In collision belts, the upper plate is generally less deformed than the lower one that underwent syn-metamorphic ductile shearing, and frequently late-collisional crustal melting. Concerning the Variscan orogeny, it is widely accepted that the Armorica microcontinent represented the upper plate of the collision system. In France, the Central-North-Armorican Domain belonged to this upper plate whose southern margin in the Pontivy–Coray area exposes metamorphic rocks. There, structural and metamorphic studies indicate that an early tectono-metamorphic event (M0-M1) with biotite–garnet–staurolite–kyanite assemblage, crystallized at 0.9 GPa and 500 °C, is characterized by a top-to-the NW shearing. This event was followed by an HT event (M2) at ca 800–900 °C, coeval with a domal structure. In micaschists, monazite yields an LA-ICP-MS age at 351 Ma ascribed to M2. M0-M1-M2 events developed before the Late Carboniferous pluton emplacement at ca 315 Ma (M3 event). The tectono-metamorphic succession documents that Armorica was not a rigid block but underwent a synmetamortphic ductile deformation during the Famennian–Tournaisian (360–355 Ma) collision redefined here as the late episode of the “Bretonian orogenic phase”, whereas the pre-Famennian Bretonnian episode is ascribed to oceanic subduction. These new data allow us to reassess the geodynamic evolution of this part of the Variscan orogen.

In the French Armorican Massif, La Lucette is the most important late Variscan Sb deposit with an uncommon SbAu-(W) ore. Detailed mineralogical investigations, fluid inclusion study in gangue and ore combined with in-situ apatite LA-ICP-MS U/Pb dating were carried out to decipher the Sb-Au-W relationships, and metallogenic processes. The mineralization consists of sigmoidal quartz lenses. Four stages of ore deposition have been identified, consisting in the following mineral assemblages: i) scheelite, ii) arsenopyrite, pyrite, iii) base-metals and iv) stibnite-Au. An initial aqueous-carbonic hot-fluid (350 to 25 degrees C) from a metamorphic source is involved for the early scheelite to base-metals stages, and fluid/rock interaction could be responsible for the scheelite crystallization. Cooling and mixing of the initial fluid with an aqueous cold meteoric fluid (similar to 200 to 130 degrees C), are key factors for the late Sb-Au ore-deposition. P-T conditions express a shallow emplacement level (3.5 to 6 km) in a single and progressive crystallization-deformation event. No significant exhumation, and no additional magmatic source from late Variscan felsic or early Carboniferous mafic magmatic events are needed for the Sb-Au-(W) ore genesis. Structural features and new LA-ICP-MS U/Pb apatite dating associated with a regional synthesis show that all major Sb-Au mineralizations of the Armorican Massif, and most from the European Variscan Belt districts have a relatively similar genetic model. In the French Variscan massifs those deposits have been emplaced during the same mineralizing peak, which operated at around 310-295 Ma, and was controlled by the late-orogenic Variscan post-thickening tectonic event.

AbstractTennantite-(Cu), Cu12As4S13, was approved as a new mineral species from the Layo epithermal deposit, Castilla Province, Arequipa Department, Peru, where it occurs as black metallic anhedral grains, up to 0.1 mm across, replacing enargite and associated with chalcopyrite and vinciennite. In reflected light, tennantite-(Cu) is isotropic, grey with a bluish shade. Reflectance data for the four COM wavelengths in air are [λ (nm): R (%)]: 470: 29.1; 546: 28.4; 589: 27.4; and 650: 25.0. Electron microprobe analysis for holotype material gave (in wt.% – average of 10 spot analyses): Cu 49.32(27), Fe 2.20(12), Zn 0.09(2), Sn 0.03(5), As 19.45(43), Sb 1.94(10), Te 0.02(5), S 27.75(43), total 100.80(20). On the basis of (As + Sb + Te) = 4 atoms per formula unit (apfu), the empirical formula of tennantite-(Cu) is (Cu11.27Fe0.57Zn0.02)Σ11.86(As3.77Sb0.23)Σ4.00S12.57. Tennantite-(Cu) is cubic, I$\overline 4$3m, with unit-cell parameters a = 10.1710(10) Å, V = 1052.2(2) Å3 and Z = 2. Its crystal structure was refined by single-crystal X-ray diffraction data to a final R1 = 0.0178 on the basis of 263 unique reflections with Fo > 4σ(Fo) and 24 refined parameters. Tennantite-(Cu) is isotypic with other tetrahedrite-group minerals. Previous findings of tennantite-(Cu) are reported and some nomenclature issues, related to the Fe and Cu oxidation states, are discussed. At the Layo epithermal deposit, tennantite-(Cu) is the result of the replacement of enargite under decreasing $f_{{\rm S}_ 2}$ conditions.

