Thomas Poitrenaud
email: thomas.poitrenaud@hotmail.fr

Marc Poujol

Romain Augier

Eric Marcoux

The polyphase evolution of a late Variscan W/Au deposit (Salau, French Pyrenees): insights from REE and U/Pb LA-ICP-MS analyses

Keywords: Tungsten, Salau deposit, Polyphase ore formation, REE analyses

The Salau deposit, located in the Axial Zone of the French Pyrenees, is the most important tungsten deposit ever mined in France. Two types of mineralization, both closely associated with a granodiorite intrusion, are distinguished. The first is a fine-grained scheelite skarn related to contact metamorphic and metasomatism between the intrusion and the adjacent carbonate rocks. The second type is represented by massive sulfides accompanied by coarse-grained scheelite, apatite, and electrum. This syn-kinematic mineralization is found enclosed within the skarn ore but occurs also within the granodiorite stock along major ductile-brittle shear zones. REE contents of scheelite and apatite from the two types of mineralization show differences sug-gesting that the two types derived from two different fluids. U/Pb dating on zircon, apatite and scheelite illustrates that magmatic zircon and apatite formed at 295 ± 2 Ma during emplacement and cooling of the granodiorite intrusion. These are cogenetic to the fine-grained scheelite skarn. Hydrothermal apatite from massive sulfide ores yields a younger age of 289 ± 2 Ma, whereas closely associated coarse-grained scheelite yields a consistent although less precise age of 284 ± 11 Ma. These results suggest that the late massive sulfide ore with abundant coarse-grained scheelite and electrum is related to the emplacement of an underlying, more evolved intrusion, accompanied during its ascent by the development of steeply dipping reversedextral shear zones.

Introduction

Mineral deposits are the result of a complex combination of geological processes that cause local metal enrichment in the Earth's crust. Geochemical tools may be applied to identify these processes. Among these tools, development of laser ab-lation inductively coupled plasma mass spectrometry (LA-ICP-MS) in situ analyses can provide either the age of the U-Th bearing phases associated with mineralization or their geo-chemical signature [START_REF] Sylvester | Trace element analysis of scheelite by excimer laser ablation-inductively coupled plasma-mass spectrome-try (ELA-ICPMS) using a synthetic silicate glass standard[END_REF][START_REF] Jackson | The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U-Pb zircon geochronology[END_REF][START_REF] Cocherie | Comparative use of TIMS and SHRIMP for U-Pb zircon dating of A-type granites and mafic tholeiitic layered complexes and dykes from the Corsican Batholith (France)[END_REF][START_REF] Harley | Zircon behavior and the thermal histories of mountain chains[END_REF][START_REF] Raju | Scheelite geochemical signa-tures by LA-ICP-MS and potential for rare earth elements from Hutti Gold Mines and fingerprinting ore deposits[END_REF][START_REF] Mao | Apatite trace element compositions: a robust new tool for mineral explora-tion[END_REF][START_REF] Poulin | Assessing scheelite as an ore-deposit discriminator using its trace element and REE chemistry[END_REF]. Due to recent developments of U/Pb dating of minerals, geochronology now allows to date successive mineralizing and alteration events. A wide range of minerals and isotopic systems are now used for direct dating of ore minerals including Rb/Sr on sphalerite [START_REF] Nakai | Rb-Sr dating of sphalerites from Mississippi Valley-type (MVT) ore deposits[END_REF][START_REF] Christensen | Direct dating of sulphides by Rb-Sr: a critical test using the Polaris Mississippi Valley-type Zn-Pb deposit[END_REF]; Re/Os on sulfide minerals [START_REF] Stein | Re-Os ages for Archean molybdenite and pyrite, Kuittila-Kivisuo, Finland, and Proterozoic molybdenite, Kabeliai, Lithuania: testing the chronom-eter in a metamorphic and metasomatic setting[END_REF][START_REF] Stein | Re-Os dating of low-level highly radiogenic (LLHR) sulfides: the Harnäs gold deposit, south-west Sweden, records continental-scale tectonic events[END_REF][START_REF] Morelli | Rhenium-osmium geochronology of arsenopyrite in Meguma group gold deposits, Meguma Terrane, Nova Scotia, Canada: evidence for multiple gold-mineralizing events[END_REF]; K/Ar and Ar/Ar on Mn oxides [START_REF] Vasconcelos | Age and duration of weathering by 40 K-40 Ar and 40 Ar/ 39 Ar analysis of potassium-manganese oxides[END_REF][START_REF] Ruffet | A geochronological 40 Ar/ 39 Ar and 87 Rb/ 86 Sr study of K-Mn oxides from the weathering sequence of Azul, Brazil[END_REF][START_REF] Spier | 40 Ar/ 39 Ar geochrono-logical contraints on the evolution of lateritic iron deposits in the Quadrilatero Ferrifero, Minas Gerais, Brazil[END_REF], illite [START_REF] Bechtel | Indirect age determination of Kuperfschiefer-type mineralization in the Polish Basin by K/Ar dating of illite; preliminary results[END_REF][START_REF] Clauer | Relating unconformity-type uranium mineralization of the Alligator Rivers uranium field (Northern Territory, Australia) to the regional Proterozoic tectono-thermal activity; an illite K/Ar dating approach[END_REF][START_REF] Bozkaya | Illite occurrences related to volcanic-hosted hydrothermal mineralization in the Biga Peninsula, NW Turkey; implications for the age and origin of fluids[END_REF], adularia [START_REF] Lang | Ar-Ar dating of adularia; a tool in understanding genetic relations between volcanism and mineralization; Baia Mare area (Gutii Mountains), northwestern Romania[END_REF][START_REF] Sanematsu | The history of vein formation determined by 40 Ar/ 39 Ar dating of adularia in the Hosen-1 vein at the Hishikari epithermal gold deposit, Japan[END_REF][START_REF] Oze | 40 Ar/ 39 Ar dating and thermal model-ing of adularia to constrain the timing of hydrothermal activity in magmatic settings[END_REF], lepidolite [START_REF] Smith | Compositional con-trols on 40 Ar/ 39 Ar ages of zoned mica from a rare-element pegma-tite[END_REF]; or Sm/Nd on fluorite [START_REF] Chesley | Samarium-neodymium direct dating of fluorite mineralization[END_REF][START_REF] Chesley | Direct dating of Mississippi Valley-type mineralization; use of Sm-Nd in fluorite[END_REF], and scheelite [START_REF] Bell | Sm-Nd and Rb-Sr isotope systematics of scheelite: possible implications for the age and genesis of vein-hosted gold deposits[END_REF][START_REF] Anglin | Sm-Nd dating of scheelite and tourmaline: implications for the genesis of Archean gold deposits, Val d'Or, Canada[END_REF][START_REF] Eichhorn | Implications of U-Pb SHRIMP zircon data on the age and evolution of the Felbertal tung-sten deposit (Tauern Window, Austria)[END_REF]). The U-Th/Pb system allows to date uraninite [START_REF] Ludwig | Age of uranium mineralization at the Jabiluka and Ranger uranium deposits, Northern Territory, Australia: new U-Pb isotope evidence[END_REF][START_REF] Bowles | Age dating of individual grains of uraninite in rocks from electron microprobe analysis[END_REF][START_REF] Fayek | U and Pb isotope analysis of uranium minerals by ion microprobe and the geochronology of the McArthur River and Sue Zone uranium deposits, Saskatchewan, Canada[END_REF][START_REF] Ballouard | Magmatic and hydrothermal behavior of uranium in syntectonic leucogranites: the uranium mineralization associated with the Hercynian Guérande granite (Armorican Massif, France)[END_REF][START_REF] Ballouard | Uranium metallogenesis in the peraluminous leucogranites from the Pontivy-Rostrenen magmatic complex (French Armorican Hercynian Belt): the result of long term oxidizing hydrothermal alteration during strike-slip deformation[END_REF], heterogenite [START_REF] Decrée | Geodynamic and climate controls in the forma-tion of Mio-Pliocene world-class oxidized cobalt and manganese ores in the Katanga province, DR Congo[END_REF][START_REF] Decrée | Dating of U-rich heterogenite: new insights into U deposit genesis and U cycling in the Katanga Copperbelt[END_REF], apatite [START_REF] Pochon | U/Pb LA-ICP-MS dating of apatite in mafic rocks: evidence for a magmatic event at the Devonian-Carboniferous boundary in the Armorican Massif (France)[END_REF][START_REF] Ballouard | Uranium metallogenesis in the peraluminous leucogranites from the Pontivy-Rostrenen magmatic complex (French Armorican Hercynian Belt): the result of long term oxidizing hydrothermal alteration during strike-slip deformation[END_REF], columbite-tantalite [START_REF] Romer | U/Pb dating of columbites: a geochronological tool to date magmatism and ore deposits[END_REF]Romer and Lehmann 1995;[START_REF] Smith | U-Pb columbite-tantalite chronology of rare-element pegmatites using TIMS and laser ablation-multi collector-ICP-MS[END_REF][START_REF] Che | In situ U/Pb isotopic dating of columbite-tantalite by LA-ICP-MS[END_REF][START_REF] Melleton | Rare-elements (Li-Be-Ta-Sn-Nb) magmatism in the European Variscan Belt, a review[END_REF][START_REF] Tchunte | Evidence for Nb-Ta occurrences in the syn-tectonic Pan-African Mayo Salah leucogranite (Northern Cameroon): constraints from Nb-Ta oxide mineralogy, geochemistry and U-Pb LA-ICP-MS geo-chronology on columbite and monazite[END_REF], wolframite [START_REF] Frei | Re-Os, Sm-Nd, U/Pb, and stepwise lead leaching isotope systematics in shearzone hosted gold mineralization: genetic tracing and age constraints of crustal hydrothermal activity[END_REF][START_REF] Romer | Direct dating of hydrothermal W minerali-zation: U/Pb age for hübnerite (MnWO4), Sweet Home Mine, Colorado[END_REF][START_REF] Guy | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U/Pb dating of wolframite[END_REF], cassiterite [START_REF] Gulson | Cassiterite: potential for direct dating of mineral deposits and a precise age for the Bushveld complex gran-ites[END_REF][START_REF] Yuan | A precise U-Pb age on cassiterite from the Xianghualing tin-polymetallic deposit (Hunan, South China)[END_REF], and scheelite [START_REF] Wintzer | Eocene U/Pb scheelite LA-ICP-MS dates of stibnite-scheelite mineralization in the Yellow pine Au-Sb-W mining area, Central Idaho, USA[END_REF] or bastnaesite [START_REF] Ntiharirizwa | Geology and U-Th-Pb dating of the Gakara REE Deposit[END_REF].

