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

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 & DEG;C and 0.18 to 15.27 wt.%, respectively. The delta S-34 values of pyrite, arsenopyrite and pyrrhotite varied in the 5.3 parts per thousand -11.4 parts per thousand range, suggesting that sulphur originated from stratum sulphur. Lead isotopic compositions of sulphide (Pb-206/Pb-204 = 18.344-18.418, Pb-207/Pb-204 = 15.628-15.701, Pb-208/Pb-204 = 38.508-38.743) indicate an upper crust source for Pb. The delta O-18(H2O-SMOW) and delta D-SMOW values range from 1.01 parts per thousand to 10.31 parts per thousand and -116.0 parts per thousand to -29.2 parts per thousand, respectively, indicating that metamorphic water was the source of ore-forming fluids. The delta C-13(PDB) values (-11.4 to -2.1 parts per thousand) 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.