Magmatism and mineralization of the Niuxingba Ag–Pb–Zn deposit in the eastern Nanling metallogenic belt, South China: Constrains from zircon U–Pb and sphalerite Rb–Sr dating, geochemistry and H–O–S–Pb isotope geochemistry

The Niuxingba deposit, a recently discovered large-scale Ag–Pb–Zn deposit in the eastern Nanling metallogenic belt (NMB), South China, contains proven metal reserves of 124,982 tons Pb, 291,585 tons Zn, and 488.3 tons Ag. The orebodies mainly consist of vein-like sulfides, and occur in the volcanoclastic sedimentary rocks of Neoproterozoic Kuli Formation. The Ag–Pb–Zn orebodies yielded a sphalerite Rb-Sr isochronal age of 158.6 ± 2.2 Ma. Zircon LA–ICP–MS U–Pb dating revealed that the ore-related granodiorite porphyry was formed at 160.7 ± 1.9 Ma, suggesting the Late Jurassic magmatism and mineralization. Ore-related granodiorite porphyry at Niuxingba exhibits light hydrothermal alterations with loss on ignition values (LOI) of 4.62 %–7.07 %. The fluid immobile elements indicate that it is geochemically akin to the granitoids linked to Pb–Zn polymetallic mineralization in the NMB, and genetically belongs to weakly peraluminous high-K I-type granite. The Hf isotope compositions indicate that the magma probably originated from the partial melting of low crustal basement, with a minor contribution from juvenile crustal melts. H–O isotope characteristics indicate a magmatic source for ore-forming fluids, with less input from meteoric water. Additionally, the narrow δ³⁴S values (−3.8 ‰ to −0.3 ‰) of sulfides from mineralization stages II and IV are consistent with other Pb–Zn polymetallic deposits in the Shi-Hang Belt, suggesting a magmatic source. The Pb isotopic data indicate the ore-forming materials at Niuxingba derived from a crust-mantle mixing source. Combined with the regional tectonic setting, we propose that the Niuxingba deposit is a magmatic-hydrothermal deposit that formed in an extensional setting related to Paleo-Pacific plate subduction.