_REF].

At the regional scale, the NS expansion of the main Velay granite would have caused doming and tilting of the originally at-lying P 3 structures including the early Rocles granite (Be [START_REF] Be Mezeme | Structural, AMS and geochronological study of a laccolith emplaced during Late Variscan orogenic extension: the Rocles pluton (SE French Massif Central)[END_REF][START_REF] Burg | Structures and way-up criteria in migmatites, with application to the Velay dome (French massif Central)[END_REF]Lagarde and Dallain, 1994;[START_REF] Laumonier | Relations entre tectoniques superposées, migmatisations et mise en place des granites sur l'exemple de la bordure sud du dôme du Velay (région de Laviolle, Ardèche, France)[END_REF]Ledru et al., 2001;[START_REF] Marignac | Evolution tectonométamorphique d'un segment de l'orogène hercynien : les Cévennes médianes, Massif Central français[END_REF]. Restoring the predoming geometry, top-to-the NE shearing would have aected a gently N-dipping foliation (Fig. 6.36a). Such situation markedly resembles that of the Pilat Shear Zone, described at the northern edge of the Velay Complex and presumably controlling its exhumation (Malavielle et al., 1990). Consequently, as originally suggested by Bouilhol et al. (2006), Consequently, we argue that left-lateral displacement dominantly took place under ductile conditions and initiated before c. 305 Ma, the intrusion age of the syntectonic Villefort granites (Fig. 6.36c). It is most likely that the Pont-de-Montvert and Borne plutons corresponded to dierent batholiths emplaced in a EW to NESE extensional regime [START_REF] Faure | Le pluton du Pont-de-Montvert : un granite syntectonique extravasé vers l'Est pendant le désépaississement crustal varisque du Massif Central français[END_REF][START_REF] Talbot | AMS study of the Pont-de-Montvert-Borne porphyritic granite pluton (French Massif Central) and its tectonic implications[END_REF]2004) and which eastern and western terminations, respectively, were truncated by ductile and subsequent brittle [START_REF] Deroin | Fracturation tardi-hercynienne et détritisme associé : chronologie des évènements dans les massifs granitiques cévenols décrochés par la faille de Villefort (Mont Lozère et Borne, Massif Central, France)[END_REF]) deformation along the Villefort Shear Zone (Fig. 6.36c,d). In addition, apparent truncations may have been exacerbated by the subtractive eects of late normal faulting.

Figure 6.36: Schematic maps illustrating the regional evolution of the study area between 325 and 275 Ma, with a particular emphasis on the formation of the Masméjean dome. To be related to Fig. 6.2.

Timing of initiation

The onset of the Villefort Shear Zone activity remains unclear. According to [START_REF] Prost | Evidence for mid-Permian compressive tectonics in Western Europe supported by a comparison with the Alleghanian geodynamic evolution[END_REF] and [START_REF] Lagarde | Contexte tetonique de la fusion crustale postcollision dans la chaîne hercynienne : l'exemple du complexe anatectique du Velay (Massif central français)[END_REF], the VSZ extends further North and bounds the western part of the Velay Complex. In this area, Dupraz and Didier (1988) documented a set of syntectonic granites (the so-called "Chaise-Dieu" granites) emplaced during wrenching, presumably related to the VSZ activity. Laurent et al. (2017) obtained zircon and monazite UPb intrusion ages ranging between 318.3 ± 4.4 Ma and 314.5 ± 3.9 Ma (taking into account systematic errors). Consequently, the Villefort Shear Zone may have initiated as early as 320 Ma in the northern Velay and possibly propagated to the South at 315310 Ma (Fig. 6.36b,c).

Isolating the Masméjean and Tanargue domes

Owing to the geometry of its foliation pattern, the western part of the Masméjean dome resembles the termination of a conical EW trending antiform, akin to the Tanargue dome. Such geometry suggests an original connection between the two domes, besides supported by their petrological continuity. This way, both were most probably part of a single EW trending antiformal structure in the core of which partially molten crust started being extruded at 315310 Ma (Fig. 6.36b, Bouilhol et al., 2006). Left-lateral movements along the Villefort Shear Zone would have oset the western termination from the main part of the antiform (Fig. 6.36c) which evolved as the Masméjean and Tanargue domes, respectively.

Vertical strain partitioning in the crust?

In the time period 310300 Ma, the middle crust was aected by strike-slip ductile shearing along the Villefort Shear Zone. In contrast, the internal structure of granitic plutons (Pont-de-Montvert and Borne, Fig. 6.36c) coevally emplaced at higher crustal levels rather recorded an EW extensional context [START_REF] Faure | Le pluton du Pont-de-Montvert : un granite syntectonique extravasé vers l'Est pendant le désépaississement crustal varisque du Massif Central français[END_REF]Faure, 1995;[START_REF] Faure | Tectonic evolution of the Cévennes para-autochtonous domain of the Hercynian French Massif Central and its bearing on ore deposits formation[END_REF][START_REF] Talbot | AMS study of the Pont-de-Montvert-Borne porphyritic granite pluton (French Massif Central) and its tectonic implications[END_REF]2004). NS wrenching is dicult to reconcile with synchronous EW extension and points to a vertical strain partitioning within the crust section.

At mid-crustal level, the Villefort Shear Zone possibly acted as a transfer structure accommodating dierential movements between the Velay Complex to the East, and the Margeride domain to the West. Such displacements would have taken place due to contrasted rheological behaviours of both crust segments. Experimental studies have demonstrated that the strength of a solid rock decreases by at least two orders of magnitude as soon as a small volume of melt is present in the matrix [START_REF] Paquet | Eect of partial melting on rock deformation: experimental and natural evidences on rocks of granitic compositions[END_REF][START_REF] Rosenberg | Experimental deformation of partially melted granite revisited: implications for the continental crust[END_REF][START_REF] Rushmer | Melt segregation in the lower crust: how have experiments helped us?[END_REF]. As a matter of fact, by 310300 Ma, the Margeride batholith was likely fully crystallized and its extraction left behind a sti, dry residue. In contrast, anatexis was still ongoing in the Velay Complex by that time.

Consequently, the Villefort Shear Zone possibly delineated the boundary between meltrich and melt-depleted mid-crustal domains by the late Carboniferous. In this frame, the shear zone would have originally remained conned in the middle crust and lately propagated to the upper crust (Fig. 6.36d), probably at Permian times [START_REF] Arthaud | Les décrochements tardi-hercyniens du Sud-Ouest de l'Europe. Géométrie et essai de reconstitution des conditions de la déformation[END_REF][START_REF] Prost | Evidence for mid-Permian compressive tectonics in Western Europe supported by a comparison with the Alleghanian geodynamic evolution[END_REF][START_REF] Talbot | Emplacement in an extensional setting of the Mont LozèreBorne granitic complex (SE France) inferred from comprehensive AMS, structural and gravity studies[END_REF].

Post-exhumation evolution

Timing of the Masméjean dome cooling is constrained by the respective ages of migmatite crystallization and ne-grained porphyritic granite intrusion, both occurring at c. 300 Ma (see section 6.3). The Permian evolution is marked by localized uid circulations pinpointed by the recrystallization/resetting of monazite in the dome core and along the Villefort Shear Zone. Last increments of brittle deformation along the latter possibly acted as a drain for a range of crustal uids. Their origin is not ascertained but they may have been released by the crystallization of migmatites or deep magmas. Sedimentation in the PradesJaujac and Alès basins started in the early Permian [START_REF] Bruguier | Application of in situ zircon geochronology and accessory phase chemistry to constraining basin development during post-collisional extension: a case study from the French Massif Central[END_REF] and The picture drawn in the Masméjean area contrasts with that observed east of the Villefort Shear Zone, in the Tanargue dome. There, the Sil-Bt zone of the mantle is pervasively aected by top-to-the S shearing related to migmatites vertical extrusion (Bouilhol et al., 2006). Such dierent mechanical behaviour of the coremantle interface compared to the Masméjean dome possibly stems from higher strain rates. Indeed, the steep migmatite foliation in the Tanargue area would testify for substantial vertical transport, larger than inferred for the Masméjean dome.

6.7.2 Respective roles of the regional strain eld and the buoyancydriven ow during doming D 2v NE-SW extension, marked by the activation of top-to-the NE shear zones, pre-dated the formation of the Masméjean and Velay domes. This 325315 Ma crustal thinning event was accompanied by early anatexis. A marked dynamic change took place at c.

315 Ma with the onset of partially molten crust vertical extrusion in the core of EW trending antiforms. At that very same time, granite bodies emplaced in the upper crust record a general D 3 NWSE to EW extension, i.e. perpendicular to the migmatites ow direction. It comes from this that the regional D 2v event likely triggered the exhumation of the partially molten crust, but as soon as this process had been launched, the ow of the middle crust would have been mostly controlled by buoyancy and overall little aected by the upper crustal strain eld. This is well evidenced in the Masméjean dome where the migmatite core is mechanically decoupled with its overlying unmolten dome mantle.

The only external control on the Masméjean dome formation would correspond to the wrench corridor along its eastern ank, clearly acting as a boundary with the adjacent crustal domain, channelling dome exhumation and collecting anatectic liquids. Yet, the signicance of this Villefort Shear Zone remains unclear as its late Carboniferous activity does not easily t with a general EW extensional context. This shear zone may have nucleated as a transfer fault, accommodating contrasted rheological behaviours on its western and eastern side. Indeed, to the West, intrusion of the Margeride granite, the largest batholith in France (Chantraine et al., 1996), likely drained large volumes of melt out of the middle crust, leaving behind a sti residue. On the other hand, to the East, melt remained conned in the middle crust and ultimately led to doming.

In any case, the Masméjean dome and the southern part of the Velay Complex illustrate the dramatic rheological and tectonic eects of continental crust partial melting. Petrological constraints gained on the Masméjean dome formation hint a twofold control on the doming process (Fig. 6.37). The spatial distribution of hydrous magmas intrusions (originating from a metasomatized mantle source) delineates crustal zones with increased water contents. Such H 2 O ingress promotes catastrophic melting in areas fea- turing substantial volumes of orthogneisses while leaving paragneiss-dominated domains unaected. As partial melting and dome formation are intimately linked (Whitney et al., 2004a), the locus of doming during post-collisional evolution would depend on: (i) the pathways followed by mantle-derived magmas en route to the surface; and (ii) the preorogenic magmatic history of the crust segment, i.e. inherited structures and lithological heterogeneities.

This model is consistent with the geological record of doming worlwide. Indeed, gneiss domes are generally cored by anatectic meta-igneous rocks. For instance, the Dassu-Askole or Gurla Mandhata domes of the Himalayan Karakorum Metamorphic complex all feature anatectic orthogneiss cores and evidence for coeval mantle-derived magmatism [START_REF] Murphy | Structural evolution of the Gurla Mandhata detachment system, southwest Tibet: Implications for the eastward extent of the Karakoram fault system[END_REF][START_REF] Rolland | Tectono-metamorphic evolution of the Karakorum Metamorphic complex (Dassu-Askole area, NE Pakistan): exhumation of mid-crustal HT-MP gneisses in a convergent context[END_REF]. Other iconic cases include the Shuswap Metamorphic Complex in the Canadian Cordillera [START_REF] Norlander | Partial melting and decompression of the Thor-Odin dome, Shuswap metamorphic core complex[END_REF][START_REF] Parkinson | Age and isotopic character of Early Proterozoic basement gneisses in the southern Monashee Complex, southeastern British Columbia[END_REF], the KesebirKardamos dome in Rhodope [START_REF] Bonev | MesozoicTertiary structural evolution of an extensional gneiss domethe KesebirKardamos dome, eastern Rhodope (BulgariaGreece)[END_REF] or the Aston BossostHospitalet domes in the Variscan Pyrénées (Denèle et al., 2014) to cite only a few.

Part III

General discussion

Chapter 7

The zircon UPbHf(O) record of crust formation and reworking in the French Massif Central rst-order all lithological components recognized so far in the French Massif Central.

UPb date distribution

The distribution of zircon UPb dates reects the temporal succession of geological events that resulted in the formation of zircon grains. The most common situation is the crystallization of an intermediate to acid magma (Hoskin et al., 2000). Therefore, the UPb date distribution dominantly reects the timing of magmatic episodes that aected a given crust segment.

Figure 7.3 shows that no matter the dataset considered (comprehensive set of data or only spots with available Hf isotope compositions) the same distribution is observed.

Most dates range between 0.7 and 0.3 Ga dening two peaks at 0.3 and 0.6 Ga. This indicates that the FMC experienced substantial magmatic activity in the Neoproterozoic and Paleozoic. That being said, it is not possible to establish whether these magmatic events built up the FMC crust or alternatively reworked pre-existing crustal lithologies.

As a matter of fact, Paleoproterozoic and Archean zircon populations suggest the presence of older crustal components in the French Massif Central.

Integral growth curves

Integration of the above-mentioned age distributions yields crustal growth curves, i.e.

the volume of the present-day crust that had already been extracted at a given time period. Such approach presumes incremental assembly of the crust and does not take into account the eects of crust destruction and recycling in the mantle.

Growth curves retrieved from zircon UPb data are very similar and indicate that 45 to 60% of the FMC crust formed between 0.8 and 0.5 Ga, that is, during the Cadomian orogeny. Signicant growth would have also taken place at Variscan times (25 to 45% of the crust being extracted between 0.4 to 0.2 Ga). Less than 5% of the crust would be Paleoproterozoic to Archean in age.

In contrast, T DM -based curves point to a slow, continuous formation of the FMC crust since c. Besides, zircon Hf data processed conventionally would suggest that the Variscan orogeny is a period of strict crust reworking (see Fig. 7.6). Such result is at odds with the intrusion of mantle-derived magmas at the post-collisional stage (section 5.3), testifying for new additions to the crust volume. In fact, 5 to 10% of the FMC crust did formed at Variscan times (Moyen et al., 2017a).

To conclude, zircon UPbHf data considered alone erroneously point to substantial Mesoproterozoic FMC crust formation and do not account for Variscan crust production.

The origin of these discrepancies can be addressed by examining the petrological context of the analysed grains.

Origin of the discrepancies

Misleading zircon UPbHf information simply result from a range of mixing processes, having taken place in a variety of environments.

Sedimentary mixing

Paleoproterozoic and Archean zircon grains (Fig. 7.3) are found as (i) detritus in Ediacaran (meta)sediments; and (ii) inherited crystals and xenocrysts in late Cadomian to

Variscan crust-derived granites, most probably sourced in the former. Consequently, it is ambiguous to assess the origin of such grains. Indeed, they may originate from distal sources (see section 2.2) and this way should not be regarded as repositories of the pre-Ediacaran history of the FMC crust segment.

In other words, the presence of pre-Neoproterozoic zircon grains in the FMC would originate from the mixing of a variety of detritus in the Ediacaran sedimentary basins and would not reect the existence of an in-situ Paleoproterozoic to Archean crust in the FMC.

Mesoproterozoic model ages as a result of magma mixing ε-unit, most likely stem from mixing between magmas sourced in (i) and (ii) and thus of contrasted isotope compositions [START_REF] Janou²ek | Magma-mixing in the genesis of Hercynian calc-alkaline granitoids: an integrated petrographic and geochemical study of the Sázava intrusion, Central Bohemian Pluton, Czech Republic[END_REF]Laumonier et al., 2014a;b;[START_REF] Wang | The aw in the crustal `zircon archive': Mixed Hf isotope signatures record progressive contamination of late-stage liquid in macultramac layered intrusions[END_REF].

This way, the Mesoproterozoic model ages displayed by detrital Neoproterozoic zircon do not reect reworking of a Mesoproterozoic crustal reservoir but are instead mixed ages. Again, the involvement of an old, non-radiogenic Hf reservoir in the mixing model does not require the existence of a Paleoproterozoic/Archean crust in the French Massif Central as the mixing could have occurred in an adjacent terrain and the zircon grains subsequently transported to the FMC Ediacaran basins.

Mesoproterozoic model ages as a result of source mixing

A somewhat similar reasoning can be followed for crust-derived peraluminous granites from both the late Cadomian Velay Orthogneiss Formation and the Variscan postcollisional MPG/CPG suites. As they reworked the Ediacaran sediments, their source material was intrinsically heterogeneous in terms of zircon Hf isotope signature. Yet, both display tighter ranges of 3 and 7 ε-unit, respectively (Moyen et al., 2017a;Chelle-Michou et al., 2017;[START_REF] Couzinié | Cadomian S-type granites as basement rocks of the Variscan belt (Massif Central, France): Implications for the crustal evolution of the north Gondwana margin[END_REF].

The small-scale petrological processes at the origin of the zircon ε Hf (t) homogenization have been detailed section 2.1 and encompass: (i) inherited zircon dissolution during melting and ascent due to Zr-undersaturated conditions, (ii) isotopic homogenization of the melt phase by advection and elemental/isotopic diusion, followed by (iii) early saturation upon emplacement, preventing further dissolution of inherited grains. Those would have proceeded during both Cadomian and Variscan reworking events. In this case, the Mesoproterozoic Hf model ages displayed by magmatic zircon grains result from an averaging of the Hf isotope composition of the source material and are mixed in essence.

The consequences of crust recycling

Zircon grains crystallized in Variscan post-collisional mac magmas (PCMM) and other granitoids from the KCG suite show subchondritic ε Hf (t) despite the magma matter is dominantly of mantle origin (section 5.3). The reason for it lies in the the incorporation of 1025% crustal crustal materials in the mantle source. Similar cases have been described

in arc magmatic suites [START_REF] Nebel | The eect of sediment recycling in subduction zones on the Hf isotope character of new arc crust, Banda arc, Indonesia[END_REF][START_REF] Roberts | Sedimentary recycling in arc magmas: geochemical and UPbHfO constraints on the Mesoproterozoic Suldal Arc, SW Norway[END_REF] further suggesting that the ε Hf (t) is not a reliable repository of the proportion of crust-vs. mantle-derived components in a given magma.

In hybrid crust/mantle sources, the Hf budget is dominated by the recycled crustal component and the resulting magmas inherit a mixed, non-radiogenic Hf isotope signa-ture (most of the Hf is provided by the crustal materials and the rest by the mantle).

This feature explains why there is no Hf record of crust production at Variscan times (see Fig. 7.6). Besides, Mesoproterozoic Hf model ages displayed by magmatic zircons are here again the result of a mixing process and meaningless from a crust evolution perspective (section 5.3).

Signicance of the linear ε Hf (t)time array

Inherited zircon grains in Variscan peraluminous granites (MPG/CPG) provide evidence for substantial reworking of the Velay Orthogneiss Formation (see sections 5.4 and 6.4).

This way, the ε Hf (t)time array would simply reect the remelting of the VOF crustal reservoir provided it had an average 176 Lu/ 177 Hf of 0.01 (further whole-rock isotopic measurements would clarify this point).

However, post-collisional mac magmas (PCMM) and other granitoids from the KCG suite also plot within ε Hf (t)time array even though these rocks originate from melting of the mantle. Consequently, them matching the ε Hf (t)time array does not reect inner crust reworking processes. Instead, it would result from: (i) the dominance of the crustal component over the Hf elemental budget in the hybrid mantle source; and (ii)

the bulk Hf isotope signature of the inferred recycled crustal component being close to that of Ediacaran metasediments (section 5.3). Consequently, the PCMM/KCG case reassesses that care must be taken when interpreting ε Hf (t)time array solely in terms of closed-system crust reworking (Laurent and Zeh, 2015;Payne et al., 2016).

Additional methodological issues

On top of the aws presented above, it must be stressed that a set of methodological issues create a range of biases in the zircon record, the importance of which must be kept in mind while reasoning on grains taken out of their petrological context.

A rst problem inherently lies in the origin of the data considered. Large compilations as those commonly used to investigate crust evolution gather the results of studies originally conducted with a specic design. For instance, in the French Massif Central, around a half of the compiled data (Fig. 7.1) originate from studies that questioned the petrogenesis of Variscan post-collisional magmas (Couzinié et al., 2016;Laurent et al., 2017;Moyen et al., 2017a). This way, the human operator specically targeted zircon rims, sometimes very narrow, with the aim to assess the timing of magma emplacement.

Therefore, databases containing signicant amounts of igneous zircon grains (in the sense that the analyses were performed with the aim to constrain the petrology of an igneous rock) are likely to be biased towards an over-representation of the most recent magmatic events.

When looking at detrital zircon data (from modern rivers or ancient sediments), the record of crust evolution is blurred by the inherently variable zircon fertility factor of each crustal lithology [START_REF] Moecher | Dierential zircon fertility of source terranes and natural bias in the detrital zircon record: Implications for sedimentary provenance analysis[END_REF]Dickinson, 2008). According to these authors, erosion of arc-related magmatic rocks will deliver 3.5 times less zircon grains than collisional igneous suites. It comes from this that the observed zircon proportions in the detrital record cannot be directly translated in terms of crust volumes. For instance the ratio between radiogenic vs. non-radiogenic grains has no potential to unravel the actual extent of new crust production vs. crust reworking at a given time period.

Finally, are only considered in the crust evolution models zircon grains yielding concordant UPb dates. Though, discordant grains do take part of the detrital zircon budget and originate as well from igneous precursors. Rejecting those entails that estimates are only retrieved from a partial set of data (Nemchin and Cawood, 2005) and bias the record towards an over-representation of mantle-derived rocks, more likely to yield concordant results than crust-derived collisional suites (sections 5.1 and 5.3).

Alternative formulations and ways forward

In the following, are address some questions surrounding the evolution of the French Massif Central crust segment. The underlying approach is to emphasize the eciency of combining petrological information with zircon UPbHf data to unravel complex geological processes. Some of the discussed points are seen as future elds of investigation. As highlighted section 7.2.2, the Ediacaran detritus can be seen as a mixture between a young Neoproterozoic crust and old crustal materials (Paleoproterozoic and older).

Given the paleo-location of the FMC along the northern Gondwana margin, it is reasonable to consider that such materials consist in Eburnean (c. 2.0 Ga-old) and Neoarchean (c. 3.3 Ga-old) crusts (see [START_REF] Altumi | U Pb LAICPMS detrital zircon ages from the Cambrian of Al Qarqaf Arch, central-western Libya: Provenance of the West Gondwanan sand sea at the dawn of the early Palaeozoic[END_REF]Nance and Murphy, 1994 and references therein). In this frame, the proportions of each component in the source of the VOF (meta)granites may be retrieved from their chondritic signature. The latter demands that 6080 % of the Ediacaran detritus in the FMC corresponds to young Neoproterozoic crust (Fig. 7.7). Consequently, even though the genuine mantle-derived Cadomian igneous rocks have not been fully preserved, their erosion products substantially fed the late Ediacaran back-arc basins of the FMC and became de facto long-term additions to the continental crust volume.

The main limitation of this approach lies in the extent to which the source of the VOF is representative of the whole Ediacaran sedimentary sequence. By analogy with the shale geochemical model of Taylor and McLennan (1985), it has been proposed that peraluminous granites overall yield a bulk estimate of the continental crust composition [START_REF] Allègre | NdSr isotopic relationship in granitoid rocks and continental crust development: a chemical approach to orogenesis[END_REF], even though such view has been challenged in the early 90's (e.g. Turpin et al., 1990).

Lastly, several studies considered that a scatter in the zircon ε Hf (t) at a given time period, as observed in the EdiacaranCryogenian record of the FMC, reects the dominance of crust reworking processes [START_REF] Dhuime | Continental growth seen through the sedimentary record[END_REF]Kemp et al., 2006;[START_REF] Vervoort | Clarifying the zircon Hf isotope record of crustmantle evolution[END_REF]. In contrast, this study shows that such situation may aswell attest to voluminous new crust production. Based on this Cadomian case, I suggest that the concomitant presence in the record of juvenile and isotopically evolved zircon grains may be taken as evidence for new crust production in an active margin developed at the edge of an old cratonic crust segment (the Gondwana in the present case).

Crustmantle interactions during the Variscan collisional orogeny

Recent studies consider that the amount of continental crust being destroyed and recycled back in the mantle markedly increases during collisional events related to supercontinent assembly [START_REF] Roberts | Increased loss of continental crust during supercontinent amalgamation[END_REF]Stern and Scholl, 2010). One of the reason for it would be the subduction of continental crust units operating at the onset of collision (see Fig. 7.8a; [START_REF] Chopin | Ultrahigh-pressure metamorphism: tracing continental crust into the mantle[END_REF][START_REF] Guillot | Eclogitic metasediments from the Tso Morari area (Ladakh, Himalaya): evidence for continental subduction during India-Asia convergence[END_REF][START_REF] Roecker | Velocity structure of the Pamir-Indu Kush region: possible evidence of subducted crust[END_REF]. On the other hand, combined petrological and zircon UPbHfO data suggest that a total of 5 to 10% of the FMC crust would have been newly formed by Variscan post-collisional magmatism (section 5.3). As a result, collisional orogens constitute sites of crust recycling and crust formation (see Fig. 7.8a). This section examines some underlying consequences of both phenomena taking place nearly coevally (at the scale of a collisional orogenic event).

There and back, the continental crust journey in the mantle Post-collisional crust production is intimately associated with the remobilization of crustal lithologies that have been previously recycled, i.e. rendered back to the mantle (Campbell et al., 2014;Guo et al., 2014;[START_REF] Janou²ek | The causal link between HP-HT metamorphism ad ultrapotassic magmatism in collisional orogens: case study from the Moldanubian Zone of the Bohemian Massif[END_REF][START_REF] Zhao | Post-collisional granitoids from the Dabie orogen in China: Zircon UPb age, element and O isotope evidence for recycling of subducted continental crust[END_REF]2013). As post-collisional magmas systematically post-date by <50 Ma a subduction stage (section 5.3), they most probably re-incorporate to the crustal volume part of the matter that had been destroyed by continental subduction, shortly prior to collision (Fig. 7.8b).

A total of 15-38 wt.% of post-collisional magmas would actually correspond to atoms that were originally hosted in the continental crust (section 5.3). This way, the pathway followed by these atoms during continentcontinent collision denes a short-lived crust/mantle geochemical cycle: crustal elements lost in the waning stages of subduction are stored in the mantle for <50 Ma and part of them return to the continental crust encapsulated within post-collisional magmas (PCMM/KCG). Such cycle is somehow sim-Figure 7.8: Summary of the observations and outcomes related to the evolution of the continental crust during collisional orogenic episodes. Delamination of the lower continental crust is not considered.

ilar in a shorter space and time scale with the well-documented case of long-term storage of oceanic to continental crust in the deep mantle and their subsequent re-mobilization in OIB basalts with EM avour [START_REF] Chauvel | HIMUEM: The French Polynesian connection[END_REF][START_REF] Hofmann | Mantle geochemistry: the message from oceanic volcanism[END_REF][START_REF] Stracke | FOZO, HIMU, and the rest of the mantle zoo[END_REF][START_REF] Stracke | Earth's heterogeneous mantle: A product of convection-driven interaction between crust and mantle[END_REF][START_REF] Weaver | The origin of ocean island basalt end-member compositions: trace element and isotopic constraints[END_REF][START_REF] Willbold | Formation of enriched mantle components by recycling of upper and lower continental crust[END_REF].

It comes from this that since the onset of modern plate tectonics, presumably in the late Archean (Laurent et al., 2014), part of the continental crust volume would have been processed through this orogenic crust/mantle cycle and resided for a short time period in the mantle.

Consequences on the continental crust chemical composition

The materials recycled in the mantle during the pre-to early-collisional stage should have, on average, a composition akin to the Bulk Continental Crust because the whole crust section is presumably dragged down by subduction dynamics. On the other hand, new additions to the crust volume are mediated by post-collisional mac magmas of peculiar chemical composition (section 5.3). Here is compared the incoming and outcoming chemical uxes within the orogenic mantle in an attempt to qualitatively evaluate the crust/mantle mass transfers and address the impact of orogenies on the long-term chem-ical evolution of the continental crust. The extent and consequences of orogenic lower crust delamination [START_REF] Arndt | An open boundary between lower continental crust and mantle: its role in crust formation and crustal recycling[END_REF][START_REF] Lustrino | How the delamination and detachment of lower crust can inuence basaltic magmatism[END_REF] have not been considered in this discussion because this process remains poorly documented in the French Massif

Central and can only be tackled in ancient orogenic systems via indirect arguments.

Figure 7.9: "Box-and-whiskers" plots for post-collisional mac magmas from the French Massif Central, regarded as primary mantle melts (N=359 for majors, N=59 for traces). Data from Couzinié et al. (2016). The thick black line is the median, the sides of the rectangles 1 st and 3 rd quartiles, the horizontal lines the max/min values and the circles outliers. Red line denotes the composition of the Bulk Continental Crust (BCC) reservoir after Rudnick and Gao (2003). The multi-element diagram is normalized to this composition.

Based on the example of the French Massif Central, Fig. 7.9 shows that postcollisional mac magmas (regarded as primary mantle melts) have lower median SiO 2 , CaO and Na 2 O contents than the bulk continental crust but higher TiO 2 , FeO t , MgO and K 2 O. Therefore, the new orogenic additions to the crust volume are more basic, mac and K-rich than the material lost and recycled in the mantle during continental subduction. From a trace element perspective, newly added materials are on average 23 times richer in incompatible elements than the bulk crust but overall display a similar pattern. This reects the predominance of recycled crustal materials in the trace element budget of the enriched mantle source (section 5.3). All in all, collisional orogenic episodes would recycle in the mantle materials of (roughly) bulk crust composition and partly replace them by a more basic, mac and K-rich component (Fig. 7.8c).

An overall limited record of crust reworking?

In the French Massif Central, examination of the zircon UPb date distribution of granites belonging to crust-derived peraluminous suites (MPG/CPG of [START_REF] Barbarin | A review of the relationships between granitoid types, their origins and their geodynamic environments[END_REF] reveals that as little as 32.6% (N=154/472) of the grains showing concordance between 95 105% yielded Variscan dates and thus pinpointed the timing of magma emplacement (see Chapter 5 and 6, additional data from Couzinié et al., 2014, andChelle-Michou et al., 2017). Such value is a maximum estimate because of the human operator tendency to target narrow zircon rims while analysing grains extracted from granites, in an attempt to better constrain the emplacement age (see section 7.2.3).

Interestingly, 30.1% (N=142/472) of the peraluminous granite zircon dates falls in the range 530560 Ma and thus attests to reworking of meta-granites from the Velay Orthogneiss Formation. This proportion is even higher in the southern part of the Velay Complex and the Masméjean dome where some granites lack any grain of Variscan age.

Similarly, migmatites developed at the expense of the VOF orthogneisses did not yield a single concordant Variscan date. The reasons for this have been discussed section 6.5 and lie in the low solubility of Zr in peraluminous melts and a range of kinetic factors. As a direct consequence, zircon extracted from Variscan crust-derived igneous rocks dominantly document pre-Variscan magmatic episodes.

From a crust evolution perspective, the Variscan case study suggests that igneous suites formed by pure crust reworking have a low potential to crystallize substantial amounts of magmatic zircon grains. This connects with the zircon fertility issue extensively discussed in [START_REF] Moecher | Dierential zircon fertility of source terranes and natural bias in the detrital zircon record: Implications for sedimentary provenance analysis[END_REF] and Dickinson (2008): peraluminous suites have low Zr contents, hence contain little zircon and on top of that only a third of them (in the Variscan case) are magmatic in origin. Consequently, the overall extent of the crust reworking record in large detrital zircon databases may be lower than currently thought. Nevertheless, it must be mentioned that in areas having experienced multiple reworking episodes (as the French Massif Central), the rst reworking event (the late-Ediacaran VOF meta-granites) may still be substantially documented because aliated zircon grains would also be encountered in igneous rocks formed during subsequent, younger crust reworking episodes (the Variscan peraluminous granites).

Further directions

The discussion conducted in this chapter outlines the extent to which the zircon UPb Hf(O) record of crust evolution may be ambiguous and challenging to interpret. The main reason for it lies in the fact that a given pattern may originate from a non-unique set of geological scenarios. Most accurate results are likely to be obtained when the petrological context of investigated zircon grains is fully assessed and provide guidance in interpreting the zircon record of crust evolution.

One possible way to fully explore the potential of zircon UPbHf data would be to independently document the detrital (modern or ancient) and igneous zircon records. This way, coupled petrological/age/isotopic information retrieved from igneous rocks could provide acute guidance to interpret the detrital zircon data, in essence more representative of the history of a given crust segment (see Dhuime et al., 2017, and references therein).

Therefore, a promising approach to constrain crust evolution on a global scale would be to: (i) reconstruct the evolutionary path of individual crust segments following the above-mentioned methodology; (ii) assemble all these pieces of information into a global model of continental crust evolution, pinpointing periods of major new crust production and documenting the associated mechanisms.

Analytical techniques

U-Pb isotopic analyses were carried out at Goethe Universität Frankfrut (GUF) by laser ablation using a Resolution M-50 (Resonetics) 193 nm ArF excimer laser system attached to ThermoFinnigan Element 2 sector field ICPMS. We applied the same methods as in Zeh and Gerdes (2012); a detailed description of these analytical techniques is available as Supplementary Mate

For zircon analyses we used a repetition rate of 5.5 Hz, and laser spot-sizes of 28, 33, 40 and 50 µm for measurements of unknowns, and 40 µm for zircon reference materials GJ-1, Plešovice, OG-1 and BB. Unknown monazite grains were analyzed with a repetition rate of 4 Hz, a spot size of 12 µm and reference monazite (Moacir, Manangoutry and an in-house standard WM) with a spot size of 33 µm. Resulting fluence was ~2.5 to 3 J•cm -2 . Sample surface was cleaned directly before each analysis by three pre-ablation pulses. Ablation was performed in a two-volume ablation cell (Laurin Technic, Australia) characterized by a very quick response time (<1 s until maximum signal strength is reached) and wash-out delay (<3 s to get <1% of maximum signal strength). It was fluxed during ablation with carrier gas consisting of a ~0.6 L min -1 He stream, mixed directly after the ablation cell with make-up gas consisting of ~0.07 L min -1 N 2 and 0.68 L min -1 Ar prior introduction into the plasma of the SF-ICP-MS. All gases had a purity of 99.999% and no homogenizer was used while mixing the gases, to prevent smoothing of the signal and thus be able to detect significant variations of the 207 Pb/ 206 Pb and 238 U/ 206 Pb ratios during measurements, possibly revealing the sequential sampling of different age domains within single zircon grains. Signal was tuned for maximum sensitivity for Pb and U while keeping low the production of oxides ( 254 UO/ 238 U ≤ 0.5%). The obtained sensitivity on zircon standard GJ-1 for 238 U and a 33 µm spot size varies from ~5000 cps•ppm -1 (session #1) to ~8000 cps•ppm -1 (session #2), at 5.5 Hz and ~3 J•cm -2 .

Data were acquired using time resolved-peak jumping, the detector being set to analogue mode for 232 Th and 238 U and counting mode for 204 (Hg+Pb), 206 Pb, 207 Pb and 208 Pb. A total of 356 mass scans were acquired over ~41 s measurement (20 s of background measurement followed by 21 s of sample ablation) and integrated to 89 ratios (4 mass scans per integration, time resolution = 0.46 s). Those ratios were subsequently corrected offline for background signal, common Pb, instrumental mass discrimination and Pb/U fractionation (both laser-induced during individual measurements, and over the day) using an in-house MS Excel © spreadsheet (Gerdes andZeh, 2006, 2009).

A common-Pb correction was carried out when necessary: for each ratio of an individual measurement, 204 Pb was estimated by subtracting the average background signal on mass 204, which mostly results from 204 Hg in the carrier gas (~500 cps), to the measured intensity. Composition of common Pb (i.e. 206 Pb/ 204 Pb and 207 Pb/ 204 Pb ratios) was determined using a model Pb composition (Stacey and Kramers, 1975) at the age of the sample, independently estimated using analyses devoid of common Pb. The inter-elemental fractionation ( 206 Pb/ 238 U) during the 21 s of sample ablation was corrected for each analysis by applying a linear regression through all measured ratios, excluding the outliers (±2σ), and considering that the intercept with the y-axis represents the 'true' ratio. Elemental fractionation over the analytical session, as well as instrumental mass discrimination, were corrected by normalization to the 206 Pb/ 238 U (0.0982) and 207 Pb/ 206 Pb (0.061) ratios of reference zircon GJ-1 (Jackson et al., 2004), using standard bracketing. Elemental concentrations in U and Pb were calculated using raw signal (in cps) of 238 U and 206 Pb for each spot, corrected from the analytical drift over the session (monitored using GJ-1), normalized to the recommended values of the GJ-1 zircon standard (U = 280.1 ppm; Pb = 25.5 ppm) and applying a spot size-dependent correction. Th/U ratio was determined for each spot using the mass fractionation-corrected 232 Th/ 238 U ratio, normalized to the recommended value of the GJ-1 zircon standard (Th/U = 0.0296).

Data from secondary standards were processed as unknowns to check the accuracy of the corrections. Our results (see Table S1, supplementary material) are all within error of the recommended TIMS values of the standard zircons Plešovice (weighted mean 206 Pb/ 238 U age = 337.13 ± 0.37 Ma; Sláma et al., 2008) et al., 2003), and the in-house standard WM (mean 206 Pb/ 238 U age = 1027 ± 2 Ma; Axel Gerdes, GUF, personal communication).

The quoted uncertainties for each individual analysis are (i) for the 206 Pb/ 238 U ratio, the quadratic addition of the within-run precision (2σ) with the external reproducibility of standard zircon GJ-1 during the corresponding analytical session (0.5 to 1.5%, 2 sigma; see Table S1, supplementary material); and (ii) for the 207 Pb/ 206 Pb ratio, a 207 Pb signal-dependent uncertainty propagation, as described by Gerdes and Zeh (2009). The 207 Pb/ 235 U ratio was calculated using the corrected 206 Pb/ 238 U and 207 Pb/ 206 Pb ratios and assuming a natural 238 U/ 235 U of 137.88, and its uncertainty was obtained by quadratic addition of propagated errors on both ratios. Age calculations and data plotting were performed using the Isoplot toolkit (Ludwig, 2008) v.4.15 for MS Excel © . The complete dataset is available as supplementary material (Table S2).

Detailed results of zircon and monazite U-Pb analyses

CPG

 Sample CHZ (Fig. S1) CHZ is from the Chalmazel granite, a plurikilometric screen of porphyritic biotite granite enclosed within the Velay granite at its northernmost margin. Four concordant spots from zircon cores yielded Ordovician to Neoproterozoic dates (410-625 Ma) and a highly discordant one (a99) has a Paleoproterozoic 207 Pb/ 206 Pb date of 2387 ± 7 Ma. The main population of analyses (n = 17), obtained from zircon rims or grains devoid of any core, define a Discordia with 206 Pb/ 238 U dates ranging between 275 and 332 Ma; the seven equivalent analyses with the highest 206 Pb/ 238 U ratios yield a Concordia date of 332.0 ± 2.0 Ma.

 Sample OL-13-06 (Fig. S1) OL-13-06 is a porphyritic biotite granite, representing the dominant phase of the large (>3000 km 2 ) Margeride batholith. The 33 analyses define a Discordia with an upper intercept at 321 ± 11 Ma (Fig. 4b); many spots have 206 Pb/ 238 U dates lower than 300 Ma (down to 31 Ma) and are generally characterized by large amounts of common Pb (between 1 and 10% and up to 40-60%). The eight analyses with the highest 206 Pb/ 238 U ratios define a Concordia date of 312.9 ± 2.0 Ma.

 Sample OL-13-11 (Fig. S1) OL-13-11 is from the Almance granite, a small laccolith flanking the western margin of the Velay dome (Feybesse et al., 1995). It contains zircon cores and xenocrysts from which 15 analyses yield early Carboniferous to Paleoproterozoic dates; 7 of them are >90% concordant and have early Carboniferous (~345 Ma; n = 3), Ordovician (a140 at ~475 Ma), late Neoproterozoic (550-580 Ma; n = 2) and Paleoproterozoic (a151 at ~2060 Ma) dates. Zircon rims and core-free grains are characterized by huge amounts of common Pb (between 2 and 52%) and highly variable 206Pb/238U dates dates ranging from 33 to 325 Ma (Figs. 4c and4e) and highly variable 206 Pb/ 238 U dates dates ranging from 85 to 317 Ma. They define a Discordia with an upper intercept of 315 ± 48 Ma (n = 15) and the five analyses with the highest 206 Pb/ 238 U ratios, including two spots with <5% of common Pb, yield a Concordia date of 314.5 ± 1.7 Ma. Eight monazite grains showing typically magmatic, oscillatory zoning (Fig. S8) were also analyzed and yield a Concordia date of 315.4 ± 0.9 Ma.

 Sample OL-13-14 (Fig. S1) OL-13-14 is a sample of the Chaise-Dieu intrusion, which consists of biotite-bearing, porphyritic to evengrained granites and granodiorites (Feybesse et al., 1995) at the western margin of the Velay dome. This samples contains many xenocrysts and zircons with cores, representing more than half of the dataset. Most of them are >90% concordant (n = 21 out of 28 analyses). The main populations are represented by zircons having Cambrian (535-545 Ma; n = 9), late Neoproterozoic (550-590 Ma; n = 8), middle Neoproterozoic (660-780 Ma; n = 4), Ordovician (450 -480Ma; n = 3) and discordant Neoarchean dates ( 207 Pb/ 206 Pb dates ~2430 Ma; (n = 13 + 2 not shown) n = 3). The zircon rims and core-free grains are characterized by extremely high common Pb contents, most often between 20 and 78%) and highly variable 206 Pb/ 238 U dates ranging from 33 to 325 Ma. They define a Discordia with an upper intercept of 321 ± 28 Ma (n = 18) and the four analyses with the highest 206 Pb/ 238 U ratios, including one with only ~1% common Pb and concordant at 318 Ma, yield a Concordia date of 318.3 ± 2.6 Ma. This date is identical to that obtained from 5 monazite grains (317.8 ± 1.3 Ma) from this sample, which are characterized by either well-developed, concentric oscillatory zoning or sector zoning (Fig. S8).

a139
 Sample OL-13-21 (Fig. S2) OL-13-21 represents an equigranular variety of the Saint-Dier granite pluton, in the northwest of the study area (Livradois domain). Among the 26 analyses carried out on zircons from this sample, 7 are from zircon cores or xenocrysts and provide dates ranging from Devonian (~365 Ma; n = 1), Cambrian-Neoproterozoic (515-565 Ma; n = 3) to Mesoproterozoic (1000-1500 Ma; n = 3, including concordant analyze a227 at 1444 ± 22 Ma). Analyses from rims or crystals without cores (n = 19) have Carboniferous 206 Pb/ 238 U dates between 300 and 343 Ma and lie along a Discordia with an upper intercept at 336 ± 11 Ma, identical to the Concordia date of 336.9 ± 1.8 Ma calculated using the eleven equivalent spots with the highest 206 Pb/ 238 U ratios.

 Sample TN-10 (Fig. S2) TN-10 is from from a plurimetric enclave of K-feldspar porphyritic, biotite-bearing granite within the Velay granite at the eastern margin of the latter, close to Colombier-le-Vieux. This sample contains a limited amount of zircon cores, that with the exception of two concordant spots having respectively Cambrian (a191, 206 Pb/ 238 U date = 539 ± 4 Ma) and Mesoproterozoic (a172, 207 Pb/ 206 U date = 1025 ± 16 Ma) dates, are dominantly Neoproterozoic (645-970 Ma; n = 4). A total of 27 spots from zircon-free cores are scattered along a Discordia with an upper intercept at 320 ± 12 Ma, the five analyses with the highest 206 Pb/ 238 U ratios providing an identical Concordia date of 321.9 ± 1.3 Ma.

 Sample TN-19 (Fig. S2) ), reported as shaded ellipses. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty.

MPG

 Sample HER (Fig. S3) HER is a coarse-grained muscovite-bearing and slightly deformed leucogranite collected from the Hermitage pluton, at the northwestern limit of the Velay complex. This granite displays C-S structures related to syntectonic emplacement along a crustal-scale D 3 shear zone (Barbarin, 1983). Seven analyses from zircon cores and xenocrysts yielded Silurian to Neoproterozoic dates between 400 and 850 Ma (n = 6) and one Archean date (concordant spot a245 at 2591 ± 17 Ma). For zircons rims and core-free crystals, the 206 Pb/ 238 U dates are scattered between 206 and 327 Ma, defining a Discordia with an upper intercept of 323 ± 7 Ma (n = 20) which is identical to the Concordia date of 325.7 ± 1.3 Ma calculated using the five analyses with the highest, equivalent 206 Pb/ 238 U ratios.

 Sample OL-13-08 (Fig. S3) OL-13-08 is an equigranular muscovite-bearing leucogranite collected from the Grandrieu granite body, associated with the Margeride CPG batholith. According to field relationships, the Grandrieu granite is younger than the latter (Lafon and Respaut, 1988;Ledru et al., 2001)  Sample OL-13-09 (Fig. S3) OL-13-09 is a medium-grained biotite-and muscovite-bearing granite from the Saint-Christophe d'Allier pluton, intrusive at the southwestern margin of the Velay dome and supposedly associated to the Margeride batholith (Feybesse et al., 1995). Most zircon analyses from those samples are from xenocrysts and zircon cores (n = 19 out of 25). Those yielded dates ranging from Devonian (a38, 206 Pb/ 238 U date of 391 ± 7 Ma), Ordovician (~490 Ma; n = 2), Cambrian (n = 10, including 9 analyses yielding a Concordia date of 534.8 ± 3.9 Ma) to late Neoproterozoic (550-570 Ma; n = 5), plus one middle Neoproterozoic spot (a32, 206 Pb/ 238 U date of 664 ± 12 Ma). Zircon grains devoid of any cores, or that are not xenocryrsts, are scarce: only 6 analyses were obtained from them. In spite of significant amounts of common Pb (0.25-21%), all are concordant, equivalent and define a Concordia date of 312.7 ± 2.3 Ma.

KCG

 Sample OL-13-24 (Fig. S4) OL-13-24 is a dark amphibole-and biotite-bearing quartz-diorite from the Gumières massif, a pluri-kilometric enclave in the Velay granite [START_REF] Barbarin | Notice explicative, Carte géol[END_REF]. Among the 32 analyses performed on zircons from this sample, 27 are within-error equivalent and define a Concordia date at 321.2 ± 1.2 Ma, while only 5 spots display slightly younger, significantly different 206 Pb/ 238 U dates (300-315 Ma).

 Sample PRC-56 (Fig. S4) PRC-56 represents an enclave of porphyritic, biotite-and amphibole-bearing granodiorite of KCG affinity within the Velay granite (sample PRC-57; see § 2.1) at the Pont-Rouge quarry. With the exception of 5 outliers having either significantly younger (n= 3) or older (n = 2) 206 Pb/ 238 U dates, all zircon spots from this sample are equivalent and define a Concordia date at 332.1 ± 0.7 Ma (n = 26).

 Sample SJV (Fig. S4) SJV is a porphyritic biotite-and amphibole-bearing granodiorite that represents the main facies of the Saint-Julien-la-Vêtre pluton, at the northernmost edge of the Velay complex (Forez Mountains). Out of 28 analyses -300 ± 420

-1 5 0 ± 6 2 0
Cores & Xen.

(n = 1) -6 9 5 ± 5 8 0

Cores & Xen.

(n = 2)

-1 9 3 ± 1 4 0
Cores & Xen.

( performed on zircons from this sample, one spot (a167) yielded a sub-concordant, Devonian date at ~375 Ma, whereas the rest show Carboniferous 206 Pb/ 238 U dates between 305 and 337 Ma (n = 27), defining a Discordia with an upper intercept of 331 ± 5 Ma. Among those, the analyses with the highest, within-error equivalent 206 Pb/ 238 U ratios yield a Concordia date of 330.1 ± 1.3 Ma (n = 14).

 Sample SGC-12-49B (Fig. S4) SGC-12-49B is a sample of K-feldspar porphyritic, biotite-bearing granite from the Largentière massif, in the Cévennes area, at an outcrop characterized by extensive magma mingling between the granite and vaugnerites. This sampl was already dated by Couzinié et al. (2014)  Sample PMV (Fig. S4) PMV was collected from the southern edge of the Pont-de-Montvert pluton (W of Vialas), a large intrusion belonging to the Mont-Lozère complex, which also includes several MPG plutons (Bougès, Finiels and Laubies granites) and intrusive in the PAU (Cévennes schists) south of the Velay complex. Analyses from two zircon cores yielded two concordant (a466) to strongly discordant (a472) Neoproterozoic dates of ~680 Ma.

Besides those, most zircon analyses are from grains devoid of any core (n = 24) and show a tight range of Permian to late Carboniferous 206 Pb/ 238 U dates . This dominant population plots along a Discordia with an upper intercept of 303 ± 3 Ma, identical to the Concordia date of 302.5 ± 0.9 Ma calculated using the 13 analyses with the highest, identical 206 Pb/ 238 U ratios.

 Sample SDZ (Fig. S4) SDZ represents the KCG intrusions in the Lyonnais moutains, at the northwest of the study area. This sample was specifically collected from an equigranular, medim-grained biotite granite variety of the Salt-en-Donzy pluton near Cottance.

Vaugnerites

 Sample 533-1 (Fig. S5) 533-1 was collected from hectometric-scale vaugnerite intrusions in migmatitic orthogneisses belonging to the LGU, a few kilometers SE of Lamastre (eastern part of the Velay dome). Zircons from this samples show a tight range of 206 Pb/ 238 U dates between 296 and 308 Ma, defining a Discordia trend with an upper intercept of 321 ± 33 Ma (n = 16). Out of them, only 4 show significantly lower 206 Pb/ 238 U dates than a main population of identical spots from which a Concordia date of 307.8 ± 1.6 Ma (n = 12) was obtained.

 Sample 533-2 (Fig. S5) 533-2 was sampled from a similar vaugnerite intrusion as 533-1. The zircon analyses from this sample show 206 Pb/ 238 U dates scattered between 288 and 311 Ma, plotting along a Discordia line with an upper intercept of 310 ± 6 Ma (n = 27). A Concordia date of 307.3 ± 1.3 Ma was calculated using the spots with the highest, identical 206 Pb/ 238 U ratios (n = 18).

 Sample LR-31 (Fig. S5) LR-31 belongs to a suite of gabbros and amphibole-bearing quartz diorites described by Vitel et al. (2000) in the inner part of the Velay granite, which show conspicuous mingling features with the latter (lobate contacts, intricate shapes) pointing to co-magmatism. Besides three outliers with 206 Pb/ 238 U dates below 292 Ma, all  Sample SC-13-02A (Fig. S6)

1 1 5 ± 4 3 0 -3 1 2 ± 4
In the composite Margeride granitic batholith (represented by sample OL-13-06, see § 2.1), vaugnerites occur as swarms of meter-to hectometer-sized enclaves. They outline a 20-km long NE-SW axis that extends out of the pluton in its easternmost part (Couturié, 1977). Although locally sharp, the contacts between vaugnerite and granite are most often intricate, rounded and irregular with lobate interfaces. Moreover, large K-feldspar xenocrysts of granitic origin are commonly observed in vaugnerites (Sabatier, 1991). Both lines of evidence support that mingling between both magmas took place. SC-13-02A is a SiO 2 -rich vaugnerite from the Margeride batholith, from which only few zircons were extracted. They show a restricted range of Carboniferous 206 Pb/ 238 U dates (300-317 Ma), and a Concordia date of 313.2 ± 2.5 Ma (n = 5) was calculated excluding the two outliers with the lowest 206 Pb/ 238 U ratios (a124 and a128).

 Sample SC-13-05 (Fig. S6) SC-13-05 was also collected in a vaugnerite enclave within the Margeride batholith. In contrast with SC-13-02A, it has high MgO and low SiO 2 contents. Zircon analyses from this sample show 206 Pb/ 238 U dates ranging from 279 to 313 Ma and define a Discordia with an upper intercept at 311 ± 3 Ma (n = 18). A Concordia date of 309.4 ± 1.5 Ma was obtained from the analyses with the highest, identical 206 Pb/ 238 U ratios (n = 12).

 Sample SC-13-09 (Fig. S6) SC-13-09 was sampled near Pubellier, at the western edge of the Velay dome, and belongs to a small stock of pyroxene-and amphibole-bearing syenodiorite (Ledru et al., 1994) intrusive in the LGU orthogneisses. With the exception of few analyses with relatively high common Pb contents (1-8%) and showing 206 Pb/ 238 U dates of 294 to 303 Ma (n = 5), as well as one outlier (spot a271) displaying a 206 Pb/ 238 U date of 336 Ma (Fig. 9c), all zircon analyses are concordant and identical within error, corresponding to a Concordia date of 309.7 ± 1.2 Ma (n = 21).

 Sample SC-13-14 (Fig. S6) SC-13-14 is a very SiO 2 -poor (<45 wt.%) vaugnerite collected from the Lyonnais area, close to Marcenod at the SW edge of the Soucieu granite. It is typical of vaugnerite occurrences North of the Velay dome, which intruded the UGU gneisses as small bodies along dextral NE-SW shear zones [START_REF] Lardeaux | Champs de déformation superposés dans la chaîne varisque. Exemple de la zone nord des Monts du Lyonnais (Massif Central français[END_REF] and are coeval with a suite of syn-kinematic granites. From this sample, four analyses were obtained from zircon cores: analyses a22 and a32 display concordant, Devonian Insets in the bottom right of (d) represent close-ups to the analyses from zircon cores or xenocrysts ("Xen."), reported as shaded ellipses.

Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty.

Ma respectively, whereas another concordant spot (a28) shows an Ordovician  Sample SC-13-19 (Fig. S6) SC-13-19 was collected in the Chassagny quarry in the Lyonnais area, where interactions between mafic and felsic magmas (corresponding to the associated granites) are well-exposed. Zircon analyses from this sample all show Carboniferous 206 Pb/ 238 U dates ranging from 302 to 337 Ma, plotting along a Discordia with an upper intercept of 334 ± 3 Ma (n = 26). A Concordia date of 333.9 ± 1.4 Ma was obtained using the equivalent analyses with the highest 206 Pb/ 238 U ratios (n = 17).

 Sample SGC-12-13 (Fig. S7) SGC-12-13 is a coarse-grained lamprophyre dyke crosscutting the low-grade Cevennes schists of the PAU, south of the Velay dome. It was collected close to Saint-Jean-de-Pourcharesse, 10 km to the East of the contact between the latter and the Borne KCG pluton.  Sample SGC-12-26 (Fig. S7) SGC-12-26 was sampled from a decameter-sized, rounded vaugnerite enclave in migmatitic paragneisses at the southern edge of the Velay complex, along the Pont-de-Bayzan road cut (see Fig. 2b in Couzinié et al. 2014). Out of 24 zircon analyses from this sample, most have 206 Pb/ 238 U ratios that are identical within error and define a Concordia date of 306.1 ± 1.3 Ma (n = 20), whereas the other spots display slightly younger 206 Pb/ 238 U dates down to 290 Ma.

 Sample SGC-12-39 (Fig. S7) SGC-12-39 was collected in a vaugnerite sill intrusive in migmatitic paragneisses East of Loubaresse, at the southermost edge of the Velay dome. Apart from two outliers with Permian 206 Pb/ 238 U dates (a254 and a255), all zircon analyses from this sample are identical within error and define a late Carboniferous, Concordia date of 306.6 ± 1.6 Ma (n = 12).

 Sample SGC-12-42 (Fig. S7) SGC-12-42 represents a rounded, meter-sized vaugnerite enclave within migmatitic paragneisses near Meyras, at the southern limit of the Velay dome. Zircon analyses show a restricted range of 206 Pb/ 238 U dates between 293 and 310 Ma (n = 16). The equivalent analyses with the highest 206 Pb/ 238 U ratios yield a Concordia date of 305.9 ± 1.7 Ma (n = 11). (b) U and Pb contents (in ppm) and Th/U ratios were calculated relative to GJ-1 reference zircon (U = 280 ppm; Pb = 25.5 ppm).

(c) Percentage of the common Pb on the 206 Pb (b.d. = below dectection limit) calculated using the interference-and background-corrected 204 Pb signal and common Pb model composition of Stacey & Kramers (1975). These new measurements were added to a database gathering analyses of post-collisional mafic magmas from the Eastern French Massif Central [START_REF] Agranier | Un exemple de magmatisme ultrapotassique syn-orogénique : les lamprophyres du Massif Central français[END_REF][START_REF] Aït-Malek | Petrology, geochemistry and U/Pb geochronology of acid-basic associations: examples from SE Velay (French Massif Central) and western anti-Atlas (Morocco)[END_REF]Ait Malek et al., 1995;[START_REF] Barbarin | Notice explicative, Carte géol[END_REF][START_REF] Batias | Le massif de granite de Tournon-Saint-Cierges (Massif Central français)[END_REF][START_REF] Bellanger | Vaugnérites et roches associées des Cévennes Médianes : quelques aspects pétrologiques et géochimiques[END_REF]Couturié, 1977;Downes et al., 1997;[START_REF] El Mouraouah | Palingenèse du granite du Velay autour de la diorite du Peyron (Burzetn Ardèche, MCF), approche pétrographique et géochimique de la genèse des granites tardimigmatitiques[END_REF]Ledru et al., 1994;Michon, 1979;[START_REF] Montel | Première découverte d'une vaugnérite à orthopyroxène : pétrographie, géochimie et conséquences pour la genèse des vaugnérites[END_REF]Négron, 1979;[START_REF] Sabatier | Remarques préliminaires sur quelques vaugnérites du Massif central[END_REF]Sabatier, , 1984Sabatier, , 1991;;Vitel et al., 2000;[START_REF] Williamson | The petrology of the Velay granite complex, Massif Central France[END_REF].

(

Zircon extraction and imaging

Samples weighing 5-10 kg were reduced using jaw and disc mills and sieved to <500 µm. Zircons were concentrated using conventional methods (Wilfley table, heavy liquids). After being hand-

Zircon U-Pb dating procedures

U-Pb isotopic analyses were carried out at Goethe Universität Frankfrut (GUF) by laser ablation using a Resolution M-50 (Resonetics) 193 nm ArF excimer laser system attached to a ThermoFinnigan Element 2 sector field ICPMS. We used a repetition rate of 5.5 Hz, laser spotsizes of 28 or 33μm for measurements of unknowns, and 40 μm for zircon reference materials GJ-1, Plešovice, OG-1 and BB. Resulting fluence was ~2.5 to 3 J•cm-2. The sample surface was cleaned directly before each analysis by three pre-ablation pulses. Ablation was performed in a two-volume ablation cell (Laurin Technic, Australia) characterized by a very quick response time (<1 s until maximum signal strength is reached) and wash-out delay (<3 s to get <1% of maximum signal strength). It was fluxed during ablation with a carrier gas consisting of a ~0.6 L min -1 He stream, mixed directly after the ablation cell with make-up gas consisting of ~0.07 L min -1 N2 and 0.68 L min -1 Ar prior to introduction into the plasma of the SF-ICP-MS. All gases had a purity of 99.999% and no homogenizer was used while mixing the gases, to prevent smoothing of the signal and thus be able to detect significant variations of the 207 Pb/ 206 Pb and 238 U/ 206 Pb ratios during measurements, possibly revealing the sequential sampling of different age domains within single zircon grains. The signal was tuned for maximum sensitivity for Pb and U while keeping low the production of oxides ( 254 UO/ 238 U ≤ 0.5%). The obtained sensitivity on zircon standard GJ-1 for 238 U and a 33 μm spot size was about ~5000 cps•ppm -1 at 5.5 Hz and ~3 J•cm -2 .

Data were acquired using time resolved-peak jumping, the detector being set to analogue mode for 232 Th and 238 U and counting mode for 204 (Hg+Pb), 206 Pb, 207 Pb and 208 Pb. A total of 356 mass scans were acquired over ~41 s measurement (20 s of background measurement followed by 21 s of sample ablation) and integrated to 89 ratios (4 mass scans per integration, time resolution = 0.46 s). These ratios were subsequently corrected offline for background signal, common Pb, instrumental mass discrimination and Pb/U fractionation (both laser-induced during individual measurements, and over the day) using an in-house MS Excel© spreadsheet (Gerdes andZeh, 2006, 2009).

A common-Pb correction was carried out when necessary: for each ratio of an individual measurement, 204 Pb was estimated by subtracting the average background signal on mass 204, which mostly results from 204 Hg in the carrier gas (~500 cps), to the measured intensity.

Composition of common Pb (i.e. 206 Pb/ 204 Pb and 207 Pb/ 204 Pb ratios) was determined using a model Pb composition (Stacey and Kramers, 1975) at the age of the sample, independently estimated using analyses devoid of common Pb. The inter-elemental fractionation ( 206 Pb/ 238 U) during the 21 s of sample ablation was corrected for each analysis by applying a linear regression through all measured ratios, excluding the outliers (±2σ), and considering that the intercept with the y-axis represents the 'true' ratio. Elemental fractionation over the analytical session, as well as instrumental mass discrimination, were corrected by normalization to the 206 Pb/ 238 U (0.0982) and 207 Pb/ 206 Pb (0.061) ratios of reference zircon GJ-1 (Jackson et al., 2004), using standard bracketing.

Elemental concentrations in U and Pb were calculated using raw signal (in cps) of 238 U and 206 Pb for each spot, corrected from the analytical drift over the session (monitored using GJ-1), normalized to the recommended values of the GJ-1 zircon standard (U = 280.1 ppm; Pb = 25.5 ppm) and applying a spot size-dependent correction. Th/U ratio was determined for each spot using the mass fractionation-corrected 232 Th/ 238 U ratio, normalized to the recommended value of the GJ-1 zircon standard (Th/U = 0.0296). Data from secondary standards were processed as unknowns to check the accuracy of the corrections. The quoted uncertainties for each individual analysis are (i) for the 206 Pb/ 238 U ratio, the quadratic addition of the within-run precision (2σ) with the external reproducibility of standard zircon GJ-1 during the corresponding analytical session (0.5 to 1.5%, 2 sigma); and (ii) for the 207 Pb/ 206 Pb ratio, a 207 Pb signal-dependent uncertainty propagation, as described by Gerdes and Zeh (2009).

The 207 Pb/ 235 U ratio was calculated using the corrected 206 Pb/ 238 U and 207 Pb/ 206 Pb ratios and assuming a natural 238 U/ 235 U of 137.88, and its uncertainty was obtained by quadratic addition of propagated errors on both ratios. Age calculations and data plotting were performed using the Isoplot toolkit (Ludwig, 2008) v.4.15 for MS Excel©.

Zircon Lu-Hf isotopes

Zircon Lu-Hf analyses for standards and samples are displayed Tables S2 andS3 respectively.

Measurements were performed on magmatic zircons at GUF, using a Thermo-Finnigan Neptune multicollector ICP-MS attached to a Resolution M-50 193 nm Ar-F excimer laser ablation system, equipped with a two-volume Laurin Technic ablation cell. The latter is fluxed by high-purity, He carrier gas (~0.6 L•min -1 ) and is characterized by rapid response time (< 3 s to get maximum signal strength) and wash-out delay (<5 s to get <1% of maximum signal strength). Laser spots with diameters of 33 µm were drilled (Fig. 5) with repetition rates of 5.5 Hz and an energy density of ~6 J•cm -2 . Make-up gas consisting of high-purity Ar (~0.75 L•min -1 ) and N2 (~0.07 L•min -1 ) was admixed to the carrier gas to improve sensitivity. Post-ablation homogenization is performed by fluxing the gases through a Resolution Instruments Squid ® tubing. Data were acquired using multicollector static mode, during 58 s of measurement characterized by 1.052 s integration time (55 baseline-corrected ratios). 172 Yb, 173 Yb and 175 Lu masses were monitored to allow the correction of isobaric interferences ( 176 Yb and 176 Lu on 176 Hf). Instrumental mass bias for Yb isotopes (calculation of β Yb ) was monitored for each measurement using an exponential law, and corrected to the natural ratio 172 Yb/ 173 Yb = 1.35351. Mass fractionation of Lu isotopes was assumed identical to that of Yb isotopes (β Lu = β Yb ). The isobaric interferences were subsequently corrected to mass bias-corrected 176 Yb/ 173 Yb = 0.79502 and 176 Lu/ 175 Lu = 0.02656 (see Gerdes and Zeh (2006)).

Mass bias for Hf isotopes (β Hf ) was determined using an exponential law and normalized to 179 Hf/ 177 Hf = 0.7325. Accuracy and external reproducibility of the method were controlled by repeated analyses of reference zircon standards GJ-1 (Jackson et al., 2004;Morel et al., 2008),

Plešovice (Sláma et al., 2008), Degeo (in-house) and 91500 (Wiedenbeck et al., 2004). The quoted uncertainties on 176 Hf/ 177 Hf ratios and εHf(t) are quadratic additions of within-run precision of each measurement with the external reproducibility (2 S.D.) of the reference zircon standard GJ-1 (~70 ppm, see data table ). Data reduction was carried out using an in-house MS Excel © spreadsheet (Gerdes andZeh, 2006, 2009).

Calculations of initial 176 Hf/ 177 Hf ratios were performed using the individual 176 Lu/ 177 Hf ratio of each measurement, a decay constant of λ176Lu = 1.867 × 10 -11 [START_REF] Scherer | Calibration of the Lutetium-Hafnium clock[END_REF]Söderlund et al., 2004) and the emplacement age obtained by U-Pb zircon dating. For the calculation of the εHf(t), parameters of the chondritic uniform reservoir (CHUR) recommended by Bouvier et al. (2008) were used ( 176 Lu/ 177 Hf = 0.0336; 176 Hf/ 177 Hf = 0.282785). Two-step depleted mantle (DM)

Hf model ages (TDM2 C ) were calculated using a DM model considering linear regression from present-day depleted mantle as recommended by Griffin et al. (2002), i.e. 176 Lu/ 177 Hf = 0.0384 and 176 Hf/ 177 Hf = 0.28325, and an average 176 Lu/ 177 Hf of 0.0113 for the crustal reservoir.

Zircon O isotopes

Oxygen isotopes were analyzed with the IBERSIMS SHRIMP IIe/mc ion microprobe using multi collector mode following the method described by [START_REF] Ickert | Determining high precision, in situ, oxygen isotope ratios with a SHRIMP II: Analyses of MPI-DING silicate-glass reference materials and zircon from contrasting granites[END_REF]. Zircons were cast in "megamounts", i.e., 35 mm epoxy discs fixed in front of the mount holder so that no metallic parts or surface discontinuities faced the secondary ions extraction plate. The mount was coated with a 12 nm thick gold layer. The primary beam consisted of a 15 kV and 3 to 3.5 nA Cs ion beam focused to produce a 17x20 µm elliptical spot on the sample. The electric charge of the nonconductive zircons caused by the primary beam was neutralised with an electron beam that impacted the sample in a ≈200 µm diameter spot concentric with the Cs beam. The source slit was fixed at 150 µm and the secondary 18 O and 16 O were simultaneous measured in static mode using two Faraday cups with entry slits of 300 µm. The sample was pre-sputtered for 180 s prior to analyses. During the last 90 s of the pre-sputtering time the secondary beam and the electron beam were steered to obtain the maximum signal on the Faraday cups. The measurement consisted in two sets of six scans, each scan was 10 s. The mass fractionation caused by Earth's magnetic field was compensated with Hemholtz coils operated at -309 mA. This eliminated the mass fractionation related to the horizontal steering of the secondary beam. Electron-induced secondary-ion emission (EISI) was measured for 10 s at the beginning of each scan and at the end of the measurement and subtracted accordingly. Data reduction was done using the POXI software developed by Peter Lanc

and Peter Holden at the ANU. The zircon standard TEMORA-2 (δ 18 O = 8.2 ± 0.3 ‰, Black et al., 2004|) was measured several times at the beginning of the session and after every four unknowns, and crosschecked against the 91500 zircon standard (δ 18 O = 9.86 ± 0.11 ‰, Wiedenbeck et al., 2004); ten to fifteen replicates of which were measured as unknowns interspersed with these. Hf/ 177 Hf = 0.282785 (Bouvier et al ., 2008).

( Hf/ 177 Hf of 0.0375 and 0.28312, respectively (Naeraa et al., 2012). analysis using an Oxford Instruments ® X-Max 20 mm 2 detector and the Oxford INCA software. Beam conditions were 20 kV accelerating voltage, 1.5 nA probe current, a working distance of 8.5 mm and a specimen beam current of 20 nA. Analyses were quantied using natural mineral standards.

B.2.2 Data tables

Mineral compositions obtained in the course of this study are reported in the following tables:

Table B2: Mineral compositions of the RV-1 and RV-2 amphibole-bearing gneisses from the Upper Gneiss Unit, Riverie quarry, see section 3.5.

Table B3: Mineral compositions of the biotite-bearing granite RV-3, Riverie quarry, see section 5.2. 46.43 46.12 45.61 47.48 44.43 46.62 46.41 44.03 43.83 47.46 47.82 44.98 46.33 TiO 2 0.86 0.94 1.04 0.97 1.09 0.85 0.86 1.10 1.21 0.88 0.80 1.02 0.85 Al 2 O 3 8.51 8. 67 9.53 7.58 10.06 8.79 8.39 9.68 9.83 7.81 7.69 9.53 7.97 FeO 15.15 14.76 15.05 13.85 15.73 14.71 14.81 15.64 15.33 14.58 14.95 15.95 14.00 MnO 0.55 0.58 0.46 0.53 0.56 0.53 0.58 0.49 0.46 0.59 0.60 0.49 0.44 MgO 13.33 13.44 13.04 13.71 12.23 13.09 13.32 12.23 11.84 13.61 13.66 12.47 13.17 CaO 10.80 11.30 11.42 11.55 11.39 10.94 11.22 11.10 11.45 11.47 11.34 11.12 23 9.49 8.22 8.40 9.75 8.28 9.48 6.96 8.79 9.19 8.61 6.95 9.04 FeO 15.31 16.35 15.98 15.42 16.76 15.97 16.47 15.17 16.51 16.50 16.38 15.51 16.98 MnO 0.56 0.50 0.57 0.38 0.48 0.42 0.39 0.47 0.63 0.42 0.46 0.48 0.47 MgO 13.77 12.04 13.08 13.00 11.96 12.88 12.22 13.91 12.50 12.30 12.72 13.96 12.17 CaO 10.35 11.39 11.10 11.72 11.54 11.90 11.68 11.47 11.01 11.45 11.06 11.29 14.16 14.40 14.01 14.33 14.34 14.47 14.54 14.79 14.25 14.52 14.18 14.49 14.62 14.46 14.74 15.03 FeO 19.79 19.62 17.39 17.47 18.64 18.18 17.38 17.52 17.42 17.50 17.96 17.64 17.26 17.52 17.51 19.25 MnO 0.17 0.24 0.15 0.18 0.16 0.13 0.23 0.21 0.14 0.15 0.20 0.00 0.00 0.00 0.23 0.24 MgO 11.83 11.92 12.73 13.03 13.56 13.37 13.32 13.60 12.63 12.84 12.99 12.94 12.96 12.79 12.94 13.23 CaO 0.21 0.13 0.00 0.00 0.16 0.13 0.13 0.12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Na 2 O 0.00 0.19 0.19 0.22 0.00 0.00 0.19 0.23 0.00 0.24 0.27 0.00 0.00 0.00 0.29 0.00 23.35 23.75 24.09 23.69 23.69 23.54 24.19 23.71 23.84 24.15 23.98 23.93 23.78 23.23 23.95 23.60 23.70 24.25 24.15 23.72 23.63 23.77 17.93 18.73 17.24 18.10 17.63 17.68 19.75 18.59 18.83 18.35 19.37 19.46 19.35 19.43 18.43 18.52 17.90 MnO 0.00 0.00 0.00 0.00 0.00 0.00 0.13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.18 0.14 MgO 11.94 12.00 12.24 12.35 12.29 12.14 11.38 12.32 10.96 11.63 10.79 11.07 10.91 11.23 11.66 11.80 11.44 CaO 0.18 0.00 0.00 0.00 0.00 0.00 0.12 0.00 0.00 0.17 0.00 0.00 0.12 0.00 0.13 0.12 0.00 Na 2 O 0.00 0.00 0.00 0.22 0.00 0.00 0.00 0.20 0.21 0.00 0.20 0.00 0.00 0.00 0.00 0.00 0.00 K 93.11 93.58 92.75 93.42 93.25 92.32 92.54 93.40 90.65 91.00 92.99 92.87 93.38 92.82 93.32 92.34 93.09 Ox. 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 Si Al vi 0.23 0.24 0.32 0.26 0.24 0.28 0.25 0.27 0.27 0.23 0.27 0.28 0.29 0.28 0.30 0.25 0.25 Ti OH* 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 FeO 0.14 0.00 0.00 0.00 0.00 0.00 0.16 0.00 0.00 0.00 0.00 CaO 5.34 5.40 5.23 5.39 5.23 5.20 5.32 5.29 5.21 5.

B.3 Zircon UPb isotope measurements

This section presents the analytical procedures and results of UPb dating sessions which have not been the subject of publication. The reader can nd the analytical notes and comprehensive dataset of published results in the Supplementary materials of the articles (see section A).

B.3.1 Analytical details on the GUF session

Zircon UPb isotopic analyses were carried out at Goethe Universität Frankfrut (GUF) by laser ablation using a Resolution M-50 (Resonetics) 193 nm ArF excimer laser system attached to ThermoFinnigan Element 2 sector eld ICPMS. We applied the same methods as in Zeh and Gerdes (2012).

We used a repetition rate of 5.5 Hz, and laser spot-sizes of 20 and 30 µm for measurements of unknowns, and zircon reference materials GJ-1, Ple²ovice and BB-16. Resulting uence was ∼2.5 to 3 J.cm -2 . Sample surface was cleaned directly before each analysis by three pre-ablation pulses. Ablation was performed in a two-volume ablation cell (Laurin Technic, Australia) characterized by a very quick response time (<1 s until maximum signal strength is reached) and wash-out delay (<3 s to get <1% of maximum signal strength). It was uxed during ablation with carrier gas consisting of a ∼0.6 L.min -1 He stream, mixed directly after the ablation cell with make-up gas consisting of ∼0.07

L.min -1 N 2 and 0.68 L.min -1 Ar prior introduction into the plasma of the SFICP MS. All gases had a purity of 99.999% and no homogenizer was used while mixing the gases, to prevent smoothing of the signal and thus be able to detect signicant varia- the day) using an in-house MS Excel ® spreadsheet (Gerdes and Zeh, 2006;2009).

A large number of analyses in our dataset shows moderate to high common Pb (Pb c ) contents. Correcting isotopic compositions from Pb c is not straightforward for three main reasons. First, there is a clear uncertainty on the age at which Pb c was incorpo- rated in the zircon structure. This is particularly true for inherited zircon grains (zircon cores, xenocrysts). Indeed, their Pb c might be as old as the grain itself (incorporated during crystallization) or subsequently added, for instance via interaction with metamorphic uids. Moreover, considering that the age of Pb c incorporation is given by the 206 Pb/ 238 U date does not account for the potential eect of Pb loss and resulting discor- Aware of all the above-mentioned caveats and in an attempt to hamper the yield of meaningless, Pb c -corrected concordant dates, we decided to restrict the use of a Pb c correction to zircons grains: (i) extracted from granite samples, for which a late Carboniferous to early Permian intrusion age can be expected given the regional geological context (see Laurent et al., 2017 and references therein), (ii) showing 206 Pb/ 238 U dates close to that of concordant, Pb c -free zircon from the same sample. The methodology applied is as follows.

For each ratio of an individual measurement, 204 Pb was estimated by subtracting the average background signal on mass 204, which mostly results from 204 Hg in the carrier gas The quoted uncertainties for each individual analysis are (i) for the 206 Pb/ 238 U ratio, the quadratic addition of the within-run precision (2σ) with the external reproducibility of standard zircon GJ-1 during the corresponding analytical session (0.5 to 1.5%, 2σ); and (ii) for the 207 Pb/ 206 Pb ratio, a 207 Pb signal-dependent uncertainty propagation, as described by Gerdes and Zeh (2009). The 207 Pb/ 235 U ratio was calculated using the 206 Pb/ 238 U and 207 Pb/ 206 Pb ratios and assuming a natural 238 U/ 235 U of 137.88, and its uncertainty was obtained by quadratic addition of propagated errors on both ratios.

Age calculations and data plotting were performed using the Isoplot/Ex v.4.15 (Ludwig, 2008) for MS Excel ® .

B.3.2 Analytical details on the SUN session

U-Pb data were obtained at the Central Analytical Facility, Stellenbosch University, and were acquired by laser ablation single collector magnetic sector eld inductively coupled plasmamass spectrometry (LASFICPMS) employing a Thermo Finnigan Element 2 mass spectrometer coupled to a Resonetics Resolution S155 excimer laser ablation system. The methods employed for analysis are described in detail by [START_REF] Frei | Precise and accurate in situ UPb dating of zircon with high sample throughput by automated LA-SF-ICP-MS[END_REF]. Data processing was performed using an in-house MS Excel ® spreadsheet (Gerdes and Zeh, 2006). The GJ-1 zircon reference material (Jackson et al., 2004) was used as primary standard. For quality control, the 91500 [START_REF] Wiedenbeck | Three natural zircon standards for U-Th-Pb, Lu-Hf, trace element and REE analyses[END_REF]2004), Temora [START_REF] Black | TEMORA 1: a new zircon standard for phanerozoic UPb geochronology[END_REF]2004) and Ple²ovice (Sláma et al., 2008a) zircon reference materials were analysed, and the results were in agreement with the published IDTIMS ages (Fig. B.2). The calculation of dates, as well as plotting of Tera-Wasserburg diagram were performed using Isoplot/Ex v.4.15 (Ludwig, 2008) for MS Excel ® .

B.3.3 Analytical details on the ETH session

Zircon UPb isotopic analyses were carried out at ETH Zürich, Switzerland by laser ablation inductively coupled plasma sector eld mass spectrometry (LAICP SFMS) using a RESOlution M-50 (Resonetics/ASI) 193 nm ArF excimer laser system attached to a ThermoFinnigan Element XR mass spectrometer.

We used a laser repetition rate of 5 Hz, a spot size of 20 or 30 µm and a laser output energy of 80 to 100 mJ, corresponding to an energy density on sample of c. 2.0 to 2.5 J.cm -2 . The sample surface was cleaned immediately before each analysis by three pre- ablation pulses. Ablation was performed in a Laurin Technic S-155 dual-volume ablation cell uxed with carrier gas consisting of c. 0.7 L.min -1 He (5.0 grade), mixed directly after the ablation cell with sample gas consisting of c. 1 L.min -1 Ar (6.0 grade) prior to introduction into the plasma of the ICPSFMS. We used Ni X-cones specically dedicated to zircon UPb geochronology. The signal was tuned for maximum sensitivity for Th and U while keeping low the production of oxides (the resulting 248 ThO + / 232 Th + intensities for the following isotopes were acquired using time resolved-peak jumping (between brackets are the dwell times in ms) and triple detector mode: 202 Hg (10), 204 (Hg+Pb) (20), 206 Pb (100), 207 Pb (100), 208 Pb (10), 232 Th (10), 235 U (10), 238 U (20) (total sweep time of 0.29 s). A total of 165 mass scans were acquired over c. 50 s measurement (20 s of background measurement followed by 30 s of sample ablation).

The resulting intensities were subsequently processed oine with the Igor Pro Iolite v2.5 software [START_REF] Hellstrom | Iolite: Software for spatially resolved LA-(quad and MC) ICP-MS analysis[END_REF], using the VizualAge data reduction scheme [START_REF] Petrus | VizualAge: A novel approach to laser ablation ICP-MS U-Pb geochronology data reduction[END_REF]. Background-subtracted intensities were used to calculate isotope ratios, which were corrected for downhole Pb/U and Pb/Th fractionation (after [START_REF] Paton | Improved laser ablation U-Pb zircon geochronology through robust downhole fractionation correction[END_REF], instrumental mass discrimination and drift through the analytical session by standard bracketing against zircon reference material GJ-1 (using isotope ratios recommended by [START_REF] Horstwood | Community-Derived Standards for LA-ICP-MS U-(Th-)Pb Geochronology -Uncertainty Propagation, Age Interpretation and Data Reporting[END_REF]. No common Pb correction was carried out. Elemental concentrations in U, Th and Pb were calculated using average intensities (in cps) of 238 U, 232 Th and 208 Pb for each spot and sensitivities calculated from the GJ-1 zircon standard, after correction of sensitivity drift over the session. The quoted uncertainties for each individual analysis correspond to the internal (2 S.E.) statistical error and propagated uncertainty based on the scatter of the primary reference material (see [START_REF] Paton | Improved laser ablation U-Pb zircon geochronology through robust downhole fractionation correction[END_REF].

Data from secondary zircon reference materials were processed as unknowns to check the accuracy of the corrections (Fig. B.3 and B.4. The obtained U-Pb dates are close to the reference ages determined by TIMS for the zircon reference materials Ple²ovice (Sláma et al., 2008a), 91500 [START_REF] Wiedenbeck | Three natural zircon standards for U-Th-Pb, Lu-Hf, trace element and REE analyses[END_REF]2004) and Temora [START_REF] Black | TEMORA 1: a new zircon standard for phanerozoic UPb geochronology[END_REF].

Age calculations and data plotting were performed using the Isoplot toolkit (Ludwig, 2008) v.4.15 for MS Excel ® .

B.3.4 Zircon UPb results of Chapter 6

Orthogneisses CHA-15-35 Forty-two measurements were conducted on 30 zircon grains. Eight analyses revealed high estimated common Pb contents (>1.2%) and will not be examined further because the calculated discordant dates can be interpreted as a combination of Pb loss and incorporation of Pb c without any possibility to discriminate between both.

Seventeen zircon spots are discordant (concordance <93%) with 206 Pb/ 238 U dates rang- ing from 469 ± 7 Ma (a163) to 589 ± 8 Ma and 207 Pb/ 206 Pb dates from 547 ± 20 Ma (a192) to 736 ± 38 Ma (a144). Estimated common Pb concentrations in the spotted zircon domains are low to moderate (up to 0.9%). Seventeen measurements performed on zircon rims and core-free grains yielded concordant 206 Pb/ 238 U dates out of which eleven are statistically equivalent and allow calculation of a Concordia date of 544.1 ± 4.9 Ma (MSWD of concordance+equivalence=0.79). Three analyses conducted on two zircon cores and one zircon rim yielded older 206 Pb/ 238 U dates of 559 ± 8 (a161 and a166) and 570 ± 8 Ma (a190), respectively. Three spots drilled on zircon rims and corefree grains gave younger 206 Pb/ 238 U dates than the main population ranging from 532 ± 8 Ma (a178) to 528 ± 7 Ma (a184) but all three are nearly discordant.

