Anaerobic methane oxidation and the formation of dolomite

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doi: 10.1016/j.epsl.2004.10.015
Author(s): Moore, T. S.; Murray, R. W.; Kurtz, A. C.; Schrag, D. P.
Author Affiliation(s): Primary:
Boston University, Department of Earth Sciences, Boston, MA, United States
Harvard University, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 229(1-2), p.141-154. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 66 refs.; illus., incl. 4 tables, sketch map
Summary: We examine the link between organic matter degradation, anaerobic methane oxidation (AMO), and sulfate depletion and explore how these processes potentially influence dolomitization. We determined rates and depths of AMO and dolomite formation for a variety of organic-rich sites along the west African Margin using data from Ocean Drilling Program (ODP) Leg 175. Rates of AMO are calculated from the diffusive fluxes of CH4 and SO4, and rates of dolomite formation are calculated from the diffusive flux of Mg. We find that the rates of dolomite formation are relatively constant regardless of the depth at which it is forming, indicating that the diffusive fluxes of Mg and Ca are not limiting. Based upon the calculated log IAP values, log Ksp values for dolomite were found to narrowly range between -16.1 and -16.4. Dolomite formation is controlled in part by competition between AMO and methanogenesis, which controls the speciation of dissolved CO2. AMO increases the concentration of CO32- through sulfate reduction, favoring dolomite formation, while methanogenesis increases the pCO2 of the pore waters, inhibiting dolomite formation. By regulating the pCO2 and alkalinity, methanogenesis and AMO can regulate the formation of dolomite in organic-rich marine sediments. In addition to providing a mechanistic link between AMO and dolomite formation, our findings provide a method by which the stability constant of dolomite can be calculated in modern sediments and allow prediction of regions and depth domains in which dolomite may be forming. Abstract Copyright (2004) Elsevier, B.V.
Year of Publication: 2004
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 06 Petrology, Sedimentary; Africa; Aliphatic hydrocarbons; Alkanes; Anaerobic environment; Angola Basin; Atlantic Ocean; C-13/C-12; Cape Basin; Carbon; Carbon dioxide; Carbonates; Chemical composition; Chemical fractionation; Chemical reactions; Continental margin sedimentation; Degradation; Diagenesis; Dolomite; Geochemistry; Hydrocarbons; Isotope ratios; Isotopes; Leg 175; Marine sedimentation; Marine sediments; Mass spectra; Methane; Namibia; ODP Site 1081; ODP Site 1082; ODP Site 1084; Ocean Drilling Program; Organic compounds; Oxidation; Precipitation; Sedimentation; Sediments; South Atlantic; Southern Africa; Spectra; Stable isotopes; Sulfates; Walvis Ridge
Coordinates: S253049 S253049 E0130140 E0130140
S193712 S193712 E0111910 E0111910
Record ID: 2006016268
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands