Evidence of two different components in a Hercynian peraluminous cordierite-bearing granite: the San Basilio intrusion (central Sardinia, Italy)

Detailed petrographic and geochemical data and Sr and Nd isotope compositions of enclaves and host-granite are reported for one of the largest strongly peraluminous cordierite-bearing intrusions of the Hercynian Sardinia-Corsica Batholith: the San Basilio Granite. Together with petrographic and other geochemical data, the Sr and Nd isotopic data record different stages in a complex homogenization process of an unrelated mafic magma with a crustal melt. Petrographic and mineralogical data on metamorphic enclaves and geochemical modelling for trace elements in granite indicate melt generation by high-degree partial melting involving biotite breakdown of a dominantly quartzo-feldspathic protolith at about T > 750-800°C and P > 6 kbar leaving a granulite facies garnet-bearing residue, followed by emplacement at ~3 kbar. The data point to a decoupling between the Sr-Nd isotope systematics and major and trace element compositions, suggesting that the effect of the mafic component was minor on granite major and trace element concentrations, but significant on Sr and Nd isotopes.