CHA-15-52 Twenty-eight spots were drilled on 23 grains. Five analyses showed substantial amounts of Pb c (>1.2%) and were not considered further. Two analyses of zircon cores yielded slightly discordant (concordance: c. 92%) 207 Pb/ 206 Pb dates of 2481 ± 8 Ma (a73) and 2486 ± 7 Ma (a83). Two measurements yielded identical concordant 206 Pb/ 238 U dates of 702 ± 12 Ma (a79, homogeneous grain) and 701 ± 10 Ma (a60, core). One measurement performed on a zircon rim (a72) has a moderate Pb c content (c. 0.8%) and a discordant (concordance: 69%) 207 Pb/ 206 Pb date of 787 ± 32 Ma. The 18 remaining analyses displayed negligible to low estimated Pb c concentrations (<0.4%).

Ten spots drilled on a core and a rim gave concordant 206 Pb/ 238 U dates of 573 ± 9 Ma (a82) and 572 ± 10 Ma (a58). Eight measurements performed on cores, rims and homogeneous grains yielded statistically equivalent 206 Pb/ 238 U dates out of which a Concordia date of 544.4 ± 5.2 Ma (MSWD C+E =0.9) can be calculated. The eight last spots are all discordant with 207 Pb/ 206 Pb dates ranging from 585 ± 22 Ma (a85) down to 547 ± 23 Ma (a87).

Granites

CHA-15-24 Thirty spots were drilled on 26 zircons grains which often appear homogeneous in CL-images and seldom show core-rim relationships. Sixteen spots are markedly discordant and have large amounts of common Pb (often >3%). Two spots with negligible amounts of Pb c yielded discordant 207 Pb/ 206 Pb dates of 753 ± 30 (a346, homogenous zircon) and 772 ± 20 (a345, zircon core) Ma respectively. Two more discordant (concordance: c. 40%) analyses performed on homogeneous zircons showed moderate amounts of Pb c (from 0.6 to 1.2%) and yielded 207 Pb/ 206 Pb dates of 615 ± 32 (a317) and 579 ± 30 Ma (a355). Five measurements conducted on a zircon core, three rims and an homogeneous zircon yielded similar 206 Pb/ 238 U dates ranging from 560 ± 8 Ma (a359) down to 537 ± 10 Ma (a326). Two analyses conducted on homogeneous zircon grains show concordant 206 Pb/ 238 U dates of 515 ± 8 (a322) and 332 ± 5 Ma (a336) respectively.

Finally, a zircon rim and a homogeneous zircon, both devoid of Pb c produced equivalent 206 Pb/ 238 U dates of 308 ± 5 (a335) and 305 ± 5 (a343) Ma respectively. Common-lead corrected (see introductory section for the method) rim analysis a344 shows a similar 206 Pb/ 238 U date of 304 ± 5 Ma. A Concordia date of 305.8 ± 4.4 Ma can be calculated out of these 3 measurements with a MSWD of concordance+equivalence equal to 1.5.

CHA-15-49 Eleven analyses were performed on 9 grains. Zircon from this sample are almost always homogeneous and very few cores can be observed. The proportion of grains with high aspect ratios (>5) is higher than in other samples. Three measurements display very high estimated Pb c contents (>7%) and are markedly discordant. They will not be considered further. Four analyses gave concordant 206 Pb/ 238 U dates: 776 ± 10 Ma (core, a453), 815 ± 9 Ma (homogeneous grain, a457), 360 ± 5 Ma (homogeneous grain, a444) and 305 ± 4 Ma (homogeneous grain, a434). The four remaining spots yielded discordant results. Two rims have 206 Pb/ 238 U dates of c. 600 Ma, one core a 206 Pb/ 238 U date of c. 500 Ma and a homogeneous grain a 207 Pb/ 206 Pb date of 1934 ± 8 Ma.

CHA-15-41 Forty-two spots were drilled on 34 zircon grains. Most grains are core-free and display narrow oscillatory zoning patterns in CL but some have broader alternating bands (up to 10 µm large). Few grains with clear core-rim relationships are also present in the investigated collection. Five analyses have high Pb c contents (>1.4%) and will not be considered further. One measurement performed on a core-free zircon yielded a concordant 206 Pb/ 238 U date of 1008 ± 13 Ma (a48). Seventeen spots drilled on zircon rims, cores and core-free crystals show low to moderate amounts of Pb c (mostly <0.6% but sometimes up to 1.1%) and are discordant (concordance <94%). Their 207 Pb/ 206 Pb dates range from 484 ± 76 Ma (a29) to 850 ± 37 Ma (a17). Thirteen measurements on zircon rims and core-free grains display concordant 206 Pb/ 238 U dates between 542 ± 7 Ma (a45) and 652 ± 10 Ma (a40). One spot on a homogeneous grain (a25) gives a younger concordant 206 Pb/ 238 U date of 429 ± 7 Ma. Five analyses yielded 206 Pb/ 238 U dates of c. 300 Ma and a Pb c correction was applied to 4 of them. The ve are statistically equivalent and a Concordia date of 304.0 ± 3.9 Ma can be calculated (MSWD C+E =1.4).

CHA-15-25 Twenty analyses were conducted on 17 grains, all but one from the rst population at GUF. Forty-two spots were drilled at ETH on 32 grains. Both datasets will be described concomitantly (see discussion on their equivalence in the introductory section). Spot names will be referred to as faXX and zaYY for those performed at GUF and ETH, respectively. Twenty-nine measurements are highly discordant (concordance <58%) and will not be discussed further. Fourteen spots yielded concordant 206 Pb/ 238 U dates ranging from 592 ± 5 Ma (za27) down to 520 ± 6 Ma (fa412). Seventeen analyses gave similar yet discordant 206 Pb/ 238 U dates, from 563 ± 3 Ma (za42) down to 514 ± 4 Ma (za36). Finally, one measurement performed on a zircon core yielded an older concordant 206 Pb/ 238 U date of 910 ± 10 Ma (fa422).

CHA-15-19 Twenty-two analyses were performed on 22 grains. They all display characteristic oscillatory zoning on CL images and are almost always devoid of inherited cores. Nine spots revealed substantial amounts of Pb c (>1%) in the zircon structure and will not be described and interpreted further. Seven analyses performed on homogeneous zircon and zircon rims with low Pb c contents (<0.7%) are discordant (concordance: 54 93%). Five have 206 Pb/ 238 U dates ranging from 321 ± 5 (a406) down to 256 ± 5 Ma (a408) and 207 Pb/ 206 Pb dates ranging from 540 ± 65 (a412) down to 365 ± 33 Ma (a421). One spot drilled on zircon rim (a411) yielded a 207 Pb/ 206 Pb date of 559 ± 15 Ma and another one (a415) an older 207 Pb/ 206 Pb date of 598 ± 23 Ma. Amongst the concordant spots, analysis a403 show a 206 Pb/ 238 U date of 316 ± 4 Ma. The ve remaining are statistically equivalent and allow the calculation of a Concordia date of 305.3 ± 3.9 Ma (MSWD C+E =0.6).

CHA-15-33 Fifty-three analyses were conducted on 44 grains. Zircon are notably small in this sample (often <100 µm in length). Oscillatory zoning was almost always observed together with frequent corerim relationships. Twelve analyses are markedly discordant, show elevated Pb c contents (often >3%) and will not be discussed further.

Twelve measurements performed on homogeneous grains, rims and cores gave concordant 206 Pb/ 238 U dates ranging from 621 ± 7 (a317) down to 476 ± 5 Ma (a351) with a cluster at c. 540 Ma. One spot yielded an older concordant 206 Pb/ 238 U date of 968 ± 11 Ma. Twenty analyses are discordant (concordance: 5293%) and show a wide range of 206 Pb/ 238 U dates between 733 ± 8 (a366) and 345 ± 4 Ma (a393). Six common lead corrected analyses, performed on 5 zircon rims and a homogeneous grain are statistically equivalent and a Concordia date of 302.2 ± 3.7 Ma (MSWD C+E =1.6) can be calculated out of them. Two spots also performed on zircon rims yielded younger 206 Pb/ 238 U dates of 293 ± 4 (a327) and 276 ± 4 Ma (a382) but are both discordant, even after the Pc c correction applied to spot a327.

CHA-15-34 Thirty-eight spots were drilled on 28 grains. Spot a110 (core-free grain) revealed very high Pb c contents (>3.1%) and will not be considered further. Seven analyses show moderate to elevated concentrations in Pb c (from 0.7 to 1.4%) and are all discordant with 207 Pb/ 206 Pb dates ranging from 961 ± 48 Ma (a91) to 578 ± 37 Ma (a127) and 206 Pb/ 238 U dates from 392 ± 6 Ma (a109) to 531 ± 7 Ma (a98). One analysis of a zircon rim (a130) is slightly discordant (concordance = 93%) and has a 207 Pb/ 206 Pb date of 1948 ± 7 Ma. Measurements performed on zircon core a100 yielded a subconcordant 206 Pb/ 238 U date of 778 ± 11 Ma. Spot a120 is discordant (concordance = 84%) and has a 207 Pb/ 206 Pb date of 964 ± 18 Ma.

CHA-15-51 Thirty-four spots were drilled on 26 grains. All zircon grains display oscillatory zoning and some corerim relationships have been observed. Fifteen measurements yielded discordant 206 Pb/ 238 U dates (concordance: 773%), feature moderate to very high common Pb contents (from 0.3 up to 20%) and will not be discussed further.

Eight analyses performed on homogeneous grains, a core and a rim are concordant and show 206 Pb/ 238 U dates ranging from 570 ± 6 (a273) down to 524 ± 7 Ma (a275). Seven measurements gave discordant (concordance: 7792%) 206 Pb/ 238 U dates in the same range from 550 ± 7 Ma (a302) down to 508 ± 6 Ma (a308). One spot performed on a zircon core (a296) is discordant, shows an older 206 Pb/ 238 U date of 651 ± 7 Ma and a 207 Pb/ 206 Pb date of 791 ± 26 Ma.

BOR-16-01 Forty-six spots were drilled on cores, rims and homogeneous grains. Ten analyses are markedly discordant (concordance < 44%) and will not be considered further.

Twelve concordant measurements yielded 206 Pb/ 238 U dates identical within error and a statistically acceptable Concordia date of 309.7 ± 3.6 Ma can be calculated out of them (MSWD C+E =1.09). Nine additional measurements show similar yet discordant 206 Pb/ 238 U dates and dene a trend between common and radiogenic Pb compositions. This trend intercepts the Concordia curve at 309.5 ± 3.6 Ma. Seven analyses yielded older concordant 206 Pb/ 238 U dates ranging from 549 ± 6 Ma down to 316 ± 2 Ma. One spot gave a younger concordant 206 Pb/ 238 U date of 297 ± 2 Ma. The rest of the data is discordant.

ROC-16-01 Thirty-eight measurements are notably discordant (concordance < 37%) and will not be further commented on. Three concordant spots performed on cores show Proterozoic 206 Pb/ 238 U dates ranging from 877 ± 6 Ma to 643 ± 9 Ma. One grain domain has a discordant 207 Pb/ 206 Pb date of 3437 ± 90 Ma. Twenty-three measurements trend along a mixing line between radiogenic and common Pb composition, with a lower intercept at 320.3 ± 3.7 Ma. Considering only the concordant analyses belonging to the trend, a Concordia date of 319.8 ± 3.8 Ma (MSWD C+E =1.5) can be calculated. Two measurements yielded younger 206 Pb/ 238 U dates of 312 ± 2 (a8) and 304 ± 2 Ma (a71), respectively. The rest of the data is discordant.

Migmatites

CHA-15-43 (in-source leucosome) Out of the 27 analyses, 3 are highly discordant (concordance <20%) and will not be examined further. Eleven measurements performed on core-free grains and zircon rims yielded discordant 206 Pb/ 238 U dates ranging from 555 ± 8 (a259) down to 406 ± 4 Ma (a232). The 13 remaining spots showed concordant results.

CHA-15-63 A total of 30 analyses were conducted on 28 zircons. Most of the zircons do not show core-rim relationships. Thirteen spots have elevated Pb c contents (from 1.5 to 11.2%) and notably discordant dates (mostly between 15 and 60% concordance), they won't be considered further. So will the overconcordant spot a279 be. Eight analyses performed on zircon rims and core-free grains showed low to moderate Pb c contents (<0.7%) and yielded discordant 207 Pb/ 206 Pb dates (concordance <94%) ranging from 768 ± 70 Ma (a309) to 567 ± 15 Ma (a310). One spot has a younger 207 Pb/ 206 Pb date of 538 ± 32 Ma. Core-free grains, cores and rims all gave 206 Pb/ 238 U dates between 590 ± 7 (a266) and 535 ± 6 Ma (a243) with a clear cluster in the period 550540 Ma.

CHA-15-47 Twenty-ve spots were drilled on 23 zircons grains. Zircons usually show core-rim relationships (most often dark cores surrounded by righter rims) buts some grains are core-free. Nine analyzed zircon domains contained substantial amount of Pbc (>1.2%, up to 24%) and won't be described further. Six analyses of zircon rims and core-free zircons are discordant (60% < concordance < 92%) and have low Pb c contents (below detection limit to 0.4%). 207 Pb/ 206 Pb dates show two clusters: (i) between 572 ± 16 Ma (a457) and 599 ± 23 Ma (a483); (ii) between 759 ± 41 Ma (a479) and 769 ± 42 Ma (a470). Two spots yielded concordant 206 Pb/ 238 U dates of 561 ± 8 Ma (rim a461) and 575 ± 8 Ma (spot a475, core-free zircon). Ten Concordant spots yielded 206 Pb/ 238 U dates clustering between 575 ± 8 (a475) and 540 ± 8 Ma (a458).

CHA-15-48 Sixty-six analyses were performed on 56 zircon grains. Twenty-four measurements performed on zircons with our without core-rim relationships yielded 206 Pb/ 238 U dates between 589 ± 8 Ma and 415 ± 8 Ma but revealed signicant amounts of common Pb (> 0.6%) resulting in a marked discordance (concordance < 68%). Only the 13 analyses with less than 2% Pb c will be further considered together with the 42 ones with Pb c < 0.6%. Two zircon cores have discordant late Archean to early Paleoproterozoic 207 Pb/ 206 Pb dates of respectively 2519 ± 6 Ma (a248) and 2437 ± 29 Ma (a223). One spot (a219) yielded a discordant 207 Pb/ 206 Pb date of 1973 ± 16 Ma. Four spots performed on zircon cores devoid of common Pb yielded concordant to sub-concordant 206 Pb/ 238 U dates between 623 ± 9 Ma (a227) and 575 ± 9 Ma (a274). Five analyses conducted on core-free zircons and zircon rims yielded concordant 238U/206Pb dates ranging from 559 ± 9 Ma (a214) to 574 ± 8 Ma (a218). Twenty-ve measurements performed on cores, rims or core-free grains are discordant (concordance <93%). Among them, 12 have low Pb c contents (<0.5%), show concordance between 75% and 93% and 207 Pb/ 206 Pb dates between 559 ± 18 Ma (a265) and 657 ± 27 Ma (a235). The 13 remaining have Pbc >0.5% with concordance mostly between 55% and 68% and older 207 Pb/ 206 Pb dates.

Eighteen analyses yielded concordant 206 Pb/ 238 U dates ranging from 551 ± 7 Ma (a276) to 518 ± 8 Ma (a224).

CHA-15-17 Twenty-one spots were drilled on 21 grains, only on zircon rims and corefree crystals apart from spot a423 which corresponds to a core. Five analyses bear substantial amounts of Pb c (>1.1%) and will not be further discussed. Eleven analyses are discordant (concordance: 76 to 93%), show subordinate to moderate amounts of Pb c (below detection limit to 0.9%) out of which 10 206 Pb/ 238 U dates between 548 ± 8 Ma (a429) and 510 ± 7 Ma (a432) and 207 Pb/ 206 Pb dates ranging from 569 ± 20 Ma (a424) to 693 ± 19 Ma (a450). Spot a452 has younger 206 Pb/ 238 U and 207 Pb/ 206 Pb dates of respectively 332 ± 5 Ma and 432 ± 31 Ma. Four core-free crystals have identical concordant 206 Pb/ 238 U dates of 539538 ± 78 Ma. One zircon core yielded an older date of 562 ± 9 Ma (a423).

CHA-15-65L Twenty-rst spots were drilled on 18 zircons grains. Not a single concordant measurement was obtained for this sample. All zircon domains showed very high common Pb content and are highly discordant (concordance <23%). The 3 least discordant analyses (conc.: 6793%) have 206 Pb/ 238 U dates between 547 ± 8 (a388) and 511 ± 9 Ma (a374).

CHA-15-65M A total of 85 measurements were performed, out of which 33 were markedly discordant and not considered further.

Two zircon cores have discordant

B.3.5 Data tables

In the following are reported the measurements of zircon standards for each session: The analytical procedure is exactly the same as followed by [START_REF] Couzinié | Cadomian S-type granites as basement rocks of the Variscan belt (Massif Central, France): Implications for the crustal evolution of the north Gondwana margin[END_REF] and the reader is referred to section A.3.

B.4.2 Analytical details on the LMV session

The procedure followed in the course of this analytical session has been published in [START_REF] Moyen | Paleoproterozoic rejuvenation and replacement of Archaean lithosphere: Evidence from zircon UPb dating and Hf isotopes in crustal xenoliths at Udachnaya, Siberian craton[END_REF]. Hafnium isotope measurements were performed with a Thermo Scientic Neptune Plus multi-collector ICPMS coupled to the Resonetics M50E 193nm laser excimer system. The MCICPMS is equipped with 9 Faraday cups and ampliers with 10

11 Ω. Data were collected in static mode ( 171 Yb, 173 Yb, 174 Hf, 175 Lu, 176 Hf-Yb-Lu, 177Hf , 178Hf , 179Hf ). The overall operating conditions and instrument settings are reported in Table B12. Each LAMCICPMS analysis consisted of 20 s of gas background data followed by 40 s of ablation. With an integration time of 1 s, each analysis typically produced 36-40 isotopic ratios. Mass bias eects on Hf were corrected using an exponential law and a true value for 179 Hf/ 177 Hf of 0.7325 [START_REF] Patchett | LuHf total-rock isochron for the eucrite meteorites[END_REF][START_REF] Patchett | Evolution of the continental crust and mantle heterogeneity: evidence from Hf isotopes[END_REF]. Data were reduced in the following order and based upon user-selected background and sample integration intervals. Firstly, the mean signal intensity of the 20-second gas background was subtracted from the signal acquired during the laser ring onto the sample. These corrected signal intensities were taken further during data reduction. β Y b was determined using the 173 Yb/ 171 Yb measured during each zircon analysis and the ref 173 Yb/ 171 Yb of 1.132685 [START_REF] Chu | Hf isotope ratio analysis using multi-collector inductively coupled plasma mass spectrometry: an evaluation of isobaric interference corrections[END_REF][START_REF] Fischer | Synthetic zircon doped with hafnium and rare earth elements: A reference material for in situ hafnium isotope analysis[END_REF], following the equation : The 176 Yb isobaric interference on 176 Hf was then determined using 176 Yb/ 173 Yb of 0.79618 and the 176 Lu isobaric interference on 176 Hf was determined using the measured interference-free 175 Lu mass assuming that β Lu = β Y b , and using the ref 176Lu / 175Lu of 0.02655 [START_REF] Vervoort | Isotopic composition of Yb and the determination of Lu concentrations and Lu/Hf by isotope dilution using MC-ICPMS[END_REF] The 176 Hf/ 177 Hf for all samples were corrected for mass bias using β Hf . Outlier rejection of the Hf isotopic ratio for each analysis were performed using a two-standard deviation criterion. Hf/ 177 Hf = 0.282785 (Bouvier et al ., 2008).

( UPb isotopic data were obtained using the laser ablation inductively coupled plasma mass spectrometry (LAICPMS) unit maintained at the Laboratoire Magmas and Volcans, Clermont-Ferrand, France, from monazite grains separated from rock powders as well as grains identied in standard petrographic thin sections. The analyses involved ablation with a Resonetics M-50 Excimer laser system operating at a wavelength of 193 nm [START_REF] Müller | Initial performance metrics of a new customdesigned ArF excimer LA-ICPMS system coupled to a two-volume laser-ablation cell[END_REF]. Spot diameter of 9 µm was associated with repetition rates of 3 Hz and a uence of 2.9 J/cm -2 . The ablated material was carried into helium and then mixed with nitrogen and argon before injection into the plasma source of a Thermo

Element XR Sector Field high-resolution ICPMS. The analytical method for isotope dating with LA-ICPMS is similar to that reported in [START_REF] Paquette | [END_REF]Tiepolo (2007), Hurai et al. (2010) and Paquette et al. (2014). Data are corrected for the UPb fractionation occurring during laser sampling and for instrumental mass bias by standard bracketing with repeated measurements of the Trebilcock monazite [START_REF] Tomascak | U-Pb monazite geochronology of granitic rocks from Maine: Implications for late Paleozoic tectonics in the Northern Appalachian[END_REF][START_REF] Kohn | U-Th-Pb dating of monazite by single-collector ICP-MS: Pitfalls and potential[END_REF]. Reproducibility and age uncertainty of reference material are propagated by quadratic addition (Horstwood et al., 2003). Repeated analyses of the Itambé monazite treated as unknowns independently controlled the reproducibility and accuracy of corrections. Data reduction was carried out using the GLITTER ® software package from Macquarie Research Ltd. (Van Achterbergh et al., 2001;Jackson et al., 2004).

Calculated ratios were exported and concordia ages and diagrams were generated using Isoplot/Ex v. 4.15 software package for MS Excel ® (Ludwig, 2008). UThPb concen- trations were calibrated relative to the certied contents of these elements in the Itambé monazite (Gasquet et al., 2010). The methodology is summarized Table B15.

Results of LAICPMS

Uncertainty level & propagation

Ages are quoted at 2σ absolute, propagation is by quadratic addition according to Horstwood et al. (2003)

Figure 1

 1 Figure 1.1: Sketch column diagram showing the structure, composition and seismic properties of standard continental crust. Temperatures prevailing at dierent crustal levels are those calculated by[START_REF] Chapman | Thermal gradients in the continental crust[END_REF]. The "Upper Crust" gathers both the upper and middle crusts described in text. Figure from[START_REF] Wedepohl | The composition of the continental crust[END_REF].

Figure 1 . 4 :

 14 Figure 1.4: Selected crustal growth curves obtained by step-wise integration of the volume of new crust formed and preserved at each time period. Curves based on zircon UPb data from Rino et al. (2004) and Condie and Aster (2010), on Hf model ages from Belousova et al. (2010) and Dhuime et al. (2012), on the age of present-day continental areas from[START_REF] Hurley | Pre-drift continental nuclei[END_REF]. Are also depicted the main periods of supercontinent amalgamation (fromCampbell and Allen, 2008). Figure inspired from[START_REF] Roberts | The zircon archive of continent formation through time[END_REF].

Figure 1 . 5 :

 15 Figure 1.5: Supercontinent ages compared to the distribution of UPb ages of c. 8,000 concordant detrital zircon grains from 40 majors rivers, Australian dunes and Antarctic Paleozoic sediments.Figure from Campbell and Allen (2008).

Figure 1 . 7 :

 17 Figure 1.7: Simplied plate tectonic sketch showing the absolute motions of continental and oceanic plates (only the crustal parts are displayed) from the Ordovician to the Carboniferous. The closure of the Iapetus ocean ended up in the Caledonian orogeny, that of the Rheic and GaliciaMassif Central in the Variscan orogeny ("Variscides"). Abbreviations: ARMOR, Armorica; AVALON, Avalonia; NFL, Newfoundland; GSB, GaliciaMassif Central ocean. Figure from Matte (2001).

Figure 1 . 8 :

 18 Figure 1.8: Simplied cross-sections at crustal scale through the Variscan belt in France, without granites. Grey, pre-Paleozoic (essentially Upper Proterozoic) low-grade basement; white, Lower Paleozoic sediments; black, ophiolitic nappes and sutures; dots, Carboniferous foredeeps; Bray SZ, NASZ and SASZ: Bray, North Armorican and South Armorican dextral shear zones; VF, Variscan Front. Figure and legend from Matte (2001).

Figure 1 .

 1 Figure 1.12: Simplied sketch showing the general metamorphic grade and structural relationships between the mains nappes in three domains of the French Massif Central. A selection of critical geochronological constraints are also depicted. NW FMC: Limousin, Sioule; SW FMC: Truyère, Lot, Marvejols, Rouergue, Albigeois, Montagne Noire (M.N.); E FMC: Brévenne, Lyonnais, Haut Allier, Vivarais, Velay, Cévennes; names of the geological regions after Ledru et al. (1989). UAU: Upper Allochtonous Units. UGU: the Upper Gneiss Unit. LGU: the Lower Gneiss Unit. PAU: Parautochtonous Unit. References and techniques for ages, mineral abbreviations from Whitney and Evans (2009): (a) Costa (1989), bt ArAr; (b) Pin and Lancelot (1982), zrc UPb IDTIMS; (c) Paquette et al. (1995) whole-rock/minerals SmNd; (d) Legendre et al. (2009), mnz UThPb EPMA; (e) Caron (1994), btmsamp ArAr; (f) Bouilhol et al. (2006), ms ArAr (f1), mnz UThPb EPMA (f2); (g) Caen-Vachette et al. (1984), whole-rock RbSr; (h) Malavielle et al. (1990) bt ArAr; (i) Costa (1990), ms ArAr; (j) Doublier et al. (2006) ms ArAr; (k) Ducrot et al. (1983) zrc UPb IDTIMS; (l) Duthou et al. (1994), whole-rock RbSr; (m) Maluski and Monié (1988), bt ArAr; (n) Poilvet et al. (2011), zrc UPb LAICPMS; (p) Faure et al. (2010) recalculated by Roger et al. (2015), zrc UPb SIMS; (q) Berger et al. (2010a); zrc UPb LAICPMS; (r) Schulz (2009), mnz UThPb EPMA; (s) Schulz (2014), mnz UTh Pb EPMA; (t) Couzinié et al. (2014), mnz UThPb EPMA; (u) Gébelin et al. (2009), mnz UPb IDTIMS.

  Fig. 2

  Fig. 2. Geological map of the Velay dome area. The extent of Variscan partial melting of the metamorphic lithologies is not shown for sake of clarity. Redrawn after Ledru et al. (2001) and regional geological maps of France at scale 1/50000. Literature geochronological data: 1, 528 ± 9 Ma, Rb-Sr whole-rock (R'Kha Chaham et al., 1990); 2, 543 ± 25 Ma, U-Th-Pb monazite (Be Mezeme et al., 2006); 3, 533 ± 23 Ma, zircon Pb evaporation(Mougeot et al., 1997); 4, 545 ± 14 Ma, Rb-Sr whole-rock (Caen-Vachette, 1979).

Fig. 3 .

 3 Fig. 3. Schematic diagram showing the field relationships and ages of the main lithological components within the two high-grade units (Upper and Lower Gneiss Units) of the eastern French Massif Central. See text for discussion.

Fig. 4 .

 4 Fig. 4. Outcrop photographs showing: (a) a typical biotite + muscovite augen gneiss (dated sample MM06), St Privat-d'Allier; (b) a leucogneiss boudin (dated sample MM09) elongated within the augen gneiss facies, D906 Langogne; (c) sharp contact between the two facies underlined by a biotite-rich layer, D906 Langogne; (d) 10 cm-thick laminated layers of mylonitic augen gneiss embedded within strongly deformed leucogneiss, contact is intricate and gradational, Pont-du-Bon-Dieu, Labastide-Puylaurent.

Fig. 6 .

 6 Fig. 6. Major elements compositions of samples from the Velay Orthogneiss Formation: (a) Na 2 O + K 2 O vs. SiO 2 Middlemost's classification diagram(Middlemost, 1994); (b) A/CNK vs. A/NK Shand's diagram[START_REF] Shand | Eruptive Rocks[END_REF]; (c) Mg# vs. SiO 2 . All diagrams were plotted using the GCDkit software[START_REF] Janoušek | Interpretation of whole-rock geochemical data in igneous geochemistry: introducing geochemical data toolkit (GCDkit)[END_REF]; (d) Results of linear discrimination analysis (LDA). More than 80% of the data are indistinguishable from one another. Data for Variscan S-type granites are fromMoyen et al. (2017).

Fig. 7 .

 7 Fig. 7. Average trace-elements compositions of rocks from the Velay Orthogneiss Formation: (a) Rare Earth Elements patterns normalized to the chondrite (Boynton, 1984); (b) Coryell-Masuda diagram normalized to the Primitive Mantle (McDonough and Sun, 1995). Same legend as Fig. 4. The shaded areas correspond to 1 S.D. (standard deviation).

Fig. 8 .

 8 Fig. 8. Tera-Wasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) showing zircon data from the Velay Orthogneiss Formation samples investigated in this study. Error ellipses and ages are displayed/quoted at 2σ level of uncertainty. Yellowish ellipses are those included in age calculations.

Fig. 9 .

 9 Fig. 9. (a) Measured εHf(t) on magmatic zircon grains and rims from the two investigated samples of augen gneisses of the Velay Orthogneiss Formation (VOF). (b) Zircon εHf(t) vs. age diagram for the two VOF samples and a compilation of data from detrital zircon in regional Ediacaran metasediments (n = 371), regarded as the potential source of the peraluminous magmas from which the VOF protoliths derive. Data from the French Massif Central (Chelle-Michou et al., 2017), the Bohemian Massif (Linnemann et al., 2014) and the Iberian Massif (Orejana et al., 2015; Teixeira et al., 2011). The εHf(t) range for the depleted mantle reservoir is bracketed by the models of Naeraa et al. (2012) (lowermost value) and Griffin et al. (2002) (uppermost value).

Fig. 11 .

 11 Fig. 11. Comparison between VOF samples and experimental melt compositions for a range of crustal sources (seeTable 2). Experimental data are projected on the principal component framework. Same legend as Fig.4.

Fig. 12 .

 12 Fig. 12. (a) and (b) Major element compositions of fractionated melts. Each arrow shows the composition of a centroid melt (P.Comp 1 = 0) after 10% fractionation of the mentioned mineral phase. The melt composition in case of a poly-mineral fractionating assemblage can be graphically estimated by a linear combination of each vector. Generic mineral compositions are from[START_REF] Stevens | Selective peritectic garnet entrainment as the origin of geochemical diversity in S-type granites[END_REF]. (c) and (d) Trace element compositions of fractionated melts. Each arrow depicts the composition of the melt after 20% (except mentioned value) fractionation of the mineral phase. The list of considered partition coefficients is available as Supp. Material (TableS8). Same legend as Fig.4. Larger symbols correspond to dated samples.

Fig. 13 .

 13 Fig. 13. Comparison of leucogneisses corrected normative compositions and experimental data on the H 2 O-saturated Qz -Ab -Or system at different pressures (numbers in kbars).Minima/eutectics (black squares) as compiled by[START_REF] Blundy | Ascent-driven crystallisation of dacite magmas at Mount St Helens, 1980-1986[END_REF]. Shift of minima/eutectic positions with decreasing water activity fromJohannes and Holtz (1996).

Fig. 14 .

 14 Fig. 14. Compilation of available intrusion ages for pre-Variscan volcanic and plutonic rocks in the French Massif Central. (a) Age distribution represented as Kernel Density Estimate, calculated using the DensityPlotter program of Vermeesch (2012); the bandwidth considered is the average 2σ error on emplacement ages (12 Ma). (b) Details on available intrusion ages. Abbreviations and references available in Supplementary text.

  Fig. 15. Geochemical comparison between Cadomian granitoids from the Mancellian domain and the VOF (N95% of the samples in the gray field). (a) Na 2 O + K 2 O vs. SiO 2 Middlemost's classification diagram(Middlemost, 1994); (b) ternary CaO -K 2 O/Na 2 O -Al 2 O 3 /(FeO t + MgO) diagram(Laurent et al., 2014). The fields represent the composition of melts derived from a range of potential sources. MME: mafic microgranular enclaves.

Figure 2 . 1 :

 21 Figure 2.1: Geological map of the Velay dome area showing the location of analysed metasediment and amphibolite samples. The extent of Variscan partial melting of the metamorphic lithologies is not shown for sake of clarity. Redrawn after Ledru et al. (2001), Mintrone (2016) and regional geological maps of France at scale 1/50,000.

Figure 2 . 2 :

 22 Figure 2.2: Cross-(a,b,d) and plane-polarized-light (c) photomicrographs of metasediments out of which detrital zircon grains were extracted to determine their UPbHf isotope compositions. (a) Pilat quartzite PIL-16-01; (b) Senouire quartzite SEN-16-01; (c) Cévennes meta-arkose CHA-16-02; (d) Pont-de-Bayzan paragneiss PdB-16-01. Mineral abbreviations from Whitney and Evans (2009).

Figure 2 .

 2 Figure 2.3: Representative cathodoluminescence images of zircon grains from Lower Gneiss Unit metasediments. The locations of laser spots (white and yellow circles for UPb and LuHf analyses respectively) are indicated along with the spot name (zXX or #YY). The corresponding 206 Pb/ 238 U dates are quoted with ± 2σ uncertainty, in Ma. All displayed analyses are concordant at > 95%. Hf isotope data are reported using the ε Hf calculated at the 206 Pb/ 238 U date obtained on the same zircon domain, quoted with 2σ uncertainty.

Figure 2 . 4 :

 24 Figure 2.4: TeraWasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) showing Neoproterozoic zircon data for the Lower Gneiss Unit metasediments. Error ellipses/ages are quoted at 2σ level of uncertainty. Yellowish ellipses are those included in age calculations.

Figure 2 .

 2 Figure 2.5: Zircon UPb date distribution of investigated metasediments from the Lower Gneiss Unit represented as Kernel Density Estimates (KDE). Only 95105% concordant 206 Pb/ 238 U (for dates < 1.2 Ga) and 207 Pb/ 206 Pb dates (for dates > 1.2 Ga) were considered. Circles below the x-axis are the central value of individual data points. Plotted with the DensityPlotter program of Vermeesch (2012). The bandwidth was set to adaptative mode for the 4003100 Ma diagram and 12 Ma (the average 2σ error of individual analyses) for the 5001100 Ma plot.

Fig

  Fig 2.6.

  -16-01 Zircon with UPb dates in the range 590980 Ma have dominantly very radiogenic Hf isotope signatures: 84% of the data yield ε Hf (t) > +4.4, 47% Depleted Mantle-like values (up to +13.7, #41). Besides, 8% are nearly chondritic (between -1.8 and 1.2, #21 and #19 respectively) and the remaining 8% subchondritic (between -12.1 and -18.7, #8 and #31, respectively). Paleoproterozoic zircon grains show slightly non-radiogenic signature (of c. -2 ε-unit). Two Neoarchean zircon yielded sub and suprachondritic values of -5.6 (#22) and +2.6 (#42). General pattern The ε Hf (t) measured on Paleoproterozoic and Neoarchean zircon are scattered and both sub and suprachondritic. Detrital zircon crystallized at the Tonian Stenian boundary have even more diverse signatures with ε Hf (t) ranging from -19 up to +11 (in the eld of composition expected for the Depleted Mantle reservoir). A large majority of CryogenianTonian zircons (mostly represented by sample Pdb-16-01) have radiogenic Hf isotope signatures. Ediacaran zircon grains are typied by their highly variable ε Hf (t), from -16.9 to +12.2. This pattern diers from that observed by Chelle-Michou et al. (2017) in LGU metasediments from the eastern Velay for two reasons: (i) their measured CryogenianTonian zircons tend to show subchondritic signatures, and(ii) the EdiacaranCryogenian highly radiogenic record (ε Hf (t)>+6) documented in this study is lacking in theirs.

Figure 2 .

 2 Figure 2.6: Combined U-Pb and Lu-Hf isotopic data for zircons from Ediacaran metasediments, constituent rocks of the Lower Gneiss Unit in the Velay area. Additional data for the eastern Velay are from Chelle-Michou et al. (2017). The yellow eld depicts the composition of intruding meta-granites from the Velay Orthogneiss Formation (see above). The ε Hf (t) range for the Depleted Mantle reservoir is bracketed by the models ofNaeraa et al. (2012) and[START_REF] Grin | Zircon chemistry and magma mixing, SE China: In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes[END_REF]. The dotted arrow represent the isotopic evolution of continental crust (calculated using an average crustal 176 Lu/ 177 Hf ratio of 0.0113). Data for the northern Armorican Massif are from D'Lemos andBrown (1993);[START_REF] Samson | UPb geochronology and SmNd isotopic composition of Proterozoic gneisses, Channel Islands, UK[END_REF] and[START_REF] Samson | UPb geochronology and HfNd isotope compositions of the oldest Neoproterozoic crust within the Cadomian orogen: new evidence for a unique juvenile terrane[END_REF].

Figure 2 . 8 :

 28 Figure 2.8: Composition of the Lower Gneiss Unit metabasites plotted in the R 1 R 2 diagram of De La Roche et al. (1980). The fractionation trends for each series are from Debon and Lemmet (1999).

Figure 2 . 9 :

 29 Figure 2.9: Incompatible, immobile element patterns normalized to the composition of N-MORBs (Sun and McDonough, 1989) for the metabasites of the Lower Gneiss Unit. The grey eld depicts the composition of samples from the litterature.

Figure 2 .

 2 Figure 2.10: Proxy element diagrams for metabasites from the Lower Gneiss Unit. (a) ThNb proxy diagram of Pearce (2008). Oceanic basalts plot within the MORBOIB array. Magmas contaminated by the continental crust during ascent or which mantle source interacted with slab-derived uids plot in the volcanic arc array. (b) TiNb proxy diagram of Pearce (2008).The TiO 2 /Yb ratio strongly depends on the presence of residual garnet in the mantle source. Magmas formed at great depth feature high TiO 2 /Yb ratio provided that garnet is not exhausted in the residua. Such samples plot in the OIB array. If the magmas result from melting of spinel peridotites, or if garnet has been exhausted in the residua, they plot in the MORB array. Same legend as Fig.2.8

Figure 2 .

 2 Figure 2.11: Representative cathodoluminescence images of zircon grains from amphibolite sample MM03. The locations of laser spots are indicated along with the spot name (aXX and cYY for measurements performed in the rst and third sequence, respectively). The corresponding 206 Pb/ 238 U dates are quoted with ± 2σ uncertainty, in Ma. All displayed analyses are concordant (except those in italic). Spot diameters are 20 and 30 µm.

  2.12b). Fourteen spots drilled on CL-dark cores, on rims displaying sector zoning and on mixed domains gave a range of discordant 206 Pb/ 238 U dates ranging from 475 ± 8 down to 347 ± 3 Ma (Fig.2.12a). One analysis performed on a CL-dark core yielded a concordant 206 Pb/ 238 U date of 496 ± 13 Ma (Fig.2.11 and 2.12a). Finally, one measurement conducted on an other CL-dark core gave a discordant 206 Pb/ 238 U date of 538 ± 10 Ma. Analyses with 206 Pb/ 238 U dates older than 320 Ma show elevated Th/U ratios (>0.48 and up to 2.5, see Fig.2.12b).

Figure 2 .

 2 Figure 2.12: (a): TeraWasserburg diagram ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) for zircon from the Vivarais amphibolite sample MM03. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellowish ellipses are those considered for Concordia age calculations. (b) 206 Pb/ 238 U date as a function of zircon Th/U ratio for each measurement showing concordance >63%.

Figure 2 .

 2 Figure 2.12b illustrates the existence of a trend between a set of spots with low Th/U (<0.11) and late Carboniferous 206 Pb/ 238 U date (<318 Ma), corresponding to (re)crystallized metamorphic zircon, and an endmember with high Th/U and Cambrian Ordovician 206 Pb/ 238 U dates. This observation suggests that the scattered 206 Pb/ 238 U ranging from 475 ± 8 down to 347 ± 3 Ma reects the sampling of mixed zircon domains comprising: (i) (re)crystallized metamorphic sectors and (ii) old zircon cores. From this perspective, the discordance displayed by most analyses would be a direct consequence of such mixing. Yet, mixing trends in the Tera-Wasserburg diagram (Fig. 2.12a) or in the 206 Pb/ 238 U date vs. Th/U plot (Fig. 2.12b) yield a non-unique solution. I interpret this feature as a consequence of common Pb incorporation, which is independently supported by the observation of healed micro-fractures in CL images. Consequently, the actual age of the zircon cores is most probably given by the single concordant 206 Pb/ 238 U date of 496 ± 13 Ma. Younger discordant dates would reect both core/rim mixed analyses and common Pb incorporation. The signicance of the discordant 206 Pb/ 238 U date of 538 ± 10 Ma remains unclear.

Figure 3

 3 Figure 3.1: Geological map of the Monts-du-Lyonnais area. Redrawn after the maps of Chiron[START_REF] Chiron | Notice explicative, Carte géol[END_REF],Dufour (1982) andFeybesse et al. (1995).

Figure 3 . 3 :

 33 Figure 3.3: Geochemical diagrams outlining the main characteristics of the meta-igneous lithologies from the Upper Gneiss Unit of the Monts-du-Lyonnais area. (a) Total Alkali vs. Silica (TAS) classication diagram (Middlemost, 1994); (b) Zr/Ti vs. Nb/Y classication diagram of Winchester and Floyd (1977) modied by Pearce (1996); (c) K 2 O vs. SiO 2 diagram of Pecerillo and Taylor (1976); (d) BA diagram of Debon and Le Fort (1983) modied by Villaseca et al. (1998); (e) normative feldspar classication diagram of O'Connor (1965).

  evolution. Following the conclusions drawn in Chapter 1, this crust segment originally consisted in a Ediacaran back-arc basin fed by detritus originating from a distal mature source (the Gondwana-land) and a proximal immature source (the Cadomian arc). I therefore propose that the LOF magmas formed by melting of a heterogeneous sedimentary sequence containing a signicant proportion of immature volcaniclastic sediments, in contrast to the VOF which source would encompass more mature detritus. This model accounts for all the dierences between the LOF and VOF and is besides supported by the spread in the LOF initial Sr isotope compositions which would attest to melting of a variety of source materials, from clasts of mantle-derived intermediate igneous rocks with low I Sr and high Sr contents to isotopically evolved and Sr-depleted distal sediments (Fig.3.4).

Figure 3 . 5 :

 35 Figure 3.5: Geochemical comparison between the Lyonnais Orthogneiss Formation (grey circles) and the Velay Orthogneiss Formation (VOF, red squares). (a) and (b): boxplots of the A/CNK and P 2 O 5 (in wt.%) values; (c) ternary CaOK 2 O/Na 2 OAl 2 O 3 /(FeO t +MgO) diagram(Laurent et al., 2014), the elds represent the composition of melts derived from a range of potential sources; (d) discrimination diagrams of[START_REF] Whalen | A-type granites: geochemical characteristics, discrimination and petrogenesis[END_REF]. A stands for A-type granites, OTG for ordinary-type granites (I-, S-and M-types) and FG for fractionated granites. The red eld depicts the compositional range of >95% of the VOF samples.

(

  1993) provided (a partial set of ) trace element analyses. Here, we present a new dataset including full trace element determinations. Five amphibolites were sampled by myself in the Riverie band and thirteen analyses from small bodies were kindly provided by Anne-Céline Ganzhorn, JeanFrançois Moyen and Véronique Gardien. Chemical analyses were performed by the ALS rm (see Appendix A.3).

  Figure 3.6: Incompatible, immobile element patterns normalized to the composition of N-MORBs(Sun and McDonough, 1989) for the metabasites of the Upper Gneiss Unit in the Monts-du-Lyonnais area. See text for a discussion on the dierences between each group. The blue elds depict the compositional range of LREE-enriched tholeiites (in a) and "transitional" alkali basalts (in c) identied by[START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF] and[START_REF] Ouali | Caractérisation géochimique des paléomagmatites de quelques unités lithotectoniques du Massif Central français : Implications géodynamiques[END_REF] among the small bodies. The red eld shows the compositional range of LREE-enriched tholeiites from the Riverie band[START_REF] Ouali | Caractérisation géochimique des paléomagmatites de quelques unités lithotectoniques du Massif Central français : Implications géodynamiques[END_REF][START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF]. Black line is the composition of the bulk continental crust(Rudnick and Gao, 2003).

  3.7a), they plot close to the OIB endmember. In the TiNb proxy diagram (Fig. 3.7b), they dene a trend between the MORB array and an OIB-like endmember with elevated TiO 2 /Yb ratio. Group IV Two samples (MG1 and MG4) are markedly dierent as they display at patterns, apart from a prominent Nb anomaly, and are strongly depleted in all incompatible elements compared to NMORBs. They plot in the volcanic arc array in the ThNb diagram and in the MORB array in the TiNb diagram (Fig. 3.7a and b). These two samples typically show low Ti/V ratios, close to 10 (Fig. 3.7c).

Figure 3 . 7 :

 37 Figure 3.7: Proxy element diagrams for metabasites from the Monts-du-Lyonnais area. (a) ThNb proxy diagram of Pearce (2008). Oceanic basalts plot within the MORBOIB array. Magmas contaminated by the continental crust during ascent or which mantle source interacted with slab-derived uids plot in the volcanic arc array. (b) TiNb proxy diagram of Pearce (2008).The TiO 2 /Yb ratio strongly depends on the presence of residual garnet in the mantle source. Magmas formed at great depth feature high TiO 2 /Yb ratio provided that garnet is not exhausted in the residua. Such samples plot in the OIB array. If the magmas result from melting of spinel peridotites, or if garnet has been exhausted in the residua, they plot in the MORB array. (c) V Ti proxy diagram of[START_REF] Shervais | TiV plots and the petrogenesis of modern and ophiolitic lavas[END_REF] applied to samples plotting in the volcanic arc array of the ThNb proxy diagram and assumed to have formed in an environment inuenced by subduction. This diagram is based on the change in V redox state when the mantle is uxed by slab-derived uids. V becomes more incompatible and resulting magmas have characteristic high V/Ti ratios. Lower V/Ti ratios would be symptomatic of a more distal position with respect to the slab. Bulk continental crust fromRudnick and Gao (2003).

3. 3 . 4

 34 Interpretation and origin of the metabasites Samples bearing a negative Nb anomaly: Group I and IV Origin of ThNb decoupling Those samples plot within the volcanic arc array in the Th-Nb proxy diagram (Fig. 3.7a). Nb being conservative and Th non conservative during subduction, selective addition of Th and LREE to the source of the magmas can account for their Th enrichment compared to MORBOIB basalts

Figure 3 . 8 :

 38 Figure 3.8: Outcrop photograph from Riverie showing the meta-tonalites and their embedded amphibolite boudins. Migmatitic neosomes appear as leucocratic patches (a) or a layered network cutting across the local foliation (b). Hammer for scale.

Figure 3 . 9 :

 39 Figure3.9: Mineral chemistry classication diagrams for (a) amphibole, with Ca B ≥ 1.50, (Na + K) A < 0.50 and Ca A < 0.50[START_REF] Leake | Nomenclature of amphiboles: report of the subcommitee on amphiboles of the International Mineralogical Association, Commission on new minerals and mineral names[END_REF], and (b) mica.

Figure 3 .

 3 Figure 3.10: (a) Photomicrograph showing the Pg + Qz + Amp + Mag assemblage of the amphibole-bearing gneiss RV-1. (b) SEM image highlighting the Ca + Chl + Rt products of amphibole alteration (sample RV-2).

Figure 3 .

 3 Figure 3.11: Representative cathodoluminescence images of zircon grains from samples of the Riverie meta-tonalites. The locations of laser spots (white and yellow circles for UPb and LuHf analyses respectively) are indicated along with the spot name (aXX or YYa/b). The corresponding 206 Pb/ 238 U dates are quoted with ± 2σ uncertainty, in Ma. All displayed analyses are concordant at >98% (except those in italic). Hf isotope data are reported using the ε Hf calculated at the 206 Pb/ 238 U date obtained on the same zircon domain, quoted with 2σ uncertainty.

Figure 3 .

 3 Figure 3.14: (a) Incompatible, immobile element patterns normalized to the composition of N-MORBs (Sun and McDonough, 1989) for the Riverie meta-tonalites and associated amphibolites. (bc) Geochemical models questioning the genetic link between meta-tonalites and amphibolites: (b) Results of forward batch crystallization models showing the virtual trace element composition of a tonalite melt dierentiated from a parental mac magma of MG0104 composition; (c) Results of reverse batch crystallization models yielding the trace element composition of the parental melt from which the tonalites would have been dierentiated.

Figure 4 . 2 :

 42 Figure 4.2: Summary of the lithological composition of each tectono-metamorphic unit recognized in the three largest and best studied exposures of the French Massif Central. Upper Allochtonous Units are not considered. See text and Fig. 4.1 for data sources and methodology.See introduction for a discussion on the overall architecture and the age of the contacts. The PAU of the Rouergue, Lot and Velay areas also includes the low-grade "Fold-and-Thrust Belt" and the Saint-Sernin-sur-Rance nappe ofFaure et al. (2009) and thus refers to all low-grade metamorphic units a similar structural position. The Limousin sketch is inspired fromMelleton et al. (2010).

Figure 4 . 3 :

 43 Figure 4.3: Comparison between the available intrusion ages for pre-Variscan igneous rocks represented as Kernel Density Estimates, calculated using the DensityPlotter program of Vermeesch (2012); optimal bandwidths were determined by the program (adaptive mode).

Figure 4 .

 4 Figure 4.4a shows that 1/4 of the data plot within the MORBOIB array and the remaining in the volcanic arc array. The compositions of samples from all massifs are evenly scattered apart for amphibolites from the Velay dome and a selection of samples from the Monts-du-Lyonnais area which characteristically plot in the MORBOIB array close to the OIB reservoir. As explained section 3.3, metabasites plotting in the volcanic arc eld were either contaminated by the continental crust during ascent/emplacement or originated from melting of a mantle that interacted with slab-derived uids. Samples plotting in the MORBOIB array show a wide range of Nb/Yb, indicative of contrasted melting degrees and/or variously enriched mantle sources. For instance, samples with high Nb/Yb would have formed by limited melting of a (potentially) enriched asthenospheric

Figure 4 .

 4 Figure 4.4d highlights that samples plotting in the MORBOIB array of gure 4.4a show radiogenic whole-rock ε N d (recalculated at 480 Ma) clustering around the value of +6.They will be referred to as subset A. Conversely, samples plotting in the volcanic arc array show a larger range of ε N d (t) from DM-like values of +9 down to slightly non-radiogenic values of -2.5. Two groups of samples can be identied. The rst group (subset B) displays ε N d (t) similar to that of the DM and to samples plotting in the MORBOIB array. The second group (subset C) gathers samples with ε N d (t) clustering around the chondritic value (± 3 ε units).

Figure 4 . 4 :

 44 Figure 4.4: (ac) Proxy element diagrams for metabasites from high-grade metamorphic units of the French Massif Central: (a) ThNb proxy diagram of Pearce (2008); (b) TiNb proxy diagram of Pearce (2008); (c) VTi proxy diagram of Shervais (1982) applied to samples plotting in the volcanic array in the ThNb proxy diagram and assumed to have formed in an environment inuenced by subduction. See caption of Fig. 3.7 for the interpretation of those proxies. (d) Whole-rock ε N d calculated at 480 Ma vs. Th/Nb ratio. The MORBOIB and volcanic array are bracketed by the values of[START_REF] Pearce | Geochemical ngerprinting of oceanic basalts with applications to ophiolite classication and the search for Archean oceanic crust[END_REF]. The isotopic composition of metasomatizing uids derived from the oceanic igneous crust is assumed to be close to that of the Depleted Mantle (value from[START_REF] Liew | Precambrian crustal components, plutonic associations, plate environment of the Hercynian Fold Belt of central Europe: Indications from a Nd and Sr isotopic study[END_REF]. Red curve: results of binary mixing model of a basaltic melt PB (Nd, Th and Nb contents set as average of N and EMORBs, fromSun and McDonough, 1989; ε N d (t) of +7) assimilating upper and lower continental crust (UCC and LCC, Nd, Th and Nb contents fromRudnick and Gao, 2003; ε N d (t) of -5, average of the FMC crust, fromTurpin et al., 1990;[START_REF] Simien | Nd isotopes in the stratigraphic record of the Montagne Noire (French Massif Central): No signicant Paleozoic juvenile inputs, and pre-Hercynian paleogeography[END_REF][START_REF] Downes | Isotopic and trace-element arguments for the lower-crustal origin of hercynien granitoids and pre-hercynian orthogneisses, Massif Central (France)[END_REF] Pin and Duthou, 1990 and Williamson et al., 1992). Blue curve: results of mass-balance, binary mixing models between the local mantle LM (ε N d (t)=+7, corresponding to that of the most radiogenic metabasite; Nd, Th and Nb contents fromWorkman and Hart, 2005) and (i) the GLOSS (Global Subducting Sediment,Plank and Langmuir, 1998), (ii) the LCC(Rudnick and Gao, 2003), both assumed to show an average ε N d (t) of -5 (see above). Percentages represent the proportion of UCC/LCC/GLOSS in the respective mixtures.

Figure 4

 4

Figure 4 . 5 : 2 :

 452 Figure 4.5: Interpretative geodynamic sketch illustrating the CambrianOrdovician evolution of the crust segment to which the French Massif Central belongs. See text for discussion.

Fig. 1 a

 1 Fig. 1 a Sketch map showing the repartition of exposed Variscan domains in Western Europe, as well as the salient structural features of the Variscan belt (MZ moldanubian zone, RHZ Rheno-Hercynian zone, STZ Saxo-Thuringian zone). b Geological map of the eastern

Fig. 2

 2 Fig. 2 Some geochemical characteristics of late-Variscan plutonic rocks in the eastern French Massif Central. The larger symbols correspond to samples investigated in the present study for which whole-rock geochemical data are available (unpublished data from S. Couzinié). a R 1 -R 2 plot of De la Roche et al. (1980) (1 = syenogabbro; 2 = monzogabbro; 3 = monzonite; 4 = monzodiorite;

Fig. 3

 3 Fig. 3 Representative cathodoluminescence images of zircon grains from samples of late-Variscan plutonics rocks investigated in this study: a cordierite-and muscovite-bearing peraluminous granites (CPG and MPG); b K-feldspar porphyritic calc-alkaline granites and granodiorites (KCG) and vaugnerites (V). The position of the laser spots used for U-Pb dating (circles) is also indicated, along with the spot name (aXXX) and the corresponding 238 U/ 206 Pb age (with ±2σ uncertainty, in Ma). Each zircon grain is labeled with the sample it

Fig. 6

 6 Fig. 6 Representative U-Pb Concordia diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U)showing examples of zircon analyses from samples of "group 3", i.e., showing several generations of zircon crystallization (core-rim relationships) and scattered 206 Pb/ 238 U dates with a Carboniferous upper intercept age, and a lower intercept at or close to zero within uncertainty. Insets in the bottom right represent the close-up to the analyses from zircon cores or xenocrysts ("Xen."), reported as shaded ellipses. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb. The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty

Fig. 7

 7 Fig. 7 Histogram (25 Ma bins), probability density plot (PDP) and Kernel Density Estimate (KDE) of 206 Pb/ 238 U ages for >90% concordant analyses of zircon cores from the eastern FMC granites (obtained using the density plotter program of Vermeesch 2012). The

Fig. 8

 8 Fig.8Plot of the zircon saturation temperature (T Zr sat , in °C) obtained from the whole-rock compositions of the dated samples of Variscan igneous rocks from the eastern FMC (using the equation ofWatson and Harrison 1983), as a function of their "mafic" oxides contents (FeO t + MgO). The fields correspond to the temperature and compositions of experimental melts of[START_REF] Gardien | Experimental melting of biotite + plagioclase + quartz ± muscovite assemblages and implications for crustal melting[END_REF], Patiño-Douce and Harris (1998), Patiño-Douce and[START_REF] Patiño-Douce | Dehydration-melting of biotite gneiss and quartz amphibolite from 3 to 15 kbar[END_REF][START_REF] Patiño-Douce | Effects of P, f(O 2 ) and Mg/Fe ratio on dehydration-melting of model metagreywackes[END_REF], Patiño-Douce and Johnston (1991),[START_REF] Pickering | Fluid-absent melting behavior of a two-mica metapelite: experimental constraints on the origin of black hills granite[END_REF],[START_REF] Vielzeuf | Experimental determination of the fluid-absent melting relations in the pelitic system[END_REF] andVielzeuf and Montel (1994) for metasediments;[START_REF] Beard | Dehydration melting and water-saturated melting of basaltic and andesitic greenstones and amphibolites at 1, 3 and 6.9 kb[END_REF],[START_REF] Bogaerts | Phase Equilibria of the Lyngdal Granodiorite (Norway): Implications for the Origin of Metaluminous Ferroan Granitoids[END_REF], Patiño-Douce and[START_REF] Patiño-Douce | Dehydration-melting of biotite gneiss and quartz amphibolite from 3 to 15 kbar[END_REF],Rapp and Watson (1995),[START_REF] Rapp | Partial melting of amphibolite/eclogite and the origin of Archaean trondhjemites and tonalites[END_REF],[START_REF] Singh | Dehydration melting of tonalites. 2. Compositions of melts and solids[END_REF],Sisson et al. (2005),[START_REF] Skjerlie | Vapour-absentmelting from 10 to 20 kbar of crustal rocks that containmultiple hydrous phases: implications for anatexis in the deep to very deep continental crust and active continental margins[END_REF];[START_REF] Tatsumi | Tholeiitic versus calc-alkalic differentiation and evolution of arc crust: constraints from melting experiments on a basalt from the Izu-Bonin-Mariana Arc[END_REF],[START_REF] Watkins | Archaean TTGs as sources of younger granitic magmas: melting of sodic metatonalites at 0.6-1.2 GPa[END_REF] andWolf and Wyllie (1994) for igneous rocks. The arrows associated with the symbols indicate whether the calculated T Zr sat represents maximum magma temperatures (arrow down, if source-inherited zircons are present) or minimum ones (arrow up, few or no inherited zircons)

Fig. 9

 9 Fig. 9 Histograms and Kernel Density Estimates (KDE) (obtained using the DensityPlotter program of Vermeesch 2012) of 206 Pb/ 238 U ages of zircons from a orthogneisses and b paragneisses of the FMC (data from Melleton et al. 2010; Chelle-Michou et al. 2015; Mintrone 2015); compared to inherited zircons from (c) CPG and (d) MPG investigated in this study. Only analyses with >90% concordance and with 206 Pb/ 238 U ages <1200 Ma are considered. The gray fields in c and d are the KDE of age distributions for zircons of ortho-and paragneisses presented in (a) and (b); the dashed blue curve represent the KDE obtained with all zircons from both ortho-and paragneisses together ▸

Fig. 10

 10 Fig. 10Timeline summarizing all the intrusion ages obtained for Variscan igneous plutonic rocks from the eastern FMC in the course of this study (symbols are as in Figs.2, 8). The groups of samples (CPG, MPG, KCG and vaugnerites) are sorted according to the respective contribution of crustal and mantle sources to their petrogenesis (see "Discussion"). On the right-hand side are represented major time markers in the Variscan evolution of the eastern FMC, including collision-related M 2 metamorphism[START_REF] Gardien | Reliques de grenat et de staurotide dans la série métamorphique de basse pression du Mont Pilat (Massif Central français) : témonis d'une évolution tectonométamorphique polyphasée[END_REF] Caron 1994; Faure et al. 2009;[START_REF] Melleton | Monazite U-Th/Pb chemical dating of the Early Carboniferous syn-kinematic MP/MT metamorphism in the Variscan French Massif Central[END_REF] Schulz 2014), the two anatectic episodes M 3 and M 4 -the latter being related to the development of the Velay dome(Montel et al. 1992; Barbey et al. 1999,

  . Abbreviations are for the names of the dated intrusions: Ald L'Aldeyrès, Alm Almance, Bor Borne, Cha Chassagny, ChD Chaise-Dieu, Chz Chalmazel, Gdr Grandrieu, Gum Gumières, Her Hermitage, Lam Lamastre, LaR La Roche, Lou Loubaresse, Lrg Largentière, Mar Margeride, Mey Meyras, MLi Moulin de Linas, Mrc Marcenod, PtB Pont-de-Bayzan, PtM Pont-de-Montvert, PtR Pont-Rouge quarry, Pub Pubellier, SDz Salt-en-Donzy, SJV Saint-Julien-la-Vêtre, StC Saint-Christophe-d'Allier, StD Saint-Dierd'Auvergne, Tou Tournon and associated intrusions 442 Int J Earth Sci (Geol Rundsch) (2017) 106:421-451 1 3

Fig. 11

 11 Fig. 11 Plot of the intrusion ages obtained for Variscan igneous rocks from the eastern FMC, as a function of the latitude (in decimal degrees) at which the samples were collected. The colored boxes represent individual plutons or batholiths (including the Velay dome); their horizontal extension is constrained by the geographic limits of the pluton, and their vertical extension by the age uncertainties obtained on dated samples from this pluton. The dashed boxes represent a group of plutons or intrusions that belong to the same geo-

Fig. 12

 12 Fig. 12 Two possible, schematic geodynamic models that may account for the spatial and temporal distribution of Variscan igneous plutonic rocks in the eastern FMC during the Carboniferous (c. 340-300 Ma): a southward retreat of a lithospheric mantle slab, after middle Devonian (>360 Ma-old) subduction of continental crust now

  Floc'h JP, Cuney M, Cheilletz A (2001) Datation U-Pb à la microsonde ionique des zircons de l'unité supérieure de gneiss dans le Sud Limousin, Massif Central. C R Acad Sci Paris 332:625-632Annen C, Sparks RSJ (2002) Effects of repetitive emplacement of basaltic intrusions on thermal evolution and melt generation in the crust. Earth Planet Sci Lett 203:937-955 Annen C,[START_REF] Annen | The genesis of intermediate and silicic magmas in deep crustal hot zones[END_REF] The genesis of intermediate and silicic magmas in deep crust hot zones. J Petrol 47(3):505-539 Arnaud F,Burg JP (1993) Microstructures des mylonites schisteuses: cartographie des chevauchements varisques dans les Cévennes et détermination de leur cinématique. C R Acad Sci Paris 11:1441-1447 Arnold J, Jacoby WR, Schmeling H, Schott B (2001) Continental collision and the dynamic and thermal evolution of the Variscan orogenic crustal root-numerical models. 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Comparaison avec les granites S du Lachlan Fold Belt, Australie. Dualité d'origine. C R Acad Sci Paris 314:593-601 Barbarin B (1999) A review of the relationships between granitoid types, their origins and their geodynamic environments. Lithos 46(3):605-626 Barbarin B, Gerbe MC, Vitel G, Gonord H, Couette F, Lebret P (2012) Notice explicative, Carte géologique de la France (1/50,000 e ), feuille Firminy (nr. 744). Orléans, Bureau de Recherches Géologiques et Minières Barbey P, Marignac C, Montel JM, Macaudière J, Gasquet D, Jabbori J (1999) Cordierite growth textures and the conditions of genesis and emplacement of crustal granitic magmas: the Velay granite (Massif Central, France). J Petrol 40(9):1425-1441 Barbey P, Villaros A, Marignac C, Montel JM (2015) Multiphase melting, magma emplacement and P-T-time path in late-collisional context: the Velay example (Massif Central, France). 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C R Acad Sci Paris 289:997-1000 Caen-Vachette M, Couturié JP, Didier J (1982) Ages radiométriques des granites anatectiques et tardimigmatitique du Velay (Massif Central français). C R Acad Sci Paris 294:135-138 Caron C (1994) Les minéralisations Pb-Zn associées au Paléozoique inférieur d'Europe méridionale. Traçage isotropique Pb-Pb des gites de l'Iglesiente (SW Sardaigne) et des Cévennes et évolution du socle encaissant par la géochronologie U-Pb, 40Ar-39Ar et K-Ar. Ph.D. thesis, University of Montpellier 288 pp Castiñeiras P, Villaseca C, Barbero L, Romera CM (2008) SHRIMP U-Pb zircon dating of anatexis in high-grade migmatite complexes of Central Spain: implications in the Hercynian evolution of Central Iberia. Int J Earth Sci 97:35-50 Chauvet A, Volland-Tuduri N, Lerouge C, Bouchot V, Monié P, Charonnat X, Faure M (2011) Geochronological and geochemical characterization of magmatic-hydrothermal events within the Southern Variscan external domain (Cévennes area, France). Int J Earth Sci 101(1):69-86 Chelle-Michou C, Laurent O, Moyen JF, Block S, Gardien V, Paquette JL, Couzinié S (2015) New U-Pb and Hf zircon data from the eastern Massif Central: from Gondwana to Pangea in a nutshell. Géol Fr 1:37-38 Clemens JD, Darbyshire DPF, Flinders J (2009) Sources of post-orogenic calcalkaline magmas: the Arrochar and Garabal Hill-Glen Fyne complexes, Scotland. Lithos 112:524-542 Cocherie A (2007) Datations U-Pb (laser-ICPMS-MC) sur zircons et U-Th-Pb sur monazites de granitoïdes du Massif central (carte de Firminy). Rapport BRGM MMA/ISO-2007/279 Cocherie A, Be Mézème E, Legendre O, Fanning CM, Faure M, Rossi P (2005) Electron-microprobe dating as a tool for determining the closure of Th-U-Pb systems in migmatitic monazites. Am Mineral 90:607-618 451 Int J Earth Sci (Geol Rundsch) (2017) 106:421-451 1 3 Williamson BJ, Shaw A, Downes H, Thirlwall MF (1996) Geochemical constraints on the genesis of Hercynian two-mica leucogranites from the Massif Central, France. Chem Geol 127:25-42 Williamson B, Downes H, Thirlwall M, Beard A (1997) Geochemical constraints on restite composition and unmixing in the Velay anatectic granite, French Massif Central. Lithos 40(2-4):295-319 Wolf MB, Wyllie PJ (1994) Dehydration-melting of amphibolite at 10 kbar: the effects of temperature and time. Contrib Mineral Petrol 115:369-383 Zeh A, Gerdes A (2010) Baltica-and Gondwana-derived sediments in the Mid-German Crystalline Rise (Central Europe): implications for the closure of the Rheic ocean. Gondwana Res 17:254-263 Zeh A, Brätz H, Millar IL, Williams IS (2001) A combined zircon SHRIMP and Sm-Nd isotope study on high-grade paragneisses from the Mid-German Crystalline Rise: evidence for northern Gondwanan and Grenvillian provenance. J Geol Soc Lond 158:983-994 5.2 Additional data: zircon UPb dating of the Monts-du-Lyonnais synkinematic granitoids 5.2.1 Regional context and investigated sample In the southern part of the MontsduLyonnais area (see Fig. 3.1), the metamorphic lithologies of the Upper Gneiss Unit are intruded by the synkinematic Montagny, Saint-Héand, Soucieu and Grand-Chemin (or Civrieux-d'Azergues) granitoids emplaced along

  for the comprehensive dataset). Out of 53 analyses, only four are concordant with 206 Pb/ 238 U dates clustering between 334 ± 6 and 339 ± 6 Ma (spots b194 and b191, respectively, Fig. 5.1b). Thirteen analyses yielded discordant 206 Pb/ 238 U dates in the same range. These spots trend along a mixing line between common and radiogenic (anchored by the concordant population) Pb compositions at 335 Ma (Fig. 5.1b). Four discordant measurements show older 206 Pb/ 238 U dates, up to 452 ± 7 Ma (b185). The 32 remaining analyses have younger 206 Pb/ 238 U dates, from 331 ± 6 (b179) down to 261 ± 5 Ma (b177). Given the scarcity of inherited cores and the typical magmatic oscillatory zoning evidenced by CL-images, I interpret the concordant zircon population as having crystallized from the melt phase. The best estimate of the crystallization age is given by the lower intercept of the mixing trend: 335.8 ± 4.4 Ma (including systematic errors). Spots yielding older 206 Pb/ 238 U dates would have sampled inherited zircon domains unidentied during CL imaging. Younger dates would result from a combination of Pb loss and common Pb incorporation, which respective contributions cannot be retrieved.

Figure 5

 5 Figure 5.1: TeraWasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) showing zircon data for the RV-3 synkinematic granite from the MontsduLyonnais area. Error ellipses/ages are quoted at 2σ level of uncertainty. Yellowish ellipses are those included in age calculations.

5. 3

 3 Article #3: The mantle source of "vaugnerites" and other post-collisional mac magmas This contribution has been published in Earth and Planetary Science Letters. In the course of my M.Sc., I sampled all but two of the igneous rocks presented in this study with the help of Jean-François Moyen, Arnaud Villaros and Adrien Vezinet and prepared them for whole-rock geochemical determinations. I extracted the zircon grains and performed the LuHf isotope measurements at GUF under the supervision of Oscar Laurent and Armin Zeh. Pilar Montero analysed the grains for O isotopes. During my Ph.D., I compiled geochronological and geochemical data available from the literature and wrote the manuscript with signicant help from Oscar Laurent, Jean-François Moyen and Pierre Bouilhol.

Fig. 1 .

 1 Fig. 1. (a) General location of the Variscan belt of Europe and inferred suture zones. Abbreviations: GMC Galicia-Massif Central, STZ Saxo-Thurigian Zone, RHZ Rhenohercynian Zone, MZ Moldanubian Zone. The yellow star highlights the location of the Velay Complex. (b) Geological map of the eastern French Massif Central (Velay area) redrawn after Chantraine et al. (1996). Post-collisional mafic magmas (triangles) and their derivatives (granite bodies in blue) are highlighted. The inset shows the location of the study area within the Massif Central. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3 .

 3 Fig. 3. (a) Compilation of available in-situ Hf isotope data for zircons from PCMM worldwide as a function of their intrusion age (note that the time-scale is logarithmic). Total number of zircon Hf measurements = 2425. The Variscan zircons (box 3) are shown in detail Fig. 3b. The εHf (t) range for the depleted mantle reservoir is bracketed by the models of Naeraa et al. (2012) (lowermost value) and Griffin et al. (2002) (uppermost value). Data from Table S7. (b) Measured zircon εHf (t) in post-collisional mafic rocks from the Variscan belt of Europe as a function of intrusion age. Additional data from Siebel and Chen (2009) and Villaseca et al. (2010).

188S.Fig. 4 .

 4 Fig. 4. (a) Compilation of in-situ O isotope data for zircons of post-collisional mafic rocks from worldwide occurrences. Total number of zircon measurements = 633. Data from TableS8. The δ 18 O for the mantle is fromValley et al. (1998). Arrows for supra-crustal weathered materials and ridge-altered materials according to[START_REF] Bindeman | Oxygen isotopes in mantle and crustal magmas as revealed by single crystal analysis[END_REF].

Fig. 5 .

 5 Fig. 5. Plots of major and trace element characteristics of PCMM from the eastern French Massif Central (only samples with SiO 2 < 63%) highlighting important features of their petrogenesis. (a) Plot of La concentrations vs. Mg#

Fig. 6 .

 6 Fig. 6. (a) Results of assimilation/fractional crystallization (AFC) model of a basaltic melt (Hf content of 2.03 ppm, from Sun and McDonough, 1989; DM-like isotopic composition with εHf (t) = +11 calculated from Naeraa et al., 2012, and δ 18 O = +5.3 from Valley et al., 1998) assimilating bulk continental crust (Hf content of 3.7 ppm, from Rudnick and Gao (2003); εHf (t) = -50 and δ 18 O = +25 adjusted to fit the data for a maximum fractionation rate of ca. 20%); grey dots indicate the fraction of remaining liquid and r the mass ratio between assimilated and crystallized material. (b), (c) and (d) Results of mass-balance, binary mixing models between DM (εHf (t) = +11; δ 18 O = +5.3; Hf contents [0.2 ppm] and Th/La [0.04] from Workman

Fig. 7 .

 7 Fig. 7. (a) Triangular diagram showing the model age and εHf 310 Ma (in brackets) of a virtual sedimentary crustal material as a function of the relative proportion of Archean, Eburnean (Paleoproterozoic) and Pan-African (Neoproterozoic-Early Paleozoic) crust in the latter, assuming identical Hf concentrations in the three end-members. The highlighted model age of 1.8 Ga corresponds to the composition of the crustal material required to explain the zircon Hf isotopic compositions of PCMM in the FMC (εHf 310 Ma of ca. -10; see Fig. 6 and text for discussion). (b) Histogram showing the distribution of zircon εHf 310 Ma for >360 Ma-old grains from all gneiss units in the eastern FMC, taken as representative of the isotopic distribution of Hf in the pre-Variscan crust at the time of PCMM formation. The εHf 310 Ma are calculated using the measured 176 Hf/ 177 Hf and 176 Lu/ 177 Hf ratios of each zircon grain. Data from Chelle-Michou et al. (2015).

Figure 5 .

 5 Figure 5.2 compares the age distribution of inherited zircon grains in MPG/CPG with that of the main lithologies of (a) the Lower Gneiss Unit (b) and the Upper Gneiss Unit. Clearly, the dominant c. 545 Ma inherited population matches the emplacement age of meta-granites from the Velay Orthogneiss Formation. Besides, the Hf isotope composition of these inherited grains remarkably mimicks that of VOF zircons (Fig. 5.3a) providing further evidence for extensive melting of the VOF meta-granites at Variscan times. Involvement of meta-igneous rocks akin to the Riverie tonalites, also of adequate age (Fig. 5.2b) is excluded by their highly radiogenic isotope signature (Fig. 5.3b) not encountered in the c. 545 Ma-old inherited grains. The "tail" of inherited zircon ages running from 560 to 1100 Ma (besides subordinate c. 2 Ga and 2.7 Ga components, not shown) could be explained by the coeval subordinate melting of LGU metasediments and incorporation of detrital zircon grains in the resulting magmas. Such detrital grains do have suitable Hf isotope compositions as they show a similar scatter than the one observed in inherited zircons (Fig. 5.3a). Finally, the age distribution of inherited zircons also displays a peak at c. 470 Ma which does not correspond to any LGU lithology, in our present state of knowledge (Fig. 5.2a). Alternatively, it could be explained by the presence in the granite source region of UGU gneisses and amphibolites (Fig. 5.2b).

Figure 5 . 2 :

 52 Figure 5.2: Inherited zircon UPb date distribution for MPG/CPG granites from the eastern French Massif Central. Only 95105% concordant 206 Pb/ 238 U dates were considered. Data from Couzinié et al. (2014); Laurent et al. (2017) and Chelle-Michou et al. (2017). Are shown for comparison: (a) the distribution of UPb dates in metasediments from the Lower Gneiss Unit represented as Kernel Density Estimate (KDE), together with the range of emplacement ages of meta-granites from the Velay Orthogneiss Formation (data from Chelle-Michou et al., 2017; Couzinié et al., 2017 and Chapter 6); (b) the distribution of UPb dates in gneisses from the Upper Gneiss Unit represented as Kernel Density Estimate (KDE), together with the range of emplacement ages of meta-basites and meta-tonalites from the Upper Gneiss Unit (data from Chelle-Michou et al., 2017 and Chapter 3). Plotted with the DensityPlotter program of Vermeesch (2012). The bandwidth of the KDEs was set to 12 Ma (the average 2σ error of individual analyses).

Figure 5

 5 Figure 5.3: Combined U-Pb and Lu-Hf isotopic data for inherited zircons in Variscan crustderived granites (CPG/MPG) compared to the signature of constituent lithologies from the Lower (a) and Upper (b) Gneiss Units. Data for the Velay Orthogneiss Formation from Couzinié et al. (2017), for the Riverie meta-tonalites from this work, for LGU metasediments from Chelle-Michou et al. (2017) and this work, for Variscan granites from Moyen et al. (2017a); Chelle-Michou et al. (2017), for UGU gneisses from Chelle-Michou et al. (2017). The ε Hf (t) range for the Depleted Mantle reservoir is bracketed by the models of Naeraa et al. (2012) and Grin et al. (2002).

Figure 6

 6 Figure 6.1: (a) General location of the Variscan belt of Europe and inferred suture zones. Abbreviations: GMC Galicia-Massif Central, STZ Saxo-Thurigian Zone, RHZ Rhenohercynian Zone, MZ Moldanubian Zone. The yellow star highlights the location of the Velay Complex. (b) Geological map of the eastern French Massif Central (Velay area) redrawn after Chantraine et al.(1996).

Figure 6 . 2 :

 62 Figure6.2: Geological map at scale 1/290000 outlining the situation of the study area. Lithological contours, foliation trajectories, main regional lineations drawn based on our own eld survey and the works ofAlabouvette et al. (1988);Bambier et al. (1985a);[START_REF] Bouilhol | La Zone Mylonitique Métamorphique Vellave (ZMMV) : une mylonite en cisaillement pur qui signe la mise en place du dôme du Velay sur sa bordure Sud[END_REF];Bouilhol et al. (2006);[START_REF] Briand | Carte géol[END_REF];Choubert and Girod (1974a);[START_REF] Couturié | Carte géol. France (1/50 000[END_REF];[START_REF] Dallain | Textural evolution in the transition from subsolidus annealing to melting process, Velay Dome, French Massif Central[END_REF];[START_REF] Dumas | Le métamorphisme régional des Cévennes occidentales (Massif Central français) : une conséquence de la mise en place du dôme anatectique vellave[END_REF];[START_REF] Faure | Le pluton du Pont-de-Montvert : un granite syntectonique extravasé vers l'Est pendant le désépaississement crustal varisque du Massif Central français[END_REF];Faure (1995);[START_REF] Gèze | Carte géol[END_REF] 1980);Négron (1979);[START_REF] Talbot | Emplacement in an extensional setting of the Mont LozèreBorne granitic complex (SE France) inferred from comprehensive AMS, structural and gravity studies[END_REF] 2005);[START_REF] Rakib | Le métamorphisme régional de basse pression des Cévennes occidentales: une conséquence directe de la mise en place du dôme thermique vellave (Massif central français[END_REF];[START_REF] Viard | Lithostratigraphie et pétrologie des formations métamorphiques du versant nord du mont Lozère[END_REF] and[START_REF] Weisbrod | Carte géol[END_REF]. Abbreviations: M, Masméjean dome; T, Tanargue dome; p-j, PradesJaujac basin; b, Bessèges basin.

Figure 6

 6 Figure 6.3: Summary of available geochronological constraints on tectonic, metamorphic and magmatic events in the upper and the middle crust and at the interface between them (namely the Mylonitic Metamorphic Vellave Zone of Bouilhol et al., 2006). Data from Be Mezeme et al. (2005a); Be Mezeme (2005b); Be Mezeme et al. (2006; 2007); Bouilhol et al. (2006); Bouilhol (2004); Brichau et al. (2007); Bruguier et al. (2003); Caron (1994); Cocherie et al. (2005); Chauvet et al. (2011); Couzinié et al. (2014); Didier et al. (2013); François (2009); Isnard (1996); Laurent et al. (2017);[START_REF] Mialhe | Le massif granitique de la Borne (Cévennes). Etude pétrographique, géochimique, géochronologique et structurale[END_REF];[START_REF] Monié | 40 Ar/ 39 Ar and U-Pb geochronology applied to Au-W-Sb metallogenesis in the Cévennes and Chataigneraie districts (southern Massif Central, France)[END_REF];[START_REF] Montel | Ages stéphaniens des microgranites du Velay (Massif central français)[END_REF] andMougeot et al. (1997).

Figure 6 . 4 :

 64 Figure 6.4: Geological map at scale 1/290000 identical to Fig. 6.2 onto which are reported available geochronological data. Each symbol refers to a specic dating technique as displayed Fig. 6.3. Data sources. 1:François (2009); 2: Monié et al. (2000); 3: Brichau et al. (2007); 4: Isnard (1996); 5: Laurent et al. (2017); 6: Chauvet et al. (2011); 7: Mialhe (1980); 8: Be Mezeme et al. (2007); 9: Be Mezeme et al. (2006); 10: Bruguier et al. (2003); 11: Couzinié et al. (2014); 12: Mougeot et al. (1997); 13: Didier et al. (2013); 14: Montel et al. (2002); 15: Couzinié et al. (2017); 16: Cocherie et al. (2005); 17: Bouilhol et al. (2006); 18: Costa (1990); 19: Be Mezeme et al. (2005a).

6. 2 . 1

 21 Observations from the dome mantleThis section summarizes the structural information gained in the course of two summer eld campaigns (2015 and 2016) and the examination of c. 80 thin sections (most of them being spatially oriented). Fig.6.6 presents interpretative cross-sections summarizing the available structural data on the Masméjean dome.The southwestern ank of the domeIn this domain, the regional foliation S n consistently trends ENESSW to NESW and gently dips to the SW. It gradually rotates east of Belvezet towards a NS direction (Fig.6.5). Intense deformation locally resulted in augen gneisses being converted into Smylonites (Fig.6.7a). Preservation of transposed symmetrical folds indicates that S n reworks an older S n-1 foliation (Fig.6.7b). Stretching lineations within S n are marked by ellispoidal biotite aggegates and Kfs-blasts/clasts (in augen gneisses only) showing a strong preferential orientation in the YZ plane. Lineations generally plunge towards the SWWSW with a maxima at N230 21 • (Fig.6.8a). Lineations in the orthogneisses located South of the Chassezac river and West of the Puylaurent dam show a slightly dierent orientation as they plunge to the SSE (Fig.6.8a). Sections in the XZ plane consistently provide evidence for top-to-the NEENE shearing (Fig.6.9). Shear criteria include C to C' shear bands, asymmetric drag folds and sigmoid mica "shs".

Figure 6

 6 Figure 6.6: Cross-sections of the Masméjean dome. Same legend than Fig. 6.5.

Figure 6

 6 Figure 6.7: Zones of very intense ductile deformation. (a) Very ne-grained mylonitic orthogneiss grading into augen gneiss out of the shear zone, Bois du Pendu near the hamlet of L'Hermet (44.52625, 3.87397). (b) Symmetrical folds developed at the expense of an older S n-1 foliation and admitting S n as axial plane, place known as Les Orts, shores of the Puylaurent dam (44.52805, 3.88016).

  Figure 6.8: Stretching lineations observed in the mantle of the Masméjean dome. Plotted on Schmidt net (lower hemisphere) using the software OpenStereo (Grohmann and Campanha, 2010).

Figure 6 . 9 :

 69 Figure 6.9: Evidence for regional top-to-the NE shearing. (ab): Shear bands within mylonitic augen gneisses, Mirandol railway bridge (a: 44.54905, 3.81606) and Chassezac gully (b: 44.53744, 3.85751). (c): Drag folds developed at the expense of Sil-bearing paragneisses and granitic (presumably intrusive) layers indicating that top-to-the NE shearing was coeval or postdated granitic magmatism, Les Orts, shores of the Puylaurent dam (44.52889, 3.88019). (d) Drag folds aecting a leucogneiss pluri-metric layer within paragneisses, L'Hermet hamlet, shores of the Puylaurent dam, (44.52263, 3.87803). (e) Drag folds within Sil-bearing paragneisses from the Mylonitic Metamorphic Vellave Zone of Bouilhol et al. (2006), east of the Masméjean dome, Notre-Dame des Neiges abbey (44.60092,3.93683). (f) Plane-polarized-light photomicrograph of micaschists showing shear bands locally underlined by truncated garnet porphyroclasts, Mirandol hamlet (44.54613,3.81520). (g) Plane-polarized-light photomicrograph of a quartz-rich paragneiss aected by top-to-the NE shear bands, Chasseradès village, (44.55417, 3.82750). (h) Crosspolarized-light photomicrograph of a syntectonic mica sh in a leucogneiss, Mirandol hamlet (44.54613, 3.81520).

