Geology and genesis of the Shenshuitan deposit in the Wulonggou gold district, Qinghai Province, China

Abstract

The Wulonggou gold district in the Eastern Kunlun region of Qinghai Province, China, hosts several gold deposits, yet the origin and nature of the ore-forming fluids remain debated. This study focuses on the Shenshuitan deposit in the Wulonggou gold district, integrating field observations with petrographic and geochemical analyses to constrain its genesis. Geological observations indicate that the deposit preserves three types alteration (skarn, propylitic and phyllic alteration). LA-ICP-MS U-Pb dating of hydrothermal garnet and magmatic zircon from the mineralization-related quartz diorite porphyry yielded ages of 220 ± 2 Ma and 218 ± 2 Ma, respectively. These overlapping ages indicate a close temporal relationship between magmatism and gold mineralization during the Late Triassic. The close spatial and temporal association among porphyry intrusion, alteration, and mineralization points to a magmatic-hydrothermal origin for the Shenshuitan deposit. The quartz diorite porphyry exhibits adakitic geochemical signatures and ε_Hf(t) values from −6 to −0.9, with two-stage model ages (TDM₂) ranging from 0.89 to 1.09 Ga. These features suggest the magma was derived from the partial melting of thickened, juvenile lower crust of Mesoproterozoic age. This magmatic event likely occurred in the post-collisional extensional setting following the closure of the Paleo-Tethys Ocean.