Discovery of the Bulakebashiquanbei Skarn Cu-Au-W Mineralization in the Western Segment of East Kunlun Orogenic Belt, NW China, and Its Exploration Significance

The Bulakebashiquanbei Cu-Au-W occurrence is a newly discovered skarn-type mineralization occurrence in the peripheral area of the Qukulekedong ore cluster, the western segment of the East Kunlun Orogenic Belt. To precisely constrain the timing of magmatism and mineralization, characterize the nature of the ore-related magma, and evaluate its regional exploration significance, this study conducted zircon and garnet U-Pb geochronology of the diorite and skarn, together with whole-rock major and trace element analyses and zircon trace element analyses of the diorite. The results show that the diorite yields a zircon ²⁰⁶Pb/²³⁸U weighted mean age of (209.4±1.8) Ma, whereas garnet from the skarn yields a common-Pb-corrected ²⁰⁶Pb/²³⁸U weighted mean age of (209.1±1.1) Ma. These ages overlap within analytical uncertainties, indicating that diorite emplacement and skarn-type Cu-Au-W mineralization were broadly coeval and occurred during the Late Triassic post-collisional extensional stage. Whole-rock geochemical characteristics indicate that the ore-related dioritic magma was mainly derived from partial melting of lithospheric mantle metasomatized by subduction-related components and subsequently underwent a certain degree of fractional crystallization. Zircon trace element data yield ΔFMQ values of −1.89 to 0.16 and 10000×(Eu/Eu*)/Yb_N ratios of 0.66–4.48, indicating that the magmatic system was generally reduced to near the FMQ buffer and had moderate to relatively high water contents. The discovery of the Bulakebashiquanbei occurrence demonstrates that, in addition to the previously recognized magmatic-hydrothermal vein-type Au-Sb mineralization, the Qukulekedong ore cluster and its surrounding areas also host skarn-type Cu-Au-W mineralization associated with late Triassic dioritic magmatism and contact metasomatism with carbonate rocks, further expanding the recognized mineralization styles of the regional magmatic-hydrothermal system. Future exploration should focus on the margins of concealed Late Triassic intermediate to felsic intrusions, contacts between intrusions and carbonate rocks, and their intersections with fault structures, with particular attention to the potential for Au-W mineralization.