Origin and Evolution of the Qingshan Pb–Zn Deposit, Northwestern Guizhou, SW China: Evidences from Fluid Inclusions and C–O–S–Pb Isotopes

The Qingshan lead–zinc (Pb–Zn) deposit in northwestern Guizhou Province is a structurally controlled, carbonate-hosted system formed from basin-derived hydrothermal processes. Geology, fluid inclusion, and isotopic data reveal a multi-stage hydrothermal circulation after Emeishan Large Igneous Province (ELIP, ~260 Ma) tectono-thermal reactivation within the Sichuan–Yunnan–Guizhu triangle (SYGT) area. Fluid inclusion microthermometry indicates that ore-forming fluids were derived from deep sources influenced by enhanced crustal heat flow linked with possible thermal input from Indo-Caledonian tectonic activity after ELIP. Ore-stage calcite records mixed carbon derived from marine carbonates with additional inputs from organic matter and deep-sourced fluids, reflecting carbonate dissolution and fluid–rock interaction. Sulfide, together with fluid inclusion temperatures > 120 °C, indicates sulfur derived from evaporitic sulfate reduced by thermochemical sulfate reduction (TSR); the heavy sulfur signature and partial isotopic disequilibrium among coexisting sulfides reflect dynamic fluid mixing during ore deposition. Lead isotopes indicate metallogenic metals were leached mainly from Devonian–Permian carbonates with subordinate basement input. Ore precipitated by cooling, depressurization, and mixing of metal-rich, H2S-bearing fluids in structurally confined zones where the carbonate–clastic interface effectively trapped ore-forming fluids, producing high-grade sphalerite–galena mineralization. Collectively, these data support a Huize-type (HZT) carbonate-hosted Pb–Zn genetic model for the Qingshan deposit.