Veronique Le Roux

Remercie Lee

Cara Donnelly

Melissa Kobussen

Weiqiang Li

Marek Locmelis

Olivia Wang

Sans

Benjamin Bonnefoy

Aurélien Delaunay

Sébastien Dulais

Antoine Lucas

Sabrina Havard

J.-L Bodinier

A Tommasi

O Alard

J.-M Dautria

A Vauchez

A J V Riches

S Y O'reilly

W L Griffin

The Lherz spinel lherzolite: refertilized rather than pristine mantle

Keywords: Lherz, refertilization, melt-rock reaction, erosion of the lithospheric mantle Chapter melt percolation, strain localization, mantle lithosphere, olivine, pyroxene, crystal-preferred orientation, dislocation creep, diffusion, refertilization reactions, lherzolites, websterites, harzburgites, melt segregation Chapter

Differentiation of the lithospheric mantle occurred principally through partial melting and extraction of basaltic melt. In this scheme, harzburgites are widely considered as refractory mantle residues left after extraction of a basaltic component, whereas fertile lherzolites are regarded as pristine mantle only weakly affected by partial melting. However, a part of tectonically-emplaced mantle rocks displays local evidence of melt percolation and have been ascribed to igneous refertilization of refractory peridotites. In this context, the present work re-investigates the nature of the Lherz spinel lherzolites (French Pyrenees), from the typelocality of lherzolites, described as a piece of preserved fertile mantle. Structural and geochemical data presented in this study show that the Lherz lherzolites are not pristine but formed through a refertilization reaction between MORB-like ascending partial melts and a depleted lithosphere from which the Lherz harzburgites are the remnants. As the type locality of lherzolites, the Lherz peridotites were partly used to infer the composition of the primitive upper mantle and these results may have important implications for the nature of the late veneer. Additionally, the analysis of crystal-preferred orientations (CPO) of minerals from Lherz peridotites highlight a strong feedback between percolation of basaltic melts and deformation under near-solidus conditions at the lithosphere-asthenosphere boundary, suggesting that refertilization may be a major process involved in the rejuvenation of the lithosphere. Variations in CPO patterns and intensity record the relative contribution of dislocation glide and diffusion processes, ruled by a balance between instantaneous melt fraction and local strain rate. These results also suggest that the pervasive websteritic layering that formed synchronous to the refertilized lherzolites may result from deformation-assisted melt segregation due to decreasing permeability in the system. Finally, this work investigated the effect of melt percolation on Hf, Nd and Sr isotopic variations. Isotope systematics of the Lherz peridotites shows that a strong isotopic decoupling may arise at the melt percolation front between depleted harzburgite and refertilized lherzolite. The one-dimensional modelling used shows that these decoupled signatures are generated by porous flow and governed by critical parameters such as the concentrations of the elements in the melt to the matrix, chemical diffusivities or efficiency of isotopic homogenization. We observe that, under certain circumstances, melt-rock interactions can generate enriched, "intraplate-like" isotopic signatures in the transition zone between upwelling partial melts and lithospheric mantle.

These results suggest that a part of isotopic signatures of mantle-related rocks could be generated by diffusional processes associated with melt transport.

Table 1 -Crystallographic fabrics strengths of minerals Figure 1 -Crystal-preferred orientations of minerals (CPO) Table 2 -Major and minor elements compositions of minerals from Lherz peridotites Table 3 -Whole-rock chemical compositions -major and minor elements (ppm) Table 4 -Whole-rocks chemical compositions -trace elements (ppm) Table 5 -Whole-rocks chemical compositions -trace elements normalized to primitive mantle Figure 2 -Whole-rocks trace elements normalized to primitive mantle Table 6 -Modal compositions of Lherz peridotites Table 7 -REE clinopyroxenes concentrations (ppm) Table 8 -REE clinopyroxenes concentrations normalized to chondrites Figure 3 -REE clinopyroxenes concentrations normalized to chondrites Table 9 -Hf, Nd and Sr isotopic ratios of the Lherz peridotites Summary of chemical techniques and methods

Textural or chemical evidence for local refertilization has been mainly observed in plagioclase peridotites from ophiolitic [START_REF] Barth | Geochemitry of the Othris ophiolite, Greece: evidence for refertilization[END_REF][START_REF] Dijkstra | Structural Petrology of Plagioclase Peridotites in the West Othris Mountains (Greece): Melt Impregnation in Mantle Lithosphere[END_REF][START_REF] Takazawa | Geochemistry and origin of the basal lherzolites from the northern Oman ophiolite (northern Fizh block)[END_REF], abyssal [START_REF] Elthon | Chemical trends in abyssal peridotites: refertilization of depleted suboceanic mantle[END_REF][START_REF] Luguet | Laserablation microprobe (LAM)-ICPMS unravels the highly siderophile element geochemistry of the oceanic mantle[END_REF][START_REF] Paulick | Geochemistry of abyssal peridotites (Mid-Atlantic Ridge, 15°20′N, ODP Leg 209): Implications for fluid/rock interaction in slow spreading environments[END_REF][START_REF] Seyler | Clinopyroxene microtextures reveal incompletely extracted melts in abyssal peridotites[END_REF] and orogenic mantle suites [START_REF] Müntener | Refertilization of mantle peridotite in embryonic ocean basins: trace element and Nd isotopic evidence and implications for crust-mantle relationships[END_REF][START_REF] Nicolas | Origin of ophiolitic and oceanic lherzolites[END_REF][START_REF] Piccardo | Alpine-Apennine ophiolitic peridotites: new concepts on their composition and evolution[END_REF][START_REF] Rampone | Chemistry and origin of trapped melts in ophiolitic peridotites[END_REF][START_REF] Rampone | Melt impregnation in ophiolitic peridotite: an ion microprobe study of clinopyroxene and plagioclase[END_REF][START_REF] Saal | Re-Os Isotopes in the Horoman peridotite: evidence for refertilization[END_REF]. Refertilization was less commonly observed in spinel and garnet peridotites. In the Ronda massif (Spain), a significant part of the spinel lherzolites has been ascribed to the refertilization of subcontinental lithosphere by kilometer-scale porous melt flow [START_REF] Garrido | Diversity of mafic rocks in the Ronda peridotite: evidence for pervasive melt/rock reaction during heating of subcontinental lithosphere by upwelling asthenosphere[END_REF][START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF]Van der Wal and Bodinier, 1996). [START_REF] Rampone | Multi-stage melt-rock interaction in the Mt. Maggiore (Corsica, France) ophiolitic peridotites: microstructural and geochemical evidence[END_REF] also recently showed that spinel and plagioclase peridotites from the Mt. Maggiore (Corsica) underwent melt-rock reaction and melt impregnation, respectively, depending on the lithospheric depths at which interaction occurred. Likewise, garnet peridotites from the Western Gneiss Region (Norway) were recently reinterpreted as formed by refertilization of a dunitic Archean lithospheric mantle [START_REF] Beyer | Archean mantle fragments in Proterozoic crust, Western Gneiss Region, Norway[END_REF]Beyer et al., 2006). In addition to tectonicallyemplaced mantle rocks, an increasing set of observations on mantle xenoliths further strengthen the hypothesis that the refertilization process may be widespread in the mantle [START_REF] Carlson | Timing of Precambrian melt depletion and Phanerozoic refertilization events in the lithospheric mantle of the Wyoming Craton and adjacent Central Plains Orogen[END_REF][START_REF] Downes | Refertilization of highly depleted lithospheric mantle (Balkan peninsula, SE Europe): evidence from peridotite xenoliths[END_REF][START_REF] Tang | Refertilization of ancient lithospheric mantle beneath the central North China Craton: evidence from petrology and geochemistry of peridotite xenoliths[END_REF].

In the large Ronda massif (300 km2), the refertilization is associated to a melting front, that led to asthenospherization and attenuation of the lithospheric mantle [START_REF] Garrido | Diversity of mafic rocks in the Ronda peridotite: evidence for pervasive melt/rock reaction during heating of subcontinental lithosphere by upwelling asthenosphere[END_REF]Vauchez and Garrido 2001;[START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF]Van der Wal and Bodinier, 1996). Likewise, the refertilization in Lanzo has been ascribed to the 'asthenospherization' of subcontinental lithospheric mantle by upwelling asthenospheric melts during the early stages of oceanisation [START_REF] Müntener | Refertilization of mantle peridotite in embryonic ocean basins: trace element and Nd isotopic evidence and implications for crust-mantle relationships[END_REF]. Some authors have suggested that the presence of melt can weaken the lower lithosphere and accommodate its removal by mantle convection, initiating feedback processes and involving further thermo-chemical erosion.

The coexistence of depleted and fertile mantle rocks can be explained by different processes such as partial melting (e.g. [START_REF] Frey | The Ronda high temperature peridotite: geochemistry and petrogenesis[END_REF], melt-rock reactions (e.g. Downes 1991; [START_REF] Kelemen | Focused melt flow and localized deformation in the upper mantle: juxtaposition of replacive dunite and ductile shear zones in the Josephine peridotite, SW Oregon[END_REF] or convective mingling (Bodinier and Godard, 2003). The Lherz massif, type-locality of lherzolites, has been described as a piece of preserved fertile mantle.

However, the structural and chemical constraints provided by previous studies were insufficient to assess the mode of formation of the lherzolites-harzburgites alternations. The present work aims to re-investigate the Lherz massif peridotites, located in the French Pyrenees. At the end of 18 th century, De La Méthérie proposed the term "lherzolite", though he did not know at that time the precise mineralogical composition of the rock. The Lherz lherzolites were then successively investigated by [START_REF] Lacroix | Les péridotites des Pyrénées et les autres roches intrusives non feldspathiques qui les accompagnent[END_REF]), Ave Lallemant (1967) and [START_REF] Conquéré | Pétrologie des complexes ultramafiques de lherzolite à spinelle de l'Ariège (France)[END_REF]. For many decades the massif has been an inspiring source of debates, notably concerning melt processes in the mantle [START_REF] Bodinier | Geochemistry and petrogenesis of Eastern Pyrenean peridotites[END_REF]Bodinier et al., 1987a;[START_REF] Bodinier | Silicate, hydrous and carbonate metasomatism at Lherz, France: contemporaneous derivatives of silicate melt-harzburgite reaction[END_REF][START_REF] Bodinier | Mechanism of mantle metasomatism: Geochemical evidence from the Lherz orogenic peridotite[END_REF][START_REF] Burnham | The petrogenesis of eastern Pyrenean peridotites: an integrated study of their whole-rock geochemistry and Re-Os isotopic composition[END_REF][START_REF] Chaussidon | Sulphur isotope composition of orogenic spinel lherzolite massifs from Ariege (north-eastern Pyrenees, France): an ion microprobe study[END_REF][START_REF] Deloule | Hydrogen isotope heterogeneities in the mantle from ion probe analysis of amphiboles from ultramafic rocks[END_REF][START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF][START_REF] Fabriès | Petrogenetic evolution of orogenic lherzolite massifs in the central and western Pyrenees[END_REF][START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF][START_REF] Hamelin | Lead isotope study of orogenic lherzolite massifs[END_REF]Lorand, 1989;[START_REF] Lorand | Sulphide petrology and sulphur geochemistry of orogenic lherzolites: a comparative study of the Pyrenean bodies (France) and the Lanzo massif (Otaly)[END_REF][START_REF] Loubet | Trace elements in orogenic lherzolites reveal the complex history of the upper mantle[END_REF][START_REF] Mcpherson | Geochemistry of metasomatism adjacent to amphibole-bearing veins in the Lherz peridotite massif[END_REF][START_REF] Mukasa | Intrinsic Nd, Pb and Sr isotopic heterogeneities exhibited by the Lherz alpine peridotite massifs, French Pyrenees[END_REF][START_REF] Pattou | Non-chondritic platinum-group element ratios in the Earth's mantle[END_REF][START_REF] Polvé | Orogenic lherzolites complexes studied by 87 Rb-87 Sr: A clue to understanding the mantle convection processes?[END_REF]Reisberg and Lorand, 1995;[START_REF] Woodland | Metasomatic interactions in the lithospheric mantle: petrologic evidence from the Lherz Massif, French Pyrenees[END_REF][START_REF] Zanetti | Infiltration metasomatism at Lherz as monitored by systematic ion-microprobe investigations close to a hornblendite vein[END_REF]. So far, the Lherz lherzolites were traditionally considered as pristine rocks, close to the primitive mantle. The pristine origin of the lherzolites was commonly accepted and the chemical trends from lherzolites to harzburgites were generally attributed to partial melting. However in the Lherz massif, fertile lherzolites and depleted harzburgites are intermingled at the scale of tens of meters [START_REF] Avé Lallemant | Structural and petrographic analysis of an "alpine-type" peridotite. The lherzolite of French Pyrenees[END_REF][START_REF] Conquéré | Pétrologie des complexes ultramafiques de lherzolite à spinelle de l'Ariège (France)[END_REF][START_REF] Conquéré | Chemical disequilibrium and its thermal significance in spinel peridotites from the Lherz and Freychinède ultramafic bodies (Ariège, French Pyrenees)[END_REF][START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF] but show distinct isotopic signatures that are not consistent with a simple partial melting process (Bodinier and Godard, 2003;[START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF]. [START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF] proposed that the harzburgites were selectively percolated by enriched melts whereas Chapter I Bodinier and Godard (2003) interpreted the harzburgites as lithospheric strips incompletely mixed with pristine asthenospheric lherzolites during thermo-mechanical erosion of the lithosphere by upwelling mantle. However, previous structural maps of the Lherz massif did not detail the inner deformation structures of harzburgites and lherzolites [START_REF] Avé Lallemant | Structural and petrographic analysis of an "alpine-type" peridotite. The lherzolite of French Pyrenees[END_REF][START_REF] Conquéré | Pétrologie des complexes ultramafiques de lherzolite à spinelle de l'Ariège (France)[END_REF]. Thus to examine the different hypotheses, the first step of this study consisted in a detailed structural mapping of the Lherz ultramafic complex. This was the starting point of this work.

Geological setting of the Lherz massif

The Pyrenean peridotite massifs occur as restricted bodies scattered across Mesozoic sediments along the North Pyrenean Fault (NPF; Fig. 1). More than 40 peridotite massifs have been listed in the Pyrenees, with dimensions varying from several m 2 to 1 km 2 for the Lherz massif [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF][START_REF] Monchoux | Comparaison et classement des massifs de lherzolite de la zone mésozoïque Nord-Pyrénéenne[END_REF]. Additionally, some large massifs (2 x 3 km) crop out farther to the west [START_REF] Fabriès | Petrogenetic evolution of orogenic lherzolite massifs in the central and western Pyrenees[END_REF]. The Pyrenean orogenic peridotites are distributed in seven groups. To the east, the Salvezines, Prades-Bestiac, Vicdessos-Lherz, and Castillon groups form the eastern Pyrenean massifs. The Tuc Desse-Arguenos, Avezac-Moncaut and Turon de Técouère-Col d'Urdach groups form the central and western Pyrenean peridotite massifs. . Fig. 1: Distribution of the Pyrenean peridotite bodies along the North Pyrenean Fault, from [START_REF] Lagabrielle | Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites, French Pyrenees[END_REF] after [START_REF] Choukroune | Tectonique des plaques et Pyrénées: sur le fonctionnement de la faille transformante nord-pyrénéenne; comparaison avec des modèles actuels[END_REF]. 1: Oligocene and post-Oligocene sediments; 2: Mesozoic and Eocene sediments; 3: Paleozoic basement; 4: area of LP-HT Pyrenean metamorphism; 5: lherzolite bodies; 6: granulites; 7: main thrusts external zones; 8: North Pyrenean Fault.

Chapter I Pyrenean peridotites are generally embedded in sedimentary basins made of voluminous detrital formations (flyschs) related to tectonic instabilities and sedimentary transport. The North Pyrenean Metamorphic Zone (NPMZ) is a narrow (0-5 km wide) band of Mesozoic carbonate sediments of Jurassic to Aptian age (Fig. 3) affected by a low pressure -high temperature metamorphism [START_REF] Golberg | High temperature -low pressure Cretaceous metamorphism related to crustal thinning (Eastern North Pyrenean Zone, France[END_REF]) dated between 110 and 85 Ma, with a peak at 95Ma [START_REF] Albarède | Age and significance of the North Pyrenean metamorphism[END_REF][START_REF] Golberg | Données nouvelles et mise au point sur l'âge du métamorphisme pyrénéen[END_REF][START_REF] Golberg | Petrological and age relationship between emplacement of magmatic breccia, alkaline magmatism and static metamorphism in the North Pyrenean Zone[END_REF][START_REF] Montigny | K-Ar study of Cretaceaous magmatism and metamorphism of the Pyrenees: age and length of rotation of the Iberian Peninsula[END_REF]. The NPMZ also contains lenses of granulites [START_REF] Azambre | Les écailles de gneiss du faciès granulite du Port de Saleix et de la région de Lherz (Ariège). Nouveaux témoins du socle profond des Pyrénées[END_REF][START_REF] Vielzeuf | Crustal splitting and the emplacement of Pyrenean lherzolites and granulites[END_REF], breccias, and granulated agglomerates that contain a large variety of metamorphic minerals such as kornerupine, sapphirine, corundum, phlogopite or cordierite [START_REF] Monchoux | Roches à saphirine au contact des lherzolites pyrénéennes[END_REF]. [START_REF] Lagabrielle | Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites, French Pyrenees[END_REF] after [START_REF] Vielzeuf | Crustal splitting and the emplacement of Pyrenean lherzolites and granulites[END_REF] and [START_REF] Colchen | Carte géologique de la France au 1/50000, feuille 1086, Aulus-les-Bains[END_REF]. Thick dotted line delineates the region of polymictic debris-flow deposits [START_REF] Lagabrielle | Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites, French Pyrenees[END_REF]. Hatched area represents the region north of the main ultramafic bodies, where strongly deformed Mesozoic sediments are exposed, and where rare sedimentary clastic deposits have been observed.

Exhumation of Pyrenean peridotites is usually ascribed to lithospheric thinning associated with successive opening and closing of elongated, asymmetrical pull-apart basins in response to the dominantly transcurrent motion of the Iberian plate relative to the European plate in the Chapter I mid-Cretaceous [START_REF] Choukroune | Tectonique des plaques et Pyrénées: sur le fonctionnement de la faille transformante nord-pyrénéenne; comparaison avec des modèles actuels[END_REF][START_REF] Debroas | Modèle de bassin triangulaire à l'intersection de décrochements divergents pour le fossé albo-cénomanien de la Ballongue (zone nord-pyrénéenne, France)[END_REF][START_REF] Vielzeuf | Crustal splitting and the emplacement of Pyrenean lherzolites and granulites[END_REF].

The crustal emplacement of the central and eastern peridotite massifs has been dated at 110-105 by Ar-Ar and Sm-Nd methods on amphiboles and whole-rocks, respectively, from Lherz and Caussou [START_REF] Henry | Late mantle evolution of the Pyrenean sub-continental lithospheric mantle in the light of new 40 Ar-39 Ar and Sm-Nd ages on pyroxenites and peridotites (Pyrenees, France)[END_REF] but is probably older (109)(110)(111)(112)(113)(114)(115)(116)(117) in the western Pyrenees [START_REF] Fabriès | Petrogenetic evolution of orogenic lherzolite massifs in the central and western Pyrenees[END_REF]. Previous models of emplacement suggested purely tectonic mechanisms such as solid intrusion of mantle rocks into the sediments [START_REF] Minnigh | Quenching: an additional model for emplacement of the lherzolite at Lers (French Pyrenees)[END_REF][START_REF] Vielzeuf | Crustal splitting and the emplacement of Pyrenean lherzolites and granulites[END_REF]. On the other hand, [START_REF] Choukroune | La brèche de Lherz dite "d'explosion liée à la mise en place des lherzolites" est une brèche sédimentaire d'âge cénozoïque[END_REF], [START_REF] Fortané | Lherzolites and the Western "Chaînons Béarnais" (French Pyrenees): structural and paleogeographical pattern[END_REF] and more recently [START_REF] Lagabrielle | Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites, French Pyrenees[END_REF] proposed tectono-sedimentary models involving disintegration and transport of mantle rocks exhumed on the sea-floor (Fig. 4).

Fig. 3: Possible geological setting and mode of emplacement of the ultramafic bodies and associated clastic rocks [START_REF] Lagabrielle | Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites, French Pyrenees[END_REF]. Blue: Jurassic platform carbonates; pink: continental crust; green: mantle; 1: detachment leaving late foliation in mantle rocks; 2: LT shear zone(s), cataclasites (c) and exhumation to seafloor; 3: late normal faulting, weathering and brecciation; 4: gravity sliding and sedimentary reworking.

Meter-scale low-temperature mylonitic bands also cross-cut the massif; they are more common at the borders and are probably related to the emplacement of the massif in the crust [START_REF] Costa | Use of 40 Ar-39 Ar stepwise heating method for dating mylonitic zones: an example from the St. Barthelemy Massif (Northern Pyrenees, France)[END_REF].

Lithologies

The Pyrenean peridotite massifs are mostly composed of layered spinel lherzolites where the layering is defined by ubiquitous cm-to dm-thick parallel bands of websterite. The Pyrenean peridotites are equilibrated either in the Ariege subfacies (garnet in mafic layers) or Chapter I in the Seiland subfacies (mafic layers devoid of garnet) defined by [START_REF] O'hara | Mineral parageneses in ultramafic rocks[END_REF] and [START_REF] Obata | The origin of mafic layers in the Ronda high-temperature peridotite intrusion, S. Spain: an evidence of partial fusion and fractional crystallisation in the upper mantle, Orogenic mafic and ultramafic association 272[END_REF]. Eastern and Central Pyrenean peridotites are equilibrated either in the Ariege or Seiland spinel subfacies. The Lherz massif peridotites are equilibrated in the Ariege spinel subfacies and show petrological and geochemical characteristics typical of sub-continental lithosphere: equilibration temperatures of 800-900°C [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF]; old osmium ages (Reisberg and Lorand, 1995); metasomatic features comparable to those observed in mantle xenoliths [START_REF] Bodinier | Geochemistry and petrogenesis of Eastern Pyrenean peridotites[END_REF][START_REF] Bodinier | Mechanism of mantle metasomatism: Geochemical evidence from the Lherz orogenic peridotite[END_REF][START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF]. Besides, they are never associated with large gabbro or pillow-lavas formations of MORB affinity suggesting that they do not represent typical oceanic lithosphere. Western Pyrenean peridotites are equilibrated in the Seiland spinel subfacies and locally show incipient recrystallization in the plagioclase stability field [START_REF] Fabriès | Petrogenetic evolution of orogenic lherzolite massifs in the central and western Pyrenees[END_REF]. They are also more serpentinized than the Eastern bodies [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF]. This suggests that the westernmost Pyrenean peridotites reached a very shallow level in oceanic basins. They are considered to be transitional between the Lherz peridotites, which represent the subcontinental mantle, and the ocean-continent transition peridotites generally equilibrated at lower pressure, higher temperature and more affected by serpentinization (e.g. Lanzo).

Fig. 4: Cartography of the lherzolites and harzburgites of the Lherz massif from [START_REF] Conquéré | Pétrologie des complexes ultramafiques de lherzolite à spinelle de l'Ariège (France)[END_REF].

Chapter I Introduction 8 asymmetrical and isoclinal folds but more open folds are observed, especially in thick pyroxenite layers which have a higher resistance to deformation [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF]. The Lherz ultramafic complex is cross-cut by a late generation of amphibole-pyroxenite dykes (Bodinier et al., 1987b;[START_REF] Conquéré | Les pyroxénites à amphibole et les amphibolites associées aux lherzolites du gisement de Lherz (Ariège, France): un exemple du rôle de l'eau au cours de la cristallisation fractionnée des liquides issus de la fusion partielle des lherzolites[END_REF][START_REF] Vétil | Conditions de mise en place des filons des pyroxénites à amphibole du massif ultramafique de Lherz (Ariège, France)[END_REF] considered as high-pressure -high-temperature crystal segregates from alkaline basalts that migrated through the Pyrenean lithospheric mantle in the Cretaceous [START_REF] Bodinier | Mechanism of mantle metasomatism: Geochemical evidence from the Lherz orogenic peridotite[END_REF][START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF][START_REF] Golberg | Petrological and age relationship between emplacement of magmatic breccia, alkaline magmatism and static metamorphism in the North Pyrenean Zone[END_REF][START_REF] Loubet | Trace elements in orogenic lherzolites reveal the complex history of the upper mantle[END_REF][START_REF] Rossy | REE and Sr-Nd isotope geochemistry of the alkaline magmatism from the Cretaceous North Pyrenean Rift Zone (France-Spain)[END_REF] . Hornblendites veins ("lherzites") were also emplaced at a slightly later stage. They were ascribed to the segregation of volatile-rich, evolved melts after crystallization of anhydrous garnet Chapter I pyroxenites from the alkaline basalt [START_REF] Bodinier | Geochemistry and petrogenesis of Eastern Pyrenean peridotites[END_REF][START_REF] Wilshire | Amphibole-rich veins in lherzolite xenoliths, Dish Hill and Dead-man Lake, California[END_REF]Woodland et al., 1996).

Sampling

Chapter I Introduction 10

The Lherz peridotites have been sampled in different locations. Sampling restricted to the harzburgite-lherzolite contacts aim to observe small-scale variations whereas profiles along the massif provide information on larger-scale processes.

Presentation of the chapters

Following the introduction, the second chapter presents a combined structural and geochemical survey of the Lherz peridotites. The main conclusion of this chapter is that the lherzolites from the type-locality do not represent pristine asthenospheric material, as assumed in previous studies, but are secondary and formed through a refertilization process at the expense of an ancient harzburgitic protolith (Le Roux et al., 2007;published in EPSL).

In the last decade, the relationships between melt percolation and deformation have been studied mostly using an experimental approach. Based on the new model on the formation of the Lherz lherzolites developed in the second chapter, the Lherz massif has become an exceptional area to study interactions between percolation and deformation in mantle rocks of a natural system. Thus, chapter three develops the geodynamical implications of a refertilization episode, through a detailed microstructural and petrophysical study of the refertilized lherzolites. The main conclusion of this chapter is that the lherzolites record a feedback between melt percolation and deformation, leading to a contemporaneous localization of the deformation / percolation (Le Roux et al., 2008;published in EPSL). This feedback might play a significant role in the structuration of the lithospheric mantle.