Charrier est un petit gisement de cuivre–étain riche en indium de type skarnoïde du Forez (nord du Massif central). Il est encaissé dans une série volcanosédimentaire du Dévono-dinantien au contact du granite viséen des Bois-noirs. Sa genèse comprend une étape précoce oxydée de haute température (vers 550–350 °C) à cassitérite–magnétite, suivie d’une étape réduite sulfurée (vers 350–250 °C) à bornite–chalcopyrite dominantes avec wittichénite, tennantite, sphalérite, bismuthinite et roquesite (CuInS2) qui se déroule en conditions de pH acide et de faible fugacité en soufre. L’apatite hydrothermale fournit un âge U–Pb de 340,7 ± 2,6 Ma identique à celui du granite (341 ± 4 Ma) ; il est confirmé par l’âge U–Pb de 332 ± 12 Ma obtenu sur cassitérite. Le gisement s’est donc formé au début de l’extension tardi-varisque par l’action des fluides magmatiques à Sn–Bi–In issus du granite des Bois-noirs (341 ± 4 Ma) ayant interagi avec la série volcanosédimentaire. Charrier pourrait traduire la superposition d’un district à cuivre sur une vaste ceinture à étain (et tungstène), ce qui suggère la présence d’autres gisements de cuivre/étain dans cette région. Cette superposition est bonifiée par une richesse particulière en indium du nord-Forez, ce métal s’exprimant du Viséen (roquesite de Charrier) jusqu’au Lias (sphalérite à indium des filons plombo–zincifères), illustration du phénomène de permanence métallique.

Charrier is a small indium-rich copper-tin deposit of the skarnoid type in Forez (North French Massif central). It is hosted in a Devono-dinantian volcano-sedimentary series at the contact with the Visean Bois-noirs granite. Its genesis includes an early high temperature oxidized stage (around 550-350 ?) with cassiterite-magnetite, followed by a reduced sulphide stage (around 350-250 ?) with bornite-chalcopyrite dominant with wittichenite, tennantite, sphalerite, bismuthinite and roquesite (CuInS2) which takes place under conditions of acidic pH and low sulfur fugacity. Hydrothermal apatite provides a U-Pb age of 340.7 +/- 2.6 Ma identical to that of the granite (341 +/- 4 Ma); it is confirmed by the U-Pb age of 332 +/- 12 Ma measured on cassiterite. The deposit was therefore formed at the beginning of the late-Variscan extension by the action of magmatic Sn-Bi-In fluids issued from the Bois-noirs granite (341 +/- 4 Ma) and which reacted with the volcano-sedimentary series. Charrier could reflect the superimposition of a copper district on a vast tin (and tungsten) belt, what suggests the presence of other copper/tin deposits in this region. This superimposition is enhanced by a particular richness in indium in northern Forez, this metal being expressed from the Visean (roquesite of Charrier) to the Lias (indium sphalerite from the lead-zinc veins), an illustration of the phenomenon of metallic permanence.

A field study combined with a laboratory study and 3D modeling have been performed in order to decipher the genesis of the Salau deposit W-Au mineralization (Pyrenees, France), one of the most important for tungsten in Europe. Results show the existence of two superimposed ore types, emplaced ca. 10 km depth and within decreasing temperature conditions: a calcic silicates skarn with rare scheelite and disseminated sulphides followed by a mineralized breccia with massive sulphides (pyrrhotite and chalcopyrite dominant), coarse-grained scheelite and gold, representing the main part of the ore mined in the past. This breccia is localized in ductile-brittle shear-zones which crosscut the granodiorite. U/Pb dating on zircon, apatite and scheelite, previously realized, confirmed this polyphase evolution. These two types of mineralization, linked to the emplacement of two successive intrusions as confirmed by sulphur isotopic analysis, granodioritic then leucogranitic, can be classified as belonging to the Intrusion-Related Gold Deposit type (IRGD). The emplacement of the high-grade gold and scheelite breccia was initiated by the progressive localization of the regional deformation in the Axial Zone of the Pyrenees during the Permian within E-W dextral-reverse faults.

