Petrogenesis and geodynamic implications of Neoproterozoic typical intermediate-felsic magmatism in the western margin of the Yangtze Block, South China

The South China Block preserves voluminous Neoproterozoic magmatism, it is thus an ideal site for understanding the mantle nature, crustal evolution, and crust-mantle interaction during the assembly and breakup of the Rodinia supercontinent. Although the previous studies have paid more attention to the mafic and felsic rocks, the systematic deep dynamics of intermediate-felsic intrusive rocks is unsubstantial. Based on the recent studies on the Neoproterozoic typical granitoid magmatism, this study provides a systematic insight on the magmatic response of different depth under subduction setting. The new study reveals that the western margin of the Yangtze Block was located at the subduction setting. Apart from the subduction fluids- and slab melts-related mantle metasomatism, the newly recognized ca.850~835 Ma high-Mg^# diorites suggest that there existed the subducted sediment melts-related mantle metasomatism. In addition, the identification of ca.840~835 Ma peraluminous granites indicates that the western margin of the Yangtze Block underwent not only the melting of the juvenile mafic lower crust but also the reworking of the mature continental crust during the Neoproterozoic. Moreover, the ca.780 Ma Ⅰ-type granodiorites-granites stand for the magmatic response of different crustal depth induced by the upwelling of asthenosphere mantle. The occurrence from ca.800 Ma thickened lower crust-derived adakitic granites to ca.750 Ma felsic crust-derived A-type granites suggest the geodynamic transition from regionally crustal thickening to extensional thinning under subduction background.