The Axial Zone of the Pyrenees (France) comprises Paleozoic rocks affected by polyphased tectonometamorphic events during the Variscan and Alpine events [START_REF] Casas | On the role of the Hercynian and alpine thrusts in the upper Paleozoic rocks of the Central and Eastern Pyrenees[END_REF][START_REF] Vissers | Iberian plate kinematics and Alpine collision in the Pyrenees[END_REF][START_REF] Denèle | Timing of granite emplacement, crustal flow and gneiss dome formation in the Variscan segment of the Pyrenees[END_REF][START_REF] Cochelin | Structural inheritance in the Central Pyrenees: the Variscan to Alpine tectonometamorphic evolution of the Axial Zone[END_REF]). The area is known to host several tungsten and gold deposits and occurrences [START_REF] Derré | Relations chronologiques entre la mise en place du granite de Salau (Haute Vallée du Salat, Pyrénées ariégeoises) et les déformations du Paléozoïque de la région[END_REF][START_REF] Guy | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U/Pb dating of wolframite[END_REF]). Among these, the Salau deposit was the most important tungsten mine in France, with a production of 13,950 t WO3 between 1970 and[START_REF] Bodin | Nappes hercyniennes précoces à matériel dévonien hétéropique dans les Pyrénées ariégeoises[END_REF], with an exceptional high average grade of 1.5% WO3. The deposit is located at the contact between the la Fourque granodioritic intrusion and metacarbonate host rocks. The ore, traditionally considered as a scheelite skarn, has a complex mineralogy and morphology, affected by a late "hydrothermal alteration" [START_REF] Fonteilles | The scheelite skarn de-posit of Salau (Ariège, French Pyrenees)[END_REF]. Similar skarn occurrences exist in the vicinity of Salau, such as Aurenere, in Spain (Fig. 1).

In addition to scheelite, the Salau deposit also contains gold in economic concentrations (1-10 g/t; [START_REF] Guiraudie | Le gisement de Salau (Ariège), résultats généraux de la recherche[END_REF][START_REF] Fonteilles | The scheelite skarn de-posit of Salau (Ariège, French Pyrenees)[END_REF]). However, the ore-forming processes and the paragenetic position of gold remain unclear. Some authors considered that sulfides, related to the late "hydrothermal alteration," are the retrograde stage of the scheelite skarn formation [START_REF] Fonteilles | Ore controls for the Salau Scheelite deposit (Ariège, France): evolution of ideas and present state of knowledge[END_REF]. Other studies interpreted these sulfides as the expression of a shear zone mineralization without a genetic link with the La Fourque intrusion [START_REF] Ledru | Relationships between fluid circulation, ore deposition and shear zones: new evidence from the Salau scheelite deposit[END_REF]. This results, in part, from the fact that neither the emplacement age of the intrusive rocks nor metal deposition has been dated. The age of intrusion and skarn is interpreted to be late Variscan [START_REF] Derré | Relations chronologiques entre la mise en place du granite de Salau (Haute Vallée du Salat, Pyrénées ariégeoises) et les déformations du Paléozoïque de la région[END_REF]. Similarly, deformation along the shear zone is the latest deformation event in the deposit [START_REF] Kaelin | Analyse structurale du gisement de scheelite de Salau (Ariège, France)[END_REF].

The aim of this paper is to constrain the timing and the origin of high-grade W/Au mineralization during the late-orogenic evolution of the Axial Zone of the Pyrenees. The Salau deposit and Aurenere occurrence were studied in order to characterize mineralization using field, petrography, SEM imagery, whole rock, and mineral geochemistry (apatite, scheelite). In addition, LA-ICP-MS U/Pb in situ dating on zircon, apatite, and scheelite was performed to constrain ages of emplacement of the intru-sive rocks or of mineralizing event(s).