Shear zones hosted antimony (Sb) quartz vein-type deposits are the most important sources of Sb worldwide. They have been recognized and mined since the Antiquity in the European Variscan belt, and particularly in the French Variscan Massifs, as the Armorican Massif. Among this type of deposit two subtypes are identified, i) the Sb and gold (Au) quartz vein-type (Sb-Au) as the La Lucette deposit located in the North Armorican Domain, and ii) the Sb-As quartz vein-type as those from the la Bellière district in the Ligerian domain. The recent advances in the understanding of the Sb mineralizations in the European Variscan Belt are typically focused on the Sb ore-genesis and its regional implications, ignoring its potential valuable co-products as gold. In this study, detailed textural-mineralogical investigations coupled with geochemical analyses in rock-samples with in-situ EPMA and LA-ICPMS ore-minerals trace element analyses, were carried out for the first time in the Late-Variscan mineralizations from the La Bellière Sb-As occurrences, and the La Lucette Sb-Au deposit, to ascertain the distribution and amount of Au in the ore-minerals and provide new data on ore deposition conditions. In the La Bellière Sb-As occurrences, no visible gold has been observed, but low-grade gold, ranging between 0.2 to 1 g/t Au, are correlated with high-grade As in rock sample. In the La Lucette Sb-Au deposit, historical assays have shown high-grade gold with an average at 40 g/t Au. EPMA and LA-ICP-MS analyses have demonstrated that gold is already present during the early time of the mineralization as invisible gold, trapped in the lattice of the Sb-rich arsenopyrites, with an average grade of 70 ppm Au in La Bellière, and at higher average grade of 223 ppm Au for La Lucette. For both type of mineralization, the early invisible gold is concentrated preferentially in the borders of the arsenopyrite crystals, and is correlated with an increase of the As content, and a decrease of the Sb and Fe. We argue that gold could be added in the arsenopyrite by substitution with the Fe and Sb at high temperature > 300 °C. Visible gold corresponds to the economic gold ore of the Sb-Au mineralizations. In the La Lucette ore, it is emplaced in the late stages, as discrete electrum grains spatially associated with the arsenopyrites, as native gold inclusions within the stibnite, and associated with rare aurostibite. Remobilization processes of the gold-bearing arsenopyrite at lower temperature, coupled with a minor initial enrichment of the Sb-bearing ore-fluid might be responsible of the late high-grade gold ore, and the visible expression of this element. In the absence of such remobilization process with late ore-fluid-enrichment, only low-grade gold is present, under the form of invisible gold in auriferous-arsenopyrites. The presence of a valuable gold co-product, also present in the Sb-As mineralizations, unknown until now in the French Variscan Massifs, will improve its economic attractivity. Gold potential in the huge French Sb-districts as the Vendée or the Brioude-Massiac districts must be reassessed.