Figure 6 .

 6 Figure 6.10: (ac) Villefort granites, cropping out in the eastern ank of the Masmejean dome. (a) Set of steeply-deeping sills concordant in the foliation of Qz-rich paragneisses, Le Ranc hamlet, AMS site 8, dated sample CHA-15-25 (44.53152, 3.90263). (b) Magmatic layering with accumulation of macroscopically undeformed Kfs megacrysts, dated sample CHA-15-41, place known as Les Clous (44.54657, 3.90506). (c) Grt-bearing leucogranite, AMS site 10, Le Thort hamlet (44.55483, 3.90577). (d) Post-tectonic leucogranite dyke cutting across the foliation of the augen gneiss, Chassezac gully (44.53543, 3.85397). (e) Granite sill intrusive within Silbearing paragneisses and truncated by top-to-the S normal faults, dated sample CHA-15-19, place known as Les Orts, shores of the Puylaurent dam (44.52806, 3.88017). (f) Fine-grained Kfs-Bt-porphyritic granite sill concordant with the foliation of Sil-bearing paragneisses themselves embedded as a decametric rafts in augen gneisses, Chassezac gully (44.53522, 3.85039). (g) Grt-bearing facies of the Rocles syntectonic granite which magmatic foliation is underlined by Bt akes, dated sample ROC-16-01, Le Travers hamlet (44.55534, 4.12841). (h) Kfs-porphyritic Borne granite, dated sample BOR-16-01, D51 road south of the Pied de Borne village (44.46468, 3.97477).

Figure 6 .

 6 Figure 6.11: Evidence for top-to-the SE shearing in the northwestern ank of the Masméjean dome. (a) "Bookshelf" fragmented Kfeldspar porphyroclast, place known as Majousseires (44.58474, 3.81716). (b) Shear bands within a quartz-rich biotite micaschist, place known as Majousseires (44.57436, 3.82279).

Figure 6 .

 6 Figure 6.12: Ductile deformation along the Villefort shear zone. (ab) Distinctive quartzite layer observed along the eastern limb of the Masméjean dome showing a nearly vertical foliation and horizontal mineral lineation marked by scarce Bt aggregates, Le Ranc (a: 44.53489, 3.90404) and La Molette (b: 44.54997, 3.90721) respectively. (cd) Cross-polarized-light photomicrograph of a quartzite showing sigma-shaped quartz porphyroclasts deformed by shear bands oblique to the foliation and indicating sinistral displacement, Le Ranc hamlet (44.53500, 3.90415). (ef) Planepolarized-light photomicrograph of sinistral shear bands aecting (e) sigmoidal QzBt aggregates in a quartzite, Le Ranc hamlet (44.52587, 3.90436) and (f) Qz-rich paragneisses, Prévenchères (44.52235, 3.90554).

Figure 6 . 13 :

 613 Figure 6.13: Typical migmatites from the Masméjean dome core, all developed at the expense of augen gneisses. (a) Metatexite with segregated neosome in the form of leucocratic quartzofeldspathic layers (leucosome), locally folded, and BtKfs-rich melanocratic layers (melanosome). (b) Metatexite with both in-situ and in-source granitic leucosomes. (c) Qz-rich paragneiss resister within migmatites and rounded intrusion of Krich diorite ("vaugnerite"). (d) Syn-anatectic folding of metatexite as evidenced by the leucosome distribution within fold hinges, presumably reecting the collection of anatectic liquids in low-strain domains. (ef) Intricate and gradual transitions between metatexites and granitic zones which contain rafts of anatectic augen gneisses and large Kfs prophyroclasts probably inherited from the latter. Such granitic zones are interpreted as melt percolation channels/pathways. Locations: (ad) Puylaurent dam (44.53037, 3.88719); (e) Borne village (44.61738, 4.01109); (f) place known as Le Bouiol (44.51293, 3.88629).

Figure 6 .

 6 Figure 6.14: Plane-polarized light photomicrographs showing the mineral assemblages of the Masméjean dome migmatites. Mineral abbreviations after Whitney and Evans (2009).

Figure 6 .

 6 Figure 6.15: Histogram of bulk magnetic susceptibility for granite (a) and migmatite (b) specimens collected in the Masméjean dome.

  ). The three bodies sampled to the South on a transect along the Chassezac river show marked variations of the K 3 orientations from one to another (S1, 2 and 8). The magnetic foliation of the westernmost meterscale body (S1) is NS-trending and mimicks that of its host paragneiss, close to the contact with the metatexites. In contrast, granite sills S2 and S3 (out of which samples CHA-15-24 and CHA-15-25 were taken) show ENEWSW to EW-trending magnetic foliations even though the sills are concordant within the steeply dipping NS foliation of the host paragneisses (see Fig. 6.10a). Granite body S5 (corresponding to dated sample CHA-15-41), collected further North, features vertical magmatic layering underlined by the accumulation of macroscopically undeformed Kfs megacrysts (see Fig. 6.10b). It shows a well-dened vertical magnetic foliation and a NS horizontal magnetic lineation.

Figure 6 .

 6 Figure 6.16: AMS scalar parameters for the Masméjean dome samples. Average values for each site correspond to the dark squares (migmatites) and circles (granites). (a) Shape parameter T (Jelínek, 1981) as a function of the total degree of magnetic anisotropy P'. (b) Shape parameter T versus bulk magnetic susceptibility K m . (c) Total degree of magnetic anisotropy P' versus bulk magnetic susceptibility K m .

  CHA-15-35 was taken near the hamlet of Le Couste 40 m east of the bridge over the Chassezac river (Fig.6.5). It corresponds to the country-rock of granite dyke CHA-15-34 (see below). Sample CHA-15-52 was collected at the place known as Majousseires on the path running along the left bank of the Allier river (Fig.6.5).GranitesAligned along the Villefort Shear Zone Four granite bodies were sampled to bracket the timing of the Villefort Shear Zone activity. Specimen CHA-15-24 was collected along the cli below the hamlet of Le Ranc on the left bank of the Chassezac river (Fig.6.5). It belongs to a large granite sill intruding the paragneisses and containing both paragneiss and orthogneiss enclaves (AMS site 2). was sampled 200 m east to CHA-15-24. It corresponds to a meter-thick granite sill injected within quartz-rich paragneisses (AMS site 8, Fig. 6.10a). CHA-15-49 was sampled near the village of Prévenchères at the place known as Le Mourio and was taken 800 m (at crow's ight) south of CHA-15-24 and 25, on the right bank of the Chassezac river. The granite is locally aected by brittle deformation related to the late activity of the Villefort fault. Specimen CHA-15-41 was collected from a granite body at the place known as Les Clous (AMS site 5). The granite displays a magmatic fabric with a vertical foliation underlined by layers rich in centimetric K-feldspar crystals alternating with ne-grained leucocratic domains (Fig. 6.10b). Sub-solidus brittle deformation also aected the body and generated millimeter-scale cataclastic bands showing marked grain-size reduction and subsequent alteration.Aected by late brittleductile top-to-the S deformation Specimen CHA-15-19 was sampled along the trail running from the hamlet of Puylaurent to the place known as Les Orts abutting the shore of the Puylaurent dam (Fig.6.5). It belongs to a meter-sized zoned granite sill with a pegmatitic upper part and a layered lower part (from which the sample was taken). The whole sill experienced post-magmatic non-coaxial deformation at the brittleductile transition. Deformation along N110 shear planes shows an apparent top-to-the S displacement (Fig.6.10e).Post-tectonic dykes and sills Those were selected to bracket the end of the main deformation episode and basement cooling. Specimen CHA-15-33 was sampled from a ne-grained porphyritic granite sill near the hamlet of Le Couste 20 m east of the bridge over the Chassezac river (Fig.6.5). This granite displays a magmatic fabric dened by the planar orientation of millimetric K-feldspar and biotite akes. CHA-15-34 is a granite dyke collected 30 m east of sample 44.53308). The dyke crosscuts the foliation of the surrounding orthogneisses (sample CHA-15-35) and is itself undeformed. CHA-15-51 was taken from a granite dyke cropping out on the left bank of the Allier river at a place known as Majousseires(GPS coordinates: 3.83309, 44.57011). The granite is undeformed, cuts across augen gneisses and is clearly post-tectonic.The Borne pluton Sample BOR-16-01 is a Kfs-porphyritic, Bt-bearing granite representative of the main phase of the Borne batholith (Fig.6.2). It was selected to address the temporal relationships between the Borne pluton and its presumed counterpart on the other side of the Villefort Shear Zone: the Pont-de-Montvert batholith, for which a zircon UPb emplacement age has recently been obtained byLaurent et al. (2017).

Figure 6 .

 6 Figure 6.18: Representative cathodoluminescence images of zircon grains from dated samples. The locations of laser spots (white circles) are indicated along with the spot name (aXX, bXX, cXX, dXX; a and b refer to the sessions performed the 2 nd and 3 rd of May 2016 at GUF, respectively; c and d to the sessions performed the 12 th and 14 th of February 2017 at ETH, respectively). The corresponding 206 Pb/ 238 U dates are quoted with ± 2σ uncertainty, in Ma. All displayed analyses are concordant (except those in italic). Spot diameters are 20 and 30 µm.

Figure 6 .

 6 Figure 6.19: Tera-Wasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) for zircon from the orthogneiss samples. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellow ellipses are those considered for Concordia age calculations.

Figure 6 .

 6 Figure 6.20: Tera-Wasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) for zircon from: (ad) the Villefort syntectonic granites; (e) the Rocles syntectonic granite, emplaced during the top-to-the NE shearing event; (f) the Les Orts granite, showing evidence for top-to-the S shearing at the brittle/ductile transition. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellow ellipses are those considered for Concordia age calculations. Dotted ellipses are those for which a common Pb correction was performed.

Figure 6 .

 6 Figure 6.21: Tera-Wasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) for zircon from samples of: (a) the Le Couste porphyritic granite sill; (b) the Borne porphyritic granite batholith; (cd) post-tectonic granite dykes showing sharp intrusive contacts with their subsolidus country-rocks. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellow ellipses are those considered for Concordia age calculations. Dotted ellipses are those for which a common Pb correction was performed.

Figure 6 .

 6 Figure 6.22: Tera-Wasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) for zircon extracted from migmatite samples. Error ellipses and ages are displayed at 2σ level of uncertainty.

Figure 6 . 23 :

 623 Figure 6.23: Histogram showing the 206 Pb/ 238 U dates of zircon grains analysed in migmatites from the southern part of the Velay Dome. Bin width is 15 Ma. Available zircon 206 Pb/ 238 U dates (concordance: 95105%) for the Velay Orthogneiss Formation (in red, data from this chapter and Part 1, N=107) and regional metasediments (in blue, data from Chapter 2 and Chelle-Michou et al., 2017, N=445) represented as Kernel Density Estimates. The latter were calculated using the DensityPlotter program of Vermeesch (2012) with a bandwidth set at 15 Ma.

Figure 6 .

 6 Figure 6.25: Tera-Wasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) for monazite extracted from: (ac) migmatites sampled at the Puylaurent dam; (d) a Saint-Laurent-les-Bains migmatite (see Bouilhol et al., 2006); (d) Villefort granite CHA-15-25; (e) post-tectonic granite dyke CHA-15-34. Zircon UPb dating did not yield any concordant Variscan date for all samples. Error ellipses and ages are displayed at 2σ level of uncertainty. Dotted ellipses were not considered for calculations.

Figure 6 . 26 :

 626 Figure 6.26: Summary of the zircon and monazite LAICPMS UPb ages obtained in the course of this study. Same legend as Fig. 6.3. The emplacement age of the Pont-de-Montvert pluton is from Laurent et al. (2017).

  and the selfconsistent thermodynamic dataset ofHolland and Powell (1998) (updated version of 2004). The chemical system retained is Na 2 OCaOK 2 OFeOMgOAl 2 O 3 SiO 2 H 2 O TiO 2 (NCKFMASHT) i.e. all iron is ferrous and Mn not considered.

Figure 6 .

 6 Figure 6.27: PT pseudosection calculated using a representative augen gneiss composition. White lines are melt isopleths (with numbers indicating melt wt.%). Initial water content was adjusted to avoid subsolidus water oversaturation at 0.5 GPa. Mineral abbreviations after Whitney and Evans (2009).

Figure 6 .

 6 Figure 6.28: Geochemical characteristics of granites, metatexites, in-source leucosomes and basement orthogneisses from the Masméjean dome. (a) BA diagram of Debon and Le Fort (1983) modied by Villaseca et al. (1998). (b) Eu/Eu* vs. Nb/Y plot. (c) Al 2 O 3 vs. Ba + Sr plot, the dark eld correspond to the modelled melt compositions. (d) Nb vs. Ba + Sr plot, the text right of each dark eld indicates the specic TX H2O conditions. Same legend as Fig. 6.5 with additional symbols: blue diamonds and black asterisk, referring to in-source leucosomes and the representative augen gneiss sample SC-14-33 considered for thermodynamic modelling, respectively. Mixing trends are calculated between: (i) extremal model melt compositions and (ii) the average composition of K-rich calc-alkaline granites ("KCG" of[START_REF] Barbarin | A review of the relationships between granitoid types, their origins and their geodynamic environments[END_REF] from the French Massif Central, regarded as mantle-derived magma fractionates(Laurent et al., 2017; Moyen et al., 2017a). Data for KCGs (6572 wt.% SiO 2 ) are from this study (sample BOR-16-01),[START_REF] Delfour | Notice explicative, Carte géol[END_REF];François (2009);[START_REF] Mialhe | Le massif granitique de la Borne (Cévennes). Etude pétrographique, géochimique, géochronologique et structurale[END_REF];[START_REF] Sabourdy | Apport de la géochimie à la connaissance de la pétrogenèse des granitoïdes des Cévennes méridionales, Massif central français[END_REF], and personnal communications from B. Barbarin, M. Cuney and J.-F. Moyen. Number of analyses is 146 for Al 2 O 3 , 143 for Ba+Sr and 8 for Nb. The grey eld depicts the compositional variability of orthogneisses from the Velay Orthogneiss Formation. X H2O are quoted in wt.%.

Figure 6 .

 6 Figure 6.29: Histogram showing the 206 Pb/ 238 U dates of inherited zircon grains and xenocrysts from granites sampled in the southern part of the Velay Dome. Data from Couzinié et al. (2014) and this study. Bin width is 15 Ma. Available zircon 206 Pb/ 238 U dates (concordance: 95105%) for the Velay Orthogneiss Formation (in red, data from this chapter and Part 1, N=107) and regional metasediments (in blue, data from Chapter 2 and Chelle-Michou et al., 2017, N=445) represented as Kernel Density Estimates. The latter were calculated using the DensityPlotter program of Vermeesch (2012) with a bandwidth set at 15 Ma.

Figure 6 . 32 :Figure 6 . 33 :

 632633 Figure6.32: Calculated maximal Zr concentration (in ppm) in the melt phase for a fully hydrated (at 0.5 GPa) orthogneiss composition (SC-14-33). Based on the equation ofBoehnke et al. (2013). The Zr concentration of the stoechiometric zircon was set at 497644 ppm.

Figure 6 .

 6 Figure6.34: Calculated proportion (white lines, in wt.%) of the orthogneiss zircon budget to be dissolved in order to saturate the melt phase. The average Zr content of the protolith was set to 115 ppm for. Dotted lines and bold numbers are melt isopleths and melt contents in wt.%, respectively.

  Fig 6.2 and 6.5) cannot be reconciled with a 12 km, post-anatectic, brittle oset. Third, evidence for left-lateral ductile shearing (see section 6.2.1), syntectonic granite intrusion and the overall asymmetric shape of the Masméjean dome collectively demonstrate that the Villefort Shear Zone controlled the exhumation of the Masméjean migmatite dome on its eastern ank.

  the presence of migmatites in the basal conglomerates argues for fast denudation rates by the late Carboniferous/early Permian. Finally, the c. 275 Ma intrusion age of a granite dyke from the Masméjean dome suggests that high-temperature conditions and anatexis in the deep crust may have lasted until the middle Permian, as observed in other late-Variscan domains such as the IvreaVerbano zone(Klötzli et al., 2014 and references therein) or the Pyrénées[START_REF] Denèle | Permian granites in the Pyrenees: the Aya pluton (Basque Country)[END_REF].6.7 Conclusion6.7.1 Middle-upper crust mechanical uncoupling during domingVertical extrusion of partially molten crust in the Masméjean dome is documented by the presence of cascading folds, the foliation attening in the dome core and AMS measurements imaging a bulk ow along the southwestern dome ank towards the NE at an angle of c. 30 • (see section 6.2.3). In this frame, normal top-to-the SW displacement of the dome mantle with respect to the core would be expected. Of critical importance is the comprehensive lack of tectonic evidence for such dierential transport in the unmolten mantle. There, ductile meso-and micro-structures strictly relate to the early c. 320 M-old top-to-the NE shearing event. Only discrete top-to-the S brittle-ductile shear bands (see Fig. 6.10e) would record dome exhumation.The observed situation demands a mechanical decoupling between the anatectic domain and the overlying unmolten lithologies. Here again the origin of such probably lies in the contrasted rheological properties of both materials, with the migmatites showing markedly lower strengths than subsolidus ortho/paragneisses. This way, the strain related to dome exhumation would have been localized within metatexites from the coremantle interface, overlying unmolten lithologies acting as rigid passive blocks and remaining unaected by the extrusion of the partially molten middle crust. Overall, such decoupling inherently stems from the presence of melt in the middle crust, which, as demonstrated above, partly results from a water inux from uprising deep magmas.

  6.7.3 What controls the locus of doming during post-collisional extensionFollowing the conclusions of section 6.4, anatexis in the Masméjean dome would have occurred at moderate temperature (mostly <730760 • C) but still generated substantial amounts of melt due to water ingress from intruding mantle-derived granitic magmas (of KCG type). This viewpoint is corroborated by geochemical data indicating a mixed origin for the Masméjean granites with a fraction corresponding to local pristine anatectic melts and the remaining being akin to KCG magmas.

Figure 6 .

 6 Figure 6.37: Conceptual sketch illustrating the role of mantle-derived magmas in ultimately controlling anatexis at mid-crustal levels. Lower crustal melting and associated peraluminous granite suites are not depicted.

7. 1

 1 Figure 7.1: Summary of the coupled petrological and zircon UPbHf constraints obtained on the French Massif Central. Data from this work, Couzinié et al. (2014), Moyen et al. (2017a) and Chelle-Michou et al. (2017). The relative extent of the UPb date peaks has to be moderated with the uneven data sources. UPb date distribution is represented as a Kernel Density Estimate (KDE). Only 95105% concordant 206 Pb/ 238 U (for dates < 1.2 Ga) and 207 Pb/ 206 Pb dates (for dates > 1.2 Ga) were considered. Plotted with the DensityPlotter program of Vermeesch (2012). The bandwidth was set to 12 Ma (the average 2σ error of individual analyses). The black dotted lines depicts the time-integrated ε Hf (t) evolution of an upper crustal with a 176 Lu/ 177 Hf of 0.0113. The range for the Depleted Mantle reservoir is bracketed by the models of Naeraa et al. (2012) and Grin et al. (2002).

Figure 7 . 2 :

 72 Figure 7.2: Summary of the coupled petrological and zircon UPbHf constraints obtained on the French Massif Central with en emphasis on the period 2001100 Ma. Same legend as Fig. 7.1. The red dotted line highlights the linear ε Hf (t)time array connecting the Velay Orthogneiss Formation and the post-collisional Variscan granitoids with a slope corresponding to a 176 Lu/ 177 Hf of 0.01.

Figure 7 . 3 :

 73 Figure 7.3: Histogram showing the distribution of zircon UPb dates in the French Massif Central. Are shown in (a) the full dataset and in (b) only the spots for which Hf isotope composition have also been measured. In both cases, only 95105% concordant 206 Pb/ 238 U (for dates < 1.2 Ga) and 207 Pb/ 206 Pb dates (for dates > 1.2 Ga) were considered.

Figure 7 . 4 :

 74 Figure 7.4: Histogram showing the distribution of zircon T DM model ages in the French Massif Central. Calculated with a 176 Lu/ 177 Hf of 0.0113 and two Depleted Mantle reservoir compositions (a: Naeraa et al., 2012 and b: Grin et al., 2002).

  3.3 Ga with a are-up at 1.21.4 to 1.31.5 Ga (depending on the Depleted Mantle composition retained). New crust extraction continued till 0.6 Ga at a slower pace.Overall, more than 60% of the local crust would have formed during the Mesoproterozoic.

Figure 7 . 5 :

 75 Figure 7.5: Integral growth curves of the French Massif Central crust obtained from the zircon UPb and T DM date distributions.

  Ediacaran metasediments from the French Massif Central are typied by their very scattered detrital zircon Hf isotope compositions (up to 45 ε-unit, Fig.7.1) observed within individual specimen (section 2.2). Such pattern is consistent with eroded Neoproterozoic magmatic rocks originating from melting of two sources: (i) the Depleted Mantle or materials extracted from this reservoir shortly prior to melting, as evidenced by zircon with highly radiogenic Hf isotope signature; (ii) old crustal remnants, most probably of Paleoproterozoic/Archean age, for grains with strongly non-radiogenic compositions. The whole range in between these endmembers, and notably the cluster between +5 and -5

7. 3 . 1

 31 What is the proportion of young Neoproterozoic crust in the Ediacaran sedimentary basins of the Massif Central? The Ediacaran (590545 Ma) deposition of metasediments from the Lower Gneiss Unit stamps the formation of the earliest crustal rocks in the French Massif Central. Examination of the detrital zircon UPbHf signature indicates that the Ediacaran basins collected detritus from the adjacent Cadomian magmatic arc and a distal source, possibly the Saharan Metacraton (see section 2.2). From a crust evolution perspective, it is critical to establish the actual amount of young Neoproterozoic arc crust in the detritus that fed the Ediacaran basins. In other words, how much of the FMC earliest crust is Neoproterozoic in age? As explained in the previous section, assessing the amount of young crust based on the proportion of Cadomian zircon grains showing radiogenic Hf isotope signatures is not relevant due to sampling biases (low zircon fertility of arc rocks, tendency to show concordant UPb dates). Besides, such approach would not take into account zircon grains having non DM-like, mixed Hf isotope signatures, even though part of their parental magma mass do represent new Neoproterozoic additions to the crust volume. As an alternative, the (meta)granites from the Velay Orthogneiss Formation may provide another probe of the actual amount of Neoproterozoic detritus in the Ediacaran basins. Following the conclusions of section 2.1, the (meta)granites originate from melting of the Ediacaran metasediments and their chondritic Hf isotope signature would result from dissolution of detrital zircon grains during melting and Hf isotope homogenization during ascent. If true, this model hints that the VOF averages the Hf isotope composition of its Ediacaran sedimentary source.

Figure 7

 7 Figure 7.7: Triangular diagram showing ε Hf (545 Ma) of a virtual sedimentary material as a function of the relative proportion of Archean, Eburnean (Paleoproterozoic) and Cadomian crust in the latter, assuming identical Hf concentrations in the three end-members. The highlighted value of zero corresponds to the composition of the crustal material required to explain the zircon Hf isotope signature of the Velay Orthogneiss Formation.

Figure S1 :

 S1 Figure S1: U-Pb Concordia diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for zircon (a, b, c, e) and monazite(d, f -in blue) analyses from samples of CPG from the eastern FMC. Insets in the bottom right of some diagrams represent close-ups to the analyses from zircon cores or xenocrysts ("Xen."), reported as shaded ellipses. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty.

   is the most representative facies of the porphyritic, biotite-bearing Tournon laccolith and was collected at the type locality in Tournon-sur-Rhône. It contains abundant zircon cores and xenocrysts, from which the analyses yield Ordovician to Neoproterozoic dates n = 17). The main populations are Ordovician (~480 Ma; n = 5) and late Neoproterozoic (580 -670 Ma; n = 7). Analyses from zircon rims or devoid of any core yield 206 Pb/ 238 U dates ranging between 261 and 325 Ma (n = 14), corresponding to a well-defined Discordia (MSWD = 0.15) with an upper intercept of 321 ± 6 Ma. The latter is identical to the Concordia date of 321.1 ± 1.1 Ma calculated using the six equivalent analyses with the highest 206 Pb/ 238 U ratios. Sample TOU-01 (Fig.S2) TOU-01 is a sample of K-felspar porphyritic, biotite-bearing granite from the Dunières laccolith that flanks the Velay granite at its easternmost margin. It contains only a few zircon cores having generally discordant U-Pb dates, only one (a54) showing a concordant Cambrian date ( 206 Pb/ 238 U date = 541 ± 10 Ma). The others show a range of 207 Pb/ 206 Pb dates from late Cambrian to Neoarchean (490-2550 Ma; n = 7). Core-free zircons and rims show 206 Pb/ 238 U dates ranging from 270 to 327 Ma (n = 22), defining a Discordia trend with an upper intercept at 326 ± 11 Ma. The eleven spots with the highest, equivalent 206 Pb/ 238 U ratios define a Concordia date of 322.2 ± 1.5 Ma. Sample PRC-57 (Fig.S2) PRC-57 is representative of the main facies of the Velay cordierite-and biotite-bearing granite. It was collected in the central part of the dome, at the Pont-Rouge quarry. The zircon population from this sample is very heterogeneous; most grains have core-rim relationships or are obvious xenocrysts (broken edges cross-cutting the exiting zonation). A total of 21 analyses from those zircons yielded Devonian to Neoproterozoic dates, with several clusters at ~370 Ma (n = 4), ~470 Ma (n = 2), 530-580 Ma (n = 9) and 600-670 Ma (n = 3). Older dates (n = 3) include early Neoproterozoic to nearly Archean ages (concordant analyses a77 at ~840 Ma and a76 at ~2450 Ma

Figure S2 :

 S2 Figure S2: U-Pb Concordia diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for zircon (a-e) and monazite (f -in blue) analyses from samples of CPG from the eastern FMC. Insets in the bottom right of some diagrams represent close-ups to the analyses from zircon cores or xenocrysts ("Xen."), reported as shaded ellipses. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty.

Figure S3 :

 S3 Figure S3: U-Pb Concordia diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for zircon(a, b, d) and monazite (c -in blue) analyses from samples of MPG from the eastern FMC. Insets in the bottom right of some diagrams represent close-ups to the analyses from zircon cores or xenocrysts ("Xen."), reported as shaded ellipses s. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty.

Figure S4 :

 S4 Figure S4: U-Pb Concordia diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for zircon analyses from samples of KCG from the eastern FMC. Insets in the bottom right of some diagrams represent close-ups to the analyses from zircon cores or xenocrysts ("Xen."), reported as shaded ellipses. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty.

Figure S6 :

 S6 Figure S6: U-Pb Concordia diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for zircon analyses from samples of vaugnerites from the eastern FMC.Insets in the bottom right of (d) represent close-ups to the analyses from zircon cores or xenocrysts ("Xen."), reported as shaded ellipses.Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty.

Figure S8 :

 S8 Figure S8: Selected back-scattered electron (BSE) images of representative monazite grains from the four samples of CPG and MPG for which this mineral has been analyzed. Analytical spots are indicated (white circles) as well as the corresponding analysis label and 206 Pb/ 238 U age (with 2σ uncertainty) in Ma. The scale bar is 100 µm.

( b )

 b U and Pb contents (in ppm) and Th/U ratios were calculated relative to GJ-1 reference zircon (U = 280 ppm; Pb = 25.5 ppm).(c) Percentage of the common Pb on the 206 Pb (b.d. = below dectection limit) calculated using the interference-and background-corrected204 Pb signal and common Pb model composition ofStacey & Kramers (1975

  picked under a binocular microscope, 20 to 40 zircons per sample (only 13 for SC13-02A) were cast in epoxy mounts and subsequently polished to expose their interiors. Internal structures of zircon grains were documented in four steps: (i) transmitted light optical imaging; (ii) reflected light optical imaging; (iii) cathodoluminescence imaging (Fig.A6); (iv) low magnification SE-SEM imaging to assemble a navigation map. The last two steps were performed on a ZEISS EVO-150 SEM at the University of Granada (Spain).

Figure S3 :

 S3 Figure S3: Photomicrographs showing the mineral assemblages of the dated samples: (a-b) augen gneisses MM06 and MM11, respectively; (c-d) leucogneisses MM09 and MM10, respectively.

  ., 2017. Supplementary Table 6 (continued):In situ LA-MC-ICPMS Lu-Hf isotope data for zircon standards analyzed in this study calculated using the apparent Pb-Pb age determined by LA-ICP-MS dating (see column f), and the CHUR parameters:

  tions of the 207 Pb/ 206 Pb and 238 U/ 206 Pb ratios during measurements, possibly revealing the sequential sampling of dierent age domains within single zircon grains. Signal was tuned for maximum sensitivity for Pb and U while keeping low the production of oxides ( 254 UO/ 238 U ≤ 0.5%). The obtained sensitivity on zircon standard GJ-1 for 238 U and a Data were acquired using time resolved-peak jumping, the detector being set to analogue mode for 232 Th and 238 U and counting mode for 204 (Hg+Pb), 206 Pb, 207 Pb and 208 Pb. A total of 356 mass scans were acquired over ≈41 s measurement (20 s of background measurement followed by 21 s of sample ablation) and integrated to 89 ratios (4 mass scans per integration, time resolution = 0.46 s). Those ratios were subsequently corrected oine for background signal, common Pb, instrumental mass discrimination and Pb/U fractionation (both laser-induced during individual measurements, and over

  dance which are likely to occur in polymetamorphic environments such as the Variscan FMC. Such a guestimate is not satisfactory as it might result in articially young concordant 206 Pb/ 238 U dates. Finally, the Pb c correction itself reduces the precision of the analytical data because of: (i) the use of a model Pb c composition(Stacey and Kramers, 1975); (ii) the interference at mass 204 between 204 Hg (originating from the gas carrier) and 204 Pb leading to a larger uncertainty on the Pb c -corrected 207 Pb/ 206 Pb ratios. As a consequence of this, inherently discordant Pb c -corrected analyses would be labelled concordant because of their large error ellipse that would overlap with the Concordia curve.

(

  ≈500 cps), to the measured intensity. Composition of common Pb (i.e. 206 Pb/ 204 Pb and 207 Pb/ 204 Pb ratios) was determined using a model Pb composition(Stacey and Kramers, 1975) at the age of 305 Ma. The inter-elemental fractionation 206 Pb/ 238 U during the 21 s of sample ablation was corrected for each analysis by applying a linear regression through all measured ratios, excluding the outliers (±2σ), and considering that the intercept with the y-axis represents the "true" ratio. Elemental fractionation over the analytical session, as well as instrumental mass discrimination, were corrected by normalization to the 206 Pb/ 238 U (0.0982) and 207 Pb/ 206 Pb (0.061) ratios of reference zircon GJ-1(Jackson et al., 2004), using standard bracketing. Elemental concentrations in U and Pb were calculated using raw signal (in cps) of 238 U and 206 Pb for each spot, corrected from the analytical drift over the session (monitored using GJ-1), normalized to the recommended values of the GJ-1 zircon standard (U = 280.1 ppm; Pb = 25.5 ppm) and applying a spot size-dependent correction. Th/U ratio was determined for each spot using the mass fractionation-corrected 232 Th/ 238 U ratio, normalized to the recommended value of the GJ-1 zircon standard (Th/U = 0.0296).Data from secondary standards were processed as unknowns to check the accuracy of the corrections (Fig. B.1). Our results are within error of the recommended TIMS values for the standard zircon BB-16 (weighted mean 206 Pb/ 238 U = 560 ± 0.8 Ma; Santos et al., in press). For Ple²ovice, our in-situ measurements outline two statistically distinct Concordia ages of c. 343 and c. 336 Ma (see Fig. B.1), the latter being identical within error to the TIMS weighted mean 206 Pb/ 238 U age of 337.13 ± 0.37 Ma reported by Sláma et al. (2008a). The c. 343 Ma-old population may reect the presence of older, inherited zircon domains within the Ple²ovice grains.

Figure B. 1 :

 1 Figure B.1: Wetherill diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for secondary zircon standards Ple²ovice and BB-16 analysed during the two analytical sessions conducted at GUF. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellow and blue ellipses are those considered for Concordia age calculations.

Figure B. 2 :

 2 Figure B.2: Wetherill diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for secondary zircon standards Ple²ovice, Temora and 91500 analysed during the analytical sessions conducted at SUN. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellow ellipses are those considered for Concordia age calculations.

Figure B. 3 :

 3 Figure B.3: Wetherill diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for secondary zircon standards Ple²ovice and Temora analysed during the three analytical sessions at ETH Zuerich. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellow ellipses are those considered for Concordia age calculations.

Figure B. 4 :

 4 Figure B.4: Wetherill diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for secondary zircon standard 91500 analysed during the three analytical sessions at ETH Zuerich. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellow ellipses are those considered for Concordia age calculations.

Table B3 :

 B3 Results of LA-ICP-MS U-Pb analyses of zircon standards performed during the sessions at GUF, 2nd and 3rd of Maythe quadratic additions of the within run precision (2 SE) and the external reproducibility (2 SD) of the reference zircon. content and Th/U ratio were calculated relative to GJ-1 reference zircon. c percentage of the common Pb on the 206 Pb. b.d. = below dectection limit. d corrected for background, within-run Pb/U fractionation (

  content and Th/U ratio were calculated relative to GJ-1 reference zircon. c corrected for background, within-run Pb/U fractionation (size = 30µm; depth of crater ~20µm. 206 Pb/ 238 U error is the quadratic additions of the within run precision (2 SE) and the external reproducibility (2 SD) of the reference zircon. Results of LA-ICP-MS U-Pb analyses of zircon standards performed during the sessions at ETH Zürich, 12 to 14th of February, 20µm (for seq. 1) and 30µm (for seq. 2 & 3) a Within run background-corrected mean 207 Pb signal in cps (counts per second). b U and Pb content and Th/U ratio were calculated relative to GJ-1 reference zircon. c corrected for background, within-run Pb/U fractionation

  20µm (for seq. 1) and 30µm (for seq. 2 & 3) a Within run background-corrected mean 207 Pb signal in cps (counts per second). b U and Pb content and Th/U ratio were calculated relative to GJ-1 reference zircon. c corrected for background, within-run Pb/U fractionation

  In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon standards analysed at LMV, Mean Hf signal in volt. (c) Initial 176 Hf/ 177 Hf and eHf calculated using the apparent Pb-Pb age determined by LA-ICP-MS dating (see column f), and the CHUR parameters: 176 Lu/ 177 Hf = 0.0336, and 176

  In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon standards analyzed at LMV, 7th of June, 2017 In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon standards analyzed at LMV, 7th of June,

  UPb dating of the Itambé monazite reference material are displayed TableB16. The obtained weighted average 207 Pb/ 235 U age of 507.8 ± 3.8 Ma (Fig.B.5), overlapping within error with the IDTIMS literature value(Gasquet et al., 2010).

Figure B. 5 :

 5 Figure B.5: Wetherill diagram ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for secondary monazite standards Itambé analysed during the analytical sessions conducted at LMV. Error ellipses and ages are displayed at 2σ level of uncertainty.

  3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 The Lyonnais Orthogneiss Formation . . . . . . . . . . . . . . . . . . . . . Geological setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 The Velay Complex . . . . . . . . . . . . . . . . . . . . . . . . . .

	from the Masméjean migmatite dome 6.1 3.2.1 6 Post-collisional exhumation of the partially molten crust: a case study 6.1.2 Chapter 1
	Introduction
	1.1 The continental crust
	1.1.1 Structure and composition

Table 1

 1 Nature, mineralogy and sampling localities of the investigated samples of the Velay Orthogneiss Formation together with results of zircon U-Pb dating performed in this study.

	Sample Velay	Locality	Lat. N	Long. E Type	Mineralogy a	U-Pb	±2σ N U-Pb	c MSWD C+E d εHf(t) e ±2σ N Lu-Hf	f
	domain					age b
	MM06 Arc de Fix S t Privat d'Allier	44.98811 3.68093 Augen gneiss Qz + Kfs + Pl + Bt + Ms	541.8 3.1	16	0.34	-0.2	2.9	13
	MM09 Arc de Fix Langogne	44.69490 3.88376 Leucogneiss	Qz + Kfs + Pl + Bt + Ms + Gt 545.9 4.3	9	1.05
	MM10 Arc de Fix Labastide-Puylaurent 44.56838 3.87095 Leucogneiss	Qz + Kfs + Pl + Ms	541.4 2.3	26	0.38
	MM11 Arc de Fix Col de Meyrand	44.60534 4.07040 Augen gneiss Qz + Kfs + Pl + Bt + Ms	542.5 3.1	17	0.43	-0.2	1.2	14

a Main mineral phases. b U-Pb Concordia age obtained in the course of this study, in Ma. c Number of analyses used to calculate the Concordia age. d MSWD of concordance + equivalence for the displayed Concordia age. e εHf(t) measured on magmatic zircons, calculated at the emplacement age of the sample. f Number of Lu-Hf analyses. 21 S.

Table 2

 2 Experimental melts database used in this study. List of starting materials, pressures and temperatures of melting and associated references (available as Supplementary text).

	Source rock	Reference

  The oldest emplacement age determined for the VOF samples (545.9 ± 4.3 Ma, leucogneiss MM09) entails that the minimum depositional age of the sediments is at least Ediacaran. As a direct consequence of this, metasediment zircon grains with concordant 206 Pb/ 238 U dates younger than 546 Ma likely experienced limited recent Pb loss. Those analyses would have remained concordant because of the weak curvature of the Concordia at Neoproterozoic/Paleozoic times. This situation is observed in sample PIL-16-01 where spot #116 shows a concordant 206 Pb/ 238 U date of 526 ± 5 Ma. Excluding those grains, the maximum depositional age is given by that of the youngest zircon population in each sample. The latter has been estimated via the following procedure. First, the youngest (and older than c. 545 Ma) concordant analysis is identied. A Concordia date is then calculated out of it and the closest older analysis. If the MSWD of concordance and equivalence is acceptable (close to 1, meaning that the two zircon grains likely belong to a single population), the next older analysis is added to this pool and a

new Concordia date calculated. This procedure is repeated until the MSWD markedly departs from 1, indicating that two dierent populations are sampled. All investigated metasediments yielded late Ediacaran ages (Fig.

2

.4), ranging from 592.4 ± 5.5 Ma for sample PdB-16-01 down to 553.2 ± 5.3 Ma for PIL-16-01. Samples SEN-16-01 and CHA-16-02 show identical maximum sedimentation ages of 567.7 ± 6.0 and 567.0 ± 5.0 Ma respectively. These results are consistent with the presence of inherited zircon grains/xenocrysts of that age in c. 540 Ma-old (meta)granites from the VOF.

2.2.8 Zircon sources

Comparison with other Cadomian terrains The zircon age distribution of all four samples is consistent with the pattern displayed by other Ediacaran (meta)sediments from the northern margin of Gondwana. Indeed, detrital zircon studies on the western Massif Central

(Chelle-Michou et al., 2017; Melleton et al., 2010)

together with Iberian

Table 3 .

 3 1: Summary of available geochronological data on the Monts-du-Lyonnais orthogneisses.

Moreover, a zircon extracted from the Duerne orthogneiss and analysed with the Pb evaporation method by

Feybesse et al. (1995)

yielded an Ediacaran date of 567 ± 12 Ma interpreted as an inherited age.

Table 3 .

 3 2 summarizes the characteristics of each group and the inferred number of specimen in both the small bodies and the Riverie band. Overall, examination of our new dataset together with available literature data indicates that: (i) the "LREE-tholeiite" type of[START_REF] Briand | Geochemistry of bimodal amphibolite-felsic gneiss complexes from eastern Massif Central, France[END_REF] is the most abundant within the LeptyniteAmphibolite Complex; (ii) the small bodies and Riverie band are typied by the presence of Group III and IV samples, respectively.

Table 3 .

 3

2 summarizes the conclusions of this study, specifying the typology, potential source and age of the dierent series.

Table 3 .

 3

2: Characteristics of the dierent metabasite groups identied in the Upper Gneiss Unit from the Monts-du-Lyonnais area

  ). The corresponding 206 Pb/ 238 U dates are quoted with ± 2σ uncertainty, in Ma. All displayed analyses are concordant at >98% (except those in italic). Hf isotope data are reported using the ε Hf calculated at the 206 Pb/ 238 U date obtained on the same zircon domain, quoted with 2σ uncertainty. Wasserburg diagrams ( 238 U/ 206 Pb vs. 207 Pb/ 206 Pb) for zircon from the Riverie meta-tonalite samples. Error ellipses and ages are displayed at 2σ level of uncertainty. Yellowish ellipses are those considered for Concordia age calculations.with an average value of 10.5 ± 0.9(2 S.D. standard deviation; Fig. 3.13). Zircons from sample RV-2 (excluding analysis 59a) show a similar range of 176 Hf/ 177 Hf(t) ratios, from 0.282717 ± 0.000033 to 0.282787 ± 0.000044 (2 S.E. standard error) equivalent to ε Hf (t) of 9.7 to 12.2 (Fig.3.13) and yielding an identical average ε Hf (t) at 10.7 ± 1.2 Hf (t) on magmatic zircon grains from the two investigated meta-tonalite samples of the Riverie band. The ε Hf (t) are recalculated and plotted at the 206 Pb/ 238 U age of each analysed zircon domain (ensuring a better graphical representation). When such value was not available, the intrusion age determined for the sample was used. The range for the Depleted Mantle reservoir is bracketed by the models ofNaeraa et al. (2012) for the lowermost value and[START_REF] Grin | Zircon chemistry and magma mixing, SE China: In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes[END_REF] for the uppermost value. Data from the Velay Orthogneiss Formation (see section 1.1) are also plotted for sake of comparison.

	Figure 3.12: Tera-(2 S.D. standard deviation). Spot 59a was performed on a zircon rim with a younger 206 Pb/ 238 U date of 361 ± 4 Ma. A 176 Hf/ 177 Hf(t) ratio of 0.282744 ± 0.000034 (2 S.E. standard error) was accordingly recalculated at that date and corresponds to an ε Hf (t) of 6.6 ± 1.2 (Fig. 3.13). 3.5.7 Interpretation of U-Pb-Hf data Protolith emplacement ages Both samples show a largely dominant population of Figure 3.13: Measured ε at c. 360 Ma and a66 yielded a 207 Pb/ 206 Pb date of 460 ± 22 Ma, regarded as the grains having statistically equivalent and concordant 206 Pb/ 238 U dates of c. 545 Ma. As RV2 Thirty-three analyses were performed on 25 grains. A Concordia date of 543.9 maximal zircon crystallization age. CL images do not provide clear evidence for: (i) these zircons feature typical magmatic oscillatory zoning (Corfu et al., 2003), we interpret ± 4.6 Ma can be calculated out of 19 statistically equivalent concordant analyses (with a MSWD of concordance and equivalence equal to 1.4). Spot a58 yielded an identical of common Pb yielded concordant to moderately discordant 206 Pb/ 238 U dates (concor-CL-imaging yielded 206 Pb/ 238 U dates of c. 545 Ma (see for instance zircon 1, Fig. 3.11b). 206 Pb/ 238 U date but is discordant (concordance of 87%). Nine measurements devoid the existence of textural discontinuities associated with new zircon growth; (ii) extensive the Concordia dates of 545.9 ± 4.7 and 543.9 ± 4.6 Ma as the emplacement ages of the tonalite protoliths of samples RV-1 and RV-2, respectively. The zircon cores identied by zircon recrystallization (zircon
	As a result, those cores likely reect stepwise mineral growth with periods of dissolution dance>91%) ranging from 536 ± 6 down to 520 ± 6 Ma. Two analyses (a50 and a60) with low to moderate common Pb contents (0.30.8%) show discordant (conc.: 5867%) followed by new zircon crystallization within the magma. This would generate textural
	discontinuities as observed when new magmatic zircon crystallizes around older, source-and younger 206 Pb/ 238 U dates of 484 ± 5 and 438 ± 7 Ma respectively. Two measure-ments performed on both tips of a single zircon yielded a concordant 206 Pb/ 238 U date of inherited grains. UPb evidence clearly suggests that the (meta)tonalite magma did not
	contain inherited grain or, if so, that they were fully dissolved prior to new magmatic 361 ± 4 Ma and a discordant 206 Pb/ 238 U date of 354 ± 4 Ma (estimated common Pb content: 0.4%), respectively. Both also feature markedly lower Th/U ratios (0.02 and zircon crystallization. Discordant zircons showing 206 Pb/ 238 U dates around 545 Ma are
	0.04 respectively) than grains yielding 206 Pb/ 238 U dates of c. 545 Ma (always >0.15). texturally similar to the concordant ones and their discordance would stem from the
	incorporation of common Pb as evidenced in some cases by the high signal on mass 204,
	reecting elevated 204 Pb content. Similarly, discordant zircons with 206 Pb/ 238 U dates 3.5.6 Zircon LuHf isotope signature younger than 545 Ma likely experienced a combination of common Pb incorporation and
	In situ zircon Lu-Hf isotope measurements were performed at Frankfurt-am-Main (Ger-Pb loss, which respective contributions cannot be retrieved. Two spots show younger
	many) following the analytical procedure reported Appendix B.4.1. The full set of results concordant 206 Pb/ 238 U dates of 536 ± 10 and 515 ± 6 Ma respectively (a20 and a30). I
	(standards and samples) is available in Tables B11 and B12. argue that these dates do not correspond to any geological event because the weak cur-
	Twenty-eight spots were drilled on grain domains that previously yielded concordant vature of the Concordia for the 600-400 Ma period entails that any c. 545 Ma-old zircon
	206 Pb/ 238 U dates and three on undated grains texturally identical to the main zircon having experienced limited Pb loss would still be sub-concordant within uncertainty.
	population. Initial Hf isotope compositions were calculated using the intrusion age de-
	termined for each sample except for spot 59a which features a younger 206 Pb/ 238 U date Signicance of younger dates Of interest are analyses a65 and a66, both performed
	of 361 Ma. The 176 Hf/ 177 Hf(t) ratios of RV-1 zircons range from 0.282709 ± 0.000042 on the tips of the same zircon grain. They show younger 238 U/ 206 Pb dates that cannot be
	to 0.282752 ± 0.000035 (2 S.E. standard error), corresponding to ε Hf (t) of 9.5 to 11.0 attributed to Pb loss from the main c. 545 Ma-old population. Indeed, a65 is concordant

Table 1

 1 List, nature and sampling localities of the investigated samples of Variscan igneous plutonic rocks from the eastern FMC, together with existing age data and results of zircon and monazite U-Pb dating performed in this study Sample

	Prob g C h M h I h N h Z h		0.87 7 17 5 22 19		0.78 5 20 8 28 25		0.98 8 33 -33 28					0.34 6 13 25 38 35	0.36 6	0.82 6 6 19 25 19			0.99 5 15 15 30 28	0.60 8	0.88 4 18 31 49 39	0.10 5	0.47 11 19 7 26 26		0.03 27 32 -32 30		0.38 13 24 2 26 24		0.03 26 31 -31 30	0.09 10 11 21 32 32	0.10 7	0.03 16 29 2 31 23
	±2σ MSWD g	2.0 0.58		1.3 0.62		2.0 0.39					1.1 1.12	1.2 1.10	2.3 0.61			1.7 0.25	0.9 0.86	2.6 0.44	1.3 1.60	1.8 0.99		1.2 1.40		0.9 1.06		0.7 1.40	1.3 1.50	1.5 1.50	1.0 1.50
	Age (Ma) f		332.0		325.7		312.9					311.0	309.3 i	312.7			314.5	315.4 i	318.3	317.8 i	336.9		321.2		302.5		332.1	302.8 i	334.9 j	337.4
	Group e		3		3		2					3		3			3		3		3		1		2		1	3	2
	Method d				Rb/Sr WR		U/Pb Zrn	(TIMS)	Rb/Sr WR	U/Pb Mnz	(TIMS)	U/Pb Mnz	(TIMS)	U/Pb Mnz	(TIMS)						Rb/Sr WR		U/Pb Zrn	(LA)			U/Pb Mnz	(LA)
	Lat. N Long. E Literature Ref. d	age (Ma) c	45°42′15″ 3°52′07″		± 14 1 45°45′50″ 3°46′23″ 329	± 9 2 44°40′28″ 3°26′01″ 334	± 12 3 ± 4 4 323 314	± 4 5 44°43′42″ 3°40′26″ 305	± 14 6 44°49′07″ 3°42′43″ 305		45°18′16″ 3°46′44″		45°19′37″ 3°41′20″		± 26 7 45°40′18″ 3°38′45″ 330	± 2 8 45°31′48″ 3°59′09″ 313	44°20′06″ 3°52′30″		45°19′44″ 4°06′08″	± 1.4 9 45°19′44″ 4°06′08″ 305.9	45°47′02″ 4°18′25″
	Type a Pluton/local-Encl. b	ity	CPG Chalmazel y		MPG Hermitage n		CPG Margeride n					MPG Grandrieu n		MPG St-Chris-n	tophe-	d'Allier	CPG Almance n		CPG Chaise-Dieu n		CPG St-Dier-n	d'Auvergne	KCG Gumières y		KCG Pont-de-n	Montvert	KCG Pont-Rouge y	quarry	CPG Pont-Rouge n	quarry	KCG Salt-en-n	Donzy
	Nature		Porph. Bt	granite	Bt-Ms leu-	cogranite	Porph. Bt-	Crd granite				Bt-Ms leu-	cogranite	Bt-Ms leu-	cogranite		Bt granite		Porph. Bt-	Crd granite	Bt granite		Bt-Am Qz-	diorite	Porph.	Bt-Am	granite	Bt-Am	granodi-	orite	Bt-Crd	granite	Bt granite
			CHZ		HER		OL-13-06					OL-13-08		OL-13-09			OL-13-11		OL-13-14		OL-13-21		OL-13-24		PMV		PRC-56	PRC-57	SDZ

  U/206 Pb age (with ±2σ uncertainty, in Ma). Each zircon grain is labeled with the sample it was extracted from and its number in this sample (zXX). Values with an asterisk indicate 207 Pb/ 206 Pb ages; labels in italics indicate >5% discordance. The yellow circles and font highlight analyses with large amounts of common 204 Pb (>5%); the red circle and font indicate an analysis (a27) from which no reliable age could be obtained because of high discordance and common Pb contents, and that was therefore discarded. The scale bar is 100 µm

	430	Int J Earth Sci (Geol Rundsch) (2017) 106:421-451
	1 3

(d) Sample LR-31 (V) Concordia Age = 299.1 ± 1.3 Ma

		0.054		data-point error ellipses are 2σ	0.053		data-point error ellipses are 2σ
			Concordia Age = 306.1 ± 1.3 Ma
		0.052	MSWDC+E = 1.04 ; Prob.C+E = 0.39 n = 20			0.051	MSWDC+E = 0.75 ; Prob.C+E = 0.85 n = 17	320
				320
								310
		0.050				0.049
	206Pb/238 U	0.048			206 Pb/ 238 U	0.047	290 290
		0.046				0.045	280
		0.044				0.043	270
		0.042 0.30	0.33	0.36	0.39	0.041 0.29	0.32	0.35	0.38
			207 Pb/ 235 U				207 Pb/ 235 U

(c) Sample SGC-12-26 (V)

	0.057			data-point error ellipses are 2σ	0.056			data-point error ellipses are 2σ
	0.055			340			0.054			340
	0.053
							0.052
	0.051					206 Pb/ 238	0.050
	0.049							310
	0.047						0.048	300
	290
	0.045 0.32	0.34	0.36	0.38	0.40	0.42	0.046 0.33	0.35	0.37	0.39	0.41	0.43
									207 Pb/ 235 U
					330
		290 290
		280 280
	270

U (

b) Sample PRC-56 (KCG)

	206 Pb/ 238
	207 Pb/ 235 U

U (

a) Sample OL-13-24 (KCG)

	Concordia Age =	350
	300 300

321.2 ± 1.2 Ma

	432	Int J Earth Sci (Geol Rundsch) (2017) 106:421-451
		Conc. Age = 332.1 ± 0.7 Ma	350
	MSWDC+E = 1.4 ; Prob.C+E = 0.03	MSWDC+E = 1. ; Prob.C+E = 0.03
	n = 27	n = 26
		320 320
	Fig. 4 Representative U-Pb Concordia diagrams ( 206 Pb/ 238 U vs.	ant analyses from zircon rims or crystals devoid of any core (exclud-
	207 Pb/ 235 U) showing examples of zircon analyses from samples of	ing outliers), used for the calculation of the Concordia Age. The
	"group 1" (V = vaugnerite), i.e., showing a single generation of zir-con dates with mostly identical 206 Pb/ 238 U ratios within uncertainties	dashed ellipses represent analyses with >5% of common 204 Pb. All ages are quoted to 2σ level of uncertainty
	(see "Discussion"). Green ellipses are the oldest, equivalent concord-
	1 3

(b) Sample SDZ (KCG) Concordia Age = 337.4 ± 1.0 Ma

		0.056			data-point error ellipses are 2σ	0.057				data-point error ellipses are 2σ
			Concordia Age =				0.054	n = 16 MSWDC+E = 1.50 ; Prob.C+E = 0.03			350
		0.050					0.051	n = 29 Upper intercept = 337 ± 2 Ma MSWD = 1.03		320 320
	206 Pb/ 238 U	0.044				206 Pb/ 238 U	0.045 0.048		280	300	0.090	0.094 550	570	n = 2) a504 590
		0.038					0.042	260 260		0.086	530
							0.039			510	a513
		0.20 0.032	0.26 ± 1 6 2 7	0.32	0.38	0.44	0.036 0.26	0.30	0.34 0.64 490	0.68	0.38 0.72	0.76	0.42
				207 Pb/ 235 U					207 Pb/ 235 U

312.9 ± 2.0 Ma

	(
	MSWDC+E = 0.39 ; Prob.C+E = 0.98	340
	n = 8
	260
	Upper intercept = 321 ± 11 Ma
	220	MSWD = 0.55
		n = 27 (+3 not shown)

a) Sample OL-13-06 (CPG)

	300 300
		0.059				data-point error ellipses are 2σ
		0.056				350
	206 Pb/ 238 U	0.050 0.053		320
		0.047
		0.044 0.32	0.34	0.36	0.38	0.40	0.42
				207 Pb/ 235 U

(d) Sample SC-13-19 (V) Concordia Age = 333.9 ± 1.4 Ma

	0.057				data-point error ellipses are 2σ
	0.054				330		MSWDC+E = 0.92 ; Prob.C+E = 0.60 n = 17
							Upper intercept = 334 ± 3 Ma
	0.051						MSWD = 0.88 n = 26
	0.048
			290
	0.045
										310 310
	0.042							300
	0.039 0.036 0.26	1 6 0 0.29 ± -4 7	0.32	0.35	0.38	0.41	290	-3 0 0	±	2 9 0

(c) Sample PRC-53 (V)

	Concordia Age = 318.9 ± 1.8 Ma
	MSWDC+E = 0.48 ; Prob.C+E = 0.98
	n = 11
	Upper intercept = 330 ± 12 Ma
	MSWD = 1.50
	n = 22	310 310
	206 Pb/ 238 U
	270 270
	250 250
	207 Pb/ 235 U
	Fig. 5 Representative U-Pb Concordia diagrams ( 206 Pb/ 238 U vs.
	207 Pb/ 235 U

b) Sample TN-10 (CPG)

	434									Int J Earth Sci (Geol Rundsch) (2017) 106:421-451
	0.060				data-point error ellipses are 2σ		0.055					data-point error ellipses are 2σ
					360				Conc. Age = 321.9 ± 1.3 Ma MSWDC+E = 1.6 ; Prob.C+E = 0.11 n = 5	330
								0.051	Upper intercept = 320 ± 12 Ma
									MSWD = 1.13			310 310
	0.054								n = 27
	206 Pb/ 238 U				0.24 1200 Cores & Xen. a227 (n = 7)	206 Pb/ 238	0.043 0.047			270	290 290	0.16	950 Cores & Xen. a172 a188 (n = 7)
	0.048		0.16	900								0.14	850
	280	± 3 2 0	0.08	600	a220			0.039	230	2 1 0 250 250		0.10	550 0.12 a200 a184	650	750 a179
		-7 2	300	1	2	3				2 7 ±			0.6	a191	1 .0	1.4
	0.042 0.30	0.34	0.38		0.42	0.46		0.035 0.24	0.27	0.30	0.33	0.36	0.39	0.42
			207 Pb/ 235 U								207 Pb/ 235 U
	1 3

U (

(a) Sample OL-13-21 (CPG) Concordia Age = 336.9 ± 1.8 Ma

	MSWDC+E = 0.99 ; Prob.C+E = 0.47
	n = 11
	Upper intercept =
	336 ± 11 Ma
	MSWD = 0.39
	n = 19
	320 320
	300 300
	a231
	a215
	a208
	0.060		data-point error ellipses are 2σ
	0.050
	0.040
	0.030		0.10
			0.08
	0.020
			0.06
			0.5	0 .7
	0.010 0.1	0 .2	0.3	0 .4	0.5

(d) Sample OL-13-11 (CPG) Concordia Age = 314.5 ± 1.7 Ma

		0.056					data-point error ellipses are 2σ
				Concordia Age = 321.1 ± 1.1 Ma MSWDC+E = 1.17 ; Prob.C+E = 0.07			MSWDC+E = 0.25 ; Prob.C+E = 0.99	340
				n = 6			330		n = 5
		0.052	Upper intercept = 321 ± 6 Ma MSWD = 0.15 n = 14				Upper intercept = 315 ± 48 Ma MSWD = 0.20 n = 15	280
	206 Pb/ 238 U	0.048		290		310 310			206 Pb/ 238 U			220	600 Cores & Xen. (n = 13 + 2 not shown)
												160	500
		0.044										a131
				270								400	a139
									100
		0.040 0.28	± 1 1 0 -3 7 0.30 0.32	0.34	0.36	0.38	0.40	0.42	-5	±	6 6	300
					207 Pb/ 235 U						207 Pb/ 235 U

(c) Sample TN-19 (CPG)

								Cores & Xen.
							(n = 16 + 1 not shown)
									700
								a215
					0.10		600 a207
							a224
								a227
				0.08	a214	500
							a233
				a220
				400	0.6	a221	0 .8
	0.056									0.054
	0.052									0.051			320
										0.048		300
	0.048
	0.044				0.11			206 Pb/ 238	0.045				0.16	900
										0.042			0.12	700
	0.040	6 8		0.07						0.039	240	0.08	500
	0.036 0.26	-2 6 ±	0.30	0.34	0.5		0.38 1 .0	0.42	0.24 0.036	0.27 10 ± 120 0.30	0.33 300	0.36 0.8	0.39	1 .6	0.42
												207 Pb/ 235 U

U (

f) Sample OL-13-08 (MPG) Conc. Age = 311.0 ± 1.1 Ma

			data-point error ellipses are 2σ
	Concordia Age =
		MSWDC+E = 1.12 ; Prob.C+E = 0.34
		n = 5	320
		Upper intercept = 314 ± 10 Ma
		MSWD = 0.10
		n = 11 (+2 not shown)	300
	800	a272	280
	600
		260
	400
		240
	200

325.7 ± 1.3 Ma

	MSWDC+E = 0.62 ; Prob.C+E = 0.78
	n = 5
	Upper intercept = 323 ± 7 Ma
	MSWD = 0.51
	n = 19 (+1 not shown)
	206 Pb/ 238
	207 Pb/ 235 U

U (

e) Sample HER (MPG)

	data-point error ellipses are 2σ
	340
	300
	260

  Our results from samples in this area show emplacement ages scattered over more than 20 Ma, and specifically clustered at 321-319 Ma (age of the two quartz-syenite enclaves within the Velay granite at Pont-Rouge (PRC-53 and PRC-54), 310 Ma (Pubellier syenodiorite, SC-13-09) and 302-299 Ma (diorite enclaves in the Velay granite;. Two vaugnerite enclaves within the Margeride batho-

lith (SC-13-02a and SC-13-05) yielded ages (313-309 Ma) that are identical within uncertainties to the emplacement age of the surrounding Margeride granite (312.9 ± 2.0 Ma; sample OL-13-06), supporting field observations indicating that the vaugnerites are coeval with the granite. Finally, to the south of the Velay complex, vaugnerite samples from Loubaresse (SGC-12-39) and Meyras (SGC-12-42) yield ages of 306.6 ± 1.6 and 305.9 ± 1.7 Ma, respectively, which are identical to those of

Couzinié et al. (2014)

for the same vaugnerite bodies (307.4 ± 1.8 and -305.8 ± 2.3 Ma, respectively; U-Pb zircon by LA-ICP-MS). The age obtained on the Meyras vaugnerite is also identical to that of Aït Malek (1997) (308 ± 6 Ma; U-Pb zircon by ID-TIMS), but this author obtained a significantly older age for the Loubaresse vaugnerite (313 ± 3 Ma; see

Couzinié et al. 2014 for discussion)

. The Pontde-Bayzan vaugnerite gave an emplacement age of 306.1 ± 1.3 Ma

. This age is significantly older than the age of 294.4 ± 3.9 Ma published by

Couzinié et al. (2014)

from the same outcrop, but from a different vaugnerite body. The latter, Permian age would not reflect the crystallization age, due to perturbation of the zircon U-Pb isotopic system by fluidrock interactions

Table 1

 1 Summary of the main documented occurrences of PCMM in the geological record.

	Orogen	Age of PCMM	Specific nomenclature	Differentiates	Proposed references
	Late Archean terranes	2950 to 2500 Ma	Sanukitoid	Sanukitoid suite	Laurent et al. (2014a)
	Svecofennian (Scandinavia)	1800 Ma	Ladogite, Nevoite	Post-kinematic granitoids	Rutanen et al. (2011)
	Pan-African	620-560 Ma	Sanukitoid	High-K calc-alkaline (HKCA)	Liégeois et al. (1998)
				granitoids
	Ross (Antarctica)	515-500 Ma	No specific name given	No specific name given	Hagen-Peter et al. (2015)
	East Kunlun (China)	c. 450 Ma	Appinite	Not described	Xiong et al. (2015)
	Caledonian	425-410 Ma	Appinite	High Ba-Sr granites	Fowler and Rollinson (2012)
	Central Asian Orogenic Belt	425 to 300 Ma	Sanukitoid	Not described	Yin et al. (2015)
		(several pulses)
	Variscan	335-300 Ma	Vaugnerite, Durbachite,	Felsic durbachites; K-rich calc-alkaline	Moyen et al. (in press);
			Redwitzite, Appinite	granitoids (KCG)	Holub (1997); von Raumer
					et al. (2014)
	North China Block assembly	320 to 115 Ma	Appinite	Post-collisional granitoids	Zhao et al. (2013)
	(Dabie-Sulu orogen. . . )	(several pulses)
	Himalaya	20 to 3 Ma	Post-collisional (ultra)potassic	(Ultra)potassic silicic magmas	Williams et al. (2004)
			magmas

Table 2

 2 Summary of zircon Lu-Hf-O isotope data from post-collisional mafic magmatic rocks of the French Massif Central obtained in the course of this study. Main geochemical features of post-collisional mafic magmatic rocks with special emphasis on the eastern FMC example (blue triangles). Each grey field illustrates the range of composition for similar rocks from other orogenic systems (data from TableS6). Plots of (a) K 2 O vs. SiO 2 concentrations (the different series are after Peccerillo and Taylor, 1976); (b) K 2 O vs. MgO + FeO t concentrations; (c) Large Ion Lithophile Elements (Ba + Sr) vs. transition element (Ni + Cr) concentrations and (d) sum of LREE (La + Nd + Ce) vs. HFSE (Zr + Nb) normalized to Yb; (e) Multi-element diagram normalized to the Primitive mantle (McDonough and Sun

	N o h		20	17	-	-	15	13	16	11	-	23	-	16	Lu/ 177 Hf
	±2 S.D.		0.87	1.75	-	-	0.58	1.19	1.00	0.80	-	0.92	-	1.15	= 0.0336.
															Hf
	δ 18 O g		8.21	8.26	-	-	8.10	7.84	7.85	7.81	-	7.32	-	7.43	Lu/ 177
	T DM2 N Lu-Hf f	(Ga) e	1.58 18	1.62 15	1.58 6	1.59 14	1.45 16	1.46 11	1.39 15	1.38 16	1.41 15	1.41 15	1.45 16	1.49 14	Hf = 0.282785 and 176
	±2σ		3.3	2.5	3.1	2.7	1.2	1.6	1.4	1.4	1.8	1.2	1.5	1.2	Hf/ 177
	eHf(t) d		-6.1	-6.7	-6.2	-6.3	-3.8	-4.1	-2.7	-2.7	-3.2	-3.2	-3.8	-4.7
	Subset c		A	A	A	A	B	B	B	B	B	B	B	B
	±2 S.D.		0.000093	0.000070	0.000088	0.000077	0.000034	0.000045	0.000041	0.000041	0.000051	0.000034	0.000042	0.000034
	b
	avg.
	176 Hf/ 177 Hf		0.282413	0.282395	0.282414	0.282410	0.282483	0.282476	0.282516	0.282521	0.282506	0.282502	0.282485	0.282461
	±2σ		1.8	1.8	2.5	1.5	1.2	1.6	1.3	1.3	1.4	1.3	1.6	1.7
	Rock type (TAS, Locality Lat. N Long. E U-Pb age	Middlemost, 1994) (Ma) a	Quartz Syenite Pont-Rouge quarry 45 • 19 47 4 • 06 05 318.9	Quartz Monzonite Pont-Rouge quarry 45 • 19 47 4 • 06 05 320.5	Quartz Monzodiorite Moulin de Linas 44 • 41 14 3 • 28 25 313.2	Monzodiorite L'Aldeyres 44 • 45 53 3 • 37 53 309.4	Quartz Monzodiorite Pubellier 45 • 13 29 3 • 39 33 309.7	Quartz Monzodiorite Lamastre 44 • 58 24 4 • 37 41 307.8	Diorite Lamastre 44 • 58 24 4 • 37 41 307.3	Quartz Diorite La Roche 45 • 17 05 4 • 06 50 299.1	Diorite La Roche 45 • 17 05 4 • 06 50 301.5	Monzodiorite Pont-de-Bayzan 44 • 39 28 4 • 18 24 306.1	Quartz Monzodiorite Loubaresse 44 • 36 02 4 • 04 14 306.6	Monzodiorite Meyras 44 • 40 21 4 • 16 26 305.9	Hf of 0.0384 and 0.28325, respectively, for evolution of the depleted mantle source.
	Sample		PRC-53	PRC-54	SC-13-02A	SC-13-05	SC-13-09	533-1	533-2	LR-31	LR-32	SGC-12-26	SGC-12-39	SGC-12-42	and 176 Hf/ 177

a U-Pb intrusion age obtained by Laurent et al. (2015). b Average 176 Hf/ 177 Hf ratio at the time of intrusion, calculated using the U-Pb intrusion age of the sample. c Subset determined from Hf isotopes (see text). d Calculated at the time of intrusion using the parameters of the Chondrite Uniform Reservoir (CHUR) recommended by Bouvier et al. (2008), i.e. present-day values of 176 e Two stage model age in billion years using the measured 176 Lu/ 177 Hf of each spot (first stage = age of zircon), 176 Lu/ 177 Hf of 0.0113 for the average continental crust (second stage) (Taylor and McLennan, 1985), and 176 f Number of individual Lu-Hf spots used in the calculation of the initial Hf isotope composition. g Average δ 18 O of the sample. h Number of individual O spots used in the calculation of the O isotope composition. 186 S. Couzinié et al. / Earth and Planetary Science Letters 456 (2016) 182-195 Fig. 2.

  . PCMM have contributed to crustal growth since the late Archean because they are the parent of voluminous granitoid suites and have a high preservation potential in the geological record. Owing to their peculiar hybrid origin, this contribution cannot be resolved in global crustal growth models based only on zircon Hf and O isotopes, such that post-Archean crustal growth may be significantly under-estimated.

	5.4 Additional discussion on the source of crust-derived gran-
	ites
	5.4.1 Rationale
	Moyen et al. (2017a) argued that the chemical dierences between MPG and CPG gran-
	ites result from both: (i) contrasted sources and (ii) dierent TX H 2 O melting conditions
	and thus melting reactions. The MPG would have formed by water-present melting or
	muscovite-dehydration melting of metasediments while the CPG would correspond to
	higher-T magmas, generated by biotite-dehydration melting of a quartzo-feldspathic (or-
	thogneiss) source. However, CPG and MPG share the same inherited zircon age pattern
	(Laurent et al., 2017) which is inconsistent with dierent magma sources. It rather sug-
	gests that chemical variations arose solely from petrogenetic processes i.e. contrasted
	melting temperatures/reactions, variable extent of peritectic assemblage entrainment,
	restite unmixing (see Clemens and Stevens, 2012).
	Laurent et al. (2017) attempt to identify the source material of MPG/CPG granites
	by comparing their inherited zircon age distribution to the respective patterns of meta-
	1. PCMM are ubiquitous in all continental collision settings since
	the late Archean and are characterized by a dual geochemistry,
	with high contents in both compatible, "mantle-hosted" ele-
	ments (FeO t + MgO, Ni, Cr) and incompatible, "crust-hosted"
	elements (LILE, REE, HFSE).
	2. As illustrated by the case study from the eastern FMC, PCMM
	originated from low-degree partial melting of a phlogopite-
	(and/or amphibole-) bearing peridotite/pyroxenite. In the FMC,
	the non-radiogenic εHf (t) (-2 to -9) and elevated δ 18 O SMOW
	(+6 to +10h) of PCMM zircons suggest that this mantle
	source was contaminated by 10 to 25% of subducted conti-
	nental shelf sediments derived from Precambrian crust, shortly
	prior to melting.

3. Mass balance calculations indicate that the incompatible trace element budget (including radiogenic isotope tracers Sr, Nd, Hf, Pb) of the PCMM source is mainly controlled by the crustal component. Therefore, resulting magmas display "crust-like" non-radiogenic isotope compositions even though 62 to 85% of their bulk mass originates from the mantle component and represents new addition to the crust.

4

igneous and metasedimentary rocks from the FMC. At the time the paper was written, such approach suered from the scarcity of available zircon ages on the eastern FMC basement. This led the authors to use a (limited) dataset from the western FMC which pre-Variscan evolution markedly contrasts with that inferred for the eastern FMC (see

Chapter 4)

. A better knowledge of the nature, zircon age distribution and Hf isotope composition of the eastern FMC constituent lithologies has been gained over the past two years and allows to put further constraints on the nature of the reworked materials during the Variscan orogeny.

Table 6 .

 6 1: Summary of available structural data in the Cévennes schists.

  are provided in TablesB4B6 and B7B9, respectively. The comprehensive description of the UPb results for each sample is presented section B.3.4.Monazites from samples were extracted from the same powder fraction than zircon grains and similarly cast into epoxy mounts while those from CHA-15-17 and CHA-15-25 were identied on rock thin sections using a Zeiss MERLIN SEM-EDX. All grains were BSE-imaged at SUN using the same apparatus. Selected monazites were dated by the UPb LAICPMS method at the Laboratoire Magmas et Volcans inClermont-Ferrand (France). Analytical details are available sections B.5. The full set of data is provided TablesB15 and B16. All zircon

	Concordia or Intercept dates were calculated considering systematic errors as explained
	section 1.5.1.
	6.3.3 Zircon textures, UPb dates and their interpretation
	Orthogneisses
	Zircon grains extracted from orthogneiss samples are euhedral to sub-euhedral, range in
	size from 80 to 400 µm, Villefort granites
	Zircon grains show a broad range of sizes (60350 µm) and aspect ratios (1.13.6). Core
	rims relationships are observed in c. 50% of the imaged grains and two zircon types can
	be recognized. Most feature a CL-dark or bright occasionally zoned core, truncated by a
	new growth zone with distinct magmatic oscillatory zoning, similar to zircons extracted
	from orthogneisses. A second, scarce type correspond to zoned grains wrapped around by
	a poorly luminescent and porous rim (see zircon 6, Fig. 6.18b). Concordant 206 Pb/ 238 U
	2.1, subsequently cast into epoxy dates obtained from cores and rims are exclusively pre-Variscan, dominantly Ediacaran.
	mounts and polished down to an equatorial grain section. BSE and CL-imaging were per-CL-dark rims are rich in common Pb and no concordant date was retrieved.
	formed at the Central Analytical Facility of Stellenbosch University (SUN, South Africa) Most zircons devoid of corerim relationships also yielded pre-Variscan (mostly Edi-

using a Zeiss MERLIN SEM and at the Laboratoire Magmas et Volcans in Clermont-Ferrand (France) using a Jeol JSM-5910 SEM. Selected grains were dated by LAICP MS in the course of two analytical sessions, one performed at GUF (2 nd and 3 rd of May, 2016) and the other one at ETH (12 th to 14 th of February, 2017). Information on the analytical methods are presented Appendix B.3.1 and B.3.3 while the results of standards and samples measurements display aspect ratios between 1.4 and 3 and show well-developed pyramidal tips (Fig. 6.18a). Corerims relationships are very common and typically feature CL-dark cores (most often unzoned and sometimes recrystallized) surrounded by rims showing magmatic oscillatory zoning. UPb dates retrieved from such rims and homogeneous grains exhibiting a similar zoning pattern are clustered and yield Condordia dates of 544.1 ± 4.9 Ma (MSWD C+E =0.79) and 544.4 ± 5.2 Ma (MSWD C+E =0.9) for CHA-15-35 and CHA-15-52, respectively (Fig. 6.19). Measured Th/U ratios are low (average value of 0.15). In both samples, few measurements yielded a range of younger, nearly discordant, 206 Pb/ 238 U dates down to 514 ± 7 Ma. Finally, analyses performed on zircon cores and additional core-free grains yielded concordant Paleo-and Neoproterozoic dates. Importantly, identical zircon textures, Th/U ratios and UPb dates have been reported by Couzinié et al. (2017) on late Ediacaran meta-granites from the Velay Orthogneiss Formation. Following this, we interpret the Concordia dates obtained for each sample as the emplacement ages of their igneous protoliths. The range of younger 206 Pb/ 238 U dates would represent a recent Pb loss trend. Zircon domains showing older dates would correspond to source-inherited grains or xenocrysts incorporated from country-rocks during magma ascent. Consequently, both samples will be regarded as constituents of the Velay Orthogneiss Formation and not early Variscan granitic intrusions. acaran) dates. Very few gave concordant Variscan UPb dates, often after a common Pb correction was performed (Fig. 6.18b). The Concordia dates of 305.8 ± 4.4 Ma (MSWD C+E =1.5) and 304.0 ± 3.9 Ma (MSWD C+E =1.4) are thus retained as the emplacement ages of the granites CHA-15-24 and CHA-15-41, respectively (Fig. 6.20a to d). One single concordant Variscan grain was analysed in sample CHA-15-49 and yielded an individual 206 Pb/ 238 U date of 305 ± 4 Ma, possibly corresponding to that of magma intrusion. No concordant Variscan date was obtained for CHA-15-25. All zircon domains with pre-Variscan ages would correspond to xenocrysts or source-inherited grains.

  The Borne batholith Zircons from the Borne granite show a large range of sizes, from 80 to 350 µm and shapes (aspect ratios: 1 to 4). They often feature large, CL-dark, heavily recrystallized cores surrounded by rims commonly showing magmatic oscillatory zoning (Fig.6.18f ). Most analyses performed on such rims and core-free grains dene a trend between radiogenic and common Pb compositions (Fig.6.21a). Concordant measurements on this trend yield a Concordia date of 309.7 ± 3.6 Ma (MSWD C+E =1.09), retained as the emplacement age of the Borne granite. It is within error identical to the whole-rock RbSr age of[START_REF] Mialhe | Le massif granitique de la Borne (Cévennes). Etude pétrographique, géochimique, géochronologique et structurale[END_REF]. Spotted zircon cores (avoiding the recrystallized ones) gave a range of concordant 206 Pb/ 238 U dates from 549 ± 6 down to 316 ± 2 Ma regarded as inherited ages. One measurement performed on a rim yielded a younger concordant 206 Pb/ 238 U date of 297 ± 2 Ma that would result from limited Pb loss from the dominant population.

  Textures and UPb resultsLarge (>60 µm) monazite grains were only observed in granite dyke CHA-15-34 and representative BSE images are displayed Fig.6.24. For other samples, analysed grains were very small (often <20 µm) and no clear BSE zoning was identied.Clearly, the Permian dates of c. 272 Ma retrieved from the leucosome cannot be regarded as the crystallization age of the melt fraction in the migmatite. Indeed, UPb apatite dating of Velay migmatites 2030 km east of the study area yielded early Permian c. 290 Ma cooling ages. Furthermore, migmatite pebbles are found in the basal conglomerate of the Prades-Jaujac basin(Bouilhol et al., 2006), which inlling has been dated at 296.0 ± 6.8 Ma (zircon UPb SIMS on bentonite). Therefore, the date of 299.1 ± 2.7 Ma obtained on the metatexite more likely correspond to the migmatite crystal-

	Puylaurent migmatites Samples from the Puylaurent migmatite yielded contrasted
	results. Monazites from melanosome CHA-15-65M are all discordant and show scattered
	206 Pb/ 238 U dates between 326 ± 9 and 294 ± 8 Ma (Fig. 6.25a). Several grains from
	in-source leucosome CHA-15-65L are also discordant but trend along a mixing line be-
	tween radiogenic and common Pb compositions, with a lower intercept at 271.6 ± 3.2
	Ma (MSWD C+E =1.03). A similar 206 Pb/ 238 U weighted average date of 272.5 ± 2.4 Ma
	can be calculated out of the ten analyses (Fig. 6.25). Conversely, monazites from meta-
	texite CHA-15-17 dene an older 206 Pb/ 238 U weighted average date of 299.1 ± 2.7 Ma
	(excluding two measurements, one being highly discordant, Fig. 6.25c).
	Saint-Laurent-les-Bains migmatite Few grains from a single sample were dated.
	lization age. Localized uid circulation would have resulted in the resetting of leucosome
	CHA-15-65L monazites. Scattered 206 Pb/ 238 U dates in the metatexite may indicate suc-
	cessive monazite crystallization events, possibly in line with several melting episodes as
	suggested by

Five analyses (one of them being concordant) dene a mixing trend between radiogenic and common Pb compositions, which lower intercept yields a date of 291.8 ± 4.7 Ma.

Two analyses performed on a grain show older discordant 206 Pb/ 238 U dates between 544 ± 15 and 518 ± 14 Ma (Fig.

6

.25d).

Villefort granite CHA-15-25 Sixteen monazite grains have identical 206 Pb/ 238 U dates with a weighted average of 282.8 ± 2.2 Ma. Those dene a mixing trend between radiogenic and common Pb with a lower intercept at 282.4 ± 2.4 Ma. Two discordant spots yielded older 206 Pb/ 238 U dates of 309 ± 10 and 359 ± 11 Ma (Fig.

6

.25e).

Post-tectonic granite dyke CHA-15-34 BSE images of monazites from this sample reveal sector zoning (and possibly oscillatory concentric zoning in monazite 1, Fig.

6

.24).

All spotted domains show identical 206 Pb/ 238 U dates, even though 10 analyses out of 16 are discordant. A weighted average 206 Pb/ 238 U date of 275.7 ± 1.9 Ma can be calculated (Fig.

6

.25f ).

Interpretation of monazite dates

Migmatites A striking feature of the Puylaurent migmatites lies in the fact that samples taken less than 20 m away from each other yielded very dierent date patterns.

  . The older monazite grain, showing late Ediacaranearly Cambrian 206 Pb/ 238 U dates, is regarded as inherited from the migmatite protolith i.e. the Velay Orthogneiss Formation. Similar inherited monazite grains in the Velay migmatites and granites have been described byBe Mezeme et al. (2006) andDidier et al. (2013).Importantly, LAICPMS monazite ages obtained in the course of this study are notably younger than the "chemical" UThPb ages reported byBouilhol et al. (2006) and BeMezeme et al. (2006) for both the Puylaurent and Saint-Laurent migmatites, spanning between 329 ± 5 and 310 ± 2 Ma. Those datasets were obtained following the procedure ofCocherie et al. (2005) and the statistical scheme developed by Cocherie and Albarede (2001) which eciency has recently been challenged[START_REF] Poujol | Two-stage partial melting during the Variscan extensional tectonics (Montagne Noire, France)[END_REF].Besides,[START_REF] Poujol | Two-stage partial melting during the Variscan extensional tectonics (Montagne Noire, France)[END_REF] and[START_REF] Trap | Timing and duration of partial melting and magmatism in the Variscan Montagne Noire gneiss dome (French Massif Central)[END_REF] noticed that it tends to yield older ages than those obtained by LAICPMS monazite dating. In our case study, most monazite analyses happened to be discordant, presumably as a result of common Pb incorporation. Therefore, the presence of non-radiogenic Pb in the monazite matrices, undetectable with a microprobe, would adequately explain the older ages retrieved byBouilhol et al. (2006) and BeMezeme et al. (2006) in the migmatites.

Villefort granite CHA-15-25 The weighted average 206 Pb/ 238 U date of 282.8 ± 2.2 Ma may correspond either to the crystallization age of the granite sill or the age of postmagmatic uid circulation. The second possibility is supported by: (i) the location of the sample within the Villefort Shear Zone which activity continued under brittle conditions, likely to drain a range of deep to shallow crustal uids; (ii) the very small size of monazite grains (mostly <20 µm in length), making them prone to recrystallization/resetting; (iii) the existence of crystals yielding older 206 Pb/ 238 U dates of 309 ± 10 and 359 ± 11 Ma, respectively, which may have escaped the localized uid inux; (iv) eld observations

  Granite dyke CHA-15-34 The 206 Pb/ 238 U date of 275.7 ± 1.9 Ma is regarded as the crystallization age of the granite dyke because of the typical oscillatory concentric zoning displayed by one monazite grain (see Fig.6.24) and the lack of evidence for a pervasive uid inux able to reset 80 µm-large grains. Interestingly, BeMezeme et al. (2006) report crystallization ages between 333 ± 6 to 318 ± 5 Ma for several granite dykes in and around the Masméjean dome. Unfortunately, these authors did not quote the exact GPS coordinates so that the actual nature of the dated samples remains unclear and cannot be directly compared to our results. The obtained Permian age is identical to a whole-rock RbSr age reported for the late Pont-de-Chervil granite, cropping out in the eastern part of the Velay dome (274 ± 7 Ma,[START_REF] Caen-Vachette | Ages radiométriques des granites anatectiques et tardimigmatitique du Velay (Massif Central français)[END_REF].

	6.3.5 Summary

Fig.

