Abstract: The Xingziyan stibnite deposit is located in the Central Hunan Basin (CHB), the middle section of the QinzhouHangzhou Joint Belt (QHJB). The stibnite ore bodies, controlled by NW-trending silicified fracture belt, are hosted in the pyrite-bearing carbonaceous and siliceous slate of the Cambrian Xiangnan Formation. In this study, we identified two ore-forming periods exhibiting three ore-forming stages. The sedimentary period typically presents rounded pyrite with recrystallized rims. And in the hydrothermal period, the early- and late-stage features presents stibnitequartz veins (wrapping around some host rock breccias) and stibnite-bearing calcite veins, respectively. The early-stage quartz and late-stage calcite in the hydrothermal period were selected to investigate fluid inclusions. Two types of widely developed fluid inclusion, H2O and CO2-H2O types, were identified under petrographic observation. The homogenization temperature and salinity of fluid inclusions ranged 113266 ℃ and 0.812.0 wt.% NaCleqv., respectively. Gaseous constituents in fluid inclusions were dominated by CO2 as identified by Laser Raman analysis. The characteristics of middle-to-low homogenization temperature, low salinity and high CO2 content indicate the ore-forming fluid may be of metamorphic origin. In consideration of the regional tectonic evolution, we conclude that the Xingziyan stibnite deposit, is an orogenic-type stibnite mineral system formed in the tectonic setting of the IndosinianYanshanian intracontinental strik-slip faulting.

Key words:  fluid inclusion, CO2-bearing fluid, Xingziyan stibnite deposit, QinzhouHangzhou Joint Belt (QHJB), orogenic-type stibnite deposit