The synthesis of 240 lead isotopes analyses, measured on Moroccan ore deposits of Ediacarian to Neogene ages located in all geotectonic domains of Morocco allows a global reflection on the metallogeny of Morocco. The isotopic compositions vary widely, from 17.738 (Bou Skour) to 18.905 (Draa Sfar) for the Pb-206/Pb-204 ratio, and from 15.521 to 15.706 for the Pb-207/Pb-204 ratio. The source of lead in the studied deposits is located in the upper continental crust, except for those in the Anti-Atlas (Bou Skour, Imiter, etc.) and some in the High Atlas (Azegour) with a clear mantellic contribution. Isotopic variations noted at the scale of a district result either from the presence of several superimposed hydrothermal events calling upon different local sources as at Tighza, or from a single event disturbed by the segmentation of a volcanosedimentary basin, as for the Jebilet and Guemassa ore deposits. At the scale of the deposit (Draa Sfar, Bou Skour), isotopic variations result from the superposition of several hydrothermal events each with their own lead and associated metals. Overall, we can distinguish three generations of lead incorporated successively into the Moroccan geological basement by magmatism and/or hydrothermalism, characterized by their Pb-206/Pb-204 ratios: 17.74-17.90 (Panafrican), 18.10-18.40 (Hercynian) and 18.75-18.90 (Alpine). Panafrican lead is present in the Anti-Atlas, and very locally in the Meseta (Bouznika), and feeds in part on the mafic magmatism of Gondwana. Hercynian lead is the most represented and displays a definitive rupture in the source of metals, which is now exclusively crustal. It invades all Moroccan areas, including the Anti-Atlas, where it re-mobilizes and mixes with the panafrican lead. Alpine lead, more discreet, marks out the large scarf going from Agadir to Nador which traces on the surface the mantle plume of the Canaries and accompanies a Neogene magmatism which may also have acted as a simple engine remobilizing Hercynian lead, in particular to form MVT deposits from Touissit. The Hercynian and Alpine lead influxes are partly responsible for resetting the Neoproterozoic mineralization, as at Bou Azzer or Imiter. In the Sawkins's model, lead isotopic results support successive remobilisations of lead stored in primary and secondary tanks, as well as inheritance phenomena. Finally, the good transfer of the isotopic signature of lead from ore deposits to surface gossans shows that the isotopic geochemistry of lead is a useful tool for mineral exploration in Morocco, moreover for stratiform polymetallic sulphides ore deposits of Hajar type.

In the Brioude-Massiac district (French Massif Central: FMC), a network of W-As-Bi-Au quartz veins constitutes the Bonnac deposit, where tungsten is the major economic element, together with high-grade gold (up to 15 g/t Au). The evolution of this mineralization has been divided into 3 stages: (i) an early deep-seated wolframite-löllingite stage formed between 12 to 9 km, at up to 400 °C; (ii) a ductile/brittle deformation stage associated with scheelite and arsenopyrite deposition, with an estimated temperature of 480–300 °C; (iii) a late stage controlled by fluid-overpressure potentially triggered by fault-valve mechanism, at a depth of 7 to 5 km, and a temperature estimated between 266 to 240 °C, is marked by micro-fracturing infilled by native bismuth, bismuthinite, hedleyite, electrum, pyrite and base-metals. Structural analysis and apatite LA-ICP-MS U/Pb dating demonstrate a spatial and temporal link between the emplacement of the peraluminous leucogranitic dykes and the Bonnac mineralization. In more details, the mineralization was deposited between 321–316 Ma, during, or just after, the emplacement of the peraluminous dykes estimated around 329–315 Ma, suggesting a magmatic-hydrothermal transition for the ore-forming process. In the proposed model, the cooling of a hidden two-mica granitic pluton could have generated a magmatic fluid, and acted as the heat source responsible for fluid flow towards inherited permeability zones. The magmatic fluid could have then re-equilibrated at high temperature by fluid-rocks interaction. The sharp changes in pressure, associated with the decrease of the temperature, and sulfide-fugacity generated by a late input of meteoric fluid were responsible for the deposition of the late gold-stage. At the regional scale, the tungsten-gold event is ascribed to an early hydrothermal stage, dissociated from the formation of the antimony event in the district. The leucogranitic dykes and Bonnac quartz veins are controlled by a NW-SE stretching direction, interpreted as an expression of the Serpukhovian-Bashkirian syn-orogenic extension (D4 event of the FMC). These new data provide evidence for an early tungsten and gold metallogenic event in the FMC, prior the “Or300” event. The genetic classification of the Bonnac mineralization is equivocal. The W-As-Bi-Au-quartz veins exhibit the features of both an “orogenic gold” deposit at a relatively deep emplacement level (mesozonal), and an Intrusion-Related-Gold-Deposit (IRGD) type with a spatial-temporal link with the peraluminous intrusion emplacement. We propose that the Bonnac deposits represent an intermediate type between a typical orogenic-gold deposit and an IRGD. We argue that the presence of economic high-grade gold content in tungsten vein-type, and more generally the IRGD deposits, have been underestimated in the Variscan French Massif Central.