Additionally, the consequences of magma transport on chemical/isotopic variations in the mantle are usually neglected. The third part of this work (fourth chapter) consists in a detailed investigation of Hf, Nd and Sr isotopic variations in the Lherz massif through a frozen melt percolation front materialized by the harzburgite-lherzolite contacts. The main conclusion of this chapter is that melt percolation through mantle rocks may produce transient isotopic signatures that do not reflect a simple mixing between the two source components. Thus, part Chapter I of mantle rocks isotopic variability could be generated by diffusional processes associated with melt transport rather than by mixing between individual reservoirs (Le Roux et al., 2008a;accepted to EPSL). Finally, the fifth chapter summarizes the main conclusions of this study, discusses some remaining, open questions and suggests work perspectives. For reader's convenience, all references are compiled at the end of this manuscript.

Details on the technical work are given at the beginning of supplementary material. Two published articles and a fourth article in preparation are also presented in this last section. extraction [START_REF] Bodinier | Geochemistry and petrogenesis of the Lanzo peridotite body[END_REF][START_REF] Frey | The Ronda high temperature peridotite: geochemistry and petrogenesis[END_REF]. Together with chondritic meteorites, these fertile lherzolites were used to infer the composition of the Earth's primitive mantle [START_REF] Mcdonough | The composition of the Earth[END_REF]. In this scheme, tectonically-emplaced peridotites massifs equilibrated in the plagioclase (Lanzo, Italy [START_REF] Bodinier | Geochemistry and petrogenesis of the Lanzo peridotite body[END_REF][START_REF] Boudier | Structural control on the partial melting of the Lanzo peridotite[END_REF]; Othris, Greece [START_REF] Menzies | Plagioclase lherzolite-residual mantle relationships within two eastern mediterranean ophiolites[END_REF]; Horoman, Japan [START_REF] Frey | Compositional variations within the lower layered zone of the Horoman peridotites, Hokkaido, Japan: constraints on models for melt-solid segregation[END_REF]), spinel (Ronda, Spain [START_REF] Dickey | Partial fusion products in Alpine-type peridotites: Serrania de La Ronda and other examples[END_REF][START_REF] Frey | The Ronda high temperature peridotite: geochemistry and petrogenesis[END_REF]; Lherz, France [START_REF] Bodinier | Geochemistry and petrogenesis of Eastern Pyrenean peridotites[END_REF]; Ivrea, Italy [START_REF] Hartmann | The composition of peridotites tectonites from the Ivrea complex (N-Italy) representing material at different stages of depletion[END_REF]) and garnet fields (Western Gneiss Region, Norway [START_REF] Carswell | Picritic magma -residual dunite relationships in garnet peridotite at Kalskaret near Tafjord, South Norway[END_REF])) were widely considered as residual mantle containing sparse remnants of pristine material. However, an increasing set of observations shows that lherzolites may also form by combined processes of partial melting and igneous refertilization.

Plagioclase lherzolites, in particular, are interpreted as products of impregnation of previously depleted peridotites by percolating melts [START_REF] Nicolas | Origin of ophiolitic and oceanic lherzolites[END_REF][START_REF] Piccardo | Alpine-Apennine ophiolitic peridotites: new concepts on their composition and evolution[END_REF][START_REF] Rampone | Chemistry and origin of trapped melts in ophiolitic peridotites[END_REF][START_REF] Rampone | Melt impregnation in ophiolitic peridotite: an ion microprobe study of clinopyroxene and plagioclase[END_REF][START_REF] Saal | Re-Os Isotopes in the Horoman peridotite: evidence for refertilization[END_REF]. [START_REF] Müntener | Refertilization of mantle peridotite in embryonic ocean basins: trace element and Nd isotopic evidence and implications for crust-mantle relationships[END_REF] have ascribed the formation of plagioclase peridotites in western Alps and Apennines to a reaction between extending lithosphere from embryonic ocean basins and upwelling asthenospheric melts. Spinel lherzolites from the Ronda Massif (S Spain) have also been ascribed to refertilization of subcontinental lithosphere [START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF]Van der Wal and Bodinier, 1996) . In Ronda, this process was coupled with thermal erosion and extensive melting of deeper lithospheric levels [START_REF] Garrido | Diversity of mafic rocks in the Ronda peridotite: evidence for pervasive melt/rock reaction during heating of subcontinental lithosphere by upwelling asthenosphere[END_REF][START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF]. Finally, Beyer et al. (2006) recently interpreted garnet peridotites and pyroxenites from the Western Gneiss Region This km-scale orogenic peridotite is therefore a natural laboratory to study the relations between depleted and fertile mantle

Geological background

The Pyrenean orogenic peridotites comprise about 40 distinct ultramafic bodies mainly composed of layered spinel lherzolites, with dimensions varying from a few m 2 to 1 km 2 in Lherz [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF]. Most massifs are spatially associated with crustal granulites [START_REF] Azambre | Les écailles de gneiss du faciès granulite du Port de Saleix et de la région de Lherz (Ariège). Nouveaux témoins du socle profond des Pyrénées[END_REF][START_REF] Vielzeuf | Crustal splitting and the emplacement of Pyrenean lherzolites and granulites[END_REF] [START_REF] Golberg | High temperature -low pressure Cretaceous metamorphism related to crustal thinning (Eastern North Pyrenean Zone, France[END_REF][START_REF] Montigny | K-Ar study of Cretaceaous magmatism and metamorphism of the Pyrenees: age and length of rotation of the Iberian Peninsula[END_REF].

Exhumation of mantle rocks is generally ascribed to transcurrent movement of the Iberian plate relative to Europe in the mid-Cretaceous, which resulted in crustal thinning associated with successive opening and closing of elongated, asymmetrical pullapart basins [START_REF] Choukroune | Tectonique des plaques et Pyrénées: sur le fonctionnement de la faille transformante nord-pyrénéenne; comparaison avec des modèles actuels[END_REF][START_REF] Debroas | Modèle de bassin triangulaire à l'intersection de décrochements divergents pour le fossé albo-cénomanien de la Ballongue (zone nord-pyrénéenne, France)[END_REF]. et al., 1987a;[START_REF] Conquéré | Les pyroxénites à amphibole et les amphibolites associées aux lherzolites du gisement de Lherz (Ariège, France): un exemple du rôle de l'eau au cours de la cristallisation fractionnée des liquides issus de la fusion partielle des lherzolites[END_REF][START_REF] Montigny | K-Ar study of Cretaceaous magmatism and metamorphism of the Pyrenees: age and length of rotation of the Iberian Peninsula[END_REF][START_REF] Vétil | Conditions de mise en place des filons des pyroxénites à amphibole du massif ultramafique de Lherz (Ariège, France)[END_REF] . Narrow metasomatized dyke wall rocks and hornblendites veins record limited melt infiltration in host peridotites (Bodinier et al., 2004;[START_REF] Bodinier | Mechanism of mantle metasomatism: Geochemical evidence from the Lherz orogenic peridotite[END_REF]. The final emplacement of the peridotites is marked by extensive brecciation in the outer rim of the Lherz body and in the host limestones. 1; Fig. 4). This feature reflects the presence of mm-scale websterite layers that are abundant near the contact with lherzolites. This is the case, for instance, in sample 05LA12 which is lherzolitic in terms of major-element and modal composition (10.7 % Cpx). However, this sample is distinguished from the "true" lherzolites from Lherz by lower Ti and much higher Cr contents (Fig. 4) and by mineral compositions typical of harzburgites ( 1) compared with literature data for mantle xenoliths and orogenic peridotites [START_REF] Canil | Midly incompatible elements in peridotites and the origins of mantle lithosphere[END_REF]. Empty squares = harzburgites; full circles = lherzolites. The variations observed within a few meters across harzburgite-lherzolite contacts in Lherz encompass almost the whole range of mantle peridotites worldwide.

increasing Al 2 O 3 traditionally ascribed to partial melting (Fig. 4). A more detailed analysis shows however that harzburgites and lherzolites tend to define distinct covariations trends, notably for minor elements. For instance the lherzolites are distinguished by slightly higher Ti contents at a given Al 2 O 3 value (Fig. 4). On a Cr vs.

Al 2 O 3 diagram, the difference between the harzburgite and lherzolite trends is striking:

while the harzburgites show a steep, steady positive correlation, the lherzolites display a Fig. 5: Chondrite-normalized [START_REF] Sun | Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes[END_REF]) REE patterns of clinopyroxenes in four representative peridotites, including harzburgites and lherzolites, both distal and adjacent to a harzburgitelherzolite contact (table 2).

curved trajectory trending towards a gentle, positive correlation in the most fertile samples (Fig. 4). From their wide range of Cr contents (600 to 7400ppm) and low Al 2 O 3 values (< 2.5%), the harzburgites resemble cratonic xenoliths, notably those equilibrated at shallow depth, in the stability field of spinel [START_REF] Canil | Midly incompatible elements in peridotites and the origins of mantle lithosphere[END_REF]. Conversely, the lherzolites show a narrow range of Cr contents (2400-4000ppm) and higher Al 2 O 3 comparable to the composition of other orogenic peridotites and off-craton mantle xenoliths.

The existence of two different trends for Cr in covariation diagrams is a reflection of the markedly distinct Cr contents in minerals from harzburgites and lherzolites (Table 2).

The Cr# number (= Cr/Cr+Al cationic ratio) of spinel, for instance, is in the range 0. unrelated to pyroxenite dykes and lherzolites [START_REF] Bodinier | Geochemistry and petrogenesis of Eastern Pyrenean peridotites[END_REF][START_REF] Bodinier | Silicate, hydrous and carbonate metasomatism at Lherz, France: contemporaneous derivatives of silicate melt-harzburgite reaction[END_REF].

Discussion

Structural relationships between harzburgitic protolith and secondary lherzolites

The constant orientation of the foliation and lineation in harzburgite bodies throughout the Lherz Massif (Fig. 1)

strongly suggests that all harzburgites were once part of a single and continuous unit.

This, together with the observation that the minor amphibole and sulphide phase, which started under static conditions and was followed by a deformation stage.

Formation of the lherzolites by refertilization reaction

Covariations of modal and majorelement compositions in the Lherz peridotites are comparable to those observed in several suites of mantle rocks worldwide.

These covariations were generally ascribed to variable degrees of partial melt extraction [START_REF] Bodinier | Geochemistry and petrogenesis of the Lanzo peridotite body[END_REF][START_REF] Canil | Midly incompatible elements in peridotites and the origins of mantle lithosphere[END_REF][START_REF] Frey | The Ronda high temperature peridotite: geochemistry and petrogenesis[END_REF], although in most cases variable degrees of refertilization of a refractory protolith would also account for the observed modal and chemical trends (Beyer et al., 2006) 1), emphasizing the two distinct covariations trends observed in lherzolites and harzburgites, respectively. The symbols for the samples are the same as in figure 4. The dashed lines represent mixing between a refractory harzburgite (intersection of the harzburgite and lherzolite trends) and variable proportions (in percent) of two distinct websterite components (grey triangles). The compositions of the websterite components were calculated from modal and mineral compositions. Modal compositions estimated by extrapolating those of the peridotites towards 0 % olivine are roughly identical for harzburgites and lherzolites (60% Opx, 34% Cpx and 6% Sp). Websterite mineral compositions were measured in thin (<1cm) websterite layers hosted by harzburgites and lherzolites. In both cases, the mineral compositions are similar in websterites and in their host peridotites, but they differ markedly between harzburgites and lherzolites. As a result, the two websterite components show distinct compositions, the one related to harzburgites being much more enriched in Cr than the one related to lherzolites. to those in lherzolites, as it is the case for thin (<10 cm) websterite layers in Lherz [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF] and other orogenic lherzolites [START_REF] Shervais | The Balmuccia orogenic lherzolite massif, Italy[END_REF].

The harzburgite trend is defined by harzburgite samples collected within a few meters from the contact with lherzolites and containing thin (~ mm) websterite seams (section 1 in table 1). These samples may be whole rocks for the harzburgites and lherzolites (same symbols as in Fig. 4). Error bars indicate the variation in Cpx composition at the sample scale. Grey symbols represent Cpx compositions recalculated for nearsolidus temperature (1250°C) using inter-mineral partition coefficients derived from [START_REF] Wood | Trace element partitioning under crustal and uppermost mantle conditions: the influences of ionic radius, cation charge, pressure, and temperature[END_REF]. Numerical models of TiO 2 variations during partial melting and magmatic refertilization are shown for comparison. For the melting model, we used the modal composition of the most fertile lherzolite, and its TiO 2 content in Cpx and whole rock, as the source composition. The melting reaction was taken from [START_REF] Walter | A mass proportion method for calculating melting reactions and application to melting of model upper mantle lherzolite[END_REF] and the mineral/melt partition coefficients from [START_REF] Wood | Trace element partitioning under crustal and uppermost mantle conditions: the influences of ionic radius, cation charge, pressure, and temperature[END_REF]. The results reported here were calculated with the fractional melting model. However, changing the melting model (e.g. for batch or incremental melting) does not significantly modify the variation trend of TiO 2 in Cpx vs. whole rock. Magmatic refertilization was simulated with the Plate Model of Vernières et al. (Vernières et al., 1997) applied to the following meltrock reaction: f i .melt i + x ol .Ol f r .melt r + x opx .Opx + x cpx .Cpx + x spl .Spl, where melt i and melt r stand for the infiltrated and residual melts, respectively, f i and f r for the corresponding melt mass fractions, x ol for the mass fraction of dissolved olivine, and x opx , x cpx and x spl for the mass fractions of crystallized Opx, Cpx, and Spl. Reaction parameters f i , f r , x ol , x opx , x cpx and x sp were adjusted to reproduce the modal variations and the Ti contents in Cpx and whole-rocks. The protolith is a highly refractory harzburgite (83% Ol, 15% Opx, 1.5% Cpx, 0.5% Spl, 0.02 wt.% TiO 2 in whole rock and 0.05 wt.% TiO 2 in Cpx). The Ti content of the infiltrated melt (TiO 2 = 2 wt.%) was derived from the composition of clinopyroxene in the most fertile lherzolite and Cpx/melt partition coefficients [START_REF] Wood | Trace element partitioning under crustal and uppermost mantle conditions: the influences of ionic radius, cation charge, pressure, and temperature[END_REF].

was derived from the composition of clinopyroxene in the most fertile lherzolite , 1997). This enrichment results from the segregation of HIE-and volatile-rich small melt fractions moving ahead of melt-consuming reaction fronts. This mechanism, also referred to as "percolative fractional crystallization" [START_REF] Harte | Mantle peridotites and processes-the kimberlite sample[END_REF], was advocated to explain enriched HIE compositions in "cryptically" metasomatized mantle xenoliths [START_REF] Bedini | Evolution of LILE-enriched small melt fractions in the lithospheric mantle: a case study from the East African Rift[END_REF] and in tens of centimetres-thick wall-rocks of alkaline dykes in Lherz [START_REF] Bodinier | Mechanism of mantle metasomatism: Geochemical evidence from the Lherz orogenic peridotite[END_REF]. In the case of the harzburgite-lherzolite contacts, the REE variation in harzburgite Cpx indicates that small melt fractions residual after the refertilization reaction migrated in the harzburgite protolith several meters (< 20 meters) ahead of the main reaction front.

Behind the reaction front, clinopyroxene REE compositions in lherzolites reflect the initial melt composition, which is depleted in LREE relative to HREE (i.e., similar to N-MORB).

Refertilization and isotopic variations

A striking feature of Pyrenean and several other orogenic peridotites is the existence of correlations between Os-Sr-Nd radiogenic isotopes and peridotite fertility (Bodinier and Godard, 2003;[START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF]Reisberg and Lorand, 1995). In the Pyrenees, the positive correlation between 187 Os/ 188 Os and Al 2 O 3 has been ascribed to a ~ 2.5 Ga-old depletion event considered to record partial melting and stabilization of lithospheric mantle in the Archean (Reisberg and Lorand, 1995). However, this hypothesis does not account for the negative correlation of 87 Sr/ 86 Sr and the positive correlation of 143 Nd/ 144 Nd with Al 2 O 3 . These covariations were ascribed either to selective percolation of enriched melts through the harzburgites [START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF] or to incomplete mixing of lithospheric strips (harzburgites) into asthenospheric material (lherzolites) during thermo-mechanical erosion of lithosphere by upwelling mantle (Bodinier and Godard, 2003). However, the first alternative implies unrealistically enriched melt compositions (Bodinier and Godard, 2003) previously suggested for the Horoman orogenic peridotite in Japan [START_REF] Saal | Re-Os Isotopes in the Horoman peridotite: evidence for refertilization[END_REF].

Refertilization fronts, a moving

lithosphere-asthenosphere boundary?

In the light of our convergent structural and geochemical arguments we suggest that the Lherz massif is a fossil lithosphereasthenosphere boundary, where a >2 Ga-old (Reisberg and Lorand, 1995) The ubiquitous websterite layers record higher melt/rock ratios and suggest smallscale anisotropic variations in the melt flux.

A possible origin for the websterite layering is refraction and channelling of percolating melts against the freezing horizon represented by eroded lithosphere [START_REF] Rabinowicz | The effect of sloped isotherms on melt migration in the shallow mantle: a physical and numerical model based on observations in the Oman ophiolite[END_REF][START_REF] Sparks | Melt extraction from the mantle beneath spreading centres[END_REF][START_REF] Spiegelman | Physics of melt extraction: theory, implications and applications[END_REF].

This hypothesis is consistent with the systematic parallelism of websterite layers and harzburgite-lherzolite contacts. It was already suggested for replacive websterite layers related to lithospheric thermal erosion in the Ronda peridotite [START_REF] Garrido | Diversity of mafic rocks in the Ronda peridotite: evidence for pervasive melt/rock reaction during heating of subcontinental lithosphere by upwelling asthenosphere[END_REF]. The low equilibrium temperatures recorded by pyroxene compositions in the Lherz peridotites [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF] imply that thermal relaxation occurred between the refertilization episode and the emplacement of the massif in the crust, in the Cretaceous.

Refertilization is thus probably related to the late-Variscan, post-collisional thermal event responsible for granulitic metamorphism in western Pyrenees [START_REF] Pin | Granulites and related rocks in Variscan median Europe: a dualistic interpretation[END_REF], which has been interpreted as the result of the destabilization of the thickened orogenic lithosphere.

Is the refertilization process specific to

Lherz? This is the first study showing convergent structural and geochemical data for extensive rejuvenation of refractory lithospheric mantle by refertilization.

However, textural or chemical evidence for igneous refertilization has been reported from tectonically-emplaced plagioclase lherzolites in New Caledonia [START_REF] Nicolas | Origin of ophiolitic and oceanic lherzolites[END_REF], western Alps (Müntener et al., 2004;[START_REF] Rampone | Melt impregnation in ophiolitic peridotite: an ion microprobe study of clinopyroxene and plagioclase[END_REF], Horoman [START_REF] Saal | Re-Os Isotopes in the Horoman peridotite: evidence for refertilization[END_REF], and from Cpx-poor lherzolites at the base of the Oman ophiolite [START_REF] Godard | Relationships between geochemistry and structure beneath a paleo-spreading centre: a study of the mantle section in the Oman Ophiolite[END_REF]. Recently Beyer et al. (2006) suggested the transformation of highly refractory (dunitic) Archean lithospheric mantle via igneous refertilization, producing garnet peridotites and pyroxenites. An association between refertilization and lithospheric thinning was proposed for the orogenic lherzolites of Ronda and Lanzo [START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF][START_REF] Müntener | Refertilization of mantle peridotite in embryonic ocean basins: trace element and Nd isotopic evidence and implications for crust-mantle relationships[END_REF]. The Ronda massif displays a narrow (<400m) refertilization front which separates a spinel tectonite domain interpreted as an old lithospheric mantle and a granular domain deeply modified by melting processes [START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF]Van der Wal and Bodinier, 1996). The Although recognized for at least two decades, this association, which is inconsistent with partial melting, was never given a satisfactory explanation.

Conclusions

The tightly linked to a partial melting domain below [START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF]Van der Wal and Bodinier, 1996). We can thus imagine that the refertilization front observed in the Lherz Massif also moved ahead of a melting front related to thermo-mechanical erosion of the lithosphere.

There is a growing body of evidence indicating that the chemical variations observed in tectonically-emplaced mantle rocks result from igneous refertilization superimposed onto previous depletion events. An important implication is that fertile lherzolites from peridotite massifs cannot be straightforwardly used to infer primitive mantle compositions. In this perspective, it is logic to wonder whether the fertile mantle xenoliths represent refertilized or pristine mantle. Several authors have ascribed the chemical stratification of cratonic lithosphere and/or its temporal evolution to metasomatic refertilization [START_REF] Griffin | The evolution of lithospheric mantle beneath the Kalahari Craton and its margins[END_REF][START_REF] Kopylova | Chemical stratification of cratonic lithosphere; constraints from the northern Slave Craton, Canada[END_REF][START_REF] Lee | Compositionally stratified cratonic lithosphere: petrology and geochemistry of peridotite xenoliths from the Labait Volcano, Tanzania[END_REF]. In this scheme, fertile (predominantly lherzolitic), off-craton lithosphere may be viewed as the ultimate transformation of cratonic lithosphere after one or several cycles of igneous refertilization. Extensive refertilization in the Western Alps and Betic peridotites is intrinsically related to the lithospheric thinning processes that led to mantle exhumation [START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF][START_REF] Müntener | Refertilization of mantle peridotite in embryonic ocean basins: trace element and Nd isotopic evidence and implications for crust-mantle relationships[END_REF][START_REF] Piccardo | Alpine-Apennine ophiolitic peridotites: new concepts on their composition and evolution[END_REF],

which

Magmatic refertilization probably plays

a key role in the rejuvenation and erosion of the lithospheric mantle. Seismological data suggest that the lithospheric mantle is strongly thinned in extensional environments [START_REF] Bastow | Upper-mantle seismic structure in a region of incipient continental breakup: northern Ethiopian rift[END_REF] and above mantle plumes [START_REF] Li | Rejuvenation of the lithosphere by the Hawaiian plume[END_REF]. Numerical models, however, predict that thermo-mechanical processes, like small-scale convective destabilization, only produce limited thinning (<30km) [START_REF] Thoraval | Plume-lithosphere interactions beneath a fastmoving plate[END_REF], due to the strong temperature dependence of the viscosity and slow heat conduction in the lithospheric mantle. Refertilization of the lithospheric mantle by asthenospheric melts may reconcile these contrasting observations.

Deformation experiments show that the presence of even a small fraction of basaltic melt results in a marked decrease of olivinerich rocks strength [START_REF] Hirth | Experimental constraints on the dynamics of the partially molten upper mantle: deformation in the dislocation creep regime[END_REF]. Progression of the melt infiltration front producing the refertilization will therefore reduce the viscosity and favor the destabilization and removal of the lithospheric mantle.

Introduction

The evolution of the upper mantle is strongly associated with partial melting and refertilization processes. Recent studies have shown that percolating melts may react with the mantle lithosphere, inducing enrichment in fusible components, i.e., refertilization via the crystallization of pyroxenes and spinel (Beyer et al., 2006;Le Roux et al., 2007;[START_REF] Lenoir | The recrystallization front of the Ronda peridotite: evidence for melting and thermal erosion of subcontinental lithospheric mantle beneath the Alboran Basin[END_REF][START_REF] Müntener | Refertilization of mantle peridotite in embryonic ocean basins: trace element and Nd isotopic evidence and implications for crust-mantle relationships[END_REF][START_REF] Rampone | Melt impregnation in ophiolitic peridotite: an ion microprobe study of clinopyroxene and plagioclase[END_REF]Tommasi et al., 2004).

Experimental deformation of partially molten assemblages shows that the presence of melt, even in low fractions, leads to a strong decrease in viscosity [START_REF] Hirth | Experimental constraints on the dynamics of the partially molten upper mantle: deformation in the dislocation creep regime[END_REF][START_REF] Rosenberg | Experimental deformation of partially melted granite revisited: implications for the continental crust[END_REF][START_REF] Takei | Deformation-induced grain boundary wetting and its effects on the acoustic and rheological properties of partially molten rock analogue[END_REF]. Additionally, deformation may produce a higher transient permeability and facilitate melt segregation [START_REF] Holtzman | Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow[END_REF][START_REF] Rosenberg | Syntectonic melt pathways during simple shearing of a partially molten rock analogue (Norcampher-Benzamide)[END_REF]. This feedback between melt percolation and deformation, observed experimentally, has also been proposed, on the basis of structural observations, as responsible for the development of shear zones in the middle and the lower crust [START_REF] Brown | Shear-zone systems and melts: feedback relations and selforganization in orogenic belts[END_REF][START_REF] Kisters | The role of strain localization in the segregation and ascent of anatectic melts, Namaqualand, South Africa[END_REF]Tommasi et al., 1994;Vauchez and Tommasi, 2003) and in the shallow mantle [START_REF] Kelemen | Focused melt flow and localized deformation in the upper mantle: juxtaposition of replacive dunite and ductile shear zones in the Josephine peridotite, SW Oregon[END_REF]. At the plate scale, it has also been suggested, based on geodynamical models and seismic anisotropy data, that magmas play an essential role in the initiation of rifting [START_REF] Buck | The role of magma in the development of the Afro-Arabian rift system[END_REF][START_REF] Kendall | Mantle upwellings, melt migration and the rifting of Africa: insights from seismic anisotropy[END_REF] and in the erosion of the lithosphere above mantle plumes [START_REF] Thoraval | Plume-lithosphere interactions beneath a fastmoving plate[END_REF]. Interactions between melt percolation and deformation in the mantle are thus major processes in the evolution of the lithosphere, controlling its composition and mechanical behavior. In this article we document still poorly understood feedback processes between melt percolation and deformation in a complex natural system: a propagating lithosphere-asthenosphere boundary.

