Geological Characteristics and Genesis Analysis of Baozishan Pb-Zn Deposit in Karakoram Area

The lead-zinc deposit of Baozishan,which is located in the Hetian area of Xinjiang Province, has the geological characteristics of epigenetic deposit related to hydrothermal metasomatic process. Mineralization occurs in the Middle Jurassic carbonatite of Longshan Formation and is strictly controlled by the NW trending faults. The main ores are smithsonite and acrusite. The alteration of country rocks are mainly hematitization and ferritization. Sulfur isotopic composition in ore has a wide distribution range (δ³⁴S=-8.49‰~24.88‰), indicating that the S originated from sedimentary strata and the additions of surface fluid. The lead isotopic composition in ore is relatively homogeneous (the values of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and μ are 18.807-18.822, 15.73-15.756, 39.055-39.168, 9.68-9.73 respectively), with Pb coming from the upper crust. The values ofδ¹³C_V-PDB and δ¹⁸O_V-SMOW vary from 2.85‰ to 8.25‰, 20.04‰ to 21.07‰ respectively, implying that C and O are from carbonate rocks rather than magmatic hydrothermal fluid. With the analysis of geology of the deposit and isotopic characteristics, Baozishan deposit is regarded as the tectonic hydrothermal-direct metasomatic lead-zinc.