La synthèse de 240 analyses isotopiques du plomb, mesurées sur les gisements miniers marocains d’âges édiacarien à néogène appartenant à tous les domaines géotectoniques du Maroc autorise une réflexion globale sur la métallogénie du Maroc. Les compositions isotopiques varient grandement, de 17,738 (Bou Skour) à 18,905 (Draa Sfar) pour le rapport 206Pb/204Pb, et de 15,521 à 15,706 pour le rapport 207Pb/204Pb. La source du plomb des gisements étudiés se situe dans la croûte continentale supérieure, excepté pour ceux de l’Anti-Atlas (Bou Skour, Imiter…) et certains du Haut-Atlas (Azegour) à nette contribution du manteau. Les variations isotopiques relevées à l’échelle d’un district résultent soit de la présence de plusieurs événements hydrothermaux superposés sollicitant différentes sources locales comme à Tighza, soit d’un seul événement perturbé par la segmentation d’un bassin volcanosédimentaire, comme pour les amas sulfurés des Jebilet et Guemassa. À l’échelle du gisement (Draa Sfar, Bou Skour), les variations isotopiques résultent de la superposition de plusieurs événements hydrothermaux avec chacun leur propre plomb et métaux associés. Globalement, on peut distinguer trois générations de plomb incorporées successivement dans le socle géologique marocain par le magmatisme et/ou l’hydrothermalisme, caractérisées par leurs rapports 206Pb/204Pb : 17,74–17,90 (panafricain), 18,10–18,40 (hercynien) et 18,75–18,90 (alpin). Le plomb panafricain est présent dans l’Anti-Atlas, et très localement dans la Meseta (Bouznika), et se nourrit en partie du magmatisme mafique du Gondwana. Le plomb hercynien est le plus représenté et affiche une rupture définitive dans la source des métaux dès lors exclusivement crustale. Il envahit tous les domaines marocains, y compris l’Anti-Atlas, où il remobilise et se mélange avec le plomb panafricain. Le plomb alpin, plus discret, jalonne la large écharpe allant d’Agadir à Nador qui trace en surface le panache mantellique des Canaries et accompagne un magmatisme néogène qui peut aussi avoir agi comme simple moteur remobilisant le plomb hercynien, notamment pour former les gisements MVT de Touissit. Les plombs hercynien et alpin sont en partie responsables du rajeunissement des minéralisations néoprotérozoïques, comme à Bou Azzer ou Imiter. Le Maroc illustre le modèle de Sawkins avec un apport majeur du plomb lors du magmatisme fini-orogénique. Les résultats isotopiques plaident en faveur de remobilisations successives du plomb stocké dans des réservoirs primaires et secondaires avec des phénomènes d’héritage. Enfin le bon transfert de la signature isotopique du plomb des gisements aux gossans de surface, notamment pour les gisements stratiformes de sulfures polymétalliques de type Hajar, montre que la géochimie isotopique du plomb est un outil utilisable pour l’exploration minière au Maroc.

La coupole de Montebras est un petit massif de granite à métaux rares (Sn, W, Li, Nb-Ta) situé au nord du Massif Central Français qui se met en place au Carbonifère supérieur dans un encaissant plus ancien, le granite de Chanon (357,2 ± 2,1 Ma). Deux épisodes magmatiques, un microgranite (316,1 ± 4,3 Ma) et un leucogranite albitique (309,8 ± 3,9 Ma), sont distingués. Le second développe à son toit des formations de contact, notamment une puissante pegmatite stockscheider (309,7 ± 4,5 Ma), passant vers l’est à des greisens à lithium et des filons plats de quartz stannifères anciennement exploités (303,8 ± 4,8 Ma). Le dépôt de cassitérite (associée à la manganocolumbite) s’étale depuis la phase magmatique avec des cristaux disséminés dans le leucogranite, jusqu’à la fin de la phase pneumatolytique marquée par des filons de quartz stannifères. Cet étalement se traduit par une baisse progressive des concentrations en éléments-traces (Nb, Ta, Fe, Mn, Mg, Ti) dans la cassitérite mais sans que soit atteint le domaine des compositions typiquement hydrothermales. Lors de la phase pneumatolytique, la cassitérite est accompagnée de rare scheelite, de la rarissime qitianlingite et d’une wolframite fréquente dont la composition (hübnérite) indique une origine magmatique pour le métal et les fluides impliqués dans le dépôt du tungstène. La paragenèse à sulfures riches en Cu, As et Sn (löllingite, chalcopyrite, tennantite, stannoïdite, mawsonite…) marque le passage à la phase hydrothermale et suggère une origine dans les roches encaissantes pour le cuivre et l’arsenic. L’événement fluo-barytique liasique se manifeste par l’apparition locale de fissures à fluorine violette, barytine et manganapatite. La coupole de Montebras fournit un exemple représentatif des granites à métaux rares de la chaîne varisque. Elle est contemporaine des autres magmas granitiques à éléments rares du nord Massif central avec lesquels elle présente des points de similitude mais aussi des différences. Sa mise en place pourrait relever d’un mécanisme de type cauldron subsidence.