Geological background

Regional geology

The Pyrenees are an east-west trending Alpine orogenic segment located between France and Spain. The Axial Zone of the Pyrenees is a segment of the southern external zone of the 2011). b Regional structural scheme of the Salau area modified from [START_REF] Colchen | Carte géol[END_REF] Variscan belt, which has structured the whole western Europe at the end of the Paleozoic, mostly during the Pennsylvanian [START_REF] Garcia-Sansegundo | Hinterland-foreland zonation of the Variscan orogen in the Central Pyrenees: comparison with the northern part of the Iberian Variscan Massif[END_REF]. Ediacarian to Paleozoic metasedimentary and plutonic rocks related to the Variscan orogeny crop out in the Axial Zone (Fig. 1). A strong structural contrast exists in the Axial Zone between middle crust rocks with flat-lying foliation and the upper crust rocks with a steeply dipping schistosity [START_REF] Carreras | Tectonics levels in the Palaeozoic basement of the Pyrenees: a review and a new interpretation[END_REF]Denèle et al. 2009a;[START_REF] Cochelin | Structural inheritance in the Central Pyrenees: the Variscan to Alpine tectonometamorphic evolution of the Axial Zone[END_REF]. Four major successive deforma-tion events have been documented (Denèle et al. 2009a;[START_REF] Laumonier | Polymétamorphisme et évolution crustale dans les Pyrénées orientales pendant l'orogenèse varisque au Carbonifère supérieur[END_REF][START_REF] Denèle | Timing of granite emplacement, crustal flow and gneiss dome formation in the Variscan segment of the Pyrenees[END_REF][START_REF] Cochelin | Structural inheritance in the Central Pyrenees: the Variscan to Alpine tectonometamorphic evolution of the Axial Zone[END_REF]. The first stage is of crustal thickening during N-S to NE-SW compressive tectonics, responsible for fold-thrust belt development in the upper crust (323-310 Ma; [START_REF] Bodin | Nappes hercyniennes précoces à matériel dévonien hétéropique dans les Pyrénées ariégeoises[END_REF]). The second stage is localized in the middle crust . This is a crustal-scale stage of syn-convergence and horizontal lateral flow of the middle crust contemporaneous with the HT/LP metamorphic peak and partial melting [START_REF] Vilà | LPHT metamorphism in a late orogenic transpressional setting, Albera Massif, NE Iberia: implica-tions for the geodynamic evolution of the Variscan Pyrenees[END_REF]. The third stage corresponds to deformation in reversedextral shear zones during cooling of the Variscan crust as exemplified by the Merens shear zone [START_REF] Denèle | Progressive deformation of a zone of magma transfer in a transpressional regime: The Variscan Mérens shear zone (Pyrenees, France)[END_REF]. The activity of the shear zone has never been dated using robust methods. The latest stages of deformation are marked by a strong heat anomaly at the bottom of the upper crust between ca. 305 to 285 Ma [START_REF] Romer | U-Pb age and lead isotope characterization of Au-bearing skarn related to Andorra granite (Pyrenees, Spain)[END_REF][START_REF] Aguilar | Late Variscan metamorphic and magmatic evolution in the eastern Pyrenees revealed by U-Pb age zircon dating[END_REF]. The emplacement of calc-alkaline and more evolved plutons is responsible for contact metamorphism, locally accompanied by skarn formation [START_REF] Autran | Relations entre les intrusions de granitoïdes, l'anatexie et le métamorphisme régional, considérées principalement du point de vue du rôle de l'eau: cas de la chaine hercynienne des Pyrénées orientales[END_REF][START_REF] Fonteilles | The scheelite skarn de-posit of Salau (Ariège, French Pyrenees)[END_REF][START_REF] Soler | Gold-bearing hédenbergite skarnsfrom the SW contact of the Andorra granite (central Pyrenees, Spain)[END_REF][START_REF] Cardellach | The origin of fluids involved in the formation of gold-bearing skarns of the Andorra granite (central Pyrenees, Spain); sulphur isotope data[END_REF][START_REF] Ayora | Strata-bound As-Au mineralization in pre-Caradocian rocks from the Vall de Ribes, eastern Pyrenees, Spain[END_REF][START_REF] Barnolas | Synthèse géologique et géophysique des Pyrénées Edition BRGM -ITGE[END_REF]. Several scheelite occurrences lo-cated in Devonian carbonate formations of the Axial Zone are known, for example in Salau, Aurenere, Costabonne, or les Tourrettes (Fig. 1).

Local geology

Stratigraphy and tectonometamorphic evolution of the wall-rocks

In the Salau/Aurenere district, the Paleozoic stratigraphic suc-cession forms a large-scale monocline (Charuau and Derré 1976;[START_REF] Derré | Le gisement de scheelite de Salau, (Ariège, Pyrénées). 26ème CGI Gisements français[END_REF]Fig. 1). From bottom to top, the following stratigraphic units are defined:

The Mont Rouch Formation (Early to Middle Ordovician) is a flysch complex reaching up to 2 km in thickness. It is followed by a monotonous series of graphitic and pyritic Silurian shales known to act regionally as a thrusting level underneath the more competent Devonian rocks. To the north, the Salau Formation comprises various carbonate and pelite intercalations. It consists of a lower member of graphitic lime-stones followed by centimetric alternations of siltstone and limestone beds. Near the top of the Salau Formation, the mas-sive gray limestones occur. The top of the Salau Formation consists of bluish shales.

Three main tectonic stages of deformation have been distinguished in the study area [START_REF] Derré | Le gisement de scheelite de Salau, (Ariège, Pyrénées). 26ème CGI Gisements français[END_REF], which correspond well with the regional tectonic evolution [START_REF] Denèle | Timing of granite emplacement, crustal flow and gneiss dome formation in the Variscan segment of the Pyrenees[END_REF][START_REF] Cochelin | Structural inheritance in the Central Pyrenees: the Variscan to Alpine tectonometamorphic evolution of the Axial Zone[END_REF]. The first stage of defor-mation (D1) involved a top-to-the-SE shear deformation re-sponsible for the development of recumbent isoclinal P1 folds of all dimensions whose axes have a consistent N45°E direction. These folds, which partially transpose the compositional layering, are associated with the development of a crenulation cleavage and a subhorizontal schistosity S1 [START_REF] Déramond | Tectoniques superposées dans le Paléozoïque du Haut-Salat (Pyrénées Ariégeoises)[END_REF][START_REF] Charuau | Relation entre les concentrations plombo-zincifères et la tectonique superposée du district de Hoque-Saubé-Carboire (Pyrénées ariégeoises). Thèse 3 e cycle Paris VI Charuau D, Derré C[END_REF][START_REF] Derré | Le gisement de scheelite de Salau (Ariège, France)[END_REF][START_REF] Colchen | Carte géol[END_REF][START_REF] Denèle | Timing of granite emplacement, crustal flow and gneiss dome formation in the Variscan segment of the Pyrenees[END_REF][START_REF] Cochelin | Structural inheritance in the Central Pyrenees: the Variscan to Alpine tectonometamorphic evolution of the Axial Zone[END_REF]. The D2 deformation stage resulted in the formation of sub-vertical folds associated with epizonal regional metamorphism (greenschist facies 300-350 °C). P2 folds are isoclinal, hectometric in size, and overturned towards the North. Fold axis have a N110°E-N120°E direction. They are ac-companied by a crenulation cleavage S2 parallel to their axial planes. The axial plane foliation (S2) is marked by muscovite and chlorite. This stage (D2) is also marked by the emplacement of the granodioritic apex, accompanied by contact metamorphism. The final D3 deformation stage is represented by large E-W (N80 to N120°E), steeply dipping (60 to 80°N), ductile shear zones and other brittle faults at the contact between the la Fourque granodiorite and the carbonate host rocks. These dextral reverse faults with a displacement of more than 200 m (Fig. 2; [START_REF] Lecouffe | Les épisodes de fracturation dans le gisement de schee-lite de Salau (Ariège), Caractères géométriques et pétrologiques, relation avec la minéralisation et implications minières[END_REF] are characterized by strain folds in marbles, C-S structures in the granodiorite, and breccias.

Intrusive rocks

The La Fourque granodiorite crops out at the bottom of the Salat valley (Fig. 1). Its shape is almost equidimensional occupying an area of about 1 km 2 . The morphology of the intrusive stock, established in an antiform, seems to be controlled by the regional structures defined by the thick carbon-ate formations surrounding it [START_REF] Derré | La province à Sn-W Ouest européenne. Histoire de divers types de gisements du massif Central, des Pyrénées et du Portugal. Distribution des gisements[END_REF]. [START_REF] Kaelin | Analyse structurale du gisement de scheelite de Salau (Ariège, France)[END_REF] and [START_REF] Soler | Pétrographie, thermochimie et métallogénie du gisement de scheelite de Salau (Pyrénées ariègeoises[END_REF] showed that the granodio-rite postdates the main foliation stage D2 [START_REF] Denèle | Timing of granite emplacement, crustal flow and gneiss dome formation in the Variscan segment of the Pyrenees[END_REF]. The mylonites at the contact with carbonate country rocks are related to a more recent ductile-brittle or brittle deformation [START_REF] Fonteilles | Ore controls for the Salau Scheelite deposit (Ariège, France): evolution of ideas and present state of knowledge[END_REF].