The [START_REF] Azambre | Les écailles de gneiss du faciès granulite du Port de Saleix et de la région de Lherz (Ariège). Nouveaux témoins du socle profond des Pyrénées[END_REF][START_REF] Kornprobst | Transcurrent crustal thinning: a mechanism for the uplift of deep continental crust/upper mantle associations[END_REF][START_REF] Monchoux | Les lherzolites pyrénéennes: contribution à l'étude de leur minéralogie, de leur genèse et de leurs transformations[END_REF][START_REF] Vielzeuf | Pétrologie des écailles granulitiques de la région de Lherz (Ariège-Zone Nord Pyrénéenne). Introduction à l'étude expérimentale de l'association grenat(alm-py)feldspath potassique[END_REF] Chapter III

Le Roux et al. (2008), Feedback between melt percolation and deformation in an exhumed lithosphere-asthenosphere boundary 37

The Lherz peridotitic massif (Pyrenees, France)

The Lherz Massif, type-locality of the lherzolite, is one of the largest of the 40 ultramafic bodies that outcrop along the North Pyrenean Fault (NPF; Pyrenees, France; Fig. 1a). The Pyrenean peridotite massifs, which dimensions vary from several m 2 to a few km², with ~ 1 km 2 for the Lherz massif [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF][START_REF] Monchoux | Comparaison et classement des massifs de lherzolite de la zone mésozoïque Nord-Pyrénéenne[END_REF], are mainly composed of layered Cretaceous [START_REF] Choukroune | Tectonique des plaques et Pyrénées: sur le fonctionnement de la faille transformante nord-pyrénéenne; comparaison avec des modèles actuels[END_REF][START_REF] Debroas | Modèle de bassin triangulaire à l'intersection de décrochements divergents pour le fossé albo-cénomanien de la Ballongue (zone nord-pyrénéenne, France)[END_REF][START_REF] Vielzeuf | Crustal splitting and the emplacement of Pyrenean lherzolites and granulites[END_REF]. Most ultramafic massifs outcrop within carbonate rocks of Jurassic to

Aptian age affected by a low pressure-high temperature metamorphism that characterizes the 'North Pyrenean Metamorphic Zone' [START_REF] Golberg | High temperature -low pressure Cretaceous metamorphism related to crustal thinning (Eastern North Pyrenean Zone, France[END_REF], and they are generally associated with crustal granulites [START_REF] Azambre | Les écailles de gneiss du faciès granulite du Port de Saleix et de la région de Lherz (Ariège). Nouveaux témoins du socle profond des Pyrénées[END_REF][START_REF] Pin | Granulites and related rocks in Variscan median Europe: a dualistic interpretation[END_REF][START_REF] Vielzeuf | Crustal splitting and the emplacement of Pyrenean lherzolites and granulites[END_REF]. (2008), Feedback between melt percolation and deformation in an exhumed lithosphere-asthenosphere boundary 39 of them, except at the contact between the two lithologies. The entire massif is crosscut by a later generation of amphibole-bearing pyroxenite dykes and hornblendite veins, related to alkaline magmatism during the Cretaceous (Bodinier et al., 1987a;[START_REF] Golberg | Petrological and age relationship between emplacement of magmatic breccia, alkaline magmatism and static metamorphism in the North Pyrenean Zone[END_REF][START_REF] Loubet | Trace elements in orogenic lherzolites reveal the complex history of the upper mantle[END_REF][START_REF] Vétil | Conditions de mise en place des filons des pyroxénites à amphibole du massif ultramafique de Lherz (Ariège, France)[END_REF]. Meter-scale low-temperature mylonitic bands cross-cut the massif; they are more common at its borders and are probably related to the emplacement of the massif in the crust [START_REF] Costa | Use of 40 Ar-39 Ar stepwise heating method for dating mylonitic zones: an example from the St. Barthelemy Massif (Northern Pyrenees, France)[END_REF].

The harzburgites generally occur as Clinopyroxenes and orthopyroxenes are 3-4 mm on average, but orthopyroxene may attain up to 1 cm (Fig. 3d). The largest orthopyroxene and clinopyroxene crystals usually show strong wavy extinction and subgrains. Spinels display irregular shapes.

Evolution of CPO through the

Lherz Massif

Sampling and Methods

To investigate the evolution of the deformation in refertilized lherzolites and associated websterites through the Lherz massif, we sampled harzburgite-lherzolite contacts, proximal lherzolites close to the contacts with harzburgites (<30m), distal lherzolites (> 30m from the contact) and their associated websterites in the western part of the massif where they dominate (Fig. 1b). The orientation of the olivine CPO in the harzburgites is consistent throughout the massif. Its intensity, characterized by J ol (Table 1) varies from point to point; CPO are strong (J ol >8) away from the contacts, but more variable (J ol varying from 10 to 4, with an average close to 7) within 10m of the contacts (Fig. 7). Orthopyroxene CPO in the Although more dispersed, clinopyroxenes CPO are similar to that of the orthopyroxenes (Fig. 8a).

The harzburgite-lherzolite contacts are marked by a significant decrease of the olivine CPO from the harzburgites to the lherzolites with J ol varying from 7 on normal and parallel to the foliation, respectively (Fig. 8a).

In the distal (> 30m from the contact), layered lherzolites that outcrop in the northern and western part of the Lherz massif, olivine CPO is always weak: J ol ranges between 4.4 and 1.7 (J ol =3 on average; Table 1 & Fig. 7). These lherzolites Orthopyroxene CPO in distal lherzolites are also weak, but well-correlated with the olivine CPO (Fig. 8a). Finally, some distal lherzolites from the western part of the massif, show an olivine CPO uncorrelated to the olivine shape preferred orientation that marks a clear foliation and lineation (Fig. 8b). In these peculiar lherzolites, the maximum concentration of [100] axes of olivine is oblique (ca. 40-50°) to the elongation of olivine crystals. In contrast, pyroxenes CPO show a good correlation with the olivine shape preferred orientation;

[001] axes of clino-and orthopyroxenes are preferentially aligned parallel to the direction of elongation of olivine crystals (Fig. 8b).

Distal lherzolites are always associated with cm-scale websteritic layers in which olivine and pyroxene display a weak CPO (Fig. 8c). Olivine CPO is usually characterized by [010]-fiber patterns and J ol varying from 3.6 to 1.7 (J ol =2.6 on average; [START_REF] Ben Ismaïl | The Kaapvaal craton seismic anisotropy: petrophysical analyses of upper mantle kimberlite nodules[END_REF]Vauchez et al., 2005) and in mantle xenoliths from oceanic islands [START_REF] Bascou | An integrated study of microstructural, geochemical and seismic properties of lithospheric mantle above the Kerguelen plume (Indian Ocean)[END_REF]. The development of such patterns has been explained by: (i) axial shortening or 3D transpressive deformation [START_REF] Bascou | An integrated study of microstructural, geochemical and seismic properties of lithospheric mantle above the Kerguelen plume (Indian Ocean)[END_REF]Tommasi et al., 1999),

(ii) activation of multiple glide directions [START_REF] Mainprice | Pressure sensitivity of olivine slip systems and seismic anisotropy of the Earth's upper mantle[END_REF]Tommasi et al., 2000), (iii) static recrystallization (Tommasi et al., 2008), and (iv) deformation in presence of melt [START_REF] Holtzman | Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow[END_REF].

The

Formation of a pervasive websteritic layering in refertilized lherzolites

The refertilization process in the Lherz massif resulted in the formation of both massive lherzolites and of mm-to tens of cm-scale websteritic layers parallel to the foliation of the lherzolites. The websteritic layering is pervasive in the distal lherzolites, but cm-wide websteritic bands are also often observed at the harzburgite-lherzolite contacts. The chemical composition of these websterites shows that they do not represent simple crystallized trapped melts (Bodinier et al., 1987b). We interpret therefore these websteritic layers as zones of melt segregation, favored by strain, where higher melt fractions resulted in more developed

Chapter III

Le Roux et al. (2008), Feedback between melt percolation and deformation in an exhumed lithosphere-asthenosphere boundary 53 refertilization reactions (dissolution of larger volumes of olivine and crystallization of larger amounts of pyroxenes and spinels).

However, the actual volume of melts needed to form these layers cannot be assessed accurately. [START_REF] Holtzman | Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow[END_REF] showed that in olivine + basalt + chromite or FeS, anorthite + basalt, and in olivine + albite melt samples deformed under simple shear, melt segregates into a network of melt-rich bands.

Analysis of these results as well as numerical models suggest that segregation is controlled by pressure gradients and depends therefore on the compaction length of the system, which is a function of the permeability and of the solid and fluid viscosities [START_REF] Hofmann | Sampling mantle heterogeneity through oceanic basalts: isotopes and trace elements[END_REF][START_REF] Rabinowicz | The effect of sloped isotherms on melt migration in the shallow mantle: a physical and numerical model based on observations in the Oman ophiolite[END_REF][START_REF] Spiegelman | Physics of melt extraction: theory, implications and applications[END_REF]. In the Lherz massif, thermal relaxation episode [START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF][START_REF] Sautter | Cooling kinetics of garnet websterites from the Freychinède orogenic lherzolite massif, French Pyrenees[END_REF]. This long thermal relaxation rules out the idea that the refertilization episode occurred during the emplacement of the massif in the crust, since this later is inferred to have occurred in

Chapter III

Le Roux et al. (2008), Feedback between melt percolation and deformation in an exhumed lithosphere-asthenosphere boundary 54 <5m.y. throughout the Pyrenees [START_REF] Fabriès | Petrogenetic evolution of orogenic lherzolite massifs in the central and western Pyrenees[END_REF][START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF][START_REF] Schärer | Gabbro and related rock emplacement beneath rifting continental crust: U-Pb geochronological and geochemical constraints for the Galicia passive margin (Spain)[END_REF].

Seismic anisotropy measurements in the

Pyrenees led [START_REF] Barruol | Lithospheric anisotropy beneath the Pyrenees from shear wave splitting[END_REF] [START_REF] Choukroune | The ECORS deep reflection seismic survey across the Pyrenees[END_REF]). An Hercynian orogenic fabric therefore appears as the best candidate to explain the observed S-wave anisotropy [START_REF] Barruol | Lithospheric anisotropy beneath the Pyrenees from shear wave splitting[END_REF]Vauchez and Barruol, 1996). The late stages of the Hercynian

Introduction

Mantle rocks that outcrop at the Earth's surface provide a direct source of information on the composition and evolution of the Earth's mantle. Isotopes systematics observed in most peridotite massifs [START_REF] Reisberg | Extreme isotopic variations in the upper mantle: Evidence from Ronda[END_REF][START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF]Pearson and Nowell, 2004) and mantle xenoliths [START_REF] Deng | Proterozoic depletion of the lithosphere recorded in mantle xenoliths from Inner Mongolia[END_REF]Witt-Eickschen and Kramm, 1997;[START_REF] Bizimis | Hf-Nd isotope decoupling in the oceanic lithosphere: constraints from spinel peridotites from Oahu, Hawaii[END_REF][START_REF] Wittig | U-Th-Pb and Lu-Hf isotopic constraints on teh evolution of the sub-continental lithospheric mantle, French Massif Central[END_REF] show a wide range of variations compared with single suites of mantlederived lavas. Some of the isotopic variations observed in peridotite massifs are correlated with lithologies, e.g. pyroxenites vs. peridotites [START_REF] Reisberg | Extreme isotopic variations in the upper mantle: Evidence from Ronda[END_REF]Pearson and Nowell, 2004) and have been ascribed to convective mingling of subducted material with pristine material [START_REF] Allègre | Implications of a two-component marble-cake mantle[END_REF][START_REF] Becker | Geochemistry of garnet peridotite massifs from lower Austria and the composition of deep lithosphere beneath a Paleozoic convergent plate margin[END_REF]. Other, small scale heterogeneities are ascribed to isotopic enrichment by metasomatizing fluids/melts superimposed onto ancient depletion due to melt extraction [START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF][START_REF] Bizimis | Hf-Nd isotope decoupling in the oceanic lithosphere: constraints from spinel peridotites from Oahu, Hawaii[END_REF][START_REF] Wittig | U-Th-Pb and Lu-Hf isotopic constraints on teh evolution of the sub-continental lithospheric mantle, French Massif Central[END_REF]. The time integration of both depletion and enrichment of parent elements is often considered as the primary cause of isotopic variations in lithospheric peridotites.

However, few studies have tackled the relationships between isotopic variations and metasomatic processes (e.g. [START_REF] Ionov | Sr-Nd-Pb isotopic compositions of peridotite xenoliths from Spitsbergen: numerical modelling indicates Sr-Nd decoupling in the mantle by melt percolation metasomatism[END_REF][START_REF] Bodinier | Silicate, hydrous and carbonate metasomatism at Lherz, France: contemporaneous derivatives of silicate melt-harzburgite reaction[END_REF]). Therefore, the mechanisms of isotopic enrichment and inter-isotopes decoupling during mantle metasomatism are still barely understood.

Additionally, the "instantaneous" (as opposed to "time-integrated") effect of melt transport on isotopes systematics is usually neglected, although it may theoretically generate drastic fractionation of daughter elements from different isotopic systems [START_REF] Navon | Geochemical consequence of melt percolation: the upper mantle as a chromatographic column[END_REF]. Further

Background and sampling

The Lherz massif is one of the largest peridotite massifs in the Pyrenees (France), exhumed from the mantle around 105 Ma ago [START_REF] Henry | Late mantle evolution of the Pyrenean sub-continental lithospheric mantle in the light of new 40 Ar-39 Ar and Sm-Nd ages on pyroxenites and peridotites (Pyrenees, France)[END_REF]) and exposed within sedimentary basins of Cretaceous age.

Pyrenean peridotites usually outcrop embedded in metamorphized carbonate sediments of Jurassic to Aptian age [START_REF] Golberg | High temperature -low pressure Cretaceous metamorphism related to crustal thinning (Eastern North Pyrenean Zone, France[END_REF] scattered in small groups along the North Pyrenean Fault [START_REF] Monchoux | Comparaison et classement des massifs de lherzolite de la zone mésozoïque Nord-Pyrénéenne[END_REF][START_REF] Fabriès | Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs[END_REF]; Fig. 1a). We present here the Hf, Nd and Sr isotopic compositions of clinopyroxene separates, considered to have similar isotopic signatures to the whole-rocks, and their rareearth elements compositions obtained during this study. [Hf] blank = 64±31 pg (n=3). The results are given in Table 1.

Samples preparation and analytical methods

Rare

Results

REE obtained in clinopyroxenes from the

sixteen peridotites sampled for this work (Table 1) show strongly depleted, U-shaped patterns in distal harzburgite bodies with La N =0.5 and (La/Sm) N ~2 (normalized to chondrites after [START_REF] Sun | Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes[END_REF] and classic, N-MORB, REE pattern in the distal lherzolite (La N =2.3; (La/Sm) N ~0.3), as observed in orogenic lherzolites worldwide [START_REF] Mcdonough | Rare earth elements in upper mantle rocks[END_REF]. At the (Pearson and Nowell, 2004), cratonic and off-craton peridotites (Pearson and Nowell, 2004), MORB [START_REF] Vervoort | Relationships between Lu-Hf and Sm-Nd isotopic systems in the global sedimentary system[END_REF]Nowell et al. 1998) and Ocean-Island Basalts -OIB - [START_REF] Salters | Hf isotope constraints on mantle evolution[END_REF] [START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF] are also shown for comparison. (b) 143 Nd/ 144 Nd versus 87 Sr/ 86 Sr for the same clinopyroxene separates compared with the fields of Pyrenean peridotites (Downes, 1991), MORB, OIB and HIMU [START_REF] Hofmann | Mantle geochemistry: the message from oceanic volcanism[END_REF][START_REF] Zindler | Chemical geodynamics[END_REF] and reference therein). The isotopic data for this study have been measured by TIMS and MC-ICP-MS techniques and corrected to 105 Ma, the age of exhumation. The differences between corrected and non-corrected isotopic ratios range between 1*10 -6 to 5*10 -6 .

2.1Ga on the protolith sample (06LI15), slightly younger than the ~2.2 Ga previously published Re depletion model ages (Reisberg and Lorand, 1995) and ~2.5 Ga in-situ Os model age [START_REF] Alard | Mantle refertilisation, Osmium isotopes and the "Primitive Upper Mantle" fallacy, consequences for the nature of the late veneer[END_REF]. However, giving the variations of T CHUR Hf model ages in harzburgitic samples, uncertainty on this age is probably high. The 'distal' harzburgitic sample which combines a Ushaped, highly REE-depleted signature (Fig.

2

) and the most enriched isotopic composition is considered to be the closest to the depleted protolith before refertilization.

The second pole is represented by a distal refertilized lherzolite characterized by a MORB-like isotopic signature (ε Hf ≈ 18 ; ε Nd ≈ 9; 87 Sr/ 86 Sr = 0.702562) and a LREEdepleted signature (Fig. 2). Other Pyrenean lherzolites that contain no visible harzburgites are isotopically comparable to the distal Lherz lherzolite [START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF][START_REF] Mukasa | Intrinsic Nd, Pb and Sr isotopic heterogeneities exhibited by the Lherz alpine peridotite massifs, French Pyrenees[END_REF]Fig. 3), suggesting a similar origin by regional magmatic refertilization. their Hf-Nd isotopic signatures (Fig. 3).

Discussion

Contrasted isotopic compositions of lherzolites and harzburgites in the Pyrenees

Previous works have revealed that fertile lherzolites and depleted harzburgites in eastern Pyrenean peridotites show markedly distinct Os-Sr-Nd isotopic signatures [START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF]Reisberg and Lorand, 1995;[START_REF] Burnham | The petrogenesis of eastern Pyrenean peridotites: an integrated study of their whole-rock geochemistry and Re-Os isotopic composition[END_REF]. The positive correlation of 187 Os/ 188 Os with Al 2 O 3 wt% has been ascribed to an old (Proterozoic) depletion event (Reisberg and Lorand, 1995;[START_REF] Burnham | The petrogenesis of eastern Pyrenean peridotites: an integrated study of their whole-rock geochemistry and Re-Os isotopic composition[END_REF]. However, 87 Sr/ 86 Sr and 143 Nd/ 144 Nd show, respectively, negative and positive correlations with Al 2 O 3 wt% in whole-rocks, a feature which is not consistent with partial melting (Downes et al., 1991;Bodinier and Godard, 2003). [START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF] proposed that the Lherz harzburgites were selectively percolated by enriched melts whereas Bodinier and Godard (2003) The Nd and Sr isotopic variations observed in this study, from the harzburgitic protolith to the refertilized lherzolites, are consistent with previously published data in the Pyrenees [START_REF] Downes | REE and Sr-Nd isotopic geochemistry of Eastern Pyrenean peridotite massifs: Sub-continental lithospheric mantle modified by continental magmatism[END_REF]. We obtained a Nd-Sr negative correlation which can be roughly accounted for by mixing between a low-Nd/high-Sr harzburgite protolith and a melt in equilibrium with the high-Nd/low-Sr distal lherzolite (Fig. 3b).

However, at the harzburgite-lherzolite contacts, the Hf isotopes are strongly decoupled from Nd (Fig. 3a) and Sr (not shown). In contrast with the Nd-Sr isotopic covariation, the Hf-Nd isotopic signatures observed at the harzburgite-lherzolite contact cannot be accounted for by mixing between the harzburgite protolith and a melt in equilibrium with the distal lherzolites (Fig. 3a). In a mixing scheme, these isotopic

Modeling of isotopic reequilibration during melt percolation

We have evaluated the influence of melt percolation on isotopic reequilibration between peridotite and an infiltrated melt using a one-dimensional percolationdiffusion model (Vasseur et al., 1991) modified to include isotopic homogenization.

The (1998), [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, orthorpyroxene, clinopyroxene and basaltic melt[END_REF][START_REF] Mcdade | Trace element partitioning on the Tinaquillo Lherzolite solidus at 1.5 GPa[END_REF]. The diffusivity of the elements in interstitial melt is the same for the three elements and fixed at 10 -8 cm 2 .s -1 [START_REF] Lesher | Kinetics of Sr and Nd exchange in silicate liquids: theory, experiments, and applications to uphill diffusion, isotopic equilibration, and irreversible mixing of magmas[END_REF].

For simplicity, the chemical diffusivities in solid phases, d, were considered to be identical for all minerals. Extrapolated at element diffusivity in minerals (Fig. 4a), (2) average grain size of minerals (Fig. 4b), [START_REF] Chou | presented at the Proc. Lunar Planet. Sci Conf 9th[END_REF] compositional contrast between protolith and melt for the daughter elements Hf and Nd (Fig. 4c), and ( 4) critical distance of isotopic homogenization along the percolation column (Fig. 4d).

The convex-upward Hf-Nd isotopic covariation trend observed for high element diffusivities in minerals (Fig. 4a) and/or small grain sizes (Fig. 4b) is consistent with the chromatography theory of trace-element reequilibration in porous flow systems [START_REF] Navon | Geochemical consequence of melt percolation: the upper mantle as a chromatographic column[END_REF]. The latter predicts that if the critical time of mineral/melt reequilibration by diffusion is short enough compared to the critical time of percolation (Vasseur et al., 1991) then Nd reequilibrates at lower melt/rock ratio than Hf due to its higher incompatibility degree, e.g. Kd Cpx/melt = 0.30 for Nd compared with 0.37 for Hf [START_REF] Blundy | Heavy REE are compatible in clinopyroxene on the spinel-lherzolite solidus[END_REF]. This type of Hf-Nd decoupling is also in agreement with the classical assumption that Hf is more robust to mantle metasomatism than Nd (e.g. [START_REF] Bedini | Isotopic constraints on the cooling of the continental lithosphere[END_REF]. Conversely, in the limiting case where the critical distance of isotopic homogenization is of the same length as the percolating column, the result of the percolationdiffusion experiment is similar to that of a mixing between the protolith and the melt (Fig. 4d).

The Lherz data are best explained by a strongly convex-downward Hf-Nd trend (heavy line on figure 4). Within the range of parameters fixed from our petrographical observations (mineralogy and grain size), geochemical data (protolith and inferred melt composition) and published experimental works (partition and diffusion coefficients), this Hf-Nd variation implies that the critical size of the isotopic homogenization volumes was ≤ 1m during the melt percolation event.

The dispersion observed for a few samples may be accounted for by subtle variations of critical parameters such as the mineral grain size, or the Hf-Nd content in peridotite or percolating melt.

In contrast with the Hf-Nd isotopic covariations, the modeled Nd-Sr trends are generally hardly distinguishable from the mixing curves in the range of the parameter values constrained by the Lherz data and experimental works (Fig. 5). Within this range of parameters, most experiments yield moderately convex-downward trajectories consistent with the chromatographic theory which predicts that Sr reequilibrates at lower melt/rock ratio than Nd due to its higher incompatibility degree, e.g. Kd Cpx/melt = 0.074 for Sr compared with 0.30 for Nd [START_REF] Blundy | Heavy REE are compatible in clinopyroxene on the spinel-lherzolite solidus[END_REF]. Noticeable exceptions are the experiments involving relatively high Nd melt /Nd matrix ratios (Fig. 5c). As previously noted by [START_REF] Ionov | Sr-Nd-Pb isotopic compositions of peridotite xenoliths from Spitsbergen: numerical modelling indicates Sr-Nd decoupling in the mantle by melt percolation metasomatism[END_REF] [START_REF] Reisberg | Extreme isotopic variations in the upper mantle: Evidence from Ronda[END_REF] or in xenoliths from the French Massif Central [START_REF] Downes | Textural, isotopic and REE variations in spinel peridotite xenoliths, Massif Central, France[END_REF]. The world-wide association of LREE-enriched harzburgites with LREEdepleted lherzolites, as observed in Lherz, suggests that the interaction of percolating melts with the lithospheric mantle is a widespread process. We observe that, under certain circumstances, these interactions can generate enriched, "intraplate-like" isotopic signatures in the transition zone between the two contrasting components. These results

suggest that a part of isotopic signatures of mantle-related rocks could be generated by diffusional processes associated with melt transport.

Chapter V: Conclusion and outlook

The present work provides structural evidence that the lherzolites from the Lherz massif, considered as pristine, are actually secondary and formed at the expense of a depleted harzburgitic protolith. Variations of major, minor and trace elements in minerals and wholerocks peridotites show that the lherzolites result from igneous refertilization reaction between depleted lithospheric mantle and percolating MORB-type partial melts. Local evidence of igneous refertilization has been previously reported in orogenic peridotites. At Lherz, structural arguments show that the whole lherzolite body is secondary and refertilized. As a result, the Lherz massif, type-locality of lherzolites, now represents a case study for the refertilization process in the mantle (Le Roux et al., 2007). Therefore the Lherz massif represents a "frozen" photograph of transient percolation stages in an old refractory lithosphere.

Implications of this result are wide. Not only for the composition of the primitive mantle itself, a major problem in the mantle community, but also for the evolution of the mantle lithosphere and the role of refertilisation in the structural and chemical evolution of the lithospheric mantle. These implications are detailed below.

Together with mantle xenoliths and chondrites, the Lherz massif has been used to infer the composition of the primitive upper mantle, in particular for the highly siderophile elements. However, the formation of the Lherz lherzolites by igneous refertilization raises the question of the validity and significance of the primitive mantle values based on fertile mantle rocks compositions. In this context, primitive mantle values needs to be re-assessed. In particular, the Os-isotope primitive upper mantle composition has major implications for the debate on the "late veneer" composition, the late meteorite bombardment that occurred on Earth after core segregation [START_REF] Alard | Mantle refertilisation, Osmium isotopes and the "Primitive Upper Mantle" fallacy, consequences for the nature of the late veneer[END_REF]supplementary material).

Evidence of melt percolation observed in previous studies of orogenic peridotites worldwide and in the Lherz massif suggests that a fundamental characteristic of most orogenic lherzolites is their refertilized nature. This suggests that magmatic percolation plays a significant role in the structural, chemical and isotopic evolution of the lithospheric mantle, contributing to its rejuvenation and thermo-mechanical erosion through time.

This work has revealed that the Lherz massif represents a natural example for feedback between melt percolation and deformation of mantle rocks (Le Roux et al., 2008b), providing natural observations consistent with experimental results [START_REF] Holtzman | Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow[END_REF]. Multiple deformation episodes have been observed via a detailed microstructural study combined with analyses of crystallographic fabrics of minerals in harzburgites, lherzolites and websterites.

Depleted harzburgites, percolated lherzolites and related websterites show a continuum of deformation suggesting that larger melt fractions favor strain localization and, in turn, larger strain favor melt percolation through a higher dynamic viscosity. This feedback effect may constitute a major process in the structural evolution of the lithosphere. Indeed it has been suggested for instance that the presence of melt in the lithosphere may reduce its viscosity, favoring the development of rift systems. Therefore, the refertilization process could also play a major role during orogenic stages, favoring the restructuration of the lithosphere.

The progressive deformation observed in the percolated lherzolites with increasing distance to the harzburgitic protolith shows that, in presence of melts, an increase in strain intensity may be associated with a decrease in crystallographic fabrics of minerals. This can be explained by a progressive increase of diffusion-creep accommodated deformation at the expense of dislocation-creep accommodated deformation. Moreover, the development of either [100]-fiber or [010]-fiber in olivines observed in peridotites worldwide may depend on a subtle balance between the strain intensity and the volume of percolating melts.

