Sedimentary facies control on Mn-carbonate mineral precipitation pathways in the Middle Permian Qiling Basin, South China

• Black shale/limestone-hosted Mn ores were developed in the Qiling Basin; • Contribution of organic-derived DIC influenced δ 13 C carb values of Mn-carbonate; • Mn sourced from contemporaneous hydrothermal activity related to ELIPs; • Sedimentary facies determined Mn-carbonate formation in porewater or water column; During the Middle Permian, a large-scale NE–SW-trending manganese metallogenic belt developed within the South China Block. Recent exploration in the Gufeng Formation of the Qiling Basin (southwestern Hunan Province, China) has discovered Mn ore resources exceeding 100 million tons. However, the pronounced lithological heterogeneity of the Mn-bearing strata has hindered a comprehensive understanding of their metallogenic mechanisms. In this study, sedimentological, mineralogical, and geochemical analyses were conducted on three newly drilled cores from the Qiling Basin Mn deposits to elucidate the precipitation pathways of Mn-carbonate minerals. Two distinct Mn-carbonate types were identified: (i) Black shale-hosted type (ZK008), deposited in a basinal environment, characterized by high TOC, negative Ce anomalies, elevated Y/Ho ratios, hat-shaped REE patterns, and low δ 13 C carb values; (ii) Limestone-hosted type (ZK002 and ZK5903), deposited in a slope setting, showing lower TOC, positive Ce anomalies, reduced Y/Ho ratios, hat-shaped to left-inclined REE patterns, and higher δ 13 C values. Both Mn ore types were formed under anoxic conditions, as indicated by the enrichment of redox-sensitive elements. Elemental discrimination diagrams and positive TOC–δ 13 C carb correlations suggest that Mn and carbon primarily originated from hydrothermal fluids and organic-derived dissolved inorganic carbon (DIC), respectively. Notably, a negative TOC–δ 13 C carb relationship was observed only in the black shale-hosted Mn-carbonates, which are dominated by kutnohorite (Ca, Mn) CO 3 and commonly nucleated around diagenetic pyrite and foraminiferal shells. In contrast, rhodochrosite (MnCO 3 ) is the predominant Mn-bearing mineral phase in the limestone-hosted type, where residual calcite acted as a major nucleation substrate. Based on these findings, precipitation mechanisms are proposed for the two Mn-carbonate types: (i) Black shale-hosted: precipitation of Mn-carbonate through the coupling of hydrothermal Mn 2+ and organic-derived DIC in anoxic porewaters; (ii) Limestone-hosted: initial Mn redox cycling in shallow slope environments, followed by Mn 2+ binding with both organic-derived (primary) and calcite redissolution-derived DIC in an anoxic water column. Overall, the Gufeng Mn deposits record a complex interplay among hydrothermal inputs, marine anoxia, organic matter oxidation, and Mn cycling. Variations in sedimentary facies exerted first-order control on Mn-carbonate precipitation pathways, allowing the coexistence of multiple formation mechanisms within a single depositional basin.