Three main types of intrusive rocks can be distinguished in the vicinity of the Salau deposit: the apical marginal facies of the La Fourque granodiorite, a porphyritic facies in the centre of the intrusion, and aphanitic dykes or sills distinguished on the basis of their grain size, chemical, and mineralogical compositions [START_REF] Toulhoat | Pétrographie et géochimie des isotopes stables[END_REF][START_REF] Guy | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U/Pb dating of wolframite[END_REF]; ESM 1 Fig. 1). The marginal facies is a relatively dark, fine-grained granodiorite with an equigranular texture (0.5-1 mm) 100 to 250 m thick. It becomes thinner at depth where it disappears. This "apical granodiorite" is composed of interstitial crystalline quartz, plagioclase (An 20-60), rare microcline, abundant biotite, and accessory minerals (zircon, apatite). The chemical composition of the marginal facies corresponds to a granodiorite with a low K2O content (2.6 wt%) compared to other granitoids in the upper Pyrenean massifs. The porphyritic facies in the center of the massif is a diorite-monzogranite, rich in potassium feldspar (20%) with higher K20 (4.6 wt%). The two petrographic types belong to two different geochemical lineages [START_REF] Raimbault | Pétrographie et géochimie de la granodiortite de la Fourque (gisement de scheelite de Salau, Pyrénées, France)[END_REF]. Different types of aphanitic sills and dykes are observed. Microdioritic dykes are cut by the apical granodiorite which contain dark microdiorite enclaves [START_REF] Fonteilles | The scheelite skarn de-posit of Salau (Ariège, French Pyrenees)[END_REF]. Aplite dykes cut both the La Fourque intrusive rocks and the marbles. They are commonly epidotized on the southern side of the La Fourque granodiorite.

The Aurenere W/Au occurrence crops out at 5 km to the West of the Salau deposit. The occurrence is also located at the contact between a granodioritic stock and Devonian marbles that are skarnified and mineralized over ca.100 m 2 (Fig. 1). The bulk chemical composition of the granodiorite stock is similar to that of La Fourque (ESM 1 Fig. 1), but, due to the erosion level, only the marginal facies is observed in the field. At its contact, the marbles are skarnified.

Mineralization styles

The first tungsten-bearing skarn was discovered in 1951, in contact with calc-alkaline intrusions at Costabonne in the Axial Zone of the Pyrenees [START_REF] Guy | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U/Pb dating of wolframite[END_REF]). The Salau deposit was discovered by in 1959, during regional tungsten exploration [START_REF] Guiraudie | Campagne de prospection en 1960 sur les calcaires du Caradoc de l'Ariège[END_REF].

The deposit was estimated to contain 20,000 t of WO3 from 1.3 Mt of ore at 1.5% WO3 using a cutoff grade of 0.8 wt% WO3 [START_REF] Fonteilles | The scheelite skarn de-posit of Salau (Ariège, French Pyrenees)[END_REF]). The orebodies located on the southern margin of the La Fourque granodioritic intrusion [START_REF] Derré | Le gisement de scheelite de Salau, (Ariège, Pyrénées). 26ème CGI Gisements français[END_REF] were mined between 1970 and 1986 [START_REF] Lecouffe | Les épisodes de fracturation dans le gisement de schee-lite de Salau (Ariège), Caractères géométriques et pétrologiques, relation avec la minéralisation et implications minières[END_REF]. The deposit was historically described as a scheelite skarn due to the presence of calcic silicates (grossular, hedenbergite) and because of its close spatial association with an intrusion. The deposit comprises two main orebodies, the Bois d'Anglade and the Veronique fault [START_REF] Fonteilles | The scheelite skarn de-posit of Salau (Ariège, French Pyrenees)[END_REF]). The Bois d'Anglade orebody is subdivided in three, named "Formation Nord," "Golfe," and "Formation Sud" (Fig. 2).

Two types of skarn were described at the Salau deposit [START_REF] Derré | La province à Sn-W Ouest européenne. Histoire de divers types de gisements du massif Central, des Pyrénées et du Portugal. Distribution des gisements[END_REF]). The first is massive and resulted from the transformation of the lower graphitic marbles or the upper marbles. It is often characterized by an almost monomineralic gangue mineralogy of either garnet or pyroxene. This first skarn does not carry significant tungsten mineralization. In contrast, the second skarn formed by metasomatism of calcic hornfels consists of alternating garnet-, pyroxene-, epidote-, and titanite-rich bands. These banded zones are inherited from the pre-existing sedimentary bedding.

A massive sulfide body of pyrrhotite, chalcopyrite, and sphalerite of 500 m × 250 m and 5 m thick is spatially associated to the Veronique Fault at the southern contact of the granodiorite with the country rocks. It is considered as part of the retrograde stage of the skarn [START_REF] Fonteilles | The scheelite skarn de-posit of Salau (Ariège, French Pyrenees)[END_REF]).

Mineralization at the Aurenere W/Au occurrence is similar to the Salau deposit. A grossular-hedenbergite-wollastonite skarn was formed during the prograde stage, whereas low contents of scheelite and disseminated sulfides (pyrrhotite, arsenopyrite) were developed during the retrograde stage. Late quartz veins cut skarn mineralization and contain coarsegrained scheelite and a massive arsenopyrite, pyrrho-tite, chalcopyrite, sphalerite, and electrum [START_REF] Palau I Ramirez | Gold-bearing metasomatic bodies related to the Hercynian plutonism in the Marimanya area[END_REF][START_REF] Palau I Ramirez | Dating of gold-bearing skarns and intragranitic mineralizations in the Central Pyrenees. A new approach to thematic mapping[END_REF][START_REF] Palau I Ramirez | El magmatisme calcoalcali del massis de Marimanya i les mineralitzacions As-Au-W associades[END_REF].

Field observations and mineralogy

The Bois d'Anglade orebody is crosscut by the Veronique Fault along its southern edge (Fig. 3a). The Bois d'Anglade orebody displays a comb shape located in an embayment of the Salau granodiorite. The bedding of Devonian-aged metasedimentary host rocks (N80E 80°N) is perpendicular to the contact with the intrusion in the embayment.

The Formation Nord and the Golfe orebodies consist of skarn (Fig. 3b) containing fine-grained scheelite. The prograde stage of skarn consists of a grossular, hedenbergite, and fine-grained scheelite (< 50 μm) assemblage (Fig. 4a). During the retrograde stage, garnet was replaced by epidote, whereas hedenbergite was replaced by amphibole, accompanied by the deposition of disseminated arsenopyrite and pyrrhotite (Fig. 4f). The proximal zone (up to 30 m from the intrusion) consists of garnet, pyroxene, and scheelite. The distal zone is characterized by a wollastonitebearing assemblage. In this zone, the scheelite size is mostly finegrained and less abundant.