Synchronous to the refertilization episode, the development of a pervasive websteritic banding in lherzolites is also commonly observed in mantle rocks. In the Pyrenean massifs, the websteritic layers probably formed through melt segregation favored by the refertilization reaction which plugged the melt network, and represent multiple "frozen" timesteps of a dynamic melt transport system. However, considering that the websterites does not represent simple crystallized trapped melts, the quantification of the volume of melts which has percolated through the Lherz mantle rocks remains an open question.

The third part of this work has shown that melt percolation by diffuse porous flow is likely to produce a large range of isotopic signatures. The models show that melt percolation may be an alternative way to produce isotopic signatures previously restricted to mantle reservoirs signatures. Indeed, a large range of Hf, Nd and Sr isotopic variations is observed at the transition zone between depleted harzburgites and fertile lherzolites of the Lherz massif, suggesting that significant isotopic decoupling can be produced at a melt percolation front.

Chapter V

Conclusion 79

The decoupled signatures cannot be explained by a mixing line between the percolated rock and the percolating melt. Modelling of isotopic variations associated with melt infiltration

shows that the nature and extent of isotopic decoupling strongly depends on (1) the compositional contrast between protolith and melt with respect to daughter elements (2) the chemical diffusion rates of the elements and ( 3) the critical times of solid-liquid chemical reequilibration and isotopic homogenization.

Mantle rocks worldwide show a large isotopic variability and interactions between partial melts and lithospheric mantle have often been observed both in xenoliths and orogenic peridotites. Thus, a part of the mantle isotopic variability observed in mantle rocks may not be necessarily representative of the global earth mantle but rather related to percolation processes that affect the lithosphere-asthenosphere boundary. To some extent, the percolation-diffusion process could be responsible for some of the isotopic signatures observed in intraplate lavas, that may originate from melt-rock interactions at the lithosphere-asthenosphere boundary.

However, the importance of the isotopic variability originated by this process needs to be further evaluated.

Technical work

After I realized the detailed structural map of the Lherz massif, I have sampled, cut with diamond saw and prepared in proper dimensions for thin sections all the Lherz peridotites studied during this work (~ 160 samples). The thin sections have been realized by Christophe Nevado and Doriane Delmas (Géosciences Montpellier).

The thin sections were used for optical observations (~ 160 thin sections), EPMA and LASER-ICPMS (~ 55 thin sections each) analyses, and manual and automatic EBSD measurements that I have performed (~ 50 thin sections).

I have crushed the whole-rocks into powders (~ 60 samples). I performed a chemical digestion of some of them in the clean lab of Geosciences Montpellier and some others in the clean lab of GEMOC ARC National Key Centre. I made the ICPMS measurements with the help of Olivier Bruguier (Montpellier) and Suzy Elhlou (Sydney). (Figure 1), inconsistent with partial melting 13,15,16 . Elements such as Na and Ti, which

The Os-sulphide paradox

Despite the compatible nature of Os, which should give the Re-Os isotopic system a degree of immunity to metasomatic processes, the isotopic composition of Os commonly is modified during melt-rock percolation-reaction processes 22-26 . This paradox stems from the highly mobile and reactive nature of, the base-metal sulphides 27 , which are the main host phase for Os in mantle rocks. Due to their low melting temperature and low viscosity, and their affinity for volatile-rich fluids 28,29 sulphides are extremely mobile and reactive in the mantle 23,24,30,31 . As predicted by modeling and whole-rock observations 32-34 and demonstrated by in-situ analyses 27 and experimental studies 35,36 this mobility is accompanied by severe fractionation of the HSE. For instance, Pd/Ir may vary by several orders of magnitude between sulphide grains a few 10-100s of micrometers apart 24,27,30,31,37,38 , and sulphides from the same sample may show extreme isotopic heterogeneity 23,24,26,39,40 reflecting their contrasting petrogenetic history, i.e. residual after melting or metasomatically introduced. sulphides, Table RM1). Then we extended our study to the regional scale by investigating "historical" samples -used to estimate the HSE and Os-isotope composition of the PUM 6,7,10 -from Lherz and other peridotite massifs in the Pyrenées (188 sulphides from 12 samples, Table RM1).

Whole-rock data show that these samples also display the Al 2 O 3 -Pd/Ir -187 Os/ 188 Os correlation, which is the backbone of the PUM estimate (Figure 2). The likelihood of metasomatic enrichment is indicated in the Pyrenées massifs by (1) the fact that the Pd/Ir vs Al 2 O 3 correlation yields an extremely fractionated fertile mantle (Figure 2a) that is incompatible with the composition of the three main groups of chondrite 11 ; (2) although partition coefficients for Pd and Ir are loosely constrained 35 a linear correlation between Pd/Ir and Al 2 O 3 is not predicted by melt modeling 25,32 ; (3) pyroxenites (probable melts) fall on the correlation lines defined by the peridotites (Figure 2b).

Harzburgites have low sulfur contents (S ≤50 ppm); each thin section contains 0 to 2 small sulphide grains (≤50µm). In contrast, Fig. 2: Symbols as in figure 1; Histogram: black, carbonaceous chondrites; grey, ordinary chondrites; stippled, enstatite chondrites. Chondrite compositions after ref. 8,11 ; PUM composition after ref. 6,7,10 . Beni Bousera massif (Morocco) 43 and for some pyroxenites in the Ronda massif (Spain) 44 . The initial Os-isotope composition of the spinel-websterites is within error of a MORB composition at that time, consistent with lithophile element abundances 14 and isotopic data 45 . 1). Histogram of whole-rock compositions 10,18,19,42 . Right column shows the 187 Os/ 188 Os distribution in single whole-rock samples from the same outcrop, a few meters wide (Figure 1, repository material). Technical limitations inherent to the in-situ technique 25 mean that samples with high Re/Os ( 187 Re/ 188 Os>0.7) and/or low Os sulphides (<1ppm) suffer large errors, and the 187 Os/ 188 Os of sulphide having 187 Re/ 188 Os >1 cannot be determined. Consequently the sulphide population presented here is slightly biased toward sulphides with high Os contents and low Re/Os. Vertical solid and dashed lines denote the estimated 187 Os/ 188 Os composition and uncertainty (respectively) of a hypothetical Primitve Upper Mantle 6,7,10 ; Shaded region indicates minimum 187 Os/ 188 Os deduced from whole-rock alumino-isochron 18,19 .

Thus the whole-rock 187 Os/ 188 Os and Re/Os composition of the Pyrenées lherzolites do not reflect partial melting but simply the precipitation of sulphides having the high metal/sulphide ratio and fractionated HSE patterns 27,37 predicted by experimental work 35,36,46 However, the existence of linear 187 Os/ 188 Os-Al 2 O 3 trends and the intersection foci (0.127-0.131) of these trends on a worldwide basis at a fertile composition (Al 2 O 3 =4.2±0.2 wt.%) remains an important constraint on the large-scale, long-term evolution of the Proterozoic lithospheric mantle 6 . Data from the literature suggest that re-fertilisation processes described here are extremely common; they have been described in several localities worldwide and from a variety of geodynamic settings: Orogenic peridotite massifs 26,32,33,47,48 ;

ophiolites 38,49 , abyssal peridotite 24,32,34,42 , sub-continental mantle xenoliths 23,31,33,50 .

Furthermore, many mantle suites, including those used in estimates of the PUM composition 6,10 show the same "symptoms"

as the Lherz and Pyrenées massifs. These include (1) behaviour of major-and minor elements inconsistent with melting models;

( Further work has shown that this observation is not an aberration, but is rather systematic; a broad inverse correlation between Nd and Os isotopes is found on a worldwide basis, similar to that observed in the Pyrenées peridotite massifs (Figure 5). Therefore, we conclude that a large proportion of the subcontinental lithospheric mantle has been refertilised, as suggested by the ubiquitous radiogenic Os composition of the "fertile" upper mantle.

This suggests that a fundamental characteristic of the lithospheric mantle is its refertilised nature. 0,658 0,013 0,12841 0,0003 -0,04 0,00 0,08 0,00 *Sr collection -8ml.

-Strontium was then collected by adding 8ml of 2.5N HCl. Samples were then dried and had a drop of concentrated HNO 3 added to remove any organics from the resin.

-The dried sample was then ready for analysis on the TIMS instrument.

-Before Nd could be collected, 7ml of 6N HCl was added to elute Lu.

*Nd collection -Nd was then eluted by adding a 6-7ml of 6N HCl.

-Samples are then dried at 150°C and then a drop of concentrated HNO 3 is added to remove organics derived from the resin.

This fraction also contains many other REE such as Ce and Sm which then need to be removed by a subsequent column.

* Cleaning columns (1) -15ml of 4N HF.

-Backflush with 25ml MQ water.

-10ml of 6N HCl.

-15ml of 2.5NHCl/0.1N HF. To recondition the columns.

-5ml of 2.5N HCl/0.1N HF before loading next sample.

*Columns (2) -Further purification of the Hf fraction.

-The H 2 O 2 and 6NHCl step as described above is repeated to reduce chromium.

-The dried down samples then had 1.4ml of 0.5N HCl/0.5N HF ready for the column.

*Cleaning columns (2)

-Full reservoir of 4N HF.

-Full reservoir of 6N HCl.

-Full reservoir of 0.5N HCl/0.5N HF.

-4ml 0.5N HCl/0.5N HF before loading.

*Washing columns -Load the 1.4ml samples Biorad® AG1-X8 (100-200 mesh) anion exchange resin.

-4cm Biorad plastic poly prep columns are used. 2.7ml of resin (wet) is added.

-Add 1ml of 0.5N HCl/0.5N HF in the column and wait until passed through the column. Repeat 2 times.

-Add 16ml of 0.5N HCl/0.5N HF.

*Hf is then collected by adding 10ml of 6N HCl.

-A few drops of HCLO 4 are added to the cut and the samples are put on the hotplate at 170°C until all of the HCLO 4 has dried down. This step is repeated 2 times and then 1.4ml 2.5N HCl is added, ready for the 3 rd Hf column.

*Column: 3 rd Hf separation column.

-Add some drops of H 2 O 2 before loading. (Ti indicator).

-Load the 1.4ml samples in Teflon columns (13cm with 6.4mm ID) with 4.2 ml AG50W-X8 cation exchange resin.

-Add 1ml of 2.5N HCl in the column and wait until passed through the column. Repeat 2 times. A total of 5ml of 2.5N HCl (enough to elute all of the Ti) is added before the Hf is collected.

*Hf collection -12ml of 2.5N HCl/ 0.1N HF.

- -Full reservoir of 0.25N HCl.

*Loading -The dried fraction from the first column is redissolved in 0.7ml 0.05M HNO 3 and then loaded onto a column containing Eichrom® Ln Spec resin. The sample is loaded stepwise in 3x 0.2ml + 1x 0.1ml increments.

-Add 3x0.1ml of 0.25N HCl to wash sample onto resin.

-Add 0.75ml of 0.25N HCl (remove Ba) -Add 0.75ml of 0.25N HCl (remove La) -Add 1.25ml of 0.25N HCl (remove Ce) -Add 0.6ml of 0.25N HCl (remove Pr) *Nd collection -3ml of 0.25N HCl. Dry overnight at 120°C. Sample beakers may be wrapped in aluminium foil to prevent static electricity once the sample has been dried down.

Résumé

La différenciation du manteau lithosphérique s'est principalement effectuée par fusion partielle et extraction de magmas. Les harzburgites sont généralement considérées comme des résidus de fusion tandis que les lherzolites représentent un manteau originel peu affecté par la fusion. Cependant, certaines péridotites orogéniques montrent des évidences de refertilisation magmatique. Dans ce contexte, ce travail remet en cause la nature primitive des lherzolites de Lherz (Pyrénées), lithotype de la lherzolite.

Les données structurales et géochimiques montrent que ces lherzolites ne représentent pas du manteau préservé mais qu'elles se sont formées par une réaction de refertilisation entre un liquide de type MORB et une lithosphère réfractaire. De plus, les orientations préférentielles de réseau (OPR) des minéraux montrent une forte interdépendance entre la percolation magmatique et la déformation finie observée dans les roches percolées. Les variations d'OPR semblent contrôlées par un équilibre subtil entre fraction de liquide instantanée et taux de déformation local.

Ce travail a également abordé les effets de la percolation magmatique sur la variabilité isotopique des roches mantelliques. Les résultats montrent qu'un fort découplage isotopique peut s'observer dans un front de percolation. Les modèles suggèrent que le découplage des signatures isotopiques se produit pendant la percolation, gouverné par le rapport des concentrations en éléments (magma/matrice), la diffusivité et le processus d'homogénéisation isotopique. Les réactions magma/roche peuvent générer des signatures isotopiques de type intraplaque. Ceci suggère qu'une part des signatures isotopiques des roches ou laves dérivées du manteau pourrait être produite par des processus diffusionnels associés à du transport de magma.

Mots-clés : Massif de Lherz ; refertilisation ; réaction magma/roche ; érosion du manteau lithosphérique ; ségrégation de magmas ; localisation de la déformation ; diffusion ; découplage isotopique ; transport de magmas.

Melt-rock interactions and melt-assisted deformation in the Lherz peridotite, with implications for the structural, chemical and isotopic evolution of the lithospheric mantle Differentiation of the lithospheric mantle occurred principally through partial melting and extraction of melts. Harzburgites are generally considered as melting residues whereas lherzolites are regarded as pristine mantle weakly affected by melting. However, some orogenic peridotites show evidence of igneous refertilization. In this context, this work re-investigates the nature of the Lherz lherzolites (Pyrenees), type-locality of lherzolites, described as a piece of preserved fertile mantle.

Structural and geochemical data show that these lherzolites are not pristine but formed through a refertilization reaction between MORB-like melts and refractory lithosphere. Moreover, the Lherz peridotites were partly used to infer the composition of the primitive upper mantle and these results may have important implications for the nature of the late veneer.

Additionally, crystal-preferred orientations of minerals (CPO) highlight a strong feedback between melt percolation and finite strain in the percolated rocks. CPO variations are ruled by a subtle balance between instantaneous melt fraction and local strain rate.

This work also investigated the effect of melt percolation on Hf, Nd and Sr isotopes. Isotope systematics in Lherz shows that strong isotopic decoupling may arise in a percolation front. The modelling suggests that decoupled isotopic signatures are generated during porous flow and governed by the melt/matrix elements concentrations, chemical diffusivities or efficiency of isotopic homogenization. Melt-rock interactions can generate "intraplate-like" isotopic signatures. This suggests that a part of isotopic signatures of mantle-related rocks could be generated by diffusional processes associated with melt transport. Keywords: Lherz massif; refertilization; melt-rock reaction; erosion of lithospheric mantle; melt segregation; strain localization; diffusion; isotopic decoupling; melt transport. Discipline : Sciences de la Terre Laboratoire : Géosciences Montpellier (UMR 5243). Place Eugène Bataillon 34095 MONTPELLIER cedex 5. FRANCE

Fig. 2 :

 2 Fig. 2: Simplified geological map of the Aulus-Lherz region redrawn by[START_REF] Lagabrielle | Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites, French Pyrenees[END_REF] after[START_REF] Vielzeuf | Crustal splitting and the emplacement of Pyrenean lherzolites and granulites[END_REF] and[START_REF] Colchen | Carte géologique de la France au 1/50000, feuille 1086, Aulus-les-Bains[END_REF]. Thick dotted line delineates the region of polymictic debris-flow deposits[START_REF] Lagabrielle | Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites, French Pyrenees[END_REF]. Hatched area represents the region north of the main ultramafic bodies, where strongly deformed Mesozoic sediments are exposed, and where rare sedimentary clastic deposits have been observed.

Fig. 5 :

 5 Fig. 5: (a) small websteritic "disk-like" pockets in depleted harzburgites; (b) the size of the websteritic pockets increases when approaching the contact with lherzolites; (c) Cr-rich websteritic bands close to a harzburgitelherzolite contact; (d) a harzburgite-lherzolite contact underlined by a thin websteritic banding; (e) pervasive websteritic layering in the lherzolites; (f) some websteritic bands may locally attain tens of centimeters; (g) amphibole-pyroxenite dykes; (h) hornblendite veins; (i) carbonate-peridotite breccias.

(

Fig. 1 :

 1 Fig. 1: (a) Geological map of the Lherz peridotite massif showing anastomosed fertile lherzolites enclosing irregularly-shaped refractory harzburgite bodies. Foliation in harzburgites shows a constant N40-N60 orientation with a gentle southward dip, while lherzolite foliation and websterite layering show variable directions and a steep southward dip. Right insert: localization of the massif. (b) 3-D bloc diagram of the upper part of the massif made after the dips of websterite layering at the contact

Fig. 2 :

 2 Fig. 2: Print of the fossil harzburgitic foliation in harzburgites (Hz) close to the contact, cross-cut by a latter mm-scale websteritic layering (W) related to the refertilization. The thin layering superimposed to the harzburgitic foliation initiates the development of cmscale websteritic veins.

Fig. 3 :

 3 Fig. 3: Change in microstructure (left), from high-temperature porphyroclastic to coarse-granular, and associated weakening of olivine crystallographic preferred orientations (right) across two harzburgite-lherzolite contacts (sections 1 and 2). The presented CPO are representative of all measured CPO through the contacts. Microstructures are from samples collected within 1m from the contact, marked by cm-scale websterite banding. Microstructures were hand-drawn from thin sections; white: olivine, dashed lines mark subgrain boundaries; light grey: enstatite, dark grey: clinopyroxene; black: spinel. Olivine CPO are presented as lower-hemisphere equal area stereographic projections in a geographic reference frame (top to North); >130 individual grain measurements; contours at 0.5 multiple of a uniform distribution intervals. Solid lines: foliation; dashed lines: websterite layering; empty stars: lineation.

  those forming small isolated bodies, show a penetrative shallowly-dipping foliation with a constant N40-60°E orientation which is marked by elongated spinels and olivine porphyroclasts. The contact with the lherzolites is often sharp and steep, and underlined by a cmscale websteritic layering. Near the contact (<1m) with harzburgites, the lherzolites are generally coarse-grained and show a weak foliation. This foliation is variable in orientation (N10 to N80), steeply dipping towards the east or south, and generally oblique on the harzburgite foliation (Figs. 1&2). Both layering and foliation in the lherzolites tend to wrap the contact with the harzburgite bodies. Away from the contact, extinction. Close to the contact, websterites and Cpx-poor lherzolites have coarser, more equant grains, but intracrystalline deformation features are still observed in olivine crystals. Spinels are interstitial and display no shape-preferred orientation. Farther from the contact,

  -rock major-and trace-element contents, and modal compositions, of Lherz peridotites collected along two sections across harzburgite-lherzolite contacts and in distal peridotites harz. = harzburgite; harz.* = harzburgite with thin (~mm) websterite layers; lherz. = lherzolite. LOI = loss on ignition; Mg# = Mg/Mg+Fe cationic ratio. Measurements were performed manually (i.e. indexing of every crystal was verified by the operator) on grain by grain basis along 2 mm-spacing profiles parallel to the long axis of the thin section. The change in microstructure is associated with a variation in both orientation and strength of olivine crystal-preferred orientations (CPO). Harzburgites exhibit a strong olivine CPO, characterized by alignment of [100] axes close to the lineation and a girdle distribution of [010] and [001] with a maximum of [010] normal to the foliation. At the contact, olivine CPO in the lherzolites is weaker but the orientation of the 3 maxima is preserved. In the lherzolites close to the contact, the weakening of the CPO is stronger, with a strong dispersion of [100] parallel to the layering but the orientation of [010] and [001] maxima is similar to the one in the harzburgites. Farther the contact, [010] axes are reoriented and the maximum concentration is normal to the lherzolite foliation.

  28-0.41 in harzburgites compared with 0.069-0.104 in lherzolites. This bimodal distribution of mineral compositions is also observed for Mg# (= Mg/Mg+Fe cationic ratio) in olivine and minor elements such as Ti in pyroxenes. The forsterite value of olivine (Fo) is 0.905-0.915 in harzburgites, compared with 0.890-0.899 in lherzolites, and TiO 2 in clinopyroxene is 0.02-0.06 wt% in harzburgites, compared with 0.12-0.20 wt% in for lherzolites. Rare earth elements (REE) in clinopyroxene display a wide range of concentrations and variable chondritenormalized REE patterns (Table 3; Fig. 5). In the core of the thickest harzburgite bodies (> 10m), clinopyroxene shows strongly depleted, U-shaped REE patterns. These REE patterns mimic the whole-rock patterns previously reported for harzburgites

  al. (2007), The Lherz spinel lherzolite: refertilized rather than pristine mantle In lherzolites away from contacts (> 20 m), clinopyroxene displays the classic, N-MORB, REE pattern observed in orogenic lherzolites worldwide (McDonough and Frey, 1989). This pattern is relatively enriched in heavy REE but selectively depleted in light REE. Within a few meters from the contact, both lherzolite and harzburgite show more LREE-enriched clinopyroxenes than their distal counterparts. The variations observed in harzburgites are especially striking: the REE content of clinopyroxene increases by a factor of 5 (heavy REE) to 10 (light REE) from the core of the harzburgite bodies to the contacts.

  steeply dipping lherzolite foliation and websterite layering cross-cut the shallowly dipping harzburgite foliation, indicates that the deformation of the harzburgites predates the formation of the lherzolites and websterites. Such structural relationships between harzburgites and lherzolites, visible throughout the intermingled zone and at the massif-scale (Fig. 1), clearly indicate that the lherzolites are secondary rocks compared to harzburgites. The harzburgite bodies represent the remnants of a highly refractory mantle protolith largely replaced by the lherzolites. Analysis of microstructures and olivine CPO suggest deformation of harzburgites by dislocation creep with activation of the hightemperature, low-stress (010) [100] slip system. The formation of the lherzolites and websterites modifies both the microstructure and the CPO of the harzburgitic protolith. by grain growth, occurs at the contact, the re-orientation of the [100] and [010] axis of olivine, parallel to the lineation and perpendicular to the lherzolite foliation respectively, is only observed at some distance from the contact (>1-2m). At the contact, lherzolites show larger and more equant grains and olivine CPO are quite similar to harzburgites, but weaker. The increase in grain size and the dispersion of the olivine CPO in lherzolites through harzburgite-lherzolite contacts may be due to static recrystallization and crystallization of new randomly-oriented olivine crystals during melt-rock reactions (Tommasi et al., 2004). The more pronounced growth of Opx and Cpx together with the increase in their modal proportions Chapter II Le Roux et al. (2007), The Lherz spinel lherzolite: refertilized rather than pristine mantle suggest that they represent the main crystallization products of the reaction. Far from the contact, olivine microstructures and CPO are consistent with the steeply-dipping foliations and sub-horizontal lineations observed at the macroscopic scale. These observations suggest that melt percolation and melt-rock reactions started at static conditions, leading to changes in modal composition, grain growth and dispersion of olivine CPO. This percolation produced an anastomosed lherzolite network in which the later deformation producing the steeply dipping foliations was localised.

  melt extraction, refertilization of a refractory protolith involving precipitation of Cr-and Al-bearing minerals, mostly spinel and pyroxenes, can explain both the positive Cr vs. Al 2 O 3 correlations and the existence of distinct Cr arrays for harzburgites and lherzolites (Fig. 6). In this model, the intersection of the harzburgite and lherzolite trends at low (<1%) Al 2 O 3 content indicates the composition of the refractory protolith before refertilization. The lherzolite trend is interpreted as a linear mixing line between the depleted protolith composition and 30-60 wt% of an aluminous websterite component (60% Opx, 34% Cpx, 6% Spl). Mineral compositions in the websterite are identical

  to cation exchange between the peridotite and the percolating melt[START_REF] Navon | Geochemical consequence of melt percolation: the upper mantle as a chromatographic column[END_REF]. The coincidence of the Cr chromatographic front with the harzburgite-lherzolite contact indicates a significant drop in the melt fraction across the reaction front as a result of partial melt consumption by the reaction[START_REF] Bodinier | Silicate, hydrous and carbonate metasomatism at Lherz, France: contemporaneous derivatives of silicate melt-harzburgite reaction[END_REF]. Titanium differs from chromium in showing closely spaced, almost aligned covariation trends for harzburgites and lherzolites on the TiO 2 vs. Al 2 O 3 diagram (Fig. 4). Hence the two arrays may be overlooked and viewed as a single correlation recording variable degrees of partial melting. However, the distribution of Ti in Cpx precludes this process. It is roughly constant in lherzolites and drops abruptly in harzburgites, whereas melting models predict a gradual decrease of Ti contents in both whole rocks and minerals (Fig. 7). When recalculated for near-solidus, high-temperature conditions (1250°C), the bimodal distribution of Ti in Cpx is less pronounced but the discrepancy with the melting models remains significant. As shown on figure 7, the distribution of Ti can be successfully reproduced with a numerical simulation of refertilization involving a pyroxene-and spinel-forming reaction (Vernières et al., 1997). Based on the intersections of the harzburgite and lherzolites trends on Cr vs. modal and majorelement composition diagrams (e.g., Fig 6), the protolith is assumed to be a highly refractory harzburgite (1.5% Cpx, 0.02 wt% TiO 2 ). The Ti content of the infiltrated melt

Fig. 7 :

 7 Fig. 7: TiO 2 concentrations in clinopyroxene vs.whole rocks for the harzburgites and lherzolites (same symbols as in Fig.4). Error bars indicate the variation in Cpx composition at the sample scale. Grey symbols represent Cpx compositions recalculated for nearsolidus temperature (1250°C) using inter-mineral partition coefficients derived from[START_REF] Wood | Trace element partitioning under crustal and uppermost mantle conditions: the influences of ionic radius, cation charge, pressure, and temperature[END_REF]. Numerical models of TiO 2 variations during partial melting and magmatic refertilization are shown for comparison. For the melting model, we used the modal composition of the most fertile lherzolite, and its TiO 2 content in Cpx and whole rock, as the source composition. The melting reaction was taken from[START_REF] Walter | A mass proportion method for calculating melting reactions and application to melting of model upper mantle lherzolite[END_REF] and the mineral/melt partition coefficients from[START_REF] Wood | Trace element partitioning under crustal and uppermost mantle conditions: the influences of ionic radius, cation charge, pressure, and temperature[END_REF]. The results reported here were calculated with the fractional melting model. However, changing the melting model (e.g. for batch or incremental melting) does not significantly modify the variation trend of TiO 2 in Cpx vs. whole rock. Magmatic refertilization was simulated with the Plate Model of Vernières et al.(Vernières et al., 1997) applied to the following meltrock reaction: f i .melt i + x ol .Ol f r .melt r + x opx .Opx + x cpx .Cpx + x spl .Spl, where melt i and melt r stand for the infiltrated and residual melts, respectively, f i and f r for the corresponding melt mass fractions, x ol for the mass fraction of dissolved olivine, and x opx , x cpx and x spl for the mass fractions of crystallized Opx, Cpx, and Spl. Reaction parameters f i , f r , x ol , x opx , x cpx and x sp were adjusted to reproduce the modal variations and the Ti contents in Cpx and whole-rocks. The protolith is a highly refractory harzburgite (83% Ol, 15% Opx, 1.5% Cpx, 0.5% Spl, 0.02 wt.% TiO 2 in whole rock and 0.05 wt.% TiO 2 in Cpx). The Ti content of the infiltrated melt (TiO 2 = 2 wt.%) was derived from the composition of clinopyroxene in the most fertile lherzolite and Cpx/melt partition coefficients[START_REF] Wood | Trace element partitioning under crustal and uppermost mantle conditions: the influences of ionic radius, cation charge, pressure, and temperature[END_REF].

  refertilization front of the Lherz massif may have been associated with such a melting front below. In the Cr vs Al 2 O 3 diagram, several suites of mantle rocks show variations comparable to those observed in the Lherz massif (Fig. 4). These variations are hardly consistent with partial melting and may suggest that the majority of lherzolites observed at the Earth surface record refertilization processes. The refertilization mechanism also provides a key to understand the paradoxical association of LREE-enriched harzburgites with LREEdepleted lherzolites often observed in mantle xenoliths and in tectonically-emplaced peridotites (McDonough and Frey, 1989).

