Microbial Alkalinity Production and Silicate Alteration in Methane Charged Marine Sediments: Implications for Porewater Chemistry and Diagenetic Carbonate Formation

• DOI: 10.3389/feart.2021.756591
• Publication Date: 2022-01-17T06:45:26Z
• Authors: Patrick Meister; Gerhard Herda; Elena Petrishcheva; Susanne Gier; Gerald R. Dickens; Christian Bauer; Bo Liu
• Keywords: Alkalinity; Carbonate minerals

A numerical reaction-transport model was developed to simulate the effects of microbial activity and mineral reactions on composition porewater in a 230-m-thick Pleistocene interval drilled Peru-Chile Trench (Ocean Drilling Program, Site 1230). This site has profiles similar those along many continental margins, where intense methanogenesis occurs alkalinity surpasses 100 mmol/L. Simulations show that sulphate reduction, anaerobic oxidation methane, ammonium release from organic matter degradation only account for parts total alkalinity, excess CO 2 produced during leads acidification porewater. Additional is by slow alteration primary aluminosilicate minerals kaolinite SiO . Overall, production methanogenic zone sufficient prevent dissolution carbonate minerals; indeed, it contributes formation cemented layers at supersaturation front near sulphate-methane transition zone. Within zone, largely inhibited cation diffusion but rapidly if cations are transported into via fluid conduits, such as faults. The simulation presented here provides fundamental insight diagenetic deep biosphere may also be applicable long-term prediction stability safety storage reservoirs.