In contrast, the Formation Sud orebody located along the strike of the Veronique Fault, which intersects the contact between the granodiorite and the marble (Fig. 3d), consists mainly of massive sulfides without skarn (Fig. 3c). Along the strike of the fault, the granodiorite is altered (albitized and chloritized) and brecciated with mylonitic clasts (Fig. 3e). The massive sulfides hosted by the Veronique Fault con-sist of coarse-grained scheelite, euhedral apatite, massive pyr-rhotite, arsenopyrite, chalcopyrite, sphalerite, native bismuth, electrum (80% Au, 20% Ag), laitakarite, and tetrahedrite (Fig. 4b). Scheelite is coarse-grained (0.2-1 cm) with poikilitic crystals cut by late sulfides (Fig. 4c). Arsenopyrite was the first mineral to appear in this assemblage. It is frac-tured and filled by late pyrrhotite, chalcopyrite, and sphalerite accompanied by the crystallization of euhedral apatite, native bismuth, electrum, laitakarite, and tetrahedrite (Fig. 4e). Apatite grains are euhedral and unaltered. (Fig. 4h). Then, late veins of quartz, scheelite, calcite, and powdery chlorite cut the sulfides and represent the last stage of ore formation.

In the Formation Nord and Golfe orebodies, similar massive sulfides form lenses or clusters in the garnet and pyroxene skarn along the bedding of the country rocks or near the contact with the granodiorite. Strain folds, C-S structures and sigma clasts in skarn, cemented by massive sulfides along Fig. 3 Field photographs showing the following: a general view of La Fourque intrusion with late faults; b sample of calcic hornfels skarnified in an embayment with comb teeth texture; c sample of deformed lower marble collected along the Veronique Fault with massive sulfides; d drag folds developed in the lower marble along the Veronique fault at contact with the La Fourque granodiorite; e altered granodiorite breccia along the Veronique Fault, cemented by massive sulfides and coarse-grained scheelite; f C-S structures in sheared skarn along the Veronique shear zone showing an east-west direction and a reverse movement; g sigma structure of skarn in the Veronique Fault showing an east-west direction and a reverse movement; h La Fourque granodiorite cut and altered by tourmaline veinlet and decimetric aplite dykes cutting the altered granodiorite the contact between the fault and the granodiorite indicate dextral reverse kinematics (Fig. 3f,g). Aplitic dykes are locally spatially associated with the massive sulfide mineralization and crosscut the La Fourque granodiorite and the scheelite skarn (Fig. 3h). In some places, tourmaline veins, spatially related to massive sulfides, cut and alter the granodiorite (Fig. 3h; [START_REF] Lecouffe | Les épisodes de fracturation dans le gisement de schee-lite de Salau (Ariège), Caractères géométriques et pétrologiques, relation avec la minéralisation et implications minières[END_REF]. The skarn ore is intersected and displaced with a reverse kinematic at the contact with ductile, quartzbearing, N90E 70°N faults. All around the La Fourque stock, sulfides are disseminated in hydrothermally altered granodiorite. All these features indicate that the massive sulfides formed after the la Fourque intrusion (Fig. 5).

Cathodoluminescence imaging

Cathodoluminescence imaging (Tescan, BRGM Orleans) was realized on selected zircon, apatite, and scheelite grains in order to detect inherited cores or zoning. Zircon grains from the Salau and Aurenere granodiorite do not show inherited cores (ESM 1 Fig. 2a, c and e; Fig. 5), with the exception of two grains (sample TP709 and TP728, ESM 1 Fig. 2b and2d). Magmatic apatite is poikilitic and altered as droplets with growth zoning (TP 130, TP 608 and TP728, ESM 1 Fig. 3c andd). Hydrothermal apatite is euhedral, unaltered, sometimes with complex zoning, and con-trast difference between core and rim (FT19, TP061, and TP 738; ESM 1 Fig. 3a andb). However, given its rhythmic aspect perpendicular to the rim, this contrast difference does not correspond to the presence of an inherited core but rather to compositional changes during the growth of the crystals. Finally, scheelite grains show growth zones without any evidence for inheritance (ESM 1 Fig. 4a,b,c; Fig. 9d).

Mineral chemistry of scheelite and apatite

Materials and methods

Fifty scheelite and 21 apatite grains were selected on thin and polished sections from 8 samples from the intrusive rocks and the two different types of mineralization. The location of the samples is given on Fig. 2. The data set is given in ESM 2 Tables 1 and2.

LA-ICP-MS analyses were performed at Brest University (France) in order to obtain REE data for scheelite and apatite as well as Mo and W contents in scheelite, using a Geolas 193nm Excimer Laser coupled to a Thermo Element II ICP-MS. Analytical conditions for the laser include a frequency of 10 Hz, a fluence of 6 J/cm

Results

Early fine-grained scheelite has a higher content in Mo (75-240 ppm) than the late coarse-grained scheelite (0-70 ppm; Fig. 6).

Magmatic apatite shows a relatively flat REE pattern with a prominent negative Europium anomaly (Fig. 7a) with Eu/Eu* and Ce/Ce* values ranging from 0.03 to 0.08 and 0.88 to 1.03, respectively (Fig. 8a). A similar REE distribution is observed for fine-grained scheelite from Salau and Aurenere, with a large negative Europium anomaly (Fig. 7b,c). Eu/Eu* and Ce/Ce* ratios yield similar values ranging between 0.06-0.14 and 0.89-1.07 for Salau and 0.4-0.55 and 0.76-0.87 for Aurenere, respectively (Fig. 8a)

Hydrothermal apatite crystals, which are texturally cogenetic with the massive sulfides, show two types of REE patterns, correlated with inner textures of the grains. Core of grains (ESM 1 Fig. 3a andb) are enriched in light REE, depleted in heavy REE with a moderate negative Europium anomaly (Fig. 7d). Rims of the same apatite grains (ESM 1 Fig. 3a andb) are also enriched in light REE and depleted in heavy REE but present a positive Europium anomaly (Fig. 7d). Eu/Eu* and Ce/Ce* returned values of 0.22-6.4 and 0.74-1.05, respectively (Fig. 8a) and therefore plot out of the domain of magmatic apatite.

Coarse-grained scheelite from massive sulfides contemporaneous of hydrothermal apatite presents an enrichment in light REE (except La and Ce) and a depletion in heavy REE with small or absent Eu anomalies (Fig. 7e). These scheelite grains yield very different Eu/Eu* ratios from hydrothermal apatite ranging from 0.6 up to 1.48 for Ce/Ce* showing low variation around 0.81-1.03 (Fig. 8b). Late scheelite crystals found in quartz-calcite-chlorite veins and have a REE chem-istry similar to the rims of the apatite grains in the massive Fig. 4 Thin section microphotographs illustrating the following: a disseminated pyrrhotite associated with fine-grained scheelite and grossular garnet in skarn bedding; b massive sulfides paragenesis with an assemblage of pyrrhotite-chalcopyrite-sphalerite crosscutting the coarse scheelite; c coarse-grained scheelite fragmented and cemented by massive pyrrhotite; d arsenopyrite crystals fragmented and cemented by chalcopyrite and massive pyrrhotite; e native bismuth-laitakarite-electrum assemblage typical of Salau gold paragenesis; f hedenbergite replaced by amphibole, intergrown with massive pyrrhotite; g back scattered electron image of fragmented magmatic apatite contemporaneous with biotite in La Fourque granodiorite; h contemporaneous of massive pyrrhotite and hydrothermal, euhedral apatite sulfide ores (Fig. 7f,g) with slightly higher Ce/Ce* ratios reaching ca. 0.9-1.15. Very coarse-grained scheelite has two REE patterns: one is similar to late scheelite, the other is enriched in LREE (Fig. 7g).