6

.26 presents a summary of the geochronological data gained in the course of this study. The new age obtained on the Rocles granite conrms that regional D 2v top-to- the NE shearing is as old as c. 320 Ma. Following the conclusion of the AMS study, the c. 305 Ma emplacement ages of the Villefort granites indicate that the Villefort Shear Zone was active by that time. An identical age was retrieved for the granite sill CHA-15-19, pre-dating brittle-ductile top-to-the S shearing. The Borne granite yielded a statistically older intrusion age than its presumed counterpart on the western side of the VSZ: the Pont-de-Montvert batholith (309.7 ± 3.6 vs. 302.5 ± 3.5 Ma, taking into account systematic errors). Emplacement of the ne-grained, porphyritic, granite sill CHA-15-33 at 302.8 ± 3.7 Ma entails that the Sil-zone of the Masméjean dome mantle had already signicantly cooled down by that time. Metatexites from the dome core would have crystallized at c. 300 Ma, at the CarboniferousPermian boundary. Permian ages mostly attest to uid circulations but also to emplacement of late granite dykes.

  . A TX H 2 O pseudosection at this pressure (not shown) indicates that 0.53 wt.% H 2 O in the bulk is necessary to reach full hydration. The retained chemical composition is displayed Table 6.2.

	Sample	SiO 2	Al 2 O 3	FeO	MgO	CaO	Na 2 O	K 2 O	TiO 2	H 2 O
	SC 14 33	72.56	14.90	2.02	0.40	0.76	3.12	5.52	0.19	0.53

Table 6.2: Chemical composition of the representative augen gneiss sample used for modelling.

  , OG-1 (weighted mean 206 Pb/ 206 Pb age = 3465.4 ± 0.6 Ma; Stern et al., 2009), and BB (DEGO: weighted mean 206 Pb/ 238 U age = 560 ± 0.8 Ma; Santos et al., in press), and the standard monazites Moacir (mean 207 Pb/ 235 U age = 504.3 ± 0.2 Ma, Gasquet et al., 2010), Manangoutry (mean 206 Pb/ 238 U age = 554.8 ± 3.8 Ma; Horstwood

  ). From zircon rims or devoid of any cores, 11 spots were obtained and have Permian to Carboniferous 206 Pb/

		0.060	(a) Sample OL-13-21					data-point error ellipses are 2σ		0.055	(b) Sample TN-10	data-point error ellipses are 2σ
			Concordia Age = 336.9 ± 1.8 Ma MSWDC+E = 0.99 ; Prob.C+E = 0.47 n = 11			360				Conc. Age = 321.9 ± 1.3 Ma MSWDC+E = 1.6 ; Prob.C+E = 0.11 n = 5	330
			Upper intercept = 336 ± 11 Ma										0.051	Upper intercept = 320 ± 12 Ma MSWD = 1.13	310 310
	206 Pb/ 238 U	0.048 0.054	300 300 MSWD = 0.39 n = 19	320 320	0.16		900	0.24 1200 Cores & Xen. a227 (n = 7)	206 Pb/ 238 U	0.043 0.047	n = 27		270	290 290	0.14	0.16	850 Cores & Xen. 950 a188 a172 (n = 7)
																	250 250	0.12	750
			280	-7 2 ± 3 2 0		300 0.08	600	1	a215 a208 a220 a231	2	3		0.039	230	2 7 ± 2 1 0	0.10	0.6 550 a200 a184	a191 650	1.0	a179	1.4
		0.042													0.035
		0.30	0.34	0.38					0.42	0.46		0.24	0.27	0.30	0.33	0.36	0.39	0.42
						207 Pb/ 235 U										207 Pb/ 235 U
		0.056	(c) Sample TN-19					data-point error ellipses are 2σ		0.056			data-point error ellipses are 2σ
			Concordia Age = 321.1 ± 1.1 Ma MSWDC+E = 1.17 ; Prob.C+E = 0.07							Concordia Age = 322.2 ± 1.5 Ma MSWDC+E = 0.47 ; Prob.C+E = 0.98	340
			n = 6							330					n = 10
		0.052	Upper intercept = 321 ± 6 Ma MSWD = 0.15										Upper intercept = 326 ± 11 Ma MSWD = 0.27
			n = 14												0.051	n = 22
	206 Pb/ 238 U	0.048			290	310 310		0.10		600 Cores & Xen. 700 (n = 16 + 1 not shown) a215 a207	206 U Pb/ 238				300 300	0.13 700	800
															0.046
										a224								600
		0.044		270		0.08		a214	500			a227					280	0.09 500
										a233
		0.040		-3 7 ± 1 1 0	a220 400	0.6	a221	0.8			0.041	260	5 3 ± 1 5 0	400	0.6	1.0	1.4
		0.28	0.30	0.32	0.34	0.36		0.38	0.40	0.42		0.28	0.30	0.32	0.34	0.36	0.38	0.40	0.42
						207 Pb/ 235 U										207 Pb/ 235 U
		0.057								350 data-point error ellipses are 2σ		0.052	Conc. Age = 302.8 ± 1.3 Ma	data-point error ellipses are 2σ 325
		0.055													0.051	MSWDC+E = 1.50 ; Prob.C+E = 0.09 n = 10
		0.053													0.050
		0.051													0.049
												800
		0.049							0.13					0.048
											700
		0.047							600					0.047			295
						0.09
							500
		0.045		4 0 0		400									0.046
		0.043		± 3 4			0.6		0.9	1.1			0.045		285
		0.30	0.33	0.36		0.39			0.42	0.45		0.30	0.32	0.34	0.36	0.38	0.40

238

U dates in the range 289-339 Ma, defining a Discordia with an upper intercept at 344 ± 19 Ma. Besides 4 analyses with high common Pb (4-10%) and one discordant spot (a80), those analyses define a Concordia date of 335.2 ± 1.2 Ma. On the other hand, 10 analyses of monazites from the same sample, showing either patchy or concentring zoning in BSE images (Fig.

SX

), yield a Concordia date of 302.8 ± 1.3 Ma.

  . A large majority of zircon analyses from this sample are from xenocrysts and zircon cores (n = 25 out of 38). Those yielded several dates clusters: Devonian (360-380 Ma; n = 2), Ordovician (~480 Ma; n = 2), early Cambrian to late Neoproterozoic (530-580 Ma, most being concordant at 550-560 Ma; n = 13) and early Neoproterozoic to Neoarchean (840-2560 Ma; n = 6), including concordant spots at ~840 Ma (a121), ~955 Ma (a116), ~1850 Ma (a118) and ~2560 Ma (a117). Regarding zircon rims and grains without cores, 13 analyses have 206 Pb/ 238 U dates between 158 and 313 Ma, defining a Discordia with an upper intercept of 314 ± 10 Ma. An identical Concordia date of 311.0 ± 1.1 Ma was calculated from the six analyses with the highest and identical 206 Pb/ 238 U ratios, excluding two older outliers from the same grain (a108 and a109) having 206 Pb/ 238 U dates of 321-324 Ma and perhaps representing a xenocryst. The Concordia date from zircon is slightly older, yet overlaps with a Concordia date of 309.3 ± 1.2 Ma obtained from six monazite analyses in this sample, showing weak to sector zoning (Fig.SX).

  but with limited confidence, owing to large uncertainties (304.1 ± 6.3 Ma). Apart from one spot from a single zircon core (a248) recording a highly discordant Neoarchean date ( 207 Pb/ 206 Pb date of 2622 ± 18 Ma) and two outliers with 206 Pb/ 238 U dates of ~325 Ma, the main population of analyses (n = 16) is characterized by moderate to high proportions of common Pb (1-10%, and up to 15-18%) and shows Triassic to late Carboniferous 206 Pb/ 238 U dates (230-303 Ma). These analyses define a Discordia with an upper intercept of 303 ± 18 Ma. Among those, a Concordia date of 298.9 ± 1.8 Ma was calculated from the ten analyses with the highest, equivalent 206 Pb/ 238 U ratios.

  Two zircon analyses from this sample are from small, rounded cores and yielded nearly concordant, Cambrian (a513; 207 Pb/ 206 Pb date = 532 ± 21 Ma) to Neoproterozoic (a504, 207 Pb/ 206 Pb date = 580 ± 6 Ma) dates. Apart from those, the main population of core-free zircons show scattered 206 Pb/ 238 U dates between 260 and 340 Ma, defining a Discordia with an upper intercept of 337 ± 2 Ma (n = 29). Nonetheless, most analyses are sub-concordant and clustered around 330-340 Ma, and among those, the 16 equivalent analyses with the highest 206 Pb/ 238 U provide a Concordia date of 337.4 ± 1.0 Ma.

Sample LR-32 (e) Sample PRC-53

  U-Pb Concordia diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for zircon analyses from samples of vaugnerites from the eastern FMC. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty. zircon analyses from this sample are identical within error and yield a Concordia date of 299.1 ± 1.3 Ma (n = 17).  Sample LR-32 (Fig. S5) LR-32 belongs to the same suite as LR-31. Apart from three zircon analyses with discordant, Jurassic to Permian 206 Pb/ 238 U dates (164-291 Ma), all analyses from this sample show very homogeneous and identical 206 Pb/ 238 U ratios corresponding to a Concordia date of 301.5 ± 1.4 Ma (n = 17). Rouge quarry, roughly in the center of the Velay dome and ~10 km to the North of the site where LR-31 and LR-32 were collected. Together with PRC-54, these are quartz-syenites with distinctive richness in SiO 2 (60-62 wt.%) combined with very high K 2 O contents (>6 wt.%) that make them unique among other vaugnerite occurrences throughout the Massif Central (unpublished data from S. Couzinié). They crop out as decametric-scale enclaves in the Velay granite (represented by sample PRC-56, see section 4.2) suggesting they represent dismembered fragments of earlier intrusions. Zircon analyses from sample PRC-53 are characterized by Permian to Carboniferous 206 Pb/ 238 U dates ranging from 249 to 323 Ma. Those analyses define a Discordia trend with an upper intercepts of 330 ± 12 Ma (n = 22). Among them, the analyses the highest, equivalent 206 Pb/ 238 U ratios correspond to a Concordia date of 318.9 ± 1.8 Ma (n = 11). PRC-54 was sampled from a quartz-syenite enclave within the Velay granite at the Pont-Rouge quarry. Zircon analyses from this sample are also characterized by Permian to Carboniferous 206 Pb/ 238 U dates comprised between 265 and 321 Ma (n = 17) and a Discordia trend with an upper intercepts at 326 ± 9 Ma. Nonetheless, most analyses show within-error equivalent 206 Pb/ 238 U ratios that correspond to a Concordia date of 320.5 ± 1.8 Ma (n = 11).

	0.053	(a) Sample 533-1 Concordia Age = 307.8 ± 1.6 Ma	data-point error ellipses are 2σ 330	0.054	(b) Sample 533-2 Concordia Age = 307.3 ± 1.3 Ma	data-point error ellipses are 2σ
		MSWDC+E = 1.05 ; Prob.C+E = 0.40			MSWDC+E = 0.73 ; Prob.C+E = 0.87	330
	0.051	n = 12 Upper intercept = 321 ± 33 Ma MSWD = 0.62	320	0.052	n = 18 Upper intercept = 310 ± 6 Ma MSWD = 0.80	320
		n = 16		0.050	n = 27
	4 0 6 7 0 0.22 0.32 240 -4 5 8 7 8 ± 0.32 0.19 1 5 ± 0.30 270 280 290 290 Concordia Age = 301.5 ± 1.4 Ma 0.34 0.36 0.25 0.28 0.34 0.36 207 Pb/ 235 U 260 220 0.30 0.042 0.044 0.046 0.048 0.022 0.027 0.032 0.037 0.042 0.047 0.052 0.16 0.038 0.042 0.046 0.050 0.054 0.058 0.28 207 Pb/ 235 U MSWDC+E = 0.71 ; Prob.C+E = 0.88 n = 17 Upper intercept = 310 ± 9 Ma MSWD = 0.40 n = 20 (d) 206 -4 7 ± 1 6 0 0.043 0.045 0.047 0.049 0.30 0.32 0.34 0.36 0.38 0.40 0.041 0.043 0.045 0.047 0.049 0.051 0.053 0.29 0.32 0.35 0.38 0.036 0.039 0.042 0.045 0.048 0.051 0.054 0.057 0.26 0.29 0.32 0.35 0.38 0.41 290 330 data-point error ellipses are 2σ 270 310 data-point error ellipses are 2σ 290 206 Pb/ 238 U 207 Pb/ 235 U 206 Pb/ 238 U 280 320 280 206 Pb/ 238 U 207 Pb/ 235 U (c) Sample LR-31 Concordia Age = 299.1 ± 1.3 Ma MSWDC+E = 0.75 ; Prob.C+E = 0.85 n = 17 290 290 206 Pb/ 238 U Pb/ 238 U 207 Pb/ 235 U Concordia Age = 318.9 ± 1.8 Ma MSWDC+E = 0.48 ; Prob.C+E = 0.98 n = 11 Upper intercept = 330 ± 12 Ma MSWD = 1.50 n = 22 250 270 310 250 270 310 207 Pb/ 235 U 206 Pb/ 238 U Concordia Age = 320.5 ± 1.8 Ma MSWDC+E = 0.42 ; Prob.C+E = 0.99 n = 11 Upper intercept = 326 ± 9 Ma MSWD = 0.58 n = 17 (f) Sample PRC-54 290 310 290 310 PRC-53 was sampled at the Pont- Sample PRC-54 (Fig. S5) Figure S5:  Sample PRC-53 (Fig. S5) Like PRC-53,	0.38 0.34 0.40 350 data-point error ellipses are 2σ 0.40 0.31 0.37 0.38 0.42 330 280 data-point error ellipses are 2σ 320

  206 Pb/ 238 U dates at 381 ± 10 Ma and 397 ± 8

	0.053						0.054
							0.052
	0.051
							0.050
	0.049						0.048
							0.046
	0.047
							0.044
	0.045						0.042
	0.31	0.33	0.35		0.37	0.39	0.30	0.33			0.36		0.39
	0.056						0.058
	0.054						0.054
	0.052						0.050
	0.050						0.046						a28
											0.075
	0.048						0.042		1800		0.065
												a32
									0.055		a22
	0.046						0.038
									0.045			a38
										0.3	0.4	0.5	0.6
	0.044						0.034
	0.31	0.33	0.35	0.37	0.39	0.41	0.24	0.28	0.32	0.36	0.40	0.44
	0.059				data-point error ellipses are 2σ
	0.056				350
	0.053
			320
	0.050
	0.047
	0.044
	0.32	0.34	0.36	0.38	0.40	0.42

  206 Pb/ 238 U date of 488 ± 8 Ma. Analysis a38 is largely discordant and is characterized by an enormous amount of common Pb (~33%) such that its (poorly constrained) 207 Pb/ 206 Pb date of 1172 ± 216 Ma is probably meaningless. The analyses from zircons devoid of cores show 206 Pb/ 238 U dates scattered between 234 and 338 Ma, defining a Discordia with an upper intercept of 347 ± 18 Ma (n = 18). The analyses with the highest, within-error identical 206 Pb/ 238 U ratios yield a Concordia date of 335.7 ± 2.1 Ma (n = 9).

  Out of nine zircon analyses, six have 206 Pb/ 238 U ratios that are identical within error and define a Concordia date of 306.6 ± 2.4 Ma. One spot (a12) displays a slightly older 206 Pb/ 238 U date of 322 ± 6 Ma, and may correspond to a xenocryst (darker CL luminescence). Two other outliers show significantly younger (Permian) 206 Pb/ 238 U dates.

  Barbarin, B., 1983. Les granites carbonifères du Forez septentrional (Massif Central Français). Typologie et relations entre les différents massifs. -Thèse 3e cycle, Université Clermont-Ferrand, 199 p.[START_REF] Barbarin | Notice explicative, Carte géol[END_REF]. Notice explicative, Carte géologique de la France (1/50 000e), feuille Firminy (nr. 744). Orléans, Bureau de Recherches Géologiques et Minières, 129 pp. Couturié, J.-P., 1977, Le massif granitique de la Margeride (M.C.F.). Etude pétrographique, géochimique et structurale. Exemple de différenciation par gravité dans les roches granitiques. Evolution régionale de la croûte au cours de l'orogène hercynien. [Thèse de 3ème cycle: Clermont-Ferrand, 335 p. Couzinié, S., Moyen, J. F., Villaros, A., Paquette, J. L., Scarrow, J. H., and Marignac, C., 2014. Temporal relationships between Mg-K mafic magmatism and catastrophic melting of the Variscan crust in the southern part of Velay Complex (Massif Central, France): Journal of GEOsciences, p. 69-86. U-Pb Concordia diagrams ( 206 Pb/ 238 U vs. 207 Pb/ 235 U) for zircon analyses from samples of vaugnerites from the eastern FMC. Green ellipses are the oldest, equivalent concordant analyses from zircon rims or crystals devoid of any core (excluding outliers), used for the calculation of the Concordia Age. The dashed ellipses represent analyses with >5% of common 204 Pb (though used for age calculation). The dashed red lines are regressions through all the data from zircon rims or crystals devoid of any core; the arrow and numbers in italics point to the lower intercept of the Discordia. All ages are quoted to 2σ level of uncertainty.

		0.055	(a) Sample SGC-12-13		data-point error ellipses are 2σ	0.054	(b) Sample SGC-12-26	data-point error ellipses are 2σ
		0.052	n = 6 Concordia Age = 306.6 ± 2.4 Ma MSWDC+E = 0.59 ; Prob.C+E = 0.84		330		0.052	n = 20 Concordia Age = 306.1 ± 1.3 Ma MSWDC+E = 1.04 ; Prob.C+E = 0.39	330
			Upper intercept = 319 ± 27 Ma MSWD = 0.37						320
		0.049	n = 9									0.050
	U Pb/ 238 206	0.043 0.046				270	290				206 Pb/ 238 U	0.046 0.048	290 290
													280 280
		0.040	250								0.044
				-5 3	±	6 8 0							270
		0.037										0.042
		0.26	0.28		0.30	0.32	0.34	0.36	0.38	0.40	0.30	0.33	0.36	0.39
							207 Pb/ 235 U					207 Pb/ 235 U
		0.053	(d) Sample SGC-12-39 Concordia Age = 306.6 ± 1.6 Ma	data-point error ellipses are 2σ 330	0.053	(d) Sample SGC-12-42 Concordia Age = 305.9 ± 1.7 Ma	data-point error ellipses are 2σ 330
			MSWDC+E = 0.66 ; Prob.C+E = 0.88						MSWDC+E = 0.56 ; Prob.C+E = 0.95
			n = 12									n = 11
		0.051							310			0.051	320
	206 Pb/ 238 U	0.047 0.049									206 Pb/ 238 U	0.047 0.049
						290							290 290
		0.045										0.045
				280									280
		0.043										0.043
		0.30			0.33			0.36		0.39	0.30	0.32	0.34	0.36	0.38	0.40
							207 Pb/ 235 U					207 Pb/ 235 U
		Figure S7:

Laurent et al., 2017. Supplementary Table S1:

  Results of LA-SF-ICPMS U-Pb analyses of standard zircons GJ-1, Plesoviče, OG-1 and BB.

	Results of LA-SF-ICPMS U-Pb analyses of standard zircons GJ-1, Plesoviče, OG-1 and BB.
		207 Pb a 207 Pb a	U U	b b	Pb b Pb b	Th b Th b	206 Pbc 206 Pbc	c c	206 Pb d 206 Pb d	±2σ ±2σ	207 Pb e 207 Pb e	±2σ ±2σ	207 Pb d 207 Pb d	±2σ ±2σ	ρ ρ	f f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g 206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps) (ppm) (ppm) (cps) (ppm) (ppm)	U U	(%) (%)		238 U 238 U	(%) (%)	235 U 235 U	(%) (%)	206 Pb 206 Pb	(%) (%)			238 U (Ma) 235 U (Ma) 206 Pb (Ma) (%) 238 U (Ma) 235 U (Ma) 206 Pb (Ma) (%)
	GJ-1 Average (n=11)	579	30.0 0.094			0.0539		0.3953		0.0531				408	408	407
	Session #1 (April 9 th , 2014) 2 S.D. ext. (abs.) 97	4.9 0.006			0.0011		0.0080		0.0001				324	325	326
	GJ1-01 2 S.D. ext. (%) 8230			24.2 0.02	b.d.		0.0973 2.0	1.6	0.8131 2.0	3.2 0.06059 2.7 0.50 599 0.3 Conc. Age = 338.6 ± 1.7 Ma 9 604 15	625	59	99
	GJ1-02	8997			24.7 0.02	b.d.		0.0972	1.6	0.8267	3.2 0.06168 2.8 0.49 598 (MSWD C+E = 0.66 ; P C+E = 0.87) 9 612 15 663	59	98
	GJ1-03 Session #2 (August 13th, 2014) 9044 26.0 0.02	b.d.		0.0989	1.5	0.8227	3.0 0.06033 2.6 0.50 608	9	610	14	615	56 100
	GJ1-04 Plešo01	9650 22823	660	27.5 0.02 33.8 0.13	b.d. 0.03		0.0987 0.0542	1.5 0.8	0.8394 0.3984	3.1 0.06167 2.7 0.47 607 1.2 0.05328 0.8 0.71 340	8 3	619 341	14 3	663 341	58 19	98
	GJ1-05 Plešo02	9245 22637	671	26.4 0.02 34.1 0.12	b.d. 0.04		0.0983 0.0540	1.4 1.0	0.8241 0.3957	3.1 0.06080 2.7 0.46 604 1.2 0.05316 0.7 0.79 339	8 3	610 338	14 3	632 336	58 17	99
	GJ1-06 Plešo03	8693 22698	680	24.7 0.02 34.7 0.13	b.d. 0.12		0.0982 0.0541	1.6 0.9	0.8322 0.3967	3.1 0.06145 2.7 0.50 604 1.2 0.05323 0.7 0.78 339	9 3	615 339	15 3	655 338	58 17	98
	GJ1-07 Plešo04	8352 22042	682	24.9 0.02 35.0 0.12	b.d. 0.03		0.0995 0.0544	1.5 0.9	0.8368 0.3993	3.1 0.06100 2.7 0.50 611 1.2 0.05321 0.7 0.82 342	9 3	617 341	14 3	639 338	57 15	99
	GJ1-08 Plešo05	8452 22378	710	26.2 0.02 36.1 0.12	b.d. 0.06		0.0984 0.0539	1.6 1.0	0.8196 0.3956	3.1 0.06039 2.6 0.51 605 1.2 0.05321 0.7 0.81 339	9 3	608 338	14 3	617 338	57 100 16
	GJ1-09 Plešo06	8714 23064	706	26.3 0.02 36.3 0.13	b.d. 0.01		0.0977 0.0546	1.6 0.9	0.8152 0.4012	3.2 0.06052 2.8 0.49 601 1.2 0.05326 0.8 0.74 343	9 3	605 343	15 3	622 340	60 18	99
	GJ1-10 Plešo07	8664 23103	726	26.5 0.02 37.2 0.12	b.d. 0.08		0.0984 0.0543	1.5 1.0	0.8327 0.3993	3.2 0.06136 2.8 0.48 605 1.3 0.05334 0.9 0.74 341	9 3	615 341	15 4	652 343	60 19	98 99
	GJ1-11 Plešo09	8128 22936	709	25.7 0.02 36.3 0.13	b.d. 0.02		0.0988 0.0543	1.5 0.8	0.8414 0.3981	3.2 0.06175 2.8 0.48 607 1.2 0.05322 0.8 0.69 341	9 3	620 340	15 3	666 338	60 19	98
	GJ1-12 Plešo10	7735 22603	736	23.8 0.02 37.4 0.12	b.d. 0.05		0.0985 0.0540	1.5 0.8	0.8303 0.3963	3.0 0.06116 2.7 0.49 605 1.1 0.05320 0.8 0.73 339	9 3	614 339	14 3	645 337	57 17	99
	GJ1-13 Plešo11	7855 23206	693	24.9 0.02 35.2 0.13	b.d. 0.03		0.0972 0.0539	1.5 0.9	0.8052 0.3964	3.0 0.06007 2.6 0.49 598 1.1 0.05329 0.6 0.85 339	9 3	600 339	14 3	606 341	57 100 13 99
	GJ1-14 Plešo12	8197 23312	686	26.3 0.02 35.1 0.13	b.d. 0.05		0.0977 0.0544	1.4 0.8	0.8155 0.3998	3.1 0.06051 2.7 0.47 601 1.2 0.05333 0.8 0.73 341	8 3	606 341	14 3	622 343	58 18	99
	GJ1-15 Plešo13	7727 22770	683	26.1 0.02 34.7 0.12	b.d. 0.03		0.0978 0.0540	1.5 0.9	0.8149 0.3962	3.1 0.06043 2.7 0.50 602 1.2 0.05323 0.7 0.78 339	9 3	605 339	14 3	619 339	58 16	99
	GJ1-16 Plešo14	7259 22501	676	24.3 0.02 34.6 0.12	b.d. 0.05		0.0985 0.0544	1.5 0.8	0.8354 0.3988	3.2 0.06152 2.8 0.46 605 1.1 0.05322 0.8 0.67 341	8 3	617 341	15 3	658 338	61 19	98
	GJ1-17 Plešo15	6822 22758	675	23.8 0.02 34.3 0.13	b.d. 0.04		0.0974 0.0539	1.5 1.0	0.8059 0.3955	3.2 0.06000 2.9 0.46 599 1.3 0.05322 0.8 0.76 338	8 3	600 338	15 4	604 338	62 100 19
	GJ1-18 Plešo16	7564 22291	674	25.6 0.02 34.5 0.12	b.d. 0.06		0.0979 0.0543	1.5 1.0	0.8382 0.3990	3.1 0.06207 2.7 0.49 602 1.3 0.05330 0.8 0.80 341	9 3	618 341	15 4	676 341	58 17	97
	GJ1-19 Plešo17	8020 29486	839	26.9 0.02 43.7 0.19	b.d. 0.10		0.0988 0.0543	1.4 0.9	0.8329 0.3992	3.1 0.06114 2.8 0.46 607 1.2 0.05328 0.8 0.73 341	8 3	615 341	15 4	644 341	60 19	99
	GJ1-20 Plešo18	8022 26278	774	26.7 0.02 40.1 0.18	b.d. 0.04		0.0977 0.0543	1.4 0.9	0.8327 0.3988	3.0 0.06180 2.7 0.47 601 1.2 0.05328 0.7 0.77 341	8 3	615 341	14 3	667 341	57 17	98
	GJ1-21 Average (n=17) 7762	705	25.8 0.02 36.1 0.132	b.d.		0.0983 0.0542	1.4	0.8290 0.3979	3.0 0.06117 2.7 0.47 604 0.0533 339	8	613 339	14	645 339	58	99
	GJ1-22 2 S.D. ext. (abs.) 7196	89	24.9 0.02 5.0 0.040	b.d.		0.0990 0.0004	1.3	0.8377 0.0035	2.9 0.06138 2.6 0.46 608 0.0001 8	8	618 8	14	653 7	55	98
	Average (n=22) 2 S.D. ext. (%)			25.6 0.022			0.0982 0.8		0.8264 0.9		0.0610 0.2				604 Conc. Age = 340.2 ± 0.8 Ma 612	640
	2 S.D. ext. (abs.)	22	2.1 0.001			0.0013		0.0219		0.0012				7 (MSWD C+E = 0.39 ; P C+E = 0.99) 12 43
	2 S.D. ext. (%)							1.3		2.6		2.0				Conc. Age = 604.9 ± 2.2 Ma
	OG-1																(MSWD C+E = 1.3 ; P C+E = 0.11)
	Session #2 (August th , 2014) Session #1 (April 9 th , 2014)
	GJ1-01 OG1-01	20230 221594 164 162.6 0.66 25.8 0.02	b.d. 0.70		0.0979 0.7127	0.8 2.1	0.812 29.130	1.8 0.06016 1.6 0.45 602 2.3 0.29640 1.0 0.89 3469 56 3458 23 3452 16 5 604 8 609 34 100
	GJ1-02 OG1-02	19635 144020 150 147.1 0.93 25.5 0.02	b.d. 0.70		0.0983 0.7115	0.8 1.8	0.8160 29.270	1.7 0.06018 1.5 0.46 605 1.8 0.29830 0.4 0.97 3464 48 3462 18 3462 5 606 8 610	33 100 7
	GJ1-03 OG1-03	19229 128196 143 132.4 0.65 25.1 0.02	b.d. 1.08		0.0984 0.7105	0.7 2.2	0.8148 28.910	1.8 0.06006 1.6 0.40 605 2.3 0.29510 0.7 0.96 3460 59 3450 23 3445 10 4 605 8 606 36 100
	GJ1-04 OG1-04	19139 123805 134 119.6 0.48 25.8 0.02	b.d. b.d.		0.0984 0.7121	0.7 1.8	0.8143 29.250	1.6 0.06005 1.5 0.46 605 1.8 0.29790 0.5 0.97 3466 48 3462 18 3459 4 605 7 605	32 100 7
	GJ1-05 OG1-05	19237 194964 180 180.5 0.94 25.3 0.02	b.d. 0.87		0.0977 0.7109	0.8 2.0	0.8087 28.965	1.7 0.06002 1.5 0.48 601 2.0 0.29551 0.4 0.98 3462 53 3452 20 3447 5 602 8 604	33 100 7
	GJ1-06 OG1-07	18660 83721	93	25.7 0.02 85.3 0.72	b.d. 2.41		0.0983 0.7102	0.7 1.8	0.8153 29.150	1.6 0.06013 1.5 0.42 605 1.8 0.29760 0.5 0.96 3459 48 3458 18 3458 4 605 7 608	32 100 8
	GJ1-07 OG1-08	18249 72584	82	25.4 0.02 77.0 0.82	b.d. 0.08		0.0986 0.7075	0.8 1.8	0.8174 29.120	1.6 0.06010 1.4 0.52 606 1.8 0.29840 0.5 0.96 3449 47 3457 18 3462 5 607 7 607	30 100 7
	GJ1-08 OG1-09	18556 135953 155 140.1 0.59 25.2 0.02	b.d. 0.25		0.0978 0.7127	0.9 1.8	0.8099 29.290	1.7 0.06008 1.5 0.50 601 1.8 0.29800 0.4 0.98 3469 48 3463 18 3460 5 602 8 606	33 100 6
	GJ1-09 OG1-10	18499 132368 129 129.5 0.92 25.5 0.02	b.d. 0.05		0.0981 0.7125	0.8 1.8	0.8119 29.210	1.7 0.06000 1.5 0.47 603 2.0 0.29730 0.8 0.91 3468 49 3460 20 3456 13 4 603 8 603 32 100
	GJ1-10 Average (n=9) 18006	25.3 0.02 137 130.5 0.746	b.d.		0.0980 0.7112	0.8	0.8113 29.144	1.8 0.06006 1.6 0.43 603 0.2972 3463	4	603 3458	8	606 3456	34 100
	GJ1-11 2 S	18939			25.6 0.02	b.d.		0.0985	0.7	0.8157	1.7 0.06005 1.5 0.43 606	4	606	8	605	33 100
	GJ1-12	18781			25.1 0.02	b.d.		0.0982	0.8	0.8125	1.7 0.05999 1.5 0.49 604	5	604	8	603	33 100
	GJ1-13	18858			25.6 0.02	b.d.		0.0983	0.9	0.8151	1.7 0.06012 1.5 0.50 605	5	605	8	608	32 100
	GJ1-14	18207			25.3 0.02	b.d.		0.0983	0.8	0.8135	1.7 0.06005 1.5 0.45 604	4	604	8	605	33 100
	GJ1-15	19458			25.7 0.02	b.d.		0.0980	0.8	0.8107	1.6 0.06003 1.4 0.48 602	5	603	8	605	31 100
	GJ1-16	18889			25.5 0.02	b.d.		0.0982	0.7	0.8132	1.6 0.06006 1.5 0.44 604	4	604	8	606	32 100
	GJ1-17	18570			25.7 0.02	b.d.		0.0983	0.8	0.8144	1.7 0.06008 1.5 0.47 605	5	605	8	606	33 100
	GJ1-18	19087			25.4 0.02	b.d.		0.0983	0.9	0.8111	1.7 0.05986 1.4 0.51 604	5	603	8	598	31 100
	GJ1-19	18609			25.6 0.02	b.d.		0.0981	0.8	0.8115	1.9 0.06000 1.7 0.41 603	4	603	8	604	37 100
	GJ1-20	18754			25.1 0.02	b.d.		0.0980	0.8	0.8116	1.7 0.06009 1.5 0.47 602	5	603	8	607	33 100
	Average (n=20)			25.4 0.024			0.0982		0.8131		0.0601				604	604	606
	2 S.D. ext. (abs.)	5	0.5 0.001			0.0005		0.0046		0.0001				3	3	5
	2 S.D. ext. (%)							0.5		0.6		0.2				Conc. Age = 603.9 ± 2.2 Ma
																	(MSWD C+E = 0.2 ; P C+E = 0.99)
	Plesoviče
	Session #1 (April 9 th , 2014)
	Pleso-01	10145			32.4 0.09	0.08		0.0538	1.8	0.3948	3.6 0.05318 3.1 0.51 338	6	338	10	336	71 100
	Pleso-02	10120			33.0 0.09	0.31		0.0542	1.6	0.3982	2.5 0.05324 2.0 0.62 341	5	340	7	339	45 100
	Pleso-03	8649			29.4 0.09	0.09		0.0551	1.7	0.4033	3.0 0.05312 2.5 0.55 346	6	344	9	334	58 103
	Pleso-04	8488			29.2 0.09	0.20		0.0541	1.7	0.3962	3.0 0.05316 2.5 0.55 339	6	339	9	335	57 101
	Pleso-05	7991			26.8 0.09	0.26		0.0532	1.9	0.3893	3.9 0.05308 3.4 0.49 334	6	334	11	332	77 101
	Pleso-06	8023			30.2 0.09	0.30		0.0543	1.8	0.3984	4.1 0.05318 3.7 0.43 341	6	341	12	336	85 101
	Pleso-07	7443			26.6 0.09	0.15		0.0535	1.5	0.3920	3.5 0.05316 3.2 0.42 336	5	336	10	336	73 100
	Pleso-08	7827			28.5 0.09	0.36		0.0535	1.6	0.3929	4.1 0.05326 3.8 0.39 336	5	336	12	340	86	99
	Pleso-09	7838			28.4 0.10	0.23		0.0535	1.5	0.3911	3.2 0.05302 2.8 0.48 336	5	335	9	330	64 102
	Pleso-10	8936			33.2 0.10	0.22		0.0543	1.7	0.3975	3.2 0.05310 2.7 0.52 341	6	340	9	333	62 102
	Pleso-11	9987			32.5 0.09	1.57		0.0538	1.7	0.3942	5.2 0.05312 4.9 0.33 338	6	337	15	334 110 101

.D. ext. (abs.) 64 66.8 0.332 0.0033 0.2650 0.0024 13 9 13 2 S.D. ext. (%) 0.5 0.9 0.8 Conc. Age = 3458 ± 7 Ma (MSWD C+E = 1.3 ; P C+E = 0.17)

	Laurent et al., 2017. Supplementary Table S1 (continued):
	Results of LA-SF-ICPMS U-Pb analyses of standard zircons GJ-1, Plesoviče, OG-1 and BB.
			207 Pb a		U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
			(cps) (ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)	238 U (Ma) 235 U (Ma) 206 Pb (Ma) (%)
	Degeo-10 14377		552	49.6 0.16	0.01		0.0928	1.5	0.7570	2.1 0.05916 1.4 0.72 572	9	572	8	573	31 100
	Degeo-11 14544		573	51.3 0.16	b.d.		0.0927	1.6	0.7555	2.5 0.05912 2.0 0.62 571	11	571	9	571	43 100
	Average (n=11)		579	51.7 0.159		0.0923		0.7522		0.0591		569	569	570
	2 S.D. ext. (abs.)		36	3.5 0.007		0.0013		0.0125		0.0002		7	8	7
	2 S.D. ext. (%)								1.4		1.7		0.3		Conc. Age = 569.3 ± 2.5 Ma
																	(MSWD C+E = 0.39 ; P C+E = 0.99)
	206 Pb/	238 U error is the quadratic addition of the within run precision (2σ) and the external reproducibility (2σ ext.) of the reference zircon GJ-1
	207 Pb/	206 Pb uncertainty is calculated using	207 Pb signal dependent error propagation following Gerdes & Zeh (2009)
	207 Pb/ 235 U error is the quadratic addition of the 207 Pb/ 206 Pb and 206 Pb/ 238 U uncertainties
	(a) Within-run background-corrected mean	207 Pb signal in cps (counts per second).
	Session #2 (August 13	th , 2014)
	OG1-01	294755		109 110.1 1.20	1.65		0.7105	1.0	29.267	1.2 0.29876 0.7 0.83 3463 12 3460 27 3464 10
	OG1-02	526578		195 197.2 1.39	0.59		0.7105	0.7	29.212	0.9 0.29819 0.5 0.85 3461	9	3460 20 3461	7
	OG1-03	288100		108 117.4 1.62	1.33		0.7114	1.4	29.347	1.5 0.29917 0.6 0.91 3465 15 3464 37 3466 10
	OG1-04	89588.9	41	36.9 0.59	0.14		0.7174	1.3	29.502	1.4 0.29827 0.6 0.91 3470 14 3486 35 3461	9
	OG1-06	151415		65	62.3 1.11	b.d.		0.7085	1.2	29.184	1.3 0.29875 0.4 0.95 3460 13 3453 33 3464	6
	OG1-07	185387		65	67.3 1.26	1.58		0.7120	1.4	29.130	1.5 0.29674 0.7 0.89 3458 15 3466 36 3453 11
	OG1-08	111215		37	37.4 1.34	1.30		0.7079	1.3	29.217	1.5 0.29933 0.6 0.91 3461 14 3451 36 3467	9
	OG1-09	129496		52	52.1 1.07	1.56		0.7136	1.9	29.433	2.0 0.29915 0.8 0.92 3468 20 3472 51 3466 13
	OG1-10	112791		47	41.9 0.63	0.35		0.7087	1.5	29.210	1.6 0.29894 0.5 0.95 3461 16 3453 40 3465	8
	OG1-11	209092		107 102.2 0.96	1.31		0.7119	1.5	29.343	1.6 0.29893 0.6 0.94 3465 16 3466 41 3465	9
	Average (n=10)		82	82.5 1.116		0.7112		29.285		0.2986		3463	3463	3463
	2 S.D. ext. (abs.)		97	100.7 0.646		0.0056		0.2369		0.0015		8	21	8
	2 S.D. ext. (%)								0.8		0.8		0.5		Conc. Age = 3463 ± 6 Ma
																	(MSWD C+E = 0.44 ; P C+E = 0.98)
	BB
	Session #1 (April 9	th , 2014)
	Degeo-01 18079		601	53.3 0.16	b.d.		0.0917	1.7	0.7447	2.1 0.05889 1.3 0.80 565	9	566	9	563	27
	Degeo-02 18031		609	54.6 0.16	b.d.		0.0928	1.6	0.7568	2.4 0.05913 1.8 0.67 572	10	572	9	572	38
	Degeo-03 17521		596	53.9 0.16	0.06		0.0937	1.7	0.7647	2.2 0.05920 1.5 0.75 577	10	577	9	575	32
	Degeo-04 16787		596	53.0 0.16	b.d.		0.0922	1.5	0.7512	1.7 0.05911 0.8 0.89 569	7	568	8	571	17	99
	Degeo-05 15704		570	50.6 0.16	0.05		0.0921	1.6	0.7494	2.1 0.05903 1.5 0.73 568	9	568	9	568	32
	Degeo-06 15051		577	51.5 0.15	b.d.		0.0926	1.6	0.7541	1.9 0.05909 0.9 0.87 571	8	571	9	570	20
	Degeo-07 14959		570	50.4 0.16	0.02		0.0916	1.5	0.7448	2.3 0.05897 1.7 0.67 565	10	565	8	566	37
	Degeo-08 14648		566	50.0 0.17	b.d.		0.0915	1.5	0.7448	1.8 0.05903 1.0 0.85 565	8	564	8	568	21	99
	Degeo-09 14207		563	50.1 0.16	b.d.		0.0922	1.5	0.7507	1.7 0.05908 0.9 0.86 569	7	568	8	570	19

Table S2 :

 S2 Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	a Laurent et al., 2016. Supplementary 207 Pb U b Pb b Th b 206 Pbc Laurent	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)			238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	Granitoids
	CHZ
	Session #1 (April 9 th , 2014)
	a78	21589 1375 289.4 0.91	0.18		0.0528	1.8	0.3856	2.1 0.05293 1.1 0.85 332	6	6	326	25	102
	a79	35429 2350 569.9 1.58	b.d.		0.0523	1.7	0.3827	1.9 0.05305 0.8 0.90 329	5	5	331	18	99
	a80	67049 3232 709.8 1.39	1.30		0.0532	1.4	0.3889	2.8 0.05297 2.4 0.49 334	4	8	327	55	102
	a82	11302	708	161.7 1.48	0.43		0.0532	1.5	0.3945	2.9 0.05381 2.5 0.51 334	5	8	363	56	92
	a83	88527 4154 880.0 0.74	3.64		0.0532	1.6	0.3840	5.0 0.05240 4.7 0.32 334	5	14	303	106	110
	a84	39364 2805 475.8 0.44	0.73		0.0479	1.5	0.3459	2.2 0.05239 1.6 0.67 302	4	6	303	37	100
	a85	32384	911	200.8 0.58	8.34		0.0528	2.0	0.3845	6.5 0.05285 6.2 0.31 331	7	19	322	142	103
	a86	23058 1543 252.4 0.28	0.92		0.0482	1.6	0.3483	2.4 0.05245 1.8 0.65 303	5	6	305	41	99
	a87	40005	556	208.2 0.21	4.81		0.1014	2.9	0.8484	5.2 0.06066 4.4 0.55 623	17	25	627	94	99
	a88	15521 1108 267.5 1.86	b.d.		0.0492	1.6	0.3615	2.2 0.05324 1.5 0.73 310	5	6	339	34	91
	a89	8910	689	27.0	0.93	0.04		0.0500	1.4	0.3661	2.4 0.05315 1.9 0.61 314	4	6	335	42	94
	a91	247927 8905 421.2 0.43	3.95		0.0652	1.6	0.4938	4.4 0.05495 4.1 0.35 407	6	15	410	91	99
	a92	10515	745	62.9	1.07	0.53		0.0486	1.7	0.3601	3.2 0.05371 2.7 0.53 306	5	9	359	61	85
	a93	26595 1853 167.2 1.43	0.30		0.0487	1.6	0.3573	1.9 0.05321 1.0 0.85 307	5	5	338	23	91
	a94	38005 1569	59.6	0.31	3.03		0.0523	1.6	0.3838	4.0 0.05325 3.7 0.39 328	5	11	339	83	97
	a95	20519	555	160.7 0.11	2.09		0.0868	1.6	0.6992	3.0 0.05844 2.6 0.53 536	8	13	546	56	98
	(e) a96 207 Pb/ 235 U = 32949 2216 403.4 0.56 207 Pb/ 206 Pb/( 238 U/ 206 Pb*1/137.88) 0.27		0.0502	1.8	0.3664	2.1 0.05298 1.2 0.83 315	5	6	328	27	96
	(f) ρ (rho) is the correlation coefficient between errors of a97 67341 3270 711.4 1.45 1.39 0.0462 206 Pb/ 238 U and 1.6 0.3368 207 Pb/ 235 U. 2.3 0.05291 1.7 0.70 291 a98 31208 1691 259.5 0.36 3.35 0.0478 2.0 0.3506 4.2 0.05325 3.7 0.47 301	5 6	6 11	325 339	38 83	90 89
	(g) Degree of concordance = ( 206 Pb/ 238 U age / a99 217754 1286 866.0 0.30 0.14 207 Pb/ 206 Pb age) × 100 0.1809 2.4	3.8324	2.4 0.15366 0.4 0.98 1072	23	1600	20	2387	7	45
	a100	75903 4345 644.2 0.15	2.33		0.0436	1.6	0.3197	3.6 0.05323 3.2 0.45 275	4	9	339	73	81
	a101	15899	741	178.6 0.29	0.06		0.0729	1.5	0.5615	1.8 0.05583 1.0 0.83 454	6	6	446	22	102
	HER
	Session #2 (August 13 th , 2014)
	a245	101734 102	58.9	0.75	b.d.		0.4947	0.8	11.999	1.0 0.17593 0.6 0.79 2591	17	2604	9	2615	10	99
	a246	20973	620	50.2	2.84	0.64		0.0508	0.8	0.3626	2.6 0.05182 2.5 0.30 319	2	7	277	58	115
	a247	15138	472	28.5	1.59	0.61		0.0447	1.1	0.3211	3.2 0.05215 2.9 0.36 282	3	8	292	67	96
	a248	13916	445	26.6	1.23	b.d.		0.0491	0.9	0.3605	1.3 0.05320 0.9 0.71 309	3	3	337	20	92
	a249	83250 2323 113.6 0.06	0.72		0.0520	0.8	0.3796	1.4 0.05295 1.1 0.58 327	3	4	327	26	100
	a250	5720	190	9.4	0.42	b.d.		0.0491	0.8	0.3574	1.5 0.05283 1.3 0.55 309	3	4	322	29	96
	a251	17363	609	29.2	0.55	0.51		0.0451	1.4	0.3368	4.7 0.05411 4.5 0.30 285	4	12	376	102	76
	a253	24601	539	25.9	0.23	2.78		0.0467	0.8	0.3392	3.6 0.05271 3.5 0.22 294	2	9	316	80	93
	a254	7860	244	12.5	0.63	0.00		0.0475	0.8	0.3953	1.8 0.06036 1.6 0.43 299	2	5	617	35	49
	a255	43239 1746	65.8	0.64	0.81		0.0324	1.4	0.2382	2.2 0.05329 1.8 0.61 206	3	4	341	40	60
	a256	36135	851	53.5	1.27	1.76		0.0501	0.7	0.3655	2.8 0.05288 2.7 0.24 315	2	8	324	61	97
	a257	30756	544	36.2	0.41	0.65		0.0636	0.9	0.4915	2.0 0.05609 1.7 0.47 397	4	7	456	38	87
	a258	102320 3233 155.8 0.02	0.40		0.0521	1.0	0.3777	1.3 0.05263 0.8 0.76 327	3	4	313	19	105
	a259	33620	608	35.5	0.71	3.87		0.0515	0.8	0.3776	4.3 0.05313 4.2 0.18 324	2	12	334	96	97
	a260	11192	365	18.9	0.66	0.50		0.0471	1.4	0.3849	2.5 0.05932 2.1 0.55 296	4	7	579	45	51
	a261	57890 1336	59.6	0.18	1.85		0.0443	1.0	0.3239	2.7 0.05301 2.5 0.37 280	3	7	329	57	85
	a262	207029 7292 260.0 0.05	1.22		0.0374	0.8	0.2729	1.9 0.05294 1.8 0.42 237	2	4	326	40	73
	a263	16903	519	25.6	0.22	0.14		0.0510	0.7	0.3731	1.2 0.05310 1.0 0.58 320	2	3	333	23	96
	a264	12380	304	17.2	1.26	3.00		0.0428	1.1	0.3335	6.2 0.05651 6.1 0.18 270	3	16	473	134	57
	a265	23899	286	28.6	0.36	1.78		0.0959	0.8	0.8105	3.4 0.06131 3.3 0.24 590	5	16	650	71	91
	a267	198243 6273 273.8 0.13	0.55		0.0457	0.9	0.3335	1.3 0.05290 1.0 0.65 288	2	3	324	23	89
	a268	122957 3735 179.6 0.39	0.24		0.0487	0.9	0.3544	1.1 0.05282 0.7 0.81 306	3	3	321	15	95
	a269	7107	214	13.6	1.47	b.d.		0.0494	0.8	0.4020	1.6 0.05903 1.4 0.51 311	3	5	568	31	55
	a270	22163	658	34.4	0.40	0.16		0.0518	1.0	0.3787	1.9 0.05306 1.7 0.52 325	3	5	331	38	98
	a271	69886 1405	78.2	0.80	3.76		0.0475	1.0	0.3453	4.4 0.05277 4.3 0.22 299	3	11	319	97	94
	a272	51563	397	57.2	0.28	0.74		0.1429	1.0	1.3354	1.9 0.06777 1.7 0.51 861	8	11	862	34	100
	a273	11701	314	16.3	0.93	1.65		0.0432	1.2	0.3122	5.8 0.05240 5.6 0.21 273	3	14	303	129	90
	a274	15460	436	23.4	0.44	0.63		0.0519	0.9	0.3791	1.9 0.05296 1.7 0.48 326	3	5	327	38	100
	OL-13-06
	Session #1 (April 9	th , 2014)
	a234	8476	682	30.4	0.39	0.29		0.0428	1.6	0.3114	2.1 0.05274 1.4 0.77 270	4	5	318	31	85
	a235	33179 2312 120.3 0.56	1.28		0.0469	1.7	0.3391	2.8 0.05240 2.3 0.59 296	5	7	303	52	98
	a236	8943	471	24.6	0.24	3.10		0.0500	1.6	0.3671	4.0 0.05324 3.7 0.39 315	5	11	339	84	93
	a237	116707 2866 104.1 0.22 37.11 0.0183	6.0	0.1314 13.9 0.05213 12.6 0.43 117	7	17	291	287	40
	a243	10925	704	32.0	0.41	2.55		0.0416	1.6	0.3025	3.6 0.05271 3.3 0.43 263	4	9	316	74	83
	a244	411736 9091 369.8 0.25 41.96 0.0202	4.7	0.1458 12.9 0.05225 12.0 0.37 129	6	17	297	273	44
	a245	30134 1475	63.5	0.28	4.11		0.0383	1.7	0.2793	5.1 0.05289 4.9 0.32 242	4	11	324	111	75
	a246	15226	381	23.9	0.89 12.88 0.0418	3.1	0.3017	9.4 0.05231 8.9 0.33 264	8	22	299	203	88

d) Corrected for background, within-run Pb/U fractionation (in case of 206 Pb/ 238 U) and common Pb, and subsequently normalized to GJ-1 (ID-TIMS value/measured value).

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)			238 U (Ma) 235 U (Ma) 206 Pb (Ma) (%)
	a247	19192 1277	67.0	0.38	1.38		0.0499	2.7	0.3626	3.7 0.05270 2.5 0.73 314	8	314	10	58	99
	a248	37600 2095	92.8	0.47	3.22		0.0377	1.8	0.2799	4.2 0.05380 3.8 0.42 239	4	251	9	85	66
	a249	41753 1531	66.9	0.08 13.34 0.0361	2.1	0.2610	7.8 0.05241 7.5 0.27 229	5	235	17	172	75
	a250	9648	805	38.8	0.38	0.58		0.0462	1.8	0.3399	2.8 0.05333 2.1 0.64 291	5	297	7	48	85
	a251	6595	541	25.9	0.23	0.14		0.0491	1.9	0.3567	2.2 0.05272 1.1 0.86 309	6	310	6	25	98
	a252	12622	694	35.2	0.50	3.53		0.0447	1.7	0.3275	4.6 0.05311 4.3 0.36 282	5	288	12	98	85
	a253	15146	540	29.0	0.37	8.03		0.0443	1.7	0.3162	6.6 0.05179 6.3 0.26 279	5	279	16	145	101
	a254	34792 1364	71.8	0.32	6.02		0.0445	1.8	0.3259	4.9 0.05314 4.5 0.37 281	5	286	12	103	84
	a255	4164	305	14.9	0.52	0.41		0.0446	1.8	0.3360	5.6 0.05459 5.3 0.31 282	5	294	14	119	71
	a256	15171	933	45.9	0.58	2.16		0.0435	1.8	0.3101	3.7 0.05176 3.2 0.49 274	5	274	9	74	100
	a257	8421	483	28.2	0.42	2.99		0.0496	1.7	0.3532	6.5 0.05170 6.2 0.26 312	5	307	17	142	115
	a258	6600	500	26.1	0.40	0.72		0.0448	1.4	0.3307	2.4 0.05349 1.9 0.60 283	4	290	6	43	81
	a259	13672	796	41.0	0.19	3.29		0.0499	2.0	0.3639	4.5 0.05285 4.1 0.44 314	6	315	12	92	98
	a260	13360	564	29.6	0.37	6.25		0.0452	1.7	0.3263	6.0 0.05230 5.8 0.29 285	5	287	15	131	96
	a261	307437 8298 190.6 0.05 61.23 0.0049	9.1	0.0332 14.5 0.04938 11.3 0.63	31	3	33	5	263	19
	a262	7184	355	19.4	1.00	1.60		0.0405	2.3	0.2954	4.7 0.05296 4.1 0.48 256	6	263	11	94	78
	a263	39557 1660	79.1	0.33	8.55		0.0393	1.8	0.2860	8.0 0.05278 7.8 0.22 249	4	255	18	177	78
	a264	26277 1993 103.6 0.51	0.18		0.0480	1.4	0.3502	1.8 0.05287 1.2 0.76 302	4	305	5	26	94
	a265	6709	285	15.3	0.47	4.93		0.0453	1.6	0.3263	5.4 0.05228 5.1 0.30 285	5	287	13	117	96
	a266	27205	864	51.3	0.19	8.52		0.0501	2.5	0.3760	8.9 0.05443 8.5 0.28 315	8	324	25	191	81
	a267	25426 1861	96.1	0.41	0.80		0.0495	1.5	0.3586	2.3 0.05253 1.7 0.66 311	5	311	6	39	101
	a268	5821	443	23.0	0.50	0.79		0.0500	1.6	0.3644	2.5 0.05283 1.9 0.64 315	5	316	7	43	98
	a269	8086	649	28.6	0.16	0.13		0.0460	1.5	0.3346	1.9 0.05279 1.2 0.78 290	4	293	5	27	91
	a270	9080	577	30.6	0.78	2.28		0.0435	2.3	0.3003	4.8 0.05004 4.2 0.49 275	6	267	11	97	140
	a271	14648	797	37.1	0.44	3.64		0.0398	2.1	0.2915	5.5 0.05317 5.1 0.38 251	5	260	13	116	75
	OL-13-08
	Session #2 (August 13 th , 2014)
	a86	132723 2706 168.1 0.06	0.42		0.0664	0.9	0.5301	1.2 0.05791 0.8 0.78 414	4	432	4	17	79
	a87	24139	756	21.9	0.28	4.53		0.0248	3.6	0.1793	6.3 0.05250 5.1 0.58 158	6	167	10	117	51
	a88	9127	223	15.6	0.30	b.d.		0.0702	1.1	0.5640	1.6 0.05824 1.2 0.67 438	4	454	6	25	81
	a89	8012	173	13.1	0.33	0.02		0.0766	0.9	0.6001	1.6 0.05681 1.4 0.52 476	4	477	6	31	98
	a90	17051	290	26.2	0.37	b.d.		0.0901	0.8	0.7290	1.1 0.05869 0.8 0.67 556	4	556	5	18	100
	a91	20271	259	21.8	0.20	2.70		0.0836	1.0	0.6793	3.9 0.05896 3.7 0.25 517	5	526	16	81	91
	a92	75314 1854	87.8	0.04	2.05		0.0491	0.6	0.3559	2.7 0.05261 2.6 0.23 309	2	309	7	60	99
	a93	17613	352	19.0	0.59	5.42		0.0461	1.5	0.3796	6.6 0.05970 6.4 0.23 291	4	327	18	138	49
	a94	12135	156	13.9	0.35	0.73		0.0871	0.9	0.6894	3.4 0.05743 3.3 0.27 538	5	532	14	71	106
	a95	32420 1223	55.9	0.05	0.02		0.0495	1.1	0.3592	1.3 0.05262 0.6 0.88 312	3	312	3	14	100
	a96	9751	195	13.4	0.33	1.22		0.0677	0.8	0.5423	2.6 0.05812 2.4 0.32 422	3	440	9	53	79
	a97	14311	540	26.2	0.26	0.00		0.0498	0.9	0.3617	1.6 0.05265 1.3 0.60 313	3	313	4	29	100
	a98	109557 2565 119.4 0.04	2.94		0.0472	0.9	0.3416	3.6 0.05254 3.5 0.24 297	2	298	9	80	96
	a99	83214 1626	95.9	0.90	1.21		0.0493	0.9	0.3580	2.3 0.05271 2.1 0.40 310	3	311	6	47	98
	a100	12600	208	18.4	0.32	0.08		0.0891	0.9	0.7217	1.4 0.05877 1.1 0.65 550	5	552	6	23	98
	a106	68329	271	66.2	0.62	0.38		0.2194	1.4	3.1122	1.7 0.10289 1.0 0.83 1279	17	1436	13	1677	18	76
	a107	122168 1381 113.9 0.04	3.95		0.0817	1.1	0.6578	4.2 0.05837 4.1 0.26 506	5	513	17	89	93
	a108	8780	297	15.2	0.34	0.03		0.0516	0.9	0.3760	1.8 0.05289 1.6 0.48 324	3	324	5	36	100
	a109	120114 2561 145.4 0.51	5.11		0.0511	0.9	0.3726	5.6 0.05290 5.6 0.16 321	3	322	16	126	99
	a110	61608 1225	51.9	0.39	5.28		0.0379	2.0	0.2740	6.2 0.05245 5.9 0.32 240	5	246	14	135	79
	a111	57111 1297	44.7	0.14 16.71 0.0305	2.4	0.2238 12.0 0.05322 11.7 0.20 194	5	205	22	266	57
	a112	14039	241	20.8	0.25	0.02		0.0882	0.9	0.7140	1.3 0.05870 0.9 0.70 545	5	547	6	20	98
	a113	71625	196	60.9	0.76	0.08		0.2581	0.8	4.2217	1.1 0.11864 0.7 0.76 1480	11	1678	9	1936	13	76
	a114	17360	490	33.1	1.04	0.11		0.0579	0.8	0.4283	1.3 0.05367 1.1 0.57 363	3	362	4	25	102
	a115	18221	304	25.9	0.10	0.07		0.0902	0.9	0.7314	1.2 0.05880 0.8 0.75 557	5	557	5	17	100
	a116	68943	542	92.4	0.61	0.07		0.1594	0.7	1.5596	1.0 0.07098 0.7 0.69 953	6	954	6	15	100
	a117	731345 880	437.1 0.48	b.d.		0.4569	0.6	10.724	0.7 0.17022 0.3 0.92 2426	12	2499	6	2560	4	95
	a118	16700	41	17.8	1.66	0.05		0.3322	1.0	5.1603	1.3 0.11265 0.8 0.77 1849	16	1846	11	1843	15	100
	a119	19706	424	31.2	0.19	0.01		0.0768	0.9	0.6006	1.3 0.05671 1.0 0.69 477	4	478	5	22	99
	a120	55645 1741	91.8	0.41	b.d.		0.0525	0.6	0.3914	1.0 0.05411 0.7 0.67 330	2	335	3	16	88
	a121	70588	674	91.4	0.22	0.03		0.1387	1.0	1.2871	1.1 0.06729 0.5 0.89 837	8	840	6	11	99
	a122	31090	984	46.1	0.08	0.44		0.0498	0.9	0.3621	1.6 0.05276 1.3 0.57 313	3	314	4	30	98
	a123	11769	181	18.7	0.75	0.05		0.0936	0.9	0.7703	1.5 0.05966 1.1 0.64 577	5	580	6	24	98
	a124	85846 2625 120.9 0.04	0.57		0.0496	0.7	0.3588	1.3 0.05250 1.1 0.55 312	2	311	4	26	101
	a125	52574	501	30.7	0.07 10.68 0.0507	2.5	0.3963	7.7 0.05671 7.2 0.33 319	8	339	22	160	66
	a126	22164	337	27.9	0.08	1.33		0.0860	0.8	0.7021	2.1 0.05919 2.0 0.37 532	4	540	9	43	93
	a127	36726	583	33.3	0.75	7.65		0.0486	1.3	0.3570	6.9 0.05331 6.8 0.19 306	4	310	19	154	89
	a128	160789 2602 216.2 0.02	1.48		0.0879	1.0	0.7054	2.1 0.05822 1.9 0.47 543	5	542	9	41	101

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)		238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	OL-13-09
	Session #1 (April 9 th , 2014)
	a06	6229	424	15.2	0.31	0.25		0.0496	1.6	0.3601	3.9 0.05260 3.6 0.41 312	5	11	312	82	100
	a07	5941	215	62.8	0.16	0.16		0.0868	1.8	0.7001	3.6 0.05847 3.1 0.50 537	9	15	547	68	98
	a08	11689	387	134.5 0.54	0.17		0.0915	1.6	0.7462	2.8 0.05915 2.3 0.56 564	8	12	572	50	99
	a09	32399	864	261.3 0.16	2.01		0.0869	1.8	0.6958	3.5 0.05809 3.0 0.50 537	9	15	533	66	101
	a10	75497 2225 651.4 0.04	1.35		0.0880	1.5	0.7056	2.3 0.05816 1.8 0.64 544	8	10	536	39	101
	a11	125517 3193 967.4 0.04	2.58		0.0888	1.4	0.7165	3.3 0.05854 2.9 0.44 548	7	14	550	64	100
	a12	17135	583	163.5 0.09	0.50		0.0846	1.6	0.6773	2.0 0.05808 1.2 0.80 523	8	8	533	27	98
	a13	94422 3157 862.5 0.02	0.30		0.0848	1.5	0.6789	1.7 0.05807 0.8 0.90 525	8	7	532	16	99
	a15	29835	738	222.2 0.73	5.00		0.0661	1.6	0.5178	6.5 0.05680 6.3 0.25 413	6	23	484	140	85
	a16	34535 1245 239.1 0.21	6.54		0.0496	1.8	0.3634	6.0 0.05319 5.7 0.31 312	6	16	337	130	93
	a17	58537 1167 298.6 0.76 10.93 0.0500	1.8	0.3625	6.9 0.05263 6.6 0.26 314	6	19	313	150	100
	a18	87595 4274 771.3 0.23	3.76		0.0490	1.5	0.3567	4.5 0.05276 4.3 0.34 309	5	12	319	97	97
	a19	8290	307	91.4	0.16	0.15		0.0888	1.8	0.7204	2.2 0.05884 1.3 0.80 548	9	10	561	29	98
	a20	79090 2095 649.0 0.23	1.98		0.0862	1.6	0.6912	3.1 0.05817 2.7 0.51 533	8	13	536	58	99
	a21	51266 1846 516.4 0.04	0.19		0.0870	1.4	0.6946	1.5 0.05790 0.6 0.92 538	7	6	526	13	102
	a22	28606	873	254.0 0.08	1.32		0.0867	1.7	0.6994	2.5 0.05851 1.8 0.68 536	9	10	549	39	98
	a24	207338 784	437.6 0.17 20.91 0.0504	2.7	0.3642	5.8 0.05240 5.2 0.46 317	8	16	303	118	105
	a26	19363	772	198.3 0.09	0.31		0.0785	1.6	0.6259	1.9 0.05781 1.1 0.82 487	7	8	523	25	93
	a28	31144 1104 322.5 0.14	1.26		0.0864	1.5	0.6997	2.5 0.05875 2.0 0.59 534	8	11	558	44	96
	a30	64226 1806 484.1 0.08	3.51		0.0779	1.7	0.6117	4.3 0.05693 3.9 0.40 484	8	17	489	87	99
	a31	99800 3444 988.6 0.05	0.31		0.0892	1.5	0.7222	1.6 0.05870 0.6 0.94 551	8	7	556	12	99
	a32	15163	378	151.6 0.43	0.74		0.1084	1.9	0.9392	2.7 0.06283 1.9 0.71 664	12	14	702	41	94
	a38	19889	599	143.1 0.32	4.94		0.0625	1.8	0.4545	5.6 0.05275 5.3 0.32 391	7	18	318	121	123
	a39	9761	280	89.2	0.36	0.83		0.0889	1.9	0.7166	2.8 0.05844 2.0 0.69 549	10	12	546	44	101
	a40	60484 1221 308.9 0.75 10.91 0.0504	1.9	0.3650	8.3 0.05257 8.1 0.23 317	6	23	310	184	102
	OL-13-11
	Session #2 (August 13	th , 2014)
	a129	58162 1001	53.0	0.19	5.38		0.0498	1.0	0.3634	5.5 0.05290 5.4 0.19 313	3	15	325	122	97
	a130	128489 1147	76.8	0.59 14.45 0.0483	2.0	0.3581	8.6 0.05376 8.4 0.23 304	6	23	361	189	84
	a131	8341	165	13.6	0.64	b.d.		0.0742	1.8	0.8263	4.3 0.08073 3.9 0.42 462	8	20	1215	77	38
	a132	303874 6040 153.2 0.23 18.82 0.0182	2.5	0.1316	8.6 0.05247 8.2 0.30 116	3	10	306	186	38
	a133	21177	582	32.8	0.45	0.69		0.0543	0.6	0.4287	1.6 0.05724 1.5 0.39 341	2	5	501	33	68
	a134	144076 529	101.4 0.13	0.70		0.1898	0.9	2.9639	1.1 0.11328 0.7 0.80 1120	9	1398	9	1853	12	60
	a135	15341	391	22.8	0.62	1.04		0.0536	0.7	0.3985	2.3 0.05397 2.2 0.32 336	2	7	370	49	91
	a136	207569 1868	90.1	0.50 31.73 0.0281	3.7	0.2158 11.7 0.05570 11.1 0.32 179	7	21	441	247	41
	a137	16868	396	21.9	0.51	1.81		0.0509	0.9	0.4120	4.3 0.05867 4.2 0.21 320	3	13	555	93	58
	a138	120401 1459	68.9	0.37 20.48 0.0334	2.8	0.2429	9.8 0.05269 9.3 0.29 212	6	20	316	213	67
	a139	28659	313	22.7	0.24	5.87		0.0653	1.4	0.5742	6.1 0.06374 5.9 0.23 408	6	23	733	126	56
	a140	65007	870	75.2	0.57	3.83		0.0765	1.1	0.5975	4.6 0.05664 4.4 0.24 475	5	18	477	98	100
	a141	56605 1188	88.0	0.44	b.d.		0.0720	0.6	0.5852	0.8 0.05892 0.5 0.81 448	3	3	564	10	79
	a142	19207	133	11.4	1.36 15.93 0.0502	1.8	0.3652	7.7 0.05276 7.5 0.24 316	6	21	318	170	99
	a143	13265	290	20.9	0.17	0.00		0.0755	0.6	0.6100	1.1 0.05856 0.9 0.57 469	3	4	551	19	85
	a144	12741	283	15.3	0.61	2.81		0.0500	0.9	0.3674	5.3 0.05331 5.3 0.17 314	3	15	342	119	92
	a150	24602	486	27.0	0.20	3.15		0.0541	0.8	0.4022	3.7 0.05396 3.6 0.23 339	3	11	370	82	92
	a151	86435	181	78.6	0.84	b.d.		0.3732	1.1	6.5956	1.3 0.12819 0.8 0.82 2044	19	2059	12	2073	13	99
	a152	15728	243	20.4	0.12	0.88		0.0871	0.8	0.7039	1.8 0.05863 1.6 0.43 538	4	7	553	35	97
	a153	162191 1134	71.0	0.88 23.10 0.0329	2.9	0.2362 10.5 0.05208 10.1 0.28 209	6	21	289	230	72
	a154	5163	80	9.9	1.66	0.11		0.0951	0.8	0.7774	1.8 0.05930 1.6 0.45 586	4	8	578	35	101
	a155	92870 1618	68.5	0.41	7.54		0.0330	1.3	0.2426	6.4 0.05337 6.2 0.21 209	3	13	345	141	61
	a156	217355 3843	83.5	0.26 19.72 0.0132	2.4	0.0964	8.7 0.05280 8.3 0.27	85	2	93	8	320	190	26
	a157	102226 875	65.6	0.54 16.74 0.0548	2.2	0.4092	8.4 0.05412 8.1 0.27 344	7	25	376	182	92
	a158	51654	853	53.1	0.96	8.00		0.0500	1.3	0.3575	7.2 0.05186 7.1 0.19 315	4	19	279	162	113
	a159	479324 2660 135.0 0.24 51.78 0.0160	5.4	0.1198 15.7 0.05441 14.7 0.35 102	6	17	388	330	26
	a160	21952	637	22.9	0.22	2.70		0.0350	1.0	0.2511	3.6 0.05205 3.5 0.28 222	2	7	288	80	77
	a161	25211	305	18.9	0.43 13.23 0.0505	1.8	0.3643	9.4 0.05236 9.2 0.19 317	6	26	301	209	105
	a162	21734	641	35.5	0.62	0.42		0.0516	0.9	0.4126	1.5 0.05801 1.2 0.59 324	3	4	530	26	61
	a163	51125	380	17.6	0.07 26.35 0.0240	3.2	0.1763	9.9 0.05326 9.4 0.32 153	5	15	340	212	45
	OL-13-14
	Session #1 (April 9	th , 2014)
	a108	60112.4 1436 331.7 0.08	7.18		0.0607	1.9	0.4739	4.6 0.05665 4.2 0.42 380	7	15	478	92	79
	a109	312949 4032 904.3 0.06 31.34 0.0461	3.4	0.3405	9.8 0.05361 9.1 0.35 290	10	25	355	206	82
	a110	13263	509	134.8 0.50	b.d.		0.0743	1.5	0.6000	2.1 0.05853 1.5 0.71 462	7	8	550	33	84
	a111	30021 1149 304.9 0.07	0.05		0.0857	1.4	0.6902	1.7 0.05840 0.9 0.85 530	7	7	545	20	97
	a112	19306 1554 216.1 0.22	1.55		0.0471	1.5	0.3444	3.8 0.05303 3.5 0.39 297	4	10	330	80	90

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)		238 U (Ma) 235 U (Ma) 206 Pb (Ma) (%)
	a113	32467	631	172.9 0.08 11.52 0.0722	1.9	0.5526	7.9 0.05553 7.7 0.23 449	8	447	29	172	104
	a114	124530 1860 359.2 0.22 31.10 0.0509	5.1	0.3680 12.5 0.05243 11.4 0.41 320	16	318	35	261	105
	a115	150794 2768 419.4 0.04 36.94 0.0239	4.3	0.1749 10.6 0.05319 9.6 0.41 152	7	164	16	218	45
	a116	118973 396	527.5 0.64	0.10		0.3410	1.9	7.4500	1.9 0.15846 0.3 0.98 1891	31	2167	17	2439	6	78
	a117	9819	334	108.7 0.34	0.13		0.0965	1.5	0.7957	2.0 0.05978 1.3 0.75 594	8	594	9	29	100
	a118	70216 1544 241.0 0.23 45.11 0.0259	5.1	0.4517 10.7 0.12630 9.4 0.48 165	8	378	34	2047 166	8
	a120	8122	300	82.1	0.11	0.35		0.0870	1.7	0.6980	2.2 0.05820 1.4 0.78 538	9	538	9	30	100
	a121	15993	660	160.0 0.20	1.25		0.0757	1.7	0.5842	3.0 0.05594 2.5 0.57 471	8	467	11	55	105
	a122	6839	242	67.0	0.13	0.13		0.0878	1.5	0.7061	1.9 0.05831 1.2 0.77 543	8	542	8	26	100
	a123	31758	709	176.6 0.13	7.59		0.0682	1.9	0.5213	7.5 0.05545 7.2 0.26 425	8	426	26	161	99
	a124	14377	519	150.8 0.29	0.29		0.0872	1.6	0.7012	1.9 0.05835 1.0 0.84 539	8	540	8	22	99
	a125	444834 3784 954.6 0.06 52.28 0.0252	5.6	0.1851 13.3 0.05334 12.1 0.42 160	9	172	21	274	47
	a126	618828 10120 1133.4 0.10 78.46 0.0051	8.1	0.0430 14.7 0.06078 12.2 0.55	33	3	43	6	263	5
	a127	27372 1005 265.2 0.08	0.23		0.0850	1.5	0.6815	1.7 0.05817 0.8 0.88 526	8	528	7	17	98
	a128	28546	737	240.5 0.39	1.97		0.0899	1.6	0.7407	3.4 0.05972 3.0 0.46 555	8	563	15	66	94
	a129	272602 2283 692.7 0.26 48.48 0.0352	5.2	0.3027 13.8 0.06230 12.7 0.38 223	11	269	33	272	33
	a130	1007391 8985 1799.9 0.10 75.45 0.0080	8.0	0.0643 14.1 0.05853 11.6 0.57	51	4	63	9	254	9
	a131	41003 1429 374.0 0.05	0.98		0.0839	1.8	0.6726	2.3 0.05817 1.4 0.79 519	9	522	9	31	97
	a132	877003 8624 1610.4 0.10 77.18 0.0087	7.9	0.0706 13.6 0.05877 11.1 0.58	56	4	69	9	242	10
	a133	21784	899	221.3 0.12	0.70		0.0770	1.6	0.6336	2.3 0.05969 1.6 0.72 478	8	498	9	34	81
	a134	45603 1265 194.2 0.17 11.95 0.0350	2.9	0.2787	7.8 0.05782 7.2 0.38 222	6	250	17	158	42
	a135	1009967 10394 1779.8 0.09 77.97 0.0059	8.5	0.0475 14.5 0.05821 11.7 0.59	38	3	47	7	255	7
	a136	10475	420	112.0 0.07	0.28		0.0863	1.8	0.6940	2.3 0.05831 1.4 0.80 534	9	535	9	30	99
	a137	23120	619	262.5 0.64	0.93		0.1136	1.5	0.9714	2.7 0.06204 2.3 0.55 693	10	689	14	49	103
	Session #2 (August 13	th , 2014)
	a275	11205	194	17.4	0.76	0.75		0.0822	0.9	0.6684	2.5 0.05899 2.4 0.35 509	4	520	10	52	90
	a276	42242	380	33.9	0.24	6.04		0.0833	1.0	0.6751	6.2 0.05877 6.1 0.16 516	5	524	26	133	92
	a278	14296	156	21.7	1.04	0.04		0.1172	0.8	1.0538	1.2 0.06520 1.0 0.63 715	5	731	7	20	92
	a279	29020	40	18.3	0.94	b.d.		0.3720	1.1	8.0851	1.3 0.15762 0.8 0.81 2039	19	2241	12	2430	13	84
	a280	55475	103	44.9	1.51	b.d.		0.3298	1.1	7.1295	1.3 0.15679 0.8 0.81 1837	17	2128	12	2421	13	76
	a281	20192	313	31.2	0.84	0.74		0.0885	0.8	0.7098	2.5 0.05817 2.4 0.32 547	4	545	11	53	102
	a287	23328	369	32.9	0.09	0.04		0.0949	0.6	0.7854	0.9 0.06002 0.7 0.70 584	4	589	4	14	97
	a288	177320 839	66.7	0.55 28.18 0.0411	3.1	0.3043 10.6 0.05365 10.1 0.29 260	8	270	25	229	73
	a291	176216 1276	81.8	0.25 19.07 0.0431	2.2	0.3119	8.5 0.05249 8.2 0.25 272	6	276	21	188	89
	a292	77660 1030	49.1	0.30 12.00 0.0371	1.5	0.2736	7.3 0.05344 7.2 0.21 235	4	246	16	163	68
	a293	288541 1761	87.3	0.06 31.77 0.0225	3.6	0.1651	9.7 0.05320 9.1 0.36 143	5	155	14	206	43
	a294	48717	705	40.5	0.28	9.32		0.0505	1.3	0.3712	7.2 0.05334 7.1 0.18 317	4	321	20	161	92
	a295	257214 3406 174.6 0.08 12.30 0.0438	1.5	0.3208	7.6 0.05317 7.4 0.20 276	4	283	19	168	82
	a296	149611 1180	74.2	0.32 18.92 0.0426	2.2	0.3096	8.4 0.05267 8.1 0.26 269	6	274	20	185	86
	a297	49681	744	62.6	0.06	0.59		0.0895	0.8	0.7231	1.5 0.05857 1.3 0.55 553	4	553	7	28	100
	a300	194946 1072	80.6	0.04 15.25 0.0518	2.8	0.3750	9.1 0.05252 8.7 0.30 325	9	323	26	198	106
	a301	52899	857	71.0	0.04	0.13		0.0893	0.8	0.7191	1.3 0.05840 0.9 0.66 551	4	550	5	21	101
	a302	4731	53	6.7	0.59	0.04		0.1211	0.8	1.0704	1.8 0.06413 1.7 0.44 737	6	739	10	35	99
	a303	105046 2357 132.1 0.60	1.24		0.0505	1.2	0.3675	2.3 0.05276 1.9 0.53 318	4	318	6	44	100
	a304	186366 1295 124.6 0.37	8.89		0.0774	1.5	0.6583	6.2 0.06168 6.0 0.24 481	7	514	25	129	72
	OL-13-21
	Session #1 (April 9 th , 2014)
	a208	25973 1258	73.1	0.08	1.55		0.0588	1.8	0.4366	3.5 0.05386 3.0 0.52 368	7	368	11	67	101
	a209	94826	745	109.5 0.25 20.64 0.0905	2.7	0.9251	9.0 0.07414 8.5 0.30 558	14	665	45	1045 172	53
	a210	50150 2276 115.8 0.06	6.29		0.0499	1.6	0.3661	7.1 0.05316 7.0 0.22 314	5	317	20	158	94
	a211	35328 2918 133.3 0.06	1.78		0.0477	1.7	0.3499	3.7 0.05319 3.3 0.46 300	5	305	10	75	89
	a212	141261 8848 468.9 0.12	1.72		0.0540	2.0	0.3922	3.6 0.05268 2.9 0.56 339	7	336	10	67	108
	a213	55960 3598 192.2 0.17	0.62		0.0544	1.6	0.3996	2.1 0.05328 1.3 0.77 341	5	341	6	30	100
	a214	48793 3065 161.1 0.17	0.99		0.0531	1.8	0.3889	2.6 0.05310 1.9 0.69 334	6	334	7	42	100
	a215	14902	728	50.0	0.26	0.25		0.0690	1.8	0.5480	2.2 0.05763 1.2 0.83 430	8	444	8	27	83
	a216	84786 4802 262.8 0.23	1.44		0.0541	1.5	0.4008	2.5 0.05370 2.0 0.61 340	5	342	7	45	95
	a217	204546 14729 715.8 0.08	0.65		0.0512	1.8	0.3734	2.0 0.05287 1.0 0.86 322	6	322	6	24	100
	a218	52703 2819 168.6 0.65	1.83		0.0531	1.5	0.3870	3.1 0.05291 2.7 0.48 333	5	332	9	61	103
	a219	28541	284	56.3	0.44	2.18		0.1773	1.9	2.1854	2.7 0.08939 2.0 0.69 1052	18	1176	19	1412	38	75
	a220	13100	510	43.3	0.36	0.77		0.0802	2.0	0.6511	3.5 0.05888 2.8 0.59 497	10	509	14	61	88
	a221	53089 1556	93.9	0.15	9.07		0.0520	1.9	0.3817	6.7 0.05321 6.4 0.28 327	6	328	19	145	97
	a222	22163 1335	63.6	0.18	1.04		0.0481	1.6	0.3534	2.6 0.05327 2.0 0.63 303	5	307	7	45	89
	a223	162839 2242 195.2 0.49 19.72 0.0547	2.7	0.3937	8.8 0.05218 8.4 0.31 343	9	337	26	192	117
	a224	72533 3603 190.4 0.06	2.48		0.0537	1.7	0.3901	3.5 0.05272 3.1 0.49 337	6	334	10	70	106
	a225	110208 6097 377.8 0.71	1.94		0.0531	1.6	0.3910	3.1 0.05337 2.7 0.52 334	5	335	9	60	97
	a226	8202	592	30.9	0.36	0.13		0.0513	1.4	0.3772	1.7 0.05336 0.9 0.84 322	4	325	5	21	94
	a227	35106	254	75.8	0.76	2.40		0.2510	1.7	3.2149	2.7 0.09290 2.2 0.61 1444	22	1461	21	1486	41	97

