SHRIMP zircon U-Pb dating and characteristics of Hf isotopes of the granodiorite porphyries in the Dongyuan W-Mo ore district, Qimen area, southern Anhui

Granodiorites in Jiangjia and neighboring areas are ore-bearing rock components of the Dongyuan W-Mo deposit in southern Anhui. The zircon SHRIMP U-Pb data show that these rock bodies were formed at 149~152 Ma, almost at the same time with the formation of the Dongyuan W-rich granodiorite. The whole-rock chemical and zircon Hf isotopic data indicate that these magma sources have complex multi-component end-members. CL images reveal that the young zircons occur as new grains or rims of homogeneous structure with magmatic zoning, whereas most of the old ages occur in cores or as single xenocrysts in Neoproterozoic granodiorites, showing that the magmatic source contained considerable amounts of components of early igneous rocks. Young magmatic zircon zones in the granodiorites samples are heterogeneous in εHf(t) values (-39.5~-2.86), probably indicating the mixture between crust and mantle materials during the formation of the magma, with old crustal rocks being the main source. Zircon Hf isotopic data and bulk-rock zircon saturation temperature (737~913°C) indicate that mantle-derived materials probably played a role in the generation of the granodiorites.