--> Abstract: Microbial Mediation in Dolomite Formation During Carbonate Diagenesis; #90063 (2007)

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Microbial Mediation in Dolomite Formation During Carbonate Diagenesis

 

McKenzie, Judith A.1, Crisogono Vasconcelos1, Mónica Sánchez-Román1, Tomaso Bontognali1, Rolf Warthmann1 (1) ETH Zurich, Zurich, Switzerland

 

Understanding processes involved in dolomite formation under Earth's surface conditions has been a long-standing challenge for carbonate sedimentologists. Because dolomite bodies are often significant hydrocarbon reservoirs, much emphasis has been placed on the development of dolomite models to define the physico-chemical and hydrologic parameters involved in dolomitization. Nevertheless, these models have not been adequately calibrated for real-world circumstances because it was not possible to synthesis dolomite in the laboratory at Earth's surface temperatures. Now, with the recent recognition that specific microbes can mediate dolomite precipitation, it is possible to conduct culture experiments under controlled conditions to better define boundary parameters. The results of these experiments provide new information to interpret the conditions required for dolomite formation during carbonate diagenesis and necessitate a reinterpretation of currently applied models. For example, dolomite apparently does not nucleate in the fluids contained in open pore spaces, but precipitation occurs readily within an organic matrix (biofilm or EPS) produced by identifiable microbes. Factors, such as the optimum growth temperature for particular microbes under defined chemical conditions, are essential considerations for dolomite nucleation. In addition, geochemical proxies that have been used to interpret the paleoenvironment of dolomite formation, such as the Sr partition factor, are being redefined with these experimental studies. Further, using a geomicrobiologic approach to investigate natural dolomite-forming environments demonstrates that a diverse microbial community with various metabolic processes promotes dolomitization. Ultimately, microbes appear to be a powerful driving force behind carbonate diagenesis and must be included in any new model paradigm for dolomitization.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California