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)		238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a228	25716 1417	82.0	0.28	1.02		0.0546	1.9	0.4028	3.0 0.05347 2.4 0.62 343	6	9	349	53	98
	a229	18194	755	43.3	0.52	4.57		0.0484	1.9	0.3596	5.6 0.05386 5.2 0.33 305	6	15	365	118	83
	a230	59460 3876 212.4 0.36	0.73		0.0530	1.7	0.3867	2.3 0.05288 1.5 0.75 333	5	6	324	34	103
	a231	49350 1543 141.5 0.36	2.00		0.0860	1.7	0.6922	3.3 0.05839 2.8 0.52 532	9	14	544	61	98
	a232	81630 5253 259.5 0.23	0.62		0.0500	1.6	0.3705	2.2 0.05372 1.5 0.73 315	5	6	359	34	88
	a233	158821 3338 225.2 0.05 14.04 0.0532	2.4	0.3887	8.1 0.05297 7.7 0.30 334	8	23	327	175	102
	OL-13-24
	Session #1 (April 9 th , 2014)
	a171	13614	819	142.8 0.42	0.76		0.0502	1.7	0.3690	2.9 0.05330 2.3 0.58 316	5	8	341	53	93
	a172	25806 1557 270.5 0.31	1.21		0.0511	1.8	0.3724	3.5 0.05285 3.0 0.53 321	6	10	323	67	100
	a173	31595 1754 336.1 0.75	1.62		0.0507	1.6	0.3695	3.4 0.05284 3.0 0.47 319	5	9	322	68	99
	a174	11370	705	114.4 0.26	0.64		0.0497	1.9	0.3644	3.2 0.05320 2.5 0.61 313	6	9	337	57	93
	a175	65424 2242 487.4 0.82	6.22		0.0504	2.0	0.3691	6.4 0.05317 6.1 0.31 317	6	18	336	137	94
	a176	45346 1968 347.0 0.19	4.53		0.0507	1.5	0.3699	5.2 0.05290 5.0 0.28 319	5	14	324	114	98
	a177	29214 1758 326.8 0.78	0.83		0.0495	1.4	0.3618	2.7 0.05300 2.3 0.52 312	4	7	329	53	95
	a178	12217	827	155.8 0.72	0.63		0.0513	1.5	0.3739	3.0 0.05291 2.5 0.52 322	5	8	325	57	99
	a179	72217 3509 637.1 0.31	3.08		0.0518	1.5	0.3770	3.9 0.05282 3.6 0.39 325	5	11	321	82	101
	a180	39183 1526 289.8 0.35	6.50		0.0509	1.9	0.3710	6.1 0.05284 5.8 0.32 320	6	17	322	131	99
	a181	37278 2656 591.0 1.43	b.d.		0.0510	1.5	0.3725	2.0 0.05294 1.4 0.74 321	5	6	326	31	98
	a182	13284	881	150.7 0.42	0.49		0.0507	1.7	0.3699	3.0 0.05295 2.4 0.58 319	5	8	327	55	98
	a183	90814 3715 680.4 0.21	6.74		0.0516	1.5	0.3765	5.9 0.05296 5.7 0.26 324	5	17	327	129	99
	a184	28452 1491 285.0 0.58	3.03		0.0508	1.8	0.3711	4.9 0.05296 4.5 0.36 320	6	14	327	103	98
	a185	34271 2703 469.7 0.47	0.03		0.0503	1.5	0.3720	1.8 0.05365 1.0 0.84 316	5	5	356	23	89
	a186	17569 1187 225.9 0.78	0.39		0.0503	1.5	0.3677	2.2 0.05306 1.7 0.66 316	5	6	331	38	95
	a187	10532	682	124.1 0.68	0.50		0.0507	1.7	0.3708	4.2 0.05302 3.8 0.40 319	5	12	330	87	97
	a188	33495 2399 424.6 0.43	1.05		0.0517	1.7	0.3767	2.6 0.05290 1.9 0.67 325	5	7	324	44	100
	a189	6618	485	91.3	0.65	b.d.		0.0521	1.5	0.3805	3.0 0.05295 2.6 0.50 327	5	8	327	59	100
	a190	6809	529	101.2 0.78	b.d.		0.0505	1.8	0.3684	3.9 0.05290 3.5 0.46 318	6	11	325	79	98
	a191	69652 4627 784.0 0.24	0.99		0.0515	1.4	0.3744	2.2 0.05274 1.7 0.64 324	4	6	318	38	102
	a192	5898	420	85.5	0.94	0.37		0.0511	1.5	0.3728	3.7 0.05288 3.4 0.39 321	5	10	324	78	99
	a193	13057	778	141.3 0.72	1.10		0.0493	1.5	0.3575	3.6 0.05254 3.2 0.43 310	5	10	309	74	100
	a199	41316 2818 101.9 0.45	0.63		0.0519	1.5	0.3786	2.2 0.05289 1.6 0.68 326	5	6	324	37	101
	a200	6303	286	21.1	0.63	2.16		0.0482	1.6	0.3481	4.1 0.05241 3.8 0.39 303	5	11	303	87	100
	a201	23402 1536 110.0 0.35	0.94		0.0510	1.4	0.3711	2.7 0.05279 2.3 0.53 321	4	7	320	52	100
	a202	4417	315	10.4	0.23	0.52		0.0506	1.6	0.3683	2.4 0.05277 1.8 0.66 318	5	6	319	40	100
	a203	4364	295	54.3	0.49	b.d.		0.0519	2.2	0.3811	6.4 0.05326 6.0 0.34 326	7	18	340	136	96
	a204	13133	978	167.9 0.53	0.49		0.0478	1.6	0.3491	2.4 0.05292 1.9 0.65 301	5	6	325	42	93
	a205	14768	545	116.6 0.71	5.31		0.0513	1.7	0.3740	6.6 0.05288 6.4 0.26 322	5	18	324	144	100
	a206	6976	477	86.6	0.46	0.26		0.0526	1.7	0.3837	3.6 0.05292 3.2 0.46 330	5	10	325	73	102
	a207	19169 1093 107.4 0.26	1.13		0.0498	1.4	0.3629	2.6 0.05288 2.2 0.54 313	4	7	324	50	97
	PMV
	Session #2 (August 13	th , 2014)
	a433	42475	888	41.9	0.16	1.59		0.0479	1.2	0.3509	4.7 0.05316 4.5 0.26 301	4	12	336	102	90
	a436	5232	134	7.0	0.89	b.d.		0.0475	1.6	0.3434	3.0 0.05249 2.5 0.55 299	5	8	307	57	97
	a437	59939 1566	71.9	0.17	0.20		0.0481	1.1	0.3478	1.3 0.05239 0.7 0.85 303	3	3	303	15	100
	a444	23304	809	35.8	0.26	0.30		0.0451	1.1	0.3295	5.0 0.05305 4.9 0.22 284	3	13	331	111	86
	a445	5288	144	7.7	0.97	0.52		0.0461	1.3	0.3433	2.0 0.05396 1.6 0.62 291	4	5	369	36	79
	a446	6115	182	8.8	0.59	b.d.		0.0456	1.1	0.3260	2.5 0.05190 2.3 0.44 287	3	6	281	52	102
	a448	67709	941	48.8	0.21	6.00		0.0463	1.3	0.3314	7.5 0.05190 7.4 0.18 292	4	19	281	169	104
	a451	13888	608	27.5	0.13	0.30		0.0479	1.0	0.3492	1.6 0.05291 1.2 0.65 301	3	4	325	28	93
	a452	46511	837	45.4	0.77	3.33		0.0459	1.5	0.3255	5.4 0.05146 5.2 0.28 289	4	13	261	118	111
	a453	53220 1394	65.7	0.27	0.47		0.0471	1.1	0.3389	2.3 0.05218 2.0 0.49 297	3	6	293	47	101
	a454	4732	140	7.0	0.53	b.d.		0.0477	1.0	0.3462	1.9 0.05261 1.6 0.55 301	3	5	312	36	96
	a456	6616	189	9.7	1.10	b.d.		0.0444	1.8	0.3194	3.8 0.05223 3.4 0.46 280	5	9	296	77	95
	a458	26439	749	33.5	0.12	b.d.		0.0475	1.2	0.3441	1.5 0.05253 1.0 0.77 299	3	4	309	22	97
	a459	38406 1281	73.2	1.18	b.d.		0.0485	1.0	0.3490	1.2 0.05223 0.7 0.85 305	3	3	296	15	103
	a460	7034	192	10.0	0.94	4.41		0.0454	1.3	0.3347	7.5 0.05348 7.4 0.18 286	4	19	349	166	82
	a462	6169	198	9.9	0.67	b.d.		0.0462	1.4	0.3388	2.4 0.05320 1.9 0.60 291	4	6	337	43	86
	a465	4446	131	6.5	0.55	2.40		0.0477	1.0	0.3500	4.4 0.05316 4.3 0.24 301	3	12	336	97	90
	a466	53714	564	63.3	0.33	0.42		0.1130	1.0	0.9703	1.3 0.06225 0.8 0.80 690	7	7	683	17	101
	a467	19181	580	26.5	0.13	0.11		0.0484	0.9	0.3497	1.4 0.05237 1.0 0.70 305	3	4	302	22	101
	a468	18149	487	25.0	1.04	0.36		0.0445	1.7	0.3280	2.9 0.05349 2.3 0.59 280	5	7	350	52	80
	a470	5435	151	8.6	1.23	1.53		0.0472	1.1	0.3424	3.0 0.05257 2.9 0.35 298	3	8	310	65	96
	a471	6291	163	9.8	1.45	b.d.		0.0483	1.1	0.3472	1.8 0.05217 1.4 0.61 304	3	5	293	32	104
	a472	16094	205	20.6	1.21	1.31		0.0810	1.4	0.6943	2.7 0.06215 2.3 0.51 502	7	11	679	50	74
	a473	11748	372	19.3	0.75	b.d.		0.0479	1.0	0.3474	1.4 0.05263 1.0 0.72 302	3	4	313	23	96

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)		238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a474	6427	169	9.9	1.25	0.49		0.0482	1.2	0.3473	1.9 0.05230 1.5 0.63 303	4	5	299	34	101
	a475	4990	142	8.1	1.16	0.25		0.0486	1.2	0.3487	1.9 0.05209 1.5 0.62 306	4	5	289	34	106
	PRC-56
	Session #2 (August 13	th , 2014)
	a08	26600	451	27.0	0.52	4.57		0.0527	0.8	0.3836	4.7 0.05283 4.7 0.18 331	3	13	322	106	103
	a09	8022	160	10.1	0.93	2.90		0.0526	0.9	0.3863	3.9 0.05329 3.8 0.22 330	3	11	341	87	97
	a10	12516	356	19.1	0.41	0.39		0.0529	0.9	0.3849	2.2 0.05280 2.0 0.42 332	3	6	320	46	104
	a11	21855	667	35.7	0.37	b.d.		0.0534	0.7	0.3918	1.1 0.05317 0.8 0.66 336	2	3	336	18	100
	a12	5817	160	8.9	0.56	0.24		0.0524	0.9	0.3842	1.6 0.05323 1.3 0.59 329	3	4	339	29	97
	a13	5581	162	9.1	0.58	0.30		0.0532	0.9	0.3874	2.0 0.05282 1.8 0.43 334	3	6	321	42	104
	a14	30098	688	40.4	0.65	1.90		0.0531	0.8	0.3895	3.0 0.05322 2.9 0.28 333	3	9	338	66	99
	a15	5448	165	9.1	0.53	0.19		0.0530	0.8	0.3947	1.5 0.05399 1.3 0.55 333	3	4	371	29	90
	a16	9910	292	17.3	0.89	0.02		0.0529	0.8	0.3891	1.5 0.05334 1.2 0.55 332	3	4	343	28	97
	a17	7127	205	11.1	0.56	0.24		0.0512	0.7	0.3756	2.1 0.05321 2.0 0.31 322	2	6	338	45	95
	a18	19935	612	37.8	1.47	0.32		0.0483	1.8	0.3611	4.1 0.05420 3.7 0.44 304	5	11	380	83	80
	a19	9964	282	16.4	0.74	0.37		0.0525	0.8	0.3827	1.6 0.05283 1.5 0.47 330	2	5	322	33	103
	a20	9369	263	15.1	0.66	0.81		0.0531	0.8	0.3881	1.9 0.05303 1.7 0.43 333	3	5	330	39	101
	a21	15143	358	19.6	0.30	2.41		0.0529	0.7	0.3882	3.3 0.05327 3.2 0.22 332	2	9	340	73	98
	a22	5459	168	9.2	0.50	0.17		0.0529	1.0	0.3900	1.8 0.05347 1.5 0.55 332	3	5	349	33	95
	a23	6079	188	10.0	0.37	b.d.		0.0528	0.8	0.3863	1.4 0.05308 1.2 0.59 332	3	4	332	26	100
	a24	10640	283	15.9	0.60	0.40		0.0526	0.7	0.3887	1.5 0.05358 1.3 0.48 331	2	4	353	29	94
	a25	7371	228	13.1	0.74	0.13		0.0528	0.8	0.3851	1.7 0.05294 1.5 0.48 331	3	5	326	33	102
	a26	16718	430	23.7	0.47	1.15		0.0526	0.9	0.3812	2.6 0.05258 2.5 0.33 330	3	7	311	57	106
	a27	12522	364	21.8	0.95	0.03		0.0526	0.8	0.3830	1.3 0.05280 1.1 0.60 331	3	4	320	24	103
	a28	21116	475	30.1	0.94	2.26		0.0538	0.8	0.4039	3.8 0.05448 3.7 0.21 338	3	11	391	84	86
	a29	22705	436	26.9	0.76	5.53		0.0514	1.3	0.3809	6.3 0.05370 6.2 0.20 323	4	18	359	140	90
	a30	6035	186	10.5	0.65	b.d.		0.0526	0.8	0.3842	1.5 0.05303 1.3 0.51 330	2	4	330	30	100
	a31	14016	216	12.9	0.35	5.79		0.0530	1.1	0.3859	5.6 0.05276 5.5 0.20 333	4	16	318	125	105
	a32	12117	348	20.7	0.72	0.20		0.0546	0.9	0.4065	1.5 0.05402 1.3 0.58 343	3	5	372	28	92
	a38	10023	301	16.2	0.41	0.06		0.0533	0.8	0.3904	1.4 0.05312 1.2 0.55 335	3	4	334	27	100
	a39	6148	188	11.8	1.21	0.07		0.0523	0.8	0.3835	1.7 0.05313 1.6 0.44 329	2	5	335	35	98
	a40	8054	248	13.7	0.57	0.03		0.0525	0.7	0.3832	1.5 0.05291 1.3 0.46 330	2	4	325	30	102
	a41	5875	179	10.7	0.85	0.16		0.0532	0.7	0.3910	1.9 0.05332 1.8 0.37 334	2	5	342	40	98
	a42	14621	431	24.5	0.63	0.05		0.0535	0.9	0.3910	1.3 0.05297 1.0 0.69 336	3	4	328	22	103
	a43	5560	180	10.3	0.68	0.07		0.0531	0.9	0.3897	1.6 0.05320 1.3 0.55 334	3	5	337	30	99
	PRC-57
	Session #2 (August 13	th , 2014)
	a44	11228	355	19.9	0.60	b.d.		0.0531	0.7	0.3887	1.3 0.05308 1.1 0.52 334	2	4	332	25	100
	a45	12384	205	17.0	0.08	0.06		0.0887	0.8	0.7176	1.4 0.05868 1.2 0.57 548	4	6	555	25	99
	a46	12189	341	22.3	1.03	b.d.		0.0567	0.9	0.4571	2.7 0.05844 2.5 0.34 356	3	9	546	55	65
	a47	51183	552	41.2	0.88	9.13		0.0549	1.4	0.4161	6.9 0.05502 6.7 0.20 344	5	21	413	151	83
	a48	20442	566	39.2	1.10	b.d.		0.0592	0.8	0.4406	1.1 0.05400 0.8 0.71 371	3	3	371	17	100
	a49	11886	201	17.6	0.30	b.d.		0.0896	1.5	0.7291	1.9 0.05900 1.2 0.79 553	8	8	567	25	98
	a50	32899	491	43.9	0.45	0.93		0.0859	1.0	0.7024	2.3 0.05932 2.1 0.44 531	5	10	579	45	92
	a52	18096	499	34.9	1.16	b.d.		0.0586	0.7	0.4360	1.1 0.05392 0.8 0.68 367	3	3	368	18	100
	a53	16455	430	29.0	1.00	0.05		0.0583	0.7	0.4659	1.2 0.05800 0.9 0.60 365	3	4	530	21	69
	a55	10493	239	18.1	0.32	b.d.		0.0756	1.1	0.6087	1.7 0.05837 1.3 0.62 470	5	6	544	29	86
	a56	92436 1079	58.3	0.04	9.88		0.0458	1.5	0.3441	7.6 0.05448 7.4 0.20 289	4	20	391	167	74
	a57	6708	128	8.3	1.03	4.31		0.0515	0.8	0.3812	5.2 0.05367 5.1 0.15 324	3	15	357	115	91
	a58	9176	158	10.0	0.74	5.05		0.0530	1.0	0.3887	5.2 0.05320 5.1 0.18 333	3	15	337	115	99
	a59	12964	405	23.3	0.71	0.05		0.0532	0.9	0.3917	1.5 0.05336 1.1 0.64 334	3	4	344	26	97
	a60	18839	439	30.4	0.97	0.94		0.0597	0.9	0.4513	2.7 0.05484 2.5 0.34 374	3	8	406	56	92
	a61	21341	271	31.4	0.77	0.49		0.1040	0.8	0.8883	2.0 0.06195 1.9 0.37 638	5	10	672	40	95
	a62	12273	202	19.4	0.53	b.d.		0.0921	0.8	0.7521	1.2 0.05921 0.8 0.71 568	5	5	575	18	99
	a63	13489	286	17.0	0.55	1.47		0.0540	1.0	0.4186	4.5 0.05619 4.4 0.21 339	3	14	460	98	74
	a64	42521	632	46.9	1.17	4.96		0.0570	0.9	0.4589	4.8 0.05836 4.7 0.19 358	3	16	543	103	66
	a65	6434	209	12.0	0.70	0.01		0.0528	0.9	0.3899	1.8 0.05355 1.5 0.53 332	3	5	352	34	94
	a66	25432	160	14.8	0.48 11.83 0.0662	1.8	0.5543	9.2 0.06070 9.0 0.20 413	7	34	629	194	66
	a72	19959	341	29.0	0.11	b.d.		0.0902	0.9	0.7276	1.2 0.05847 0.8 0.73 557	5	5	547	18	102
	a73	15840	391	24.6	0.79	0.62		0.0557	0.8	0.4994	1.9 0.06503 1.7 0.45 349	3	6	775	35	45
	a74	21309	498	34.7	1.09	1.00		0.0577	0.7	0.4488	2.0 0.05639 1.8 0.36 362	2	6	468	41	77
	a75	40444	687	36.3	0.15	6.05		0.0488	1.0	0.3542	5.5 0.05266 5.4 0.18 307	3	15	314	122	98
	a76	88853	112	69.4	1.70	0.06		0.4606	0.8	10.221	1.0 0.16093 0.6 0.81 2442	16	2455	9	2465	10	99
	a77	11654	115	18.4	0.98	0.05		0.1386	0.7	1.2897	1.1 0.06751 0.8 0.65 837	6	6	853	17	98
	a78	17212	524	30.2	0.67	b.d.		0.0536	0.9	0.3946	1.3 0.05343 0.9 0.70 336	3	4	347	20	97
	a80	8335	280	19.4	1.96	b.d.		0.0499	0.9	0.3660	1.5 0.05322 1.2 0.58 314	3	4	338	28	93

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)		238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a81	6690	199	11.4	0.65	0.13		0.0535	0.8	0.3953	1.7 0.05354 1.5 0.48 336	3	5	352	34	96
	a83	24097	660	35.3	0.24	1.03		0.0539	0.9	0.3935	2.2 0.05292 2.0 0.41 339	3	6	325	45	104
	a84	18834	298	21.6	0.10	1.41		0.0729	1.4	0.6030	3.6 0.05998 3.4 0.37 454	6	14	603	73	75
	SDZ
	Session #2 (August 13	th , 2014)
	a476	57616 1440	77.7	0.33	0.15		0.0544	1.1	0.4008	1.2 0.05345 0.6 0.89 341	4	4	348	13	98
	a477	118329 3130 171.6 0.45	b.d.		0.0540	0.9	0.3947	1.0 0.05303 0.4 0.93 339	3	3	330	9	103
	a478	38084 1016	51.1	0.11	b.d.		0.0536	1.0	0.3921	1.2 0.05308 0.5 0.89 336	3	3	332	12	101
	a480	40714	916	46.8	0.18	b.d.		0.0534	0.9	0.3933	1.1 0.05341 0.6 0.83 335	3	3	346	14	97
	a481	69828 1848 115.3 1.18	0.81		0.0518	1.5	0.3832	3.2 0.05368 2.8 0.47 325	5	9	358	63	91
	a482	114057 3032 166.0 0.47	b.d.		0.0537	1.3	0.3940	1.4 0.05316 0.5 0.93 337	4	4	336	12	100
	a483	68928 1734	91.7	0.37	0.74		0.0515	1.6	0.3772	2.4 0.05315 1.8 0.67 324	5	7	335	41	97
	a484	60861 1433	68.9	0.14	1.19		0.0493	1.1	0.3660	3.5 0.05390 3.4 0.31 310	3	10	367	76	85
	a485	108644 1630	96.4	1.85	8.76		0.0451	2.1	0.3271	8.5 0.05258 8.3 0.24 284	6	22	311	189	92
	a486	23288	552	29.4	0.32	b.d.		0.0538	1.2	0.3966	1.4 0.05346 0.7 0.87 338	4	4	348	15	97
	a487	81501 2095 106.7 0.15	b.d.		0.0537	1.5	0.3940	1.5 0.05319 0.4 0.96 337	5	4	337	9	100
	a488	48936 1268	64.6	0.20	0.30		0.0524	1.3	0.3806	2.1 0.05265 1.7 0.62 329	4	6	314	38	105
	a490	9819	235	13.0	0.51	b.d.		0.0536	1.1	0.3945	1.6 0.05336 1.1 0.72 337	4	5	344	24	98
	a491	60722 1537	79.3	0.22	b.d.		0.0529	1.4	0.3913	1.8 0.05369 1.1 0.77 332	5	5	358	26	93
	a492	39230	950	49.2	0.18	b.d.		0.0543	0.9	0.3968	1.2 0.05300 0.7 0.79 341	3	3	329	17	104
	a493	33496	806	37.1	0.23	0.49		0.0472	1.3	0.3539	2.2 0.05437 1.8 0.57 297	4	6	386	41	77
	a499	88067 1423	66.1	0.33	6.15		0.0415	1.3	0.3019	6.1 0.05271 6.0 0.22 262	3	15	316	136	83
	a500	18632	452	26.2	0.68	b.d.		0.0540	1.7	0.3936	1.8 0.05290 0.7 0.92 339	6	5	324	16	104
	a501	16480	446	24.4	0.41	0.50		0.0540	1.2	0.3971	1.8 0.05330 1.3 0.66 339	4	5	341	30	99
	a502	31157	810	40.2	0.13	1.05		0.0522	1.3	0.3868	2.7 0.05374 2.4 0.48 328	4	8	360	53	91
	a503	44836 1138	56.3	0.29	0.83		0.0496	1.6	0.3613	2.9 0.05280 2.4 0.56 312	5	8	320	54	98
	a504	5661	73	7.6	0.85	b.d.		0.0941	1.1	0.7719	1.9 0.05951 1.6 0.57 580	6	8	586	34	99
	a505	65233 1427	74.0	0.13	2.48		0.0525	1.3	0.3863	4.5 0.05340 4.3 0.29 330	4	13	346	97	95
	a506	65980 1773	89.8	0.23	0.11		0.0518	1.0	0.3799	1.7 0.05321 1.3 0.58 325	3	5	338	31	96
	a507	35760	861	43.7	0.16	b.d.		0.0534	0.9	0.3899	1.1 0.05298 0.6 0.86 335	3	3	328	13	102
	a508	62642 1553	83.9	0.46	b.d.		0.0533	1.1	0.3912	1.4 0.05323 0.8 0.83 335	4	4	338	17	99
	a509	83198 1691	92.8	0.72	1.92		0.0496	1.3	0.3700	3.9 0.05405 3.7 0.32 312	4	11	373	83	84
	a510	27667	617	29.7	0.49	0.46		0.0448	2.0	0.3328	2.3 0.05389 1.2 0.87 282	6	6	367	26	77
	a512	90754 1951 115.5 0.72	0.52		0.0541	1.0	0.4009	2.0 0.05378 1.7 0.53 339	3	6	362	38	94
	a513	14773	218	18.8	0.62	b.d.		0.0821	1.1	0.6572	1.4 0.05805 0.9 0.75 509	5	6	532	21	96
	a514	26533	745	38.0	0.18	0.16		0.0531	1.9	0.3901	2.2 0.05332 0.9 0.90 333	6	6	342	21	97
	SGC-12-49B
	Session #1 (April 9	th , 2014)
	a228	4173	353	18.2	0.49	2.25		0.0481	1.9	0.3482	6.8 0.05248 6.5 0.29 303	6	18	306	149	99
	a229	2620	231	12.2	0.58	2.27		0.0479	1.8	0.3461	2.5 0.05243 1.8 0.71 302	5	7	304	41	99
	a230	7585	664	36.0	0.77	0.08		0.0477	1.8	0.3449	4.4 0.05249 4.1 0.41 300	5	12	307	93	98
	a231	12131	813	42.6	0.67 15.46 0.0478	1.9	0.3447	7.4 0.05236 7.1 0.26 301	6	19	317	163	95
	a232	5720	449	24.7	0.83	9.46		0.0474	1.8	0.3419	6.1 0.05230 5.8 0.30 299	5	16	299	132	100
	a233	1854	172	9.2	0.70	4.26		0.0477	1.9	0.3449	3.1 0.05244 2.4 0.62 300	6	8	305	55	99
	a234	28288	954	59.0	1.30	0.42		0.0363	2.6	0.2710 12.5 0.05408 12.3 0.21 230	6	28	375	276	61
	a235	9405	320	17.2	0.48	1.17		0.0400	2.4	0.3004 10.3 0.05445 10.0 0.23 253	6	24	390	225	65
	a236	3788	266	15.1	0.71	6.76		0.0476	2.6	0.3431 11.9 0.05228 11.6 0.22 300	8	31	314	265	96
	a237	6840	589	30.2	0.57 17.72 0.0464	1.9	0.3358	3.0 0.05248 2.3 0.63 292	5	8	306	53	95
	a243	8867	720	34.1	0.22	4.88		0.0471	1.8	0.3413	4.5 0.05251 4.1 0.41 297	5	12	308	94	97
	a244	9228	568	28.1	0.34	1.84		0.0441	2.0	0.3173	7.5 0.05223 7.2 0.26 278	5	18	296	164	94
	a245	46792 1221	71.3	0.56	1.36		0.0380	2.9	0.2741 10.2 0.05225 9.8 0.28 241	7	23	312	224	77
	a246	7499	491	24.7	0.42	b.d.		0.0455	2.0	0.3288	6.4 0.05239 6.1 0.31 287	6	16	303	138	95
	a247	10574	848	41.2	0.47	1.70		0.0447	1.9	0.3235	4.2 0.05249 3.8 0.44 282	5	10	307	86	92
	a248	236076 864	254.2 0.12	0.37		0.2482	3.0	6.0460	3.2 0.17660 1.1 0.94 1429	39	1982	28	2622	18	55
	a249	4007	354	20.0	0.66	1.26		0.0522	1.9	0.3828	3.5 0.05315 3.0 0.54 328	6	10	335	67	98
	a251	3096	270	15.2	0.54	1.06		0.0517	1.7	0.3765	2.6 0.05287 2.0 0.65 325	5	7	323	45	101
	a252	5076	377	19.2	0.41	1.34		0.0470	2.0	0.3401	7.8 0.05249 7.5 0.26 296	6	20	323	171	92
	SJV
	Session #1 (April 9	th , 2014)
	a138	6988	504	86.8	0.45	0.02		0.0497	1.5	0.3700	3.6 0.05401 3.3 0.42 313	5	10	371	74	84
	a139	6792	457	77.9	0.55	0.20		0.0484	1.5	0.3566	2.3 0.05344 1.8 0.63 305	4	6	348	41	88
	a140	101299 3787 805.1 0.85	5.61		0.0498	1.6	0.3632	5.5 0.05285 5.3 0.29 314	5	15	322	119	97
	a141	7282	479	16.7	0.21	0.39		0.0524	1.6	0.3858	2.1 0.05340 1.4 0.75 329	5	6	346	31	95
	a142	4270	303	11.2	0.55	0.24		0.0519	1.6	0.3782	2.2 0.05284 1.5 0.75 326	5	6	322	33	101
	a143	24833	495	47.2	0.35 12.77 0.0514	2.6	0.3760	7.0 0.05300 6.5 0.37 323	8	20	329	148	98

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)		238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a144	6194	405	28.3	0.31	0.69		0.0508	1.9	0.3724	3.0 0.05318 2.3 0.64 319	6	8	336	52	95
	a145	21591 1533	58.8	0.68	0.03		0.0517	1.4	0.3776	1.9 0.05294 1.2 0.75 325	4	5	326	28	100
	a151	90436 6912 1175.0 0.23	0.52		0.0531	1.4	0.3866	1.8 0.05284 1.1 0.80 333	5	5	322	24	103
	a152	10488	753	141.0 0.52	0.10		0.0537	1.5	0.3932	1.9 0.05312 1.1 0.80 337	5	5	334	25	101
	a153	4472	306	52.8	0.42	0.17		0.0511	1.7	0.3786	2.7 0.05372 2.1 0.63 321	5	8	359	48	89
	a154	4429	318	55.4	0.44	0.22		0.0510	1.7	0.3786	2.1 0.05383 1.3 0.78 321	5	6	364	30	88
	a155	31918 1988 369.7 0.63	0.80		0.0509	1.8	0.3738	2.5 0.05330 1.8 0.69 320	5	7	342	42	94
	a156	7507	508	87.0	0.44	0.35		0.0503	1.5	0.3663	2.1 0.05279 1.5 0.73 317	5	6	320	33	99
	a157	17208 1174 220.1 0.63	0.06		0.0513	1.7	0.3771	2.2 0.05326 1.5 0.75 323	5	6	340	34	95
	a158	28423 1743 340.3 0.71	0.77		0.0527	1.5	0.3864	2.2 0.05318 1.6 0.69 331	5	6	337	37	98
	a159	11799	878	171.8 0.87	0.06		0.0522	1.5	0.3842	2.8 0.05335 2.3 0.55 328	5	8	344	53	95
	a160	6155	434	76.8	0.34	0.43		0.0529	1.5	0.3889	2.3 0.05331 1.7 0.66 332	5	7	342	39	97
	a161	10603	729	123.9 0.37	0.27		0.0503	1.6	0.3678	2.6 0.05306 2.0 0.61 316	5	7	331	46	95
	a162	5645	440	78.3	0.45	0.13		0.0523	1.5	0.3835	2.1 0.05320 1.5 0.70 329	5	6	337	33	97
	a163	13671	931	166.3 0.44	0.78		0.0515	1.4	0.3756	3.1 0.05288 2.8 0.44 324	4	9	324	63	100
	a164	5417	378	67.0	0.43	0.21		0.0520	1.7	0.3810	2.3 0.05309 1.5 0.73 327	5	6	333	35	98
	a165	40817 1877 351.6 0.36	3.25		0.0526	1.5	0.3853	4.0 0.05308 3.7 0.37 331	5	11	332	83	100
	a166	5180	389	67.4	0.42	0.20		0.0522	1.8	0.3823	2.4 0.05307 1.6 0.75 328	6	7	332	36	99
	a167	17651 1002 198.9 0.33	0.05		0.0595	1.7	0.4516	2.1 0.05503 1.3 0.78 373	6	7	414	30	90
	a168	22417 1570 279.6 0.41	0.19		0.0535	1.5	0.3885	1.9 0.05272 1.1 0.81 336	5	5	317	25	106
	a169	22252 1442 258.4 0.44	0.66		0.0523	1.5	0.3801	2.4 0.05268 1.8 0.64 329	5	7	315	42	104
	a170	9067	631	109.7 0.40	b.d.		0.0513	1.5	0.3806	2.8 0.05385 2.4 0.52 322	5	8	365	54	88
	TN-10
	Session #2 (August 13	th , 2014)
	a164	26473	812	44.8	0.78	0.19		0.0500	0.8	0.3666	1.2 0.05322 0.9 0.66 314	3	3	338	21	93
	a165	15973	337	19.9	0.70	3.08		0.0519	1.1	0.3862	5.4 0.05393 5.3 0.20 326	4	15	368	119	89
	a166	35824	840	50.5	1.09	1.16		0.0500	1.1	0.3648	2.4 0.05295 2.1 0.44 314	3	7	326	49	96
	a167	269546 1280 116.4 1.24 24.35 0.0488	2.7	0.3500	8.9 0.05199 8.4 0.31 307	8	24	285	193	108
	a168	51367 1635	72.4	0.10	0.16		0.0470	0.8	0.3432	1.1 0.05295 0.8 0.71 296	2	3	327	17	91
	a169	59832	645	47.9	1.19 10.13 0.0517	1.5	0.3756	7.3 0.05265 7.1 0.21 325	5	20	314	162	104
	a171	45683 1387	68.5	0.30	0.57		0.0495	0.7	0.3563	1.3 0.05223 1.1 0.56 311	2	3	296	25	105
	a172	25752	179	32.2	0.52	b.d.		0.1716	0.8	1.7364	1.2 0.07341 0.8 0.72 1021	8	1022	7	1025	16	100
	a173	51443 1217	66.8	0.66	0.94		0.0492	1.1	0.3538	2.2 0.05215 1.9 0.49 310	3	6	292	45	106
	a174	70965	843	54.0	0.76 12.45 0.0492	1.5	0.3602	8.3 0.05309 8.1 0.18 310	4	22	332	184	93
	a175	43034 1276	65.3	0.34	0.48		0.0512	0.8	0.3730	1.5 0.05280 1.2 0.58 322	3	4	320	27	101
	a176	49571	974	48.5	0.13	4.06		0.0482	1.1	0.3508	4.4 0.05278 4.2 0.24 303	3	12	319	96	95
	a177	21899	627	39.3	1.40	1.01		0.0494	0.9	0.3603	2.2 0.05287 2.0 0.40 311	3	6	323	46	96
	a179	38572	540	54.9	0.20	b.d.		0.1051	0.9	0.8860	1.1 0.06112 0.7 0.79 644	5	5	643	15	100
	a180	39112 1085	63.4	1.08	1.27		0.0492	0.8	0.3587	2.4 0.05282 2.2 0.33 310	2	6	321	51	96
	a182	11107	99	11.4	0.65	0.01		0.0952	2.0	1.0450	2.8 0.07961 2.0 0.71 586	11	15	1187	39	49
	a183	200007 1768	99.1	0.42 16.52 0.0394	1.9	0.2903	8.4 0.05345 8.1 0.23 249	5	19	348	184	72
	a184	7099	135	13.9	0.49	1.42		0.1002	1.3	0.8545	4.5 0.06184 4.3 0.29 616	8	21	668	91	92
	a185	9431	309	17.2	0.76	b.d.		0.0512	0.8	0.3715	1.7 0.05259 1.5 0.46 322	3	5	311	35	104
	a186	46738 1551	74.8	0.37	0.82		0.0471	0.7	0.3305	2.3 0.05087 2.1 0.31 297	2	6	235	50	126
	a187	20865	630	36.3	0.97	0.52		0.0503	0.7	0.3747	2.4 0.05403 2.2 0.30 316	2	7	372	50	85
	a188	21172	163	25.9	0.29	0.05		0.1591	0.8	1.5658	1.3 0.07138 1.0 0.64 952	7	8	968	20	98
	a189	31269 1126	54.7	0.86	4.21		0.0399	1.0	0.2868	6.1 0.05218 6.0 0.16 252	2	14	293	138	86
	a190	40365 1218	79.0	1.58	0.60		0.0508	0.7	0.3683	1.8 0.05254 1.6 0.38 320	2	5	309	37	103
	a191	47060	753	66.0	0.34	0.95		0.0871	0.8	0.6990	1.8 0.05817 1.6 0.47 539	4	7	536	34	100
	a192	25219	439	26.3	1.15	5.17		0.0486	1.1	0.3597	5.9 0.05364 5.8 0.19 306	3	16	356	130	86
	a198	50121	801	42.9	0.16	5.85		0.0498	1.0	0.3611	5.5 0.05255 5.4 0.19 314	3	15	309	122	101
	a199	72018 1186	52.6	0.19	9.07		0.0388	1.4	0.2848	7.1 0.05319 7.0 0.20 246	3	16	337	158	73
	a200	14991	120	13.9	0.49	4.77		0.1012	0.9	0.8584	4.5 0.06149 4.4 0.20 622	5	21	656	94	95
	a201	88638 2305 110.7 0.37	1.91		0.0460	0.7	0.3348	2.7 0.05278 2.6 0.27 290	2	7	319	59	91
	a202	72125 1088	62.3	0.64	4.40		0.0467	1.3	0.3393	4.5 0.05266 4.4 0.28 294	4	12	314	99	94
	a204	41410	412	23.9	0.61 13.71 0.0403	1.8	0.2983 10.4 0.05368 10.3 0.18 255	5	25	357	232	71
	a205	45452 1033	59.0	0.85	2.71		0.0489	0.8	0.3573	3.7 0.05305 3.6 0.22 307	2	10	331	81	93
	a206	70961	740	44.1	0.60 12.95 0.0418	1.6	0.3118	8.5 0.05405 8.3 0.19 264	4	21	373	187	71
	TN-19
	Session #2 (August 13	th , 2014)
	a207	20807	283	30.8	0.69	0.21		0.1004	0.9	0.8351	1.4 0.06033 1.1 0.62 617	5	7	615	24	100
	a208	24428	827	45.0	1.02	0.07		0.0473	0.9	0.3455	1.2 0.05303 0.8 0.73 298	2	3	330	18	90
	a209	37542 1097	56.4	0.40	0.15		0.0509	0.6	0.3720	1.4 0.05297 1.2 0.44 320	2	4	327	28	98
	a210	12716	258	18.8	0.38	b.d.		0.0726	0.9	0.5768	1.4 0.05766 1.0 0.67 452	4	5	517	22	87
	a211	66323 1757	78.3	0.12	5.37		0.0432	1.4	0.3177	6.1 0.05333 6.0 0.23 273	4	15	343	135	79
	a212	20485	464	30.5	0.38	b.d.		0.0669	0.9	0.5415	1.2 0.05867 0.8 0.73 418	4	4	555	18	75

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)			238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a213	69311 2396	95.9	0.20	0.25		0.0413	1.0	0.3007	1.5 0.05285 1.1 0.65 261	3	4	322	26	81
	a214	51486	820	69.9	0.87	0.85		0.0776	1.1	0.6060	2.1 0.05666 1.8 0.51 482	5	8	478	40	101
	a215	76036	850	92.0	0.30	0.80		0.1092	0.9	0.9321	1.6 0.06192 1.3 0.56 668	6	8	671	28	100
	a216	53742 1748	86.8	1.21	b.d.		0.0514	1.0	0.3743	1.4 0.05283 1.0 0.71 323	3	4	322	22	100
	a217	33318	613	37.2	0.72	3.00		0.0512	0.8	0.3705	3.8 0.05252 3.7 0.20 322	2	10	308	85	104
	a218	3419	47	5.3	1.02	b.d.		0.0960	1.0	0.8254	1.9 0.06238 1.6 0.52 591	6	9	687	35	86
	a219	6143	127	9.4	0.47	b.d.		0.0721	1.2	0.5743	1.8 0.05778 1.4 0.63 449	5	7	522	32	86
	a220	17657	211	15.7	0.21	5.04		0.0694	1.0	0.5397	4.8 0.05643 4.7 0.21 432	4	17	469	104	92
	a221	11186	235	17.0	0.35	0.26		0.0721	0.8	0.5637	1.7 0.05667 1.5 0.47 449	4	6	479	33	94
	a222	34145	518	47.7	0.49	0.04		0.0923	0.7	0.7704	1.0 0.06051 0.7 0.72 569	4	5	622	16	92
	a223	3880	128	7.3	1.03	0.19		0.0491	1.0	0.3576	2.3 0.05277 2.0 0.45 309	3	6	319	46	97
	a224	16561	251	21.6	0.25	0.29		0.0882	0.8	0.7083	2.1 0.05823 2.0 0.37 545	4	9	538	44	101
	a225	19582	639	32.0	0.59	0.19		0.0473	0.8	0.3453	1.3 0.05294 1.1 0.58 298	2	3	326	24	91
	a226	31171	534	33.1	0.96	3.96		0.0518	1.6	0.3756	5.6 0.05263 5.4 0.28 325	5	16	313	123	104
	a227	21932	350	36.3	1.02	0.15		0.0899	0.8	0.7369	1.9 0.05942 1.7 0.44 555	4	8	583	37	95
	a228	30417	710	41.9	0.93	2.78		0.0497	0.8	0.3603	4.1 0.05257 4.0 0.20 313	3	11	310	91	101
	a229	3970	64	6.6	1.22	b.d.		0.0821	1.8	0.6994	2.8 0.06177 2.2 0.63 509	9	12	666	47	76
	a230	18386	457	26.9	0.09	b.d.		0.0623	0.9	0.4886	1.3 0.05686 1.0 0.70 390	3	4	486	21	80
	a231	48973 1108	55.0	0.17	1.80		0.0496	0.7	0.3608	2.8 0.05280 2.8 0.24 312	2	8	320	63	97
	a232	28938	920	49.9	0.70	0.05		0.0505	0.8	0.3685	1.0 0.05291 0.7 0.75 318	2	3	325	16	98
	a233	17393	357	25.2	0.13	0.10		0.0746	0.9	0.5847	1.4 0.05688 1.1 0.62 464	4	5	487	25	95
	a234	11443	182	11.5	0.36	0.77		0.0600	1.6	0.5366	3.6 0.06481 3.3 0.43 376	6	13	768	68	49
	a242	30216	398	41.5	0.46	b.d.		0.1015	0.9	0.8670	1.2 0.06195 0.9 0.71 623	5	6	672	18	93
	a243	54234 1739	86.6	0.24	b.d.		0.0515	0.9	0.3748	1.0 0.05274 0.5 0.90 324	3	3	318	10	102
	a244	27490	928	48.3	0.69	b.d.		0.0484	0.8	0.3528	1.0 0.05285 0.6 0.82 305	2	3	322	13	95
	TOU-01
	Session #1 (April 9 th , 2014)
	a41	21817 1309 223.6 0.16	1.19		0.0514	1.6	0.3744	2.4 0.05286 1.9 0.65 323	5	7	323	42	100
	a42	26422 1148 238.9 0.63	3.70		0.0513	1.6	0.3740	4.2 0.05287 3.9 0.38 323	5	12	323	89	100
	a43	27851 1691 296.3 0.29	0.82		0.0509	1.5	0.3712	2.2 0.05292 1.7 0.66 320	5	6	325	38	98
	a44	23042 1401 245.3 0.42	1.29		0.0481	1.4	0.3504	2.5 0.05286 2.0 0.58 303	4	7	323	46	94
	a45	41263 1859 333.9 0.23	3.53		0.0475	1.9	0.3441	4.8 0.05249 4.4 0.40 299	6	13	307	101	98
	a47	33889 2057	80.1	0.67	0.63		0.0502	1.7	0.3656	3.1 0.05283 2.5 0.57 316	5	8	321	58	98
	a48	139822 1593 163.6 0.22	1.87		0.1407	1.4	1.6673	2.5 0.08595 2.1 0.55 849	11	16	1337	41	63
	a49	18111 1066	79.4	0.37	1.30		0.0502	1.7	0.3653	2.9 0.05278 2.3 0.59 316	5	8	319	53	99
	a50	12398	856	60.2	0.21	0.03		0.0512	1.4	0.3736	2.0 0.05291 1.5 0.69 322	4	6	325	33	99
	a51	32661 2014	70.0	0.19	1.51		0.0507	1.5	0.3702	3.2 0.05290 2.9 0.46 319	5	9	325	66	98
	a52	30438 1939 320.3 0.11	1.18		0.0502	1.4	0.3656	2.4 0.05278 2.0 0.58 316	4	7	319	45	99
	a53	134778 396	628.5 0.74	0.36		0.3762	1.9	8.7952	2.0 0.16958 0.6 0.96 2058	34	2317	19	2553	10	81
	a54	33192	961	415.0 1.57	1.48		0.0876	1.9	0.7033	3.4 0.05825 2.8 0.57 541	10	14	539	61	100
	a55	57948 1123 400.2 0.16	0.00		0.1027	1.9	1.4049	2.4 0.09925 1.6 0.77 630	11	15	1610	29	39
	a56	57029 1704 330.0 0.12	7.16		0.0517	1.7	0.3760	5.5 0.05278 5.2 0.31 325	5	15	319	118	102
	a57	25528	679	230.7 0.46	0.75		0.0883	1.6	0.7585	2.8 0.06233 2.3 0.57 545	8	12	685	49	80
	a58	27240 1861 304.2 0.12	0.16		0.0510	1.5	0.3725	1.6 0.05294 0.7 0.90 321	5	4	326	16	98
	a59	20652 1222 243.3 0.89	1.72		0.0492	1.5	0.3587	3.2 0.05285 2.8 0.46 310	4	9	322	64	96
	a60	83678 1992 571.8 0.41	6.28		0.0709	1.8	0.5734	5.4 0.05869 5.1 0.33 441	8	20	556	112	79
	a61	32902 1707 359.0 0.20	0.24		0.0632	1.7	0.4968	2.1 0.05699 1.2 0.82 395	6	7	491	26	80
	a62	19741 1455 209.4 0.15	0.32		0.0438	1.8	0.3207	2.2 0.05310 1.2 0.82 276	5	5	333	28	83
	a63	38800 3142 512.5 0.60	0.98		0.0427	1.6	0.3053	2.5 0.05185 1.9 0.63 270	4	6	279	44	97
	a65	12794	828	153.0 0.57	0.46		0.0500	1.6	0.3663	2.7 0.05313 2.2 0.58 315	5	7	334	49	94
	a66	23889 1470 271.4 0.65	0.88		0.0483	1.6	0.3533	2.9 0.05309 2.4 0.56 304	5	8	332	55	91
	a72	27846 1580 294.8 0.52	1.07		0.0510	1.5	0.3736	2.6 0.05311 2.1 0.57 321	5	7	334	48	96
	a73	126298 2014 650.6 0.24	2.27		0.0907	2.2	1.1530	3.1 0.09222 2.1 0.72 560	12	17	1472	40	38
	a74	22408 1557 247.0 0.05	0.03		0.0516	1.6	0.3755	1.8 0.05280 0.8 0.89 324	5	5	320	18	101
	a75	15261	728	141.2 0.40	3.58		0.0520	1.8	0.3796	4.5 0.05290 4.1 0.39 327	6	13	325	94	101
	a76	18896 1275 228.0 0.49	0.34		0.0500	1.5	0.3657	2.0 0.05305 1.3 0.76 314	5	5	331	29	95
	a77	24980 1284 225.3 0.28	3.04		0.0491	1.9	0.3576	4.1 0.05287 3.7 0.45 309	6	11	323	83	96
	Vaugnerites
	533-1
	Session #1 (April 9	th , 2014)
	a107	57895 1559 103.7 0.55 12.48 0.0488	2.2	0.3501	9.0 0.05203 8.7 0.25 307	7	24	287	199	107
	a108	14077 1195	61.2	0.48	b.d.		0.0484	1.8	0.3511	2.0 0.05260 1.0 0.88 305	5	5	312	22	98
	a109	29037 2440 128.0 0.54	b.d.		0.0490	1.8	0.3575	1.9 0.05291 0.8 0.92 308	5	5	325	18	95
	a110	17155 1386	69.7	0.40	0.26		0.0484	1.7	0.3521	2.1 0.05282 1.1 0.84 304	5	5	321	25	95
	a111	30618 1880 103.0 0.79	3.37		0.0488	1.9	0.3506	4.7 0.05214 4.3 0.41 307	6	13	291	98	105

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)			238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a112	24922 1782	96.2	0.73	1.38		0.0470	1.7	0.3442	3.4 0.05313 3.0 0.50 296	5	9	334	68	89
	a113	22275 1739	90.9	0.52	0.79		0.0486	1.7	0.3478	2.7 0.05193 2.0 0.64 306	5	7	282	47	108
	a114	16182 1392	75.7	0.73	b.d.		0.0477	1.7	0.3454	2.3 0.05256 1.4 0.77 300	5	6	310	33	97
	a115	16363 1320	62.6	0.23	0.28		0.0480	1.7	0.3509	2.2 0.05303 1.4 0.77 302	5	6	330	32	92
	a116	38754 3302 166.9 0.38	b.d.		0.0494	1.8	0.3587	1.9 0.05266 0.6 0.94 311	5	5	314	14	99
	a117	12164 1071	49.8	0.21	b.d.		0.0475	1.8	0.3457	2.0 0.05276 1.0 0.86 299	5	5	319	24	94
	a118	27160 2002 104.1 0.45	0.65		0.0495	1.8	0.3569	2.4 0.05231 1.6 0.74 311	5	7	299	38	104
	a119	30644 2656 138.7 0.48	b.d.		0.0491	1.7	0.3582	1.9 0.05289 0.8 0.90 309	5	5	324	19	95
	a120	28415 2123 113.6 0.53	1.05		0.0490	1.8	0.3539	2.8 0.05238 2.2 0.63 308	5	7	302	50	102
	a121	32750 2474 130.2 0.44	0.98		0.0494	1.9	0.3597	2.8 0.05284 2.1 0.66 311	6	8	322	48	96
	a122	29394 2628 138.8 0.59	0.28		0.0473	1.8	0.3405	2.2 0.05226 1.3 0.82 298	5	6	297	29	100
	533-2
	Session #1 (April 9 th , 2014)
	a345	7401	707	38.4	0.86	0.04		0.0463	1.8	0.3368	2.2 0.05272 1.3 0.82 292	5	6	317	29	92
	a346	5693	534	31.3	0.99	b.d.		0.0490	1.8	0.3552	2.2 0.05261 1.2 0.84 308	5	6	312	27	99
	a347	10212	491	25.7	0.56	0.72		0.0457	2.0	0.3347	3.2 0.05306 2.4 0.63 288	6	8	331	55	87
	a348	13589 1232	63.2	0.52	0.25		0.0481	1.7	0.3489	2.2 0.05256 1.3 0.81 303	5	6	310	29	98
	a349	3555	321	17.4	0.69	0.03		0.0488	1.8	0.3537	2.6 0.05256 1.8 0.71 307	5	7	310	41	99
	a350	2750	260	13.3	0.41	b.d.		0.0494	1.9	0.3562	2.9 0.05225 2.2 0.66 311	6	8	296	50	105
	a351	3854	374	20.3	0.83	b.d.		0.0464	1.9	0.3358	2.4 0.05251 1.5 0.80 292	5	6	308	33	95
	a352	11578	976	53.9	0.69	0.67		0.0491	1.8	0.3574	3.3 0.05276 2.7 0.56 309	6	9	319	62	97
	a353	10307	989	55.4	0.93	b.d.		0.0475	1.8	0.3428	2.0 0.05231 0.9 0.89 299	5	5	299	21	100
	a354	5745	534	30.5	0.94	b.d.		0.0480	1.8	0.3517	2.1 0.05316 1.2 0.82 302	5	6	335	27	90
	a355	2821	264	14.4	0.79	0.03		0.0489	1.9	0.3549	2.6 0.05262 1.7 0.75 308	6	7	312	39	99
	a356	4679	446	22.3	0.42	0.28		0.0477	1.8	0.3476	2.4 0.05281 1.6 0.75 301	5	6	321	37	94
	a357	1738	165	8.4	0.48	b.d.		0.0491	2.1	0.3521	3.3 0.05198 2.5 0.65 309	6	9	284	58	109
	a358	7302	661	38.3	1.06	0.32		0.0472	1.7	0.3450	2.1 0.05295 1.3 0.79 298	5	6	327	30	91
	a359	3229	306	17.0	0.83	b.d.		0.0482	1.8	0.3490	2.4 0.05255 1.5 0.75 303	5	6	309	35	98
	a360	7018	556	32.2	0.96	0.72		0.0484	1.8	0.3562	4.4 0.05337 4.0 0.40 305	5	12	344	91	88
	a361	10410	917	53.8	0.97	0.06		0.0487	1.7	0.3541	2.3 0.05274 1.5 0.76 307	5	6	317	33	97
	a362	8926	825	48.7	1.04	b.d.		0.0486	1.7	0.3529	2.0 0.05262 1.0 0.86 306	5	5	312	23	98
	a363	5634	534	30.5	0.90	b.d.		0.0487	1.8	0.3505	2.4 0.05220 1.5 0.78 307	5	6	294	34	104
	a364	5709	478	27.0	0.86	0.19		0.0473	1.8	0.3523	3.0 0.05401 2.4 0.61 298	5	8	371	54	80
	a365	6966	646	34.4	0.58	b.d.		0.0491	1.8	0.3545	2.2 0.05239 1.3 0.81 309	5	6	303	30	102
	a366	2327	218	10.8	0.29	0.19		0.0494	1.9	0.3583	2.5 0.05265 1.7 0.75 311	6	7	314	38	99
	a367	4251	410	22.4	0.74	0.20		0.0491	1.9	0.3574	2.6 0.05283 1.8 0.72 309	6	7	321	41	96
	a368	1802	169	8.7	0.58	1.56		0.0459	2.3	0.3329	3.3 0.05256 2.3 0.71 290	7	8	310	53	93
	a369	2696	247	13.1	0.61	b.d.		0.0494	1.8	0.3582	2.5 0.05257 1.7 0.72 311	5	7	310	39	100
	a370	3523	334	18.1	0.80	1.30		0.0475	1.9	0.3486	2.6 0.05327 1.7 0.76 299	6	7	340	37	88
	a371	9369	879	52.6	1.16	0.61		0.0478	1.8	0.3513	2.0 0.05331 1.0 0.86 301	5	5	342	23	88
	LR-31
	Session #1 (April 9	th , 2014)
	a318	7363	698	41.7	1.18	b.d.		0.0475	1.8	0.3436	2.1 0.05248 1.1 0.85 299	5	5	306	25	98
	a319	9823	992	55.6	0.96	b.d.		0.0472	1.8	0.3445	2.1 0.05289 1.1 0.84 298	5	6	324	26	92
	a321	4544	452	25.6	0.98	b.d.		0.0471	1.8	0.3402	2.3 0.05234 1.3 0.81 297	5	6	300	31	99
	a322	3256	324	15.7	0.37	b.d.		0.0475	2.0	0.3401	2.8 0.05192 2.0 0.71 299	6	7	282	45	106
	a323	4645	448	26.1	1.05	b.d.		0.0479	1.8	0.3462	2.2 0.05243 1.3 0.81 302	5	6	304	29	99
	a324	3220	314	18.6	0.93	b.d.		0.0481	2.3	0.3473	2.8 0.05240 1.6 0.82 303	7	7	303	36	100
	a325	4429	423	24.5	0.83	0.63		0.0475	1.8	0.3436	3.6 0.05242 3.1 0.51 299	5	9	304	71	99
	a326	4695	457	25.3	0.95	0.09		0.0475	1.9	0.3480	2.5 0.05311 1.7 0.75 299	6	7	334	38	90
	a327	5569	539	30.9	1.08	0.50		0.0466	1.9	0.3390	2.5 0.05282 1.6 0.75 293	5	6	321	37	91
	a333	1978	210	10.1	0.45	b.d.		0.0478	2.5	0.3427	3.7 0.05204 2.7 0.68 301	7	10	287	62	105
	a334	2259	211	11.4	0.87	b.d.		0.0450	2.2	0.3262	4.0 0.05262 3.3 0.56 283	6	10	312	75	91
	a335	5230	499	29.2	1.09	0.53		0.0474	1.8	0.3418	2.9 0.05228 2.3 0.61 299	5	8	298	53	100
	a336	5820	568	33.2	1.11	b.d.		0.0473	1.7	0.3426	2.3 0.05254 1.5 0.75 298	5	6	309	35	96
	a337	4036	390	21.6	0.93	0.03		0.0470	1.8	0.3440	2.6 0.05308 1.9 0.70 296	5	7	332	42	89
	a338	5340	505	29.1	1.17	b.d.		0.0462	1.8	0.3338	3.4 0.05239 2.9 0.52 291	5	9	303	66	96
	a340	4412	427	24.4	1.02	b.d.		0.0474	1.7	0.3419	2.3 0.05232 1.5 0.76 299	5	6	299	34	100
	a341	5052	453	25.4	0.88	0.18		0.0474	1.9	0.3424	4.2 0.05236 3.8 0.44 299	5	11	301	87	99
	a342	4243	384	23.0	1.07	0.19		0.0479	1.8	0.3483	3.2 0.05274 2.6 0.57 302	5	8	318	60	95
	a343	3853	378	30.9	3.26	b.d.		0.0455	2.1	0.3399	4.6 0.05421 4.1 0.46 287	6	12	380	92	75
	a344	3384	329	19.0	1.03	b.d.		0.0480	1.9	0.3502	2.7 0.05290 2.0 0.69 302	5	7	325	45	93
	LR-32
	Session #1 (April 9	th , 2014)
	a207	6189	587	33.3	1.19	b.d.		0.0370	2.0	0.2690	2.4 0.05274 1.3 0.83 234	5	5	318	31	74

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)			238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a208	6868	628	35.7	0.84	b.d.		0.0462	1.7	0.3332	2.2 0.05235 1.4 0.77 291	5	6	301	32	97
	a209	8516	778	54.5	1.81	0.32		0.0481	1.8	0.3473	3.0 0.05239 2.4 0.61 303	5	8	303	55	100
	a210	7624	730	32.9	0.14	b.d.		0.0481	1.8	0.3506	2.1 0.05285 1.1 0.86 303	5	6	322	25	94
	a211	3108	299	17.0	0.97	b.d.		0.0482	1.9	0.3468	2.7 0.05212 1.9 0.71 304	6	7	291	44	104
	a212	5063	492	28.4	1.03	0.22		0.0473	1.9	0.3413	3.8 0.05234 3.3 0.49 298	5	10	300	76	99
	a213	7330	686	41.8	1.15	0.39		0.0482	1.8	0.3506	2.3 0.05281 1.5 0.76 303	5	6	321	34	95
	a214	8596	820	50.6	1.26	b.d.		0.0481	1.7	0.3460	2.2 0.05217 1.4 0.79 303	5	6	293	31	103
	a215	6604	634	34.6	0.77	b.d.		0.0480	1.8	0.3492	2.2 0.05271 1.3 0.82 302	5	6	317	29	96
	a216	2999	289	16.1	0.86	b.d.		0.0477	1.8	0.3451	2.5 0.05244 1.7 0.73 301	5	6	305	38	99
	a217	8849	858	53.4	1.30	b.d.		0.0481	1.7	0.3483	2.4 0.05254 1.6 0.73 303	5	6	309	37	98
	a218	2600	240	13.8	0.97	0.04		0.0478	1.8	0.3454	2.5 0.05243 1.7 0.74 301	5	7	304	39	99
	a219	6605	614	36.1	1.10	0.71		0.0470	1.8	0.3453	2.5 0.05327 1.7 0.72 296	5	6	340	39	87
	a220	4126	400	23.5	1.11	b.d.		0.0477	1.9	0.3440	2.4 0.05233 1.6 0.76 300	5	6	300	36	100
	a221	8711	826	40.4	0.41	0.02		0.0477	1.7	0.3448	2.1 0.05244 1.3 0.80 300	5	6	305	29	99
	a222	11994 1115	57.8	0.58	b.d.		0.0481	1.7	0.3463	2.0 0.05221 1.0 0.88 303	5	5	295	22	103
	a224	17123 1950	56.0	0.89	2.02		0.0258	1.9	0.1830	4.2 0.05148 3.8 0.45 164	3	7	262	87	63
	a225	3398	318	18.3	0.98	b.d.		0.0477	1.9	0.3493	2.6 0.05311 1.7 0.74 300	6	7	333	39	90
	a226	2595	243	13.4	0.78	0.13		0.0479	2.1	0.3483	3.0 0.05274 2.1 0.71 302	6	8	317	47	95
	PRC-53
	Session #1 (April 9	th , 2014)
	a78	5675	443	25.6	0.77	0.76		0.0511	2.4	0.3747	3.3 0.05317 2.2 0.75 321	8	9	336	49	96
	a79	11609	950	39.0	0.39	1.13		0.0394	1.8	0.2819	3.9 0.05194 3.4 0.46 249	4	9	283	78	88
	a80	3856	311	17.3	0.61	b.d.		0.0509	1.8	0.3715	2.3 0.05297 1.4 0.79 320	6	6	328	32	98
	a81	5966	477	26.9	0.69	0.14		0.0506	2.0	0.3663	3.1 0.05249 2.4 0.63 318	6	8	307	55	104
	a82	4533	353	18.7	0.63	0.01		0.0485	1.9	0.3544	2.4 0.05297 1.5 0.79 305	6	6	327	34	93
	a84	8829	624	30.5	0.63	1.68		0.0435	1.9	0.3271	5.8 0.05454 5.5 0.33 274	5	15	394	122	70
	a85	4791	352	21.1	0.93	0.09		0.0500	1.9	0.3641	2.7 0.05277 1.9 0.72 315	6	7	319	42	99
	a86	3599	301	15.8	0.58	0.14		0.0475	2.0	0.3568	2.6 0.05446 1.7 0.77 299	6	7	390	37	77
	a87	6051	547	28.0	0.97	b.d.		0.0428	1.9	0.3155	2.5 0.05347 1.6 0.76 270	5	6	349	36	77
	a88	3543	303	16.1	0.60	0.01		0.0490	1.8	0.3566	2.3 0.05275 1.5 0.78 309	5	6	318	33	97
	a89	4503	376	19.0	0.75	0.34		0.0441	1.8	0.3207	2.7 0.05272 2.1 0.64 278	5	7	317	47	88
	a90	7515	654	30.7	0.18	0.61		0.0508	2.0	0.3737	2.5 0.05334 1.6 0.78 319	6	7	343	36	93
	a91	6556	518	28.8	0.63	0.49		0.0487	1.9	0.3507	4.6 0.05225 4.1 0.43 306	6	12	296	94	103
	a92	3173	268	15.5	0.73	b.d.		0.0507	2.0	0.3668	2.6 0.05248 1.6 0.77 319	6	7	306	37	104
	a93	3535	296	16.2	0.52	b.d.		0.0509	1.8	0.3760	3.5 0.05356 2.9 0.53 320	6	10	353	66	91
	a94	7462	953	42.6	0.52	0.85		0.0440	2.1	0.3205	4.4 0.05286 3.9 0.47 277	6	11	323	88	86
	a96	4928	402	23.7	0.80	b.d.		0.0513	1.8	0.3739	5.3 0.05283 5.0 0.35 323	6	15	322	112	100
	a97	2851	226	12.1	0.47	0.04		0.0504	1.9	0.3679	2.4 0.05291 1.5 0.79 317	6	7	325	33	98
	a98	6141	489	28.5	0.82	b.d.		0.0505	1.8	0.3674	2.1 0.05272 1.1 0.85 318	5	6	317	25	100
	a99	5441	476	27.6	0.68	0.08		0.0495	2.3	0.3696	2.6 0.05416 1.3 0.87 311	7	7	378	29	82
	a100	4783	397	23.2	0.82	0.45		0.0504	1.8	0.3688	2.6 0.05308 1.9 0.70 317	6	7	332	43	95
	a101	5287	458	26.4	0.87	0.62		0.0487	1.8	0.3567	2.6 0.05313 1.8 0.71 307	5	7	334	41	92
	PRC-54
	Session #1 (April 9	th , 2014)
	a153	4884	411	22.6	0.57	b.d.		0.0507	1.8	0.3723	2.8 0.05328 2.1 0.66 319	6	8	341	47	94
	a154	3328	274	15.1	0.58	1.67		0.0483	2.0	0.3574	4.5 0.05367 4.1 0.45 304	6	12	357	92	85
	a157	3596	315	17.7	0.52	0.54		0.0512	2.1	0.3710	2.9 0.05256 2.0 0.72 322	6	8	310	45	104
	a158	4619	397	22.9	0.75	0.60		0.0507	1.9	0.3708	3.0 0.05304 2.4 0.62 319	6	8	330	54	96
	a159	3791	304	18.0	0.83	0.06		0.0511	1.8	0.3724	2.4 0.05281 1.6 0.75 321	6	7	321	36	100
	a162	5057	444	21.1	0.17	b.d.		0.0489	1.9	0.3613	2.5 0.05363 1.6 0.76 307	6	7	356	37	86
	a164	5449	467	27.3	0.82	0.32		0.0508	1.8	0.3739	2.3 0.05335 1.3 0.81 320	6	6	344	30	93
	a165	7208	598	35.4	0.79	b.d.		0.0511	1.9	0.3723	3.3 0.05282 2.8 0.56 321	6	9	321	63	100
	a166	4973	398	21.3	0.29	0.85		0.0510	2.3	0.3830	4.0 0.05442 3.2 0.58 321	7	11	389	72	83
	a167	4541	365	19.7	0.42	0.40		0.0480	2.2	0.3373	6.5 0.05100 6.2 0.33 302	6	17	241	142	125
	a168	2897	278	16.5	0.62	b.d.		0.0510	2.0	0.3734	3.9 0.05311 3.3 0.51 321	6	11	333	76	96
	a169	3747	298	17.0	0.55	0.94		0.0511	1.9	0.3691	3.4 0.05235 2.8 0.57 321	6	9	301	64	107
	a170	8110	469	28.9	0.86	1.21		0.0420	3.0	0.3150	6.7 0.05441 6.0 0.45 265	8	17	388	135	68
	a171	4704	380	22.4	0.84	b.d.		0.0494	1.7	0.3649	2.3 0.05354 1.4 0.77 311	5	6	352	32	88
	a173	6004	465	27.4	0.81	0.15		0.0509	1.9	0.3706	3.5 0.05286 3.0 0.54 320	6	10	323	67	99
	a174	6642	425	24.9	0.72	1.55		0.0508	1.9	0.3695	4.7 0.05280 4.3 0.42 319	6	13	320	97	100
	a175	3776	331	17.9	0.66	0.80		0.0484	1.9	0.3559	2.9 0.05329 2.2 0.67 305	6	8	341	49	89
	SC-13-02A
	Session #1 (April 9	th , 2014)
	a123	16281 1162	55.4	0.11	1.15		0.0497	1.8	0.3556	2.9 0.05193 2.2 0.63 312	5	8	283	51	111
	a124	10583	580	33.9	0.40	1.52		0.0481	2.9	0.3438	4.7 0.05185 3.6 0.63 303	9	12	279	83	109

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)			238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a125	4151	348	16.9	0.29	0.83		0.0494	2.0	0.3579	4.2 0.05253 3.8 0.46 311	6	11	309	86	101
	a126	37697 2917 138.1 0.08	0.64		0.0499	1.9	0.3624	2.2 0.05262 1.2 0.84 314	6	6	312	28	101
	a127	28741 2367 112.3 0.15	b.d.		0.0496	1.8	0.3619	2.1 0.05288 1.2 0.84 312	5	6	324	26	96
	a128	23592 1639	80.6	0.23	1.06		0.0476	1.8	0.3408	2.8 0.05188 2.2 0.63 300	5	7	280	50	107
	a129	3761	293	16.7	0.28	b.d.		0.0504	1.9	0.3642	2.4 0.05245 1.4 0.80 317	6	6	305	32	104
	SC-13-05
	Session #1 (April 9	th , 2014)
	a130	22671 1914	90.0	0.10	0.06		0.0491	1.7	0.3542	1.9 0.05231 0.7 0.93 309	5	5	299	16	103
	a131	18683 1681	76.2	0.72	b.d.		0.0494	1.7	0.3584	1.9 0.05267 0.7 0.93 311	5	5	314	16	99
	a132	28199 2219 109.9 0.45	0.87		0.0491	1.7	0.3573	2.5 0.05281 1.8 0.69 309	5	7	321	41	96
	a133	22021 1874	91.7	0.15	0.21		0.0495	1.7	0.3588	2.0 0.05257 1.0 0.87 311	5	5	310	22	100
	a134	26155 2259 106.7 0.19	0.11		0.0485	1.7	0.3541	2.1 0.05297 1.1 0.84 305	5	6	327	25	93
	a135	22772 1959 101.0 0.44	0.15		0.0498	1.8	0.3598	2.2 0.05242 1.2 0.84 313	6	6	304	27	103
	a136	21383 1842	82.6	0.23	b.d.		0.0488	1.7	0.3564	2.2 0.05297 1.3 0.78 307	5	6	327	30	94
	a137	27083 2416 119.1 0.34	0.05		0.0485	1.7	0.3523	1.9 0.05265 0.8 0.91 305	5	5	314	18	97
	a138	47211 3167 165.9 0.39	4.32		0.0458	2.2	0.3282	5.3 0.05198 4.8 0.41 289	6	13	285	111	101
	a139	31903 2622 127.3 0.27	0.78		0.0482	1.7	0.3516	2.4 0.05293 1.7 0.72 303	5	6	326	38	93
	a140	19685 1685	78.3	0.08	b.d.		0.0498	1.7	0.3623	1.9 0.05274 0.8 0.91 313	5	5	318	18	99
	a141	8310	752	45.7	1.19	b.d.		0.0480	1.8	0.3483	2.1 0.05258 1.2 0.83 303	5	6	311	27	97
	a142	3600	356	18.9	1.04	b.d.		0.0442	1.8	0.3265	2.4 0.05359 1.5 0.77 279	5	6	354	34	79
	a143	22951 1928	89.5	0.14	b.d.		0.0483	1.7	0.3533	1.8 0.05308 0.7 0.92 304	5	5	332	16	92
	a144	18048 1610	73.4	0.42	b.d.		0.0496	1.7	0.3583	2.0 0.05235 1.0 0.87 312	5	5	301	22	104
	a145	34254 2651 135.1 0.45	1.22		0.0480	1.7	0.3478	2.6 0.05256 2.0 0.65 302	5	7	310	46	98
	a151	26236 2054	97.4	0.22	1.22		0.0474	1.8	0.3450	2.9 0.05285 2.2 0.63 298	5	8	322	51	93
	a152	42315 2190 113.4 0.28	4.27		0.0494	1.8	0.3655	5.0 0.05369 4.7 0.36 311	6	14	358	105	87
	SC-13-09
	Session #1 (April 9 th , 2014)
	a269	11009	517	30.4	0.58	5.03		0.0491	2.1	0.3618	6.9 0.05340 6.6 0.31 309	6	19	346	149	89
	a270	8640	800	44.0	0.75	b.d.		0.0484	1.7	0.3500	2.0 0.05245 1.1 0.86 305	5	5	305	24	100
	a271	25541 2206 139.3 0.92	b.d.		0.0535	1.8	0.3937	1.9 0.05337 0.8 0.91 336	6	6	344	18	98
	a272	20722 1925 110.6 0.89	0.51		0.0489	1.8	0.3577	2.5 0.05302 1.7 0.72 308	5	7	329	39	93
	a273	13647	963	54.7	0.75	1.84		0.0497	1.8	0.3573	3.8 0.05215 3.3 0.47 313	5	10	292	76	107
	a274	13872 1252	63.8	0.37	b.d.		0.0500	1.8	0.3655	2.1 0.05299 0.9 0.90 315	6	6	328	21	96
	a275	6187	594	32.2	0.73	b.d.		0.0491	1.7	0.3535	2.1 0.05221 1.2 0.81 309	5	6	295	28	105
	a276	19657 1832 104.8 0.84	b.d.		0.0494	1.7	0.3599	1.9 0.05284 0.9 0.89 311	5	5	322	19	97
	a277	5741	473	27.3	0.62	1.06		0.0500	1.9	0.3579	4.2 0.05194 3.7 0.46 314	6	11	283	85	111
	a278	18506 1014	58.3	0.70	4.83		0.0467	1.8	0.3400	6.4 0.05284 6.1 0.29 294	5	17	322	138	91
	a279	8961	670	37.2	0.61	1.76		0.0493	1.8	0.3517	4.0 0.05177 3.6 0.45 310	5	11	275	83	113
	a280	23926 1965 110.2 0.80	1.24		0.0475	1.8	0.3427	3.0 0.05228 2.4 0.59 299	5	8	298	56	101
	a281	12209 1077	56.7	0.51	0.35		0.0494	1.7	0.3606	2.3 0.05291 1.5 0.75 311	5	6	325	34	96
	a282	30891 1245	69.3	0.20	7.69		0.0480	1.9	0.3466	7.8 0.05241 7.5 0.25 302	6	21	303	172	99
	a288	27883 1287	70.5	0.28	5.73		0.0481	1.8	0.3507	6.1 0.05290 5.9 0.30 303	5	16	325	133	93
	a289	14414 1113	61.4	0.73	1.32		0.0473	1.8	0.3379	3.5 0.05183 3.0 0.51 298	5	9	278	69	107
	a290	18639 1734	95.5	0.72	b.d.		0.0489	1.7	0.3553	1.9 0.05267 0.9 0.89 308	5	5	315	19	98
	a291	12801 1201	69.5	0.95	b.d.		0.0485	1.7	0.3523	2.0 0.05273 1.0 0.87 305	5	5	317	22	96
	a292	13709 1197	66.2	0.74	0.39		0.0487	1.7	0.3491	2.4 0.05199 1.6 0.74 307	5	6	285	36	108
	a293	29892 2138 121.6 0.72	2.01		0.0495	1.7	0.3592	3.5 0.05258 3.1 0.49 312	5	9	311	70	100
	a294	14567 1366	75.9	0.74	0.02		0.0487	1.7	0.3561	2.0 0.05301 0.9 0.88 307	5	5	329	21	93
	a295	16905 1557	86.9	0.74	b.d.		0.0497	1.7	0.3634	2.0 0.05301 1.0 0.88 313	5	5	329	22	95
	a296	23928 2103 133.4 1.25	0.81		0.0494	1.7	0.3612	2.7 0.05307 2.0 0.65 311	5	7	332	46	94
	a297	38073 3563 189.2 0.58	b.d.		0.0495	1.7	0.3605	1.8 0.05277 0.6 0.94 312	5	5	319	14	98
	a298	20911 1861 109.8 0.93	0.58		0.0488	1.7	0.3566	2.5 0.05304 1.9 0.68 307	5	7	331	42	93
	a299	26664 2440 147.8 1.08	0.10		0.0493	1.7	0.3609	2.1 0.05310 1.2 0.82 310	5	6	333	27	93
	a300	18573 1551	90.9	0.94	0.55		0.0483	1.7	0.3486	2.3 0.05231 1.6 0.73 304	5	6	299	36	102
	SC-13-14
	Session #1 (April 9	th , 2014)
	a15	29463 1321	63.2	0.96	5.61		0.0369	2.4	0.2711	6.3 0.05330 5.8 0.39 234	6	14	341	132	68
	a16	14880	727	49.2	0.62	1.89		0.0538	1.8	0.3940	4.6 0.05316 4.2 0.40 338	6	13	335	96	101
	a17	10208	641	33.3	0.58	1.25		0.0462	1.9	0.3386	3.5 0.05313 3.0 0.53 291	5	9	334	67	87
	a18	21318	884	50.5	0.43	5.92		0.0499	2.0	0.3642	6.5 0.05295 6.2 0.31 314	6	18	327	141	96
	a19	21296	774	48.4	0.92	6.83		0.0478	2.1	0.3546	8.1 0.05377 7.8 0.26 301	6	22	377	176	80
	a20	6659	415	22.9	0.25	0.57		0.0531	1.8	0.3918	4.1 0.05350 3.7 0.45 334	6	12	350	83	95
	a21	40077 2456 137.2 0.43	1.47		0.0529	1.8	0.3878	3.1 0.05316 2.5 0.59 332	6	9	336	57	99
	a22	20803 1167	70.4	0.13	0.21		0.0608	2.6	0.4556	3.0 0.05430 1.6 0.85 381	10	10	383	37	99
	a23	11046	571	29.5	0.66	2.30		0.0420	1.9	0.3046	5.3 0.05257 5.0 0.35 265	5	13	310	114	85

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

	Laurent
		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)			238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a24	18836	858	46.3	0.72	5.58		0.0434	2.1	0.3182	6.8 0.05320 6.5 0.31 274	6	17	337	147	81
	a25	16733 1178	61.7	0.17	0.24		0.0537	1.7	0.3968	2.2 0.05364 1.4 0.79 337	6	6	356	30	95
	a26	12879	652	40.8	0.73	2.32		0.0532	1.9	0.3880	3.9 0.05292 3.4 0.48 334	6	11	325	78	103
	a27	27562	984	66.4	0.80	7.43		0.0534	2.2	0.3942	6.6 0.05358 6.2 0.34 335	7	19	353	140	95
	a28	8975	410	33.4	0.38	0.01		0.0786	1.8	0.6178	2.0 0.05698 1.0 0.86 488	8	8	491	23	99
	a29	10672	661	35.2	0.18	0.18		0.0536	2.0	0.3931	3.1 0.05319 2.4 0.63 337	6	9	337	55	100
	a30	4659	310	15.9	0.12	0.51		0.0535	1.9	0.3926	2.5 0.05317 1.5 0.78 336	6	7	336	35	100
	a31	20997 1488	80.7	0.24	0.10		0.0537	1.8	0.3956	2.1 0.05342 1.1 0.86 337	6	6	347	24	97
	a32	16355	974	62.0	0.23	0.03		0.0635	2.0	0.4793	2.5 0.05472 1.4 0.81 397	8	8	401	32	99
	a38	52115	533	47.5	0.27 32.68 0.0418	4.1	0.4556 11.6 0.07900 10.9 0.35 264	11	38	1172 216	23
	a39	61518	687	60.6	0.95 29.92 0.0454	4.2	0.3576 13.1 0.05715 12.4 0.32 286	12	36	497	273	58
	a40	10117	617	32.0	0.34	1.02		0.0487	1.8	0.3641	4.1 0.05418 3.7 0.44 307	5	11	379	83	81
	a41	8258	486	26.1	0.46	2.10		0.0522	1.8	0.4023	7.1 0.05589 6.8 0.26 328	6	21	448	152	73
	SC-13-19
	Session #1 (April 9	th , 2014)
	a176	5309	453	24.5	0.67	1.36		0.0479	1.9	0.3579	3.1 0.05415 2.5 0.60 302	6	8	377	56	80
	a177	35612 2634 171.8 0.99	0.59		0.0533	1.7	0.3947	2.2 0.05369 1.4 0.78 335	6	6	358	32	93
	a178	37941 2126 141.8 0.95	2.83		0.0535	1.8	0.3887	3.9 0.05272 3.4 0.46 336	6	11	317	78	106
	a179	31432 2599 168.4 1.02	b.d.		0.0533	1.7	0.3906	1.9 0.05313 0.8 0.91 335	6	5	335	18	100
	a180	16104 1161	67.4	0.68	1.02		0.0509	1.8	0.3688	3.0 0.05255 2.5 0.58 320	5	8	310	56	103
	a181	19954 1602	97.1	0.74	b.d.		0.0533	1.8	0.3912	2.2 0.05320 1.3 0.80 335	6	6	337	30	99
	a182	30264 2291 141.0 0.87	0.66		0.0516	1.7	0.3803	2.3 0.05342 1.5 0.76 325	5	6	347	34	94
	a183	11566	943	53.9	0.61	b.d.		0.0520	1.7	0.3815	2.1 0.05322 1.1 0.84 327	6	6	338	26	97
	a184	31644 2455 145.3 0.75	0.28		0.0525	1.8	0.3888	2.4 0.05374 1.7 0.73 330	6	7	360	37	91
	a185	27725 2229 124.0 0.65	b.d.		0.0487	1.9	0.3603	2.1 0.05365 1.1 0.87 307	6	6	356	24	86
	a186	16884 1314	80.6	0.69	0.42		0.0535	1.9	0.3925	2.8 0.05325 2.1 0.68 336	6	8	339	47	99
	a187	23450 1955 121.2 0.83	b.d.		0.0532	1.7	0.3878	1.8 0.05292 0.7 0.93 334	6	5	325	15	103
	a188	25727 2143 142.7 1.14	0.14		0.0532	1.7	0.3914	1.9 0.05334 0.7 0.92 334	6	5	343	16	97
	a189	16040 1100	63.5	0.75	0.69		0.0496	1.8	0.3647	2.8 0.05336 2.1 0.64 312	5	8	344	48	91
	a190	20338 1556	95.8	0.77	0.24		0.0533	1.7	0.3903	2.0 0.05307 1.0 0.85 335	6	6	332	24	101
	a191	9495	806	40.2	0.16	b.d.		0.0514	1.7	0.3793	2.3 0.05352 1.5 0.76 323	5	6	351	33	92
	a192	16904 1431	85.7	0.74	b.d.		0.0527	1.7	0.3828	1.9 0.05273 0.8 0.90 331	6	5	317	19	104
	a193	34950 2920 197.7 1.21	b.d.		0.0532	1.7	0.3901	1.8 0.05316 0.6 0.95 334	6	5	336	13	100
	a199	23191 1840 104.8 0.55	0.30		0.0531	1.7	0.3901	2.7 0.05326 2.1 0.63 334	6	8	340	48	98
	a200	35658 1971 129.8 0.81	3.24		0.0537	1.8	0.3883	4.5 0.05248 4.1 0.40 337	6	13	306	94	110
	a201	17406 1401	84.6	0.69	0.08		0.0536	1.7	0.3937	2.0 0.05326 0.9 0.89 337	6	6	340	20	99
	a202	20551 1764 105.5 0.76	0.08		0.0522	1.7	0.3832	2.0 0.05323 0.9 0.88 328	5	6	339	21	97
	a203	24667 1575	92.0	0.59	2.21		0.0513	1.7	0.3756	3.5 0.05312 3.0 0.49 322	5	10	334	69	96
	a204	25955 2104 130.1 0.86	0.08		0.0525	1.7	0.3893	2.1 0.05383 1.2 0.82 330	5	6	364	26	91
	a205	50789 4586 257.7 0.53	0.23		0.0525	1.7	0.3829	1.9 0.05292 0.7 0.92 330	6	5	326	16	101
	a206	22131 1707	99.5	0.57	0.18		0.0534	1.7	0.3942	2.4 0.05351 1.6 0.72 336	6	7	350	37	96
	SGC-12-13
	Session #1 (April 9	th , 2014)
	a06	2173	157	8.5	0.61	b.d.		0.0486	2.0	0.3510	3.1 0.05241 2.4 0.63 306	6	8	303	55	101
	a07	7516	433	27.6	0.90	1.46		0.0495	2.2	0.3611	5.7 0.05287 5.2 0.38 312	7	15	323	119	96
	a08	4627	300	14.1	0.49	2.35		0.0411	2.2	0.3047	6.9 0.05374 6.6 0.32 260	6	17	360	148	72
	a09	7449	615	34.0	0.73	0.28		0.0486	1.8	0.3506	3.5 0.05233 3.1 0.51 306	5	9	300	70	102
	a10	6330	704	36.4	0.67	0.85		0.0462	2.6	0.3331	6.2 0.05233 5.6 0.43 291	8	16	300	128	97
	a11	3988	265	15.3	0.62	0.63		0.0487	2.1	0.3540	6.1 0.05268 5.7 0.34 307	6	16	315	131	97
	a12	16544 1078	62.9	0.66	0.83		0.0513	1.7	0.3744	2.9 0.05296 2.3 0.61 322	6	8	327	52	99
	a13	21730 1540	79.7	0.47	0.76		0.0484	1.8	0.3501	2.9 0.05245 2.2 0.63 305	5	8	305	51	100
	a14	4422	328	19.8	0.83	b.d.		0.0485	2.0	0.3561	2.6 0.05326 1.6 0.77 305	6	7	340	37	90
	SGC-12-26
	Session #1 (April 9 th , 2014)
	a372	7438	728	43.8	1.17	b.d.		0.0480	1.7	0.3497	2.0 0.05280 1.1 0.84 302	5	5	320	25	94
	a373	2778	263	14.7	0.89	0.54		0.0460	2.0	0.3342	3.2 0.05267 2.5 0.63 290	6	8	315	57	92
	a374	2177	201	10.7	0.59	b.d.		0.0489	2.2	0.3525	3.1 0.05223 2.2 0.71 308	7	8	296	50	104
	a375	1368	129	7.2	0.80	b.d.		0.0485	2.5	0.3530	4.0 0.05275 3.1 0.62 306	7	11	318	71	96
	a376	3408	322	17.0	0.55	0.07		0.0491	1.9	0.3537	2.4 0.05222 1.5 0.77 309	6	6	295	35	105
	a378	6613	618	34.4	0.79	0.20		0.0488	1.8	0.3558	2.1 0.05285 1.1 0.85 307	5	6	322	26	95
	a379	1657	148	7.5	0.32	0.21		0.0495	1.9	0.3585	3.0 0.05255 2.2 0.65 311	6	8	309	51	101
	a380	4414	425	23.3	0.82	0.44		0.0477	1.8	0.3488	2.6 0.05304 1.9 0.69 300	5	7	331	43	91
	a381	1050	90	4.3	0.36	b.d.		0.0461	2.6	0.3294	4.3 0.05183 3.5 0.59 290	7	11	278	80	104
	a382	4158	336	18.4	0.72	b.d.		0.0486	1.8	0.3544	2.4 0.05294 1.6 0.75 306	5	6	326	36	94
	a388	6784	533	29.1	0.74	b.d.		0.0485	1.8	0.3515	2.2 0.05256 1.2 0.82 305	5	6	310	28	98

et al., 2016. Supplementary Table S2 (continued):

  Results of LA-SF-ICPMS U-Pb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

		207 Pb a	U	b	Pb b	Th b	206 Pbc	c	206 Pb d	±2σ	207 Pb e	±2σ	207 Pb d	±2σ	ρ	f	206 Pb ±2σ 207 Pb ±2σ 207 Pb ±2σ conc. g
		(cps)	(ppm) (ppm)	U	(%)		238 U	(%)	235 U	(%)	206 Pb	(%)			238 U (Ma) U (Ma) 206 Pb (Ma) (%)
	a389	3718	266	14.5	0.72	0.07		0.0485	1.8	0.3515	2.5 0.05259 1.7 0.73 305	5	7	311	40	98
	a390	4714	335	19.7	1.13	0.04		0.0474	1.7	0.3449	2.2 0.05281 1.4 0.79 298	5	6	321	31	93
	a391	12266	814	51.3	1.29	b.d.		0.0490	1.7	0.3552	1.9 0.05261 0.9 0.89 308	5	5	312	20	99
	a392	4088	251	13.1	0.60	0.38		0.0485	1.8	0.3557	2.5 0.05315 1.7 0.73 306	5	7	335	38	91
	a393	3231	192	10.2	0.73	b.d.		0.0467	1.8	0.3427	2.7 0.05319 1.9 0.68 294	5	7	337	44	87
	a394	1687	93	4.9	0.51	b.d.		0.0493	1.9	0.3573	2.9 0.05256 2.2 0.66 310	6	8	310	49	100
	a395	6898	375	21.7	1.05	b.d.		0.0484	1.7	0.3520	2.1 0.05277 1.3 0.81 305	5	6	319	28	96
	a396	1975	101	4.7	0.19	0.07		0.0482	2.1	0.3449	3.3 0.05185 2.6 0.62 304	6	9	279	60	109
	a397	5103	249	14.1	0.88	0.04		0.0482	1.8	0.3492	2.3 0.05255 1.4 0.78 303	5	6	309	32	98
	a398	2501	116	5.9	0.50	0.01		0.0490	1.9	0.3563	2.6 0.05277 1.8 0.73 308	6	7	319	40	97
	a399	4639	211	11.5	0.65	0.38		0.0494	1.8	0.3580	2.4 0.05256 1.6 0.74 311	5	6	310	37	100
	a400	1869	78	4.0	0.49	b.d.		0.0472	2.4	0.3484	3.3 0.05352 2.2 0.74 297	7	9	351	50	85
	a401	3006	127	7.0	0.78	0.17		0.0488	1.8	0.3520	2.6 0.05233 1.8 0.72 307	6	7	300	40	102
	SGC-12-39
	Session #1 (April 9	th , 2014)
	a254	5399	432	30.6	1.82	b.d.		0.0463	1.9	0.3347	5.3 0.05245 5.0 0.35 292	5	14	305	113	96
	a255	3499	311	21.0	1.52	0.88		0.0447	2.0	0.3298	2.9 0.05348 2.1 0.70 282	6	7	349	47	81
	a256	3132	331	21.2	1.36	0.07		0.0485	1.8	0.3452	3.6 0.05166 3.1 0.50 305	5	9	270	71	113
	a257	3526	336	20.2	1.08	b.d.		0.0491	1.8	0.3524	2.5 0.05209 1.7 0.73 309	5	7	289	39	107
	a258	4042	363	19.4	0.58	0.02		0.0490	1.8	0.3545	2.8 0.05249 2.1 0.64 308	5	7	307	48	100
	a259	5015	481	32.9	1.67	0.03		0.0488	1.9	0.3540	2.6 0.05261 1.7 0.75 307	6	7	312	39	98
	a260	9069	814	43.6	0.63	0.32		0.0485	1.7	0.3568	3.3 0.05335 2.8 0.52 305	5	9	344	63	89
	a261	3638	346	22.9	1.34	0.07		0.0491	1.7	0.3542	2.6 0.05236 2.0 0.65 309	5	7	301	46	103
	a262	4199	396	21.0	0.62	0.02		0.0485	1.8	0.3500	2.5 0.05231 1.8 0.71 305	5	7	299	41	102
	a263	6428	499	36.8	1.81	b.d.		0.0493	1.8	0.3617	3.5 0.05322 3.0 0.52 310	6	9	338	67	92
	a264	4575	433	25.7	0.99	b.d.		0.0488	1.9	0.3568	2.4 0.05301 1.5 0.78 307	6	6	329	34	93
	a265	3325	237	15.1	1.32	3.96		0.0479	2.1	0.3463	5.5 0.05249 5.1 0.39 301	6	14	314	115	96
	a266	7339	432	24.5	0.56	3.39		0.0481	1.9	0.3430	5.8 0.05171 5.4 0.33 303	6	15	273	125	111
	a267	4846	430	26.2	1.11	b.d.		0.0489	1.8	0.3546	2.9 0.05265 2.2 0.64 307	6	8	314	51	98
	SGC-12-42
	Session #1 (April 9	th , 2014)
	a302	2768	271	13.5	0.42	b.d.		0.0472	1.8	0.3403	2.5 0.05230 1.7 0.74 297	5	6	298	38	100
	a303	9186	261	17.2	0.47 12.57 0.0491	2.2	0.3553	7.9 0.05247 7.6 0.28 309	7	21	306	172	101
	a304	2881	269	14.3	0.57	0.07		0.0485	1.9	0.3506	2.5 0.05240 1.7 0.74 305	6	7	303	39	101
	a305	3768	362	18.2	0.41	0.01		0.0487	1.8	0.3524	2.3 0.05248 1.4 0.78 307	5	6	306	32	100
	a306	10865 1062	66.4	1.28	b.d.		0.0488	1.7	0.3548	2.1 0.05273 1.1 0.84 307	5	6	317	26	97
	a307	2810	269	13.1	0.45	b.d.		0.0465	1.8	0.3410	2.6 0.05320 1.9 0.69 293	5	7	337	43	87
	a308	7511	718	39.0	0.72	b.d.		0.0485	1.8	0.3536	2.1 0.05290 1.2 0.82 305	5	6	324	28	94
	a309	4457	421	21.1	0.49	b.d.		0.0471	1.7	0.3419	2.1 0.05265 1.2 0.83 297	5	5	314	27	95
	a310	2707	250	12.3	0.40	b.d.		0.0474	1.9	0.3411	2.7 0.05215 1.9 0.72 299	6	7	292	42	102
	a311	3064	300	15.5	0.54	b.d.		0.0485	1.8	0.3547	2.7 0.05302 2.0 0.67 305	6	7	330	46	93
	a312	3476	322	16.9	0.60	0.01		0.0481	1.8	0.3486	2.9 0.05255 2.3 0.62 303	5	8	309	52	98
	a313	2893	271	12.6	0.16	0.06		0.0484	1.8	0.3509	2.6 0.05262 1.9 0.68 304	5	7	312	43	97
	a314	2794	271	12.6	0.16	b.d.		0.0485	1.8	0.3456	3.3 0.05169 2.7 0.56 305	6	9	272	63	112
	a315	3557	355	15.5	0.09	0.99		0.0464	1.9	0.3343	3.0 0.05224 2.3 0.64 292	5	8	296	52	99
	a316	4969	486	26.2	0.63	b.d.		0.0492	1.8	0.3577	2.5 0.05269 1.7 0.73 310	5	7	315	38	98
	a317	2963	280	12.6	0.08	0.08		0.0480	1.9	0.3472	2.8 0.05243 2.0 0.68 302	6	7	304	46	99
	206 Pb/	238 U error is the quadratic addition of the within run precision (2σ) and the external reproducibility (2σ ext.) of the reference zircon GJ-1
	207 Pb/	206 Pb uncertainty is calculated using	207 Pb signal dependent error propagation following Gerdes & Zeh (2009)
	207 Pb/ 235 U error is the quadratic addition of the 207 Pb/ 206 Pb and 206 Pb/ 238 U uncertainties
	(a) Within-run background-corrected mean	207 Pb signal in cps (counts per second).

