Microbial metallogenesis of early carboniferous manganese deposit in central Guangxi, South China

Manganese deposits in the Early Carboniferous Baping Formation of central Guangxi, South China were formed Youjiang Basin on southern passive margin Block. Hosted Second Member Formation, manganese ore layers interbedded by thin-middle carbonate and silicified carbonate. Previous studies provide limited information about this deposit, sedimentary characteristics ores metallogenic mechanism are not clear. In study, integrated analyses petrology, mineralogy, geochemistry, carbon isotope reveal microbial metallogenesis deposit Guangxi for first time. Oncoid-bearing massive Mn laminated contain evidence disseminated mineralized biosignatures millimeter scale. An situ mineralogical study based CL, FTIR, SEM-EDS Raman spectroscopy has identified syngenetic diagenetic Fe systems during formation deposit. Both biomats precipitated micro-laminae microbiogenic minerals such as Mn-calcite, rhodochrosite, kutnohorite, apatite. The model can be divided into two main stages: (1) Sediment accumulation stage, where enzymatic Mn(II) oxidation controlled oxides within cyanobacterial organic network, thus enriching manganese; (2) Diagenetic Mn-metasomatism reaction between matter led to precipitation proto-ore (Ca-rhodochrosite). A positive ?13C value (+1.53‰) sample negative values (?7.15‰ ?3.64‰) samples indicate participation alkalinity source Mn-bearing carbonates. presence kutnohorite Mn-sulfide indicates a transitional zone suboxic anoxic conditions. Anatase represents mineral Fe-biomat. After release elements decomposed cells EPS, series accessory (feldspar, apatite, pyrite, etc.) formed.