LA-ICP-MS U/Pb geochronology

Materials and methods

Zircon, apatite, and scheelite grains were selected from 12 samples issued from the intrusive rocks and the two different types of mineralization. The location of the samples is provided on Fig. 2. Raw data is given in ESM 2 Tables 3, 4, and5. Five fresh samples of igneous rocks were selected for U/Pb dating on zircon, three samples from the La Fourque intrusion (TP 754, TP 608, TP 610), and two samples from the Aurenere intrusion (TP 728, TP 709). Four samples were se-lected for U/Pb dating on apatite. One sample (TP 130) is magmatic apatite from the marginal facies of the La Fourque granodiorite. Three samples (TP 061, FT19, TP 738) are hy-drothermal apatite associated with coarse-grained and massive A classic mineral separation procedure was applied to concentrate the zircon grains using the facilities avail-able at ISTO laboratory. Rock samples were crushed, and the fractions with a particle size below 250 μm were processed further. Heavy minerals were concentrat-ed by heavy liquids from the size fraction. Magnetic minerals were then removed with an isodynamic Frantz magnetic separator. Zircon grains were carefully handpicked under a binocular microscope and embedded in epoxy mounts that were then polished. For apatite and scheelite, U/Pb dating was realized in context on regular thin sections. U/Pb geochronology was conduct-ed in situ by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) at Geosciences Rennes using an ESI NWR193UC Excimer laser coupled to an Agilent 7700x quadrupole ICP-MS equipped with a dual pumping system to enhance sensitivity [START_REF] Paquette | Sensitivity enhancement in LA-ICP-MS by N2 addition to carrier gas: application to radiometric dating of U-Th-bearing min-erals[END_REF]. The instrumental conditions are reported in ESM 2 Table 6. Additional information about the protocols used for U/Pb zircon dating can be found in [START_REF] Ballouard | Tectonic record, magmatic history and hydrother-mal alteration in the Hercynian Guérande leucogranite, Armorican Massif, France[END_REF], and in [START_REF] Pochon | U/Pb LA-ICP-MS dating of apatite in mafic rocks: evidence for a magmatic event at the Devonian-Carboniferous boundary in the Armorican Massif (France)[END_REF] for apatite. According to [START_REF] Horstwood | Community-derived standards for LA-ICP-MS U-(Th-)Pb geochronologyuncertainty propagation, age interpretation and data reporting[END_REF], uncertainties ob-tained for the reference material Plesovice were propa-gated to the analyzed zircon grains.

For U-Pb dating of scheelite, we followed the protocol of [START_REF] Wintzer | Eocene U/Pb scheelite LA-ICP-MS dates of stibnite-scheelite mineralization in the Yellow pine Au-Sb-W mining area, Central Idaho, USA[END_REF] and used the NIST 612 glass standard as our primary standard (see ESM 2 Table 6). For all the samples, results are plotted in Tera-Wasserburg diagrams using Isoplot/ Ex [START_REF] Ludwig | User's manual for a geochronological toolkit for Microsoft Excel[END_REF]. All errors are provided at 1σ level for zircon and 2σ level for apatite and scheelite.

Results

Zircon dating

Sample TP 754 is from the marginal facies at the SE edge of the La Fourque intrusion. Twenty-one zircon grains were an-alyzed (ESM 2 Table 3; Fig. 9a). Thirteen of these analyses are concordant (Fig. 9a) and define a concordia date of 295 ± 2.4 Ma (MSWD = 0.57). Five analyses either in zircon cores or in homogeneous grains define inherited apparent ages from older material around 325 and 350 Ma. Finally, 6 analyses are sub-concordant to discordant and are interpreted as reflecting the presence of a small amount of common Pb together with a slight Pb loss.

Sample TP 608 was collected in the porphyritic facies of the La Fourque intrusion. Eighteen zircon grains were analyzed (ESM 2 Table 3; Fig. 9b). Seven of these analyses (Fig. 9b) are concordant and yield a Concordia date of 296.9 ± 3.2 Ma (MSWD = 1.4) interpreted as the age of the intrusion. The remaining data are discordant at 280 Ma and attributed to Pb loss.

Sample TP 610 was collected on the northern side of the La Fourque intrusion from porphyritic facies. Twenty-four zircon grains were analyzed (ESM 2 Table 3; Fig. 9c). Fifteen analyses are concordant and yield a concordia date of 294.5 ± 2.2 Ma (MSWD = 0.81; Fig. 9c) interpreted as the emplace-ment age for this granodiorite. One concordant analysis yields an inherited apparent age from older material of ca. 320 Ma. Six analyses are discordant perhaps because of Pb loss and/or the presence of common Pb. In summary, all three samples from the La Fourque granodiorite yield concordant ages com-parable within error at ca 295 Ma.

TP 709 and TP 728 were sampled on the Aurenere granodioritic intrusion. For sample TP 709, nineteen analyses were performed (ESM 2 Table 3; Fig. 9d). Nine of them are con-cordant (Fig. 9d) and yield a Concordia age of 293.9 ± 2.8 Ma (MSWD = 0.29). Twelve discordant results show either older, inherited, apparent ages, or Pb loss. On sample TP 728, eigh-teen analyses are concordant and yield a Concordia age of 293.4 ± 2 Ma (MSWD = 1.13) (ESM 2 Table 3; Fig. 9e). Two analyses define older inherited apparent ages from older material at ca. 700 and 570 Ma while one analysis shows signs of Pb loss. Therefore, all these results agree for an emplace-ment age at ca. 295 Ma for the Aurenere intrusion, indistin-guishable from the emplacement age of the La Fourque intrusion.

Apatite dating

For sample TP 130, seventeen grains that were analyzed (ESM 2 Table 4) are discordant position (Fig. 10b) with a lower intercept of 297.3 ± 7.1 Ma (MSWD = 6.7). Hydrothermal apatite grains were collected in massive sulfides of the Golfe (TP 061), the Formation Sud (TP 738), and the Veronique Fault (FT19). All the apparent ages obtained on these apatites are similar within error (Fig. 10a,c,d

Discussion

In contrast to several skarn deposits worldwide, the Salau deposit has the particularity to host two different types of mineralization. The combination of field obser-vations with mineral chemistry and geochronology pro-vides insights to decipher the evolution stages of the mineralization.

Nature of the fluids

The mineral chemistry of scheelite and apatite provides evidence for mineral formation from different fluid sources. Higher Mo contents in the paragenetically early, skarnhosted scheelite (Fig. 6) are in a good agreement with observations made on other deposits, such as Los Santos (Timon [START_REF] Sanchez | Mineralogical and physiochemical evolution of the Los Santos scheelite skarn, Salamanca, NW Spain[END_REF], Mittersill [START_REF] Eichhorn | Implications of U-Pb SHRIMP zircon data on the age and evolution of the Felbertal tung-sten deposit (Tauern Window, Austria)[END_REF], Costabonne [START_REF] Raimbault | REE fractionation between scheelite and apatite in hydrothermal conditions[END_REF], or Eastern China [START_REF] Song | Scheelite elemental and isotopic signatures: implications for the genesis of skarn-type W-Mo deposits in the Chizhou Area, Anhui Province, Eastern China[END_REF][START_REF] Poulin | Assessing scheelite as an ore-deposit discriminator using its trace element and REE chemistry[END_REF]. The lower Mo contents found for the paragenetically late, coarse-grained, scheelite could suggest formation from a fluid depleted in Mo. REE data for cogenetic scheelite and apatite that provide further evidence for distinct mineralizing events [START_REF] Raimbault | REE fractionation between scheelite and apatite in hydrothermal conditions[END_REF] were two groups of REE patterns and are recog-nized for both scheelite and apatite, suggesting that two fluids are associated with mineralization. The first group of REE patterns is relatively flat, with a distinct negative Eu anomaly. Both the magmatic apatite of the La Fourque granodiorite (Fig. 7a) and fine-grained scheelite from the scheelite skarn (Fig. 7b) display these typical patterns for minerals derived from a magmatic source [START_REF] Raju | Scheelite geochemical signa-tures by LA-ICP-MS and potential for rare earth elements from Hutti Gold Mines and fingerprinting ore deposits[END_REF] which suggest they are linked here to the emplacement of the La Fourque grano-diorite into Devonian marbles.