Table 1 :

 1 Whole-rock geochemical data for samples newly analyzed in the scope of this study

	Sample	LR33a	LR33b	LR34	D2-1	PRC51	PRC55	SC-13-10	SGC 12 015B SGC 12 015D
	Ref ALS	LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482
	Long	4.113827	4.113827	4.113827	4.34499	4.101357	4.101357	3.65903	4.22173	4.22173
	Lat	45.28477	45.28477	45.28477	44.58553	45.32981	45.32981	45.22445	44.75042	44.75042
	Locality	La Roche	La Roche	La Roche	Lamastre	Pont-Rouge quarry	Pont-Rouge quarry	Pubellier	Peyron	Peyron
	Type	vaugnerite	vaugnerite	vaugnerite	vaugnerite	syenite	syenite	vaugnerite	vaugnerite	vaugnerite
	Details	fine-grained, HAS	coarse-grained, HAS	HAS	sample courtesy of V. Gardien	fine-grained, LAS	LAS	light facies	fine-grained, loose	fine-grained vgn. + equigranular gr., loose
	SiO 2	55.40	55.50	61.70	47.70	61.40	62.10	60.20	52.50	52.40
	Al 2 O 3	19.55	18.10	17.55	10.95	14.30	16.20	16.10	17.05	17.05
	Fe 2 O 3	6.82	7.17	5.93	10.40	5.03	5.55	5.51	9.30	9.29
	CaO	4.21	4.06	3.83	8.98	2.59	1.76	4.75	5.80	5.80
	MgO	3.08	4.01	2.16	12.95	5.25	2.87	4.54	5.56	5.58
	Na 2 O	3.53	3.30	3.96	1.16	2.10	3.35	2.70	2.58	2.56
	K 2 O	2.54	3.12	2.58	4.68	5.15	4.47	4.86	2.57	2.53
	Cr 2 O 3	0.01	0.01	<0.01	0.12	0.03	0.01	0.02	0.01	0.01
	TiO 2	1.32	0.99	1.18	1.96	1.32	1.33	0.93	1.80	1.78
	MnO	0.06	0.08	0.05	0.13	0.07	0.07	0.08	0.12	0.13
	P 2 O 5	0.34	0.43	0.34	0.51	1.14	0.69	0.47	0.55	0.54
	SrO	0.12	0.07	0.07	0.04	0.08	0.05	0.08	0.06	0.06
	BaO	0.11	0.10	0.13	0.40	0.33	0.18	0.21	0.11	0.10
	C	0.15	0.12	0.02	0.07	0.03	0.02	<0.01	0.03	0.03
	S	0.07	0.10	0.01	0.39	0.02	0.02	0.02	0.09	0.09
	Ba	1135	975	1200	3820	3060	1815	1915	1075	993
	Ce	74.7	66.3	114.5	50.6	218.0	266.0	164.0	91.9	91.7
	Cr	50	110	10	930	240	80	120	140	140
	Cs	8.72	11.75	7.21	4.34	16.40	8.29	13.40	7.91	8.24
	Dy	4.41	2.76	5.23	4.29	4.83	5.71	3.96	7.63	6.61
	Er	2.11	2.05	2.51	1.81	2.02	2.51	1.86	3.99	4.29
	Eu	2.05	1.84	1.51	1.61	2.67	2.27	2.55	2.10	1.93
	Ga	27.2	23.7	25.5	14.4	25.4	28.2	21.0	20.6	22.5
	Gd	5.26	5.06	6.72	5.13	9.87	9.47	7.71	8.98	9.33
	Hf	5.9	5.3	11.0	2.8	22.7	15.8	7.7	7.7	7.5
	Ho	0.81	0.71	0.87	0.78	0.72	0.92	0.71	1.35	1.43
	La	36.8	32.5	60.6	23.2	96.5	126.5	88.6	43.3	47.6
	Lu	0.23	0.17	0.24	0.33	0.17	0.20	0.29	0.54	0.53
	Nb	12.1	10.6	15.8	9.7	60.5	32.3	17.1	23.6	22.6
	Nd	35.4	33.3	44.4	27.5	100.5	111.5	68.7	46.2	43.9
	Pr	8.68	7.88	12.55	6.26	26.30	31.20	18.50	11.20	10.50
	Rb	147.0	185.5	171.5	210.0	284.0	227.0	200.0	97.5	95.6
	Sm	7.26	6.04	8.75	6.15	18.85	18.65	10.50	9.27	9.65
	Sn	4	3	3	2	8	2	9	2	3
	Sr	775.0	648.0	582.0	306.0	681.0	419.0	680.0	479.0	473.0
	Ta	0.7	1.0	1.2	0.7	3.5	1.5	2.1	1.4	1.6
	Tb	0.71	0.64	1.00	0.74	1.21	1.19	0.95	1.33	1.11
	Th	5.04	5.24	13.75	5.98	45.90	42.40	28.70	8.70	8.48
	Tl	0.7	0.7	1.1	0.6	1.4	0.9	1.0	0.6	<0.5
	Tm	0.31	0.25	0.31	0.26	0.24	0.29	0.22	0.63	0.56
	U	1.39	1.16	2.59	1.26	10.20	7.25	13.60	1.97	1.54
	V	133	125	85	360	62	85	106	146	141
	W	<1	<1	<1	3	<1	1	1	2	15
	Y	17.9	15.5	24.1	21	21.7	23.4	20.2	36.2	35.9
	Yb	1.50	1.33	2.17	1.83	1.44	1.58	1.86	3.43	3.39
	Zr	260	189	412	99	875	577	295	310	308
	As	0.2	0.2	1.8	0.6	1.1	1.4	<0.1	3.4	2.2
	Bi	0.04	0.04	0.03	0.04	0.14	0.04	0.16	0.11	0.09
	Hg	<0.005	<0.005	0.005	<0.005	<0.005	<0.005	<0.005	<0.005	<0.005
	Sb	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	0.05	<0.05
	Se	0.6	0.4	0.8	0.7	0.9	0.6	0.3	0.4	0.7
	Te	<0.01	0.02	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
	LOI	2.62	1.99	1.11	1.88	1.15	1.74	1.12	2.23	2.14
	Total	99.71	98.93	100.59	101.86	99.94	100.37	101.57	100.24	99.97
	Ag	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5
	Cd	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5
	Co	20	23	12	49	16	14	19	30	30
	Cu	16	26	10	44	10	8	50	24	19
	Li	30	30	20	40	30	60	50	50	50
	Mo	<1	<1	<1	1	<1	2	1	1	1
	Ni	26	54	8	193	130	16	59	48	45
	Pb	14	12	17	6	47	41	39	11	10
	Sc	21	13	15	38	11	13	12	19	20
	Zn	78	85	112	77	84	111	61	106	91
	Ge
	In
	Re

Couzinié et al., 2016. Supp.

Couzinié et al., 2016. Supp. Table 1 (cont.):

  Whole-rock geochemical data for samples newly analyzed in the scope of this study

	Sample	SGC 12 017

SGC 12 019 SGC 12 035A SGC 12 035B SGC 12 038A SGC 12 041B SGC 12 046 SGC 12 054B SGC 12 060

	Ref ALS	LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482
	Long	4.22375	4.23872	4.30583	4.30583	4.0701	4.27347	4.28713	4.34852	4.07357
	Lat	44.74817	44.74693	44.65670	44.65670	44.60028	44.67322	44.55378	44.69622	44.67992
	Locality	Peyron	Burzet	Pont-de-Bayzan	Pont-de-Bayzan	Loubaresse	Meyras	Largentiere	Chadenet	Pei Plot
	Type	vaugnerite	vaugnerite	vaugnerite	vaugnerite	vaugnerite	vaugnerite	vaugnerite	vaugnerite	vaugnerite
								medium-	at the contact	medium-
	Details	coarse-grained vgn.	enclave within Velay granite	intermediate rim of the sill	core of the sill	intermediate facies	intermediate facies	grained, darkest facies,	with the "late-migmatitic"	grained, spotted-
								Kfs blasts	granite	facies, folded
	SiO 2	50.50	55.40	56.80	55.70	59.60	53.40	56.40	60.60	58.70
	Al 2 O 3	16.50	17.75	18.05	18.10	16.75	17.95	15.45	16.05	16.90
	Fe 2 O 3	9.17	8.12	7.85	8.04	5.31	8.80	7.00	8.45	6.40
	CaO	6.13	3.39	4.09	4.06	3.00	4.80	4.25	3.78	4.18
	MgO	5.55	4.62	3.18	3.50	3.08	4.95	4.60	2.60	4.18
	Na 2 O	3.31	1.76	1.94	1.46	3.65	2.39	2.16	3.56	2.24
	K 2 O	2.69	3.66	3.70	4.32	3.27	3.66	4.20	2.42	3.61
	Cr 2 O 3	0.02	0.01	<0.01	<0.01	0.01	0.01	0.01	<0.01	0.02
	TiO 2	1.60	1.96	1.48	1.45	1.55	1.94	0.92	1.78	1.44
	MnO	0.12	0.11	0.09	0.10	0.07	0.10	0.10	0.12	0.10
	P 2 O 5	0.46	0.59	0.54	0.52	0.59	0.51	0.53	0.49	0.73
	SrO	0.07	0.05	0.06	0.08	0.08	0.05	0.07	0.03	0.05
	BaO	0.09	0.08	0.16	0.19	0.12	0.13	0.14	0.06	0.16
	C	<0.01	<0.01	0.07	0.10	<0.01	<0.01	0.02	<0.01	<0.01
	S	0.06	0.01	0.07	0.05	0.02	0.02	0.07	0.04	0.03
	Ba	877	817	1560	1935	1155	1320	1405	548	1580
	Ce	88.5	93.9	100.5	96.1	177.0	153.0	71.7	86.5	145.0
	Cr	150	100	10	10	70	110	140	30	140
	Cs	3.26	14.40	10.95	13.50	10.70	12.70	15.25	5.67	22.60
	Dy	6.67	5.61	6.16	6.57	5.93	6.90	4.68	8.38	6.27
	Er	3.71	2.56	3.87	3.12	2.40	3.01	2.72	5.04	2.66
	Eu	1.76	2.60	2.00	1.97	2.51	2.43	1.36	1.79	2.23
	Ga	20.2	22.0	23.5	28.3	27.2	28.5	18.0	23.2	22.1
	Gd	7.74	9.36	9.43	7.53	9.37	9.94	5.88	9.23	8.94
	Hf	6.1	7.3	8.0	8.3	13.2	11.7	5.1	6.8	14.2
	Ho	1.20	1.05	1.13	1.12	0.98	1.21	0.87	1.61	0.86
	La	42.5	46.3	49.5	48.1	86.8	73.9	35.1	42.1	76.6
	Lu	0.54	0.32	0.39	0.46	0.30	0.31	0.45	0.59	0.28
	Nb	23.2	29.2	18.4	18.5	32.8	24.7	13.2	19.7	28.6
	Nd	42.7	50.1	48.6	48.6	78.8	82.1	35.0	42.9	75.2
	Pr	9.95	12.15	11.80	12.35	20.20	19.95	9.04	10.40	19.20
	Rb	81.2	164.0	181.0	219.0	218.0	175.0	148.5	159.0	300.0
	Sm	9.17	10.40	9.11	9.24	12.85	12.65	7.29	9.49	12.30
	Sn	3	4	5	5	4	5	4	3	12
	Sr	526.0	381.0	451.0	486.0	515.0	395.0	522.0	268.0	435.0
	Ta	1.1	1.1	1.5	1.2	1.9	2.1	1.1	1.4	1.9
	Tb	1.05	1.20	1.01	1.07	1.15	1.26	0.91	1.36	1.19
	Th	8.48	8.40	13.90	12.45	20.00	16.15	14.35	12.55	23.60
	Tl	<0.5	0.8	0.8	0.8	1.0	0.6	0.9	0.6	1.6
	Tm	0.57	0.35	0.50	0.54	0.41	0.42	0.39	0.70	0.41
	U	1.28	2.14	3.52	2.80	2.99	3.15	4.09	4.00	5.45
	V	139	91	121	128	62	121	155	142	142
	W	2	6	1	2	1	1	1	4	2
	Y	31.7	26.8	29.6	31.7	26	32.3	27.4	42.4	24.8
	Yb	3.06	2.13	3.04	2.52	2.18	2.64	2.32	3.80	2.27
	Zr	282	284	313	312	543	427	212	281	537
	As	6.5	6.7	1.3	1.7	2.3	1.4	2.2	2.3	1.8
	Bi	0.05	0.22	0.16	0.14	0.15	0.2	0.07	0.09	0.32
	Hg	<0.005	<0.005	<0.005	0.005	0.006	0.006	<0.005	<0.005	<0.005
	Sb	<0.05	<0.05	0.13	0.08	0.05	0.05	0.09	0.07	0.05
	Se	0.7	1.3	1.4	1.3	0.8	0.6	0.6	1.1	1.1
	Te	0.01	<0.01	<0.01	0.01	0.01	<0.01	<0.01	0.01	<0.01
	LOI	1.8	3.66	2.31	2.53	1.65	2.08	2.2	1.63	1.44
	Total	98.01	101.16	100.25	100.05	98.73	100.77	98.03	101.57	100.15
	Ag	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5
	Cd	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5
	Co	29	26	19	18	16	27	20	18	17
	Cu	15	15	8	6	8	9	13	15	38
	Li	40	100	100	100	90	60	80	70	110
	Mo	1	1	1	<1	<1	<1	1	<1	<1
	Ni	48	57	2	3	37	17	19	4	17
	Pb	8	13	15	22	16	10	22	14	2
	Sc	20	13	13	13	9	20	21	22	18
	Zn	95	97	93	93	77	95	84	95	76
	Ge
	In
	Re

Couzinié et al., 2016. Supp. Table 1 (cont.):

  Whole-rock geochemical data for samples newly analyzed in the scope of this study

	Sample	SGC 12 061 SGC 12 010A SGC 12 010B SGC 12 011A SGC 12 011B SGC 12 012	SC-13-02b	SC-13-06	SC-13-07
	Ref ALS	LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482
	Long	4.07418	4.05583	4.05583	4.08857	4.08857	4.08857	3.47373	3.79974	3.79974
	Lat	44.68115	44.50997	44.50997	44.49843	44.49843	44.49818	44.68734	44.82754	44.82754
	Locality	Pei Plot	La Borne	La Borne	La Borne	La Borne	La Borne	Moulin de Linas	Jagonzac	Jagonzac
	Type	vaugnerite	lamprophyre lamprophyre lamprophyre lamprophyre lamprophyre	vaugnerite	vaugnerite	vaugnerite
	Details	equigranular	dyke	dyke	dyke	dyke	dyke	fine-grained	coarse-grained	dark, fine-grained
	SiO 2	57.80	55.70	53.50	54.70	55.10	56.50	62.00	52.30	55.50
	Al 2 O 3	17.30	12.90	14.15	14.45	12.90	16.00	12.45	15.30	18.00
	Fe 2 O 3	6.09	6.75	8.65	6.79	6.36	7.45	7.42	7.30	7.53
	CaO	4.47	5.77	5.37	5.49	4.27	3.37	3.27	7.32	6.47
	MgO	2.54	7.01	8.47	6.28	9.04	5.34	8.00	6.42	3.79
	Na 2 O	2.59	2.17	1.16	2.16	1.66	2.46	1.50	2.57	3.75
	K 2 O	5.41	5.31	4.87	5.79	6.32	3.93	4.00	4.48	3.43
	Cr 2 O 3	<0.01	0.06	0.07	0.05	0.06	0.02	0.06	0.03	<0.01
	TiO 2	1.14	1.05	1.20	1.40	1.25	1.06	0.98	1.37	1.06
	MnO	0.08	0.22	0.14	0.10	0.08	0.10	0.13	0.11	0.11
	P 2 O 5	0.56	0.78	0.91	1.01	0.97	0.66	0.32	0.90	0.51
	SrO	0.07	0.08	0.07	0.09	0.08	0.10	0.01	0.10	0.12
	BaO	0.17	0.34	0.29	0.31	0.37	0.29	0.07	0.38	0.22
	C	0.01	0.02	0.02	0.03	0.02	0.02	0.03	<0.01	0.02
	S	0.02	0.01	0.02	0.15	0.02	0.15	0.02	0.03	0.09
	Ba	1710	3240	2510	3000	3570	2740	573	3420	2020
	Ce	125.5	185.0	219.0	145.5	202.0	146.5	37.0	136.0	165.0
	Cr	30	520	590	390	500	220	430	220	<10
	Cs	7.01	2.97	61.60	15.80	19.45	47.60	28.00	10.80	12.60
	Dy	6.21	8.38	8.14	7.14	7.66	7.50	4.39	6.15	5.84
	Er	3.12	2.80	3.29	2.89	3.32	3.62	2.30	3.26	2.89
	Eu	2.09	3.94	3.99	3.18	3.55	2.95	0.63	3.46	2.93
	Ga	24.9	17.1	21.0	18.5	18.9	22.0	23.1	21.2	22.9
	Gd	9.00	15.15	15.75	11.25	14.15	10.30	5.23	10.20	9.65
	Hf	12.6	16.1	17.4	14.3	12.9	13.7	1.6	5.2	6.9
	Ho	1.10	1.37	1.22	1.17	1.39	1.10	0.94	1.02	1.08
	La	63.1	94.1	88.6	70.8	104.0	69.8	16.5	64.8	88.6
	Lu	0.47	0.36	0.36	0.49	0.37	0.45	0.31	0.37	0.34
	Nb	20.5	23.4	24.9	37.7	28.6	30.3	10.3	20.3	15.4
	Nd	63.8	133.0	122.5	78.5	130.0	74.4	25.8	73.7	74.9
	Pr	16.35	29.20	28.40	18.50	30.40	18.35	5.35	18.70	19.85
	Rb	211.0	136.5	312.0	179.5	235.0	253.0	319.0	205.0	148.5
	Sm	10.65	24.10	22.70	14.75	24.70	15.30	6.82	13.80	14.80
	Sn	5	30	66	74	50	75	9	12	6
	Sr	590.0	654.0	543.0	756.0	682.0	802.0	168.5	961.0	1045.0
	Ta	1.6	1.3	1.1	1.1	1.2	1.2	1.0	1.5	1.4
	Tb	1.25	1.88	1.72	1.31	1.68	1.36	0.71	1.40	1.20
	Th	22.90	76.50	82.90	31.40	59.40	51.60	3.66	27.70	32.60
	Tl	0.6	0.7	1.8	0.9	0.9	1.9	1.6	1.7	1.0
	Tm	0.30	0.44	0.35	0.46	0.39	0.49	0.26	0.41	0.44
	U	4.63	9.72	10.15	7.10	11.60	10.60	3.78	7.39	6.91
	V	73	136	140	158	116	103	127	182	172
	W	1	12	346	5	2	34	8	5	1
	Y	28.4	39.1	31.8	33.6	40.3	33.5	22	31.2	29.1
	Yb	2.67	1.93	2.13	2.38	2.02	2.63	2.11	2.63	2.55
	Zr	459	532	528	577	498	509	49	231	275
	As	0.2	202	>250	204	222	>250	7.9	<0.1	0.7
	Bi	0.12	1.3	1.46	0.63	0.6	0.16	0.81	0.13	0.25
	Hg	<0.005	0.007	0.06	0.011	0.006	0.014	<0.005	<0.005	<0.005
	Sb	<0.05	0.39	0.27	0.8	1.02	1.03	<0.05	<0.05	<0.05
	Se	0.7	0.7	1	0.9	1.1	1.1	0.8	0.4	0.3
	Te	<0.01	0.02	0.04	0.02	0.01	0.01	<0.01	<0.01	<0.01
	LOI	1.68	2.2	2.73	1.51	2.52	1.84	1.71	1.33	1.27
	Total	99.9	100.34	101.58	100.13	100.98	99.12	101.92	99.91	101.76
	Ag	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5
	Cd	<0.5	0.8	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5
	Co	12	26	32	25	28	23	30	24	17
	Cu	3	1	1	9	2	47	15	13	15
	Li	50	40	110	50	40	50	140	70	70
	Mo	<1	<1	<1	1	<1	2	<1	<1	<1
	Ni	3	151	154	35	212	85	130	49	2
	Pb	24	42	24	65	61	26	7	40	37
	Sc	14	20	23	22	16	18	18	20	14
	Zn	83	190	205	126	83	194	99	79	75
	Ge
	In
	Re

Couzinié et al., 2016. Supp. Table 1 (cont.):

  Whole-rock geochemical data for samples newly analyzed in the scope of this study

	Sample	533-1	533-2	LR31	LR32	PRC53	PRC54	SC-13-09	SGC 12 026 SGC 12 039
	Ref ALS	LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482 LR13221482
	Long	4.37411	4.37411	4.113827	4.113827	4.101357	4.101357	3.65911	4.30658	4.07053
	Lat	44.58249	44.58249	45.28477	45.28477	45.32981	45.32981	45.22474	44.65778	44.60045
	Locality	Lamastre	Lamastre	La Roche	La Roche	Pont-Rouge quarry	Pont-Rouge quarry	Pubellier	Pont-de-Bayzan	Loubaresse
	Type	vaugnerite	vaugnerite	vaugnerite	vaugnerite	syenite	syenite	vaugnerite	vaugnerite	vaugnerite
	Details	sample courtesy of V. Gardien	sample courtesy of V. Gardien	Bt-clusters, HAS	Bt-clusters, HAS	LAS	LAS	dark facies	rounded enclave	coarse-granied, dark facies
	SiO 2	56.40	50.50	52.80	49.90	60.00	61.80	57.70	50.60	57.60
	Al 2 O 3	11.45	9.25	15.05	14.75	15.95	15.90	13.25	13.45	14.70
	Fe 2 O 3	5.96	9.27	6.65	7.95	5.60	5.32	6.80	8.27	6.13
	CaO	6.12	9.83	6.26	5.36	2.09	2.29	3.46	6.81	4.11
	MgO	7.80	13.25	9.51	9.10	3.14	2.81	8.38	7.73	5.74
	Na 2 O	2.00	1.45	2.41	2.24	2.06	2.27	2.30	1.51	2.96
	K 2 O	4.16	2.93	1.77	2.44	6.69	6.38	4.21	5.71	3.42
	Cr 2 O 3	0.07	0.13	0.08	0.08	0.01	0.01	0.06	0.04	0.03
	TiO 2	1.06	0.92	0.70	1.13	1.46	1.30	0.72	1.51	1.36
	MnO	0.08	0.14	0.10	0.11	0.07	0.07	0.10	0.11	0.09
	P 2 O 5	0.60	0.60	0.35	0.37	0.75	0.65	0.32	1.22	0.68
	SrO	0.03	0.04	0.08	0.07	0.06	0.06	0.08	0.06	0.10
	BaO	0.18	0.18	0.06	0.08	0.23	0.20	0.15	0.46	0.19
	C	0.02	0.06	0.26	0.29	0.02	0.02	0.01	0.26	0.02
	S	0.12	0.23	0.06	0.07	0.04	0.04	0.08	0.05	0.04
	Ba	1780	1580	597	746	2250	1890	1475	4490	1430
	Ce	36.4	53.3	64.7	81.6	223.0	252.0	123.0	77.2	177.5
	Cr	560	910	640	570	90	90	460	310	180
	Cs	8.43	2.36	20.40	16.35	18.90	16.65	15.70	13.30	5.94
	Dy	3.48	4.18	4.07	5.47	5.22	6.02	3.41	7.40	4.20
	Er	1.56	2.08	2.01	3.43	2.50	2.24	1.49	3.89	1.75
	Eu	1.35	1.49	1.24	1.76	3.07	2.77	1.75	2.04	2.31
	Ga	16.5	12.2	18.1	17.5	27.9	27.3	18.9	17.8	20.4
	Gd	4.23	5.94	4.77	6.11	8.64	9.66	6.28	8.25	8.52
	Hf	1.9	4.0	2.9	4.3	15.6	15.0	6.3	5.0	10.2
	Ho	0.64	0.85	0.67	1.05	0.86	0.96	0.48	1.23	0.62
	La	14.5	24.5	34.7	41.3	103.0	122.0	61.7	33.8	91.5
	Lu	0.15	0.23	0.28	0.42	0.27	0.32	0.27	0.49	0.24
	Nb	14.3	9.0	9.6	14.1	36.8	36.6	15.2	14.0	23.4
	Nd	20.2	27.8	26.6	38.7	105.0	106.0	51.4	41.9	77.5
	Pr	4.84	6.57	7.69	10.20	27.00	28.70	14.10	9.71	20.80
	Rb	232.0	95.7	89.7	105.0	305.0	303.0	180.0	173.0	138.5
	Sm	6.07	6.16	5.45	7.51	17.95	16.65	8.83	8.22	12.95
	Sn	19	3	2	2	10	8	6	4	6
	Sr	250.0	345.0	641.0	570.0	503.0	522.0	485.0	490.0	577.0
	Ta	2.0	0.7	0.6	1.1	2.3	2.3	1.4	1.1	1.0
	Tb	0.62	0.81	0.69	1.11	1.14	1.09	0.72	1.13	0.92
	Th	4.25	6.19	8.18	8.06	40.10	50.90	25.40	6.24	23.00
	Tl	0.9	0.5	<0.5	0.7	1.7	1.4	1.4	0.8	0.5
	Tm	0.13	0.19	0.23	0.45	0.30	0.28	0.17	0.53	0.27
	U	4.06	1.37	4.41	4.09	7.56	7.53	5.80	2.64	3.01
	V	212	175	139	192	90	75	122	237	73
	W	6	<1	2	<1	<1	1	6	7	1
	Y	16.7	18.7	17.7	24.4	21.8	25.1	17.1	33.1	18.6
	Yb	1.07	1.64	1.40	2.80	1.63	1.83	1.72	3.57	1.18
	Zr	76	156	98	149	641	559	259	187	437
	As	0.8	0.4	2.1	2.4	2.7	0.6	0.3	3.8	3.2
	Bi	0.15	0.08	0.06	0.05	0.15	0.21	0.19	0.21	0.12
	Hg	<0.005	<0.005	<0.005	<0.005	<0.005	0.008	<0.005	<0.005	<0.005
	Sb	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	0.15	<0.05
	Se	0.4	0.2	<0.2	0.4	0.9	0.9	0.6	0.6	0.6
	Te	<0.01	<0.01	0.01	0.01	<0.01	0.01	<0.01	<0.01	<0.01
	LOI	1.12	1.88	4.45	4.41	1.46	1.28	1.45	2.41	0.99
	Total	97.03	100.37	100.27	97.99	99.57	100.34	98.98	99.89	98.1
	Ag	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5
	Cd	1.5	<0.5	<0.5	0.5	<0.5	<0.5	<0.5	<0.5	<0.5
	Co	27	46	46	44	16	14	31	25	21
	Cu	41	36	34	34	16	17	30	11	10
	Li	60	30	40	50	30	30	50	50	50
	Mo	<1	1	<1	1	<1	<1	1	1	1
	Ni	23	61	232	200	17	16	207	6	136
	Pb	10	13	9	9	42	45	43	20	8
	Sc	26	36	25	29	13	13	15	31	13
	Zn	82	76	82	93	94	100	73	83	84
	Ge
	In
	Re

Couzinié et al., 2016. Supp. Table 1 (cont.):

  Whole-rock geochemical data for samples newly analyzed in the scope of this study

	Sample	SGC 12 042 SGC 12 013	SC-13-02a	SC-13-05
	Ref ALS	LR13221482 LR13221482 LR13221482 LR13221482
	Long	4.27383	4.08863	3.47373	3.63152
	Lat	44.67262	44.49668	44.68734	44.76482
	Locality	Meyras	La Borne	Moulin de Linas	L'Aldeyres
	Type	vaugnerite	lamprophyre	vaugnerite	vaugnerite
	Details	rounded body	medium-grained dyke	coarse-grained	coarse-grained
	SiO 2	51.00	50.20	58.90	50.80
	Al 2 O 3	17.80	13.00	13.15	12.70
	Fe 2 O 3	8.96	8.22	6.75	10.20
	CaO	5.26	4.95	4.90	6.54
	MgO	5.20	11.45	6.88	12.60
	Na 2 O	1.41	1.41	2.33	2.14
	K 2 O	4.88	4.51	3.00	3.19
	Cr 2 O 3	0.01	0.08	0.05	0.08
	TiO 2	1.94	1.10	0.90	0.97
	MnO	0.10	0.12	0.09	0.14
	P 2 O 5	0.56	0.67	0.28	0.36
	SrO	0.06	0.05	0.02	0.04
	BaO	0.14	0.20	0.07	0.16
	C	0.14	0.32	0.02	0.01
	S	0.08	0.02	0.05	0.12
	Ba	1365	1915	631	1375
	Ce	152.0	97.4	72.7	75.0
	Cr	100	730	360	590
	Cs	14.65	30.60	15.45	9.20
	Dy	7.30	4.92	4.39	4.03
	Er	3.36	2.60	2.41	1.84
	Eu	2.56	2.24	1.67	1.87
	Ga	29.0	18.1	17.5	16.1
	Gd	10.00	7.71	5.71	6.79
	Hf	13.7	8.1	6.4	5.4
	Ho	1.17	0.94	0.73	0.65
	La	67.6	43.6	33.6	35.8
	Lu	0.42	0.37	0.36	0.25
	Nb	28.6	17.4	11.5	13.2
	Nd	80.7	55.1	37.2	39.7
	Pr	19.60	13.15	9.11	9.71
	Rb	210.0	199.5	194.0	139.5
	Sm	12.85	10.30	8.00	8.40
	Sn	4	6	9	4
	Sr	421.0	406.0	302.0	413.0
	Ta	2.1	1.0	1.4	1.1
	Tb	1.40	0.92	0.85	0.81
	Th	17.95	24.60	16.75	16.15
	Tl	0.7	1.2	0.8	1.7
	Tm	0.56	0.36	0.26	0.19
	U	2.77	5.61	6.18	4.93
	V	117	150	102	135
	W	1	2	4	3
	Y	31.4	23.8	23.7	19.8
	Yb	2.68	2.30	2.14	1.55
	Zr	529	330	222	185
	As	0.8	57.6	4.3	2.6
	Bi	0.12	0.17	0.09	0.25
	Hg	<0.005	0.007	<0.005	0.009
	Sb	0.05	2.1	0.06	<0.05
	Se	0.5	0.6	0.6	0.3
	Te	<0.01	0.01	<0.01	<0.01
	LOI	2.46	3.65	1.26	1.82
	Total	99.78	99.61	98.58	101.74
	Ag	<0.5	<0.5	<0.5	<0.5
	Cd	<0.5	<0.5	<0.5	0.6
	Co	27	40	28	52
	Cu	19	17	32	43
	Li	90	70	90	30
	Mo	1	1	<1	1
	Ni	16	254	110	152
	Pb	9	23	12	22
	Sc	19	21	14	20
	Zn	105	92	69	91
	Ge
	In
	Re

Couzinié et al., 2016. Supp.Table 2 :

 2 In situ LA-MC-ICPMS Lu-Hf isotope data for zircon standards analyzed in this study 176 Yb/ 177 Hf a ±2s 176 Lu/ 177 Hf a ±2s 178 Hf/ 177 Hf 180 Hf/ 177 Hf Sig Hf b 176 Hf/ 177 Hf ±2s 176 Hf/

										177 Hf (t) eHf(t) c ±2s T DM2	d
								(V)				(Ga)
	GJ1-1	0.0089	1	0.00029	0	1.46714	1.88665	9	0.282006	0.282003	-14.2	0.8 2.25
	GJ1-2	0.0088	1	0.00029	0	1.46718	1.88677	9	0.281989	0.281986	-14.8	1.0 2.28
	GJ1-3	0.0101	1	0.00033	0	1.46713	1.88660	9	0.282007	0.282004	-14.1	1.0 2.25
	GJ1-4	0.0081	0	0.00028	0	1.46711	1.88673	9	0.281992	0.281989	-14.7	1.0 2.27
	GJ1-5	0.0077	0	0.00026	0	1.46714	1.88662	13	0.282016	0.282013	-13.8	0.9 2.23
	GJ1-6	0.0071	0	0.00025	0	1.46715	1.88682	12	0.281994	0.281991	-14.6	0.9 2.27
	GJ1-7	0.0077	0	0.00026	0	1.46713	1.88678	13	0.281996	0.281993	-14.5	0.9 2.27
	GJ1-8	0.0080	0	0.00026	0	1.46716	1.88671	13	0.281995	0.281992	-14.5	0.9 2.27
	GJ1-9	0.0082	1	0.00026	0	1.46714	1.88665	14	0.282006	0.282003	-14.2	0.8 2.25
	GJ1-10	0.0080	1	0.00026	0	1.46718	1.88664	13	0.282010	0.282007	-14.0	0.9 2.24
	GJ1-11	0.0072	0	0.00024	0	1.46716	1.88687	12	0.281982	0.281980	-15.0	0.8 2.29
	GJ1-12	0.0079	0	0.00025	0	1.46714	1.88679	12	0.281996	0.281993	-14.5	0.9 2.27
	GJ1-13	0.0081	1	0.00026	0	1.46714	1.88679	11	0.281988	0.281985	-14.8	0.9 2.28
	GJ1-14	0.0078	0	0.00025	0	1.46714	1.88673	11	0.282000	0.281997	-14.4	1.0 2.26
	GJ1-15	0.0075	1	0.00024	0	1.46711	1.88679	10	0.282002	0.282000	-14.3	0.9 2.25
	GJ1-16	0.0074	0	0.00024	0	1.46720	1.88675	10	0.281997	0.281994	-14.5	1.0 2.26
	GJ1-17	0.0082	1	0.00026	0	1.46715	1.88661	15	0.282002	0.281999	-14.3	0.8 2.25
	GJ1-18	0.0082	1	0.00026	0	1.46715	1.88676	15	0.282002	0.281999	-14.3	0.9 2.25
	GJ1-19	0.0074	0	0.00025	0	1.46710	1.88678	13	0.282014	0.282011	-13.9	0.9 2.23
	GJ1-20	0.0074	1	0.00024	0	1.46712	1.88668	14	0.282006	0.282003	-14.1	0.9 2.25
	GJ1-21	0.0076	1	0.00024	0	1.46713	1.88669	14	0.282015	0.282012	-13.8	0.9 2.23
	GJ1-22	0.0078	0	0.00025	0	1.46709	1.88670	14	0.281983	0.281980	-15.0	0.9 2.29
	Average (n=22)	0.0080		0.00026		1.46714	1.88672		0.282000		-14.4
	2 S.D. ext.	0.0013		0.00004		0.00005	0.00015		0.000020		0.7
	91500-1	0.0100	0	0.00034	0	1.46722	1.88678	7	0.282292	0.282285	6.2	0.9 1.50
	91500-2	0.0108	0	0.00036	0	1.46720	1.88673	7	0.282319	0.282312	7.1	1.1 1.44
	91500-3	0.0115	1	0.00038	0	1.46712	1.88653	7	0.282301	0.282293	6.5	1.0 1.48
	91500-4	0.0098	1	0.00032	0	1.46716	1.88670	12	0.282300	0.282294	6.5	0.9 1.48
	91500-5	0.0103	1	0.00033	0	1.46715	1.88672	12	0.282272	0.282266	5.5	0.9 1.53
	91500-6	0.0047	1	0.00016	0	1.46716	1.88674	10	0.282291	0.282288	6.3	0.9 1.49
	91500-7	0.0098	1	0.00032	0	1.46715	1.88668	10	0.282286	0.282279	6.0	1.0 1.51
	91500-8	0.0085	0	0.00028	0	1.46713	1.88680	9	0.282287	0.282281	6.1	1.0 1.50
	91500-9	0.0093	1	0.00031	0	1.46711	1.88670	9	0.282287	0.282281	6.0	0.9 1.51
	91500-10	0.0046	0	0.00015	0	1.46715	1.88664	13	0.282287	0.282283	6.1	0.9 1.50
	91500-11	0.0046	0	0.00015	0	1.46710	1.88653	12	0.282293	0.282290	6.4	0.9 1.49
	91500-12	0.0081	0	0.00027	0	1.46713	1.88665	13	0.282301	0.282296	6.6	0.9 1.48
	91500-13	0.0082	1	0.00026	0	1.46712	1.88660	13	0.282320	0.282314	7.2	0.9 1.44
	Average (n=13)	0.0085		0.00028		1.46715	1.88668		0.282295		6.4
	2 S.D. ext.	0.0048		0.00015		0.00007	0.00017		0.000027		0.9
	Pleso1	0.0048	1	0.00013	0	1.46715	1.88681	12	0.282480	0.282480	-3.3	1.0 1.44
	Pleso2	0.0060	1	0.00014	0	1.46714	1.88674	12	0.282474	0.282473	-3.5	0.9 1.46
	Pleso3	0.0074	0	0.00017	0	1.46720	1.88674	13	0.282466	0.282465	-3.8	0.9 1.47
	Pleso4	0.0067	1	0.00015	0	1.46715	1.88679	21	0.282465	0.282464	-3.9	0.9 1.47
	Pleso5	0.0051	1	0.00012	0	1.46715	1.88667	22	0.282468	0.282468	-3.7	0.8 1.47
	Pleso7	0.0037	1	0.00009	0	1.46712	1.88669	17	0.282475	0.282475	-3.5	0.8 1.45
	Pleso8	0.0046	2	0.00010	0	1.46715	1.88684	16	0.282464	0.282464	-3.9	0.9 1.48
	Pleso9	0.0061	2	0.00014	0	1.46715	1.88667	15	0.282466	0.282466	-3.8	0.8 1.47
	Pleso10	0.0066	2	0.00014	0	1.46713	1.88670	23	0.282466	0.282466	-3.8	0.8 1.47
	Pleso11	0.0048	1	0.00012	0	1.46711	1.88666	23	0.282480	0.282479	-3.3	0.8 1.44
	Pleso12	0.0044	0	0.00011	0	1.46711	1.88672	22	0.282474	0.282473	-3.5	0.9 1.46
	Pleso13	0.0043	0	0.00009	0	1.46714	1.88670	21	0.282482	0.282482	-3.2	0.8 1.44
	Pleso14	0.0044	0	0.00009	0	1.46715	1.88678	22	0.282477	0.282476	-3.4	0.8 1.45
	Average (n=13)	0.0053		0.00012		1.46714	1.88673		0.282472		-3.6
	2 S.D. ext.	0.0022		0.00005		0.00005	0.00012		0.000013		0.5
	DEGEO1	0.0063	0	0.00018	0	1.46722	1.88670	7	0.281739	0.281737	-24.4	1.1 2.77
	DEGEO2	0.0064	0	0.00018	0	1.46720	1.88685	7	0.281724	0.281722	-24.9	1.0 2.80
	DEGEO3	0.0065	0	0.00018	0	1.46715	1.88679	8	0.281722	0.281720	-25.0	1.0 2.80
	DEGEO4	0.0065	1	0.00017	0	1.46716	1.88670	12	0.281732	0.281730	-24.7	0.9 2.78
	DEGEO5	0.0062	1	0.00017	0	1.46718	1.88668	12	0.281727	0.281725	-24.8	1.0 2.79
	DEGEO6	0.0062	1	0.00017	0	1.46716	1.88676	10	0.281707	0.281706	-25.5	1.1 2.83
	DEGEO7	0.0063	1	0.00017	0	1.46712	1.88665	10	0.281735	0.281734	-24.5	1.0 2.78
	DEGEO8	0.0063	1	0.00017	0	1.46716	1.88677	9	0.281706	0.281705	-25.6	1.1 2.83
	DEGEO9	0.0062	1	0.00017	0	1.46712	1.88664	9	0.281702	0.281700	-25.7	0.9 2.84
	DEGEO12	0.0064	1	0.00017	0	1.46712	1.88668	13	0.281710	0.281708	-25.5	0.9 2.83
	DEGEO13	0.0061	1	0.00017	0	1.46713	1.88673	13	0.281728	0.281726	-24.8	0.9 2.79
	Average (n=11)	0.0063		0.00017		1.46716	1.88672		0.281721		-25.1
	2 S.D. ext.	0.0003		0.00001		0.00007	0.00013		0.000026		0.9

Couzinié et al., 2016. Supp. Tab. 2 (cont.):

  In situ LA-MC-ICPMS Lu-Hf isotope data for zircon standards analyzed in this study M=mass of respective isotope. The 176 Lu/ 177 Hf were calculated in a similar way by using the 175 Lu/ 177 Hf and b(Yb). Initial 176 Hf/ 177 Hf and eHf calculated using the apparent Pb-Pb age determined by LA-ICP-MS dating (see column f), and the CHUR parameters:176 Lu/ 177 Hf = 0.0336, and 176 Hf/ 177 Hf = 0.282785(Bouvier et al ., 2008). In situ LA-MC-ICPMS Lu-Hf isotope data for zircon in PCMM samples from the eastern FMC In situ LA-MC-ICPMS Lu-Hf isotope data for zircon in PCMM samples from the eastern FMC In situ LA-MC-ICPMS Lu-Hf isotope data for zircon in PCMM samples from the eastern FMC In situ LA-MC-ICPMS Lu-Hf isotope data for zircon in PCMM samples from the eastern FMC In situ LA-MC-ICPMS Lu-Hf isotope data for zircon in PCMM samples from the eastern FMC Initial 176 Hf/ 177 Hf and eHf calculated using an emplacement age of 311 Ma and the CHUR parameters:

	(a) Couzinié et al., 2016. Supp. Tab. 3 (cont.): 176 Yb/ 176 Yb/ 177 Hf = ( 176 Yb/ 173 Yb) true x ( 173 Yb/ 177 Hf) meas x (M 173(Yb) /M 177(Hf) ) b(Hf) , b(Hf) = ln( 179 Hf/ 177 Hf true / 176 Yb/ 177 Hf a ±2s 176 Lu/ 177 Hf a ±2s 178 Hf/ 177 Hf 180 Hf/ 177 Hf Sig Hf 179 Hf/ 177 Hf measured )/ ln (M 179(Hf )/M 177(Hf) ), b 176 Hf/ 177 Hf ±2s 176 Hf/ 177 Hf (t) eHf(t) 177 Hf a ±2s 176 Lu/ 177 Hf a ±2s 178 Hf/ 177 Hf 180 Hf/ 177 Hf Sig Hf b 176 Hf/ 177 Hf ±2s 176 Hf/ 177 Hf (t) eHf(t) Couzinié et al., 2016. Supp. Tab. 3 (cont.): 176 Yb/ 177 Hf a ±2s 176 Lu/ 177 Hf a ±2s 178 Hf/ 177 Hf 180 Hf/ 177 Hf Sig Hf b 176 Hf/ 177 Hf ±2s 176 Hf/ 177 Hf (t) eHf(t) Couzinié et al., 2016. Supp. Tab. 3 (cont.): 176 Yb/ 177 Hf a ±2s 176 Lu/ 177 Hf a ±2s 178 Hf/ 177 Hf 180 Hf/ 177 Hf Sig Hf b 176 Hf/ 177 Hf ±2s 176 Hf/ 177 Hf (t) eHf(t) Couzinié et al., 2016. Supp. Tab. 3 (cont.): 176 Yb/ 177 Hf a ±2s 176 Lu/ 177 Hf a ±2s 178 Hf/ 177 Hf 180 Hf/ 177 Hf Sig Hf b 176 Hf/ 177 Hf ±2s 176 Hf/ 177 Hf (t) eHf(t)	c ±2s T DM2 c ±2s T DM2 c ±2s T DM2 c ±2s T DM2 c ±2s T DM2	d d d d d
										(V) (V) (V) (V) (V)		(Ga) (Ga) (Ga) (Ga) (Ga)
	(b) Mean Hf signal in volt. Monzodiorite SC-13-05 Mean (n=18) a325 a266 a353	0.0163 0.0500 0.0148 0.0411	58 36 18	0.00049 0.00172 0.00048 0.00138		18 10 5	1.46709 1.46713 1.46716 1.46719	1.88634 1.88668 1.88674 1.88665	13 16 12	0.282543 0.282496 0.282519	0.282413 0.282533 0.282493 0.282511	-6.1 -2.3 1.0 1.36 1.58 -3.5 0.8 1.43 -2.9 0.9 1.40
	a131 a133 ±2σ (ext.) a326 a334 a267 Mean (n=16) a354 a358 (c) (d) two stage model age in billion years using the measured 0.0282 45 0.00086 0.0228 50 0.00075 0.0074 0.00021 0.0301 49 0.00105 0.0263 7 0.00093 0.0460 56 0.00131 0.0243 0.00073 0.0522 36 0.00169 0.0494 28 0.00162 a134 0.0264 55 0.00081 Qz Monzonite PRC-54 a335 0.0412 45 0.00142 ±2σ (ext.) 0.0228 0.00063 a360 0.0570 49 0.00184	13 15 16 3 15 11 7 176 Lu/ 177 Lu of each spot (first stage = age of zircon), 1.46714 1.88661 13 0.282454 1.46709 1.88622 7 0.282362 0.00012 0.00056 1.46710 1.88650 13 0.282518 1.46715 1.88670 11 0.282538 1.46715 1.88685 16 0.282514 1.46715 1.88674 1.46718 1.88676 11 0.282571 1.46712 1.88657 13 0.282504 15 1.46699 1.88612 7 0.282414 14 1.46717 1.88678 11 0.282551 0.00005 0.00025 14 1.46717 1.88687 10 0.282550	0.282449 0.282358 0.000093 0.282512 0.282533 0.282507 0.282485 0.282562 0.282494 0.282409 0.282543 0.000042 0.282540	-4.9 1.2 1.51 -8.2 1.1 1.69 3.3 -3.0 0.9 1.40 -2.3 0.9 1.36 -3.0 1.0 1.40 -3.8 1.45 -1.1 0.9 1.30 -3.5 0.9 1.43 -6.4 1.3 1.59 -1.9 0.9 1.34 1.5 -1.8 1.0 1.34
	a value of 0.0113 for the average continental crust (second stage), a135 0.0267 57 0.00081 17 a153 0.0228 15 0.00069 4 a337 0.0448 26 0.00152 9 a361 0.0325 45 0.00107 14	1.46704 1.46705 1.46713 1.46711	1.88599 1.88626 1.88646 1.88670	8 6 14 13	0.282389 0.282433 0.282520 0.282524	0.282384 0.282429 0.282511 0.282518	-7.2 1.5 1.64 -5.5 1.3 1.55 -3.0 0.9 1.40 -2.6 0.8 1.38
	and a juvenile crust (NC) 176 Lu/ 177 Lu and 176 Hf/ 177 Hf of 0.0384 and 0.28314, respectively. a136 0.0266 64 0.00085 18 1.46702 1.88556 a155 0.0206 11 0.00061 3 1.46698 1.88620 a338 0.0422 66 0.00140 21 1.46709 1.88642 Monzodiorite SGC-12-42 a363 0.0357 15 0.00119 3 1.46710 1.88655	8 6 14 14	0.282372 0.282394 0.282516 0.282523	0.282367 0.282390 0.282508 0.282516	-7.9 1.5 1.67 -6.9 1.4 1.63 -3.1 1.1 1.41 -2.7 0.9 1.39
	a140 a156 a339 a301 a364		0.0248 0.0127 0.0180 0.0562 0.0380	29 12 14 12 33	0.00077 0.00039 0.00063 0.00172 0.00121		9 4 4 3 9	1.46704 1.46711 1.46717 1.46716 1.46710	1.88626 1.88630 1.88680 1.88669 1.88677	7 11 12 13 14	0.282430 0.282411 0.282539 0.282511 0.282529	0.282426 0.282408 0.282535 0.282501 0.282522	-5.8 1.2 1.56 -6.2 1.2 1.59 -2.2 1.1 1.35 -3.2 0.9 1.42 -2.5 0.9 1.38
	a143 a158 a339-LR31-NoUPb-1 a303 a365		0.0171 0.0223 0.0430 0.0382 0.0269	43 18 25 40 25	0.00059 0.00068 0.00141 0.00118 0.00090		12 5 8 12 8	1.46708 1.46717 1.46716 1.46716 1.46710	1.88641 1.88661 1.88673 1.88683 1.88665	7 11 13 14 11	0.282430 0.282469 0.282537 0.282486 0.282485	0.282426 0.282465 0.282529 0.282479 0.282480	-5.8 1.2 1.56 -4.2 1.2 1.48 -2.4 0.9 1.36 -4.0 1.1 1.46 -4.0 0.9 1.46
	a144 a159 a339-LR31-NoUPb-2 a304 a366		0.0356 0.0144 0.0472 0.0245 0.0136	62 16 55 18 12	0.00107 0.00045 0.00154 0.00075 0.00053		18 5 14 6 3	1.46713 1.46715 1.46708 1.46715 1.46716	1.88669 1.88663 1.88646 1.88670 1.88679	13 10 13 16 11	0.282491 0.282411 0.282471 0.282455 0.282504	0.282485 0.282409 0.282462 0.282451 0.282501	-3.7 1.1 1.45 -6.2 0.9 1.59 -4.8 1.1 1.49 -5.0 0.8 1.51 -3.2 1.0 1.42
	a138 a161 a343 a305 a367		0.0095 0.0131 0.0469 0.0137 0.0514	13 19 54 18 30	0.00032 0.00040 0.00145 0.00042 0.00166		4 6 12 5 10	1.46710 1.46700 1.46716 1.46714 1.46712	1.88610 1.88601 1.88672 1.88668 1.88665	8 6 11 20 11	0.282397 0.282379 0.282546 0.282445 0.282543	0.282395 0.282377 0.282538 0.282443 0.282533	-6.9 1.3 1.62 -7.3 1.0 1.65 -2.1 1.1 1.35 -5.3 1.0 1.53 -2.1 1.0 1.35
	a130 a162 Mean (n=16) a306 Mean (n=15)		0.0252 0.0137 0.0416 0.0583 0.0379	49 15 85	0.00078 0.00043 0.00138 0.00176 0.00125		13 4 23	1.46699 1.46703 1.46713 1.46713 1.46714	1.88570 1.88581 1.88662 1.88670 1.88670	7 6 13	0.282427 0.282371 0.282490	0.282422 0.282368 0.282521 0.282480 0.282516	-5.9 1.3 1.57 -7.6 1.3 1.67 -2.7 1.38 -4.0 0.9 1.46 -2.7 1.39
	a130-SC1305-NoUPb-1 a167 ±2σ (ext.) a309 ±2σ (ext.)	0.0220 0.0167 0.0366 0.0205 0.0248	59 13 29	0.00067 0.00052 0.00112 0.00063 0.00076		16 4 8	1.46700 1.46706 0.00006 1.46714 0.00007	1.88550 1.88625 0.00026 1.88663 0.00022	8 10 18	0.282341 0.282413 0.282458	0.282338 0.282410 0.000041 0.282454 0.000041	-8.9 2.2 1.73 -6.2 1.0 1.59 1.4 -4.9 0.9 1.51 1.4
	a130-SC1305-NoUPb-2 a168 a311	0.0247 0.0198 0.0318	24 14 16	0.00082 0.00059 0.00097		7 4 5	1.46704 1.46710 1.46714	1.88636 1.88650 1.88679	7 11 14	0.282421 0.282421 0.282462	0.282416 0.282417 0.282456	-6.1 1.1 1.58 -5.9 1.1 1.57 -4.8 0.8 1.50
	a130-SC1305-NoUPb-3 a169 Qz Monzodiorite SC-13-09 a313 Qz Monzodiorite 533 -1	0.0383 0.0150 0.0176	45 14 18	0.00115 0.00046 0.00057		13 4 5	1.46699 1.46705 1.46710	1.88636 1.88613 1.88674	7 12 15	0.282436 0.282382 0.282452	0.282429 0.282380 0.282448	-5.6 1.3 1.55 -7.2 1.0 1.64 -5.1 0.9 1.52
	a130-SC1305-NoUPb-4 a172 a270 a313-sgc12-42-NoUPb-1 a107	0.0270 0.0169 0.0383 0.0085 0.0597	68 6 48 12 65	0.00083 0.00052 0.00118 0.00029 0.00191		20 2 13 4 20	1.46713 1.46703 1.46712 1.46715 1.46709	1.88652 1.88599 1.88693 1.88679 1.88650	8 7 16 17 12	0.282438 0.282344 0.282497 0.282451 0.282521	0.282433 0.282341 0.282490 0.282450 0.282510	-5.5 1.1 1.54 -8.6 1.3 1.72 -3.5 0.9 1.44 -5.1 0.9 1.52 -2.9 1.0 1.40
	Mean (n=14) a174 a271 a313-sgc12-42-NoUPb-3 a110	0.0254 0.0160 0.0529 0.0154 0.0325	21 72 5 66	0.00079 0.00049 0.00161 0.00049 0.00105		6 20 2 21	1.46706 1.46713 1.46719 1.46714 1.46717	1.88617 1.88648 1.88692 1.88664 1.88662	7 14 13 13	0.282423 0.282492 0.282474 0.282501	0.282410 0.282420 0.282482 0.282472 0.282495	-6.3 -5.8 1.4 1.57 1.59 -3.2 1.1 1.44 -4.3 0.9 1.47 -3.4 1.3 1.43
	±2σ (ext.) a174-PRC54-NoUPb-1 a273 a313-sgc12-42-NoUPb-4 a112	0.0139 0.0161 0.0403 0.0123 0.0535	17 32 29 75	0.00039 0.00048 0.00121 0.00041 0.00165		5 9 8 22	0.00011 1.46710 1.46714 1.46713 1.46712	0.00075 1.88623 1.88691 1.88679 1.88649	13 15 17 14	0.282381 0.282510 0.282459 0.282507	0.000077 0.282378 0.282503 0.282457 0.282497	2.7 -7.3 1.2 1.65 -3.1 0.9 1.41 -4.8 0.8 1.50 -3.3 1.2 1.42
	a174-PRC54-NoUPb-3 a277 a313-sgc12-42-NoUPb-5 a113	0.0207 0.0331 0.0297 0.0673	15 24 17 60	0.00061 0.00099 0.00090 0.00215		4 7 5 18	1.46698 1.46711 1.46713 1.46705	1.88574 1.88679 1.88667 1.88649	12 14 16 10	0.282329 0.282505 0.282446 0.282496	0.282325 0.282499 0.282441 0.282483	-9.2 1.1 1.75 -3.2 0.9 1.42 -5.4 0.9 1.53 -3.8 1.0 1.45
	Qz Monzodiorite SC-13-02A a174-PRC54-NoUPb-4 a278 a315 a115	0.0180 0.0256 0.0211 0.0366	13 22 41 25	0.00053 0.00075 0.00068 0.00127		4 6 13 9	1.46710 1.46719 1.46715 1.46708	1.88636 1.88697 1.88661 1.88632	11 17 14 12	0.282408 0.282473 0.282455 0.282467	0.282405 0.282468 0.282451 0.282459	-6.3 0.9 1.60 -4.3 1.0 1.48 -5.0 0.9 1.51 -4.7 1.0 1.50
	a123 Mean (n=15) a279 a317 a116		0.0358 0.0173 0.0358 0.0150 0.0888	9 24 16 96	0.00113 0.00052 0.00107 0.00049 0.00272		2 7 5 28	1.46710 1.46707 1.46711 1.46718 1.46698	1.88653 1.88623 1.88652 1.88679 1.88586	10 14 18 10	0.282391 0.282467 0.282474 0.282490	0.282384 0.282395 0.282461 0.282471 0.282474	-7.3 1.1 1.64 -6.7 1.62 -4.6 0.9 1.49 -4.3 0.9 1.47 -4.2 1.2 1.47
	a125 ±2σ (ext.) a281 Mean (n=14) a117		0.0376 0.0066 0.0393 0.0259 0.0391	18 27 71	0.00120 0.00019 0.00113 0.00080 0.00125		5 8 22	1.46707 0.00012 1.46716 1.46714 1.46715	1.88656 0.00053 1.88687 1.88672 1.88635	9 20 12	0.282352 0.282488 0.282458	0.282345 0.000070 0.282482 0.282461 0.282451	-8.7 1.3 1.72 2.5 -3.8 0.9 1.45 -4.7 1.49 -5.0 0.9 1.51
	a126 a281-sc13-09-NoUPb-1 ±2σ (ext.) a118		0.0712 0.0609 0.0312 0.0339	52 74 36	0.00212 0.00178 0.00093 0.00109		15 21 11	1.46719 1.46720 0.00004 1.46711	1.88697 1.88669 0.00014 1.88637	10 14 12	0.282483 0.282512 0.282471	0.282471 0.282502 0.000034 0.282465	-4.2 1.3 1.47 -3.1 0.9 1.41 1.2 -4.5 1.0 1.49
	a127 Diorite LR-32 a288 a119		0.0584 0.0418 0.0528	27 37 189	0.00183 0.00126 0.00158		7 10 55	1.46712 1.46713 1.46717	1.88671 1.88658 1.88687	16 18 11	0.282439 0.282483 0.282507	0.282429 0.282475 0.282498	-5.7 1.0 1.55 -4.1 1.0 1.46 -3.3 0.9 1.42
	a127-SC1302A-NoUPb-1 a208 a290 Monzodiorite SGC-12-26 a119b	0.0222 0.0562 0.0389 0.0846	24 99 21 143	0.00058 0.00189 0.00113 0.00258		6 32 6 44	1.46711 1.46715 1.46709 1.46710	1.88667 1.88678 1.88652 1.88633	21 7 18 13	0.282439 0.282533 0.282474 0.282482	0.282436 0.282523 0.282467 0.282467	-5.4 1.7 1.54 -2.6 1.0 1.38 -4.4 0.9 1.48 -4.4 1.1 1.48
	a127-SC1302A-NoUPb-2 a210 a292 a373 a122	0.0265 0.0096 0.0249 0.0432 0.0492	7 11 22 58 64	0.00079 0.00041 0.00075 0.00150 0.00156		2 4 6 19 18	1.46711 1.46714 1.46715 1.46716 1.46704	1.88652 1.88663 1.88693 1.88661 1.88639	15 7 21 12 12	0.282426 0.282507 0.282507 0.282505 0.282446	0.282421 0.282505 0.282503 0.282496 0.282437	-5.9 1.0 1.57 -3.2 1.0 1.41 -3.1 0.8 1.41 -3.4 0.9 1.43 -5.4 1.1 1.54
	Mean (n=6) a211 a294 a375 Mean (n=11)		0.0420 0.0874 0.0448 0.0222 0.0544	27 38 39	0.00128 0.00299 0.00131 0.00079 0.00171		9 10 12	1.46712 1.46707 1.46710 1.46718 1.46710	1.88666 1.88668 1.88661 1.88674 1.88642	7 16 12	0.282576 0.282466 0.282487	0.282414 0.282559 0.282458 0.282483 0.282476	-6.2 -1.3 1.0 1.31 1.58 -4.7 0.9 1.50 -3.9 0.9 1.45 -4.1 1.46
	±2σ (ext.) a212 a295 a377 ±2σ (ext.)		0.0380 0.0583 0.0571 0.0359 0.0389	58 18 79	0.00119 0.00198 0.00165 0.00121 0.00114		20 5 25	0.00008 1.46710 1.46713 1.46715 0.00011	0.00034 1.88632 1.88674 1.88669 0.00049	10 18 13	0.282494 0.282502 0.282500	0.000088 0.282483 0.282493 0.282493 0.000045	3.1 -4.0 1.0 1.45 -3.4 0.9 1.43 -3.5 1.0 1.43 1.6
	a214 a298 a378		0.0746 0.0529 0.1035	17 27 58	0.00247 0.00155 0.00339		5 7 19	1.46702 1.46717 1.46716	1.88619 1.88662 1.88676	9 14 12	0.282492 0.282515 0.282541	0.282478 0.282506 0.282522	-4.2 1.2 1.46 -3.0 0.9 1.41 -2.5 0.9 1.38
	Qz Syenite PRC-53 a215 a299 a379		0.0769 0.0323 0.0227	18 73 35	0.00230 0.00096 0.00077		9 20 11	1.46717 1.46718 1.46712	1.88673 1.88672 1.88680	8 24 12	0.282549 0.282464 0.282516	0.282536 0.282459 0.282512	-2.1 1.0 1.35 -4.6 1.1 1.50 -2.9 1.0 1.40
	a79 a217 a300 a380 (a) 176 Yb/ 177 Hf = ( 176 Yb/ 173 Yb) true x ( 173 Yb/ 177 Hf) meas x (M 173(Yb) /M 177(Hf) ) b(Hf) , b(Hf) = ln( 179 Hf/ 177 Hf true / 179 Hf/ 177 Hf measured )/ ln (M 179(Hf )/M 177(Hf) ), M=mass of 0.0243 22 0.00072 6 1.46721 1.88665 11 0.282471 0.282467 -4.2 1.4 1.48 0.0272 52 0.00095 17 1.46709 1.88637 9 0.282501 0.282495 -3.5 1.0 1.43 0.0549 16 0.00160 4 1.46712 1.88670 15 0.282488 0.282478 -3.9 0.8 1.46 0.0709 17 0.00235 5 1.46715 1.88667 12 0.282538 0.282525 -2.4 0.9 1.37
	a84 a218 Mean (n=16) a381 respective isotope. The	0.0147 0.0234 0.0421 0.0179 177 Hf were calculated in a similar way by using the 10 0.00044 2 1.46707 39 0.00080 12 1.46707 0.00124 1.46714 15 0.00074 4 1.46708 176 Lu/	1.88615 1.88642 1.88675 1.88678 175 Lu/ 177 Hf and b(Yb). 14 9 11	0.282394 0.282485 0.282489	0.282391 0.282481 0.282483 0.282485	-6.8 1.1 1.62 -4.1 1.0 1.46 -3.8 1.45 -3.8 0.9 1.45
	a84-prc53-NoUPb-1 a84-prc53-NoUPb-2 a84-prc53-NoUPb-3 a219 a220 a221 (b) Mean Hf signal in volt. ±2σ (ext.) a388 a390 (c) 176 Lu/ 177 Hf = 0.0336, and Qz Monzodiorite SGC-12-39 176 Hf/ 0.0189 0.0150 0.0157 0.0788 0.0458 0.0258 0.0219 0.0591 0.0346 177 Hf = 0.282785 (Bouvier et al ., 2008). 12 0.00056 4 11 0.00044 3 9 0.00049 3 18 0.00271 6 35 0.00158 11 24 0.00096 9 0.00063 44 0.00201 15 61 0.00119 18 a392 0.0340 27 0.00123 9 (d) two stage model age in billion years using the measured 176 Lu/ 177 Lu of each spot (first stage = age of zircon), a value of 0.0113 for the average continental 1.46712 1.88644 12 0.282452 0.282448 -4.8 1.0 1.51 1.46713 1.88655 14 0.282462 0.282459 -4.4 1.2 1.49 1.46710 1.88636 15 0.282404 0.282402 -6.5 1.1 1.60 1.46716 1.88669 7 0.282555 0.282539 -2.0 1.0 1.34 1.46701 1.88629 4 0.282487 0.282478 -4.2 1.2 1.46 1.46707 1.88631 4 0.282512 0.282507 -3.1 1.6 1.41 0.00007 0.00031 0.000034 1.2 1.46709 1.88663 13 0.282518 0.282507 -3.0 0.9 1.41 1.46715 1.88657 13 0.282503 0.282496 -3.4 0.9 1.43 1.46714 1.88668 12 0.282488 0.282481 -3.9 0.9 1.45
	a84-prc53-NoUPb-4 a223 a255 a395 crust (second stage), and a juvenile crust (NC) 0.0220 13 0.1707 242 0.0323 28 0.0475 16	0.00064 0.00401 0.00096 0.00161 176 Lu/ 177 Lu and	4 51 8 4 176 Hf/ 177 Hf of 0.0384 and 0.28325, respectively. 1.46712 1.88645 14 0.282443 1.46698 1.88634 9 0.282539 1.46715 1.88678 14 0.282493 1.46714 1.88681 11 0.282516	0.282439 0.282516 0.282488 0.282507	-5.1 1.0 1.53 -2.8 1.8 1.39 -3.7 0.9 1.44 -3.0 1.0 1.40
	a84-prc53-NoUPb-5 a226 a255-sgc12-39-NoUPb-1 a396	0.0159 0.0199 0.0361 0.0111	7 33 26 12	0.00048 0.00076 0.00106 0.00048		2 11 8 4	1.46714 1.46713 1.46721 1.46713	1.88650 1.88644 1.88698 1.88673	11 8 14 12	0.282410 0.282510 0.282526 0.282511	0.282407 0.282506 0.282520 0.282509	-6.3 0.8 1.59 -3.2 1.1 1.41 -2.6 1.0 1.38 -3.0 0.9 1.40
	a84-prc53-NoUPb-6 a227 a255-sgc12-39-NoUPb-2 a397	0.0172 0.0757 0.0098 0.0850	16 36 9 47	0.00045 0.00256 0.00034 0.00281		4 13 2 14	1.46708 1.46701 1.46714 1.46716	1.88648 1.88603 1.88671 1.88680	14 5 15 11	0.282483 0.282524 0.282473 0.282554	0.282480 0.282509 0.282471 0.282538	-3.7 1.0 1.45 -3.0 1.5 1.40 -4.3 0.9 1.47 -1.9 1.1 1.34
	a85 a227-LR32-NoUPb-1 a255-sgc12-39-NoUPb-3 a398	0.0126 0.0992 0.0206 0.0451	20 23 30 59	0.00038 0.00323 0.00063 0.00154		6 9 9 20	1.46704 1.46703 1.46715 1.46713	1.88612 1.88596 1.88674 1.88677	6 5 15 13	0.282355 0.282491 0.282478 0.282507	0.282353 0.282473 0.282474 0.282498	-8.2 1.3 1.70 -4.3 1.6 1.47 -4.2 0.9 1.47 -3.4 0.9 1.42
	a86 Mean (n=15) a255-sgc12-39-NoUPb-4 a400	0.0170 0.0620 0.0136 0.0418	8 10 48	0.00052 0.00197 0.00043 0.00144		3 3 16	1.46706 1.46708 1.46715 1.46714	1.88606 1.88641 1.88667 1.88662	6 17 13	0.282377 0.282461 0.282494	0.282374 0.282506 0.282459 0.282485	-7.4 1.3 1.66 -3.2 1.41 -4.7 0.9 1.50 -3.8 1.0 1.45
	a87 ±2σ (ext.) a255-sgc12-39-NoUPb-5 Mean (n=15)	0.0149 0.0820 0.0158 0.0450	14 24	0.00042 0.00211 0.00047 0.00154		3 6	1.46696 0.00012 1.46714 1.46714	1.88565 0.00050 1.88677 1.88671	9 16	0.282322 0.282481	0.282319 0.000051 0.282478 0.282502	-9.4 1.1 1.76 1.8 -4.0 0.9 1.46 -3.2 1.41
	a90 a256 ±2σ (ext.)		0.0111 0.0153 0.0511	16 26	0.00035 0.00052 0.00162		5 8	1.46703 1.46711 0.00005	1.88598 1.88636 0.00015	15 6	0.282339 0.282437	0.282337 0.282434 0.000034	-8.7 1.1 1.73 -5.6 1.4 1.55 1.2
	a92 Qz Diorite LR-31 a257		0.0118 0.0217	9 18	0.00037 0.00067		3 5	1.46713 1.46715	1.88664 1.88680	13 14	0.282419 0.282501	0.282417 0.282498	-5.9 1.0 1.57 -3.3 0.9 1.42
	a94 a318 a259 Diorite 533 -2		0.0220 0.0261 0.0286	10 61 13	0.00064 0.00089 0.00087		4 19 4	1.46703 1.46715 1.46711	1.88601 1.88662 1.88675	13 13 13	0.282442 0.282512 0.282515	0.282438 0.282507 0.282510	-5.2 1.1 1.53 -3.2 1.1 1.41 -2.9 0.8 1.40
	a96 a319 a260 a345		0.0142 0.0882 0.0358 0.0438	7 144 58 22	0.00045 0.00270 0.00106 0.00142		2 40 16 7	1.46708 1.46713 1.46712 1.46709	1.88648 1.88652 1.88674 1.88645	11 12 16 14	0.282425 0.282557 0.282474 0.282509	0.282422 0.282541 0.282468 0.282501	-5.7 1.0 1.56 -2.0 1.1 1.34 -4.4 1.1 1.48 -3.2 1.1 1.42
	a97 a319-LR31-NoUPb-1 a261 a346		0.0132 0.0230 0.0210 0.0461	7 31 34 34	0.00039 0.00067 0.00060 0.00154		2 8 10 9	1.46713 1.46710 1.46713 1.46717	1.88654 1.88651 1.88677 1.88673	12 16 21 11	0.282439 0.282507 0.282494 0.282546	0.282436 0.282503 0.282491 0.282537	-5.2 1.1 1.54 -3.3 1.0 1.42 -3.6 1.0 1.44 -1.9 1.0 1.35
	a100 a321 a262 a347		0.0145 0.0626 0.0117 0.0214	16 49 10 9	0.00045 0.00207 0.00039 0.00074		5 14 3 3	1.46709 1.46709 1.46716 1.46717	1.88630 1.88672 1.88678 1.88681	14 10 16 13	0.282385 0.282532 0.282485 0.282511	0.282382 0.282521 0.282483 0.282507	-7.2 1.1 1.64 -2.7 1.1 1.38 -3.8 0.9 1.45 -3.0 1.0 1.40
	a101 a322 a263 a348		0.0193 0.0190 0.0432 0.0294	19 5 24 16	0.00058 0.00076 0.00126 0.00107		5 2 7 5	1.46718 1.46716 1.46717 1.46715	1.88668 1.88680 1.88669 1.88678	10 6 15 13	0.282469 0.282529 0.282504 0.282513	0.282466 0.282524 0.282497 0.282506	-4.2 1.1 1.48 -2.6 1.0 1.37 -3.4 0.9 1.42 -3.0 0.9 1.41
	a323 a265 a351		0.0573 0.0227 0.0292	37 45 34	0.00194 0.00069 0.00095		12 12 11	1.46710 1.46714 1.46717	1.88657 1.88672 1.88670	12 15 11	0.282542 0.282499 0.282522	0.282531 0.282496 0.282516	-2.3 0.9 1.36 -3.4 0.9 1.43 -2.7 0.9 1.39

Couzinié et al., 2016. Supp. Tab. 3: Couzinié et al., 2016. Supplementary

Table 4 :

 4 Zircon in situ SHRIMP O isotope data for standards during the analytical runs

	Session 1
	spot ID	δ	18 O ‰ error (1σ)	18 O/ 16 O	error (1σ)
	91500-1		9.92	0.12	0.00202508	0.00002460
	91500-2		9.57	0.06	0.00202438	0.00001239
	91500-3		9.76	0.08	0.00202478	0.00001714
	91500-4		9.85	0.09	0.00202494	0.00001892
	91500-5		9.77	0.07	0.00202479	0.00001534
	91500-6		9.81	0.06	0.00202487	0.00001323
	91500-7	10.09	0.10	0.00202542	0.00002094
	91500-8		9.54	0.09	0.00202432	0.00001994
	91500-9		9.81	0.07	0.00202487	0.00001515
	91500-10		9.99	0.07	0.00202523	0.00001499
	91500-11	10.30	0.07	0.00202585	0.00001388
	91500-12		9.42	0.13	0.00202410	0.00002860
	statistics on 91500	mean=	9.82	std dev=	0.24
	Session 2
	spot ID	δ 18 O ‰ error (1σ)	18 O/ 16 O	error (1σ)
	91500-1		9.73	0.10	0.00202471	0.00002158
	91500-2		9.94	0.15	0.00202512	0.00002979
	91500-3		9.75	0.11	0.00202475	0.00002369
	91500-4		9.60	0.13	0.00202445	0.00002709
	91500-5		9.93	0.15	0.00202511	0.00002969
	91500-6	10.17	0.12	0.00202559	0.00002473
	91500-7		9.71	0.15	0.00202468	0.00003178
	91500-8		9.72	0.13	0.00202470	0.00002723
	91500-9	10.46	0.15	0.00202618	0.00002850
	91500-10	10.01	0.09	0.00202527	0.00001820
	91500-11		9.78	0.11	0.00202482	0.00002271
	91500-12		9.69	0.10	0.00202462	0.00002105
	91500-13		9.90	0.10	0.00202505	0.00002051
	91500-14		9.95	0.08	0.00202514	0.00001713
	statistics on 91500	mean=	9.84	std dev=	0.23
	Session 3
	spot ID	δ	18 O ‰ error (1σ)	18 O/ 16 O	error (1σ)
	91500-1		9.91	0.11	0.00202507	0.00002206
	91500-2		9.60	0.12	0.00202445	0.00002435
	91500-3		9.96	0.13	0.00202517	0.00002568
	91500-4	10.02	0.08	0.00202529	0.00001540
	91500-5	10.06	0.07	0.00202538	0.00001396
	91500-6	10.16	0.10	0.00202558	0.00002009
	91500-7		9.19	0.11	0.00202363	0.00002359
	91500-8		9.86	0.07	0.00202497	0.00001410
	91500-9		9.73	0.08	0.00202471	0.00001756
	91500-10		9.72	0.09	0.00202469	0.00001957
	statistics on 91500	mean=	9.89	std dev=	0.28

Calibration standard TEMORA 2, measured every 4 unknowns; calibration value delta 18O = 8.2 ‰, standard deviation = 0.39; measured on 42 spots in 23 grains Calibration standard TEMORA 2, measured every 4 unknowns; calibration value delta 18O = 8.2 ‰, standard deviation = 0.38; measured on 28 spots in 20 grains Cross-checking standard, Zircon 91500, delta 18O = 9.86 ± 0.11 ‰ Wiedenbeck et al., 2004 Calibration standard TEMORA 2, measured every 4 unknowns; calibration value delta 18O = 8.2 ‰, standard deviation = 0.41; measured on 20 spots in 20 grains Couzinié et al., 2016. Supplementary Table 5:

