The mineral, geochemical, and Fe-S isotopes data for Carboniferous-Permian karstic bauxites in China

Karstic bauxites were deposited in karstic depressions with varying paleogeographies and iron (Fe) concentrations. The mechanism of the iron cycle in paleokarstic areas is complex and remains poorly understood. We observed that Fe content in the Qingyuan and Mianchi deposits (continental interior and margin, respectively) increased downward along profiles, negatively correlating with δ⁵⁶Fe, which reflects Fe(II) release via reductive leaching. In contrast, the Pingguo deposit shows a positive Fe-Al correlation, suggesting co-enrichment of Fe and Al. Its δ⁵⁶Fe values vary slightly (~+0.08‰), indicating minimal Fe loss. Our results highlight non-uniform Fe leaching over paleokarstic surfaces, with implications for metallogenic efficiency and ecosystem dynamics.