Rb-Sr isotopic Dating of Vein-like Sphalerites from the Chaima Au Deposit in Fengxian-Taibai Ore-concentration Area, Shaanxi Province and Its Geological Significance

The Chaima gold deposit is located at the northwest part of the Fengxian-Taibai ore-concentration area in Shaanxi Province, it is 0.5 km west to the super-large Baguamiao gold deposit, and both of them are similar in metallogenic geological environment and ore-controlling conditions. There are five ore-bearing zones in this deposit and their occurrences are controlled by both of lithology and structure. In this paper, the Rb-Sr isotopic dating has been carried out on the sphalerite from the sphalerite-galena vein of the main mineralization stage in the Chaima Au deposit, yielding an isochron age of (210.8±2.4) Ma, showing that the zinc mineralization was developed in Late Triassic. The ⁸⁷Sr/⁸⁶Sr_i ratio of the sphalerite is 0.710 55±0.000 11, indicating that the ore-forming materials are mainly derived from the continental crust. In the context of regional geology, it's suggested that lead-zinc mineralization and gold mineralization in the Fengxian-Taibai ore-concentration area are the common products in the Late Triassic collision process of the South Qinling orogenic belt, and the gold deposits and lead-zinc deposits are formed at the same era.