  Lherz Massif, lithotype of the lherzolite, is an exceptional area for studying the structural and geochemical evolution of the sub-continental lithospheric mantle. Detailed structural mapping reveals that the Lherz spinel lherzolites are secondary rocks formed at the expense of harzburgites, which represent remnant bodies of an old (>2Ga) and highly refractory protolith. Petrological and geochemical data show that the lherzolite-websterite suite has been formed by a near-solidus refertilization reaction involving crystallization of pyroxene and spinel, and dissolution of olivine. The irregular-shaped harzburgite-lherzolite contact thus materializes an anastomosed refertilization front formed by coalescence of melt infiltration channels. This evolution starts under static conditions but is followed by localization of the deformation in the refertilized domains. Upwelling of basaltic partial melts through the lithospheric mantle was associated with the migration of an important refertilization front. At a largerscale, the Ronda Massif (S Spain) also displays a refertilization front which is

  may suggest that large-scale refertilization is specific of tectonicallyemplaced, orogenic peridotites. However, the Lherz massif illustrates a situation where refertilization and exhumation are related to distinct events, separated in time by thermal relaxation of the subcontinental mantle lithosphere. Several suites of spinel peridotite xenoliths compositionally comparable to the Lherz peridotites (i.e., formed of LREE-depleted lherzolites associated with subordinate, LREE-enriched harzburgites) might also record magmatic refertilization of a previously depleted lithospheric mantle.

  Lherz Massif (Pyrenees, France) is an ideal location to study interactions between percolation and deformation in mantle rocks. It is composed of refertilized spinel lherzolites containing frequent cmscale websteritic layers that surround metric to decametric-scale bodies of depleted harzburgite in the southern part of the massif. Detailed structural mapping and geochemical analysis show that the lherzolites formed at the expense of of basaltic melts deeply modified the structure and the composition of the

Fig. 1 :

 1 Fig. 1: (a) Localization and geological context of the Lherz Massif[START_REF] Azambre | Les écailles de gneiss du faciès granulite du Port de Saleix et de la région de Lherz (Ariège). Nouveaux témoins du socle profond des Pyrénées[END_REF][START_REF] Kornprobst | Transcurrent crustal thinning: a mechanism for the uplift of deep continental crust/upper mantle associations[END_REF][START_REF] Monchoux | Les lherzolites pyrénéennes: contribution à l'étude de leur minéralogie, de leur genèse et de leurs transformations[END_REF][START_REF] Vielzeuf | Pétrologie des écailles granulitiques de la région de Lherz (Ariège-Zone Nord Pyrénéenne). Introduction à l'étude expérimentale de l'association grenat(alm-py)feldspath potassique[END_REF]. 1-Schists; 2-Mesozoic and Cenozoic rocks; 3-Granulites; 4-Metamorphic Mesozoic rocks; 5-Peridotites; 6-Granulite occurrences; 7-Hercynian basement; 8-Late Tertiary sediments. (b) Geological map of the Lherz Massif (Le Roux et al., 2007) with the location of analyzed samples.

. 1 -

 1 Fig. 1: (a) Localization and geological context of the Lherz Massif[START_REF] Azambre | Les écailles de gneiss du faciès granulite du Port de Saleix et de la région de Lherz (Ariège). Nouveaux témoins du socle profond des Pyrénées[END_REF][START_REF] Kornprobst | Transcurrent crustal thinning: a mechanism for the uplift of deep continental crust/upper mantle associations[END_REF][START_REF] Monchoux | Les lherzolites pyrénéennes: contribution à l'étude de leur minéralogie, de leur genèse et de leurs transformations[END_REF][START_REF] Vielzeuf | Pétrologie des écailles granulitiques de la région de Lherz (Ariège-Zone Nord Pyrénéenne). Introduction à l'étude expérimentale de l'association grenat(alm-py)feldspath potassique[END_REF]. 1-Schists; 2-Mesozoic and Cenozoic rocks; 3-Granulites; 4-Metamorphic Mesozoic rocks; 5-Peridotites; 6-Granulite occurrences; 7-Hercynian basement; 8-Late Tertiary sediments. (b) Geological map of the Lherz Massif (Le Roux et al., 2007) with the location of analyzed samples.

  spinel lherzolites. Exhumation of Pyrenean peridotites is usually ascribed to lithospheric thinning associated with successive opening and closing of elongated, asymmetrical pull-apart basins in response to the dominantly transcurrent motion of the Iberian plate relative to the European plate in the mid-

Fig. 2 : 38 Fig. 3 :

 2383 Fig. 2: Photographs of (a) fertile pockets in harzburgites; (b) a contact between harzburgite and lherzolite underlined by a thin websteritic layering. The foliations of harzburgites and lherzolites and the direction of the websteritic layering measured on the field are reported on the photograph as dashed lines; (c), (d) pervasive websteritic layering in distal lherzolites.

  to 5 mm long) are usually elongated; aspect ratios may attain up to 1:4. They display curvilinear grain boundaries, wavy extinction, and closely-spaced (100) subgrain boundaries. Orthopyroxenes and rare clinopyroxenes are smaller (2-3 mm and < 1 mm on average, respectively) and show irregular shapes and wavy extinction.

Fig. 4 :

 4 Fig. 4: (a) Photomicrograph parallel to the foliation plane of a porphyroclastic harzburgite showing a orthopyroxene-clinopyroxene-spinel rich websteritic lens with a coarse granular texture. Detail photomicrographs of the lens showing (b) irregularly-shaped interstitial spinels (Spl) and (c) a strongly deformed orthopyroxene (Opx) with en-echelon fractures normal to the kink bands filled with clinopyroxene.

  Crystal-preferred orientations (CPO) of olivine, orthopyroxene and clinopyroxene were measured by indexing of Electron Back Scattered Diffraction (EBSD) patterns using the SEM-EBSD system at Geosciences Montpellier (France). Indexing was performed either manually or automatically. Manual measurements consisted of grain-bygrain indexing along 2 mm-spacing profiles parallel to the long axis of the thin section. For each thin section, except in the websterites, ≥ 200 olivine grains were indexed to obtain a statistically representative sampling of the CPO (Ben Ismaïl and Mainprice, 1998). The automatic mapping used a regular grid step of 85µm, which is in average 10-11 times smaller than the largest observed grains, over the whole thin section. Raw maps are characterized by 50-60% indexed surface. Non-indexed pixels are linked to serpentinization, polishing defects, grain boundaries and non-indexed minor phases like spinels. Post-acquisition data treatment allowed to further increase the

Fig. 5 :

 5 Fig. 5: (a) Olivine crystal-preferred orientations (CPO) in distal harzburgites (>15 m from the contact). (b) Olivine crystal-preferred orientations (CPO) in distal lherzolites (>30m from the contact). Lower hemisphere equal area projections in the geographic reference frame (N at the top, E on the right). Contours at 0.5 of multiple of a uniform distribution intervals. 1 measurement per grain. N= Number of grains measured. Empty stars and solid lines indicate the projection of the apparent lineation and foliation, respectively.

Fig. 6 :

 6 Fig. 6: Evolution of olivine crystal-preferred orientations (CPO) across two harzburgite-lherzolite contacts. Lower hemisphere equal area projections in the geographic reference frame (N at the top, E on the right). Contours at 0.5 of multiple of an uniform distribution intervals. 1 measurement per grain. N= Number of grains measured. Empty stars and solid lines indicate the projection of the apparent lineation and foliation, respectively.

3. 2 .

 2 Weakening of CPO associated with the refertilization process Harzburgites display a clear [100]-fiber olivine CPO throughout the massif (Figs. 5a, 6 & 7). This olivine CPO pattern is characterized by alignment of [100] axes close to the lineation and a girdle distribution of [010] and [001] with a maximum of [010] normal to the foliation. It is typical of deformation by dislocation creep with activation of the high temperature, low stress (0kl)[100] slip systems, with (010) as the dominant slip plane (Tommasi et al., 2000).

Fig. 7 :

 7 Fig. 7: Evolution of olivine CPO as function of the distance to the harzburgite-lherzolite contacts. (a) CPO strength, represented by the J index. (b), (c), and (d) Maximum density of distribution of [100], [010], and [001] axes of olivine, respectively. (e) Ratio of maximum density of distribution of [100] axes relative to the one of [010] axes. This plot highlights the transition from strong [100]-fiber patterns in harzburgites to ([010]-fiber patterns in lherzolites close to the contact, and finally to weak [100]-fiber patterns in lherzolites far from the contact. Empty squares: harzburgites; solid circles: lherzolites; grey triangles: websterites. Dotted lines outline the general evolution of the olivine CPO from the harzburgites to the lherzolites far from the contacts.

Table 1 :

 1 Modal composition and olivine CPO pattern and intensity (J index) of the studied samples, according to their distance to the nearest harzburgite-lherzolite contact. The localization of the samples is given in Fig. 1; Ol = olivine, Opx = orthopyroxene, Cpx = clinopyroxene, Spl = spinel. Modal compositions were calculated by inversion of whole-rock chemical compositions based on mineral compositions obtained by microprobe analysis (Le Roux et al., 2007). harzburgites display strong [001]-fiber patterns (Fig. 8a), characterized by alignment of [001] axes close to the lineation and a weaker concentration of [100] axes normal to the foliation (Fig. 8a). This CPO is typical of high-temperature deformation of orthopyroxene with dominant activation of the (100)[001] slip system. The correlation between olivine and orthopyroxene CPO, marked by parallelism of the dominant high-temperature Burgers vectors [100] and [001]respectively, suggests a coherent deformation of these two mineral phases.

Fig. 8 :

 8 Fig. 8: (a) Representative crystal-preferred orientations (CPO) of olivine, enstatite and diopside in harzburgites (H.), proximal lherzolites (P.L.) and distal lherzolites (D.L.). Lower hemisphere equal area projections in the geographic reference frame (N at the top, E on the right). Contours at 0.5 of multiple of a uniform distribution intervals. 1 measurement per grain. N= Number of grains measured. Empty stars and solid lines indicate the projection of the average lineation and foliation of representative samples. (b) Shape-and crystal-preferred orientations (CPO) of olivine (Ol, white), orthopyroxene (Opx, light gray) and clinopyroxene (Cpx, dark gray) measured by crystal orientation mapping with a 85µm grid step in two 'abnormal' distal lherzolites. Empty stars and solid lines indicate the projection of the apparent lineation and foliation respectively. The lineation, marked by the elongation of olivine crystals, is not parallel to the maximum concentration of [100] axes of olivine, but it is parallel to the maximum concentration of [001] axes of pyroxenes. (c) Crystal-preferred orientations (CPO) of olivine, enstatite and diopside in cm-scale websterite layers within lherzolites. Dotted lines represent the orientation of the websteritic layer.

  dominantly display [100]-fiber olivine CPO patterns (Figs. 5b & 7). [100] axes of olivine are aligned close to the lineation, whereas [010] and [001] display a girdle distribution with a maximum of [010] normal to the foliation. This crystallographic fabric is consistent with activation of (0kl)[100] slip systems with dominant slip on (010) planes. Some distal lherzolites display [010]-fiber olivine CPO, similar to those observed close to the harzburgite bodies (Figs. 5b & 7).

  In the Lherz massif, lherzolites formed through a refertilization process involving interaction of refractory mantle lithosphere (harzburgites) with upwelling asthenospheric melts(Le Roux et al., 2007). Detailed structural mapping shows that the orientation of the foliation and the lineation in harzburgites is consistent at the scale of the massif even though many harzburgites are small, isolated bodies enclosed in the lherzolites. On the other hand, the direction of the foliation and lineation in lherzolites varies throughout the massif. The lherzolites steeply-dipping foliation locally moulds the harzburgite bodies and often crosscuts their steady shallowly-dipping foliation. In addition, within the lherzolites, an increase in the deformation away from the contact with harzburgites is suggested by the progressive development of a shapepreferred orientation of olivine crystals and a better alignment of spinels, which results in an evolution in the field from an incipient to a well-developed foliation with increasing distance to the contacts. Stronger deformation in the distal lherzolites is also suggested by boudinage and folding of the websteritic layering that are not observed close to the contacts. These observations support that the harzburgites preserve structures related to an episode of deformation prior to the formation of the lherzolites, and that subsequent deformation was localized in the lherzolites. The important change in the deformation kinematics, characterized by sub-horizontal foliations in harzburgites to steeply-dipping foliations in lherzolites, suggests two distinct deformation episodes rather than a continuum. In the following paragraphs we discuss the relations between melt percolation and deformation that vary throughout the massif, from the harzburgites to the distal lherzolites. The numerous cm-scale websteritic lenses in the harzburgites (Fig. 2a) were probably formed by partial crystallization of small volumes of melt injected in the harzburgite. Coexistence of strongly deformed orthopyroxene crystals showing wavy extinction, kink bands, local 'en echelon' fractures and moderately to undeformed clinopyroxenes and undeformed spinels (Fig. 4) suggests syn-kinematic crystallization where strain rate progressively decreased with increasing Chapter III Le Roux et al. (2008), Feedback between melt percolation and deformation in an exhumed lithosphere-asthenosphere boundary 49 crystal fraction. Fractures normal to kink bands in large deformed orthopyroxene crystals filled by small undeformed clinopyroxene crystals (Fig. 4c) may have resulted from crystal-scale hydraulic fracturing in the harzburgites caused by local overpressure due to the presence of melts. Far from the harzburgite-lherzolite contacts, these websteritic lenses are systematically parallel to the harzburgites foliation. In contrast, close to the contacts, they are larger and more numerous and they are often oblique to the harzburgite foliation and parallel to the contact. Because of their minerals composition similar to those of the host matrix, it seems difficult to chemically discriminate whether these pockets are linked or not to the refertilization event. Although a possible formation of these websteritic lenses during an older melt percolation event cannot be ruled out, we favor, based on our structural observations, the hypothesis that they represent the early stage of the melt percolation event that formed the lherzolites. In this scenario, the foliation-parallel websterite lenses represent the initial stages of melt percolation that were accompanied by an incipient deformation of the harzburgites. Alignment of the melt lenses in the foliation implies that the percolation of these small melt volumes was guided by the preexistent anisotropic structure of the harzburgites (Tommasi et al., 2008; Waff and Faul, 1992). The strong olivine CPO in the harzburgites resulted in a mechanical anisotropy (Tommasi and Vauchez, 2001) that probably also controlled the incipient stages of deformation. Close to the contact with lherzolites, the structural control by the harzburgite foliation was probably overwhelmed by the external solicitation (imposed kinematics), which is better expressed in lherzolites. Finally, coexistence of deformed and undeformed minerals in these lenses suggests that partial crystallization and refertilization reactions in the melt pockets led to a stop of the deformation and transfer of strain to domains with a larger proportion of melt and hence a lower dynamic viscosity. With increasing distance to the contacts with harzburgites, lherzolites display an evolution of macroscopic structures and crystal preferred orientations that may be explained by variations in finite strain and in the melt fraction present during deformation. The tectonic fabric of the lherzolites strengthens with increasing distance to the contact. Within 1m from contact, the lherzolites show an incipient foliation marked by the alignment of interstitial spinels and a cm-scale websterite banding, but their olivine CPO is still parallel to the harzburgite one. This suggests that, in this narrow contact zone, strain was not high enough to erase the crystallographic fabric inherited from harzburgites. Within 30m from the contacts, proximal lherzolites show Chapter III Le Roux et al. (2008), Feedback between melt percolation and deformation in an exhumed lithosphere-asthenosphere boundary 50 a weak but clearly developed foliation and lineation, to which is associated a weak olivine CPO with a dominant [010]-fiber pattern, characterized by a point maximum of [010] normal to the foliation and dispersion of [100] in the foliation plane. [010]-fiber olivine patterns similar to those observed in the proximal lherzolites have been observed in peridotites worldwide, for instance in the Ronda massif (Vauchez and Garrido, 2001), in alkali-basalt xenoliths from Siberia (Tommasi et al., 2008), in cratonic xenoliths (Ben Ismaïl and

52 Fig. 9 :

 529 Fig.9: Sketch summarizing the evolution of microstructures and olivine CPO in harzburgites and lherzolites from the Lherz massif according to their distance to the harzburgite-lherzolite contacts.

  pyroxenes and spinel crystallization during refertilization reactions resulted in a reduction of porosity, plugging the melt network and hence favoring the segregation of melts. The coexistence of cm-scale strongly deformed orthopyroxenes and moderately to undeformed clinopyroxenes suggests that the deformation slowed progressively as the newly-formed crystals plugged the porosity, likely localizing further in less crystallized domains. The websteritic layers in the Lherz massif thus probably represent multiple "frozen" timesteps of a dynamic melt transport system.

4. 3 .

 3 Geodynamic environment of the refertilization processIn this paper we suggest that the refertilization of the old harzburgitic mantle lithosphere was coeval with a deformation dominated by simple shear under subsolidus temperature conditions. During the evolution of the Pyrenean domain, two major events have tightly associated magmatism and deformation: 1) the Cretaceous deformation and 2) the Hercynian orogeny. The emplacement of the Lherz massif in the crust during the Cretaceous[START_REF] Henry | Late mantle evolution of the Pyrenean sub-continental lithospheric mantle in the light of new 40 Ar-39 Ar and Sm-Nd ages on pyroxenites and peridotites (Pyrenees, France)[END_REF] might have produced such a deformation.Howeveramphibole-pyroxenite dykes considered to represent trans-lithospheric melt conduits for Cretaceous alkaline magmatism(Bodinier et al., 1987a;[START_REF] Golberg | Petrological and age relationship between emplacement of magmatic breccia, alkaline magmatism and static metamorphism in the North Pyrenean Zone[END_REF][START_REF] Loubet | Trace elements in orogenic lherzolites reveal the complex history of the upper mantle[END_REF][START_REF] Vétil | Conditions de mise en place des filons des pyroxénites à amphibole du massif ultramafique de Lherz (Ariège, France)[END_REF] crosscut at high angle the foliations of both the harzburgites and refertilized lherzolites, suggesting that the refertilization event occurred before the Cretaceous. Moreover Pyrenean peridotites record equilibrium conditions of 8-17 kb at ~950°C suggesting an isobaric cooling stage from ~1200°C to ~900°C during a ~20My

  to suggest that the retrieved S-wave polarization anisotropy is largely inherited from the deformation of the mantle lithosphere during the Hercynian orogeny. Indeed, shear-wave splitting measurements yield a consistent ~N100E polarization of the fast S-wave and rather large splitting, suggesting a lithospheric fabric mostly due to transcurrent motions. This anisotropy is observed in all domains of the Pyrenean belt, even in the southern and northern external domains where the ECORS seismic profile has shown that only the uppermost crust was involved in the Pyrenean tectonics

  orogeny in the Pyrenees are characterized by emplacement of syncinematic granites at the scale of the belt. Based on the analysis of the magmatic flow fabric of these granites and of the tectonic fabric in the host rocks, Gleizes et al. (1997) suggested that the whole Pyrenean belt behaved as a large, lithospheric-scale "shear-zone" during the last stage of the Variscan orogeny. We suggest therefore that the Variscan event may represent an adequate context for the syn-orogenic refertilization episode of an older lithosphere, remnants of which have been preserved in Lherz massif. melt fractions favored strain localization and larger strain favored Chapter III Le Roux et al. (2008), Feedback between melt percolation and deformation in an exhumed lithosphere-asthenosphere boundary 55 melt percolation through a higher dynamic porosity. This feedback is probably a major process in the compositional and structural rejuvenation of the subcontinental mantle lithosphere. (c) The response of the rocks' texture to deformation depends on a subtle balance between two parameters: the strain intensity and the volume of percolating melts. In the Lherz massif, this led to coexistence of [100]-fiber and [010]-fiber olivine CPO. [100]-fiber olivine CPO developed where strain dominated the evolution (very low melt fractions as in the harzburgites or high strain as in the distal lherzolites). On the other hand, [010]-fiber olivine CPO developed where melt played an equally important or dominant part in the evolution (low melt fraction and incipient strain in proximal lherzolites or large melt fractions in the websterites). (e) The formation of the websterites layers was synchronous of that of the lherzolites, due to melt segregation that was probably favored by the refertilization reactions, which plugged the melt network, reducing the permeability and producing small-scale pressure gradients. (e) The deformation-refertilization event observed in the Lherz massif probably records the evolution of the Pyrenean mantle lithosphere during the late stage of the Variscan orogeny during the Carboniferous, when abundant magmatism coeval with orogen-parallel transcurrent faulting was emplaced throughout the Pyrenean domain. This shearing produced a large-scale anisotropic structure in the mantle lithosphere, which may explain the beltparallel polarization of the fast split shear wave observed in the Pyrenees.

  than first envisioned. For instance,[START_REF] Sneeringer | Strontium and samarium diffusion in diopside[END_REF] obtained a diffusion rate of ~5.10 -15 cm 2 .s -1 for Sm in diopside at 1250°C and 1.4 Gpa whileVan Orman et al. (2001) showed that Yb, one of the fastest REE, did not diffuse faster than 5-6.10 -16 cm2.s -1 at the same pressuretemperature conditions. The high mantle temperature and the relatively slow rate of mantle melting may not guarantee isotopic equilibrium between the solid residue and the extracted molten fractions when the mantle source is isotopically heterogeneous. Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: , the massif offers a unique opportunity to trace Hf, Nd and Sr isotopic variations related to melt transport. We used a one-dimensional percolation-diffusion model (Vasseur et al., 1991) modified to include isotopic homogenization and a percolation-reaction model (Vernières et al., 1997) to assess the effects of mineralogical reactions on isotopic variations. We show that transient, decoupled, isotopic signatures may develop in a melt percolation front. These signatures are highly sensitive to parameters such as daughter-element concentrations in peridotite and melt, element diffusivity, mineral grain size and efficiency of isotopic reequilibration. The variations observed in the Lherz peridotites are more readily governed by diffusional peridotite-melt disequilibrium than by the chromatographic effect of melt transport and the refertilization reaction.

Fig. 1 :

 1 Fig. 1: (a) Distribution of the Pyrenean peridotite bodies along the North Pyrenean Fault (NPF), from Lagabrielle and Bodinier (2008) after Choukroune (1978). 1: Oligocene and post-Oligocene sediments; 2: Mesozoic and Eocene sediments; 3: Paleozoic basement; 4: area of LP-HT Pyrenean metamorphism; 5: lherzolite bodies; 6: granulites; 7: main thrusts external zones; 8: North Pyrenean Fault. (b) Harzburgites and lherzolites intermingling in the Lherz massif (Le Roux et al., 2007); the location of the sampling sites are indicated on the map, 1: distal lherzolite; 2: profile through a contact; 3: distal harzburgites. (c) Detailed sampling site 2 through a harzburgite-lherzolite contact.

  and Sr isotopes analyses, including samples dissolution, chemical separation and measurements were carried Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: corrected for W and Ta, and Lu and Yb interferences at masses 180 and 176, respectively, by monitoring the isotopes 182 W, 181 Ta, 175 Lu, and 173 Yb, and normalized for mass fractionation to 179 Hf/ 177 Hf of 0.7325 using an exponential law. In order to asses the daily performance of the MC-ICP-MS, JMC475 (≈50 ppb) and JMC321 (≈50 ppb) were used as internal standards for Hf and Nd respectively and yield ( 176 Hf/ 177 Hf ) JMC475 = 0.282173 ± 15 (2SD; n= 18; typical internal precision is c.a 3.10 -6 ) and ( 143 Nd/ 144 Nd) JMC321 = 0.511008 ± 20 (2SD; n= 5; typical internal precision is c.a 5.10 -6 ). Four standards BHVO-2 gave a 176 Hf/ 177 Hf of 0.283107 ± 20 (2SD; typical internal precision is c.a 8.10 -6 ) and 143 Nd/ 144 Nd of 0.512961 ± 9 (2SD; typical internal precision is c.a.6.10 -6 ). These values are well within the accepted-published values[START_REF] Barrat | Geochemistry of the Tertiary volcanism of Northern Ireland[END_REF][START_REF] Blichert-Toft | The Lu-Hf isotope geochemistry of chondrites and the evolution of the mantle-crust system[END_REF][START_REF] Weis | High-precision Pb-Sr-Nd-Hf isotopic characterization of USGS BHVO-1 and BHVO-2 reference materials[END_REF]).Procedural blanks were as follow:[Sr] blank = 139±61 pg (n=2); [Nd] blank = 26 pg (n=1);

Table 1 :

 1 87 Sr/ 86 Sr, 143 Nd/ 144 Nd and 176 Hf/ 177 Hf isotopic ratios in the 16 clinopyroxenes separates from a harzburgite-lherzolite transition zone in the Lherz massif as well as in distal samples (06LI15: harzburgitic protolith; 06LI17 distal lherzolite), obtained by TIMS and MC-ICP-MS techniques at the GEMOC ARC National Key Centre (Australia). The associated 87 Rb/ 86 Sr, 147 Sm/ 144 Nd and 176 Lu/ 177 Hf were calculated from Rb, Sr, Sm, Nd, Lu and Hf concentrations in clinopyroxenes obtained by LA-ICPMS. dist. (m) is the distance to the contact between harzburgites and lherzolites. Meaningless T CHUR model ages have not been reported. * denotes that Nd isotopes ratios obtained by TIMS. BHVO-2 values are from Weis et al. (2005), JMC475 values are from Blichert-Toft and Albarede, (1997) and JMC321 values are from Barrat and Nesbitt (1996). The clinopyroxene REE compositions (ppm) in harzburgites and lherzolites are from the transition zone and the distal (>15m from a contact) peridotites. Errors are twice the standard deviations. At least 5 clinopyroxenes have been lasered in each thin section, and all individual clinopyroxenes have been lasered twice. Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: a caseand/or Medium REE (MREE) with La N up to 29 and (La/Sm) N ~3.6 (Fig. 2). These patterns are similar to the representative REE patterns at the massifscale obtained on more than 50 samples in Le Roux et al. (2007). Thus the harzburgitelherzolite contact sampled for this study can be considered as a representative transition zone between harzburgites and lherzolites.

