Geology, geochemistry and genesis of the Suolong gold deposit in the West Qinling Orogen, Gansu Province, China

Abstract

The Suolong gold deposit is in the eastern part of the Min‐Li metallogenic belt within the West Qinling Orogen. It is hosted in Lower Permian sandstone and siltstone. The gold mineralization is fault‐ and joint‐controlled. Four hydrothermal stages of mineralization, including the sulphide‐quartz stage, the arsenian pyrite‐quartz stage, the polymetallic sulphide‐quartz‐carbonate stage and the sulphide‐carbonate stage, were identified. Here we report results from fluid inclusion studies and C‐H‐O‐S‐Pb isotopes to get insight into the characteristics of mineralization and ore genesis. Fluid inclusion results indicate that the ore‐forming temperatures and salinities were in the range from 135 to 419°C and 0.18 to 15.27 wt.%, respectively. The δ34S values of pyrite, arsenopyrite and pyrrhotite varied in the 5.3‰–11.4‰ range, suggesting that sulphur originated from stratum sulphur. Lead isotopic compositions of sulphide (206Pb/204Pb = 18.344–18.418, 207Pb/204Pb = 15.628–15.701, 208Pb/204Pb = 38.508–38.743) indicate an upper crust source for Pb. The δ18OH2O‐SMOW and δDSMOW values range from 1.01‰ to 10.31‰ and −116.0‰ to −29.2‰, respectively, indicating that metamorphic water was the source of ore‐forming fluids. The δ13CPDB values (−11.4 to −2.1‰) show that the carbon in the ore‐forming fluids originated predominantly from a deep source. Our data suggest that the Suolong gold deposit is an orogenic gold deposit related to the subduction of an oceanic plate along the Mianlue belt.