  Zircon in situ SHRIMP O isotope data for samples

		δ 18 O ‰	error (1σ)	18 O/ 16 O	error (1σ)	δ 18 O ‰ error (1σ)	18 O/ 16 O	error (1σ)
	Session 1					Monzodiorite SGC-12-42
	Qz Monzodiorite 533 -2				12.1	8.24	0.11	0.00202172	0.00002673
	1.1	6.95	0.10	0.00201913 0.00002953	13.1	8.13	0.09	0.00202151	0.00002179
	3.1	7.31	0.12	0.00201985 0.00003337	14.1	7.67	0.10	0.00202058	0.00002528
	4.1	7.45	0.10	0.00202014 0.00002690	15.1	6.69	0.13	0.00201862	0.00003877
	5.1	7.46	0.11	0.00202015 0.00002993	16.1	7.59	0.08	0.00202041	0.00002124
	6.1	7.62	0.11	0.00202048 0.00002847	Mean (n=16)	7.43
	7.1	7.30	0.10	0.00201983 0.00002793	±2σ (ext.)	1.15
	9.1	8.37	0.10	0.00202199 0.00002327
	10.1	8.51	0.11	0.00202227 0.00002573	Session 2
	10.2	8.42	0.08	0.00202208 0.00002031	Qz Syenite PRC-53
	11.1	8.23	0.11	0.00202171 0.00002780	1.1	8.02	0.16	0.00202128	0.00003925
	14.1	8.38	0.12	0.00202200 0.00002793	2.1	8.58	0.14	0.00202241	0.00003258
	15.1	7.76	0.10	0.00202076 0.00002732	3.1	7.82	0.15	0.00202088	0.00003899
	16.1	8.50	0.11	0.00202224 0.00002610	4.1	8.13	0.18	0.00202149	0.00004497
	17.1	7.81	0.10	0.00202085 0.00002502	5.1	7.92	0.13	0.00202108	0.00003339
	18.1	7.64	0.12	0.00202053 0.00003199	6.1	8.04	0.14	0.00202132	0.00003405
	19.1	7.95	0.09	0.00202113 0.00002377	7.1	7.98	0.15	0.00202121	0.00003769
	Mean (n=16)	7.85				8.1	7.83	0.14	0.00202089	0.00003641
	±2σ (ext.)	1.00				9.1	7.76	0.16	0.00202076	0.00004097
						10.1	8.80	0.13	0.00202284	0.00002944
	Qz Diorite LR-31					11.1	7.69	0.14	0.00202063	0.00003761
	3.1	7.73	0.09	0.00202070 0.00002391	12.1	8.30	0.13	0.00202184	0.00003149
	4.1	7.75	0.10	0.00202074 0.00002629	13.1	8.08	0.13	0.00202141	0.00003306
	5.1	7.57	0.12	0.00202039 0.00003092	14.1	8.92	0.13	0.00202309	0.00002984
	7.1	8.69	0.11	0.00202262 0.00002449	16.1	9.23	0.15	0.00202370	0.00003288
	9.1	8.01	0.10	0.00202126 0.00002436	17.1	7.94	0.12	0.00202111	0.00002942
	10.1	8.07	0.11	0.00202139 0.00002769	18.1	8.13	0.13	0.00202149	0.00003239
	11.1	7.92	0.10	0.00202107 0.00002568	19.1	8.80	0.14	0.00202285	0.00003183
	12.1	8.08	0.09	0.00202140 0.00002353	20.1	8.34	0.14	0.00202192	0.00003450
	13.1	7.45	0.10	0.00202015 0.00002598	21.1	7.92	0.13	0.00202107	0.00003229
	14.1	7.39	0.11	0.00202001 0.00002988	Mean (n=20)	8.21
	15.1	7.31	0.09	0.00201985 0.00002518	±2σ (ext.)	0.87
	Mean (n=11)	7.81
	±2σ (ext.)	0.80				Qz Monzonite PRC-54
						1.1	9.59	0.10	0.00202444	0.00002205
	Qz Monzodiorite SC-13-09				2.1	9.39	0.14	0.00202404	0.00003012
	1.1	7.81	0.13	0.00202087 0.00003430	3.1	8.41	0.13	0.00202206	0.00003211
	2.1	7.81	0.10	0.00202086 0.00002698	3.2	7.99	0.14	0.00202121	0.00003653
	3.1	8.39	0.12	0.00202203 0.00002935	4.1	7.73	0.12	0.00202071	0.00003092
	4.1	8.91	0.08	0.00202307 0.00001867	5.1	7.78	0.15	0.00202080	0.00004019
	6.1	8.32	0.11	0.00202189 0.00002662	6.1	7.37	0.14	0.00201997	0.00003842
	7.1	8.05	0.09	0.00202135 0.00002191	7.1	6.86	0.13	0.00201896	0.00003736
	8.1	8.11	0.09	0.00202147 0.00002171	8.1	8.25	0.13	0.00202175	0.00003146
	9.1	8.25	0.09	0.00202173 0.00002174	9.1	8.54	0.14	0.00202232	0.00003348
	10.1	7.75	0.10	0.00202074 0.00002642	10.1	7.28	0.12	0.00201979	0.00003417
	12.1	8.08	0.11	0.00202141 0.00002674	11.1	7.41	0.10	0.00202006	0.00002702
	13.1	8.00	0.12	0.00202124 0.00002977	13.1	8.44	0.09	0.00202212	0.00002040
	14.1	7.92	0.10	0.00202107 0.00002549	14.1	8.21	0.11	0.00202166	0.00002765
	15.1	8.09	0.11	0.00202142 0.00002765	15.1	9.28	0.12	0.00202381	0.00002610
	16.1	8.01	0.09	0.00202125 0.00002199	16.1	7.97	0.12	0.00202119	0.00003013
	18.1	8.03	0.11	0.00202129 0.00002743	17.1	9.97	0.12	0.00202520	0.00002535
	Mean (n=15)	8.10				Mean (n=17)	8.26
	±2σ (ext.)	0.58				±2σ (ext.)	1.75
	Monzodiorite SGC-12-42				Qz Monzodiorite 533 -1
	1.1	7.67	0.11	0.00202057 0.00002796	1.1	8.11	0.14	0.00202146	0.00003541
	2.1	8.22	0.11	0.00202168 0.00002695	2.1	8.80	0.13	0.00202285	0.00002888
	3.1	6.41	0.09	0.00201806 0.00002971	3.1	8.43	0.18	0.00202211	0.00004311
	4.1	6.87	0.10	0.00201898 0.00003041	4.1	7.75	0.14	0.00202075	0.00003696
	5.1	7.15	0.10	0.00201953 0.00002862	5.1	7.72	0.15	0.00202067	0.00003997
	5.2	7.02	0.09	0.00201928 0.00002585	7.1	8.21	0.09	0.00202166	0.00002231
	7.1	8.04	0.11	0.00202131 0.00002669	8.1	7.94	0.11	0.00202112	0.00002892
	8.1	7.80	0.11	0.00202085 0.00002768	9.1	7.62	0.12	0.00202048	0.00003208
	9.1	7.18	0.11	0.00201960 0.00003039	11.1	8.37	0.16	0.00202197	0.00003809
	10.1	6.89	0.12	0.00201901 0.00003500	12.1	7.68	0.16	0.00202061	0.00004301
	11.1	7.27	0.10	0.00201978 0.00002823	13.1	7.81	0.14	0.00202086	0.00003732

Couzinié et al., 2016. Supplementary Table 5 (continued):

	Zircon in situ SHRIMP O isotope data for samples
	δ	18 O ‰	error (1σ)	18 O/ 16 O	error (1σ)
	Qz Monzodiorite 533 -1
	14.1	6.87	0.14	0.00201898 0.00003987
	15.1	6.62	0.11	0.00201848 0.00003355
	Mean (n=13)	7.84
	±2σ (ext.)	1.19
	Session 3
	Monzodiorite SGC-12-26
	1.1	6.46	0.10	0.00201815 0.00003044
	2.1	6.85	0.12	0.00201893 0.00003444
	3.1	6.92	0.11	0.00201908 0.00003203
	4.1	6.93	0.11	0.00201909 0.00003322
	5.1	7.05	0.11	0.00201933 0.00003269
	6.1	8.01	0.10	0.00202126 0.00002625
	7.1	7.20	0.10	0.00201965 0.00002933
	8.1	7.68	0.10	0.00202060 0.00002640
	9.1	7.84	0.10	0.00202092 0.00002566
	10.1	7.72	0.10	0.00202068 0.00002695
	11.1	7.57	0.16	0.00202037 0.00004284
	12.1	7.46	0.12	0.00202017 0.00003296
	13.1	7.25	0.09	0.00201973 0.00002540
	14.1	6.39	0.16	0.00201801 0.00005138
	15.1	7.57	0.07	0.00202039 0.00001931
	16.1	7.37	0.08	0.00201997 0.00002172
	17.1	7.86	0.07	0.00202097 0.00001714
	18.1	7.62	0.09	0.00202048 0.00002295
	19.1	8.02	0.11	0.00202128 0.00002712
	20.1	7.04	0.08	0.00201931 0.00002311
	21.1	7.54	0.08	0.00202031 0.00002116
	22.1	6.84	0.09	0.00201891 0.00002669
	23.1	7.20	0.09	0.00201964 0.00002491
	Mean (n=23)	7.32
	±2σ (ext.)	0.92

Table 1 :

 1 New whole-rock major and trace elements data obtained on the Velay Orthogneiss Formation. Leucogneiss Augen gneiss Leucogneiss Banded gneiss Augen gneiss Banded gneiss Banded gneiss Banded gneiss Leucogneiss Banded gneiss Augen gneiss

	SC14 13	Vivarais	45.22961	4.40612	AUGEN	76.1	13.5	1.82	0.03	0.08	0.42	3.44	4.26	0.07	0.35	0.87
	SC14 12	Vivarais	45.12458	4.54009	OG	77.1	12.3	2.19	0.02	0.18	0.48	2.54	4.86	0.12	0.24	0.66
	SC14 11	Vivarais	45.12503	4.54082	LEPT	77	12.8	1.69	0.02	0.08	0.39	2.68	5.56	0.07	0.26	0.67
	SC14 10	Vivarais	45.07805	4.44173	OG	76.5	12.8	2.25	0.02	0.19	0.59	2.67	5.49	0.14	0.24	0.59
	SC14 09	Vivarais	45.03204	4.49436	OG	72	14.5	2.65	0.04	0.52	1.18	4.27	3.96	0.27	0.31	0.51
	SC14 08	Vivarais	45.03204	4.49436	OG	73.7	14.5	2.1	0.03	0.44	0.99	3.91	4.24	0.23	0.27	0.57
	SC14 07	Vivarais	45.02800	4.49277	AUGEN	77.2	11.9	1.83	0.02	0.15	0.43	2.38	5.48	0.11	0.21	0.42
	SC14 06	Vivarais	45.02800	4.49277	OG	77.4	12.25	2.06	0.02	0.18	0.49	2.87	4.67	0.13	0.19	0.53
	PG3	Pilat	45.41059	4.53977	LEPT	74.2	12.8	2.05	0.02	0.26	0.56	3.05	4.79	0.13	0.29	0.69
	OSZ	Pilat	45.41724	4.53230	AUGEN	69.9	14.55	2.73	0.03	0.67	1.02	3.05	5.02	0.3	0.24	0.89
	MM12	Pilat	45.41075	4.53991	LEPT	74.8	12.65	2.01	0.03	0.22	0.53	2.87	4.55	0.12	0.25	0.85
	Sample MM06 MM09 MM10 MM11	Area Arc de Fix Arc de Fix Arc de Fix Arc de Fix	Lat. N 44.98811 44.69490 44.56838 44.60534	Long. E 3.68093 3.88376 3.87095 4.07040	Type Augen gneiss Leucogneiss Leucogneiss Augen gneiss Code LEPT LEPT AUGEN AUGEN	SiO 2 76.5 75.1 71.3 73.3	Al 2 O 3 12.9 13.15 14.8 13.1	Fe 2 O 3 1.93 1.68 3.08 1.76	MnO 0.03 0.02 0.04 0.02	MgO 0.11 0.09 0.84 0.21	CaO 0.32 0.42 1.08 0.56	Na 2 O 2.39 3.01 2.79 2.85	K 2 O 5.42 4.93 4.36 5	TiO 2 0.04 0.06 0.37 0.18	P 2 O 5 0.2 0.27 0.23 0.19	LOI 0.55 0.79 1.39 0.79	Ag <0.5

Couzinié et al., 2017. Supplementary

  New whole-rock major and trace elements data obtained on the Velay Orthogneiss Formation. Type Banded gneiss Leucogneiss Banded gneiss Augen gneiss Augen gneiss Augen gneiss Augen gneiss Augen gneiss Augen gneiss Leucogneiss Augen gneiss Leucogneiss Augen gneiss Augen gneiss Augen gneiss

	SC14 38	Arc de Fix	44.53111	3.88741	AUGEN	71.4	13.85	3.61	0.05	0.97	1.16	2.9	4.27	0.39	0.2	1.05	2.39	0.91	0.14	25.4	1.82	2.6	<0.005	0.34	0.054	3.9	70	0.08	15.3	4.3	2	10	1.15	322	<0.001	<0.05	2	0.4	1.71	7	10.2	1.8	0.39	<0.01	4.37	1.4	0.14	14	<5	1	11.8	0.73	73
	SC14 37	Arc de Fix	44.56838	3.87095	AUGEN	70.8	14.1	2.61	0.03	0.58	0.45	2.7	5.53	0.29	0.26	1.27	4.18	1.97	0.18	20.3	2.93	2.8	0.011	0.75	0.108	8.9	70	0.19	13.6	9.6	1	18	2.28	293	<0.001	<0.05	2	0.6	2.43	6	26.1	1.3	0.56	<0.01	8.22	1.1	0.26	7.92	6	2	23.4	1.5	70
	SC14 35	Arc de Fix	44.69490	3.88376	AUGEN	75.2	13.5	2	0.02	0.23	0.55	3.06	4.91	0.13	0.22	0.66	2	0.89	0.09	20.5	1.23	2.1	0.006	0.33	0.103	3.4	50	0.08	11.7	3.3	2	10	0.83	282	<0.001	<0.05	2	0.5	1.08	6	11.4	1	0.28	<0.01	5.28	1.4	0.11	7.3	<5	1	12.1	0.73	46
	SC14 34	Arc de Fix	44.69490	3.88376	LEPT	75.6	12.95	1.72	0.03	0.11	0.38	2.59	5.64	0.04	0.2	0.5	5.38	3.13	0.29	18.7	3.65	3.6	0.01	0.99	0.059	12.1	40	0.35	10	12.7	2	19	3.13	244	<0.001	<0.05	2	<0.2	3.36	5	36.6	0.7	0.75	<0.01	9.15	1.1	0.46	4.22	8	1	31	2.68	48
	SC14 33	Arc de Fix	44.76386	3.88516	AUGEN	72.8	14.95	2.25	0.03	0.4	0.76	3.13	5.54	0.19	0.24	0.83	2.99	1.32	0.88	21.2	4.12	5.6	0.016	0.52	0.088	32.2	60	0.16	13.9	28.8	3	38	7.22	278	<0.001	<0.05	4	0.2	5.78	16	187.5	1.9	0.59	<0.01	21.4	1.5	0.18	6.37	16	2	14.3	1.32	73
	SC14 32	Arc de Fix	44.76386	3.88516	LEPT	75.4	12.5	2.17	0.02	0.19	0.35	1.88	6.65	0.13	0.25	0.56	2.48	0.82	0.57	22.9	3.38	3.9	<0.005	0.33	0.115	25.6	70	0.07	11.1	22.7	4	30	5.87	281	<0.001	<0.05	3	0.3	4.59	8	134.5	1	0.49	<0.01	15.2	1.3	0.1	5.89	10	2	10.2	0.52	74
	SC14 31	Arc de Fix	44.94692	3.68603	AUGEN	72.8	13.45	2.61	0.03	0.51	0.91	2.79	4.69	0.26	0.2	0.75	3.56	1.99	0.17	16.9	2.31	2.8	<0.005	0.64	0.081	7.7	30	0.17	8	7.8	1	18	2.14	254	<0.001	<0.05	2	0.3	2.37	5	24.1	0.6	0.49	<0.01	6.31	1.1	0.25	4.96	6	<1	22	1.62	45
	SC14 30	Arc de Fix	44.95867	3.70022	AUGEN	71.6	14.6	3.18	0.04	0.81	1.18	3.2	4.27	0.35	0.25	1.06	4.14	2.26	0.16	17.5	2.68	2.7	0.007	0.79	0.093	9	40	0.2	11.2	8.3	<1	19	2.26	241	<0.001	<0.05	2	0.3	2.4	6	22.2	0.7	0.54	<0.01	7.7	1.2	0.33	4.81	7	1	24.1	1.76	59
	SC14 28	Arc de Fix	44.98793	3.68103	AUGEN	73.6	13.75	2.03	0.03	0.26	0.53	3.08	5.02	0.19	0.21	0.94	3.42	1.46	0.36	18.4	3.09	2.8	<0.005	0.61		11.1	50	0.15	11.1	11.3	1	20	2.87	260		<0.05	2	0.3	3.05	9	38.6	1.5	0.64	0.01	7.02	1	0.23	6.69	9	<1	20.4	0.78	54
	SC14 27	Arc de Fix	45.20795	3.61540	AUGEN	73.7	13.9	2.49	0.03	0.46	0.74	3.08	4.81	0.24	0.22	0.84	4.8	3.44	0.84	20.1	6.31	3.8	<0.005	1.19		27.3	60	0.42	10.7	25.3	4	24	6.64	167		<0.05	4	<0.2	6.01	8	125	1.2	1.06	<0.01	11	0.6	0.5	2.31	28	<1	27.9	2.59	63
	SC14 25	Arc de Fix	45.26191	3.65904	AUGEN	72.7	13.7	2.02	0.03	0.35	0.71	3	4.68	0.18	0.14	1	3.22	1.4	0.26	18.7	2.52	2.9	0.01	0.54	0.047	7.9	60	0.11	10.9	8.2	2	18	2.05	237	0.001	<0.05	2	0.6	2.32	7	28.6	1.3	0.48	<0.01	6.09	1.1	0.2	8.44	7	1	18	1	41
	SC14 22	Vivarais	45.30632	4.65525	LEPT	77.6	12.45	1.42	0.02	0.13	0.38	2.56	4.65	0.11	0.22	1.45	5.54	3.19	0.94	17.9	5.84	4.6	0.006	1.07	0.07	25.8	60	0.38	9.3	27.2	11	20	6.47	151.5	<0.001	0.05	5	0.9	5.66	6	110.5	1	0.87	<0.01	10.2	0.7	0.43	3.03	30	2	31	2.97	33
	SC14 21	Vivarais	45.40639	4.65522	OG	76.9	12.45	1.68	0.02	0.13	0.44	2.89	4.57	0.11	0.23	0.87	2.88	1.51	0.13	21.7	1.71	2.6	0.02	0.47	0.04	4.5	20	0.14	10.6	5.1	1	20	1.36	251	<0.001	1.4	3	<0.2	1.49	9	19.7	1.5	0.4	<0.01	4.58	1.6	0.19	10.4	<5	4	15.4	1.3	33
	SC14 16	Vivarais	45.29857	4.64510	LEPT	76.9	13.05	1.77	0.02	0.07	0.41	3.38	4.6	0.06	0.35	0.56		0.92	0.15	21	1.19	2	<0.005	0.35	0.009	5.6	10	0.09	4	4.4	<1	19	1.18	213	<0.001	<0.05	1	<0.2	1.23	6	17.2	0.7	0.27	<0.01	4.16	1.1	0.13	2.29	<5	4	11.2	0.79	46
	SC14 14	Vivarais	45.20891	4.49379	OG	77.5	12.2	1.8	0.03	0.13	0.42	2.86	4.42	0.09	0.21	0.75	<0.5	2	0.56	16.2	3.93	3.6	<0.005	0.77	0.046	15.7	30	0.21	7.9	15.5	3	25	4.02	170.5	<0.001	0.05	2	0.6	4.35	4	64.5	0.8	0.7	<0.01	8.53	0.9	0.3	3.2	12	1	23.5	1.86	58
	Sample	Area	Lat. N	Long. E	Code	SiO 2	Al 2 O 3	Fe 2 O 3	MnO	MgO	CaO	Na 2 O	K 2 O	TiO 2	P 2 O 5	LOI	Ag	Er	Eu	Ga	Gd	Hf	Hg	Ho	In	La	Li	Lu	Nb	Nd	Ni	Pb	Pr	Rb	Re	Sb	Sc	Se	Sm	Sn	Sr	Ta	Tb	Te	Th	Tl	Tm	U	V	W	Y	Yb	Zn

Zr

Couzinié et al., 2017. Supplementary Table 1 (continued):

  New whole-rock major and trace elements data obtained on the Velay Orthogneiss Formation.

																			5.34	2.72	0.95	21.2	5.39	4.2	0.006	0.99	0.044	24.4	90	0.4	13.5	24.9	12	16	6.2	229	<0.001	<0.05	6	<0.2	4.99	7	101	1.4	0.75	<0.01	10.5	1.2	0.38	3.87	40	5	28.8	2.3	66
																			6.12	3.77	0.82	19.2	5.22	3.8	0.017	1.23	0.04	26.2	30	0.5	9.9	25.8	6	30	6.8	211	<0.001	0.74	4	0.4	6.14	7	98.1	1.2	0.98	0.01	8.93	1	0.56	5.02	18	2	39.7	3.46	46
																			3.18	1.68	0.35	22.2	2.15	2.3	0.006	0.55	0.028	11.1	30	0.13	9.5	10.3	2	19	2.98	217	<0.001	<0.05	2	<0.2	2.29	6	45.7	1.1	0.41	0.01	6.63	0.9	0.2	4.53	6	4	18.1	1.12	45
																			3.04	1.87	0.22	19	1.6	2.1	<0.005	0.57	0.022	6.2	30	0.19	3.9	5.4	1	19	1.52	224	<0.001	<0.05	2	0.3	1.61	5	34.4	0.7	0.38	<0.01	4.25	0.9	0.25	3.83	<5	4	18.6	1.77	32
																			5	2.75	0.82	18.8	3.9	3.6	<0.005	0.95	0.02	17.1	50	0.27	8.4	16.4	4	26	4.22	184	<0.001	<0.05	3	0.3	4.22	6	87.4	1.1	0.78	<0.01	7.99	0.7	0.35	4.25	13	3	26.9	2.46	35
																			6.57	3.49	0.29	13.8	4.64	5.2	0.008	1.26	0.042	12.1	30	0.23	8.1	12.5	2	30	3.17	224	<0.001	<0.05	2	0.3	3.54	4	38	0.7	0.96	0.01	9.86	1.1	0.42	3.47	<5	1	40.6	2.29	40
																			6.04	4.06	0.89	17.4	5.01	4.4	<0.005	1.12	0.033	22.9	40	0.46	7.9	23.2	6	24	5.84	137.5	<0.001	<0.05	4	0.6	5.19	3	100	0.7	0.88	0.01	10.7	0.5	0.61	2.11	20	1	35.2	3.56	48
																			7.38	3.45	1.03	18.6	7.6	5.8	<0.005	1.3	0.047	25.4	70	0.42	10.5	29.6	7	27	6.88	140.5	<0.001	0.09	4	<0.2	6.93	4	125	0.8	1.26	0.01	10.2	0.6	0.42	2.7	26	1	39	3.07	50
																			3.88	1.74	0.57	18.5	3.97	3.3	0.02	0.63	0.023	17.6	50	0.13	9.3	17	4	32	4.4	207	<0.001	0.08	2	<0.2	3.84	7	60.3	1	0.67	0.01	8.62	1	0.2	4.03	12	2	19.4	1.27	51
																			6.08	3.27	0.72	17	5.21	4.6	0.01	1.06	0.051	22.5	80	0.37	9.4	23.4	4	24	5.7	176	0.001	<0.05	3	<0.2	5.58	5	93.1	0.9	0.87	0.01	10.9	0.7	0.45	3.03	15	1	31.3	2.84	42
	SC14 49	Arc de Fix	44.55854	4.19263	Leucogneiss	LEPT	77.4	12.7	1.97	0.04	0.17	0.4	3.04	4.54	0.08	0.22	0.3		6.61	4.5	0.57	17	4.89	3.9	0.006	1.28	0.041	21.2	40	0.48	10.2	20.7	4	32	5.5	148	<0.001	0.05	3	0.4	5.57	6	83.5	0.9	0.88	<0.01	10.4	0.7	0.6	4.85	13	1	39.1	3.71	41
	SC14 42 SC14 45 SC14 47 SC14 48	Arc de Fix Arc de Fix Arc de Fix Arc de Fix	44.61961 44.61692 44.60534 44.55854	4.00833 4.01186 4.07040 4.19263	Leucogneiss Augen gneiss Augen gneiss Leucogneiss	AUGEN AUGEN LEPT LEPT	69.9 69.4 77.3 78	14.25 15.5 12.55 12.95	3.41 2.99 2.14 1.38	0.05 0.04 0.05 0.01	1.14 0.8 0.15 0.35	1.16 1.23 0.36 0.51	2.98 2.93 3.2 3.94	4.63 5.43 4.86 2.97	0.45 0.35 0.07 0.09	0.24 0.24 0.2 0.24	1.05 0.93 0.19 0.65	<0.5	1.98 3.59 2.37	1.59 0.81 1.87 1.13	0.18 0.05 0.22 0.1	18.1 25.6 19.8 21.9	2.1 1.17 2.61 1.48	2 2.2 3.1 3	<0.005 0.005 0.01 <0.005	0.53 0.36 0.63 0.35	0.066 0.033 0.027 0.047	6.4 3.6 8.7 6.8	60 120 30 30	0.16 0.06 0.16 0.1	10.3 21.3 12 16.4	6.4 3.7 8.8 6.1	3 2 2 1	11 8 9 6	1.63 1.02 2.18 1.58	261 546 267 283	<0.001 <0.001 <0.001 <0.001	<0.05 <0.05 <0.05 <0.05	2 3 2 3	<0.2 <0.2 <0.2 0.2	1.85 1.06 2.24 1.52	5 26 7 8	15.9 23.2 22.3 19.5	1 3.2 1.3 1.6	0.37 0.25 0.54 0.33	<0.01 <0.01 <0.01 <0.01	5.41 5.33 8.88 8.25	1.4 2.3 1.1 1.2	0.21 0.12 0.24 0.16	2.8 12.65 8.54 3.86	7 <5 5 5	<1 9 2 2	16.2 11 20.6 13.1	1.34 0.63 1.55 0.91	37 53 51 32
	Sample	Area	Lat. N	Long. E	Type	Code	SiO 2	Al 2 O 3	Fe 2 O 3	MnO	MgO	CaO	Na 2 O	K 2 O	TiO 2	P 2 O 5	LOI	Ag		Er	Eu	Ga	Gd	Hf	Hg	Ho	In	La	Li	Lu	Nb	Nd	Ni	Pb	Pr	Rb	Re	Sb	Sc	Se	Sm	Sn	Sr	Ta	Tb	Te	Th	Tl	Tm	U	V	W	Y	Yb	Zn

Zr

Couzinié et al., 2017. Supplementary Table 1 (continued):

Table 3 :

 3 Operating conditions for the LA-ICP-MS equipment

	Laboratory & Sample Preparation
	Laboratory name	Géosciences Rennes, UMR CNRS 6118, Rennes, France
	Sample type/mineral	zircon
	Sample preparation	Conventional mineral separation, 1 inch resin mount, 1mm polish to finish
		(BSE) imaging using a Jeol JSM-6400 SEM at the Ecole des Mines de St Etienne (France)
	Imaging	(CL) imaging using a Jeol JSM-5910 SEM at the Laboratoire Magmas et Volcans (Clermont-
		Ferrand, France)
	Laser ablation system
	Make, Model & type	ESI NWR193UC, Excimer
	Ablation cell	ESI NWR TwoVol2
	Laser wavelength	193 nm
	Pulse width	< 5 ns
	Fluence	8.8 J/cm -2
	Repetition rate	3 Hz
	Spot size	20 -35 μm
	Sampling mode / pattern	Single spot
	Carrier gas	100% He, Ar make-up gas and N 2 (3 ml/mn) combined using in-house smoothing device
	Background collection	20 seconds
	Ablation duration	60 seconds
	Wash-out delay	15 seconds
	Cell carrier gas flow (He)	0.75 l/min
	ICP-MS Instrument
	Make, Model & type	Agilent 7700x, Q-ICP-MS
	Sample introduction	Via conventional tubing
	RF power	1350W
	Sampler, skimmer cones	Ni
	Extraction lenses	X type
	Make-up gas flow (Ar)	0.85 l/min
	Detection system	Single collector secondary electron multiplier
	Data acquisition protocol	Time-resolved analysis
	Scanning mode	Peak hopping, one point per peak
	Detector mode	Pulse counting, dead time correction applied, and analog mode when signal intensity > ≈ 10 6 cps
	Masses measured	204 (Hg + Pb),	206 Pb,	207 Pb,	208 Pb,	232 Th,	238 U
	Integration time per peak	10-30 ms
	Sensitivity / Efficiency	20000 cps/ppm Pb (50µm, 10Hz)
	Data Processing
	Gas blank	20 seconds on-peak
	Calibration strategy	GJ1 zircon standard used as primary reference material, 91500 used as secondary reference material (quality control)
	Reference Material info	GJ1 (Jackson et al., 2004) Plešovice (Slama et al., 2008)
	Data processing package used	GLITTER ® (van Achterbergh et al., 2001)
	Quality control / Validation	Plešovice: concordia age = 337.0 ± 1.0 Ma (N=20; MSWD C+E =0.21)

Table 4 :

 4 Results of LA-ICPMS U-Pb analyses of the Plešovice zircon standard The label "concordant" vs. "discordant" for each spot was attributed based on the position of the error ellipse with respect to the Concordia curve. If the ellipse intersects the Concordia, then the spot is "concordant".

	label f				Concordant	Concordant	Concordant	Concordant		Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant		Concordant	Concordant		Concordant	Concordant	Concordant	Concordant
	conc. e	(%)			91	97	102	99		103	102	111	103	98	87	98	110	104	108	103	97		90	104		106	96	107	98
	±2σ	(Ma)			7.0	7.6	7.9	7.9		7.9	7.5	8.3	8.5	7.6	7.8	7.8	9.0	7.7	8.0	7.9	8.4		8.4	8.6		6.9	7.1	7.2	7.5
	207 Pb	235 U			322.2	338.1	336.1	337.9		336.4	336.4	333.4	336.2	336.7	331.3	337.2	332.9	335.9	333.1	336.2	337.7		339.6	335.3		337.5	337.8	334.8	337.9
	Pb a U a Th a 207 Pb b ±2σ 206 Pb c ±2σ ρ d 207 Pb ±2σ 206 Pb ±2σ	(ppm) (ppm) U 235 U 238 U 206 Pb (Ma) 238 U (Ma)	Plešovice	Session #1 (May 11 th , 2015)	4110515 29 604 0.08 0.373 0.009 0.0506 0.0012 0.96 350.3 48.7 318.4 7.5	17110515 26 520 0.08 0.395 0.010 0.0537 0.0013 0.93 345.7 51.4 337.0 8.0	31110515 27 549 0.08 0.392 0.011 0.0536 0.0013 0.90 331.0 53.3 336.8 8.1	41110515 29 577 0.08 0.395 0.011 0.0538 0.0013 0.91 340.1 52.3 337.6 8.2	Session #2 (May 12 th , 2015)	5120515a 31 624 0.09 0.393 0.011 0.0538 0.0014 0.91 327.8 52.1 337.7 8.4	17120515a 34 669 0.10 0.393 0.010 0.0537 0.0014 0.96 329.7 48.5 337.5 8.3	30120515a 32 628 0.10 0.389 0.011 0.0538 0.0014 0.87 304.2 57.0 337.7 8.3	41120515a 30 588 0.10 0.393 0.012 0.0537 0.0014 0.86 328.9 58.6 337.3 8.3	4120515b 32 641 0.09 0.393 0.010 0.0535 0.0013 0.95 341.3 49.9 336.0 8.2	17120515b 31 637 0.09 0.386 0.011 0.0517 0.0013 0.92 375.1 52.5 325.1 8.0	31120515b 33 669 0.10 0.394 0.011 0.0536 0.0014 0.94 344.2 51.2 336.3 8.3	41120515b 32 646 0.09 0.388 0.012 0.0536 0.0014 0.81 306.5 63.5 336.7 8.4	4120515c 31 618 0.09 0.392 0.011 0.0538 0.0013 0.92 323.8 51.8 337.7 8.1	17120515c 31 622 0.09 0.388 0.011 0.0536 0.0013 0.86 311.0 57.0 336.3 8.0	30120515c 30 583 0.09 0.392 0.011 0.0537 0.0013 0.87 327.8 56.0 337.4 7.9	41120515c 32 617 0.10 0.395 0.012 0.0536 0.0013 0.82 345.3 60.5 336.6 7.8	Session #3 (May 13 th , 2015)	4130515 14 281 0.09 0.397 0.023 0.0533 0.0025 0.80 372.6 61.3 334.9 7.6	18130515 16 325 0.09 0.391 0.023 0.0537 0.0025 0.78 323.3 63.6 337.1 7.6	Session #4 (October 19 th , 2015)	4191015 44 853 0.12 0.394 0.009 0.0542 0.0012 0.93 319.9 50.4 340.1 7.3	17191015 36 718 0.11 0.395 0.010 0.0535 0.0012 0.90 349.5 51.7 336.1 7.2	30191015 36 710 0.11 0.391 0.010 0.0538 0.0012 0.87 316.0 53.9 337.6 7.3	41191015 36 719 0.11 0.395 0.010 0.0537 0.0012 0.84 344.0 55.8 337.0 7.3	(a) U and Pb contents (in ppm) and Th/U ratios were calculated relative to GJ-1 reference zircon (U = 280 ppm; Pb = 25.5 ppm).	(b) Pb/ U = Pb/ Pb/( U/ Pb*1/137.88)	(d) ρ (rho) is the correlation coefficient between errors of 206 Pb/ 238 U. Pb/ 235 U and 207	Pb age) × 100 Pb/ 206 U age / 207 Pb/ 238 (e) Degree of concordance = ( 206	(f)

(c) Corrected for background, within-run Pb/U fractionation and subsequently normalized to GJ-1 (ID-TIMS value/measured value).

Couzinié et al., 2017. Supplementary

Table 5 :

 5 Results of LA-ICPMS U-Pb analyses of zircons from the Velay Orthogneiss Formation Corrected for background, within-run Pb/U fractionation and subsequently normalized to GJ-1 (ID-TIMS value/measured value). The label "concordant" vs. "discordant" for each spot was attributed based on the position of the error ellipse with respect to the Concordia curve. If the ellipse intersects the Concordia, then the spot is "concordant".

	label f				Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Normally Discordant	Normally Discordant	Concordant	Normally Discordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Concordant	Normally Discordant	Concordant	Normally Discordant	Normally Discordant	Concordant	Concordant	Normally Discordant			Concordant	Concordant	Concordant
	207 Pb ±2σ 206 Pb ±2σ 207 Pb ±2σ conc. e	206 Pb (Ma) 238 U (Ma) 235 U (Ma) (%)			558.9 49.0 542.8 12.6 545.9 11.0 97	545.9 46.1 534.7 12.4 536.8 10.4 98	688.1 47.2 660.3 15.2 666.6 12.6 96	519.6 49.5 544.3 12.6 539.6 10.9 105	535.2 48.4 541.5 12.6 540.4 10.6 101	563.7 48.2 539.5 12.5 544.1 10.9 96	622.9 45.3 534.0 12.4 551.1 10.6 86	777.7 48.3 542.9 12.7 590.4 11.9 70	576.3 46.0 538.1 12.5 545.4 10.6 93	696.9 45.3 514.5 12.0 549.3 10.7 74	538.6 50.4 542.3 12.7 541.6 11.0 101	554.3 47.9 536.2 12.6 539.6 10.8 97	554.5 49.1 541.3 12.7 543.8 11.1 98	555.8 49.7 542.5 12.8 545.0 11.2 98	550.8 50.7 540.9 12.8 542.8 11.4 98	568.1 52.1 543.5 12.8 548.2 11.7 96	547.0 56.3 542.0 12.9 542.9 12.3 99	570.8 52.0 543.8 12.9 549.0 11.7 95	723.5 48.7 721.4 16.9 721.8 13.9 100	551.5 48.0 509.1 12.1 516.9 10.6 92	543.3 47.6 540.4 12.8 540.9 11.0 99	612.1 60.7 535.8 13.0 550.6 13.4 88	793.2 55.2 544.7 13.1 595.3 13.5 69	553.3 49.9 559.7 13.4 558.4 11.6 101	553.4 56.6 543.8 13.1 545.6 12.5 98	778.6 50.5 542.4 13.0 590.1 12.6 70			549.3 46.4 538.7 13.1 540.7 11.0 98	567.4 48.0 541.0 13.2 546.0 11.4 95	534.0 50.1 546.0 13.3 543.7 11.4 102
	Pb a U a Th a 207 Pb b ±2σ 206 Pb c ±2σ ρ d	(ppm) (ppm) U 235 U 238 U	Arc-de-Fix augen gneiss MM06 -S t Privat-d'Allier	Session #1 (May 11 th , 2015)	z1* 17 205 0.08 0.712 0.019 0.0879 0.0021 0.93	z2* 57 698 0.05 0.697 0.017 0.0865 0.0021 0.97	z3 24 206 0.46 0.928 0.024 0.1079 0.0026 0.94	z4* 17 198 0.09 0.701 0.018 0.0881 0.0021 0.94	z5* 30 363 0.05 0.703 0.018 0.0876 0.0021 0.95	z6* 24 290 0.06 0.709 0.018 0.0873 0.0021 0.94	z7b 77 949 0.03 0.721 0.018 0.0864 0.0021 0.97	z8 16 192 0.12 0.789 0.021 0.0879 0.0021 0.92	z9* 52 644 0.06 0.711 0.018 0.0871 0.0021 0.97	z10 50 634 0.06 0.718 0.018 0.0831 0.0020 0.96	z11* 20 237 0.11 0.705 0.019 0.0878 0.0021 0.93	z12* 36 446 0.04 0.701 0.018 0.0867 0.0021 0.94	z13* 18 214 0.14 0.708 0.019 0.0876 0.0021 0.93	z14* 15 179 0.10 0.711 0.019 0.0878 0.0022 0.92	z15* 15 179 0.14 0.707 0.019 0.0875 0.0022 0.91	z16* 12 150 0.10 0.716 0.020 0.0880 0.0022 0.89	z18a* 14 163 0.15 0.707 0.021 0.0877 0.0022 0.85	z18b* 11 126 0.15 0.717 0.020 0.0880 0.0022 0.89	z19 19 145 0.58 1.036 0.028 0.1184 0.0029 0.92	z20 91 1214 0.03 0.664 0.017 0.0822 0.0020 0.95	z21a* 76 949 0.02 0.704 0.018 0.0875 0.0022 0.95	z21b 11 125 0.33 0.720 0.023 0.0867 0.0022 0.80	z22 12 127 0.61 0.797 0.024 0.0882 0.0022 0.84	z23 30 364 0.05 0.733 0.020 0.0907 0.0023 0.92	z24* 9 107 0.27 0.711 0.021 0.0880 0.0022 0.85	z25 15 164 0.64 0.788 0.022 0.0878 0.0022 0.89	Arc-de-Fix augen gneiss MM11 -Col de Meyrand	Session #2 (May 12 th , 2015)	z26* 34 428 0.05 0.703 0.018 0.0872 0.0022 0.96	z27* 17 209 0.08 0.712 0.019 0.0875 0.0022 0.94	z29* 14 170 0.18 0.708 0.019 0.0884 0.0022 0.93

* analyses retained for calculation of Concordia date Couzinié et al., 2017. Supplementary

Table 6 :

 6 In situ LA-MC-ICPMS Lu-Hf isotope data for zircon standards analyzed in this study

	Age g	(Ma)	601	601	601	601	601	601	601	601	601	601	601	601	601	601	601	601	601
	f
	T DM2	(Ga)	2.19	2.18	2.13	2.17	2.19	2.14	2.17	2.13	2.16	2.16	2.15	2.19	2.15	2.16	2.15	2.16	2.16
	εHf (t) e ±2σ c	(abs.)	-14.7 1.0	-14.5 0.9	-13.6 1.0	-14.4 1.1	-14.6 1.0	-13.8 1.1	-14.3 1.0	-13.5 1.1	-14.1 0.9	-14.2 1.1	-14.0 1.0	-14.7 1.1	-14.0 1.1	-14.1 1.1	-14.0 1.0	-14.2 1.0	-14.2 1.1	-14.2
	176 Hf e	177 Hf (t)	0.281990	0.281998	0.282022	0.281999	0.281993	0.282015	0.282001	0.282024	0.282009	0.282004	0.282010	0.281990	0.282012	0.282007	0.282011	0.282005	0.282006	0.282006
	±2σ c	(abs.)	0.000029	0.000024	0.000027	0.000031	0.000030	0.000031	0.000029	0.000032	0.000026	0.000030	0.000028	0.000032	0.000030	0.000031	0.000029	0.000029	0.000030
	176 Hf	177 Hf	0.281993	0.282000	0.282025	0.282002	0.281996	0.282018	0.282004	0.282027	0.282011	0.282007	0.282013	0.281992	0.282014	0.282010	0.282013	0.282007	0.282009	0.282008
	b
	Sig Hf	(V)	15	16	11	11	10	10	9	8	9	9	8	8	6	7	8	7	7
	±2σ 176 Lu a ±2σ 178 Hf ±2σ 180 Hf ±2σ	(abs.) 177 Hf (abs.) 177 Hf (abs.) 177 Hf (abs.)	0.0006 0.00026 0.00002 1.46718 0.00004 1.88680 0.00014	0.0006 0.00025 0.00002 1.46722 0.00003 1.88686 0.00008	0.0006 0.00025 0.00002 1.46717 0.00004 1.88652 0.00012	0.0006 0.00025 0.00002 1.46726 0.00004 1.88637 0.00011	0.0006 0.00025 0.00002 1.46726 0.00005 1.88653 0.00011	0.0006 0.00025 0.00001 1.46722 0.00005 1.88657 0.00011	0.0006 0.00025 0.00001 1.46725 0.00005 1.88638 0.00012	0.0006 0.00025 0.00001 1.46729 0.00005 1.88632 0.00011	0.0006 0.00024 0.00001 1.46727 0.00005 1.88650 0.00012	0.0006 0.00025 0.00001 1.46733 0.00006 1.88640 0.00014	0.0006 0.00024 0.00001 1.46721 0.00007 1.88644 0.00012	0.0006 0.00024 0.00001 1.46729 0.00005 1.88653 0.00013	0.0006 0.00024 0.00001 1.46722 0.00006 1.88630 0.00021	0.0006 0.00024 0.00001 1.46731 0.00004 1.88657 0.00017	0.0006 0.00024 0.00001 1.46728 0.00005 1.88657 0.00014	0.0006 0.00024 0.00001 1.46722 0.00006 1.88645 0.00012	0.0006 0.00024 0.00001 1.46723 0.00007 1.88649 0.00012	0.00024 1.46725 1.88651
	Spot size 176 Yb a	(µm) 177 Hf	40 0.0080	40 0.0075	40 0.0074	40 0.0074	40 0.0074	40 0.0073	40 0.0074	40 0.0073	40 0.0073	40 0.0075	40 0.0071	40 0.0071	40 0.0074	40 0.0072	40 0.0070	40 0.0070	40 0.0071	0.0073
		GJ-1 (08/02/2016)	GJ1-12Jcm-40_1	GJ1-12Jcm-40_2	GJ1-12Jcm-40_3	GJ1-12Jcm-40_4	GJ1-12Jcm-40_5	GJ1-12Jcm-40_6	GJ1-12Jcm-40_7	GJ1-12Jcm-40_8	GJ1-12Jcm-40_9	GJ1-12Jcm-40_10	GJ1-12Jcm-40_11	GJ1-12Jcm-40_12	GJ1-12Jcm-40_13	GJ1-12Jcm-40_14	GJ1-12Jcm-40_15	GJ1-12Jcm-40_16	GJ1-12Jcm-40_17	Average	2 S.E. (abs.)

Table B1 :

 B1 Whole-rock major and trace element compositions obtained on lithologies from the UGU/LGU

	Sample	MG01	MG02	MG04	MG05	MG06	RV-1	RV-2	MM01	MM02
	Ref ALS	LR17005608 LR17005608 LR17005608 LR17005608 LR17005608 LR16016981 LR16016981 LR15096747 LR15096747
	Long	4.57860	4.57769	4.57820	4.58819	4.58827	4.58827	4.58827	4.43565	4.51147
	Lat	45.59175	45.59077	45.59086	45.59650	45.59646	45.59646	45.59646	45.08400	45.07050
	Locality	Riverie	Riverie	Riverie	Riverie	Riverie	Riverie	Riverie	Rochepaule Fromentoux
	Type	amphibolite	amphibolite	amphibolite	amphibolite	amphibolite	tonalite	tonalite	amphibolite	amphibolite
	Details									layered
	SiO 2	49.30	52.90	48.60	51.90	51.40	68.40	65.50	45.90	43.80
	Al 2 O 3	17.30	15.55	17.10	15.65	14.95	15.20	15.55	15.40	13.40
	Fe 2 O 3	7.62	10.85	7.55	8.86	12.20	4.33	5.47	13.45	12.70
	CaO	14.05	8.10	12.65	8.64	7.39	4.50	3.77	10.95	14.45
	MgO	8.49	4.17	9.55	7.50	4.97	2.13	2.84	3.60	7.62
	Na 2 O	2.19	4.11	2.06	4.04	4.32	5.08	4.96	3.46	1.77
	K 2 O	0.30	0.59	0.62	0.87	0.81	0.40	0.57	1.01	0.61
	Cr 2 O 3	0.04	0.01	0.07	0.04	<0,01	0.01	<0,01	0.02	0.07
	TiO 2	0.39	1.82	0.28	1.30	2.36	0.37	0.40	2.72	2.56
	MnO	0.13	0.14	0.13	0.17	0.21	0.08	0.07	0.15	0.17
	P 2 O 5	0.02	0.26	0.02	0.13	0.28	0.04	0.06	0.90	0.52
	SrO	0.03	0.02	0.02	0.01	0.02	0.02	0.03	0.12	0.15
	BaO	<0,01	0.01	0.02	0.04	0.02	0.02	0.03	0.05	0.01
	C	0.02	0.02	0.06	0.01	0.05	0.02	0.12	0.01	0.02
	S	0.16	0.06	0.02	<0,01	0.07	0.11	<0,01	0.10	0.55
	Ba	42	87.7	159	323	198	222	244	415	48.6
	Ce	1.8	27.5	1.6	14.7	23.9	19.9	16.8	98.7	84.7
	Cr	330	70	550	270	30	20	10	120	490
	Cs	5.50	0.35	23.20	0.76	1.12	0.26	1.18	1.27	0.64
	Dy	1.38	6.00	0.95	4.30	7.04	2.33	1.62	6.45	5.49
	Er	1.06	3.99	0.69	2.94	4.17	1.53	1.10	2.90	2.55
	Eu	0.45	1.58	0.33	1.16	1.80	0.66	0.57	3.19	2.43
	Ga	15.3	25.2	14.8	17.1	23.6	14.5	15.9	23.4	23.9
	Gd	1.23	6.40	0.90	4.47	7.14	2.44	1.69	9.26	7.06
	Hf	0.4	4.4	0.3	2.6	4.0	3.5	3.5	7.5	5.9
	Ho	0.31	1.36	0.28	0.97	1.41	0.50	0.33	1.09	0.88
	La	0.9	11.3	1.2	6.4	9.8	8.3	8.0	43.0	40.9
	Lu	0.10	0.55	0.08	0.37	0.59	0.27	0.20	0.31	0.26
	Nb	0.2	6.3	0.2	3.8	4.4	2.3	1.9	58.2	48.4
	Nd	2.0	19.3	1.4	10.6	19.1	10.8	9.2	55.6	42.4
	Pr	0.28	4.02	0.30	2.23	3.85	2.41	2.06	12.65	9.57
	Rb	7.7	7.9	20.1	16.4	17.6	7.9	13.9	13.8	8.2
	Sm	0.88	5.38	0.54	3.40	5.28	2.71	1.99	11.10	8.33
	Sn	<1	1	2	1	1	2	1	4	29
	Sr	277.0	293.0	208.0	192.0	249.0	250.0	287.0	968.0	1450.0
	Ta	<0,1	0.4	<0,1	0.2	0.1	0.3	0.4	3.8	3.5
	Tb	0.25	1.07	0.16	0.74	1.11	0.36	0.23	1.15	1.01
	Th	0.18	1.03	0.05	0.84	1.21	0.74	1.14	5.28	5.68
	Tl	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5
	Tm	0.15	0.58	0.10	0.39	0.63	0.24	0.16	0.37	0.33
	U	0.07	0.74	0.06	0.56	0.65	0.38	0.55	1.64	1.49
	V	215	234	177	227	362	78	113	105	226
	W	<1	<1	<1	1	1	<1	<1	1	1
	Y	8.3	37.8	6.6	24.2	40.6	14.9	9.9	28.7	25.6
	Yb	0.94	3.35	0.70	2.51	4.37	1.66	1.18	2.12	1.94
	Zr	12	189	12	99	193	134	107	327	255
	As	5.2	0.2	3.1	<0,1	0.3	0.3	<0,1	1.5	67.2
	Bi	0.08	0.02	0.06	0.02	0.01	0.02	0.01	0.14	5.62
	Hg	<0,005	<0,005	0.006	<0,005	<0,005	<0,005	<0,005	0.007	<0,005
	Sb	0.18	0.07	0.15	0.13	0.15	<0,05	0.73	0.07	0.06
	Se	0.3	0.2	0.2	0.2	0.7	0.2	0.4	0.6	1.2
	Te	0.01	0.01	0.01	0.01	0.01	<0,01	<0,01	<0,01	0.04
	LOI	1.07	0.47	1.39	1.01	1.23	0.51	2.25	0.41	1.42
	Total	100.93	99	100.06	100.16	100.16	101.09	101.5	98.14	99.25
	Ag	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	0.9	1
	Cd	<0,5	0.6	<0,5	0.7	0.6	<0,5	<0,5	<0,5	0.8
	Co	36	29	45	36	35	13	14	36	68
	Cu	53	29	10	1	20	25	2	33	144
	Li	<10	<10	10	<10	<10	10	30	10	<10
	Mo	<1	1	<1	<1	<1	<1	<1	<1	<1
	Ni	63	16	119	53	5	13	10	69	286
	Pb	3	2	9	<2	<2	2	<2	2	6
	Sc	44	25	39	35	31	10	14	12	21
	Zn	36	103	50	81	73	33	46	144	123
	Ge	<5	<5	<5	<5	<5	<5	<5	<5	<5
	In	0.007	0.024	0.009	0.013	0.018	0.007	0.019	0.049	0.111
	Re	<0,001	0.001	<0,001	<0,001	0.001	<0,001	<0,001	0.001	0.001

Table B1 (

 B1 continued): Whole-rock major and trace element compositions obtained on lithologies from the LGU

	Sample	MM03	MM04	PIL-16-01	SEN-16-01	PdB-16-01a PdB-16-01b ROC-16-01	CHA-16-02	BOR-16-01
	Ref ALS	LR15096747 LR15096747 LR17005608 LR17005608 LR17005608 LR17005608 LR17005608 LR17005608 LR17005608
	Long	4.51147	4.51147	4.41651	3.60390	4.30584	4.30584	4.07712	3.79093	3.58485
	Lat	45.07050	45.07050	45.40051	45.16402	44.65707	44.65707	44.33320	44.54597	44.27880
	Locality	Fromentoux Fromentoux Saint-Etienne	Jax	Pont-de-Bayzan	Pont-de-Bayzan	Le Travers Chasseradès Pied de Borne
	Type	amphibolite	amphibolite metasediment metasediment paragneiss	paragneiss	granite	metasediment	granite
	Details							Ms-Bt-Gt syntectonic granite		Porphyroid granite
	SiO 2	45.10	46.60	87.50	77.70	67.00	59.60	75.30	72.70	69.50
	Al 2 O 3	13.25	13.40	7.20	12.75	14.30	17.45	14.80	13.70	13.80
	Fe 2 O 3	12.90	13.85	1.63	2.46	6.63	8.22	1.37	3.54	2.89
	CaO	16.95	9.97	0.45	1.35	2.18	1.35	0.47	0.31	1.70
	MgO	4.93	5.73	0.58	0.81	2.56	3.41	0.11	1.44	1.47
	Na 2 O	2.43	3.63	2.06	2.53	2.79	2.41	4.64	0.02	2.66
	K 2 O	0.36	0.55	0.87	1.75	2.62	4.35	3.77	5.37	5.01
	Cr 2 O 3	0.06	0.02	<0,01	0.01	0.02	0.01	<0,01	0.01	0.01
	TiO 2	1.75	3.36	0.37	0.54	1.14	0.95	0.04	0.54	0.38
	MnO	0.20	0.15	0.01	0.06	0.09	0.07	0.06	0.05	0.06
	P 2 O 5	0.19	0.33	0.06	0.14	0.27	0.26	0.27	0.14	0.22
	SrO	0.10	0.06	0.01	0.02	0.03	0.02	<0,01	<0,01	0.03
	BaO	0.01	0.01	0.02	0.04	0.06	0.09	<0,01	0.10	0.07
	C	0.04	0.01	0.02	0.03	0.01	<0,01	0.01	0.04	0.01
	S	0.16	0.32	<0,01	<0,01	0.08	0.01	<0,01	<0,01	<0,01
	Ba	53	127	205	341	525	885	26.1	922	629
	Ce	24.7	43.2	73.6	81.4	66.3	77.8	7.0	53.7	61.7
	Cr	390	120	20	40	110	110	10	60	60
	Cs	1.62	0.31	1.28	1.58	10.05	16.45	9.25	12.55	16.55
	Dy	3.39	5.85	3.43	5.56	5.39	6.15	0.84	3.87	3.43
	Er	1.92	2.83	2.00	3.11	3.28	3.84	0.48	2.15	2.12
	Eu	1.22	2.00	0.92	1.41	1.49	1.21	0.09	0.38	0.83
	Ga	17.9	20.3	7.6	14.5	18.8	27.8	25.7	15.8	18.3
	Gd	4.18	6.30	4.16	6.43	5.79	6.90	0.64	4.31	4.21
	Hf	2.7	4.5	7.9	7.5	8.4	5.5	1.6	6.1	4.8
	Ho	0.63	0.97	0.62	1.08	1.17	1.30	0.13	0.80	0.72
	La	11.1	19.6	35.4	39.8	33.7	38.3	3.8	28.0	32.2
	Lu	0.20	0.26	0.28	0.42	0.47	0.49	0.07	0.34	0.30
	Nb	13.9	26.6	8.4	10.2	13.2	14.4	16.2	9.0	17.2
	Nd	14.7	25.8	27.5	33.5	31.7	37.3	2.7	24.9	25.7
	Pr	3.19	5.70	8.08	9.42	8.32	10.10	0.74	6.51	7.28
	Rb	9.9	5.7	30.9	56.3	105.5	205.0	395.0	200.0	266.0
	Sm	3.96	7.01	5.20	6.77	6.81	8.43	0.82	5.10	5.58
	Sn	38	2	1	2	3	4	17	1	14
	Sr	817.0	548.0	88.6	212.0	277.0	244.0	15.9	27.4	297.0
	Ta	1.0	1.8	0.7	0.8	0.8	0.9	2.5	0.6	2.4
	Tb	0.63	0.93	0.62	0.92	0.95	1.05	0.15	0.64	0.64
	Th	1.60	2.63	15.45	12.80	8.98	9.38	2.85	9.01	25.20
	Tl	<0,5	<0,5	<0,5	<0,5	0.6	0.9	2.2	0.9	1.1
	Tm	0.25	0.35	0.29	0.45	0.47	0.53	0.09	0.33	0.30
	U	0.59	0.66	3.47	2.57	2.51	2.69	8.57	3.21	8.26
	V	201	326	21	45	131	163	<5	97	42
	W	2	<1	2	1	1	2	1	3	1
	Y	16.9	25.7	17.8	27.9	29.7	38.2	4.8	21.4	21
	Yb	1.44	2.04	1.71	2.82	2.96	3.39	0.58	2.12	2.16
	Zr	104	179	320	288	314	241	30	232	190
	As	11.6	2.3	0.7	17	<0,1	0.9	3.5	0.4	1.3
	Bi	6.5	0.26	0.12	0.19	0.27	0.25	2.97	0.22	1.01
	Hg	0.008	0.009	<0,005	<0,005	<0,005	<0,005	<0,005	<0,005	<0,005
	Sb	0.09	0.06	<0,05	<0,05	0.08	0.13	0.06	0.08	<0,05
	Se	0.2	1	0.6	0.3	0.5	0.9	<0,2	0.6	0.6
	Te	0.02	<0,01	<0,01	0.03	0.06	0.04	0.02	0.03	0.01
	LOI	1.41	0.74	0.7	1.46	1.15	2.51	0.47	3.01	0.67
	Total	99.64	98.4	101.46	101.62	100.84	100.7	101.3	100.93	98.47
	Ag	0.8	0.9	<0,5	<0,5	<0,5	<0,5	<0,5	0.7	<0,5
	Cd	0.9	0.5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5
	Co	56	55	2	4	14	17	<1	7	5
	Cu	145	126	5	9	30	32	2	56	2
	Li	10	<10	10	10	60	90	50	210	100
	Mo	<1	<1	<1	<1	<1	<1	<1	<1	<1
	Ni	240	54	9	7	29	53	<1	19	9
	Pb	9	<2	12	75	15	21	33	6	37
	Sc	20	28	3	5	14	18	2	8	7
	Zn	183	134	24	127	83	180	63	43	46
	Ge	<5	<5	<5	<5	<5	<5	<5	<5	<5
	In	0.045	0.035	0.009	0.013	0.069	0.082	0.011	0.026	0.042
	Re	0.001	0.002	0.001	<0,001	<0,001	<0,001	<0,001	<0,001	<0,001

Table B1 (

 B1 continued): Whole-rock major and trace element compositions obtained on the Masméjean dome area

	Sample	CHA-15-05	CHA-15-07	CHA-15-17	CHA-15-19	CHA-15-24	CHA-15-29	CHA-15-33	CHA-15-34	CHA-15-25
	Ref ALS	LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR16016981
	Long	3.88036	3.86111	3.88742	3.88017	3.90175	3.87859	3.84491	3.84598	3.90264
	Lat	44.52902	44.53889	44.53103	44.52806	44.53318	44.51265	44.53368	44.53308	44.53148
	Locality	Les Orts	L'Adrech	Barrage de Puylaurent	Les Orts	Le Ranc	Piéchelapie	Le Couste	Le Couste	Le Ranc
	Type	granite	granite	augen gneiss	granite	granite	granite	granite	granite	granite
	Details		"4-Vios type"	metatexite				"4-Vios type"
	SiO 2	71.30	66.00	69.60	73.00	74.30	73.60	71.40	75.00	72.60
	Al 2 O 3	14.20	14.95	15.70	14.45	14.35	14.05	14.65	14.25	14.45
	Fe 2 O 3	2.41	3.75	2.47	1.59	0.92	0.90	1.83	1.01	1.49
	CaO	0.29	1.40	0.99	0.43	0.45	0.45	0.78	0.44	0.62
	MgO	0.53	2.37	0.56	0.38	0.13	0.10	0.53	0.07	0.27
	Na 2 O	2.85	1.78	4.05	2.81	3.68	4.15	2.99	4.22	3.49
	K 2 O	6.22	6.08	4.78	5.87	4.96	4.10	5.83	4.37	5.22
	Cr 2 O 3	0.01	0.02	<0,01	<0,01	<0,01	<0,01	0.01	<0,01	<0,01
	TiO 2	0.30	0.64	0.26	0.15	0.05	0.03	0.19	0.05	0.12
	MnO	0.02	0.06	0.03	0.02	0.01	0.02	0.03	0.02	0.02
	P 2 O 5	0.20	0.56	0.27	0.30	0.19	0.26	0.30	0.22	0.33
	SrO	<0,01	0.03	<0,01	<0,01	<0,01	<0,01	<0,01	<0,01	<0,01
	BaO	0.09	0.14	0.08	0.08	0.02	0.02	0.04	0.02	0.02
	C	0.02	0.03	0.01	0.01	0.01	0.01	0.01	0.01	0.02
	S	0.01	<0,01	0.01	0.01	0.02	0.02	0.01	<0,01	0.01
	Ba	773	1310	668	733	167.5	161	390	158.5	167.5
	Ce	78.9	55.1	51.4	32.9	7.0	9.3	37.8	9.6	18.3
	Cr	20	100	10	<10	<10	10	20	<10	<10
	Cs	3.83	14.65	9.21	5.94	5.10	7.19	12.15	9.28	5.14
	Dy	3.74	3.37	5.84	2.88	0.23	1.00	2.33	1.27	2.97
	Er	1.96	1.59	3.45	1.41	0.08	0.57	1.02	0.50	1.30
	Eu	0.86	1.11	0.93	0.61	0.15	0.09	0.47	0.20	0.25
	Ga	15.2	17.8	19.4	16.3	18.3	19.3	22.7	19.3	22.5
	Gd	4.46	4.23	5.00	2.61	0.38	0.76	2.73	1.00	2.26
	Hf	5.9	4.8	4.6	3.2	0.8	1.6	3.1	1.0	1.5
	Ho	0.67	0.56	1.19	0.51	0.04	0.20	0.42	0.21	0.50
	La	37.9	30.0	24.6	16.7	4.5	5.2	20.2	5.1	8.7
	Lu	0.23	0.18	0.37	0.16	0.02	0.07	0.12	0.06	0.13
	Nb	13.9	17.4	11.2	13.6	6.8	11.2	11.2	11.0	13.0
	Nd	32.6	26.9	23.7	13.6	2.6	3.8	17.0	3.9	8.3
	Pr	8.73	6.39	5.84	3.43	0.72	1.05	4.47	1.01	2.15
	Rb	171.5	221.0	186.5	174.0	190.0	202.0	284.0	235.0	203.0
	Sm	5.68	5.07	5.48	2.91	0.42	0.72	3.46	1.18	2.23
	Sn	10	12	6	4	5	13	15	13	7
	Sr	112.0	279.0	96.2	135.5	60.2	36.6	103.0	37.0	61.3
	Ta	1.1	4.2	1.0	1.2	0.6	3.0	1.5	4.3	1.0
	Tb	0.69	0.57	0.86	0.47	0.03	0.12	0.43	0.21	0.43
	Th	18.35	13.50	10.10	8.06	2.99	2.52	9.41	3.04	3.66
	Tl	1.1	1.2	0.8	1.0	0.8	0.9	1.2	1.3	0.8
	Tm	0.25	0.22	0.46	0.20	0.03	0.08	0.12	0.07	0.18
	U	8.28	7.62	2.82	6.06	18.75	2.64	6.60	2.91	9.96
	V	12	62	19	11	<5	6	16	<5	<5
	W	1	1	2	1	<1	3	5	3	3
	Y	18.9	17.8	32.8	16.2	1.3	6.4	11.9	7	15.4
	Yb	1.41	1.25	2.87	1.25	0.11	0.63	0.91	0.48	1.03
	Zr	194	152	145	81	14	30	89	20	34
	As	10.6	7.3	2.4	1.2	0.9	0.5	1.7	0.4	0.8
	Bi	0.11	0.4	0.04	2.94	6.59	1.66	0.65	1	2.61
	Hg	<0,005	<0,005	<0,005	0.006	<0,005	<0,005	<0,005	<0,005	<0,005
	Sb	0.11	0.1	0.13	<0,05	<0,05	0.06	<0,05	<0,05	<0,05
	Se	0.5	0.7	0.8	0.4	<0,2	0.2	0.2	0.3	0.4
	Te	<0,01	<0,01	<0,01	0.04	<0,01	0.02	<0,01	<0,01	0.02
	LOI	0.96	1.92	0.91	1.01	0.61	0.69	0.71	0.61	0.7
	Total	99.38	99.7	99.7	100.09	99.67	98.37	99.29	100.28	99.33
	Ag	<0,5	<0,5	<0,5	0.5	<0,5	<0,5	<0,5	<0,5	<0,5
	Cd	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5
	Co	2	8	3	1	<1	<1	3	<1	1
	Cu	15	7	2	7	6	6	2	1	3
	Li	30	110	60	40	30	20	70	30	40
	Mo	<1	<1	<1	<1	<1	<1	<1	<1	<1
	Ni	4	19	4	1	<1	1	4	1	<1
	Pb	29	40	22	23	30	10	29	16	19
	Sc	4	10	3	3	1	2	4	2	6
	Zn	34	121	49	15	19	8	45	12	23
	Ge	<5	<5	<5	<5	<5	<5	<5	<5	<5
	In	0.032	0.045	0.035	0.012	0.011	0.006	0.023	0.009	0.017
	Re	<0,001	<0,001	0.001	0.001	<0,001	<0,001	<0,001	<0,001	<0,001

Table B1 (

 B1 continued): Whole-rock major and trace element compositions obtained on the Masméjean dome area

	Sample	CHA-15-35	CHA-15-36	CHA-15-41	CHA-15-43	CHA-15-44	CHA-15-47	CHA-15-48	CHA-15-49	CHA-15-51
	Ref ALS	LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR16016981
	Long	3.84598	3.84611	3.90506	3.87934	3.80854	3.96989	3.96989	3.90300	3.83309
	Lat	44.53308	44.53295	44.54657	44.56799	44.54674	44.60493	44.60493	44.52644	44.57011
	Locality	Le Couste	Le Couste	les Clous-Maurines	Masmejean	Mirandol	St-Laurent-les-Bains	St-Laurent-les-Bains	Le Mourio	Majousseires
	Type	leucogneiss	leucogneiss	granite	migmatite	leucogneiss	migmatite	augen gneiss	granite	granite
	Details				in source leucosome		in source leucosome	metatexite
	SiO 2	75.20	77.30	69.30	75.10	78.60	76.30	70.60	71.90	73.80
	Al 2 O 3	12.45	13.25	15.35	13.25	12.40	13.15	14.25	14.60	14.85
	Fe 2 O 3	1.37	1.35	2.67	1.02	1.23	1.19	2.57	2.11	1.30
	CaO	0.40	0.46	0.55	0.31	0.36	0.45	0.74	0.41	0.45
	MgO	0.10	0.09	0.96	0.14	0.09	0.19	0.64	0.67	0.14
	Na 2 O	2.91	3.06	2.75	2.61	3.08	2.57	2.72	2.93	3.60
	K 2 O	4.52	4.77	5.93	6.27	4.29	5.96	5.40	5.41	5.07
	Cr 2 O 3	<0,01	<0,01	<0,01	<0,01	<0,01	<0,01	0.01	0.01	<0,01
	TiO 2	0.09	0.09	0.47	0.06	0.06	0.09	0.29	0.27	0.07
	MnO	0.02	0.02	0.03	0.01	0.02	0.01	0.03	0.02	0.03
	P 2 O 5	0.29	0.35	0.29	0.26	0.36	0.13	0.28	0.27	0.34
	SrO	<0,01	<0,01	0.02	<0,01	<0,01	<0,01	<0,01	0.01	<0,01
	BaO	0.01	0.02	0.10	0.02	0.01	0.06	0.07	0.08	0.01
	C	0.01	0.01	<0,01	0.01	0.01	0.01	<0,01	0.01	0.01
	S	0.01	<0,01	<0,01	<0,01	0.01	0.01	0.02	<0,01	<0,01
	Ba	102	181.5	945	147	64.5	526	604	798	128
	Ce	11.9	13.3	68.3	10.3	6.9	16.0	58.1	64.4	8.0
	Cr	<10	<10	20	<10	<10	<10	20	20	<10
	Cs	8.76	19.05	6.59	6.58	12.30	5.92	15.05	6.59	6.73
	Dy	2.41	2.72	2.69	2.59	1.91	3.27	5.49	2.92	1.98
	Er	0.92	1.08	1.32	1.48	0.82	2.48	3.30	1.56	0.93
	Eu	0.14	0.20	1.03	0.17	0.10	0.60	0.85	0.73	0.20
	Ga	17.9	20.9	21.2	15.8	21.0	12.8	19.4	18.8	22.3
	Gd	1.54	1.80	4.08	1.68	1.05	1.77	5.11	3.44	1.44
	Hf	1.9	2.3	6.3	2.4	2.5	1.9	5.0	4.1	0.8
	Ho	0.41	0.46	0.49	0.46	0.32	0.71	1.13	0.51	0.30
	La	5.3	5.7	39.7	4.9	3.1	7.8	27.2	32.4	3.9
	Lu	0.07	0.12	0.16	0.19	0.08	0.31	0.37	0.18	0.10
	Nb	12.2	15.4	14.3	7.5	16.7	4.2	13.2	14.4	16.3
	Nd	5.1	5.8	33.5	4.9	3.5	6.7	26.1	27.7	3.7
	Pr	1.37	1.52	8.51	1.25	0.80	1.67	6.56	7.16	1.07
	Rb	261.0	331.0	222.0	216.0	362.0	179.5	229.0	207.0	255.0
	Sm	1.50	1.73	6.02	1.29	0.89	1.76	5.84	4.74	1.27
	Sn	8	11	6	6	14	5	6	7	18
	Sr	20.2	30.0	264.0	54.2	11.5	85.8	88.8	214.0	34.4
	Ta	14.5	2.5	1.7	0.6	3.5	0.6	1.0	2.8	2.9
	Tb	0.33	0.42	0.53	0.34	0.23	0.34	0.90	0.49	0.26
	Th	4.80	5.41	26.90	4.12	3.61	3.74	11.00	22.60	1.80
	Tl	1.0	1.7	1.1	1.1	1.4	0.8	1.2	1.0	0.8
	Tm	0.13	0.14	0.16	0.20	0.11	0.33	0.44	0.20	0.12
	U	8.91	6.17	5.92	6.37	23.20	3.87	4.54	4.15	3.85
	V	<5	6	33	5	<5	5	23	24	<5
	W	4	5	2	1	12	1	2	3	5
	Y	12.2	15.5	14.4	14.7	11.1	21.6	32.9	15.6	10.5
	Yb	0.69	0.86	1.13	1.37	0.64	2.16	2.78	1.47	0.89
	Zr	37	43	228	42	39	42	162	146	17
	As	1.3	1.4	7.8	13.4	1.2	1	2.3	1.4	2
	Bi	0.8	0.1	0.14	0.31	3.24	0.1	0.21	0.05	4.78
	Hg	0.01	<0,005	<0,005	<0,005	0.005	<0,005	<0,005	<0,005	<0,005
	Sb	0.05	0.19	0.11	0.14	0.12	<0,05	0.12	<0,05	<0,05
	Se	0.6	0.7	0.6	0.4	0.4	<0,2	0.7	0.5	0.4
	Te	<0,01	<0,01	<0,01	<0,01	0.01	<0,01	<0,01	<0,01	<0,01
	LOI	0.65	0.67	1.61	0.7	0.76	0.46	0.97	1.54	0.84
	Total	98.01	101.43	100.03	99.75	101.26	100.56	98.57	100.23	100.5
	Ag	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5
	Cd	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5
	Co	<1	<1	2	<1	<1	1	2	3	<1
	Cu	3	12	3	3	3	1	9	5	2
	Li	60	70	60	20	50	40	70	30	30
	Mo	<1	<1	<1	<1	<1	<1	<1	<1	<1
	Ni	<1	1	6	<1	<1	1	5	6	<1
	Pb	15	118	33	35	6	25	23	23	20
	Sc	2	2	5	2	2	1	4	4	3
	Zn	25	33	39	10	30	16	62	21	18
	Ge	<5	<5	<5	<5	<5	<5	<5	<5	<5
	In	0.024	0.023	0.02	0.016	0.013	0.018	0.055	0.007	0.012
	Re	<0,001	<0,001	<0,001	<0,001	<0,001	<0,001	<0,001	0.001	<0,001

Table B1 (

 B1 continued): Whole-rock major and trace element compositions obtained on the Masméjean dome area Mineral major element compositions were obtained using a Zeiss EVO MA15 Scanning Electron Microscope at the Central Analytical Facility (CAF) of Stellenbosch University, South Africa. Mineral compositions were quantied by EDX (Energy Dispersive X-ray)

		B.2 Mineral chemistry
	Sample	CHA-15-52	CHA-15-59	CHA-15-63 CHA-15-65L CHA-15-65M	SC14 40	SC14 46
	Ref ALS Long	LR16016981 LR16016981 LR16016981 LR16016981 LR16016981 LR15096747 LR15096747 3.82921 3.87213 3.88324 3.88742 3.88742 3.90157 4.01186 B.2.1 Analytical details
	Lat	44.57224	44.60196	44.59365	44.53103	44.53103	44.53354	44.61692
	Locality	Majousseires la Soucheire Charbonneire	Barrage de Puylaurent	Barrage de Puylaurent	Chassezac valley	Borne
	Type	leucogneiss	granite	migmatite	migmatite	augen gneiss	granite	leucosome
	Details			in source leucosome	in source leucosome	metatexite	concordant vein within paragneiss	in situ leucosome in orthogneiss
	SiO 2	76.00	72.60	72.60	73.70	71.00	74.00	74.00
	Al 2 O 3	12.90	15.10	14.85	14.65	13.70	14.25	14.50
	Fe 2 O 3	1.91	1.90	0.70	1.03	4.12	1.79	1.39
	CaO	0.42	0.64	0.52	0.44	0.43	0.53	1.72
	MgO	0.13	0.37	0.07	0.18	1.38	0.34	0.45
	Na 2 O	3.01	3.07	3.25	3.59	2.60	2.78	3.38
	K 2 O	4.88	5.10	7.27	5.99	5.14	5.90	4.23
	Cr 2 O 3	<0,01	<0,01	<0,01	<0,01	0.01	<0,01	<0,01
	TiO 2	0.12	0.23	0.03	0.07	0.41	0.17	0.11
	MnO	0.03	0.03	0.02	0.02	0.05	0.02	0.03
	P 2 O 5	0.29	0.26	0.49	0.21	0.18	0.18	0.17
	SrO	<0,01	0.01	<0,01	<0,01	<0,01	0.01	0.03
	BaO	0.01	0.05	0.04	0.04	0.04	0.07	0.09
	C	0.01	0.01	0.01	0.01	0.01	0.03	<0,01
	S	<0,01	<0,01	<0,01	<0,01	<0,01	0.01	<0,01
	Ba	62.1	467	352	361	375	674	857
	Ce	15.9	77.8	7.0	10.4	55.7	31.9	31.4
	Cr	<10	<10	<10	<10	20	10	10
	Cs	4.14	7.62	5.15	5.38	14.75	7.32	4.79
	Dy	4.51	2.46	2.03	1.42	4.55	3.18	2.26
	Er	2.83	1.00	1.22	0.75	2.54	1.54	1.04
	Eu	0.10	0.67	0.40	0.44	0.66	0.63	0.97
	Ga	19.6	20.5	14.5	14.2	19.1	21.6	17.9
	Gd	2.63	4.26	1.73	1.22	4.48	3.45	2.60
	Hf	3.4	4.2	1.4	1.2	4.3	3.0	2.2
	Ho	0.99	0.47	0.43	0.25	0.86	0.63	0.34
	La	7.3	41.8	3.0	5.3	26.3	17.4	19.7
	Lu	0.29	0.14	0.17	0.09	0.29	0.24	0.12
	Nb	15.3	13.1	1.8	4.7	14.9	11.0	3.7
	Nd	7.8	31.0	4.1	5.2	24.7	15.4	15.8
	Pr	1.95	8.13	0.86	1.22	6.04	4.83	4.36
	Rb	229.0	212.0	263.0	207.0	265.0	193.0	111.5
	Sm	2.42	5.73	1.38	1.13	5.23	2.95	2.76
	Sn	7	11	8	5	11	6	4
	Sr	21.6	126.0	63.4	78.7	66.6	119.5	286.0
	Ta	2.4	1.6	1.5	0.9	1.4	1.3	0.4
	Tb	0.63	0.53	0.31	0.23	0.72	0.45	0.33
	Th	8.40	21.20	0.87	2.42	10.65	8.16	8.01
	Tl	1.1	0.9	1.0	0.8	1.1	0.7	<0,5
	Tm	0.38	0.14	0.20	0.11	0.36	0.23	0.15
	U	3.01	5.93	5.70	2.57	4.80	6.44	2.46
	V	5	10	<5	6	38	<5	9
	W	5	3	<1	1	2	1	1
	Y	29.5	13.2	13.9	7.9	24.5	18.9	11.5
	Yb	2.49	0.97	1.19	0.67	2.01	1.33	1.07
	Zr	78	140	18	19	140	96	60
	As	2.6	1.9	11.8	0.5	1.9	0.4	1.7
	Bi	0.8	1.08	2.07	0.2	0.13	0.76	0.11
	Hg	<0,005	<0,005	<0,005	<0,005	<0,005	<0,005	0.005
	Sb	<0,05	<0,05	0.36	<0,05	<0,05	<0,05	<0,05
	Se	0.8	0.4	0.6	<0,2	0.3	<0,2	<0,2
	Te	<0,01	<0,01	<0,01	<0,01	<0,01	<0,01	0.03
	LOI	0.68	1.21	0.3	0.63	1.01	0.85	0.53
	Total	100.38	100.57	100.14	100.55	100.07	100.89	100.63
	Ag	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5
	Cd	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5	<0,5
	Co	1	1	<1	1	5	1	3
	Cu	5	1	12	1	1	4	4
	Li	30	60	20	20	130	20	30
	Mo	<1	<1	<1	<1	<1	<1	<1
	Ni	<1	1	<1	<1	12	<1	6
	Pb	21	24	52	35	28	39	31
	Sc	2	3	1	1	7	3	2
	Zn	21	47	29	19	107	37	14
	Ge	<5	<5	<5	<5	<5	<5	<5
	In	0.041	0.018	0.049	0.014	0.07	0.031	0.024
	Re	<0,001	<0,001	<0,001	<0,001	<0,001	<0,001	<0,001

Table B2 :

 B2 Mineral compositions of Riverie meta-tonalite samples RV-1 and RV-2

	RV1 -Amphiboles
	S 1	S 2	S 3	S 4	S 5	S 6	S 7	S 8	S 9 S 10 S 11 S 12 S 13
	SiO 2

Table B2 (cont.):

 B2 Mineral compositions of Riverie meta-tonalite samples RV-1 and RV-2 SiO 2 35.58 35.46 36.00 35.51 35.05 36.36 37.67 36.75 37.17 36.91 37.06 37.47 37.09 37.20 37.21 35.53 TiO 2 2.80 2.59 2.90 2.94 2.88 3.06 2.99 2.92 3.64 3.27 3.42 3.33 3.09 3.48 3.41 2.43 Al 2 O 3

		RV1 -Biotites
		S 3	S 4	S 6	S 7	S 8	S 9 S 10 S 11 S 12 S 13 S 14 S 15 S 16 S 17 S 18 S 19
														11.25
	Na 2 O 1.35 1.34 1.44 1.03 1.47 1.04 1.33 0.89 1.54 1.45 1.54 1.10 1.37
	K 2 O	0.37 0.38 0.36 0.42 0.56 0.41 0.47 0.30 0.41 0.42 0.45 0.26 0.46
	Total 97.44 98.29 98.74 98.51 99.57 98.93 98.42 98.74 98.88 99.00 99.10 99.34 99.24
	No. Ox 23	23	23	23	23	23	23	23	23	23	23	23	23
	Si	6.67 6.66 6.76 6.83 6.63 6.82 6.62 6.97 6.71 6.69 6.75 6.95 6.70
	Al iv	1.33 1.34 1.24 1.17 1.37 1.18 1.38 1.03 1.29 1.31 1.25 1.05 1.30
	Al vi	0.06 0.28 0.15 0.26 0.28 0.22 0.24 0.13 0.19 0.25 0.20 0.11 0.23
	Ti	0.10 0.08 0.08 0.06 0.09 0.06 0.08 0.06 0.08 0.08 0.07 0.06 0.08
	Fe3+ 1.45 0.91 1.06 0.81 0.85 0.82 0.90 0.99 1.06 0.89 1.01 1.05 0.99
	Fe2+ 0.38 1.06 0.85 1.04 1.16 1.09 1.10 0.81 0.92 1.09 0.95 0.78 1.05
	Mn	0.07 0.06 0.07 0.05 0.06 0.05 0.05 0.06 0.08 0.05 0.06 0.06 0.06
	Mg	2.94 2.60 2.79 2.78 2.56 2.76 2.64 2.95 2.67 2.64 2.71 2.94 2.60
	Ca	1.59 1.77 1.70 1.80 1.77 1.83 1.81 1.75 1.69 1.76 1.69 1.71 1.73
	Na	0.37 0.38 0.40 0.29 0.41 0.29 0.37 0.24 0.43 0.40 0.43 0.30 0.38
	K	0.07 0.07 0.07 0.08 0.10 0.07 0.09 0.05 0.07 0.08 0.08 0.05 0.08
	OH*	2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00
	Total 17.03 17.21 17.17 17.17 17.28 17.19 17.28 17.04 17.19 17.25 17.20 17.06 17.19

Table B2 (cont.):

 B2 .00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Total 19.55 19.58 19.63 19.58 19.49 19.55 19.61 19.59 19.55 19.64 19.64 19.56 19.56 19.55 19.59 19.53 Mineral compositions of Riverie meta-tonalite samples RV-1 and RV-2

	K 2 O Total 92.40 92.21 92.07 91.60 91.39 93.72 95.61 94.43 94.54 94.74 95.25 95.14 94.16 94.70 95.32 92.79 7.87 7.67 8.71 7.91 6.61 8.03 9.14 8.30 9.29 9.30 9.16 9.27 9.13 9.25 8.99 7.08 No. Ox 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 Si 5.59 5.58 5.64 5.57 5.50 5.58 5.67 5.58 5.66 5.62 5.62 5.66 5.66 5.65 5.62 5.51 Al iv 2.41 2.42 2.36 2.43 2.50 2.42 2.33 2.42 2.34 2.38 2.38 2.34 2.34 2.35 2.38 2.49 Al vi 0.21 0.25 0.22 0.22 0.16 0.19 0.24 0.23 0.22 0.23 0.16 0.25 0.29 0.24 0.24 0.26 Ti 0.33 0.31 0.34 0.35 0.34 0.35 0.34 0.33 0.42 0.37 0.39 0.38 0.35 0.40 0.39 0.28 Fe3+ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe2+ 2.60 2.58 2.28 2.29 2.45 2.33 2.19 2.23 2.22 2.23 2.28 2.23 2.20 2.23 2.21 2.50 Mn 0.02 0.03 0.02 0.02 0.02 0.02 0.03 0.03 0.02 0.02 0.03 0.00 0.00 0.00 0.03 0.03 Mg 2.77 2.80 2.97 3.05 3.18 3.06 2.99 3.08 2.87 2.92 2.94 2.92 2.95 2.90 2.91 3.06 Ca 0.04 0.02 0.00 0.00 0.03 0.02 0.02 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 RV2 -Plagioclase S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 S 10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 62.12 62.59 62.02 62.54 62.00 61.85 62.23 62.12 62.04 62.48 0.00
	Na K OH*	0.00 0.06 0.06 0.07 0.00 0.00 0.06 0.07 0.00 0.07 0.08 0.00 0.00 0.00 0.08 0.00 1.58 1.54 1.74 1.58 1.32 1.57 1.75 1.61 1.81 1.81 1.77 1.79 1.78 1.79 1.73 1.40 2.00 2RV1 -Plagioclase S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 S 10 S 11 S 12 S 13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 61.50 62.43 62.53 62.51 62.21 62.18 62.32 62.12 62.63 62.17 62.16 62.57 62.24 0.00
		SiO 2	TiO 2	Al 2 O 3

Table B3 :

 B3 Mineral compositions of Riverie granite sample RV-3SiO 2 36.50 36.53 36.55 36.72 36.70 36.33 35.81 36.37 34.73 35.31 35.81 36.21 36.24 36.13 36.57 35.77 36.34 TiO 2 3.60 3.32 3.22 3.10 3.61 3.15 2.90 2.95 2.94 3.19 3.69 3.14 3.43 3.06 3.18 3.29 3.89Al 2 O 3 14.08 14.25 14.55 14.29 14.18 14.18 14.13 14.53 14.17 13.94 14.51 14.14 14.49 14.26 14.49 14.36 14.27 FeO

	Biotite S 2	S 3	23.40 S 4	FeO 0.18 0.00 0.14 0.00 0.14 0.00 0.00 0.14 0.00 0.13 0.00 0.17 0.00 0.00 0.19 0.17 0.17 0.16 0.00 0.22 0.00 0.23 0.00	CaO 5.07 5.38 5.44 5.21 5.35 5.07 5.49 5.18 5.31 5.53 5.33 5.41 5.57 5.28 5.70 5.78 5.58 5.96 5.84 5.64 5.54 5.59 5.65 S 5	Na 2 O 8.52 8.44 8.54 8.78 8.28 8.64 8.81 8.78 8.70 8.48 8.70 8.96 8.40 8.80 8.79 8.60 8.58 8.59 8.65 8.38 8.78 8.60 8.64	K 2 O 0.25 0.23 0.21 0.11 0.25 0.22 0.16 0.19 0.14 0.16 0.22 0.22 0.22 0.15 0.18 0.24 0.22 0.18 0.22 0.32 0.11 0.25 0.30 S 6	Total 98.88 100.23 100.94 100.30 99.92 99.65 100.96 100.13 100.63 100.62 100.38 101.27 100.22 99.58 101.40 100.42 100.79 101.14 100.72 100.51 100.17 100.48 100.62 S 7	Si 2.76 2.76 2.75 2.76 2.76 2.76 2.74 2.75 2.76 2.74 2.75 2.75 2.75 2.77 2.75 2.75 2.76 2.73 2.73 2.75 2.75 2.75 2.76 S 8 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00	Al 1.23 1.24 1.25 1.23 1.24 1.23 1.25 1.24 1.24 1.26 1.25 1.24 1.24 1.22 1.24 1.23 1.23 1.26 1.26 1.24 1.23 1.24 1.22 S 9	Fe(ii) 0.01 0.00 0.01 0.00 0.01 0.00 0.00 0.01 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.01 0.01 0.01 0.00 0.01 0.00 0.01 0.00	Ca 0.24 0.25 0.26 0.25 0.25 0.24 0.26 0.25 0.25 0.26 0.25 0.25 0.26 0.25 0.27 0.27 0.26 0.28 0.28 0.27 0.26 0.27 0.27 S 10	Na 0.74 0.72 0.73 0.75 0.71 0.75 0.75 0.75 0.74 0.72 0.75 0.76 0.72 0.76 0.75 0.74 0.73 0.73 0.74 0.72 0.75 0.74 0.74	K 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.01 0.01 0.02 S 11	Total 5.00 4.99 5.00 5.00 4.98 5.00 5.01 5.01 5.00 5.00 5.01 5.02 4.99 5.01 5.01 5.01 5.00 5.01 5.02 5.00 5.01 5.01 5.01 S 12	An 24.39 25.71 25.73 24.52 25.92 24.19 25.40 24.33 25.02 26.24 24.99 24.73 26.47 24.71 26.10 26.74 26.11 27.43 26.85 26.60 25.69 26.07 26.12 S 13 Ab 74.16 72.99 73.11 74.85 72.61 74.56 73.73 74.61 74.21 72.85 73.78 74.08 72.28 74.47 72.89 71.94 72.67 71.59 71.93 71.59 73.68 72.52 72.23	Or 1.44 1.29 1.16 0.63 1.47 1.24 0.86 1.06 0.77 0.91 1.23 1.19 1.25 0.82 1.00 1.32 1.22 0.97 1.22 1.81 0.62 1.65 1.40 S 14	S 15	S 16	S 17	S 18

  2.00 Total 19.51 19.54 19.52 19.56 19.50 19.54 19.55 19.57 19.65 19.55 19.53 19.54 19.51 19.54 19.52 19.52 19.50 SiO 2 62.62 62.59 62.79 62.39 62.41 62.62 62.57 62.71 62.41 62.67 62.59TiO 2 0.00 0.00 0.00 0.12 0.00 0.00 0.00 0.00 0.00 0.00 0.00Al 2 O 3 23.92 24.05 24.20 23.65 23.94 23.77 24.03 23.88 23.80 23.91 23.70

	Plagioclase
	S 2	S 3	S 4	S 5	S 6	S 7	S 8	S 9	S 10	S 11	S 12

  207 Pb/ 206 Pb dates of 1557 ± 21 Ma (conc.: 95%, a525) and 1773 ± 12 Ma (conc.: 82%, a509). Nineteen other spots were discordant. Those performed on zircon cores show a range of 206 Pb/ 238 U dates spanning between 853 ± 12 (a529) and 566 ± 10 Ma (a584). Discordant rims and core-free grains have younger 206 Pb/ 238 U dates, from 565 ± 8 (a513) down to 505 ± 8 Ma (a484). A range of cores, rims and core-free grains yielded concordant 206 Pb/ 238 U dates between 974 ± 14 (a490) and 542 ± 8 Ma (a493) once again clustering around 555545 Ma.

