Geochemical Study of Trace Elements and In Situ S–Pb Isotopes of the Sachakou Pb–Zn Deposit in the Aksai Chin Region, Xinjiang

The sulfide Pb–Zn deposits in the Aksai Chin region of Xinjiang have long been subject to debate regarding their genetic classification due to the unclear origin of the ore-forming components. This study focuses on the Sachakou Pb–Zn deposit, the most representative deposit in the region, and integrates field investigations, petrographic observations, in situ LA-ICP-MS trace element analysis, and in situ S–Pb isotope analysis. The deposit is hosted within the siliceous rock and silicified limestone of the Lower Jurassic Bagongbulansha Formation, with ore bodies controlled by structural and stratigraphic factors. Three mineralization stages have been identified in the Sachakou deposit: a red–brown sphalerite mineralization stage (S1), a light-brown sphalerite stage (S2), and a galena mineralization stage (S3). The trace elements in sphalerite indicate that the mineralization process is unrelated to magmatic activity. The mineralization temperature, determined using a GGIMFis geothermometer, ranges from 294 °C to 121 °C. The δ34SV-CDT values of sulfides range from −4.93‰ to 1.24‰, suggesting that the Jurassic gypsum layer served as the sulfur source. The lead isotope ratios of 206Pb/204Pb range from 18.308 to 18.395, of 207Pb/204Pb—from 15.669 to 15.731, and of 208Pb/204Pb—from 38.595 to 38.776, indicating that the ore-forming metals were predominantly sourced from the upper crust. Based on geological and geochemical characteristics, the Sachakou Pb–Zn deposit is classified as a sedimentary-hosted epizonogenic hydrothermal deposit.