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Variscan subduction-related plutonism in the French Massif Central
Usmanova, Diana ; Janoušek, Vojtěch (advisor) ; Špillar, Václav (referee)
The French Massif Central belongs to the Moldanubian Zone, which is an internal part of the Variscan Orogen. The Massif was formed during six tectonic-metamorphic events and has a nappe structure. The Muscovite-bearing Peraluminous Granitoids (MPG), Cordierite-bearing Peraluminous Granitoids (CPG), K-rich Calc-alkaline Granitoids (KCG), and Amphibole-bearing Calc-alkaline Granitoids (ACG) types of granitoids were intruded into the nappe units during the Carboniferous. The formation of FMC granitoid plutons was predominantly linked to continental collision; only the ACG plutonites are older, typical of magmatic arcs. These amphibole-bearing calc-alkaline quartz diorites to tonalites are common in the western French Massif Central (Limousin region), where a 250 km long belt known as the "Limousin tonalite belt" is found. Its linear shape and characteristic geochemical composition suggest a subduction-related origin. Newly obtained geochemical data from the Limousin region indicate an intermediate composition (52-57 wt% SiO2), a metaluminous, subalkaline character, and place the samples in the calc-alkaline series. Furthermore, enrichment of Large Ion Lithophile Elements (LILE), depletion of High Field Strength Elements (HFSE), negative europium anomaly (Eu/Eu* = 0,63-0,92) and relatively low initial...
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