Fluid Spatiotemporal Evolution in the Zhaxikang PbZnSb Polymetallic Deposit: Materialization of the Metallogenic Model

The Zhaxikang Pb-Zn-Sb deposit is a typical deposit in the Northern Himalayan metallogenic belt, but a long-standing coexistence of various genetic interpretations (magmatic-hydrothermal, exhalative-sedimentary, hot spring, etc.) has restricted the synthesis of metallogenic regularities and exploration deployment. Our previous work established a "Zhaxikang-type" tectono-magmatic coupling metallogenic model, providing a research direction that can accommodate different genetic views. However, direct evidence regarding the migration path, temporal evolution sequence, and precipitation mechanism of the ore-forming fluids remains lacking, which hinders the refinement of the model and a deeper understanding of the deposit genesis. To address this issue, this paper presents: (1) a comparison of fluid inclusion temperature and salinity between the regional F1-1 fault and the deposit; (2) analysis of Fe and In contents in sphalerite from different mineralization stages; and (3) in-situ sulfur isotope analysis of zoned Fe-Mn carbonate-sphalerite-pyrite assemblages. The results show that: (1) quartz inclusions in the F1-1 fault (18.9 Ma) have significantly higher temperatures (250–450°C) and salinities (0–17%) than those in the deposit (180–336°C, 2–12%), indicating fluid migration from the regional fault to secondary ore-hosting faults; (2) from the Pb-Zn stage (43.1 Ma) to the Sb stage (17.9–12.2 Ma), Fe content in sphalerite decreases from ~8.5% to ~2.2%, and In content from 71.8 ppm to 1.8 ppm, indicating decreasing temperature and reflecting regional tectonic uplift that drove the fluid transition from a magmatic endmember to a meteoric water endmember; (3) in the zoned textures, sphalerite δ³⁴S is consistently higher than that of pyrite (sulfur isotope disequilibrium), confirming rapid mixing and precipitation of a Zn- and S²⁻-rich (heavy sulfur) magmatic fluid and a SO₄²⁻-, Fe-, Mn-rich (light sulfur) Fe-Mn carbonate fluid under a "seismic pump" mechanism. These lines of evidence materialize the metallogenic model from three dimensions: spatial migration, temporal evolution, and dynamic mechanism. Furthermore, by reinterpreting previous data and integrating various genetic views within the model, we demonstrate its compatibility, self-consistency, and applicability to distal deposits, providing a new paradigm for understanding long-distance fluid migration and mineralization in collisional orogens.