The East Kunlun Orogen (EKO) is located in the western part of the Central Asian Orogenic Belt, and it records the Neoproterozoic–Early Devonian tectonic evolution involving subduction and extinction of the Proto-Tethys Ocean. Heihaibei granite is located in the South Kunlun belt within EKO. In this study, geochronology, geochemistry, and Hf isotope analysis of Heihaibei monzogranite and granodiorite were carried out. Their LA-ICP-MS zircon U-Pb results yielded ages of 414.1 ± 2.0 and 417.8 ± 2.0 Ma. The Heihaibei granite is peraluminous (A/CNK = 0.99–1.30), with high alkali contents (7.76–9.14 wt.%) and 10000 Ga/Al (2.60–3.38), FeO^T/MgO (27.6–49.5), and Y/Nb ratios (1.93–2.93), suggesting that the Heihaibei granite is an A₂-type granite. The Heihaibei granite samples have zircon εHf (t) values ranging from -6.3 to -0.3, which suggests that the Early Devonian granite was derived by partial melting of Mesoproterozoic (TDM₂ = 1797–1415 Ma) crust. When considering data on contemporaneous granites, geochronological and geochemical data for Heihaibei granite indicate that it was emplaced in a post-collisional extension environment following the closure of the Proto-Tethys Ocean. The Heihaibei granite was formed by extension of the southern subduction accretionary complex as part of the post-collisional setting during the closure of the Proto-Tethys Ocean.

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 δDH2O and δ18Oquartz values of quartz in auriferous quartz veins range from −104.2‰ to −81.1‰ and +9.2‰ to +13.9‰, respectively. The δ34S values of sulfides in auriferous quartz veins range from +7.60‰ to +8.65‰, and the lead isotope compositions of sulfides in ores range from 18.7219 to 19.0007 for 206Pb/204Pb, 15.6959 to 15.7062 for 207Pb/204Pb, and 37.7359 to 38.8055 for 208Pb/204Pb. The Pb isotope compositions of potassic feldspars from Heihaibei granites vary from 18.3532 to 19.4864 for 206Pb/204Pb, 15.6475 to 15.6812 for 207Pb/204Pb, and 37.1750 to 38.4598 for 208Pb/204Pb. 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.