The La Belliere gold district, in the Ligerian domain of the Armorican Massif is the third one of France in term of production. It shows gold-bearing quartz veins neighboring with a complex network of Sb veins, hosted in the Neoproterozoic metasedimentary basement of the Mauges Nappe. New structural data, mineralogical, textural and geochemical assays have been carried out to clarify the gold and Sb veins relationships. Our results favor of two-step hydrothermal event with an early deep-seated gold event followed by a late shallower Sb event. The gold-bearing quartz veins are hosted by N60 degrees E to N90 degrees E sinistral strike-slip faults. These veins exhibit a fourstage paragenesis: 1) early barren quartz filling, 2) arsenopyrite-pyrite with minor scheelite assemblage, 3) gold and base metal sulfides crystallized after a ductile/brittle deformation stage, and 4) pyrite-carbonate coeval with a late brittle stage. These results support a continuous evolution model from a deep emplacement level (12 to 9 km) to a shallow one (7 to < 5 km) with a brutal change in the P/T conditions that triggered the deposition of gold (stage 2) controlled by a seismic-valve mechanism. On the contrary, Sb veins correspond to open space vein types, hosted in a N20 degrees W to N20 degrees E conjugated strike-slip fault network arranged in a Riedel shear model, controlled by N130-140 degrees E regional dextral strike-slip shear zone associated to the South Armorican Shear Zone system. A two-stage evolution is recognized, the first one consists of early pyrite-arsenopyrite with microcrystalline quartz, followed by a late stibnite stage formed after geodic quartz deposition. Quartz texture argues for a shallow emplacement (< 5 km) of veins controlled by a suction-pump mechanism. Chronologically, the gold vein opening complies with a NE-SW maximum shortening direction different from the late-Variscan stress field responsible for the dextral Armorican shear zone during late Carboniferous, and constrains an indirect dating. Thus, a Visean age is proposed for the formation of gold veins. The overall features of gold deposits are close to those of mesozonal orogenic gold deposits in Europe. Conversely, Sb-bearing veins are generated by a N-S shortening during the late Carboniferous. The Sb event, distinct in time from the earlier gold one, might correspond to a different expression of the so-called "epizonal" type in the orogenic gold model. It is proposed that the Late Carboniferous "Or 300" event is not the unique metallogenic period for gold deposition in the French Variscan domain. Our study highlights the role of the sinistral strike-slip shearing of possible Visean age, in the gold metallogenesis of the Ligerian domain.

