In-situ mineral chemistry, sulfur and lead isotopes, and paragenetic analysis to unravel the ore-forming processes in Qibaoshan Co-Ni-Cu-Pb-Zn deposit (Qin-Hang metallogenic belt, South China)

Cobalt and nickel are critical metals in high-demand for clean energy technologies, its occurrence in sediment-hosted deposits is mostly in association with Cu, but rare in association with Pb-Zn mineralization. The Qibaoshan deposit, located in the Qin-Hang metallogenic belt of western Jiangxi, South China, presents a unique case of stratiform Zn-Pb-Co-Ni-Cu mineralization hosted in Devonian-Carboniferous clastic-carbonate strata, with no exposed magmatic rocks. This study integrates in-situ mineral chemistry, sulfur and lead isotopes, and paragenetic analysis to unravel the ore-forming processes of this unusual polymetallic system. Results reveal two distinct mineralization events: (1) an earlier Pb-Zn stage driven by basin fluids heated by concealed magmatism, with metals and sulfur sourced from the metamorphic basement; and (2) a later Co-Cu-Ni stage linked to intermediate-mafic magmatic-hydrothermal fluids, introducing magma-derived sulfur and metals. Cobalt and nickel occur mainly as independent minerals, including sulfarsenide cobaltite, gersdorffite, diarsenide safflorite, rammelsbergite, loellingite, and triarsenide skutterudite, with minor substitution in pyrite and arsenopyrite. This study highlights a rare example of superimposed sediment-hosted base metal and critical metal mineralization, driven by dual fluid systems with contrasting sources. The findings challenge traditional models of sediment-hosted deposits and offer new insights into the diversity of cobalt enrichment mechanisms. The Qibaoshan deposit serves as a key natural laboratory for understanding metal coexistence, fluid evolution, and exploration targeting in complex polymetallic systems.