Geochronology, geochemistry, zircon Hf isotopic composition and genesis of Shihushan granite in Anning, Yunnan Province

The LA-ICP-MS zircon U-Pb age, rock geochemistry and zircon Hf isotopic composition of the Shihushan granite located in Dezi Village of Anning area were investigated in this study. The zircon U-Pb dating yielded a magmatic crystallization age of (616±20) Ma and inherited ages of (839±17) Ma, (766±15) Ma and (705.5±9.4) Ma, indicating pluton emplacement in Neoproterozoic Ediacaran Stage. The authors hold that the magmatic crystallization age of (616±20) Ma indicates the pluton emplacement in Neoproterozoic Ediacaran Stage, and the assemblage of inherited ages of (839±17) Ma, (766±15) Ma and (705.5±9.4) Ma represents the splitting of the Rodinia supercontinent. The age of (839±17) Ma may represent the initiation of the breakup of the Rodinia supercontinent, while the age of (616±20) Ma may represent the final stage of the breakup event. The major and trace elements of alkali feldspar granite show the characteristics of A-type granite with high SiO₂-K₂O-Al₂O₃ content, indicating an extensional environment. Zircons from samples have low ε_Hf(t) value (< 0). All samples are plotted on the upper crustal evolution area on t-t (Ma) and t-(¹⁷⁶Hf/¹⁷⁷Hf) diagrams. The two-stage Hf model ages range from 1.77 Ga to 2.31 Ga. According to the Nb/Y-Rb/Y diagram, the petrogenic material mainly originated from the 60% melting of the shale of the Paleoproterozoic lower crust.