Geochemical Characteristics and Ore Genesis of the Muhu Manganese Deposit in the Eastern Segment of Markansu Metallogenic Zone, Western Kunlun Mountains, Northwest China

The complex geochemical behaviors of manganese (Mn) enrichment processes remain insufficiently understood, which hinders a deeper understanding of the formation mechanism of sedimentary Mn deposits. A systematic geochemical analysis of a continuous drill-core profile is very important for understanding the Mn enrichment process. This study focuses on the Muhu large Mn deposit, located in the eastern segment of the Markansu metallogenic belt, western Kunlun Mountains. The vertical changes of Mn ore, Mn-bearing black rocks, and wall rocks were systematically evaluated through a single-borehole core section, including their geological characteristics, lithogeochemistry, and paleoenvironmental indicators, revealing the ore genesis of the Muhu deposit. The results indicate that during the initial Mn deposition in the Muhu area, the geochemical environment was relatively oxidized, with relatively high paleosalinity, comparatively low primary productivity, and a relatively deep redox interface. The sedimentary basin was influenced by open-marine seawater and accompanied by the input of hydrothermal materials. The redox conditions of basin waters likely played an important role in controlling the geochemical behavior of Mn cycling, and these oxides initially enriched were subsequently reduced in the presence of organic matter, ultimately contributing to the formation of Mn carbonate ore. Accordingly, a three-stage process of “oxidation–reduction–mineralization” is proposed for the Muhu (Markansu) Mn carbonate deposit. This refined evolutionary model provides further constraints for understanding the metallogenic mechanism of marine sedimentary Mn deposits.