The Jinxi-Yelmand high-sulfidation epithermal gold deposit, Western Tianshan, Xinjiang Province, P.R. China

The Jinxi-Yelmand gold deposit is located in the late Paleozoic Tulasi intra-arc volcano-sedimentary basin in the Xinjiang Uygur Autonomous Province of northwest China. Although all known deposits in the Tulasi Basin were previously described as low-sulfidation epithermal systems, the recently discovered Jinxi-Yelmand deposit is interpreted here to be a modified high-sulfidation epithermal gold deposit based on its hydrothermal alteration assemblages, fluid inclusions and isotopic data. Hydrothermal alteration at Jinxi-Yelmand covers an area of about 4 km2 and is well zoned. The inner zone (Zone 1) is characterized by intense silicification, with a remnant quartz+dickite assemblage. Vuggy quartz textures are locally preserved in this zone. The intermediate zone (Zone 2) has advanced argillic alteration with a dickite+kaolinite+quartz+smectite assemblage. The outer zone (Zone 3) is characterized by an argillic alteration assemblage of montmorillonite+kaolinite. Gold is hosted mainly by quartz and pyrite in alteration zones 1 and 2. Fluid inclusion study indicates that the hydrothermal alteration and mineralization formed at temperatures between 198 and 275 °C and relatively low salinities (<5% NaCl equiv.). Oxygen and hydrogen isotopic data from fluid inclusions and alteration mineral assemblages, as well as geological relationships, suggest that the ore-stage hydrothermal fluids were of magmatic-hydrothermal origin, with early stage input of SO2-rich magmatic vapors. This study reports the first recognized occurrence of a modified high-sulfidation style hydrothermal system in the western Chinese Xinjiang province, enhancing the potential for the exploration of epithermal gold in this region.