Zircon U–Pb geochronology and Sr–Nd–Hf isotopic compositions of the Yuanzhuding granitoid porphyry within the Shi-Hang Zone, South China: Petrogenesis and implications for Cu–Mo mineralization

Abstract

The Shi-Hang Zone is an important NE–SW-trending Mesozoic magmatic belt in South China, which is dominated by granites with relatively high εNd(t) values and young TDM model ages. Here, we present laser ablation inductively coupled plasma mass spectrometry (LA–ICP-MS) zircon U–Pb ages, major and trace element compositions, and Sr–Nd–Hf isotope data for the Yuanzhuding porphyritic granitoids within the southwestern Shi-Hang Zone, and use these data to determine the origin of this granitoid and its relationship with Cu–Mo mineralization. Zircon U–Pb dating indicates that these granitoids were emplaced at 157.8±1.1Ma. They have initial 87Sr/86Sr ratios of 0.70941–0.71398, εNd(t) values of −3.15 to −2.02, and in situ zircon εHf(t) values of +1.71 to +6.17. Geochemically, most of them are high-K calc-alkaline and show an adakitic affinity. They are more likely emplaced in a continental arc setting related to westward subduction of the paleo-Pacific plate. Their parental magma originated chiefly from the overlying sediments of the downgoing slab, and subsequently interacted with the lithospheric mantle wedge at the temperatures of ~790°C. High oxygen fugacity during magmatic evolution played a crucial role in the development of Cu–Mo mineralization within the Yuanzhuding. The discovery of the Yuanzhuding deposit implies that the Chenzhou–Huaiji fault belt is most likely prospective for mineral exploration for porphyry Cu–Mo deposits.