Contribution of microbial processes to the enrichment of Middle Permian manganese deposits in northern Guizhou, South China

Economically important manganese deposits are hosted in the Middle Permian Maokou Formation of Zunyi, northern Guizhou, South China. During Permian, intense rifting related to initial stage Emeishan Large Igneous Province (ELIP) led development carbonate platforms and inter-platform troughs. The occur transitional zone between Previous studies emphasized that hydrothermal activities at bottom trough basin controlled formation deposits. In this study, new sedimentary, mineralogical, stable isotope evidence acquired from deposit, indicating microbially-mediated metallogenic mechanism also made an contribution for deposition. metallogenesis deposit is highly like combination microbial processes. Manganese ores Zunyi carbonate, showing massive clastic structures, no macroscopic nor microscopic lamination found, samples coarse-grained, diagenetically recrystallized with abundant mineralized microfossil biosignatures. FTIR, EPMA, Raman analyses recognize micrometer-scale cyclic mineralogical assembly help reconstruct proposed model metallogenesis. Hydrothermal activity provided dissolved Mn2+ ions into anoxic basal watermass. syngenetic stage, systems could be subdivided three categories: (1) cyanobacterial system, (2) Mn-biomat system (3) Fe-biomat system. Cyanobacterial precipitation calcite, it partially affected by Mn-metasomatism transformed Mn-bearing calcite. Mn-oxidizing microbes bio-oxide (δ-MnO2) near redoxcline basin. was responsible Fe-oxides (hematite) Fe-hydroxides (ferrihydrite lepidocrocite). After burial, oxides reacted organic matter sediments through processes during early diagenesis jointly contributed diagenetic ore. redox fluctuations oxic/suboxic zones re-oxidation process resulted marcasite. Anatase cycles observed were interpreted as product