Cadomian S-type granites as basement rocks of the Variscan belt (Massif Central, France): Implications for the crustal evolution of the north Gondwana margin

摘要: Abstract From the Neoproterozoic to early Paleozoic, northern Gondwana margin was sequentially shaped by Cadomian accretionary and Variscan collisional orogens which offers opportunity investigate relative extent of crust production/reworking in both geodynamic settings. In eastern part French Massif Central (FMC), Velay Orthogneiss Formation (VOF) represents a consistent lithological unit pre-Variscan basement comprises augen gneisses leucogneisses. Such rocks constitute unique record magmatic history bear critical information on crustal evolution margin. Here, we present whole–rock major trace element compositions indicating that: (i) VOF shows remarkable geochemical homogeneity; (ii) protolith corresponds strongly peraluminous, “S-type” porphyritic granites originating from partial melting an Ediacaran sedimentary sequence; (iii) leucogneisses are former leucogranites generated fractionation magma at origin granites; (iv) whole suite emplaced shallow levels ( We propose that sediments occurred during inversion back-arc basin promoted high thermal gradient typical thinned domains. Therefore, other S-type granitoids indicative substantial reworking away any proper continental collision zone.