The second group of REE patterns is marked by LREE enrichment and moderate to high Eu/Eu* anomalies. Hydrothermal apatite grains present in the massive sulfide ore display negative europium anomalies in the core (Fig. 7c) and positive anomalies in rims (Fig. 7c). Cathodoluminescence images show contrasted growth bands (ESM 1 Fig. 3a andb) and confirm the compositional nature of the observed zonation. These compositional changes reflect the chemical evolution of the hydrothermal fluid. Coarse-grained scheelite, also associated with massive sulfides, presents a similar REE pattern with a weak positive Eu anomaly, as the typical signature of hydrothermal system [START_REF] Lottermoser | Rare earth elements and hydrothermal ore formation processes[END_REF].

Figure 11 shows the distribution of the different scheelite generations in a ternary LREE-MREE-HREE (Light Rare Earth Element -Medium Rare Earth Element -Heavy Rare Earth Element) diagram [START_REF] Raju | Scheelite geochemical signa-tures by LA-ICP-MS and potential for rare earth elements from Hutti Gold Mines and fingerprinting ore deposits[END_REF]. The fine-grained scheelite has a strong enrichment in LREE and plots near the "skarn, porphyry W-Mo deposits" cluster, whereas scheelite from massive sulfides, enriched in both LREE This interpretation is corroborated by isotopic studies and fluid inclusion data [START_REF] Toulhoat | Pétrographie et géochimie des isotopes stables[END_REF][START_REF] Guy | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U/Pb dating of wolframite[END_REF] showing evidence for different stages of mineralization that coincide with a decrease in fluid temperature and evo-lution of hydrothermal fluid compositions. A first magmat-ic fluid, which contains H2O and NaCl [START_REF] Soler | Pétrographie, thermochimie et métallogénie du gisement de scheelite de Salau (Pyrénées ariègeoises[END_REF], is found in the skarn minerals (quartz, garnet, hedenbergite, and scheelite). After the skarn formation, a H2O-CO2-CH4 fluid was probably linked to the decarbonatation of the country rocks during metasomatism mixed with the mag-matic fluid to precipitate scheelite [START_REF] Krier-Schellen | Etude microthermométrique des inclusions fluides des différentes paragenèses du gisement de scheelite (tungstène) de Salau (Pyrénées Ariégeoises[END_REF]. The parameters for the skarn formation are estimated at 470 < T°C < 530, -9 < log fS2 < -6, -27.7 < log fO2 < -21.1 and P ≈ 2 kbar [START_REF] Soler | Pétrographie, thermochimie et métallogénie du gisement de scheelite de Salau (Pyrénées ariègeoises[END_REF]. For the massive sulfides, δ 34 S values have been interpreted as characteristic of a fluid with a magmatic origin [START_REF] Guy | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U/Pb dating of wolframite[END_REF][START_REF] Palau I Ramirez | El magmatisme calcoalcali del massis de Marimanya i les mineralitzacions As-Au-W associades[END_REF]. The parameters for the late massive sulfide miner-alization are estimated at 335 < T°C < 363, -9.51 < log fS2 < -8.45, -32.8 < log fO2 < -30.2 and 2.16 < P (kbar) < 2.58 [START_REF] Krier-Schellen | Etude microthermométrique des inclusions fluides des différentes paragenèses du gisement de scheelite (tungstène) de Salau (Pyrénées Ariégeoises[END_REF]. Absolute time constraints on the Salau/Aurenere W/Au deposit Direct in situ U/Pb geochronology on zircon, apatite, and scheelite yields distinct ages for the different stages of ore formation. Zircon and magmatic apatite dating yields an age of ca. 295 Ma, corresponding to the emplacement age of the La Fourque and Aurenere intrusions. The associat-ed massive skarns have the same age. Massive sulfide ores related to the Veronique Fault formed later, as sug-gested by an age of 289 ± 2 Ma for hydrothermal apatite. Coarsegrained scheelite from massive sulfide ore yields an age of 284 ± 11 Ma consistent with the hydrothermal apatite age. Using the emplacement age of the la Fourque intrusion at 295 ± 2 Ma (and related skarn) and 289 ± 2 Ma for the hydrothermal apatite associated with massive sulfides ore, it appears that these mineralizations are the result of two distinct metallogenic events separated by at least 2 Ma. This interpretation is in agreement with field relations (alteration features, tourmaline veins and brec-cias observed along the late shear zones), demonstrating that the deposition of the massive sulfide ore postdate granodiorite cooling (Fig. 3eg).

A model for the cooling of the La Fourque intrusion, computed using Darcy's law and convection/conduction in porous media for an intrusion, was emplaced at 2 kbar. A geothermal gradient of 40 °C/km was used for the mar-ble host rocks [START_REF] Cochelin | Structural inheritance in the Central Pyrenees: the Variscan to Alpine tectonometamorphic evolution of the Axial Zone[END_REF]) and an initial tem-perature of 900 °C for the granodiorite. The permeability of the marble is set at 1.10 -16 m 2 and that of the grano-diorite is 1.10 -19 m 2 . In this example, the la Fourque granodiorite intrusive body (1 km 2 ) cooled to geothermal gradient in less than ca. 40,000 years, comparable to other values of ca. 200,000 years [START_REF] Petford | Granite magma formation, transport and emplacement in the Earth's crust[END_REF][START_REF] Eldursi | Numerical investigation of transient hydrothermal processes around intrusions: heat-transfer and fluid-circulation controlled mineralization patterns[END_REF][START_REF] Chauvet | Geochronological and geochemical characterization of magmatic-hydrothermal events within the Southern Variscan external domain (Cévennes area, France)[END_REF][START_REF] Nabelek | The influence of temperature-dependant thermal diffusivity on the conductive cooling rates of plutons and temperature-time paths in contact aure-oles[END_REF][START_REF] Bucholz | Constraining the time scales of magmatic differentiation with U/Pb zircon geochronology[END_REF]. This implies that it cannot be the source for the coarse-grained scheelite, massive sulfide, and gold mineralization as they form at least 2 Ma after the intrusion had cooled.

At Salau, where massive sulfide mineralization within shear zone has a magmatic origin according to δ 34 S and fluid inclusions studies [START_REF] Toulhoat | Pétrographie et géochimie des isotopes stables[END_REF][START_REF] Guy | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U/Pb dating of wolframite[END_REF][START_REF] Krier-Schellen | Etude microthermométrique des inclusions fluides des différentes paragenèses du gisement de scheelite (tungstène) de Salau (Pyrénées Ariégeoises[END_REF], an igneous source other than La Fourque granodiorite is required. In Salau mine, evidence for possible intrusive bodies, younger than the La Fourque granodiorite, includes tourmaline veinlets and aplite veins (Fig. 3h). That could be derived from an evolved granite, emplaced deeper in the crust. This granitic stock could thus be considered as part of a long-lasting, multi-intrusion event that was emplaced during D3 deformation event and which was ultimately responsible for the schee-lite bearing massive sulfide ores. Such relationships be-tween different intrusive rocks were also observed in the nearby massifs of Marimanya (Palau i Ramirez 1998) and Cauterets [START_REF] Reyx | Relations entre tectonique, métamorphisme de contact et concentrations métalliques dans le secteur des anciennes mines d'Arre et d'Anglas (Hautes Pyrénées -Pyrénées atlantiques)[END_REF]. Similar observations were made at Hämmerlein [START_REF] Lefebvre | The Hämmerlein skarn-hosted polymetallic deposit and the Eibenstock granite associated greisen, western Erzgebirge, Germany: two phases of mineralization -two Sn sources[END_REF] or Los Santos in Spain (Timon [START_REF] Sanchez | Mineralogical and physiochemical evolution of the Los Santos scheelite skarn, Salamanca, NW Spain[END_REF], where different granites were emplaced within a time gap of ca. 10 Ma. Throughout the Variscan Orogen, other examples of sul-fide mineralization, consecutive to an early, mostly tungsten-rich mineralization, were described, such as Puy les Vignes [START_REF] Guy | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U/Pb dating of wolframite[END_REF] and Panasqueira [START_REF] Codeço | Chemical and boron isotopic composition of hydrothermal tourmaline from the Panasqueira W-Sn-Cu deposit[END_REF].

