Abstract

The orogenic granitoids of the French Variscan are classified into three principal associations: aluminopotassic, subalkaline, and calc-alkaline. Each of these associations is characterized by the petrographical and geochemical composition of the members and the nature of the related mineralization.Aluminopotassic granitoids contain most of the observed Sn, W, and U mineralization and all the Be, Nb-Ta, and Li mineralization. They are associated with two-mica leucogranites, with a separate occurrence of Sn, W, Li, Be, Nb-Ta mineralization related to evolved sodic leucogranites and U mineralization related to potassic leucogranites.The Cu and Mo potential of the subalkaline granitoids is assessed by the occurrence of genetically related mineralized pegmatites and K feldspar veins and of postmagmatic veins and stockworks. Complex Sn-Cu and W-Mo mineralization occurs in areas and bodies characterized by the emplacement of both subalkaline and aluminopotassic granitoids. Evolved subalkaline granites and leucogranites contain U mineralization (occurrences, deposits) which can be enhanced by late aluminopotassic two-mica leucogranite intrusions.The calc-alkaline granitoids are conspicuously barren, except for some W skarn occurrences, a type of mineralization which is also observed around subalkaline and aluminopotassic intrusions. No Cu-Mo porphyry mineralization is observed in either calc-alkaline or subalkaline granitoids.The regional pattern of distribution of the granitoids and their related mineralization leads to the definition of three principal regions which differ by the volumic development of the various granitoid associations and the related mineralization. No clear magmatic or metalliferous polarity can be observed across the French Variscan. The observed pattern of distribution results from the ensialic evolution of the French Variscan orogeny and from the mainly crustal origin of the granitoids emplaced between 280 and 360 Ma in response to the postcollisional thrusting and shearing tectonics.Similar relationships between the mineralization and granitoid varieties are observed in the adjacent European segments of the French Variscan. Other classification schemes suffer some limitations, including being less discriminating, so that comparisons are not always useful.

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