Genesis and Prospecting Significance of the Buziwannan Gold-Polymetallic Ore Deposit in the West Kunlun Orogen Belt, China: Constraints from Mineral Geochemistry and in Situ S–Pb Isotope Analyses of Sulfides

The Buziwannan gold-polymetallic deposit is located in Northwest China's West Kunlun Orogen Belt (WKOB). There are two metallogenic stages that have been identified: skarn and hydrothermal. In this research study, in situ mineral geochemistry and sulfur-lead isotopes are used to precisely constrain the genesis and ore-forming process. Pyrite is the most dominant sulfide, and four types have been identified. Py0 is a sedimentary euhedral crystal; Py1 is a subhedral grain occurring in skarn ores, and coexists with Po1, Apy1, Ccp1 and Gn1; Py2, which coexists with Apy2, Po2 and Ccp2, is a subhedral to irregular crystal; and Py3 is a colloform crystal. Gn2 is the most recent sulfide. Magnetite and Ccp1 LA-ICMPS analyses indicate a skarn origin. Py0 and Py1 have the highest Co/ Ni ratios and Ni contents, respectively, and Au has positive correlations with Pb, Ag and As, according to the trace element compositions of pyrite (LA-ICPMS). With the exception of four spots, most pyrites have Au (0.01-30.23 ppm) and As (1.47-15,709 ppm) concentrations below the Au saturation line, indicating that the majority of gold is present as lattice bound Au+. Py3 has clearly higher Sb contents indicating that Sb-rich fluids were added. The delta 34S values of sulfides show that the sedimentary Py0 and skarn sulfides have the highest and lowest delta 34S values of +13.30 to +14.67 %o and +4.48 to +7.77 %o, respectively, and other sulfides possess delta 34S values that fall between the two members, indicating a mixed source of magmatic and sedimentary. The lead isotope values also indicate that the sulfides from the hydrothermal stage have a mixed Pb source of magmatic and sedimentary. The skarn ores are spatially and genetically related to the Triassic granodiorite, indicating a Triassic age for ore formation. The Triassic magmatic intrusions hold the potential for future gold deposit exploration in the WKOB.