Geochemistry of Sulfur and Lead Isotopic Compositions of Sedex Lead-zinc Deposits in Fengtai Mineral Cluster Region of Qinling Mountains

Fengtai mineral cluster region is located in the middle of Qinling Devonian lead and zinc polymetallic metallogenic belt. Lead-zinc deposits are mainly located in the siliceous rocks between Gudaoling group of the Upper Devonian and Xinghongpu group of the Middle Devonian. The analysis of S and Pb isotopic compositions of ore minerals in three typical ore deposits indicates that δ³⁴S values of metal sulfide range no more than 10‰ in Qiandongshan, Bafangshan and Yinmusi lead-zinc deposits. The δ³⁴S values of sulfides in the region range from 4.3‰ to 13.2‰, indicating that sulfur mainly came from seawater sulfate reduction. Among the lead isotope of three deposits, ²⁰⁶Pb/²⁰⁴Pb varies from 17.775 to 18.180, ²⁰⁷Pb/²⁰⁴Pb varies from 15.457 to 15.805, and ²⁰⁸Pb/²⁰⁴Pb varies from 37.977 to 38.670. Pb isotopic compositions have a large overlap, suggesting that the three lead-zinc deposits have similar sources of lead. The analysis of structure model diagram and Δβ-Δγ diagram of Pb isotope shows that lead came from the process that Yangtze plate subducted to North China plate in the middle of Early Paleozoic and Qinling microplate subducted to North China plate in the late Paleozoic.