Characteristics of zircon U-Pb-Hf isotopes for the Gartasksitao porphyritic rocks and constraints on ridge subduction, Xinjiang

The Gartasksitao porphyry copper deposit is located in the western part of the porphyry metallogenic belt in West Junggar.The LA-ICP-MS zircon U-Pb age, geochemistry, and Hf isotopic compositions of the granodiorite porphyry for this deposit have been analyzed.The results show that the zircon U-Pb age of the granodiorite porphyry is 299.2 ± 5.3 Ma, formed between the Late Carboniferous and the Early Permian.The samples have high SiO₂, Al₂O₃, Na₂O, and low K₂O, high Mg^# and Sr, low Y, Yb, indicating affinity with the adakitic feature.Trace elements are characterized by enrichment of Cs-Ba-U LILEs and LREEs, depletion of in Ti-Nb-Ta and HREEs, and rarely Eu anomaly.The ¹⁷⁶Hf/ ¹⁷⁷Hf ratios are high, with positive ε_Hf (t) values (+10.1~+15.6, Avg.+12.8) and young T_DM2 (307.4 ~ 687.1 Ma), indicating that the granodiorite porphyry was derived from a depleted mantle source.It could be suggested that the porphyry was formed by the oceanic ridge subduction, accompanied by considerable Cu and Au mineralization, which indicates that the Gartasksitao porphyry copper deposit has promising prospecting potential.