The aim of this paper is to give a contribution to a general picture of the main processes governing recent magmatism in Tuscany, by studying the petrogenesis of the Roccastrada and S. Vincenzo volcanic centers in depth. Geochemical (major elements and Rb, Sr, Ba, Y, Nb, Zr, Hf, Th, Ta, Cr, Co, Sc, and REE) and mineral chemistry (two feldspars, biotite and cordierite) data on the Roccastrada and S. Vincenzo rhyolites, as well as Sr isotopic data on Paleozoic metasedimentary formations belonging to the Tuscan basement , are therefore presented. At Roccastrada only purely anatectic melts were observed . The crystallization temperature, pressure and water content for the phenocryst assemblages are estimated to be about 700°C, < 1 Kb and 2.5%. The rocks that crop out East and West of M. Alto represent two magma batches derived from the same source rock, by differing degrees of partial melting leaving differing residual mineralogies. The Paleozoic garnet-bearing micaschists could, on the basis of their geochemical and isotopic characteristics, be suitable source rocks . The S. Vincenzo volcanites are considerably enriched in Sr, Ba , Y, and REE in some samples. They have been interpreted to be the result of an interaction between a crustal anatectic melt and a mantle-derived melt. Linear a rrays on the A/B vs. 1/B diagrams allowed the extrapolation of the composition o f the mantle-derived magma. It exhibits strong enrichments in incompatible elements, and his pattern in a multielemental plot is very similar to those of some alkalic magmas cropping out in Southern Italy.
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