The Argemela mineralized area (AMA), central Portugal, exhibits a nearly continuous magmatic to hydrothermal ore-forming sequence typical of Variscan granite-related rare metal deposits. Disseminated and vein-type mineralization are distributed in two systems, the Argemela Mine (AM) and the Cabego da Argemela (CA). Disseminated mineralization includes montebrasite, cassiterite and columbite-tantalite dispersed in rare metal granites. Vein-type mineralization occurs both in granites and country rocks. The CA system exposes three generations of intragranitic veins with montebrasite in the two earliest and montebrasite, wolframite, cassiterite and columbite-tantalite in the latest. Country rock veins include a swarm of cassiterite and montebrasite veins (AM) and rare isolated wolframite veins (CA). Disseminated cassiterites are enriched in Ta2O5 and Nb2O5 compared to vein cassiterites. Disseminated columbite-tantalites evolve toward Mn- and Ta-rich chemistries that contrast with the more Fe- and Nb-rich compositions in intragranitic veins. In the CA system, both intragranitic and country rock veins crystallize early Mn-rich wolframites followed by late more Fe-rich compositions associated with Nb-, Ta-poor cassiterite, the later replaced by stannite. Field relations, structural, mineralogical and geochemical data suggest that the disseminated and vein-type mineralization are expressions of a continuous metallogenic evolution initiated at the magmatic stage, pursued during the magmatic-hydrothermal transition and ended with hydrothermal circulations in country rock. The two mineralized systems share similarities, but they also show major differences. Structural analysis demonstrates that the intragranitic veins in the CA and the country rock veins in the AM were emplaced under the same tectonic regime. Therefore, the two systems are variants of the same local metallogenic evolution. Sn and W show markedly contrasted behaviors. Both have a magmatic source but only Sn reaches concentrations leading to saturation of the melt with cassiterite. W is deposited later and preferentially to Sn in intragranitic veins. At the hydrothermal stage, cassiterite and wolframite deposition are disconnected and, overall, wolframite occurs only in minor amounts. The metallogenic model proposed for the AMA emphasizes magmatic rare metal concentration processes, exsolution of magmatic fluids and selective deposition of metals during the magmatic-hydrothermal and later hydrothermal stages. The Sn-Li-(Nb-Ta)-dominated, and W-poor signature of the AMA makes it similar to LCT pegmatites of the Central Iberian Zone but is distinctive from the world class W-(Sn-Cu) Panasqueira deposit nearby.

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 suggesting 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 reverse-dextral shear zones.

The Mo-Cu-W Azegour skarn, located in the High-Atlas in Morocco, is associated with a Late Hercynian alkaline granitic intrusion. Here the origin of the mineralisation via Re-Os geochronology and using Mo, S and Pb isotopes is discussed. The age of mineralisation defined by Re-Os molybdenite geochronology is 276 +/- 1.2 Ma for the Azegour mine, and 267 +/- 1.2 for the Tizgui deposit suggesting for multiple mineralisation events associated with the Hercynian alkaline granitic intrusion. The delta Mo-98(NIST) of molybdenite range from -0.60 parts per thousand to 0.42 parts per thousand (n = 26) for the Azegour mine and from 0.08 parts per thousand to 0.40 parts per thousand (n = 2) for the Tizgui mine. Variations of the delta Mo-98(NIST) occur either at the deposit scale with a difference of about 0.72960, and at the sample scale (few cm), which exhibits a difference of up to 0.40 parts per thousand. A multi-phased mineralisation is proposed as the main processes explaining the variation in the delta Mo-98(NIST) values although the influence of a Rayleigh fractionation process cannot be precluded. The high delta S-34 values determined from molybdenite, pyrrhotite, and chalcopyrite (8-14.7 parts per thousand) suggest a sedimentary origin for sulphur from the Cambrian sedimentary country rocks. Whereas, the initial Pb-206/(204) Pb compositions of common lead (18.08-18.30) for chalcopyrite and pyrrhotite imply a strong contribution of lead from the host volcano-sedimentary units.

axis. Observation on calcite shapes and the direction of the magnetic lineation are coherent, suggesting that it is possible to track hydrothermal paleo-circulation using magnetic lineation and petrographic fabrics.

Isotopic compositions of Mo in molybdenites were used for deciphering a possible genetic link between isotopic variations and mineralizing processes, based on a worldwide molybdenite databank. We compared the δ98/95Mo (hereafter referred as δ98MoNIST) of 391 molybdenite samples (193 from the literature, 198 for this study) from different localities, different types of occurrences and different ages. The 198 molybdenite samples we analysed represent various types of mineralization in 6 granites, 11 pegmatites, 6 perigranitic veins, 2 greisen, 28 porphyry deposits, 5 skarns, 1 IOCG, and 9 Alpine-type fissure veins, with ages varying from 5 Ma to 2.7 Ga. The Mo isotopic composition was determined with an MC-ICP-MS Neptune after aqua regia dissolution and adjustment to [Mo] = 1 μg·ml− 1. Mass bias was corrected by using Zr as dopant and standard-sample-standard bracketing. The δ98MoNIST ratios were normalized to NIST3134. External reproducibility is 0.07‰ (2σ). The overall range of the δ98MoNIST ratio in the 391 molybdenite samples varied from − 1.62 to 2.27‰, being higher for molybdenite formed in Alpine-type veins, greisen, perigranitic veins and IOCG, than for that in granite, pegmatite, porphyry deposits and skarns. The crystallization temperature can explain some of these differences, as polymetallic Alpine-type fissure veins broadly crystallize at lower temperatures than granite, pegmatite and porphyry deposits. For some occurrences the δ98MoNIST was determined on several molybdenite samples, showing variability at occurrence scale. For example, in the Azegour skarn (Morocco) the δ98MoNIST varies from − 0.60 to 0.42‰ (n = 29), and in “Ravin de la Ruine” Alpine-type fissure veins (France) the variation is from − 0.08 to 0.77‰ (n = 3). No correlation is seen between δ98MoNIST and the age of the deposits.