Table B4 :

 B4 Results of LAICPMS UPb analyses of zircon standards performedduring the sessions at GUF, 2nd and 3rd ofMay, 2016;

Table B5 :

 B5 Results of LAICPMS UPb analyses of zircon standards performedduring the session at SUN, 26th of October, 2016;

Table B6 :

 B6 Results of LAICPMS UPb analyses of zircon standards performedduring the sessions at ETH Zürich, 12 to 14th of February, 2017.

	Analyses of zircon grains from investigated samples can be found in the following
	tables:

Table B7 :

 B7 Results of LAICPMS zircon UPb analyses performed during the sessions at GUF, 2nd and 3rd ofMay, 2016;

Table B8 :

 B8 Results of LAICPMS zircon UPb analyses performed during the session at SUN, 26th of October, 2016;

Table B9 :

 B9 Results of LAICPMS zircon UPb analyses performed during the sessions at ETH Zürich, 12 to 14th of February, 2017.

Table B4 :

 B4 Results of LA-ICP-MS U-Pb analyses of zircon standards performed during the sessions at SUN, 26 th

	of October, 2016
	grain 207 Pb a	U/ 206 Pb*1/137.88)	rho is the 206 Pb/ 238 U/ 207 Pb/ 235 U error correlation coefficient.	degree of concordance = 206 Pb/ 206 Pb age x 100 Pb/ 238 U age / 207
			e	f

Table B7 : Results of LA-ICP-MS zircon U-Pb analyses performed during the sessions at GUF, 2nd and 3rd of May, 2016

 B7

		U) and subsequently normalised to GJ-1 (ID-TIMS value/measured value);
		Pb/ 238
	grain 207 Pb a	(in case of 206	207 Pb/ 235 U obtained from signal measured on masses 207 and 235	d rho is the 206 Pb/ 238 U/ 207 U error correlation coefficient. Pb/ 235	e U age / 207 Pb/ 206 Pb age x 100 Pb/ 238 degree of concordance = 206

Table B7 (continued): Results of LA-ICP-MS zircon U-Pb analyses performed during the sessions at GUF, 2nd and 3rd of May, 2016

 B7

	Spot size = 20 and 30µm; depth of crater ~20µm. 206 Pb/ 238 U error is the quadratic additions of the within run precision (2 SE)	and the external reproducibility (2 SD) of the reference zircon.	Pb/ Pb error propagation ( Pb signal dependent) following Gerdes & Zeh (2009). Pb/ U error is the quadratic addition of the Pb/ Pb and Pb/ U uncertainty.	corrected for background, within-run Pb/U fractionation (in case of 206 Pb/ 238 U), common Pb using Stacy and Kramers (1975) model Pb composition (specified by a *,	Pb*1/137.88) U/ 206 Pb/( 238 Pb/ 206 U calculated using 207 Pb/ 235 see text for discussion) and subsequently normalised to GJ-1 (ID-TIMS value/measured value); 207	e rho is the 206 Pb/ 238 U/ 207 Pb/ 235 U error correlation coefficient.	f degree of concordance = 206 Pb/ 238 U age / 207 Pb/ 206 Pb age x 100

a Within run background-corrected mean 207 Pb signal in cps (counts per second). b U and Pb content and Th/U ratio were calculated relative to GJ-1 reference zircon. c percentage of the common Pb on the 206 Pb. b.d. = below dectection limit. d g Zone of the grain on which the analysis was performed. C: core; r(1 or 2): rim (internal or external corona); h: grain devoid of core-rim relationship.

Table B8 :

 B8 Results of LA-ICP-MS zircon U-Pb analyses performed during the session at SUN, 26 th

	of October, 2016 Table B8 (cont.): Results of LA-ICP-MS zircon U-Pb analyses performed during the session at SUN, 26 th of October, 2016	grain 207 Pb a U b Pb b Th b 206 Pb d ±2s 207 Pb d ±2s 207 Pb d ±2s rho e 206 Pb ±2s 207 Pb ±2s 207 Pb ±2s conc. f grain 207 Pb a U b Pb b Th b 206 Pb d ±2s 207 Pb d ±2s 207 Pb d ±2s rho e 206 Pb ±2s 207 Pb ±2s 207 Pb ±2s conc. f (cps) (ppm) (ppm) (cps) (ppm) (ppm) U U (%) U (%) Pb (%) U (Ma) U (Ma) Pb (Ma) (%) U 238 U (%) 235 U (%) 206 Pb (%) 238 U (Ma) 235 U (Ma) 206 Pb (Ma) (%)	RV-3 Riverie biotite granite 30 58 b193 14110 8071 385 0.06 0.05059 1.9 0.40846 2.3 0.05856 1.4 0.81 318 6 348 7 551	b133 9547 5346 270 0.05 0.05322 1.9 0.43795 2.7 0.05968 2.0 0.69 334 6 369 8 592 43 56 12 100 b194 111082 77519 3801 0.03 0.05323 1.9 0.39008 2.0 0.05315 0.5 0.96 334 6 334 6 335	b134 17491 10619 577 0.28 0.05386 1.7 0.39825 1.9 0.05363 0.8 0.89 338 6 340 5 356 19 95 50 79 b195 10084 6195 343 0.07 0.05868 1.8 0.45569 2.9 0.05632 2.3 0.62 368 6 381 9 465	b135 21528 12899 642 0.03 0.05179 1.7 0.48040 3.8 0.06727 3.4 0.46 326 6 398 13 846 71 38 35 59 b196 18257 10403 542 0.12 0.05369 2.2 0.43829 2.7 0.05921 1.6 0.80 337 7 369 8 575	b136 30319 18140 993 0.32 0.05318 1.8 0.40612 2.2 0.05539 1.3 0.82 334 6 346 7 428 28 78 29 56 b197 25485 14224 695 0.08 0.05150 1.9 0.42028 2.3 0.05919 1.3 0.81 324 6 356 7 574	b137 34427 12520 652 0.30 0.04984 2.3 0.46997 6.3 0.06839 5.9 0.36 314 7 391 21 880 121 36 26 36 b198 36718 20512 987 0.04 0.04926 1.8 0.45842 2.2 0.06750 1.3 0.81 310 5 383 7 853	b140 32621 13748 794 0.38 0.05452 1.8 0.46328 6.0 0.06163 5.7 0.31 342 6 387 19 661 122 52 35 60 b199 12502 7521 380 0.04 0.05352 1.8 0.43336 2.4 0.05872 1.6 0.74 336 6 366 7 557	b141 27023 10112 545 0.04 0.05016 2.1 0.67139 20.8 0.09708 20.7 0.10 315 6 522 89 1569 388 20	b142 18185 7554 385 0.07 0.04739 2.4 0.61713 7.9 0.09445 7.5 0.30 298 7 488 31 1517 142 20 Spot size = 30µm; depth of crater ~20µm. 206 b143 11500 4770 232 0.04 0.04415 2.2 0.67102 21.7 0.11023 21.6 0.10 278 6 521 93 1803 393 15 Pb/ 238 Pb/ 238 b144 26509 16532 828 0.15 0.05127 1.8 0.40072 2.4 0.05669 1.5 0.77 322 6 342 7 479 33 67 U uncertainty. U error is the quadratic additions of the within run precision (2 SE) and the external reproducibility (2 SD) of the reference zircon. 207 Pb/ 206 Pb error propagation ( 207 Pb/ 235 U error is the quadratic addition of the 207 Pb/ 206 Pb and 206 Pb signal dependent) following Gerdes & Zeh (2009). 207	b145 35042 16000 755 0.07 0.04497 1.7 0.50418 2.3 0.08132 1.6 0.74 284 5 415 8 1229 31 23	b146 16647 9957 493 0.03 0.05283 1.9 0.41763 2.4 0.05734 1.4 0.79 332 6 354 7 505 31 66	b147 18089 11390 580 0.03 0.05409 1.9 0.44179 2.5 0.05924 1.7 0.75 340 6 372 8 576 36 59 Pb/ 238 b148 32796 20805 1052 0.13 0.05284 1.9 0.39738 2.4 0.05455 1.5 0.79 332 6 340 7 394 34 84 U) and subsequently normalised to GJ-1 (ID-TIMS value/measured value); corrected for background, within-run Pb/U fractionation (in case of 206	b149 25554 12004 714 0.49 0.05170 1.8 0.51814 2.3 0.07269 1.4 0.80 325 6 424 8 1005 28 32 207 Pb/ 235 U calculated using 207 Pb/ 206 Pb/( 238 U/ 206 Pb*1/137.88)	b151 35034 24038 1128 0.08 0.04954 2.1 0.37016 2.2 0.05419 0.9 0.92 312 6 320 6 379 19 82 d rho is the 206 b158 27184 18222 863 0.08 0.04800 1.8 0.48788 2.3 0.07371 1.5 0.77 302 5 403 8 1034 30 29 e Pb/ 238 U/ 207 degree of concordance = 206 b159 26522 15845 761 0.07 0.05043 2.2 0.40872 3.3 0.05878 2.5 0.67 317 7 348 10 559 54 57 Pb/ 235 Pb/ 238 U age / 207 Pb/ 206 U error correlation coefficient. Pb age x 100	b160 11551 5050 302 0.08 0.06263 2.6 0.50215 3.0 0.05815 1.5 0.87 392 10 413 10 535 32 73	b161 31200 18439 868 0.06 0.04958 1.9 0.38801 2.6 0.05675 1.8 0.74 312 6 333 7 482 39 65	b162 72383 43491 2201 0.04 0.05441 1.9 0.41133 2.0 0.05483 0.8 0.92 342 6 350 6 405 18 84	b163 51294 37384 1851 0.03 0.05363 1.7 0.39755 1.9 0.05376 0.8 0.90 337 6 340 5 361 18 93	b164 65853 41061 2227 0.37 0.05008 2.0 0.41461 2.4 0.06004 1.3 0.84 315 6 352 7 605 27 52	b165 46084 22763 1273 0.35 0.05383 2.1 0.41053 2.6 0.05531 1.6 0.79 338 7 349 8 425 36 80	b166 26224 16582 821 0.20 0.05033 2.1 0.39778 2.4 0.05732 1.2 0.86 317 6 340 7 504 27 63	b167 21739 14501 708 0.20 0.04932 1.7 0.36667 2.4 0.05392 1.7 0.70 310 5 317 7 368 39 84	b168 23900 12411 644 0.03 0.05386 2.0 0.49141 3.3 0.06617 2.6 0.62 338 7 406 11 812 54 42	b169 24605 10394 524 0.07 0.05345 1.9 0.40502 2.3 0.05496 1.3 0.82 336 6 345 7 411 29 82	b171 16701 11324 548 0.25 0.04814 2.1 0.36794 2.6 0.05543 1.4 0.83 303 6 318 7 430 31 71	b174 30654 22394 1122 0.14 0.05181 1.9 0.40307 2.1 0.05643 1.0 0.87 326 6 344 6 469 23 69	b175 53276 30263 1526 0.04 0.05198 1.9 0.47370 2.3 0.06610 1.3 0.82 327 6 394 8 809 28 40	b176 27421 16353 812 0.08 0.05065 1.7 0.45860 2.5 0.06566 1.8 0.69 319 5 383 8 796 38 40	b177 67155 49422 1970 0.08 0.04128 2.1 0.33793 2.3 0.05938 1.1 0.88 261 5 296 6 581 24 45	b178 21227 12864 633 0.10 0.05129 1.7 0.41470 2.3 0.05864 1.5 0.75 322 5 352 7 554 33 58	b179 28950 16928 851 0.07 0.05274 1.8 0.42438 2.1 0.05835 1.1 0.84 331 6 359 6 543 24 61	b180 30017 18535 901 0.12 0.05049 2.4 0.38720 2.7 0.05562 1.2 0.90 318 7 332 8 437 26 73	b181 43885 21811 1044 0.07 0.04750 1.9 0.48952 2.7 0.07475 1.9 0.72 299 6 405 9 1062 38 28	b182 22867 7214 419 0.08 0.05330 2.0 0.64497 4.5 0.08777 4.0 0.46 335 7 505 18 1377 77 24	b183 15901 8369 413 0.09 0.05174 1.9 0.40435 3.0 0.05668 2.4 0.61 325 6 345 9 479 53 68	b184 11243 5084 265 0.05 0.05207 1.8 0.51151 7.0 0.07125 6.7 0.26 327 6 419 24 964 137 34	b185 21559 8955 656 0.24 0.07262 1.7 0.61222 2.2 0.06114 1.4 0.78 452 7 485 8 644 29 70	b186 20081 9821 565 0.10 0.05982 1.8 0.46361 2.0 0.05621 1.0 0.87 375 6 387 6 461 22 81	b187 37241 18463 910 0.06 0.05028 1.8 0.46096 3.1 0.06649 2.5 0.59 316 6 385 10 822 52 38	b188 19084 15813 776 0.06 0.05161 2.0 0.44532 2.8 0.06258 1.9 0.72 324 6 374 9 694 41 47	b191 24835 21106 1051 0.03 0.05398 1.8 0.40150 2.1 0.05395 1.0 0.87 339 6 343 6 369 23 92	b192 10549 4862 259 0.10 0.05199 2.1 0.53418 3.1 0.07452 2.3 0.67 327 7 435 11 1056 46 31

a Within run background-corrected mean 207 Pb signal in cps (counts per second). b U and Pb content and Th/U ratio were calculated relative to GJ-1 reference zircon. c

Table B9 : Results of LA-ICP-MS zircon U-Pb analyses performed during the sessions at ETH Zürich, 12 to 14th of February, 2017

 B9

	Pb a
	207
	grain

  (in case of 206 Pb/ 238 U) and subsequently normalised to GJ-1 (ID-TIMS value/measured value);

	B.4 Zircon Hf isotope compositions
	B.4.1 Analytical details on the GUF session
	207 Pb/ 235 U obtained from signal measured on masses 207 and 235	d rho is the 206 Pb/ 238 U/ 207 Pb/ 235 U error correlation coefficient.	e degree of concordance = 206 Pb/ 238 U age / 207 Pb/ 206 Pb age x 100

  ). 176 Y b calculated = 173 Y b measured × 176 Lu calculated = 175 Lu measured × Both determined 176 Lu and 176 Yb signals were subtracted from the total 176 signal intensity and the calculated 176 Hf signal were used to determine the mass biais using the true 179 Hf/ 177 Hf ratio of 0.7325 (Patchett and Tatsumoto, 1980), following the equation : Finally the interference corrected 176 Hf/ 177 Hf is evaluated according to the following equation: 176 Hf 177 Hf corrected = 176 (Hf + Y b + Lu) meas -176 Y b calc -176 Lu calc 177 Hf meas

						×	M 177 M 176	β(Hf )
						(B.5)
			176 Y b 173 Y b ref	×	M 173 M 176	β(Y b)	(B.2)
			176 Lu 175 Lu ref	×	M 175 M 176	β(Y b)	(B.3)
	β Hf =	ln	179 Hf / 177 Hf ref 179 Hf / 177 Hf meas M 177 ln M 179			(B.4)

Table B10 :

 B10 Operating conditions and instrument settings for Hf analyses B.4.3 Data tables This section provides the results of zircon LAMCICPMS LuHf isotope measurements. The data are reported in the following tables:

Table B11 :

 B11 In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon standards analyzed at GUF, 1st of August, 2016;

Table B12 :

 B12 results for amphibole-bearing gneisses sampled at the Riverie quarry, see section 3.5.

Table B13 :

 B13 results of analyses conducted on zircon standards during the analytical session performed at LMV.

Table B14 :

 B14 results of analyses conducted on zircon grains from investigated samples during the analytical session performed at LMV.

Table B11 :

 B11 In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon standards analysed at GUF, 1st of August, 2016

	176
	Spot size

  Hf were calculated in a similar way by using the 175Lu/177Hf and b(Yb).(d) two stage model age in billion years using the measured 176 Lu/ 177 Lu of each spot (first stage = age of zircon), a value of 0.0113 for the average continental crust (second stage), and a juvenile crust (NC) 176

	measured )/ ln (M 179(Hf )/M 177(Hf) ), M=mass of respective isotope.
	Hf
	Hf/
	Yb/ Hf) meas x (M 173(Yb) /M 177(Hf) ) b(Hf) , b(Hf) = ln( Hf/ Hf true /	Lu/ 177 Lu and 176 Hf/ 177 Hf of 0.0384 and 0.28314, respectively.
	Yb) true x (
	Yb/
	a) Yb/ Hf = (	The 176 Lu/ 177

Table B12 :

 B12 In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon grains from amphibole-bearing gneisses analyzed at GUF, 1 st

		f
		Naeraa
		DM
		e
		Griffin
		DM
		±2σ
		d
		εHf (t)
	of August, 2016	±2σ Intrusion ±2σ 176 Hf d	(abs.) age (Ma) (Ma) 177 Hf (t int)
		c
		εHf (app)
		±2σ Apparent ±2σ Conc. 176 Hf c	(abs.) age (Ma) (Ma) (%) 177 Hf App
		Hf	Hf
		176	177
		b
		Sig Hf	(V)
		±2σ	(abs.)
		Hf	Hf
		180	177
		±2σ	(abs.)
		Hf	Hf
		178	177
		±2σ	(abs.)
		176 Lu a	177 Hf
		±2σ	(abs.)
		176 Yb a	177 Hf

Table B14 :

 B14 In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon grains from meta-sediments analysed at LMV, 7th of June, 2017

	Hf/ Hf(T) e Hf (T) 2σ	0.282481 4.5 0.9	0.282541 7.6 0.5	0.282529 5.1 1.0	0.282378 -1.5 0.9	0.282674 9.3 0.7	0.282600 12.3 0.9	0.282513 3.9 0.8	0.282313 -3.4 1.0	0.282678 10.1 1.0	0.282476 3.4 0.9	0.282499 3.8 1.1	0.282461 2.7 0.8	0.282520 4.9 0.7	0.282467 2.7 0.8	0.281974 -16.1 0.7	0.282472 11.0 1.0	0.282358 -1.5 0.7	0.281944 -16.9 1.0	0.282286 -2.0 0.8	0.282617 8.4 1.1	0.281044 0.2 0.8	0.282381 -0.9 0.7	0.282290 -3.3 0.8	0.282711 12.7 0.8	0.282492 6.9 0.8	0.281527 4.1 0.8	0.282530 5.1 1.1	0.282513 4.2 0.7	0.281029 -2.0 0.7	0.282396 9.9 0.7	0.282540 4.9 0.9	0.282266 -4.8 0.7	0.282188 0.5 1.2	0.282616 8.3 0.7	0.281080 1.2 0.6
	2 SE Age 2σ	0.00177 682 7	0.00009 727 5	0.00169 635 5	0.00201 578 8	0.00060 594 6	0.00115 844 8	0.00172 606 5	0.00128 597 8	0.00044 622 6	0.00230 644 6	0.00144 622 5	0.00057 635 5	0.00036 639 6	0.00200 623 7	0.00054 565 4	0.00074 986 7	0.00146 610 6	0.00069 579 5	0.00131 701 6	0.00202 641 5	0.00013 2718 10	0.00016 600 5	0.00106 636 9	0.00180 683 7	0.00050 771 6	0.00460 2149 12	0.00109 632 6	0.00076 617 5	0.00045 2645 18	0.00119 1058 9	0.00024 609 5	0.00003 608 5	0.00400 964 7	0.00185 640 5	0.00060 2705 9
	Yb/ Hf	0.03874	0.01910	0.03836	0.02613	0.01659	0.06561	0.03393	0.05026	0.03571	0.06799	0.04545	0.03270	0.01186	0.04633	0.02085	0.05377	0.02984	0.03016	0.04108	0.04406	0.03495	0.01759	0.02193	0.03734	0.01996	0.04326	0.03397	0.02107	0.01694	0.01652	0.01971	0.01088	0.06568	0.04766	0.03927
	2 SE	0.000056	0.000001	0.000036	0.000056	0.000019	0.000023	0.000039	0.000038	0.000005	0.000072	0.000048	0.000029	0.000015	0.000059	0.000016	0.000028	0.000041	0.000022	0.000018	0.000072	0.000010	0.000003	0.000025	0.000061	0.000022	0.000111	0.000034	0.000019	0.000012	0.000049	0.000008	0.000001	0.000113	0.000049	0.000008
	Spot Hf/ Hf 2 SE Hf/ Hf 2 SE Lu/ Hf	E-CHA16 #1-94 0.282497 0.000025 1.467257 0.000042 0.001248	E-CHA16 #2-93 0.282549 0.000016 1.467242 0.000050 0.000600	E-CHA16 #3-96 0.282544 0.000027 1.467274 0.000050 0.001249	E-CHA16 #4-97 0.282387 0.000027 1.467272 0.000038 0.000851	E-CHA16 #5-100 0.282680 0.000019 1.467303 0.000041 0.000496	E-CHA16 #6-105 0.282630 0.000025 1.467271 0.000043 0.001916	E-CHA16 #7-104 0.282525 0.000023 1.467291 0.000033 0.001080	E-CHA16 #8-a109 0.282330 0.000027 1.467285 0.000037 0.001569	E-CHA16 #9-110 0.282691 0.000029 1.467246 0.000046 0.001145	E-CHA16 #10-209 0.282504 0.000026 1.467245 0.000053 0.002318	E-CHA16 #11-111 0.282516 0.000032 1.467230 0.000039 0.001392	E-CHA16 #12-118 0.282474 0.000024 1.467282 0.000035 0.001154	E-CHA16 #13-123 0.282525 0.000020 1.467278 0.000034 0.000434	E-CHA16 #14-124 0.282484 0.000024 1.467253 0.000040 0.001460	E-CHA16 #15-127 0.281981 0.000019 1.467269 0.000039 0.000629	E-CHA16 #16-128 0.282503 0.000027 1.467286 0.000049 0.001684	E-CHA16 #17-129 0.282369 0.000020 1.467249 0.000035 0.000967	E-CHA16 #18-135 0.281955 0.000027 1.467281 0.000039 0.000964	E-CHA16 #19-137 0.282304 0.000023 1.467293 0.000041 0.001378	E-CHA16 #20-140 0.282635 0.000032 1.467237 0.000040 0.001464	E-CHA16 #21-142 0.281099 0.000023 1.467259 0.000033 0.001071	E-CHA16 #22-146 0.282387 0.000019 1.467237 0.000054 0.000551	E-CHA16 #23-154 0.282298 0.000023 1.467260 0.000033 0.000654	E-CHA16 #24-156 0.282729 0.000024 1.467325 0.000028 0.001346	E-CHA16 #25-157 0.282503 0.000023 1.467288 0.000037 0.000738	E-CHA16 #26-163 0.281579 0.000022 1.467227 0.000045 0.001278	E-CHA16 #27-165 0.282543 0.000030 1.467309 0.000050 0.001114	E-CHA16 #28-167 0.282522 0.000020 1.467278 0.000027 0.000714	E-CHA16 #29-168 0.281055 0.000021 1.467277 0.000035 0.000521	E-CHA16 #30-175 0.282408 0.000019 1.467292 0.000035 0.000632	E-CHA16 #31-176 0.282548 0.000025 1.467300 0.000037 0.000691	E-CHA16 #32-179 0.282269 0.000020 1.467262 0.000036 0.000314	E-CHA16 #33-178 0.282225 0.000035 1.467281 0.000043 0.002006	E-CHA16 #34-180 0.282635 0.000020 1.467273 0.000041 0.001556	E-CHA16 #35-181 0.281142 0.000018 1.467284 0.000039 0.001198

Table B14 (

 B14 continued): In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon grains from meta-sediments analysed at LMV, 7th of June, 2017

	Hf/ Hf(T) e Hf (T) 2σ	0.282261 -5.1 0.6	0.282467 2.8 0.8	0.282335 -2.8 0.5	0.282503 2.8 0.7	0.282319 4.2 0.7	0.282369 -0.5 0.8	0.282371 -0.9 0.7	0.282647 11.4 0.8	0.282655 10.9 1.0	0.281481 -1.8 0.9	0.282635 9.2 0.6	0.282679 10.5 0.8	0.282646 13.0 1.0	0.282410 4.7 0.9	0.282038 -12.1 0.6	0.282692 12.5 0.8	0.282639 11.5 0.7	0.282605 12.8 0.8	0.282664 10.3 0.7	0.281088 -4.8 0.7	0.282466 8.2 0.8	0.282677 11.6 0.9	0.282620 11.5 0.8	0.282622 12.4 1.4	0.282598 9.8 0.8	0.282200 1.2 1.1	0.282677 9.3 0.6	0.282133 -1.8 0.6	0.280972 -5.6 0.6	0.282566 5.8 0.6	0.282528 7.8 0.7	0.282543 9.3 0.9	0.282554 8.0 0.8	0.282353 0.2 0.9
	2 SE Age 2σ	0.00025 601 5	0.00266 630 5	0.00014 591 7	0.00080 571 4	0.00133 925 15	0.00223 636 6	0.00103 618 5	0.00045 731 8	0.00188 693 7	0.00125 1966 10	0.00082 650 7	0.00146 637 6	0.00492 800 8	0.00087 804 8	0.00040 643 7	0.00278 706 9	0.00057 747 8	0.00121 857 10	0.00106 652 7	0.00018 2437 8	0.00089 870 8	0.00187 691 7	0.00088 776 8	0.00427 814 8	0.00054 736 7	0.00165 978 11	0.00049 590 6	0.00089 952 10	0.00015 2581 8	0.00171 607 6	0.00042 756 7	0.00036 798 8	0.00174 723 7	0.00045 696 7
	Yb/ Hf	0.02099	0.06197	0.01146	0.02523	0.03230	0.04263	0.02806	0.03608	0.05068	0.10743	0.04350	0.02894	0.05327	0.02930	0.03744	0.04310	0.02251	0.02373	0.02650	0.01839	0.03401	0.04107	0.04256	0.08423	0.03241	0.06447	0.02348	0.03794	0.01375	0.04989	0.04222	0.03152	0.06161	0.02474
	Spot Hf/ Hf 2 SE Hf/ Hf 2 SE Lu/ Hf 2 SE	E-CHA16 #36-183 0.282269 0.000016 1.467282 0.000028 0.000731 0.000003	E-CHA16 #37-189 0.282490 0.000022 1.467237 0.000040 0.001957 0.000078	E-CHA16 #38-192 0.282338 0.000015 1.467272 0.000038 0.000342 0.000005	E-CHA16 #39-198 0.282511 0.000019 1.467270 0.000040 0.000729 0.000026	E-CHA16 #40-195 0.282337 0.000020 1.467266 0.000042 0.001076 0.000045	E-CHA16 #41-203 0.282386 0.000021 1.467295 0.000047 0.001403 0.000078	E-CHA16 #42-207 0.282382 0.000021 1.467276 0.000045 0.000948 0.000035	H-PdB16 #1-199 0.282662 0.000021 1.467269 0.000049 0.001101 0.000015	H-PdB16 #2-7 0.282676 0.000028 1.467253 0.000031 0.001571 0.000051	H-PdB16 #3-8 0.281612 0.000026 1.467196 0.000046 0.003527 0.000073	H-PdB16 #4-9 0.282651 0.000018 1.467246 0.000031 0.001278 0.000017	H-PdB16 #5-11 0.282690 0.000022 1.467284 0.000029 0.000912 0.000034	H-PdB16 #6-15 0.282672 0.000027 1.467281 0.000029 0.001727 0.000158	H-PdB16 #7-19 0.282425 0.000027 1.467255 0.000034 0.000974 0.000028	H-PdB16 #8-20 0.282052 0.000018 1.467255 0.000035 0.001131 0.000023	H-PdB16 #9-21 0.282709 0.000022 1.467252 0.000035 0.001316 0.000090	H-PdB16 #10-24 0.282649 0.000021 1.467261 0.000043 0.000719 0.000023	H-PdB16 #11-41 0.282617 0.000023 1.467273 0.000025 0.000750 0.000030	H-PdB16 #12-45 0.282674 0.000019 1.467273 0.000041 0.000858 0.000032	H-PdB16 #13-57 0.281114 0.000019 1.467226 0.000042 0.000557 0.000006	H-PdB16 #14-50 0.282487 0.000022 1.467246 0.000044 0.001282 0.000038	H-PdB16 #15-63 0.282696 0.000024 1.467265 0.000031 0.001487 0.000063	H-PdB16 #16-68 0.282642 0.000023 1.467235 0.000048 0.001517 0.000040	H-PdB16 #17-81 0.282660 0.000040 1.467256 0.000038 0.002500 0.000135	H-PdB16 #18-85 0.282613 0.000023 1.467238 0.000038 0.001054 0.000014	H-PdB16 #19-90 0.282237 0.000031 1.467290 0.000036 0.0019890 0.0000430	H-PdB16 #20-92 0.282686 0.000018 1.467228 0.000041 0.0008300 0.0000196	H-PdB16 #21-94 0.282154 0.000018 1.467212 0.000043 0.0011679 0.0000397	H-PdB16 #22-96 0.280993 0.000016 1.467258 0.000035 0.0004329 0.0000020	H-PdB16 #23-98 0.282582 0.000017 1.467225 0.000030 0.0014609 0.0000531	H-PdB16 #24-100 0.282550 0.000021 1.467195 0.000033 0.0015456 0.0000120	H-PdB16 #25-102 0.282560 0.000026 1.467274 0.000040 0.0010991 0.0000041	H-PdB16 #26-105 0.282580 0.000023 1.467215 0.000043 0.0019133 0.0000357	H-PdB16 #27-106 0.282362 0.000025 1.467241 0.000042 0.0007310 0.0000165

Table B16 (

 B16 continued): In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon grains from meta-sediments analysed at LMV, 7th of June, 2017

	Hf/ Hf(T) e Hf (T) 2σ	0.282533 7.3 0.7	0.282677 10.0 0.7	0.282651 9.5 0.8	0.281638 -18.7 1.1	0.282027 -12.3 1.3	0.282741 12.7 0.9	0.282651 12.0 1.0	0.282528 4.4 0.7	0.282653 9.4 1.1	0.282566 11.4 0.8	0.282745 12.2 1.1	0.282659 9.4 0.7	0.282596 10.2 1.1	0.282756 13.7 1.0	0.281256 2.6 0.7	0.281542 -1.9 0.9	0.282548 5.6 1.1	0.280996 -0.4 0.7	0.282675 8.7 1.4	0.282310 -3.2 1.0	0.282497 4.0 0.8	0.282610 7.9 1.0	0.282597 8.2 1.0	0.282394 4.6 0.8	0.282309 -2.3 0.7	0.281164 1.6 0.8	0.281308 -7.4 0.8	0.282296 -4.2 0.8	0.282536 5.4 0.9	0.282248 -5.6 0.8	0.282084 -10.5 0.8	0.282651 7.6 0.9	0.281116 4.1 0.8	0.281505 -0.2 1.1
	2 SE Age 2σ	0.00051 724 7	0.00063 620 6	0.00033 638 6	0.00084 978 10	0.00407 651 7	0.00052 641 7	0.00129 749 8	0.00015 606 5	0.00295 630 11	0.00127 855 13	0.00028 610 6	0.00292 622 8	0.00299 755 8	0.00143 658 6	0.00112 2498 10	0.00332 1866 11	0.00119 629 8	0.00083 2763 18	0.00376 564 7	0.00076 612 7	0.00130 637 6	0.00159 632 6	0.00077 666 7	0.00072 823 8	0.00140 651 7	0.00117 2596 11	0.00012 1989 23	0.00149 587 6	0.00278 637 6	0.00117 600 6	0.00125 641 6	0.00236 555 8	0.00063 2773 14	0.00126 1994 15
	Yb/ Hf	0.02163	0.06197	0.03452	0.05693	0.04371	0.03206	0.01708	0.00658	0.02679	0.03344	0.05046	0.02915	0.07757	0.04128	0.03237	0.04325	0.03089	0.02144	0.03696	0.03309	0.05078	0.03460	0.03649	0.02392	0.03843	0.03504	0.01107	0.05577	0.03262	0.03622	0.02248	0.04360	0.04679	0.03413
	Spot Hf/ Hf 2 SE Hf/ Hf 2 SE Lu/ Hf 2 SE	H-PdB16 #28-107 0.282542 0.000021 1.467178 0.000036 0.0006679 0.0000084	H-PdB16 #29-195 0.282699 0.000020 1.467166 0.000041 0.0018612 0.0000078	H-PdB16 #30-117 0.282663 0.000024 1.467254 0.000032 0.0010600 0.0000086	H-PdB16 #31-118 0.281675 0.000032 1.467290 0.000043 0.0020242 0.0000335	H-PdB16 #32-120 0.282044 0.000037 1.467238 0.000043 0.0014341 0.0001316	H-PdB16 #33-122 0.282754 0.000025 1.467226 0.000039 0.0011027 0.0000115	H-PdB16 #34-124 0.282661 0.000028 1.467268 0.000042 0.0006746 0.0000503	H-PdB16 #35-125 0.282530 0.000019 1.467259 0.000039 0.0001590 0.0000067	H-PdB16 #36-128 0.282662 0.000031 1.467282 0.000034 0.0008056 0.0000881	H-PdB16 #37-130 0.282583 0.000022 1.467224 0.000045 0.0010455 0.0000342	H-PdB16 #38-131 0.282763 0.000031 1.467223 0.000035 0.0016061 0.0000199	H-PdB16 #39-138 0.282670 0.000021 1.467237 0.000058 0.0009571 0.0000921	H-PdB16 #40-137 0.282627 0.000032 1.467264 0.000036 0.0021801 0.0000650	H-PdB16 #41-123 0.282773 0.000028 1.467243 0.000043 0.0014087 0.0000497	H-PdB16 #42-144 0.281309 0.000021 1.467312 0.000040 0.0011122 0.0000414	H-PdB16 #43-167 0.281590 0.000024 1.467248 0.000036 0.001356 0.000113	H-PIL16 #1-9 0.282559 0.000030 1.467184 0.000034 0.000943 0.000041	H-PIL16 #2-18 0.281028 0.000021 1.467232 0.000040 0.000602 0.000022	H-PIL16 #3-19 0.282686 0.000039 1.467157 0.000053 0.001075 0.000111	H-PIL16 #4-22 0.282320 0.000027 1.467298 0.000033 0.000918 0.000014	H-PIL16 #5-15 0.282514 0.000022 1.467230 0.000061 0.001418 0.000034	H-PIL16 #6-17 0.282622 0.000028 1.467272 0.000037 0.000995 0.000039	H-PIL16 #7-30 0.282611 0.000029 1.467230 0.000035 0.001170 0.000025	H-PIL16 #8-29 0.282405 0.000024 1.467252 0.000042 0.000754 0.000018	H-PIL16 #9-34 0.282323 0.000021 1.467234 0.000029 0.001196 0.000035	H-PIL16 #10-33 0.281218 0.000022 1.467211 0.000026 0.001073 0.000028	H-PIL16 #11-35 0.281318 0.000022 1.467292 0.000036 0.000279 0.000001	H-PIL16 #12-36 0.282314 0.000024 1.467244 0.000049 0.001597 0.000037	H-PIL16 #13-39 0.282549 0.000027 1.467248 0.000037 0.001110 0.000094	H-PIL16 #14-48 0.282260 0.000022 1.467209 0.000044 0.001102 0.000036	H-PIL16 #15-79 0.282092 0.000024 1.467309 0.000034 0.000694 0.000040	H-PIL16 #16-84 0.282664 0.000027 1.467254 0.000043 0.001318 0.000080	H-PIL16 #17-87 0.281195 0.000023 1.467265 0.000042 0.001480 0.000012	H-PIL16 #18-83 0.281543 0.000030 1.467243 0.000046 0.001004 0.000032

Table B16 (

 B16 continued): In situ LA-MC-ICP-MS Lu-Hf isotope data for zircon grains from meta-sediments analysed at LMV, 7th of June, 2017

		B.5 Monazite UPb isotope measurements
	Hf/ Hf(T) e Hf (T) 2σ	0.281678 4.0 0.9 B.5.1 Analytical details on the LMV session 0.282208 0.282350 0.282443 0.281131 0.282300 0.282493 0.282552 0.282379 0.282389 0.281827 0.282384 0.281494 0.282402 0.282571 0.282300 0.281524 1.6 0.7 -1.1 0.6 10.8 1.1 1.9 1.0 -3.5 0.6 3.8 0.6 5.4 1.2 -1.3 0.8 -0.9 0.8 -11.9 0.8 -1.3 1.1 -5.7 0.8 0.8 0.9 4.7 0.9 -3.0 0.8 2.9 1.0
	2 SE Age 2σ	0.00230 1910 11	0.00022 981 9	0.00227 643 6	0.00060 1025 11	0.00139 2656 14	0.00327 614 6	0.00066 635 7	0.00117 612 6	0.00009 586 7	0.00025 590 6	0.00340 985 9	0.00116 576 6	0.00024 1776 18	0.00053 642 7	0.00293 550 5	0.00065 637 7	0.00113 2101 17
	Yb/ Hf	0.06404	0.03918	0.04866	0.06895	0.02919	0.02263	0.02959	0.06995	0.01690	0.02538	0.03884	0.03390	0.02608	0.03421	0.07536	0.03651	0.03079
	2 SE	0.000048	0.000006	0.000071	0.000019	0.000035	0.000097	0.000011	0.000045	0.000004	0.000011	0.000091	0.000024	0.000006	0.000017	0.000073	0.000015	0.000042
	Hf/ Hf 2 SE Hf/ Hf 2 SE Lu/ Hf	0.281744 0.000027 1.467255 0.000038 0.001809	0.282231 0.000019 1.467278 0.000031 0.001215	0.282367 0.000018 1.467297 0.000030 0.001477	0.282479 0.000030 1.467235 0.000044 0.001889	0.281176 0.000027 1.467293 0.000043 0.000869	0.282309 0.000017 1.467331 0.000029 0.000712	0.282505 0.000018 1.467257 0.000042 0.001024	0.282575 0.000034 1.467242 0.000043 0.002058	0.282385 0.000023 1.467323 0.000041 0.000554	0.282397 0.000022 1.467257 0.000045 0.000730	0.281848 0.000022 1.467215 0.000050 0.001183	0.282395 0.000032 1.467276 0.000046 0.000981	0.281524 0.000023 1.467299 0.000034 0.000869	0.282414 0.000025 1.467245 0.000047 0.000992	0.282593 0.000026 1.467226 0.000039 0.002166	0.282314 0.000021 1.467259 0.000036 0.001165	0.281566 0.000027 1.467237 0.000050 0.001051
	Spot	H-PIL16 #19-91	H-PIL16 #20-90	H-PIL16 #21-94	H-PIL16 #22-98	H-PIL16 #23-102	H-PIL16 #24-103	H-PIL16 #25-104	H-PIL16 #26-11	H-PIL16 #27-110	H-PIL16 #28-112	H-PIL16 #29-113	H-PIL16 #30-114	H-PIL16 #31-118	H-PIL16 #32-122	H-PIL16 #33-125	H-PIL16 #34-130	H-PIL16 #35-126

Table B15 :

 B15 Summary of experimental conditions for LAICPMS analyses conducted at LMV;

Table B16 :

 B16 Results of LAICPMS UPb analyses of monazite standard Itambé, performed at LMV, 15th of November, 2016;

Table B17 :

 B17 Results of LAICPMS UPb analyses of monazite from investigated samples, performed at LMV, 15th of November, 2016;B.6 AMS measurementsTableB18presents the results of AMS measurements performed at Saint-Etienne University (see section 6.2.3 for analytical details).

Table B15 .

 B15 Summary of experimental conditions for LA-ICPMS analyses conducted at LMV

	Laboratory & Sample
	Preparation
	Laboratory name	Laboratoire Magmas & Volcans, Clermont-Ferrand, France
	Sample type/mineral	Monazite
	Sample preparation	Polished thin sections, polished 1-inch resin mounts, 0.25µm polish to finish
	Imaging	BSE with a Zeiss MERLIN SEM at Stellenbosch university
	Laser ablation system
	Model & type	Resonetics/M-50E, ATL AtlexExcimer
	Ablation cell & volume	Laurin Cell ® two volumes cell, Laurin Technic Ltd., volume ca. 1-2 cm 3
	Laser wavelength	193 nm
	Pulse width	<4 ns
	Fluence	2.9 J.cm -2
	Repetition rate	3 Hz
	Spot size	9 µm
	Sampling mode / pattern	Single spot
	Carrier gas	100% He, Ar make-up gas and N2 combined using the Squid® device from
		RESOlution Instruments.
	Background collection	30 secs
	Ablation duration	60 secs
	Wash-out delay	30 secs
	Cell carrier gas flow	0.7 l/min
	ICP-MS Instrument
	Make, Model & type	Thermo Element XR single collector sector field ICP-MS
	Sample introduction	Via conventional tubing
	RF power	1300W
	Make-up gas flow	0.95 l/min Ar
	Detection system	Single collector secondary electron multiplier
	Masses measured	204, 206, 207, 208, 232, 238
	Integration time per peak 10 ms
	Total integration time per	130 ms
	reading	(should represent the time resolution of the data)
	Sensitivity / Efficiency	150 000 cps/ppm U and Th (3µm.s line, 47µm, 10 Hz, 9 J.cm -2 on NIST
		612 reference material)
	Dead time	35 ns
	Data Processing
	Gas blank	30 second on-peak
	Calibration strategy	Monazite: Trebilcock as primary reference material and Itambé as
		secondary reference material.
	Reference Material info	Itambé monazite (Gasquet et al. 2010)
		Trebilcock monazite (Tomascak et al. 1996, Kohn and Vervoort 2008)
	Data processing package	GLITTER ® (van Achterbergh et al. 2001)
	/ Correction for LIEF
	Mass discrimination	Monazite: standard-sample bracketing with 207 Pb/ 206 Pb and 206 Pb/ 238 U
		normalized to Trebilcock
	Common-Pb correction,	No common-Pb correction.
	composition and
	uncertainty

Table B16 :

 B16 . Reproducibility and age uncertainty of reference material are propagated. Quality control Itambé: weighted average 207 Pb/ 235 U age = 507.8±3.8 (2σ) Results of LA-ICP-MS U-Pb analyses of monazite standard Itambé, performed at LMV, 15 th

	of November, 2016
	Pb d
	207
	grain

Table B17 :

 B17 Results of LA-ICP-MS U-Pb analyses of monazite samples, performed at LMV, 15 th of Nov. 2016

	An.#	Pb	Th	U	Th	207 Pb d	±2s	206 Pb d	±2s	rho e	206 Pb ±2s
		(ppm)	(ppm)	(ppm)	U	235 U	(abs.)	238 U	(abs.)		U (Ma)
	CHA-15-17 Puylaurent migmatite (thin section)
	z8	1110	47578	11818	4.0	0.40053	0.01320	0.04638	0.00141	0.92	9
	z9	959	60887	2719	22.4	0.95350	0.03255	0.05049	0.00156	0.91	10
	z10	1076	68441	5933	11.5	0.35149	0.01515	0.04607	0.00144	0.73	9
	z11	387	2263	8446	0.3	0.34548	0.01290	0.04668	0.00144	0.83	9
	z19	828	37713	7463	5.1	0.50057	0.01683	0.04822	0.00147	0.91	9
	z20	975	61573	4522	13.6	0.36589	0.01311	0.04732	0.00144	0.85	9
	z21	551	30686	3586	8.6	0.35848	0.01467	0.04839	0.00150	0.76	9
	z22	1479	96715	5389	17.9	0.39610	0.01542	0.04755	0.00147	0.79	9
	z27	355	20131	2416	8.3	0.37407	0.01911	0.04849	0.00156	0.63	10
	z28	311	17611	1885	9.3	0.38977	0.01575	0.05031	0.00156	0.77	10
	z29	1192	70517	6411	11.0	0.34752	0.01233	0.04723	0.00144	0.86	9
	z31	544	26498	4447	6.0	0.35296	0.01365	0.04856	0.00150	0.80	9
	z32	1174	78400	3355	23.4	0.40076	0.01701	0.04794	0.00150	0.74	9
	CHA-15-65M Puylaurent migmatite (melanosome; mount)
	z7	790	39380	5660	7.0	0.35221	0.01248	0.04671	0.00132	0.80	8
	z8	752	40458	4092	9.9	0.43788	0.01803	0.04928	0.00144	0.71	9
	z9	858	36991	6232	5.9	0.39953	0.01389	0.0519	0.00147	0.81	9
	z10	2969	183749	11883	15.5	0.54676	0.01869	0.04915	0.00141	0.84	9
	z11	2068	86578	18230	4.7	0.70091	0.02265	0.04882	0.00138	0.87	9
	z13	2064	103432	13876	7.5	0.39153	0.01299	0.05043	0.00144	0.86	9
	CHA-15-65L Puylaurent migmatite (leucosome; mount)
	z29	5217	157142	82307	1.9	0.31930	0.00972	0.04343	0.00120	0.91	7
	z31	4996	155471	77270	2.0	0.31362	0.00960	0.04333	0.00120	0.90	7
	z35	2869	171846	18554	9.3	0.30971	0.01008	0.04283	0.00120	0.86	7
	z37	6326	214940	89458	2.4	0.32625	0.01011	0.04348	0.00120	0.89	8
	z38	6428	184560	106368	1.7	0.30934	0.01002	0.04303	0.00120	0.86	7
	z40	2956	168017	24118	7.0	0.30500	0.00981	0.0418	0.00117	0.87	7
	z45	2341	135593	17266	7.9	0.32016	0.01266	0.04323	0.00123	0.72	8
	z46	3686	130991	49283	2.7	0.36763	0.01185	0.04391	0.00123	0.87	8
	z47	4406	150764	61713	2.4	0.32221	0.01032	0.04392	0.00123	0.87	8
	z49	5289	162277	85236	1.9	0.35405	0.01137	0.04301	0.00120	0.87	7
	CHA15-48 St Laurent-les-Bains migmatite (mount)
	z16	2149	112215	16847	6.7	0.33645	0.01128	0.04651	0.00132	0.85	8
	z17	2597	116652	27169	4.3	0.36486	0.01203	0.04652	0.00132	0.86	8
	z18	3503	110801	49928	2.2	0.34956	0.01143	0.04665	0.00132	0.87	8
	z21	2202	79052	26030	3.0	0.49296	0.01647	0.0468	0.00132	0.84	8
	z22	1179	55436	8443	6.6	0.71224	0.02475	0.04945	0.00141	0.82	9
	z23	2030	78773	3081	25.6	0.69964	0.02580	0.08362	0.00240	0.78	14
	z24	2034	76324	2857	26.7	0.73418	0.02745	0.08796	0.00252	0.77	15

CHA-15-34 Le Couste post-tectonic granite dyke (mount)

	z7	1970	88799	22118	4.0	0.31710	0.00957	0.04343	0.00120	0.92	7
	z8	3491	146268	41607	3.5	0.31453	0.00954	0.04437	0.00123	0.91	8
	z9	1762	86566	16666	5.2	0.32446	0.00987	0.04409	0.00123	0.92	8
	z10	2604	110055	31064	3.5	0.31828	0.00954	0.04451	0.00123	0.92	8
	z11	2247	139908	12568	11.1	0.33500	0.01053	0.04429	0.00123	0.88	8
	z12	2421	132827	20303	6.5	0.31603	0.00972	0.04391	0.00123	0.91	8
	z15	1199	71231	8350	8.5	0.32212	0.01128	0.04433	0.00126	0.81	8
	z16	2188	135902	13345	10.2	0.31888	0.01083	0.04334	0.00123	0.84	8
	z17	2177	130765	15244	8.6	0.31312	0.00993	0.04314	0.00120	0.88	7
	z18	1930	108366	15448	7.0	0.31405	0.00984	0.04294	0.00120	0.89	7
	z19	2665	119409	30918	3.9	0.31548	0.00957	0.04338	0.00120	0.91	7
	z20	3421	176094	43661	4.0	0.36106	0.01083	0.04336	0.00120	0.92	7
	z21	3760	100697	63548	1.6	0.31741	0.00957	0.0435	0.00120	0.91	7
	z22	3939	120085	61747	1.9	0.31324	0.00942	0.04369	0.00123	0.94	8
	z25	4909	142513	79359	1.8	0.32084	0.00969	0.0437	0.00123	0.93	8
	z26	2883	139622	28965	4.8	0.32237	0.00996	0.04343	0.00120	0.89	7
	CHA-15-25 Le Ranc granite sill (thin section)
	z7	2550	61771	44490	1.4	0.32003	0.01032	0.04484	0.00141	0.98	9
	z8	3195	88029	52047	1.7	0.32360	0.01044	0.04489	0.00141	0.97	9
	z10	2055	91963	8262	11.1	0.32714	0.01056	0.04542	0.00141	0.96	9
	z11	656	65435	2032	32.2	0.40401	0.01338	0.04554	0.00144	0.95	9
	z15	1129	194609	818	238.0	0.31092	0.01128	0.04422	0.00141	0.88	9
	z16	1146	195348	810	241.2	0.31634	0.01152	0.04494	0.00141	0.86	9
	z17	107	8327	222	37.6	0.59525	0.02280	0.05732	0.00183	0.83	11
	z18	1968	115713	7416	15.6	0.32014	0.01041	0.0448	0.00141	0.97	9
	z19	1154	72337	4199	17.2	0.33938	0.01122	0.04472	0.00141	0.95	9

Table B18 :

 B18 Results of AMS measurements performed at Saint-Etienne University

	Specimen	Km (.10 -6 SI)	L	F	P	P'	T	U	K 1 dec K 1 inc K 2 dec K 2 inc K 3 dec K 3 inc
	Site 1 Le Ranc (44.533778, 3,900976)
	15CVE04A	112.1	1.013 1.266 1.282 1.323	0.898	0.885	111.5 39.8	4.2	19.7	254.2	43.7
	15CVE05A	29.8	1.05	1.033 1.085 1.085 -0.209	-0.229	88.5	50.6 308.8	32	205.4	20.3
	15CVE06A	171.3	1.213 1.092 1.325 1.333 -0.373	-0.433	126	25.9 307.7	64.1	216.3	0.7
	15CVE07A	22.0	1.04	1.077	1.12	1.122	0.313	0.287	129.1 50.8 355.7	29.3	251.5	23.6
	15CVE08A	247.7	1.079 1.245 1.343 1.358	0.486	0.429	72.5	28.7 338.2	7.9	234.4	60.1
	15CVE08B	43.2	1.014 1.124 1.139 1.154	0.788	0.775	343.4	5.3	77.4	37.1	246.4	52.4
	15CVE09A	42.0	1.012 1.095 1.108 1.119	0.771	0.76	125.2 32.9 352.7	46.3	233	25.3
	15CVE10A	27.3	1.011 1.159 1.172 1.194	0.86	0.849	26.7	61.5 162.3	21.2	259.6	18.1
	15CVE11A	192.4	1.037 1.435 1.488 1.552	0.817	0.782	168.7 26.8	357	62.9	260.4	3.3
	15CVE12A	61.1	1.023 1.174 1.201 1.221	0.754	0.734	130.9 10.9	34.4	30.7	238.3	57
	15CVE13A	105.6	1.014 1.228 1.244 1.278	0.877	0.864	350.6 17.3 105.4	53.4	249.8	31.1
	15CVE13B	110.8	1.02	1.198 1.221 1.246	0.806	0.789	124.6 41.2	10.6	24.9	258.8	38.6
	Site 2 Le Ranc (44.53317, 3.901795)
	15CVE14A	59.0	1.033 1.052 1.086 1.087	0.219	0.199	276.6 16.7 170.3	43	22.4	42.3
	15CVE15A	83.6	1.022	1.12	1.145 1.156	0.679	0.661	219.6	9.1	124.8	27.9	326.1	60.4
	15CVE16A	54.1	1.011	1.06	1.072 1.077	0.672	0.662	99.8	5.9	199.9	59.7	6.5	29.6
	15CVE17A	70.0	1.01	1.129	1.14	1.158	0.853	0.844	86.7	44.5	194	16.8	299.1	40.7
	15VCE18A	93.7	1.018 1.035 1.054 1.055	0.329	0.317	148.7 56.1	55.2	2.4	323.5	33.8
	15CVE19A	84.6	1.008	1.05	1.059 1.063	0.712	0.705	234.7 54.3	102	26	0.2	22.7
	15CVE20A	68.5	1.016 1.029 1.046 1.046	0.273	0.262	189.9 40.6	71.8	28.8	318.3	35.9
	15CVE21A	41.4	1.021 1.009	1.03	1.031	-0.41	-0.416 181.8 23.7 280.2	18.5	44.4	59.2
	15CVE21B	66.8	1.05	1.006 1.056 1.061 -0.786	-0.791 222.9 31.2 344.5	40.8	109.3	33.5
	15CVE22A	54.9	1.018 1.046 1.065 1.067	0.442	0.429	245.9 10.9 131.8	64.7	340.4	22.5
	15CVE22B	72.7	1.006 1.059 1.065 1.072	0.797	0.791	217.3	19	107.2	45	323.4	38.9
	15CVE23A	86.0	1.004 1.044 1.049 1.054	0.817	0.813	85.1	24.7	198	40.2	332.6	39.7
	15CVE24A	60.1	1.007 1.015 1.022 1.023	0.391	0.386	173.7 38.2	80.8	3.7	346.1	51.6
	Site 3 Combe Serre (44.535566, 3.891003)
	15CVE25A	8.9	1.067 1.149 1.226 1.231	0.366	0.321	26.2	1	295.9	16.3	119.8	73.7
	15CVE26A	28.2	1.053 1.081 1.138 1.139	0.209	0.178	257.9 19.2 163.3	13	41.3	66.5
	15CVE27A	28.6	1.05	1.024 1.075 1.077 -0.349	-0.365 245.6 17.7 351.1	40	137.2	44.7
	15CVE27B	13.0	1.063	1.11	1.18	1.182	0.259	0.22	54	4.8	322.6	16.2	160	73.1
	15CVE28A	24.3	1.021 1.029 1.051 1.051	0.141	0.129	248	7	339	8.7	119.7	78.8
	15CVE29A	68.2	1.035 1.078 1.115 1.118	0.374	0.351	229.2	0.5	319.2	7.9	135.3	82.1
	15CVE30A	108.9	1.045 1.069 1.117 1.118	0.202	0.175	223.2 13.1 122.9	37.6	329	49.4
	15CVE30B	126.9	1.023 1.115 1.141 1.151	0.655	0.636	242.8	3.5	335.2	33.8	147.6	55.9
	15CVE31B	65.8	1.056 1.054 1.113 1.113 -0.013	-0.04	230.2	6.6	104.9	78.7	321.3	9.1
	15CVE31A	86.1	1.032 1.115	1.15	1.159	0.555	0.53	232.4 17.3 114.3	56.4	331.8	27.8
	15CVE32A	64.2	1.07	1.049 1.122 1.123 -0.173	-0.201	233	16	323.1	0.4	54.5	73.9
	15CVE33A	95.0	1.024 1.162 1.191 1.208	0.725	0.704	226.1	8.4	317	6.1	82.5	79.6
	15CVE33B	93.9	1.035 1.087 1.125 1.129	0.411	0.386	237.3	8.4	329.2	12.5	114.3	74.8
	Site 4 Puylaurent (44.533841, 3.885268)
	15CVE34B	69.4	1.01	1.099 1.111 1.123	0.804	0.795	165.7 19.8 268.2	31.1	48.4	51.9
	15CVE34A	71.4	1.001 1.121 1.122 1.142	0.982	0.981	173.3	22	274.5	25.6	47.9	55.1
	15CVE35A	13.6	1.042 1.071 1.117 1.118	0.249	0.223	263.1 19.7 357.1	11.1	114.9	67.2
	15CVE36A	10.7	1.041 1.116 1.162 1.168	0.459	0.429	153	7.9	245.8	19.2	41.6	69.1
	15CVE37A	93.3	1.013 1.131 1.146 1.162	0.806	0.794	254.8 64.2 122.6	18	26.6	17.8
	15CVE38B	16.5	1.041	1.1	1.145	1.15	0.41	0.382	276.1 43.8	182	4.2	87.7	45.9
	15CVE38A	18.3	1.025 1.099 1.126 1.134	0.592	0.572	250.4 46.5 152.7	7.2	56	42.6
	15CVE39A	5.2	1.07	1.34	1.433 1.467	0.626	0.57	261.8 25.4 161.9	20	38.2	56.7
	15CVE40A	85.2	1.003 1.125 1.128 1.148	0.958	0.956	232.8 50.8 134.7	6.5	39.5	38.4
	15CVE41A	85.1	1.009 1.119 1.129 1.145	0.847	0.839	216.8 45.9 120.3	6.2	24.4	43.4
	15CVE42A	67.5	1.015 1.096 1.112 1.122	0.725	0.712	256.6 56.9 127.8	22.2	27.7	23.2
	Site 5 Les Clous (44.546591, 3.905026)
	15CVE43A	154.5	1.041 1.046 1.088 1.088	0.057	0.036	161	7.2	39.1	76.6	252.5	11.2
	15CVE43B	137.3	1.049 1.029	1.08	1.081 -0.248	-0.266 165.6	6.7	12.9	82.5	256	3.4
	15CVE44A	148.1	1.036 1.038 1.076 1.076	0.028	0.01	174.9 11.5	34.4	75.2	266.8	9.1
	15CVE45A	152.1	1.045 1.052	1.1	1.1	0.07	0.047	172.8 15.6	18.1	72.8	264.8	7
	15CVE46A	147.5	1.05	1.05	1.103 1.103 -0.004	-0.028 170.6 16.1	38.4	66.8	265.4	16.3
	15CVE46B	139.3	1.045 1.044 1.091 1.091 -0.006	-0.028 168.7 13.9	44.8	66	263.6	19.1
	15CVE47A	97.3	1.037 1.035 1.074 1.074 -0.027	-0.044 189.2 22.4 345.2	65.7	95.5	8.9
	15CVE47B	98.3	1.038 1.025 1.064 1.064 -0.198	-0.212	181	27.4 346.6	61.9	87.9	6
	15CVE48A	96.3	1.037 1.051	1.09	1.09	0.157	0.136	191.2	24	355.4	65.2	98.5	6
	15CVE48B	93.9	1.047 1.054 1.103 1.103	0.063	0.039	188.1	28	355.2	61.4	95.2	5.4
	15CVE48C	84.5	1.038 1.047 1.086 1.087	0.104	0.084	192.7 25.7 349.3	62.3	98.1	9.6
	15CVE49A	90.5	1.04	1.037 1.078 1.078 -0.046	-0.064 180.7 23.1	334	64.5	86.3	10.2
	15CVE49B	89.2	1.049 1.041 1.093 1.093 -0.086	-0.108 180.3 19.1 331.9	68.5	87	9.5
	15CVE50B	87.4	1.033 1.035	1.07	1.07	0.027	0.01	184.9	15	318.4	68.8	90.8	14.7

Table B18 (

 B18 cont.): Results of AMS measurements performed at Saint-Etienne University

	Specimen	Km (.10 -6 SI)	L	F	P	P'	T	U	K 1 dec K 1 inc K 2 dec K 2 inc K 3 dec K 3 inc
	15CVE50A	92.1	1.037 1.035 1.073 1.073 -0.029	-0.047 189.8 15.5 331.1	70.4	96.5	11.7
	15CVE51B	78.9	1.04	1.033 1.074 1.074 -0.099	-0.117	195	11.8	35.9	77.4	285.9	4.4
	15CVE51A	84.6	1.036 1.029 1.066 1.066 -0.116	-0.132 193.3 21.1	21.1	68.7	284.3	2.7
	15CVE52B	129.0	1.053 1.036 1.091 1.091	-0.19	-0.211 157.2	11	354	78.5	247.9	3.2
	15CVE52A	129.3	1.048 1.039 1.088 1.088 -0.105	-0.125 161.5	9.5	10.4	79.1	252.4	5.1
	15CVE55A	137.8	1.049 1.036 1.087 1.087 -0.152	-0.172 151.5 23.1	5.5	62.8	247.4	13.6
	15CVE55B	121.6	1.054 1.034	1.09	1.091 -0.215	-0.235 153.5 18.7	14.9	65.8	248.6	14.9
	15CVE56A	133.9	1.06	1.035 1.098 1.099 -0.257	-0.279	161	12	15.1	75.6	252.7	7.8
	15CVE56B	134.3	1.059 1.036 1.096 1.097	-0.24	-0.262 159.4 14.4	28.4	68.6	253.5	15.4
	Site 6 Puech Redon (44.577817, 3.895382)
	15CVE57A	45.4	1.017 1.113 1.133 1.144	0.725	0.71	322.7 26.8	81.4	43.5	212.3	34.6
	15CVE58A	85.2	1.022 1.118 1.143 1.154	0.672	0.653	20.4	46	289.2	1.1	198.2	44
	15CVE59A	45.7	1.007 1.128 1.136 1.154	0.886	0.879	26.1	26.5 120.6	9	227.8	61.7
	15CVE60B	51.6	1.013 1.145	1.16	1.179	0.829	0.817	99.7	24.9 356.8	25.7	227.4	52.8
	15CVE60A	53.1	1.019 1.106 1.127 1.138	0.68	0.663	19.3	28.5 118.1	15.8	233.7	56.7
	15CVE60B	51.4	1.007 1.156 1.164 1.187	0.905	0.898	102.8 23.1	2.3	23.2	232.4	56.3
	15CVE61A	56.1	1.005 1.113 1.119 1.136	0.906	0.9	96.7	46.4 343.9	20.3	237.9	36.6
	15CVE62A	36.3	1.004 1.102 1.106 1.121	0.929	0.926	16.5	36.6 125.1	23.3	240	44.3
	15CVE62B	36.9	1.022 1.104 1.128 1.137	0.646	0.628	104.5 44.6 352.9	20.5	245.7	38.4
	15CVE63A	46.8	1.004 1.071 1.075 1.085	0.883	0.879	104.7 16.7 356.2	46.6	208.6	38.6
	15CVE64A	47.2	1.011 1.164 1.177	1.2	0.862	0.851	358.9 41.2	98.4	10.7	200.1	46.8
	15CVE65A	78.5	1.015 1.123	1.14	1.154	0.766	0.753	95.5	27.8 333.3	45.3	204.5	31.8
	15CVE66A	57.2	1.028 1.018 1.047 1.047 -0.223	-0.234	111	9	19.8	7.5	250.6	78.2
	15CVE67A	80.5	1.011 1.065 1.076 1.082	0.709	0.7	101.6 13.4 193.2	6.5	308.7	75
	Site 7 Masméjean (44.568143, 3.878975)
	15CVE69A	39.1	1.034 1.055 1.091 1.092	0.234	0.213	329.6	0.7	223.3	87.6	59.6	2.3
	15CVE70A	21.9	1.015 1.008 1.023 1.023 -0.312	-0.317	84.3	44.4 336.2	17.6	230.6	40.3
	15CVE71B	34.1	1.023 1.065 1.089 1.093	0.479	0.462	333.5 25.9 111.4	56.8	233.7	19.2
	15CVE71A	35.8	1.027 1.022	1.05	1.05	-0.099	-0.111 334.6 12.8	85.6	57.6	237.3	29.2
	15CVE72A	27.0	1.013 1.009 1.021 1.021	-0.18	-0.185 331.1	1.5	239.1	53.8	62.2	36.2
	15CVE73A	22.0	1.026 1.014 1.041 1.041 -0.281	-0.29	144.9 15.8 305.6	73.3	53.4	5.2
	Site 8 Le Ranc (44.531518, 3.90263)
	17CVE01A	14.3	1.024 1.203 1.232 1.256	0.77	0.748	52.7	49.7 270.4	33.9	166.9	19.2
	17CVE02A	14.0	1.021 1.291 1.319 1.361	0.848	0.827	33.6	37.2 293.4	13.2	187.3	49.8
	17CVE03A	14.9	1.071 1.208 1.293 1.305	0.467	0.416	58.8	38.8 311.5	20.3	200.4	44.2
	17CVE04A	85.4	1.009 1.159 1.169 1.192	0.889	0.88	357.9 39.8 107.1	21.5	218.2	42.4
	17CVE05A	25.5	1.002 1.175 1.178 1.206	0.972	0.97	281.9	9.7	20	39.6	180.7	48.7
	17CVE05B	29.1	1.025 1.136 1.165 1.178	0.674	0.652	71.9	23.9 325.1	33.2	190.4	47.1
	17CVE06C	22.1	1.064 1.115 1.186 1.188	0.273	0.233	317.4 13.3	57.3	35.9	210.4	50.9
	17CVE06B	21.3	1.045	1.1	1.15	1.154	0.368	0.337	323.8	7.4	58	29.4	221.1	59.5
	17CVE06A	24.1	1.049 1.072 1.124 1.125	0.188	0.16	336.5 23.4	71.7	11.7	186.2	63.5
	17CVE07A	26.8	1.014 1.071 1.086 1.092	0.658	0.647	354.1 48.6	99.3	13	199.9	38.5
	17CVE07B	17.3	1.015 1.132	1.15	1.165	0.781	0.768	334.1 30.5	79.4	24.1	200.9	49.4
	17CVE08A	38.9	1.028 1.107 1.138 1.145	0.568	0.546	349.5 33.1	94.8	22	212	48.5
	Site 9 Les Gouttes (44.548959, 3.868486)
	17CVE10A	54.2	1.016 1.204 1.223 1.251	0.843	0.828	199.1 31.5 290.2	1.9	23.4	58.4
	17CVE10B	72.8	1.007 1.187 1.196 1.225	0.918	0.911	202.5 27.6 109.1	6.5	6.9	61.5
	17CVE10C	77.1	1.016 1.179 1.198 1.222	0.825	0.811	181.6 32.1 274.6	4.7	12	57.5
	17CVE11B	17.4	1.058 1.016 1.075 1.079 -0.567	-0.579 224.8 28.1 322.5	14.1	76.1	58
	17CVE11A	15.5	1.036 1.051 1.089 1.089	0.169	0.149	210	21.3 300.4	0.9	32.7	68.7
	17CVE12B	44.2	1.014 1.161 1.178 1.199	0.829	0.816	187.7 24.7 278.1	1	10.4	65.3
	17CVE12A	50.3	1.017 1.171 1.191 1.213	0.805	0.789	155.5 17.8 248.2	8.3	2.2	70.2
	17CVE13A	24.3	1.051 1.078 1.133 1.134	0.207	0.177	240.5 28.7 145.1	9.8	38.1	59.3
	17CVE13B	22.9	1.015 1.125 1.143 1.157	0.769	0.756	236.6 26.8 145.6	2	51.7	63.1
	17CVE13C	21.3	1.026	1.11	1.138 1.147	0.61	0.589	168.1 42.6 264.7	7.1	2.3	46.6
	17CVE14A	71.8	1.005 1.123 1.128 1.146	0.915	0.909	313.7 15.6 220.3	11.8	94.8	70.3
	17CVE15B	60.0	1.005 1.133 1.138 1.158	0.926	0.921	326.8	1.1	236.5	11.7	61.9	78.2
	17CVE15A	50.3	1.01	1.159	1.17	1.192	0.879	0.87	151.7	9.7	245.6	21.6	39	66.1
	17CVE16A	58.8	1.017 1.154 1.174 1.192	0.789	0.774	250.7 20.6 151.3	23.5	17.5	57.9
	17CVE16B	55.0	1.008	1.17	1.179 1.204	0.907	0.9	287.7	1.7	197.1	21.3	22.2	68.7
	17CVE17A	51.7	1.02	1.222 1.246 1.276	0.822	0.804	169.7 43.5 261.2	1.5	352.7	46.4
	17CVE17B	64.7	1.01	1.16	1.171 1.194	0.879	0.87	141.4 37.4 242.8	14.5	350	48.9

Table B18 (

 B18 cont.): Results of AMS measurements performed at Saint-Etienne University

	Specimen	Km (.10 -6 SI)	L	F	P	P'	T	U	K 1 dec K 1 inc K 2 dec K 2 inc K 3 dec K 3 inc
	Site 10 Le Thort (44.555368, 3.905332)
	17CVE18A	4.2	1.133 1.033 1.171 1.181 -0.585	-0.61	67.7	25	218.4	61.9	332	12.1
	17CVE18B	15.1	1.041 1.062 1.105 1.106	0.201	0.177	53.5	4.2	145.4	23.5	314.1	66.1
	17CVE20B	2.9	1.121 1.216 1.363 1.368	0.263	0.19	297.6 18.4	34	18.5	165.8	63.4
	17CVE21B	19.5	1.055 1.051 1.109 1.109 -0.032	-0.058 145.6 35.8	50	7.6	309.8	53.2
	17CVE22A	16.9	1.042 1.079 1.124 1.126	0.302	0.275	130.1 30.4	36.5	6.2	296.2	58.8
	17CVE23A	33.2	1.007 1.019 1.026 1.027	0.443	0.438	157.4 26.5 270.8	38.7	42.8	39.9
	17CVE24A	10.4	1.03	1.078	1.11	1.113	0.439	0.418	92.1	20	1.8	0.9	269.4	70
	17CVE25B	11.3	1.065 1.025 1.091 1.094 -0.445	-0.462	75.3	8.2	332.1	57.9	170.2	30.8
	17CVE25C	12.9	1.057 1.018 1.075 1.079 -0.518	-0.531	58.7	38.9 324.6	5	228.6	50.6
	17CVE25A	16.5	1.014 1.026 1.041 1.041	0.303	0.294	26	14.3 126.7	36.1	278.1	50.3
	17CVE26A	11.1	1.057 1.031	1.09	1.091 -0.288	-0.308 165.8	12	45.9	66.9	260.1	19.4
	Site 11 Masméjean railway (44.565239, 3.887277)
	17CVE27A	87.7	1.011 1.059	1.07	1.076	0.674	0.665	191	5.5	283.5	24.1	88.9	65.2
	17CVE28A	42.1	1.025	1.05	1.076 1.077	0.332	0.315	250.4	4.7	342	18	146.2	71.3
	17CVE29A	107.7	1.021 1.072 1.095	1.1	0.537	0.52	279.4	6.5	9.8	3.6	128.7	82.6
	17CVE30A	70.0	1.008 1.065 1.073	1.08	0.784	0.778	283.4 23.2	19.6	14.2	138.4	62.4
	17CVE30B	97.5	1.006 1.073 1.079 1.088	0.844	0.839	283	10.1	16.5	18.8	166.1	68.4
	17CVE31A	108.6	1.009 1.128 1.138 1.156	0.868	0.86	251.7	3.3	342.5	14.4	148.9	75.2
	17CVE32B	45.4	1.004 1.074 1.078 1.089	0.887	0.883	40.3	0.4	310.2	21.6	131.4	68.4
	17CVE32C	62.2	1.003 1.081 1.084 1.096	0.928	0.925	269.2 26.9	6.2	13.5	120.1	59.4
	17CVE32A	63.2	1.016 1.053	1.07	1.073	0.524	0.512	242	21.7 340.4	20.2	109.3	59.6
	17CVE33A	23.4	1.02	1.027 1.047 1.048	0.161	0.15	75.5	1.4	165.5	0.9	286.2	88.3
	17CVE33B	16.3	1.036 1.046 1.083 1.083	0.125	0.105	27.4	11.8 119.8	11.4	252.7	73.4
	17CVE34B	97.8	1.007 1.013	1.02	1.021	0.266	0.262	314.7	7	223.7	8.5	83.7	79
	17CVE34A	48.8	1.017 1.023 1.041 1.041	0.139	0.129	239.8	0.9	149.7	4.8	340.9	85.1

S.Couzinié et al. / Lithos 286-287 (2017) 16-34

S.Couzinié et al. / Lithos 286-287 (2017) 16-34

Acknowledgements

Here comes the time to write the acknowledgement section, trickier than I would have

Acknowledgements

We acknowledge funding from the European Commission, together with the UJM through the Campus France PRESTIGE program to C.C.-M.; and with Université de Liège through the Marie-Curie Actions Be-IPD-Acknowledgements Financial support from CNRS-INSU (project SYSTER to J.F.M.) and the Deutscher Akademischer Austauschdienst (DAAD research grant nr. A/13/70682 to O.L.) are greatly acknowledged. We are grateful to E. Bruand, A. Gerdes, L. Marko and A. Vézinet for help during sample preparation and measurements. B. Barbarin and P. Bouilhol are thanked for discussions and assistance during fieldwork and sampling. We are grateful to the detailed and insightful comments provided by an anonymous reviewer, and thank W.C. Dullo, P. Pitra and M. Ballèvre for editorial handling and remarks on the manuscript.

Acknowledgements

We acknowledge financial support from an ERC grant (StG 279828, project MASE to J. van Hunen), two PNP grants from French CNRS ("Différentiation et évolution de la croûte tardi orogénique", 2014 and "Quantification de la durée d'un épisode de fusion partielle en contexte de désépaississement tardi-orogénique", 2016), the Deutsche Forschungsgemeinschaft (grant Zeh424/11-2 to A.Z.) and the Deutscher Akademischer Austauschdienst (grant A/13/70682 to O.L.). A.V. acknowledges funding by the Labex VOLTAIRE (ANR-10-LABX-100-01). V. Gardien provided two samples for this study. D. Garcia kindly supplied his database and guided us in the field. A. Vézinet, M. Benoit and E. Bruand assisted during zircon separation procedures. Helpful discussions with V. Janoušek and G. Stevens were much appreciated. A. Gerdes assisted during Hf analytical sessions and P. Montero performed zircon imaging and SHRIMP measurements. This contribution is IBERSIMS publication N • 35. We are grateful to A. Yin for editorial handling. C.L. Farmer and S. Wilde provided thorough and constructive reviews; R. Rudnick, P. Cawood and an anonymous reviewer provided insightful comments on an earlier version of this manuscript -may they all be thanked.

. PB acknowledges support from ERC Starting Grant (MASE; 279828), and his Auvergne Fellowship (French Government Laboratory of Excellence initiative no. ANR-10-LABX-0006, ClerVolc contribution no. 255). We thank C. Guilbaud for making the thin sections, S. Sao-Joao and J.-L. Devidal for assistance during SEM imaging and B. Moine for help during zircon separation. We are indebted to M. Ballèvre who provided the file of Fig. 1. M. J. Mayne, G. Nicoli,

Appendix A. Supplementary material

Supplementary material related to this article can be found online at http://dx.doi.org/10.1016/j.epsl.2016.09.033.

Appendix A

Supplementary materials of published articles

A. 1 Laurent et al., 2017 Are presented in the following: the Supplementary Text which includes additional gures; Supplementary Table S1: Results of LASFICPMS UPb analyses of standard zircons GJ-1, Ple²ovice, OG-1 and BB; Supplementary Table S2: Results of LASFICPMS UPb analyses of zircons from granitoids and vaugnerites of the Eastern French Massif Central.

Supplementary material

to the article : " , coeval crust and mantle melting during Variscan late-orogenic evolution: zircon U-Pb dating in the eastern French Massif Central" Oscar Laurent*, Simon Couzinié, Armin Zeh, Olivier Vanderhaeghe, Jean-François Moyen, Arnaud Villaros, Véronique Gardien, Cyril Chelle-Michou *Corresponding author: olaurent@ulg.ac.be or oscarlaurent86@gmail.com ; Tel.:(+32)43662250

A. 2 Couzinié et al., 2016 Are reported: the Supplementary Text with additional references; Supplementary

Whole-rock geochemistry

Samples were sawed at Saint-Etienne University and a c. 500 g fragment of each sample was sent to ALS Global for whole-rock chemical composition measurements. We chose the "Complete Characterization Package" which combines ICP-AES and ICP-MS analyses for major and trace elements, respectively. More information about analytical routines used by this company can be found at http://www.alsglobal.com/. Repeated analyses of standards MRGeo08, OGGeo08, NCSZC73007, SY-4, GBM908-10, GBM908-5 and GEOMS-03 were obtained during the analytical session.

Analyses on the standards were reproducible to < 1.6% for major elements, < 5.8% for trace elements (except Cr, V and Zr) and consistent within uncertainty with the expected values for these standards. Duplicate measurements of ten samples show external reproducibility better than 1.8% (RSD) for major elements (except CaO at 3.3%) and generally better than 9% (RSD) for trace elements, except for Sn, Ta, W, Se, Te, Lu and Cr. Thirty-two blanks display measured values typically under detection limits for all major and trace elements.

Results for the investigated samples are presented in Table S1.

Whole-rock geochemistry procedures

Samples were sawed at Saint-Etienne University and a c. 500 g (for leucogneisses) to 2000 g (for augen gneisses) fragment of each sample was sent to ALS Global firm for whole-rock chemical composition measurements. We chose the "Complete Characterization Package" which combines ICP-AES and ICP-MS analyses for major and trace elements, respectively. More information about analytical routines used by this company can be found at http://www.alsglobal.com/. Repeated analyses of standards SY-4, GRE-3, OREAS-121 and AMIS0304 were realized during the analytical session.

Analyses of the standards were reproducible to < 1.7% for most major elements (except K2O 2.4%, MgO 6.4% and P2O5 4.6%), < 7.9% for trace elements (except Cr 25%, V 12.5%, and Ba 10.9%)

and consistent within uncertainty with the expected values. Duplicate measurements of four samples show external reproducibility better than 1.1% (RSD) for major elements (except P2O5 at 4.6%) and generally better than 5.4% (RSD) for trace elements except for Tl, Tm, Lu, Hf and V.

Fifteen blanks display measured values typically under detection limits for all major and trace elements.

Results for the investigated samples are presented in Table S1.

Patiño Douce, A.E., Beard, A.D., 1995 Supplementary figures to the article : "Cadomian S-type granites as basement rocks of the Variscan belt (Massif Central, France): implications for the crustal evolution of the north Gondwana margin"

Figure S1: MFW plot (Ohta and Arai, 2007) for the VOF samples retained for geochemical interpretations. Meta-igneous rocks experienced limited LILE mobility. Large symbols represent newly obtained geochemical data. Same legend as Fig. 6.

Figure S2: Rb-Sr isochron for samples of augen gneisses and leucogneisses from the VOF. Data from the literature (Caen-Vachette, 1979; R'Kha [START_REF] Chaham | The fix augen gneiss (French Massif Central): new evidence for the lower Cambrian peraluminous magmatism[END_REF]. The isochron age of 541 ± 14 Ma (N=22, calculated with the Isoplot program using the robust regression mode) argues for limited mobility of LILE (here Rb and Sr) during amphibolite-facies metamorphism.