Isotope Geochemistry of the Heihaibei Gold Deposit within the Kunlun River Area in the Eastern Kunlun Orogen in Northwest China and Its Metallogenic Implications

The Heihaibei gold deposit is located in the Eastern Kunlun Orogen in Northwest China. The gold mineralization here occurs predominantly in quartz veins within faulted granite zones. The sulfide mineral assemblage is dominated by pyrite and arsenopyrite, with minor chalcopyrite, galena, sphalerite, tetrahedrite, and micro-native gold. Weak alterations in Heihaibei granites include silicification and sericitization, with minor chloritization and carbonatization. The measured delta D-H2O and delta O-18(quartz) values of quartz in auriferous quartz veins range from -104.2 parts per thousand to -81.1 parts per thousand and +9.2 parts per thousand to +13.9 parts per thousand, respectively. The delta S-34 values of sulfides in auriferous quartz veins range from +7.60 parts per thousand to +8.65 parts per thousand, and the lead isotope compositions of sulfides in ores range from 18.7219 to 19.0007 for Pb-206/Pb-204, 15.6959 to 15.7062 for Pb-207/Pb-204, and 37.7359 to 38.8055 for Pb-208/Pb-204. The Pb isotope compositions of potassic feldspars from Heihaibei granites vary from 18.3532 to 19.4864 for Pb-206/Pb-204, 15.6475 to 15.6812 for Pb-207/Pb-204, and 37.1750 to 38.4598 for Pb-208/Pb-204. Collectively, the isotope (H, O, S, and Pb) geochemistry suggests that the ore-forming fluid was a special metamorphic water evolved from the deep slab-derived fluids, and the sulfur and lead were predominantly sourced from such metamorphic fluids, and from the deep parts of the Heihaibei granites. Therefore, the Heihaibei gold deposit can be classified as an orogenic gold deposit, which is closely associated with the subduction of the Paleo-Tethys oceanic plate, and even the final closure of this ocean by the Later Triassic.