Zircon U-Pb Dating, Petrology, Geochemistry of the Buya Pluton and Its MMEs in the Southern Margin of Tarim, Xinjiang

Paleozoic acidic intrusive rocks are widespread in the Tiekelike tectonic belt of the southern margin of Tarim. Petrography, whole-rock major and trace elements, and zircon U-Pb dating are reported for the Buya granodiorite and its mafic microgranular enclaves (MMEs), which are used to constrain their petrogenesis and tectonic setting. High-precision LA-MC-ICP-MS zircon U-Pb dating has revealed that the quartz monzobiorite was formed at 432.6±2.5 Ma (MSWD=1.5), and its microgranular enclaves were formed at 432.4±6.4 Ma (MSWD=0.031) indicating that both of them are the products of early Silurian magma activity. Chemical composition suggests that the enclaves were derived from partial melting of the mantle, while the magma of the host rocks is mainly crustal and is mixed with minor mantle-derived magma. Both the field and petrographic characteristics show that the dark enclaves were formed by the rapid condensation of the mafic magma into the felsic magma, which is the product of the magmatic mixing by the mantle underplating of the lower crust. They are magmatic records of the late stage of early Paleozoic collision orogeny in the southern margin of Tarim.