Geochronology, Geochemistry and Hf Isotopic Compositions of the Granodiorite in the Shazigou Copper Deposit, West Kunlun

The Shazigou Copper deposit is located in the western part of West Kunlun Orogenic Belt, and the granodiorite in this deposit is closely related to copper mineralization. In this paper, the major and trace elements, zircon U-Pb dating and in-situ zircon Hf isotopic compositionof the granodiorite have been reported and studied. The LA-ICP-MS zircon U-Pb dating yields an age of late Triassic (213.7±2.6)Ma, which has been interpreted as the crystallization age of zircons extracted from the granodiorite. The zircon Hf isotope data shows that εHf(t) values vary from-2.72 to 1.21, indicating the involvement of a small portion of mantle-derived magma during the granodiorite diagenesis. Geochemical data indicates that these granodiorite belongs to I-type granite based on the following characteristics, such as enrichment in Ca, K, Mg and Fe, A/CNK values from 0.99 to 1.04 (<1.1), medium to strong negative Eu anomalies (δEu=0.54~0.94, average is 0.79), enrichment in large ion lithophile element (Rb,Th,K,Nd,Sm) and LREE, depletion in high field strength element (Ba,Nb,Ta,Sr,P,Ti) and HREE. The Shazigou copper deposit is ascribed to magmatic hydrothermal type. Its early metallogenic age coincides with the intrusion of the Shazigou granodiorite. The ore-forming materials are mainly from the lower crust of the orogenic belt. In this mining area, the weakly aluminous I-type granite provides material and heat sources for mineralization. Therefore, it's considered that the Shazigou granodiorite was formed in a post-collisional extension regime, following the Paleo-Tethyan orogeny. The source rocks might be the product of the strong mixing of crust-derived granitic magma and mantle-derived basic magma, which was caused by the mantle intruded into the ancient continental crust. The exchange interaction of crust-mantle materials provides a large amount of ore-forming materials for the copper polymetallic mineralization in the Shazigou area.