Fluid inclusion and stable isotope studies of the Qiongbulake copper deposit in Western Awulale Mountain,Xinjiang

Abstract：The Qiongbulake copper deposit is the largest deposit in western Awulale Mountain copper belt of Xinjiang. Three ore types from No.1 ore body were selected for fluid inclusion and stable isotope studies. The results reveal that all the fluid inclusions are of L-V type and NaCl-H2O system. Fluid inclusions associated with calcite display moderate-low homogenization temperatures (85℃～343℃),moderate-low salinities (1.57～17.79 wt%NaCl eq.) and low densities (0.7g/cm3～1.05 g/cm3). The petrographic characteristics of the fluid inclusions in the three ore types are similar to each other,whereas some differences do exist for the homogenization temperatures and alkalinities. Carbon isotope determinations of calcite show δ13CPDB values of -3.2‰～-6.5‰, suggesting that the carbon was derived from the mantle. Oxygen isotope determinations of the fluids show δ18OSMOW values of 0.45‰～4.44‰. Sulfur isotope determinations of sulfides show δ34SVDT values of -10.5‰～5.5‰. The No. 1 ore body and other volcanic hydrothermal ore bodies have similar fluid inclusion and stable isotope characteristics. Therefore, the No. 1 ore body is not of sedimentation-transformation genesis but of volcanic hydrothermal genesis. The mixing of volcanic hydrothermal solution and circulated meteoric water was probably responsible for ore genesis. The slow cooling of ore-forming fluid played the most important role in the deposition of minerals. However, the effect of dilution and the increase of pH were not negligible.