Fig. 2 :Fig. 3 :

 23 Fig.2: Chondrite-normalized[START_REF] Sun | Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes[END_REF] clinopyroxenes REE patterns in the sixteen peridotites analyzed in this study, including distal harzburgites and lherzolites (> 15m from the contact), and samples adjacent to the contact ('proximal').

  Harzburgites and lherzolites from the transition zone differ markedly from the distal ones with respect to their isotopic signatures. Their compositions plot close to the field of intraplate basalts (Ocean-Island Basalts and HIMU) and a simple mixing between the two poles defined by the distal Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: a casestudy in the Lherz peridotite 67 peridotites particularly fail to account for

  melt strictly confined to the sharp and convoluted contact between harzburgites and lherzolites, which is very unlikely according to chemical and structural constraints. A more likely alternative is that these isotopic signatures formed at the melt percolation front through a particular Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: a casestudy in the Lherz peridotite 68 chemical/physical process that led to the decoupling of Hf from Nd and Sr.

  model incorporates the effects of chemical diffusion, critical distance of isotopic homogenization, melt velocity, height of the percolating column and grain size. It assumes instantaneous solid-liquid equilibrium at the surface of mineral grains, considered to be spherical, and chemical diffusion within the grains, from surface to core. Isotopic equilibrium between fluid and solid phases is governed by the mass-balance equation of isotopic homogenization at the scale of critical volumes. The critical volume of isotopic homogenization is defined as the volume of percolated peridotite in which melt and matrix have reached isotopic equilibrium during the critical time of percolation (i.e., the times it takes for the melt to reach the top of the column). In addition, a percolation-reaction model (the "plate model" of Vernières et al., 1997) has also been used to evaluate the effects of the volumes by selfdiffusion, which is effective even in the lack of chemical potential gradient (e.g. when the percolating melt and the peridotite have reached chemical equilibrium); (d) chemical reaction between the rock and the infiltrating melt that changes the mineralogical composition of the rock and/or the melt fraction. A detailed parameterization was carried out to assess the influence of the main percolation-diffusion model parameters on the covariation of Hf, Nd and Sr isotopic compositions in a harzburgite column percolated by a melt in equilibrium with the Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: a casestudy in the Lherz peridotite 69 distal lherzolites. The parameters used for modeling are compiled in

1250°C and 1 . 5 5 . 3 .

 1553 Gpa from the experimental data ofVan Orman et al. (2001), the diffusion rate of Nd was fixed at 3.4*10 - 17 cm².s -1 . The diffusivity of Hf was estimated from its ionic radius and charge, yielding a diffusion rate of 1.2*10 -17 cm².s -1 . The chemical diffusivity of Sr is somewhat controversial. While the study of[START_REF] Sneeringer | Strontium and samarium diffusion in diopside[END_REF] indicates that this element has a faster diffusivity in clinopyroxene, compared with REE, the recent study of Von der Handt (2008) on orthopyroxene suggests that the diffusion of Sr is actually slower than that of REE, in both clino-and orthopyroxene. For this reason, we fixed the diffusivity of Sr identical to that of Nd. To assess the effect of chemical diffusivities variations, we run experiments involving variations of this parameter in the range 0.1 to 30 times the d values. The observed range of pyroxenes grains sizes in Lherz varies from 1 to 4mm (Le Roux et al. 2008), except in small-scale mylonitic zones (<1mm). In the models, mineral grain size varies from 0.1 mm to 5 mm. This represents the average diameter of the grains, considered to be spherical. For simplicity, olivines and pyroxenes were considered to have the same size for modeling. The Hf, Nd and Sr contents in the protolith (based on the composition of the most depleted sample) are ~ 0.003, 0.015 and 1 ppm, respectively, and the Hf, Nd and Sr contents in the infiltrated melt (based on equilibrium with clinopyroxenes from distal, refertilized lherzolites) are ~ 2.45, 10.7 and 743 ppm, respectively. To evaluate the effect of the compositional contrast between meltTable 2: Fixed and variable modeling parameters used in the one-dimensional model of Vasseur et al. (1991). Ol = olivine; Opx = orthopyroxene; Cpx = clinopyroxene; Spl = spinel. CDIH is the critical distance of isotopic homogenization. and matrix, we run a series of experiments with a realistic range of daughter element variations in the harzburgites. Hf melt /Hf matrix ratios vary from 817 to 305, assuming constant Hf melt and Nd melt /Nd matrix , and Nd melt /Nd matrix ratios vary from 475 to 1420, assuming constant Nd melt and Sr melt /Sr matrix . The critical distance of isotopic homogenization along the column ranges between 0.1 and 10m. The parameters used in the percolationreaction model of Vernières et al. (1997), such as porosity, isotopic ratios and elements concentrations, are the same as for the onedimensional model. The melt-rock reaction was taken from Le Roux et al. (2007). It is a pyroxene-forming reaction at decreasing melt mass also involving some degree of olivine dissolution. Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: a casestudy in the Lherz peridotite 71 Results of the modeling Representative results of the percolationdiffusion modeling are illustrated on figures 4 and 5. These figures show the isotopic covariations of Hf-Nd (Fig. 4) and Nd-Sr (Fig. 5) along the percolation column, from the composition of the harzburgite protolith (atop the column) to that of the melt (at base of the column). Both Hf-Nd and Nd-Sr covariations define curved trajectories that may be either convex upward, lying above the mixing lines, or convex downward, lying below the mixing lines. These variations imply significant inter-isotopic decoupling, notably for the Hf-Nd pair.

Fig. 4 :

 4 Fig. 4: 176 Hf/ 177 Hf versus 143 Nd/ 144 Nd in clinopyroxene separates from Lherz harzburgites (open squares) and lherzolites (solid circles), compared with the mixing curve (dotted line) between a harzburgite protolith and a MORB-type melt, and with the results of the one-dimensional percolation-diffusion modeling (solid lines). The diagrams (a) to (d) illustrate the effects of varying parameters in the model: (a) diffusivity, d, of the elements in minerals; (b) the mineral grain size; (c) the Hf melt /Hf matrix ratio; (d) the critical distance of isotopic homogenization along the column. Heavy lines represent a 'best fit' of the Lherz data.

  However, our experiments also show convex-downward Hf-Nd covariation trends that are opposite to the variation predicted by the chromatographic theory. At a given Hf melt /Hf matrix value, they are systematically observed in experiments involving relatively slow element diffusivities in minerals (Fig.4a) and/or coarse grain sizes (Fig.4b), i.e., when the critical time of solid-liquid equilibrium tends to be significant compared to the critical time of percolation (104 years in all our experiments). This type of Hf-Nd decoupling does not result from the difference in diffusivity between Hf and Nd as Hf diffuses at a slower rate than Nd. The convex-downward Hf-Nd trends reflect the persistence of solid-liquid chemical disequilibrium in significant parts of the percolation column -notably the uppermost part -where the percolating melt and the matrix partly preserve their original compositions. In these conditions, the chromatographic fractionation process is overwhelmed by the compositional effect of Hf and Nd concentrations in the protolith and disequilibrium melt. This effect results from the dependence of the bulk (solid + melt) isotopic values calculated with the isotopic mixing equation at the scale of critical homogenization volumes on daughter element concentrations in minerals and melt. For a given set of parameters consistent with the chromatography theory, the convexupward Hf-Nd isotopic trends are observed in experiments involving relatively low concentration of Hf in melt relative to the matrix (Hf melt /Hf matrix < 443 for the experiments shown on figure 4c). However, Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: a casestudy in the Lherz peridotite 73 a subtle increase of the Hf concentration in the melt relative to the matrix (Hf melt /Hf matrix = 443 to 817, i.e. Hf matrix = 0.008 to 0.003 on figure 4c) is sufficient to generate a change from convex-upward to convexdownward Hf-Nd isotopic covariation trends. Finally, the amplitude of the transient Hf-Nd isotopic decoupling along the percolation column is negatively correlated with the efficiency of the isotopic homogenization process. Spatially limited homogenization (i.e., short critical distance of isotopic homogenization along the column) yields strongly convex Hf-Nd covariation curves, either upwards or downwards depending on the other model parameters (e.g., Fig. 4d).

Fig. 5 :

 5 Fig. 5: 143 Nd/ 144 Nd versus 87 Sr/ 86 Sr in clinopyroxene separates from Lherz harzburgites (open squares) and lherzolites (solid circles), compared with the mixing curve (dotted line) between a harzburgite protolith and a MORB-type melt, and with the results of the one-dimensional percolation-diffusion modeling (solid lines). The diagrams (a) to (d) illustrate the effects of varying parameters in the model: (a) diffusivities, d, of the elements in minerals; (b) the mineral grain size; (c) the Nd melt /Nd matrix ratio; (d) the critical distance of isotopic homogenization along the column.

Fig. 6 :

 6 Fig. 6: Results of percolation-reaction modeling (Vernières et al., 1997) for the Hf-Nd isotopes in the Lherz peridotites. Symbols are the same than in previous figures.

  between harzburgites and lherzolites in the Lherz massif can be reproduced with a realistic range of physical parameters: a melt fraction of a few percent, a percolation rate of several cm.y -1 , a distance of percolation from tens to several hundreds of meters associated with a volume of homogenization on the scale of the sample (some tens of cm). The Lherz example suggests that a large range of isotopic signatures may be generated at a melt percolation front, depending on chemical diffusion, isotopic homogenization and peridotite-melt compositions. We also show that mineralogical reactions at decreasing melt-mass enhance chromatographic effects by decreasing the porosity. The variations observed in the Lherz peridotites are more readily governed by diffusional peridotitemelt disequilibrium than by the chromatographic effect of melt transport and the refertilization reaction. The development of these signatures is a transient phenomenon associated with the passage of a percolation front which has been "frozen in" in the Lherz massif. Moreover, we observe that the microstructural characteristics (e.g. the grain size) of the percolated protolith strongly influence the resulting isotopic signature within the percolation front. Thus deformation and recrystallization of mantle Chapter IV Le Roux et al. (2008), Isotopic decoupling during porous melt flow: a casestudy in the Lherz peridotite 76 rocks may induce local variations in isotopic signatures, as observed in the Ronda massif

I1

  have crushed, sieved and passed rocks fractions through magnetic separator. I have made a careful handpicking to get the clinopyroxene separates I used for isotopic data (16 samples of >100mg pure clinopyroxene fractions). I have performed the chemical separation of Hf, Nd and Sr (clinopyroxene separates and corresponding whole-rocks) in the clean lab of GEMOC ARC National Key Centre with the help of Peter Wieland and I have performed the TIMS and MC-ICPMS measurements. This work was supported by INSU DYETI Program and ARC LIEF, DEST Systemic Infrastructure Grants, Macquarie University and industry, and by ARC Discovery project grants. I have obtained financial help from the French Ministry of Research and a 6 months 'Bourse Lavoisier Co-tutelle' scholarship for the collaboration with Australia. Mantle refertilisation, osmium isotopes and the "Primitive Upper Mantle" fallacy, Consequences for the nature of the late veneer Article in preparation. O. Alard 1,2 , V. Le Roux 1,2 , J.-P. Lorand 3 , J.-L. Bodinier 1 , W. L. Griffin 2 , , S. Y. O'Reilly 2 Géosciences Montpellier, Université de Montpellier 2 and CNRS, Cc 060, Place E. Bataillon, 34095 Montpellier cedex 5 France 2 GEMOC, Department of Earth & Planetary Sciences, Macquarie University NSW 2109 AUSTRALIA 3 Unité de Recherche "Minéralogie", Muséum National d'Histoire Naturelle de Paris, UMR7160 CNRS, Paris 75005, France. VLR's contribution in this paper: data and writing. A recurrent question in planetary sciences is: what were the "building blocks" of our planet? Of foremost interest is the nature of the `late veneer'; this late accretion (0.2-0.8% of Earth's mass) is seen by many as the carrier of water and possibly the seeds of life for Earth 1 . However, the nature of this late component remains elusive and constraints from various geochemical systems seem at first glance contradictory 2 . The highly siderophile elements (HSE: Os, Ir, Ru, Rh, Pt, Pd, Au and Re) have been seen as one of the most promising first-order constraints on the nature of the late component. The broadly chondritic relative abundances of HSEs in Earth's mantle are assumed to reflect the addition of chondritic material to the mantle after core formation via an intense meteorite bombardment 3,4 . Re and Os are both HSEs, 187 Re decays by beta emission to 187 Os, with a half-life of 41.6 Ga 5 , and the 187 Os/ 188 Os of Earth's Primitive Upper Mantle (PUM) reflects its timeintegrated Re/Os. The currently accepted 187 Os/ 188 Os value for the PUM, .0006) as the source of the "late veneer" and would suggest that ordinary chondrites 8 ( 187 Os/ 188 Os OC = 0.1283 ± 0.0017) formed the bulk of this veneer. the Earth was made of an unsampled type of material, the "Earthchondrite" or "Earth achondrite". Recently, the Pd/Ir of the PUM has been estimated 10 at ca 2.02 ± 0.30, but no chondrite group shows such fractionated HSE abundances 11 . However, a key question is the robustness and significance of the estimated PUM composition. We show here that the estimate of the Os-isotope composition of the PUM is erroneous, because it is based on sample suites in which the HSE abundances and Os-isotope composition have been altered by metasomatic processes. In the light of these new data the Os-isotope composition of the silicate Earth can currently only be constrained at best to be broadly chondritic. Behind the PUM The PUM is the composition of a hypothetical upper mantle reservoir that has never experienced melt depletion or metasomatic enrichment (i.e. the silicate earth prior to crustal differentiation). True PUM almost certainly does not exist anywhere on Earth today. Thus, the PUM composition has been estimated using correlations between potential indicators of melt depletion such as Al 2 O 3 and 187 Os/ 188 Os (Figure 1) in samples of the sub-continental lithospheric mantle, including xenoliths (scavenged by alkali-basalt volcanoes) and orogenic peridotites (tectonically emplaced into the crust). The PUM estimate relies mainly on two key assumptions: (i) due to the highly refractory nature of Os, the 187 Os/ 188 Os of a mantle section is "frozen in" during major melt extraction events and is not modified by percolation-reaction with ascending magmas; (ii) the least depleted (high-Al 2 O 3 ) peridotites represent samples from which no (or little) melt has been extracted. However, the validity and robustness of these two assumptions are highly questionable. The type Lherzolite under scrutiny The Lherz massif is the largest and bestexposed peridotite massif in the Pyrenées (France) and is the type locality of fertile mantle rock (i.e. Lherzolite). As such (and for historical reasons) Lherz has played a key role in the PUM estimate; it thus represents an ideal (and emblematic) place to investigate the true nature of the correlation between Al 2 O 3 and 187 Os/ 188 Os and to test the robustness of the PUM estimate. The Lherz massif shows several features inconsistent with the conventional meltextraction hypothesis, which regards

Fig. 1 :

 1 Fig. 1: Whole-rock major-element systematics (TiO 2 , Na 2 O vs Al 2 O 3 ) for the Pyrenées massifs. Open circles, Pyrenées peridotites 12 ; grey circles, Lherz samples (this study); black diamonds, interlayered spinel-websterites from all Pyrenées massifs. Solid bold curves show theoretical evolution of Al 2 O 3 , TiO2 and Na 2 O during partial melting 13 (tick marks every 10%). Dashed line denotes mixing between a refractory protolith (Al 2 O 3 = 0.45 ; TiO 2 =0.01 ; Na 2 O= 0.02 wt.%) and a basaltic melt (Al 2 O 3 = 15; TiO 2 = 0.6 ; Na 2 O= 1.45 wt.%); crosses show 5% mixing increments. Vertical lines denote the estimated Al 2 O 3 composition of a hypothetical Primitve Upper Mantle 6,7,10 (4.2±0.2 wt.%)

  have relatively low bulk partition coefficients (D≤0.1), will be more quickly depleted than less incompatible elements such as Al (D≈0.35±0.05) during partial melting, thus producing an upward-concave trend. In contrast, linear trends, such as those observed for the Lherz and the Pyrenées peridotites, are typical of mixing processes (Figure1). Thus, while Al 2 O 3 (or CaO, MgO, Lu…) are indices of fertility, they are not necessarily melt depletion indicators16,17 , as has been assumed for the calculations that led to the PUM6,7,10 estimate. While the positive correlation Al 2 O 3 -187 Os/ 188 Os has been ascribed to an old (Proterozoic) depletion event involving partial melting and stabilization of the lithospheric mantle18,19 , such a scenario cannot explain the negative and positive correlations of Al 2 O 3 with 87 Sr/ 86 Sr and 143 Nd/ 144 Nd, respectively12,20 .Thus, the (micro-and macro-) structural features suggest that all of the harzburgite bodies once formed a single continuous unit and that the deformation of the harzburgites predates the formation of the lherzolites and websterites.The petrographic and geochemical observations (e.g. Figure 1) are not consistent with a model in which the harzbugite represents the residue left after the extraction of partial melts from the fertile lherzolite. Instead, these features indicate that the lherzolite formed during refertilisation via a near-solidus reaction at the expense of the harzburgite protolith. This reaction caused the precipitation of pyroxenes ± spinel ± amphibole and sulphide. The pervasive websteritic layering in the refertilised lherzolites probably reflects melt segregation, or porosity waves in a matrix in which permeability was decreasing due to the pyroxene-producing refertilisation reaction 21 . Thus, ironically and in contrast to the canonical interpretation, the eponymous lherzolites of the Lherz massif are in fact re-fertilised harzburgites.

  Within this new framework, the relationships between refertilisation and the Os-isotope systematics of the Pyrenées massifs were investigated through the in-situ determination of the Re-Os composition of individual sulphide grains25 . First, we sampled at the meter scale in the Lherz massif (Figure1RM, 10 samples, 103

  lherzolites have S contents up to ≈300 ppm and show ≥20 large (50-600 µm) sulphide grains per section. All sulphides are interstitial and show polyhedral shapes with inward-convex grain boundaries and low dihedral angles (≤60º). In contrast to the peridotite xenoliths hosted by alkali basalts and kimberlites, no primitive sulphide inclusions (spherical shapes, mono-sulphide solid solution composition 27,35 ) in olivine have been found. All sulphides, irrespective of the peridotite type, consist of pentlandite (Pn: (Fe,Ni) 8 S 9 ) and minor chalcopyrite (Cp: CuFeS 2 ). The abundance of Cu-rich phases (Cp ± bornite) is higher (up to 20%) in sulphide-rich samples. Thus the sulphides of the Pyrenées lherzolites are not typical of residual mantle; instead, they have a metal (Ni,Cu)-rich composition typical of sulphide melts produced by partial melting of mantle sulphides 35,36 . The abundance of sulphide (up to 415 ppm of S) and the proportion of pyrrhotite (Po: Fe (1-x) S) increase in peridotite samples interlayed with websterite. Spinel-degree of fertility. Most lherzolite samples contain some sulphides with unradiogenic 187 Os/ 188 Os (< 0.115), low Re/Os and high Os contents, like those found in the harzburgites (Figure 4, RM table). This clearly indicates that all samples have undergone a major melting event during lower Proterozoic time (mean T RD = 2.2±0.2 Ga). This observation strongly supports the hypothesis that the protolith of the Lherz massif consisted of deformed old harzburgites 14 . The second sulphide endmember shows extremely radiogenic Os ( 187 Os/ 188 Os>>0.15), high Re/Os and low Os contents (<5 ppm). The increase in sulphide abundance in the lherzolite at the contact with pyroxenite and the continuous trend in whole-rock composition between peridotites and pyroxenites (Figure 2) support a genetic link between the refertilising agent (i.e. the radiogenic end-member) and the interlayered spinel-websterites. Spinel websterites (unpublished data) yield a poorly constrained (MSWD 6.6) Re-Os isochron age of 1.35±0.12 Ga and an initial Os-isotope composition of 0.118±0.004. This age is similar to that of the spinel-websterites in the

Fig. 4 :

 4 Fig. 4: Relative probability plot of 187 Os/ 188 Os in Pyrenées sulphides. Solid curve, sulphide 187 Os/ 188 Os composition in residual harzburgites (n=22,Table1repository material); dashed curve, sulphide 187 Os/ 188 Os for all Pyrenées lherzolites studied here (n=268; Table1). Histogram of whole-rock compositions10,18,19,42 . Right column shows the 187 Os/ 188 Os distribution in single whole-rock samples from the same outcrop, a few meters wide (Figure1, repository material). Technical limitations inherent to the in-situ technique25 mean that samples with high Re/Os ( 187 Re/ 188 Os>0.7) and/or low Os sulphides (<1ppm) suffer large errors, and the 187 Os/ 188 Os of sulphide having 187 Re/ 188 Os >1 cannot be determined. Consequently the sulphide population presented here is slightly biased toward sulphides with high Os contents and low Re/Os. Vertical solid and dashed lines denote the estimated 187 Os/ 188 Os composition and uncertainty (respectively) of a hypothetical Primitve Upper Mantle6,7,10 ; Shaded region indicates minimum 187 Os/ 188 Os deduced from whole-rock alumino-isochron18,19 .

  . The only primitive feature preserved in these rocks is probably the relict melt-depletion age carried by the residual sulphide population both the harzburgites and the lherzolites. Consequences for the "late veneer" and the composition of the upper mantle The fertile nature of the lherzolites from the Lherz massif -the type locality -is thus not related to small degrees of melting but rather to the referilisation of a refractory ancient mantle lithosphere through the reactive percolation of a MORB-like melt. This event was accompanied by the precipitation of sulphide, which has profoundly modified the Os-isotope composition and HSE abundances of the Lherz mantle. Thus, the commonly-used indices of fertility (e.g. Al 2 O 3 ), the HSE abundances (e.g. Pd/Ir, Re/Os) and the 187 Os/ 188 Os of the Pyrenées lherzolites are not pristine characteristics. The linear correlation between 187 Os/ 188 Os and Al 2 O 3 must be considered as a mixing line between an injected mafic component ("mantle botox") and an old (Archean-Proterozoic) refractory mantle. The intersections of these trends with a "primitive" Al 2 O 3 content therefore have no meaning in terms of the composition of the PUM.

Fig. 5 :

 5 Fig. 5: Nd and Os isotopic composition for the non-Archean lithospheric mantle. Black circles, alkalibasalt hosted peridotite xenoliths; empty triangles, orogenic peridotite massifs, for data source see repository material; dashed grey line shows the expected composition of variably depleted mantle, i.e. old and depleted mantle should have Nd >>0 and 187 Os/ 188 Os <<0.13 depending on the age and extent of melting; conversely pristine undepleted mantle should have Nd≈0 and 187 Os/ 188 Os near the PUM composition 6 (i.e. ≈ 0.1296±0.0008). Solid and dotted thin lines denote PUM estimate 6 ( Nd PUM ≈ -0.1±1).

  and whole-rock composition; (3) fractionated whole-rock HSE patterns inconsistent with any known chondrite group (e.g. Pd/Ir>2); (4) the coexistence at the thin section scale of several unrelated sulphide populations. However, the most convincing arguments stem from the discrepancies between 143 Nd/ 144 Nd and 187 Os/ 188 Os. It has been recognised that even the most fertile peridotites that were used to estimate the PUM composition show Ndisotope compositions indicative of oldmelting events 6 (i.e. Nd>>0; Figure 5).

Table

Table 2 Compositional

 2

ranges in major and minor elements of olivine (Ol), orthopyroxene (Opx), clinopyroxene (Cpx) and spinel (Spl) for harzburgites and lherzolites, and ranges of Mg# in olivine (= Mg/Mg+Fe cationic ratio) and Cr# in spinel (=Cr/Cr+Al cationic ratio).

Table 3 REE

 3

compositions of clinopyroxene in four representative peridotites: a harzburgite and a lherzolite distal from harzburgites-lherzolites contacts, and the same rock types adjacent to a contact (section 2 in table

1

).

table 1 .

 1 They range from 94% Ol, 4.6% Opx,

	1.2% Cpx and <1% Spl in harzburgites to
	62% Ol, 21% Opx, 15% Cpx and >2% Spl in
	lherzolites. Major and minor elements in
	whole rocks display a wide range of
	variation from highly refractory (e.g., 45.53
	wt% MgO and 0.17 wt% Al 2 O 3 ) to very
	fertile compositions (34.85 wt% MgO and
	4.97 wt% Al 2 O

Modal compositions calculated by linear inversion of whole-rock and mineral compositions for major elements are given in 3 ). Harzburgites collected in the vicinity of lherzolites (< 5m) are more fertile on average than more distal harzburgites. Their modal and major-element compositions partly overlap the composition of lherzolites (e.g., in the range 2-2.5 wt% Al 2 O 3 -Table

Table

  Cr vs. Al 2 O 3 diagram for the peridotites of section 1 and distal samples (table

	FIG. 6:
	. In the case of Lherz, the partial
	melting model is precluded by structural
	observations that show that the harzburgite
	predate the lherzolites. Formation of
	harzburgite-lherzolite	intercalations	by
	variable degrees of melting is also ruled out
	by variations of minor and trace elements in
	peridotites and/or their constituent minerals.
	Chromium, for instance, shows two
	features at odds with the partial melting
	model. First, although highly compatible
	during mantle melting (Liu and O'Neill,
	2004), this element tends to be negatively
	correlated with MgO and positively
	correlated with Al 2 O 3 (Fig. 4). Second,
	harzburgites and lherzolites form two
	different trends on Cr vs. major-element
	correlation diagrams, a feature that reflects
	the bimodal distribution of the Cr content in
	minerals, notably spinel. In contrast with

Table 1 )

 1

	Chapter III	Le Roux et al. (2008), Feedback between melt percolation and deformation
		in an exhumed lithosphere-asthenosphere boundary

. [100] axes of olivine and [001] axes of pyroxenes are parallel to the

  . . ε Nd and ε Hf are defined as (( 143 Nd/ 144 Nd sample / 143 Nd/ 144 Nd CHUR )-1)*10000 and (( 176 Hf/ 177 Hf sample / 176 Hf/ 177 Hf

CHUR )-1)*10000 respectively (e.g. Blichert-Toft and Albarede, 1997). ε Nd and ε Hf are present-day values.The Nd isotopic ranges of Pyrenean harzburgites (H) and lherzolites (L)

  Os/ 188 Os vs. Al 2 O 3, and the negative and positive correlations of 87 Sr/ 86 Sr and 143 Nd/ 144 Nd, respectively, vs. Al 2 O 3 .

	interpreted them as lithospheric strips
	incompletely	mixed	with	pristine
	asthenospheric lherzolites during thermo-
	mechanical erosion of the lithosphere by
	upwelling mantle. Recently, Le Roux et al.