Isotopic compositions of Mo in molybdenites were used for deciphering a possible genetic link between isotopic variations and mineralizing processes, based on a worldwide molybdenite databank. We compared the δ98/95Mo (hereafter referred as δ98MoNIST) of 391 molybdenite samples (193 from the literature, 198 for this study) from different localities, different types of occurrences and different ages. The 198 molybdenite samples we analysed represent various types of mineralization in 6 granites, 11 pegmatites, 6 perigranitic veins, 2 greisen, 28 porphyry deposits, 5 skarns, 1 IOCG, and 9 Alpine-type fissure veins, with ages varying from 5Ma to 2.7Ga. The Mo isotopic composition was determined with an MC-ICP-MS Neptune after aqua regia dissolution and adjustment to [Mo]=1μg·ml−1. Mass bias was corrected by using Zr as dopant and standard-sample-standard bracketing. The δ98MoNIST ratios were normalized to NIST3134. External reproducibility is 0.07‰ (2σ). The overall range of the δ98MoNIST ratio in the 391 molybdenite samples varied from −1.62 to 2.27‰, being higher for molybdenite formed in Alpine-type veins, greisen, perigranitic veins and IOCG, than for that in granite, pegmatite, porphyry deposits and skarns. The crystallization temperature can explain some of these differences, as polymetallic Alpine-type fissure veins broadly crystallize at lower temperatures than granite, pegmatite and porphyry deposits. For some occurrences the δ98MoNIST was determined on several molybdenite samples, showing variability at occurrence scale. For example, in the Azegour skarn (Morocco) the δ98MoNIST varies from −0.60 to 0.42‰ (n=29), and in “Ravin de la Ruine” Alpine-type fissure veins (France) the variation is from −0.08 to 0.77‰ (n=3). No correlation is seen between δ98MoNIST and the age of the deposits.

The Mo-W-Cu skarn of Azegour is generated at the expense of a sequence dominated by calcareous sedimentary rocks Cambrian in age, within the metamorphic aureole of a Permian granite. Metasomatized layers constituting the skarn are several meters thick, and mainly composed of massive garnetite and/or wollastonitite and seldomly of pyroxenite. Garnets belong to three different types easy to recognize due to their different colors: green-black, brown-black and orange, this later one being present only in the northern part (Toulkine zone) of the skarn. The green-black garnet is very common, forming crystals up to 8 cm, and composed of andradite with locally a core of Al-rich andradite (up to 5% Al2O3). The very common brown-black garnet form thick layers associated with quartz. It often reveals a core of pure andradite surrounded by a Al-rich andradite (up to 10% Al2O3), close to the grossular domain. Orange garnet is only grossular. Pourcentage of spessartine is always weak (4% maximum). Wollastonite is slighly manganiferous, while vesuvianite is F- and Cl-rich (up to 3.3% and 1.2% respectively). Mineralogical association allow to establish the formation of the skarn around 620-650 degrees C, under a pressure of 1.7-2 kbar, and a fCO(2) of 31 mole %, in a reducing environment (fO(2) of 10(-18) to 10(-17) atm.). The skarn of Azegour marks the end of Hercynian orogeny and whitnesses of the perennity of a reducing environment highly favorable to sulphide crystallization. Mo-skarn of Azegour seems to have formed at higher temperatures than other Hercynian W-skarn such as Salau (France).