Thermochemical oxidation of methane by manganese oxides in hydrothermal sediments

Abstract Microbial anaerobic oxidation of methane coupled to the reduction Mn(IV)-oxides, typically MnO 2 , derived from continental weathering and riverine transport has been proposed as a globally important sink methane. However, potential role hydrothermal Mn(IV) oxide-rich sediments sink, mechanisms underpinning at high-temperature fields remain poorly understood. Here, we report occurrence almost pure rhodochrosite with extremely negative δ 13 C PDB values (as low –76.4‰) in direct association hausmannite formed through activity Late Triassic Heqing Mn deposit Southern China. Based on detailed petrography geochemistry, this is interpreted result thermochemical by during early diagenesis. Given high 2+ CH 4 release sulfate concentration observed Archean oceans, propose that oxides may have effective sinks Earth’s ancient oceans.