(2007)

suggested that the refertilization scenario was the most likely to explain, at the same time, the positive correlation of 187

Table 2

 2

					. The
	protolith was very likely heterogeneous; for
	modeling we took the most extreme
	composition characterized by the highest
	176 Hf/ 177 Hf and 87 Sr/ 86 Sr and the lowest
	143 Nd/ 144 Nd	values	in	the	studied
	harzburgites. As isotopic composition for the
	melt, we took that of the distal, refertilized
	lherzolite. This sample is comparable to
	other Pyrenean lherzolites unrelated to
	harzburgites (Downes et al., 1991) and is
	therefore considered to be equilibrated with
	the fertilizing, infiltrated melt. In all
	experiments the length of the percolation
	column has been fixed at 100m. This length
	corresponds to the typical distance in the
	Lherz massif between the distal harzburgites,
	which represents the protolith before
	percolation, and the distal lherzolites,
	considered to be fully equilibrated with
	incoming, fertilizing melt. Mineral/melt
	partition coefficients are from Blundy

TABLE OF CONTENTS Technical work Article Mantle refertilisation, osmium isotopes and the "Primitive Upper Mantle" fallacy, Consequences for the nature of the late veneerTable 1 -Crystallographic fabrics strengths of minerals Figure 1 -Crystal-preferred orientations of minerals (CPO)Table 2 -Major and minor elements compositions of minerals from Lherz peridotitesTable 3 -Whole-rock chemical compositions -major and minor elements (ppm)Table 4 -Whole-rocks chemical compositions -trace elements (ppm)

 OF1234

Table 5 -Whole-rocks chemical compositions -trace elements normalized to primitive mantle Figure 2 -Whole-rocks trace elements normalized to primitive mantleTable 6 -Modal compositions of Lherz peridotitesTable 7 -REE clinopyroxenes concentrations (ppm)

 567

Table 8 -REE clinopyroxenes concentrations normalized to chondrites Figure 3 -REE clinopyroxenes concentrations normalized to chondrites Table 9 -Hf, Nd and Sr isotopic ratios of the Lherz peridotites Summary of chemical techniques and methods

 8

Table 1

 1 repository material); dashed curve, sulphide 187 Os/ 188 Os for all Pyrenées lherzolites studied here (n=268; Table

Table RM1 :

 RM1 [START_REF] Alard | Mantle refertilisation, Osmium isotopes and the "Primitive Upper Mantle" fallacy, consequences for the nature of the late veneer[END_REF]

	Sample Lherz Site 2 04LH11 Al 2 O 3 =0.57 wt.% S=38.5 ppm n.Sulf/sectº=1.3 (Pd/Ir)=0.40 04LH12 Al2O3=0.48 wt.% S=36 ppm n.Sulf/sectº=8 04LH13 Al2O3=0.47 wt.% n.Sulf/sectº=28 (Pd/Ir)=1.93 (Pd/Ir)=0,3 ‡ 71-335 Al2O3=2.86 wt.% S= 312 ppm n.Sulf/sectº= 22 (Pd/Ir)=1,46 © 82-4 Al 2 O 3 =1.14 wt.% S= 80 ppm n.Sulf/sectº=10.3 72-442 (Pd/Ir)=0,64 † Al 2 O 3 =1.21 wt.% (Pd/Ir)=0,87 © S= 23 ppm n.Sulf/sectº=2.5 (Pd/Ir)=0.30 ‡ (Pd/Ir)=0.29 ‡ 04LH815 (Pd/Ir)=0,44 ©	N#Sulf A/s1 B/s1 B/s2 C/s1 WR A/s1 A/s2 A/s6 WR A/s1 A/s5a A/s5a A/s5b A/s6 A/s7 A/s8 B/s2 B/s2[rep] A/s14a WR* B/s3 A/s14b B/s4 A/s15 A/s1 A/s16 A/s2 A/s10 WR ‡ A/s17 A/s3 A/s11 A/s18 A/s4 A/s13 A/sX A/s19 A/s4[rep] A/s14 A/s1 A/s20 A/s5 A/s15 A/s2 A/s6 A/s16a A/s3 A/s1 A/s7 A/s16b A/s4 A/s2 A/s8 A/s16c A/s4[rep] A/s2[rep] A/s9a A/s17a A/s5 A/s3 A/s9b A/s18a A/s7a B/s1 A/s9c A/s18b A/s7b B/s2 A/s10a WR A/s1 A/s7b[rep] A/s8a A/s8b A/s9 WR* A/s10b WR ‡ A/s11 WR ‡ A/s15 A/s11a WR*	Os ppm 187 Re/ 187,9 0,0 0022 188 Os 124,0 0,0 0028 41,3 0,0 0275 131,3 0,0022 5.1 4•10 -3 0,0298 34,6 0,2128 74,2 0,0 0207 188,8 0,0 0054 4.8 2•10 -3 0,0437 29,9 0,0297 57,4 0,0335 16,3 0,099 2,5 1,08 6,7 0,256 2,0 0,589 4,3 0,0602 251,2 0,041 208,8 0,0277 11,9 0,511 3.4 7•10 -3 0,228 32,1 0,1 2666 5,7 0,515 131,6 0,0326 6,5 0,0561 7,3 0,0410 5,7 0,0481 6,8 0,143 5,6 0,351 2.8•10-3 0,0 3405 7,3 0,438 5,2 0,550 4,6 0,0722 5,1 0,0286 117,1 0,0046 44,2 1,05 10,4 0,456 10,0 0,0727 128,7 0,059 5,2 0,0550 3,7 0,201 7,0 0,509 119,6 0,142 5,8 0,179 3,1 0,600 1,9 0,813 7,6 0,224 4,2 0,373 108,2 0,0364 21,9 0,355 4,3 0,147 10,5 0,0210 160,4 0,0 0441 3,2 0,726 4,9 0,151 9,5 0,558 142,0 0,0 0396 . 0,383 3,9 0,166 9,7 0,455 57,3 0,177 5,9 0,118 2,1 0,155 18,6 0,0969 397,9 0,0001 9,1 0,004 8,5 0,235 69,7 0,1860 125,1 0,0120 52,9 0,0093 3.9 0•10 -3 0,4590 20,6 0,265 103,2 0,0085 36,5 0,0279 16,5 0,0448 4,5 0,190 2.8 9•10 -3 0,058 35,6 0,040 2.7 9•10 -3 0,051 29,7 0,0088 3.1 7•10 -3 0,045 49,9 0,517 9,6 0,125 4.1 2•10 -3 0,270	2SE 0,00010 0,00012 0,00051 0,00 11 0,00 15 0,00 24 0,00015 0,00013 0,00 22 0,00 17 0,00 45 0,012 0,15 0,030 0,072 0,00 83 0,010 0,00 93 0,079 0,005 0,00086 0,048 0,00 68 0,00 31 0,00 66 0,00 47 0,058 0,056 0,00085 0,027 0,091 0,00 70 0,00 33 0,00 17 0,22 0,018 0,00 50 0,010 0,00 13 0,044 0,042 0,065 0,027 0,026 0,092 0,033 0,027 0,00 61 0,015 0,010 0,00 07 0,00048 0,078 0,018 0,033 0,00007 0,056 0,015 0,018 0,018 0,060 0,020 0,00 77 0,00 00 0,000 0,022 0,00 44 0,00 32 0,00 07 0,00 69 0,027 0,00 09 0,00 50 0,00 40 0,032 0,00 12 0,006 0,00 10 0,00 34 0,00 09 0,030 0,020 0,005	187 Os/ 0,11130 188 Os 0,11134 0,1172 0,1124 0,11586 0,1188 0,1124 0,1100 0,11298 0,1164 0,11290 0,1215 0,153 0,1257 0,1432 0,1281 0,11165 0,11099 0,1251 0,1284 0,1174 0,1349 0,11177 0,1411 0,1270 0,1390 0,1271 0,1318 0,11530 0,1342 0,1330 0,1250 0,1382 0,11147 0,1180 0,1200 0,1288 0,1113 0,1248 0,1489 0,1327 0,11565 0,1217 0,1518 0,1459 0,1210 0,1385 0,1190 0,1207 0,1311 0,1243 0,11756 0,1426 0,1237 0,1239 0,11729 0,1303 0,1287 0,1202 0,1270 0,1241 0,1297 0,1182 0,11109 0,1212 0,1224 0,1116 0,1195 0,1124 0,12857 0,1227 0,1088 0,1110 0,11513 0,1277 0,11780 0,1191 0,11775 0,12001 0,11810 0,1184 0,1219 0,1226	2SE 0 ,00092 0 ,00084 0,0013 0,0024 0 ,00011 0,0018 0,0014 0,0026 0 ,00008 0,0015 0 ,00082 0,0022 0,014 0,0024 0,0053 0,0054 0 ,00078 0 ,00090 0,0068 0,0003 0,0030 0,0048 0 ,00054 0,0030 0,0066 0,0022 0,0040 0,0072 0 ,00080 0,0026 0,0070 0,0032 0,0030 0 ,00072 0,0032 0,0019 0,0020 0,0011 0,0017 0,0046 0,0014 0 ,00040 0,0026 0,0080 0,0050 0,0026 0,0082 0,0013 0,0030 0,0044 0,0013 0 ,00013 0,0042 0,0058 0,0062 0 ,00076 0,0026 0,0040 0,0014 0,0034 0,0040 0,0066 0,0014 0 ,00030 0,0024 0,0056 0,0012 0,0014 0,0012 0 ,00014 0,0040 0,0018 0,0026 0 ,00096 0,0056 0 ,00024 0,0024 0 ,00004 0 ,00098 0 ,00040 0,0024 0,0020 0,0002	TRD (Ga) 2,35 2,34 1,53 2,19 1,72 1,31 2,19 2,53 2,12 1,65 2,13 0,93 -3,64 0,34 -2,19 0,00 2,30 2,39 0,43 -0,04 1,51 -0,98 2,28 -1,88 0,16 -1,57 0,14 -0,53 1,80 -0,88 -0,71 0,44 -1,46 2,33 1,43 1,15 -0,10 2,34 0,47 -3,04 -0,66 1,75 0,90 -3,47 -2,60 1,01 -1,50 1,28 1,04 -0,43 0,54 1,48 -2,11 0,62 0,60 1,52 -0,31 -0,08 1,11 0,16 0,57 -0,23 1,39 2,38 0,98 0,80 2,31 1,21 2,19 -0,07 0,76 2,69 2,39 1,82 0,06 1,45 1,27 1,46 1,14 1,41 1,37 0,88 0,78	2ı ı ı ı 0,03 0,03 0,03 0,08 0,00 0,07 0,05 0,10 0,00 0,04 0,03 0,04 0,52 0,03 0,44 0,00 0,03 0,04 0,22 0,00 0,10 0,32 0,02 0,10 0,02 0,06 0,01 0,37 0,02 0,76 0,25 0,03 0,07 0,03 0,05 0,48 0,00 0,05 0,01 0,44 0,07 0,02 0,06 0,96 0,21 0,09 1,93 0,03 0,30 0,05 0,01 0,00 0,19 0,09 0,19 0,02 0,14 0,01 0,36 0,01 0,05 0,04 0,04 0,01 0,04 0,16 0,08 0,03 0,04 0,00 0,13 0,08 0,10 0,03 0,01 0,01 0,05 0,00 0,02 0,01 0,24 0,04 0,01	TMA (Ga) 2,35 2,34 1,54 2,21 1,85 2,61 2,20 2,53 2,36 1,77 2,31 1,21 2,20 0,87 5,15 0,00 2,54 2,56 -2,05 -0,09 2,15 4,23 2,47 -2,17 0,18 -1,77 0,21 -3,23 1,95 19 2,24 0,53 -1,57 2,35 -0,97 -1 6 -0,12 2,72 0,54 -5,98 3,05 2,62 1,57 7,46 2,67 2,14 -1 5 1,41 6,39 -0,66 0,57 1,50 2,80 0,96 -1,87 1,54 -3,49 -0,13 -15,95 0,28 0,79 -0,37 1,80 2,38 0,99 1,80 4,08 1,25 2,24 0,74 2,04 2,74 2,56 2,03 0,12 1,68 1,40 1,66 1,17 1,58 -6,42 1,25 2,15	2ı ı ı ı 0,02 0,02 0,02 0,04 0,01 0,05 0,02 0,05 0,01 0,02 0,03 0,05 0,56 0,16 2,21 0,07 1,80 0,00 0,06 2,17 0,05 0,05 0,01 0,04 0,04 0,04 0,00 0,01 30 1,58 2,58 0,04 0,02 0,02 8 0,00 0,08 0,34 1,22 1,46 0,61 0,01 1,19 0,64 0,18 8 0,03 1,47 0,36 0,01 0,00 0,72 0,03 0,46 0,01 5,12 0,08 8,53 0,02 0,16 0,01 0,05 0,01 0,02 0,03 0,09 0,02 0,02 0,23 0,13 0,36 0,04 0,06 0,03 0,03 0,01 0,01 0,00 2,01 0,01 0,02 0,09 0,08
	S=27 ppm n.Sulf/sectº=6 (Pd/Ir)=0.25 04LH14 Al 2 O 3 =0.47 wt.% S=57 ppm n.Sulf/sectº=8 04LH09 Al2O3=1.9 wt.% S= ppm n.Sulf/sectº=10 (Pd/Ir)=1.77 Al 2 O 3 =3.50 wt.% S= 188 ppm n.Sulf/sectº=20 04LH06 Al 2 O 3 =3.46 wt.% S= 185 ppm Se=63.5 ppb n.Sulf/sectº=18 72-273 72-425 Al 2 O 3 =3.11 wt.% Al 2 O 3 =3.63 wt.% S= 185 ppm S= 389 ppm n.Sulf/sectº=14 n.Sulf/sectº= 39 Frechynede 'Historic' 71-322 Al2O3=1.5 wt.% S= 56 ppm n.Sulf/sectº=8 (Pd/Ir)=1,09 © (Pd/Ir)=0,76 † 71-339 Al2O3=3.41wt.% S= 244 ppm n.Sulf/sectº=36 (Pd/Ir)=2,02 ©	A/s5b WR A/s1 A/s2 A/s3 A/s8 WR A/s1 A/s2 A/s3 A/s3[rep] A/s4c A/s4a A/s5 A/s8 A/s7 WR A/s2a A/s2b A/s2c A/s3 A/s4 A/s5a A/s5b A/s7 A/s8 A/s10 A/s12a WR A/s1 A/s2 A/s3 A/s4 A/s5 A/s6 A/s7 A/s7[rep] A/s8a A/s8b A/s9 A/s11b B/s1a A/s1 A/ s0 B/s1b A/s2 A/ s1 B/s5 A/s3 A/ s2 B/s6 A/s4 A/ s3 B/s7a A/s5 A/ s4 B/s7b A/s6a A/ s5 B/s7c A/s6b A/ s6 B/s8 A/ s7 B/s8[rep] C/s1 A/ s8 A/ s9 C/s2 C/s3 WR † A/s1 A/s2 A/s6 A/s8 A/s10 B/s2 B/s3 B/s4 B/s6 WR* A/s1 A/s10 A/s1[rep] A/s11 A/s2 A/s14b A/s3 A/s15 A/s4 A/s16 A/s5 A/s20 A/s6 A/s22 A/s18[nug] A/s24a A/s18[all] A/s24b A/s19 A/s25a A/s20 A/s25b A/s21a A/s26a A/s21b A/s26b A/s22a A/s26c A/s22b A/s28	154,6 4.0 0•10 -3 144,4 39,2 29,5 69,6 4.5 8•10 -3 5,9 5,8 9,8 10,2 21,3 9,6 89,8 27,4 3,9 3.4 5•10 -3 16,3 9,4 58,3 11,3 47,1 10,4 4,1 6,7 33,5 13,9 3,6 4.0 3•10 -3 122,4 2,7 11,4 8,5 3,2 5,1 49,6 44,3 4,2 2,0 7,6 25,4 4,5 10,4 8,4 37,5 14,2 7,0 31,9 8,1 7,1 27,4 6,6 4,9 37,5 154,5 4,4 2,6 41,0 413,4 4,9 23,8 1,6 4,1 16,6 5,9 17,8 3,0 2,5 4,9 6,6 4.7 2•10 -3 8,2 14,4 144,2 4,1 12,9 145,4 3,1 6,1 17,3 3.9 1•10 -3 7,9 1,9 8,2 6,9 9,0 2,7 2,8 4,6 5,3 7,7 42,6 5,9 13,4 17,3 90,8 8,5 22,2 27,7 21,4 12,9 8,6 6,9 4,3 90,6 4,1 10,2 11,1 14,4 18,7 6,6	0,0093 0,0422 0,0310 0,0546 0,3053 0,109 0,0819 0,9203 0,8232 0,433 0,404 0,0 0210 0,831 0,0419 0,0035 1,20 0,1770 0,573 0,386 0,807 0,279 0,482 0,64 1,098 0,127 0,893 0,1 8723 0,925 0,447 0,0 0251 0,385 0,383 0,112 0,343 0,081 0,0 0469 0,0 0362 0,188 0,522 0,468 0,461 0,1169 0,0783 0,0097 0,0203 0,498 0,0857 0,2988 0,0617 0,140 0,0260 0,629 0,342 0,555 0,0130 0,184 0,4040 0,147 0,0051 0,184 0,0109 1,235 0,0133 0,244 0,1545 0,1494 0,0583 1,56 0,1454 0,1447 0,075 0,0153 0,627 0,0019 0,088 0,0519 0,0001 0,70 0,078 0,0095 0,0671 0,080 0,768 0,070 1,44 0,288 0,153 0,0143 0,245 0,417 0,0309 0,0683 0,0883 0,668 1,09 0,0305 0,0435 0,246 0,0201 0,0368 0,0998 0,0680 0,1073 0,591 0,013 0,44 0,577 0,1171 0,677 0,757 0,0532	0,00 26 0,00 21 0,00 28 0,00 49 0,00 41 0,010 0,00 41 0,00 19 0,00 11 0,053 0,071 0,00013 0,002 0,00 57 0,00 05 0,13 0,00 44 0,084 0,041 0,080 0,037 0,061 0,1 0 0,068 0,031 0,063 0,00085 0,091 0,012 0,00011 0,034 0,069 0,010 0,043 0,010 0,00014 0,00031 0,025 0,055 0,075 0,030 0,00 57 0,00 34 0,00 08 0,00 27 0,097 0,00 47 0,00 45 0,00 57 0,014 0,00 02 0,078 0,018 0,054 0,00 25 0,011 0,00 31 0,042 0,00 12 0,012 0,00 17 0,094 0,00 13 0,033 0,00 39 0,00 69 0,00 10 0,14 0,00 87 0,00 22 0,00 15 0,00 12 0,026 0,00 05 0,021 0,00 70 0,00 00 0,2 2 0,010 0,00 03 0,00 13 0,015 0,083 0,013 0,23 0,074 0,013 0,00 06 0,023 0,073 0,00 18 0,00 18 0,00 62 0,022 0,13 0,00 66 0,00 20 0,037 0,00 38 0,00 38 0,00 22 0,00 14 0,00 70 0,098 0,020 0,1 1 0,018 0,00 19 0,020 0,042 0,00 18	0,11208 0,11385 0,11124 0,1141 0,1184 0,1117 0,11622 0,1574 0,1428 0,1290 0,1289 0,1365 0,1556 0,1206 0,11270 0,169 0,1207 0,1391 0,1203 0,1115 0,1172 0,1291 0,1423 0,1477 0,1316 0,1117 0,1313 0,1426 0,12788 0,1116 0,1300 0,1159 0,1169 0,1270 0,1196 0,1113 0,1116 0,1220 0,1355 0,1130 0,1159 0,1382 0,1252 0,1316 0,1249 0,1103 0,1356 0,1132 0,1261 0,1332 0,11723 0,135 0,1386 0,12686 0,1103 0,1410 0,1483 0,1150 0,11225 0,1329 0,1197 0,1698 0,1354 0,1288 0,1332 0,12566 0,147 0,137 0,1252 0,1299 0,11410 0,1332 0,1155 0,1124 0,1550 0,1274 0,11188 0,173 0,1435 0,1246 0,1173 0,1207 0,1593 0,1213 0,1392 0,1251 0,1545 0,1211 0,1488 0,1274 0,1336 0,12028 0,1407 0,1193 0,1328 0,12137 0,1312 0,1214 0,1234 0,1215 0,1284 0,1204 0,1341 0,1256 0,1131 0,1317 0,1304 0,1257 0,1244 0,1197 0,1345	0 ,00046 0 ,00012 0 ,00080 0,0016 0,0036 0,0022 0 ,00009 0,0051 0,0044 0,0018 0,0014 0,0044 0,0030 0,0052 0 ,00096 0,017 0 ,00012 0,0024 0,0050 0,0082 0,0036 0,0022 0,0028 0,0064 0,0048 0,0058 0,0012 0,0038 0 ,00012 0,0018 0,0022 0,0016 0,0018 0,0004 0,0028 0,0012 0,0018 0,0022 0,0018 0,0048 0,0024 0,0028 0,0016 0,0042 0,0014 0,0072 0,0056 0,0017 0,0034 0,0024 0 ,00074 0,010 0,0042 0 ,00090 0,0022 0,0060 0,0098 0,0048 0 ,00072 0,0044 0,0050 0,0240 0,0076 0,0012 0,0024 0 ,00082 0,011 0,017 0,0022 0,0020 0 ,00023 0,0046 0,0058 0,0010 0,0060 0,0028 0 ,00044 0,013 0,0056 0,0012 0 ,00023 0,0019 0,0086 0,0016 0,0026 0,0017 0,0056 0,0046 0,0060 0,0044 0,0022 0 ,00044 0,0030 0,0024 0,0042 0 ,00048 0,0030 0,0011 0,0019 0,0013 0,0022 0,0020 0,0030 0,0064 0,0022 0,0060 0,0020 0,0016 0,0024 0,0022 0,0048	2,24 2,00 2,36 1,97 1,37 2,30 1,67 -4,33 -2,13 -0,12 -0,11 -1,20 -4,05 1,06 2,16 -6,09 1,05 -1,59 1,10 2,33 1,54 -0,15 -2,05 -2,86 -0,50 2,29 -0,46 -2,10 0,03 2,31 -0,27 1,72 1,58 0,16 1,20 2,35 2,31 0,86 -1,06 2,12 1,72 -1,46 0,41 -0,50 0,45 2,49 -1,08 2,09 0,28 -0,74 1,53 -0,99 -1,52 0,18 2,49 -1,86 -2,95 1,84 2,22 -0,69 1,18 -6,25 -1,05 -0,10 -0,73 0,35 -2,74 -1,33 0,41 -0,25 1,96 -0,74 1,77 2,19 -3,96 0,09 2,27 -6,71 -2,23 0,50 1,52 1,05 -4,62 0,96 -1,60 0,43 -3,88 0,99 -3,03 0,10 -0,79 1,10 -1,83 1,24 -0,67 0,95 -0,44 0,95 0,67 0,93 -0,05 1,08 -0,86 0,36 2,11 -0,52 -0,33 0,34 0,53 1,18 -0,92	0,02 0,00 0,03 0,06 0,28 0,11 0,00 0,28 0,15 0,12 0,06 0,08 0,18 0,10 0,03 0,89 0,00 0,16 0,95 0,35 0,25 0,04 0,17 0,18 0,06 0,20 0,02 0,10 0,00 0,07 0,11 0,43 0,06 0,01 0,07 0,05 0,07 0,05 0,12 1,79 0,83 0,09 0,01 0,03 0,01 1,81 0,12 0,18 0,02 0,04 0,02 0,33 0,57 0,01 0,09 0,32 0,21 0,03 0,19 0,09 0,10 1,24 0,13 0,00 0,04 0,01 0,58 0,14 0,02 0,01 0,01 0,06 0,35 0,04 0,49 0,00 0,02 1,96 0,25 0,01 0,01 0,04 0,72 0,03 0,03 0,04 0,56 0,07 0,72 0,68 0,03 0,01 0,11 0,08 0,03 0,01 0,02 0,04 0,02 0,02 0,00 0,04 0,05 0,09 0,08 0,99 0,03 0,01 0,03 0,05 0,08	2,29 2,22 2,54 2,26 4,83 3,07 2,07 3,42 2,15 4,23 -2,79 -1,21 3,89 1,17 2,17 3,05 1,81 4,19 11,99 -2,64 4,44 1,02 3,77 1,71 -0,72 -2,12 -0,83 1,70 -0,51 2,32 -3,20 16,62 2,14 0,84 1,49 2,38 2,33 1,54 4,24 -23,5 -2 2 -2,03 0,50 -0,51 0,47 -1 6 -1,35 6,92 0,33 -1,11 1,63 1,95 -8,52 -0,56 2,57 -3,35 2,80 2,25 -1,23 1,21 3,00 -1,09 -0,24 -1,16 0,54 -3,19 0,48 0,62 -0,39 2,38 -0,76 -3,79 2,20 -5,06 0,11 2,27 8,87 -2,75 0,51 1,80 1,30 5,16 1,15 0,65 1,35 -6,21 1,02 -7,54 10 -0,85 1,32 -2,32 -2,17 0,42 1,03 -0,50 2,26 0,70 1,02 -0,06 1,29 -1,15 -0,91 2,18 10 0,90 0,46 -0,88 -1,52 -1,06	0,02 0,01 0,02 0,04 0,22 0,11 0,02 0,14 0,08 18,8 3 11,5 4 0,04 0,09 0,05 0,02 0,67 0,03 2,31 13,9 9 0,58 1,16 1,01 1,73 0,19 0,08 0,30 0,01 0,31 0,23 0,03 3,04 29,9 2 0,07 0,46 0,05 0,02 0,03 0,17 2,31 37,7 3 17 0,01 0,02 0,06 20 0,06 0,01 0,01 0,06 0,27 0,75 1,95 0,01 0,05 0,22 0,23 0,44 0,01 0,05 0,71 0,08 0,04 0,07 0,03 0,29 0,09 0,01 0,02 0,01 0,01 0,03 0,51 0,02 0,40 0,00 0,01 7,05 0,15 0,00 0,01 1,28 0,06 0,15 0,04 0,41 0,75 1,05 0,04 0,02 181 0,07 0,01 0,08 0,20 0,01 0,02 0,01 0,48 0,00 0,01 0,04 0,02 0,11 0,53 0,10 59 0,07 0,01 0,19 0,04
	O4LH07	A/s1 A/s12 WR † A/s22c WR*	6,8 8,1 4.0 3•10 -3 3,9 4.1 5•10 -3	0,307 0,343 0,0544 0,553 0,168	0,074 0,037 0,00 11 0,024 0,003	0,1226 0,1166 0,1235 0,1286 0,1225	0,0070 0,0020 0 ,00025 0,0060 0,0002	0,78 1,61 0,65 -0,07 0,79	0,32 0,26 0,00 0,02 0,01	2,84 8,22 0,75 0,22 1,31	1,85 3,89 0,00 0,04 0,02
	Al 2 O 3 =2.00 wt.%	A/s2 A/s13 A/s23	8,8 4,6 2,0	0,0975 0,528 0,177	0,00 60 0,020 0,039	0,1297 0,1168 0,132	0,0052 0,0032 0,010	-0,23 1,59 -0,61	0,03 0,34 0,17	-0,30 -6,70 -1,05	0,01 1,26 0,19
	S= 139 ppm 71-324 Fontete Rouge 'historic' A/s3 A/s16 A/s1a A/s24a	10,8 1,7 412,2 10,6	0,0640 0,81 0,0098 0,0466	0,00 58 0,15 0,00 06 0,00 92	0,1261 0,1382 0,11109 0,1267	0,0026 0,0062 0 ,00058 0,0018	0,29 -1,46 2,38 0,19	0,01 0,15 0,02 0,01	0,34 1,52 2,43 0,22	0,01 0,59 0,01 0,01
	Se=42.4 ppb n.Sulf/sectº= O4LH04 Al2O3=3.22 wt.% S= 165 ppm n.Sulf/sectº=17 Al2O3=2.96 wt.% S= 170 ppm n.Sulf/sectº= 24 (Pd/Ir)=2,05 ® FON-B-93 Al2O3=3.23 wt.% S= 277 ppm n.Sulf/sectº= 16 (Pd/Ir)=1,85 ® (Pd/Ir)=1,78 @ 71-336 Al2O3=3.45wt.% S= 179 ppm 71-326 n.Sulf/sectº=24 Al2O3=3.58 wt.% (Pd/Ir)=1,81 ® S= 170 ppm 04LH15 Al2O3=3.99 wt.% S= 203 ppm 71-323 Al2O3=0.76 wt.% S= 22 ppm n.Sulf/sectº=3.5 Lherz 'Historic' n.Sulf/sectº= 28	A/s4 A/s5a A/s5c A/s7 A/s10 A/s14 A/s14[rep] A/s15a A/s15a[rep] A/s15b A/s17 A/s18 WR WR[rep] A/s2 A/s3b A/s4 A/s5 A/s5b A/s6 A/s7 A/s9 A/s1b A/s3 A/s2 A/s2[rep] A/s5 A/s6a A/s6b A/s8 A/s10 A/s24b A/s24c A/s1a A/s25a A/s1b A/s25b A/s1c A/s26 A/s2a A/s27 A/s2b A/s28 A/s3a A/s30 A/s3a[rep] A/s3c A/s11 WR* A/s4 A/s14 A/s5 A/s2 A/s6 A/s19 A/s10 WR* A/s4 A/s8 A/s22a A/s11 A/s5a A/s9 A/s22b A/s12 A/s3 A/s5a[rep] A/s10 A/s25 A/s15 A/s4 A/s6 A/s11 A/s26 A/s17 A/s5 A/s8 A/s12 A/s27a A/s27c WR A/s1 A/s2 A/s3 A/s1 A/s1[rep] A/s2 A/s3 A/s13c A/s21 A/s13b A/s20 A/s13a A/s23 A/s12 A/s19 A/s11 A/s18 A/s10 A/s16 A/s7 A/s15 WR A/s6a A/s6b A/s10 A/s13 WR (AL)	4,2 4,5 9,2 4,0 5,0 7,1 9,0 1,5 2,0 3,1 19,6 2,2 3.2 8•10 -3 3.5 1•10 -3 3,8 3,7 4,5 9,7 16,3 11,1 16,3 13,4 1,9 291,0 184,9 106,1 93,3 12,4 16,6 19,8 12,8 9,6 120,2 12,0 6,6 12,5 5,9 4,3 10,7 5,9 15,2 12,1 8,1 4,8 3,3 2,7 4,5 7,1 6,5 3.4 7•10 -3 7,3 127,0 7,9 2,8 5,0 5,0 6,6 3.9 2•10 -3 117,1 20,1 7,8 5,6 1,9 68,1 183,9 13,3 29,3 1,7 38,9 3,3 107,1 14,0 3,4 5,3 4,7 24,8 37,5 5,9 25,0 26,8 18,1 4.5 7•10 -3 6,2 158,6 34,1 39,2 33,9 102,9 39,8 6,1 8,9 7,5 40,0 154,9 1,4 21,2 1,2 5,5 2,4 8,3 2,8 14,7 2,2 3.7 1•10 -3 23,8 5,9 18,1 13,3 4.4•10 -3	0,89 0,82 0,358 0,223 0,0542 0,0361 0,059 1,190 0,97 0,295 0,745 0,376 0,442 0,398 1,063 0,784 0,38 0,186 0,225 0,3884 0,222 1,29 0,0007 0,0070 0,0117 0,0155 0,085 0,0458 0,425 0,524 0,0812 0,0217 0,671 0,518 0,0488 0,409 0,539 0,349 0,339 0,677 0,572 0,211 0,152 0,814 0,852 0,876 0,397 0,1856 0,2995 0,429 0,0110 0,223 0,436 0,585 0,340 0,611 0,302 0,0046 0,125 0,0232 1,04 0,566 0,013 0,0112 0,264 0,0878 0,512 0,684 0,343 0,1129 0,108 0,0123 0,202 0,151 0,398 0,362 0,0374 0,780 0,700 0,883 0,1237 0,191 0,0023 0,753 0,0 0233 0,0 0136 0,0 0036 0,0 0039 0,429 0,187 0,4215 0,049 0,0121 1,59 0,254 0,83 0,1688 0,0734 0,354 0,0997 0,0 0539 0,0297 0,3637 0,217 0,0820 0,0200 0,093	0,1 7 0,1 6 0,081 0,017 0,00 53 0,00 39 0,010 0,078 0,16 0,048 0,095 0,068 0,013 0,012 0,220 0,088 0,1 1 0,018 0,029 0,00 57 0,052 0,21 0,00 00 0,00 11 0,00 03 0,00 05 0,018 0,00 14 0,047 0,022 0,00 28 0,00 68 0,068 0,095 0,00 82 0,028 0,061 0,019 0,034 0,028 0,088 0,013 0,012 0,028 0,090 0,017 0,023 0,00 12 0,00 60 0,023 0,00 13 0,011 0,061 0,015 0,057 0,023 0,00 60 0,00 17 0,029 0,00 13 0,2 1 0,080 0,004 0,00 11 0,020 0,00 89 0,028 0,041 0,014 0,00 11 0,012 0,00 09 0,017 0,016 0,079 0,042 0,00 08 0,045 0,065 0,018 0,00 36 0,036 0,00 05 0,063 0,00018 0,00037 0,00005 0,00002 0,088 0,014 0,00 26 0,010 0,00 26 0,2 5 0,026 0,2 0 0,00 71 0,00 51 0,065 0,00 40 0,00032 0,00 30 0,00 55 0,031 0,00 66 0,00 09 0,010	0,1395 0,1319 0,1285 0,1268 0,1350 0,1239 0,1222 0,1488 0,1397 0,1294 0,1382 0,1375 0,12830 0,12583 0,166 0,1482 0,1239 0,1252 0,1301 0,1344 0,1319 0,167 0,11136 0,1147 0,11901 0,11853 0,1360 0,12847 0,1275 0,1312 0,1413 0,1115 0,1154 0,13703 0,1255 0,13921 0,1247 0,13440 0,1137 0,13278 0,1130 0,13011 0,1262 0,15001 0,1372 0,15194 0,13490 0,1526 0,12680 0,13441 0,11895 0,13413 0,1329 0,14149 0,1337 0,1477 0,12590 0,11269 0,12613 0,1219 0,119 0,1426 0,12016 0,1102 0,1256 0,12575 0,1412 0,12268 0,1349 0,1129 0,1346 0,1207 0,13493 0,1368 0,1298 0,1273 0,1230 0,12773 0,1281 0,1374 0,12435 0,1290 0,1115 0,1109 0,1207 0,1183 0,1117 0,11898 0,1313 0,1249 0,1559 0,12032 0,11146 0,1264 0,12752 0,148 0,1416 0,1218 0,1393 0,1241 0,1323 0,130 0,12471 0,1294 0,1510 0,1242 0,1252	0,0056 0,0042 0,0010 0,0036 0,0074 0,0060 0,0046 0,0066 0,0062 0,0068 0,0024 0,0052 0 ,00007 0 ,00011 0,026 0,0082 0,0028 0,0032 0,0046 0,0013 0,0034 0,030 0 ,00078 0,0011 0 ,00078 0 ,00056 0,0022 0 ,00098 0,0022 0,0012 0,0010 0,0020 0,0034 0 ,00340 0,0017 0 ,00200 0,0072 0 ,00164 0,0066 0 ,00280 0,0074 0 ,00280 0,0056 0 ,00640 0,0112 0 ,00780 0 ,00194 0,0016 0 ,00025 0 ,00142 0 ,00056 0 ,00320 0,0044 0 ,00200 0,0020 0,0032 0 ,00025 0 ,00072 0 ,00220 0,0058 0,011 0,0065 0 ,00054 0,0018 0,0056 0 ,00044 0,0031 0 ,00220 0,0030 0,0011 0,0016 0,0066 0 ,00420 0,0022 0,0014 0,0017 0,0028 0 ,00660 0,0036 0,0032 0 ,00018 0,0050 0,0027 0,0096 0,0013 0,0024 0,0012 0 ,00090 0,0062 0,0011 0,0036 0 ,00080 0 ,00032 0,0260 0 ,00090 0,017 0,0048 0,0068 0,0032 0,0086 0,0020 0,014 0 ,00020 0,0020 0,0034 0,0012 0,0010	-1,65 -0,55 -0,06 0,18 -0,99 0,60 0,84 -3,02 -1,68 -0,18 -1,46 -1,36 -0,03 0,32 15,95 -5,65 -2,94 0,59 0,41 -0,28 -0,91 -0,54 -5,78 2,34 1,88 1,28 1,35 -1,14 -0,05 0,08 -0,44 -1,91 2,32 1,79 -1,29 0,37 -1,60 0,49 -0,90 2,02 -0,67 2,12 -0,29 0,27 -3,21 -1,31 -3,50 -0,98 -3,60 0,19 -0,91 1,29 -0,87 -0,69 -1,94 -0,81 -2,86 0,31 2,16 0,28 0,87 1,29 -2,10 1,12 2,50 0,36 0,33 -1,90 0,77 -0,97 2,13 -0,94 1,05 -0,98 -1,25 -0,24 0,12 0,72 0,05 0,00 -1,34 0,53 -0,12 2,31 2,41 1,05 1,38 2,30 1,29 -0,46 0,45 -4,10 1,10 2,33 0,24 0,08 -2,96 -1,95 0,89 -1,62 0,57 -0,60 -0,33 0,48 -0,19 -3,35 0,55 0,41	0,13 0,04 0,01 0,02 0,14 0,06 0,07 0,17 0,12 0,07 0,07 1,15 0,00 0,01 1,55 0,43 0,27 0,04 0,04 0,26 0,06 1,38 0,03 0,03 0,02 0,01 0,05 0,00 0,28 0,03 0,04 0,08 0,17 0,28 0,01 5,14 0,21 0,14 1,02 0,05 0,75 0,03 0,04 0,33 0,23 0,39 0,61 0,17 0,00 0,75 0,01 0,09 1,19 0,15 0,13 0,30 0,00 0,02 0,01 0,09 0,16 0,59 0,01 0,07 0,09 0,00 0,39 0,04 0,26 0,05 0,03 0,11 0,13 0,07 0,10 0,02 0,04 0,01 0,00 0,06 0,00 0,02 0,10 0,50 0,02 0,05 0,04 0,02 2,00 0,01 13,85 0,02 0,01 0,04 0,00 0,84 0,25 0,12 0,56 0,10 0,02 0,08 0,01 0,01 0,23 0,01 0,01	1,45 0,57 -0,39 0,39 -1,14 0,65 0,98 1,59 1,26 -0,60 1,85 -13,9 0,55 5,70 3,43 3,23 6,02 0,73 -0,61 -12,9 -1,15 2,61 2,34 1,91 1,32 1,40 -1,44 -0,06 -8,16 1,75 -2,38 2,44 -3,13 5,27 0,42 -163 -1,78 -5,53 9,67 1,09 -6,31 -0,58 0,42 3,26 1,25 3,07 -2 0 -6,60 0,64 34 1,33 -1,85 17,02 4,71 -4,35 5,89 1,10 2,18 0,40 0,93 -0,89 5,71 1,16 2,56 0,96 0,42 8,11 -1,25 -5,43 2,90 -1,26 1,08 -1,90 -1,96 -4,57 0,85 0,79 -0,06 0,00 1,19 0,75 -0,22 2,33 -3,20 1,39 2,30 1,29 20 0,80 243 1,24 2,39 -0,09 0,21 2,89 1,05 -3,29 1,08 -11,0 0,75 -0,60 -0,35 3,45 -0,39 -4,19 0,58 0,52	0,53 0,23 0,50 0,04 0,07 0,03 0,04 0,18 0,37 0,23 0,54 0,33 3,09 1,41 0,81 16,7 1 0,06 0,09 2,25 0,30 0,93 0,01 0,02 0,01 0,01 0,08 0,00 85,6 1 0,38 0,06 5,14 0,85 385 0,01 1,47 0,93 0,12 4,02 0,04 3,69 0,29 0,03 0,22 0,29 19 0,03 0,03 92 0,09 0,11 0,01 70,7 8 0,44 20,7 8 0,73 0,06 0,02 0,04 3,08 0,31 3,17 0,01 0,04 0,13 0,01 2,51 0,20 0,04 0,03 0,05 0,06 0,16 0,98 15,5 9 0,60 0,02 0,01 0,12 0,00 0,04 0,05 0,66 0,01 218 0,05 0,01 1269 0,03 0,02 0,02 0,03 0,03 0,03 1,47 0,16 0,06 0,01 10,7 0,05 0,01 0,04 0,06 0,33 0,06 0,14 0,01 0,02

