Petrogenesis of a Palaeoproterozoic S-type granite, central Wuyishan terrane, SE China: implications for early crustal evolution of the Cathaysia Block

摘要

We present zircon U-Pb ages, Hf isotopes, and whole-rock geochemistry of the Xiaochuan gneissic granite intrusion, SE China, to constrain its petrogenesis and provide insights into early crustal evolution of the Cathaysia Block. LA-ICP-MS zircon U-Pb dating of a representative sample yields a weighted mean ~(206)Pb/~(207)Pb age of 1839 ±16 Ma, interpreted as the emplacement age of the Xiaochuan granite. Zircons have ε_(Hf(t) values ranging from -8.1 to 2.7 and T_(DM2) model ages from 2.23 to 3.03 Ga. The granites are strongly peraluminious (A/CNK = 1.14-1.41), with relatively high FeO~t TiO_2, and CaO/Na_2O, and low CaO, Al_2O_3/TiO_2, and Rb/Sr values. In addition, they show strongly negative Ba, Sr, Nb, and Ta and positive Th and Pb anomalies in the primitive mantle-normalized spider diagram, similar to other Cathaysia Palaeoproterozoic S-type granites. The geochemical and Hf isotopic signatures suggest that the Xiaochuan gneissic granites were generated by partial melting of Archaean crustal materials in an' intraplate extensional setting. Our results, combined with existing geochronological data, further demonstrate that the Wuyishan terrane is underlain by Palaeoproterozoic crystalline basement.