Concluding remarks

The Salau deposit is the expression of regional deforma-tion and magmatism in the axial zone of the Pyrenees during the late Variscan evolution (Fig. 12). The La Fourque granodiorite was emplaced at ca. 295 Ma contemporaneously to D2 event, in compressional regime in-to the upper crust at ca. 2 kbar. The intrusion is associated with contact metamorphism and the formation of skarns along the intrusive contact. This event corresponds to a period where the upper crust of the Axial Zone was ab-normally warm and the N-S compressive tectonic regime was marked by hectometric E-W trending folds. Later, at ca. 289 Ma with crust cooling, the deformation regime changed and was localized in shear zones along previous-ly emplaced granitic stocks and gneiss domes. As a con-sequence, shear zones were developed at their contact with host rocks or within graphitic metasedimentary beds. The Salau deposit consists of two types of mineralization. The first is a skarn with garnet, pyroxene, and finegrained scheelite mineralization with disseminated arsenopyrite and pyrrhotite. The second type, a breccia, consists of a coarse-grained scheelite with abundant massive sul-fide mineralization (arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, sulfosalts, native bismuth, and electrum) locat-ed in a major fault. The skarn is related to the La Fourque granodiorite emplacement at ca. 295 Ma (zircon and magmatic apatite). The massive sulfides ore is related to a reverse dextral, E-W trending Veronique Fault developed at ca. 289 Ma (hydrothermal apatite and coarse-grained scheelite). This age result is the first direct dating of the D3 Variscan deformation event. This interpretation is corroborated by isotopic and fluid inclusion data, indicating that the massive sulfides and scheelite mineralization were formed by a buried younger intrusion.

At a larger scale, this study points out that magmatism and hydrothermal events are phenomena which take place on relatively short timescales, generally between ca. 10 4 to 10 6 years.

Nevertheless, these events can be the expression of the regional evolution typically in late-orogenic stage,

Fig. 1 a

 1 Fig. 1 a Simplified geological map of the Paleozoic domain in the Pyrenees (southern France) modified from Denèle et al. (2011). b Regional structural scheme of the Salau area modified from[START_REF] Colchen | Carte géol[END_REF]

  v,c,an -Pyritic schists .. Cross secuo (fi mtruSJons 92 ± 13 Ma Il ig. 4)

Fig. 2

 2 Fig.2North-south cross section of the La Fourque massif as constrained by field observations and drill hole data. Location of studied samples in blue. Note that metamorphic isograds cross the fold structure, which precedes the La Fourque granodioritic intrusion emplaced into a large-

Fig. 5

 5 Fig. 5 Paragenetic sequence of the Salau W/Au-Cu deposit. Three main stages are distinguished, the scheelite skarn, the massive sulfide ore, and late alteration

Fig. 6

 6 Fig. 6 Diagram of molybdenum grade (ppm) vs tungsten content (%) in function of different scheelite types analyzed by LA-ICPMS. Finegrained scheelite shows higher molybdenum content (80-250 ppm) than coarse-grained scheelite (5-80 ppm) for the Salau deposit

Fig. 7

 7 Fig. 7 Comparison of REE spectra for different apatites and scheelites analyzed by LA-ICPMS. Magmatic apatite from Salau and fine-grained scheelite from Salau and Aurenere shows a similar relatively flat REE pattern with a strong negative europium anomaly (a-c). Hydrothermal

  ) if discordia are forced to a common Pb composition of 207 Pb/ 206 Pb = 0.870 obtained on galena from the massive sulfide mineralization (Marcoux and Moëlo 1991; Chew et al. 2014; Cochrane et al. 2014): TP 061 yields an age of 278 ± 9.7 Ma (N = 17; MSWD = 0.25), TP 738 gives a date of 287 ± 4.6 Ma (N = 15; MSWD = 3.2), and FT19 yields a date of 288.2 ± 3.4 Ma (N = 16; MSWD = 21). If all these data are plotted together in the same Tera-Wasserburg diagram

Fig. 8

 8 Fig.8Ce/Ce* vs Eu/Eu* anomalies diagram for apatite (a) and scheelite (b), adapted from[START_REF] Mao | Apatite trace element compositions: a robust new tool for mineral explora-tion[END_REF]. Anomaly values were calculated using Eu/ Eu* = EuCN/(SmCN•GdCN) 0.5 and Ce/Ce* = CeCN/(LaCN•PrCN )0.5[START_REF] Worrall | The development of acidic groundwaters in coal-bearing strata; part I, rare earth element fingerprinting[END_REF]. CN: normalized data to chondrite[START_REF] Mcdonough | The composition of the Earth[END_REF]

Fig. 9 Fig. 10

 910 Fig. 9 Tera-Wasserburg concordia diagrams for zircon. a-b-c Salau granodiorite. d, e Aurenere granodiorite. f Pleso reference sample. N corresponds to the number of zircon grains that have been analyzed per sample. Ellipses and errors are reported at 2σ

Fig. 11

 11 Fig. 11 LREE-MREE-HREE ternary diagram for the Salau and Aurenere scheelite analyzed by LA-ICPMS. (LREE = La + Ce + Pr + Nd, MREE = Sm + Eu + Gd + Tb + Dy, HREE = Ho + Er + Tm + Yb + Lu ; from Raju

Fig. 12

 12 Fig. 12 Chronology of the Salau deposit genesis. a D1 corresponds to early folding N30°E. b D2 at ca. 295 Ma corresponds to the N-S com-pressional stage which led to N110°E folds formation, granodiorite intru-sion and related scheelite skarn genesis. c Finally, D3 at ca. 289 Ma, a late evolved granite intrusion and the localization of deformation in shear zones during progressive cooling of the crust led to the formation of a scheelite, massive sulfides, and gold mineralization

  La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

					100
		100		conten t
		10		REE		10
		1	La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu		1	La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
		1000	Aurenere scheelite (TP726a)		10000	Hydrothermal apatite (FT19, TP738, TP061)
				c			d
		100		(CN)	1000
				conten t	100
		10		REE
						10
							core
		1	La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu		1 La Ce Pr Nd Sm Eu Gd Tb Dy Ho	rim Er Tm Yb Lu
		1000	Coarse-grained scheelite (250p, SC1)	e	1000	Late scheelite (156p)	f
		100		(CN)	100
				content
		10		RE	E	10
				250p
				SC1
		1	La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu		1	La Ce Pr Nd Sm Eu Gd Tb Dy Ho	Er Tm Yb Lu
		1000	Very coarse scheelite (211p)	g
	(CN)	100
	content	10
	REE	1
		0,1

Acknowledgments This investigation was supported by the society e-Mines through its R&D activity and the ISTO. The authors thank the following persons for their support on the field: F. Carbalido, F. Cheval-Garabedian, Q. Monge, J.L. Carbalido, and M. Bonnemaison. C. Derré, P. d'Arco, A.S. Audion, M. Picault, J. Gouin, G. Raoult, and B. Cochelin are thanked for their technical support including the provision of samples and valuable advice. I. Di Carlo (ISTO) is acknowledged for the MEB cathodoluminescence and microprobe analytical analyses. We particularly thank S. Janiec, G. Badin, and P. Benoist from ISTO laboratory for the thin sections and rock-crushing preparations. We also address our thanks to the IUEM (Brest) for LA-ICP-MS analyses. Finally, we would like to acknowledge the editor in chief G. Beaudoin, the associate editor J. Gutzmer, and two anonymous reviewers for their careful reading of this article and constructive remarks.

Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.