Molybdenite Re-Os Geochronology and S, Pb Isotopic Characteristics of Banchang Copper Polymetallic Deposit in Neixiang, Henan Province

A great breakthrough has been achieved in prospecting in Banchang copper polymetallic deposit, East Qinling orogenic belt in recent years, which is characterized by obvious mineralization zoning in the mining area. The Cu, Pb, Zn and Ag mineralizations are developed in the upper part, and the Cu and Mo mineralizations are located in the lower part of the mining area. With Re-Os isotopic dating of molybdenite, LA-ICP-MS zircon U-Pb dating of granite rocks, sulfur and lead isotopic tracing of metal sulfide, the metallogenic time, ore genesis and metallogenic dynamic setting of the deposit are discussed in this study. Re-Os model ages of six molybdenite samples are 149.8±2.4 Ma to 151.5±2.3 Ma, with the weighted average age of 150.7±1.9 Ma and isochron age of 151.0±4.6 Ma, indicating that the metallogenic epoch was Late Jurassic. The zircon U-Pb age of Zhifanggou granite porphyry which is located to the south of Banchang deposit is 148±1 Ma, indicating that magmatic activities occurred during the metallogenic period. Eleven δ³⁴S_V-CDT values for sulfides range from -1.2‰ to +1.2‰, and the values are interpreted to reflect a deep magmatic source of the sulfur. In addition, the results show that ²⁰⁶Pb/²⁰⁴Pb values range from 17.178 to 17.709, ²⁰⁷Pb/²⁰⁴Pb values range from 15.430 to 15.528 and ²⁰⁸Pb/²⁰⁴Pb values range from 37.476 to 37.847, which are similar to lead isotope values of Yanshan Period granites in North Qinling and the crustal basement of South Qinling but very different from lead isotope values of the North Qinling strata. It is concluded that Banchang copper polymetallic deposit belongs to skarn-like type-hydrothermal vein type deposit which is related to Yanshannian magmatic activity, and it formed in the lithospheric thinning setting of East Qinling.