  Put 12ml of 2.5N HCl/0.1N HF to collect Hf. Dry on the hot plate at 150°C. Samples are then made up into 2% HNO 3 ready for analysis by MC-ICPMS. Nd specific column (2) -This column will remove the Ba, La, Ce, Pr, and Sm from the samples. Method used is adapted from Pin et al.53 . Glass biorad columns (5cm in length) are used. Approximately 5cm of resin (Eichrom® Ln Spec resin) is added (approx. 300mg). The resin is turned into a slurry with 1N HCl and then added to the column.

	*Cleaning columns (3)
	-10ml of 4N HF.
	-Backflushing with 25ml MQ water.
	-15ml of 6N HCl.
	-25ml of 2.5N HCl to recondition columns
	-5 ml of 2.5N HCl before loading.

* *Cleaning columns -Full reservoir of 1N HCl. Repeat 2 times.

Acknowledgments iii

Acknowledgments

This thesis results from the collaboration between Geosciences Montpellier (France) and GEMOC ARC National Key Centre (Australia). This work has been supported by INSU DYETI Program, University of Montpellier II, Macquarie University, ARC Discovery project grants, the French Ministry of Research and 'Bourses Lavoisier cotutelle'.

I want to thank all the people who have been implicated in my work during these three years, and particularly my official supervisors Jean-Louis Bodinier, Alain Vauchez and Suzanne O'Reilly. I am also grateful to Andrea Tommasi and Olivier Alard who were involved in some

Acknowledgements

Acknowledgments

We thank Ben Holtzman and Günter Suhr for their constructive reviews. D. Mainprice provided softwares for analysing/plotting CPO data and C. Nevado and D. Delmas supplied high quality polished thin sections for EBSD measurements. This study was partially funded by the Institut National des Sciences de l'Univers (CNRS/INSU) program 'Dynamique et Evolution de la Terre Interne' (DyETI). This is contribution no 544 from the GEMOC ARC National Key Centre.

References: end of thesis manuscript.

Acknowledgements

Trace element and isotope data were obtained at GEMOC using instrumentation funded by ARC LIEF, DEST Systemic Infrastructure Grants, Macquarie University and industry, and the work was supported by ARC Discovery project grants (OA, SYO'R and WLG) and INSU DYETI Program. VLR also got funding from the French Ministry of Research and from 'Bourses Lavoisier' for the collaboration with Australia. Peter Wieland and Norman Pearson are deeply thanked for assistance and advice during the isotopic work. We thank James Van Orman and Anette von der Handt for their help in the estimation of elements diffusivities, and Nadine Wittig and an anonymous reviewer for their constructive reviews. This is contribution no. XX from the GEMOC ARC National Key Centre. References: end of thesis manuscript. Acknowledgments We thank N.J. Pearson, P. Wieland and S. Elhou for assistance with chemistry and mass spectrometry, C. Countenceau (the Gypaete barbue crew) and "Momo" for field assistance and S. Demouchy and A. Luguet for comments. Analytical data were obtained at GEMOC, using instrumentation funded by ARC LIEF, a DEST Systemic Infrastructure Grant, Macquarie University and industry. O.A. thanks the Royal Society and the Australian Research Council for financial support. This is publication XXX from the ARC National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC).

This study was supported by the DyETI programme of INSU-CNRS and the Laboratoire de Tectonophysique, Montpellier. We thank Fred Frey for his comments on an earlier version of this paper, and Martin Menzies and Cin-Ty Lee for their constructive reviews.

Chapter V Conclusion

Tommasi, A., Godard, M., Coromina, G., Dautria, J.-M., Barsczus, H., 2004. Seismic anisotropy and compositionally induced velocity anomalies in the lithosphere above mantle plumes: a petrological and microstructural study of mantle xenoliths from French Polynesia. Earth and Planetary Science Letters. 227, 539-556. Tommasi, A., Mainprice, D., Canova, G., Chastel, Y., 2000. Viscoplastic self-consistent and equilibrium-based modeling of olivine lattice preferred orientations. Implications for upper mantle seismic anisotropy. Journal of Geophysical Research. 105, 7893-7908. Tommasi, A., Tikoff, B., Vauchez, A., 1999. Upper mantle tectonics: three-dimensional deformation, olivine crystallographic fabrics and seismic properties. Earth and Planetary Science Letters. 168, 173-186. Tommasi, A., Vauchez, A., 2001. Continental rifting parallel to ancient collisional belts: an effect of the mechanical anisotropy of the lithospheric mantle. Earth and Planetary Science Letters. 185, 199-210. Tommasi, A., Vauchez, A., Fernandes, L.A.D., Porcher, C.C., 1994. Magma-assisted strain localization in an orogen-parallel transcurrent shear zone of southern Brazil. Tectonics. 13, 421-437. Tommasi, A., Vauchez, A., Ionov, D., 2008. Deformation, static recrystallization, and influence of temperature, pressure, and ionic radius, and an elastic model for diffusion in silicates. Contributions to Mineralogy and Petrology. 141, 687-703. Vasseur, G., Vernières, J., Bodinier, J.-L., 1991. Modelling of trace element transfer between mantle melt and heterogranular peridotite matrix. Journal of Petrology. 41-54. Vauchez, A., Barruol, G., 1996. Shear-wave splitting in the Appalachians and the Pyrenees: importance of the inherited tectonic fabric of the lithosphere. Physics of The Earth and Planetary Interiors. 95, 127-138. Vauchez, A., Dineur, F., Rudnick, R., 2005. Microstructure, texture and seismic anisotropy of the lithospheric mantle above a mantle plume: insights from the Labait volcano xenoliths (Tanzania). Earth and Planetary Science Letters. 232, 295-314. Vauchez, A., Garrido, C., 2001. Seismic properties of an asthenopherized lithospheric mantle: constraints from lattice preferred orientations in peridotite from the Ronda massif.

Earth and Planetary Science Letters. 192, 235-249. Vauchez, A., Tommasi, A., 2003. Wrench faults down to the asthenosphere: Geological and geophysical evidence and thermo-mechanical effects. in: F. Storti, R.E. Holdsworth, F. Salvini (Eds), Intraplate strike-slip deformation belts. Geol. Soc. London Spec. Publ., London, 15-24. Vernières, J., Godard, M., Bodinier, J.-L., 1997 Pyrenées peridotites whole-rock compositions 10,18,19,42 . Grey squares are whole-rock spinel-websterites (unpublished data). Solid and dashed lines denote the PUM composition 6,7,10 . The Insert shows the same sulphides plotted in 187 Os/ 188 Os-1/Os space. Such a linear correlation is symptomatic of a mixing trend. Note the agreement with the bulk-rock composition (estimated after Os and corrected S whole-rock content and using a pentlandite composition S=33 wt.%)

One end-member corresponds to a "relict" depleted component found in all peridotite samples irrespective of their

Supplementary material

Table RM1(caption):

Sample information: Al 2 O 3 content (in W.t. %) and S content (in ppm) are from Bodinier (1989), Pattou et al., 1995, Lorand et al., 1999Le Roux et al., 2007 (Ref-13); Pd/Ir from ®, Pattou et al., 1995;©, Lorand et al., 1999;†, Becker et al., 2006 (Ref-10); ‡, Luguet et al., 2007 (Ref-42), @, Lorand et al., 2008 (Ref-37).

Whole rock (WR) Re-Os Composition; *, Reisberg & Lorand, 1995 (Ref-19); ‡, Luguet et al., 2007 (Ref-42); †, Becker et al., 2006 (Ref-10) and unpublished data from A. Luguet ( AL ). Unless reported by the authors, 2SE (standard error) was set at 0.2% and 2% for 187 Os/ 188 Os and 187 Re/ 188 Os respectively. Sulfide: N# Denotes the sulphide number in a given section; A,B, C are the thin section numbers; [rep] denotes replicate i.e. a second analysis of the same large sulphide grain (Ø>120 µm).

Os sulphide content: Note, that the method used, laser ablation MC-ICP-MS 25 , only allows determination of mass ratio, and not Re and Os concentrations, as internal normalisation is not possible. Thus, Os concentrations (given in ppm) are estimates computed from Os voltage measured on sulphide and on the PGE-A standard bracketing the analyses.

Average uncertainties using this method are at least about 20% when internal error on voltage measurements and external reproducibility for PGE-A are propagated through; other sources of uncertainties are: between-run variation of laser output energy, gas flow fluctuation, ... Re-Os isotopic composition: SE, standard error of means, Data are processed in time-resolved mode as described in Pearson et al., (2002;Ref-25). We emphasize here that the correction for 187 Re overlap on 187 Os has been demonstrated to be reliable only for sulphide having 187 Re/ 188 Os≤1 (Pearson et al., 2002;Ref-25), Therefore, data in italics (high Re/Os sulphides) are for information only. They are reported in order to show the reader that sulphide with high 187 Re/ 188 Os (>1) occur and because they show values broadly consistent with sulphides from the same sample having lower Re/Os ratio.

Consequently the reader must be aware that our sampling is biased toward sulphides having Os content >1 ppm and low Re/Os.

Summary of chemical techniques and methods

Preparation of Clinopyroxenes separates

We sampled 16 peridotites in the Lherz massif (Pyrenees, France) from where clinopyroxenes were separated. The rocks have been cut using diamond saw. Once the rims had been removed, the interiors were crushed in a steel crusher, carefully cleaned after each sample to avoid crosscontamination. Aliquots of the crushed samples were ground in agate mortars to produce whole-rocks powders. Another aliquot was sieved. Only fractions of < 200µm, < 250µm and < 350µm were used later on. These fractions have been washed with pure water to remove dust and dried in an oven. Then the minerals were passed through a Frantz magnetic separator, which allows the separation of clinopyroxene from orthopyroxene, olivine and spinel (from the less to the most magnetic mineral). -Samples were then initially dissolved in 2ml of 27N HF (merck, suprapur grade) and 2ml of HNO 3 (Ajax) . The beakers were closed and placed on the hotplate at150°C overnight. The samples were then dried down and the above step was repeated.

-When dry, add 10-15 drops of HCLO 4 (merck suprapur grade) to the samples. The HCLO 4 was then dried down at 150°C for a few hours and then the temperature was slowly increased to 200°C. Once all of the HCLO 4 evaporated, 4ml of 6N HCl (merck) and 200µl of H 2 O 2 was added and refluxed for 2 hours at 150°C. This step reduces the Cr 6+ to Cr 3+ . The Cr 3+ passes through independently of Hf whereas Cr 6+ does not. Also, Cr 6+ sticks to the anion exchange resin and causes a large amount of the Hf to be lost as it damages the resin and competes with complexation sites 52 .

The samples are then dried down at 150°C and then one more dissolution in 6N HCl is carried out, the samples are then dried and 1.4ml of 2.5N HCl / 0.1N HF is added to the samples. Samples are transferred to 2ml microcentrifuge tubes and centrifuged to remove and precipitate prior to column separation.

*Columns (1) -Collect Hf, Sr, Nd *Hf collection -5.4ml.

-Samples were loaded into Teflon columns containing Biorad® AG50W-X8 (200-400mesh) cation exchange resin with a bed height of 18cm and an I.D of 6.4mm. -Once the sample eluted, 1ml of 2.5N HCl/ 0.1N HF was added. This step was carried out a total of 4 times. -The samples were then dried down and prepared for the second Hf separation column as the Hf in this step was eluted with the bulk of the sample matrix. -Before Sr could be collected, 21.5ml of 2.5N HCl was added, to remove elements such as Rb and Ca.