Rogers, Jennifer Roberts¹, Luis A. Gonzalez¹, G. L. Macpherson¹ 
(1) University of Kansas, Lawrence, KS

ABSTRACT: Microbial Precipitation of Dolomite in Methanogenic Groundwater

We report the microbial precipitation of dolomite at low temperature in dilute natural waters from both field and laboratory experiments. In a freshwater aquifer we observe microorganisms colonizing basalt and nucleating secondary non-stoichiometric dolomite on their cell walls. These observations were confirmed in the laboratory where ordered dolomite formed at near equilibrium conditions from groundwater with dissolved molar Mg:Ca ratios <1, whereas dolomite was absent in sterile experiments. Geochemical and microbiological data suggest that methanogenic microorganisms are the dominant metabolic guild in this system and are integral to precipitation of the dolomite. We hypothesize that the attached microbial consortium perturbs the geochemical environment at the basalt surface, releasing Mg and Ca that drive dolomite precipitation after nucleating on the microbial cell membrane. These findings offer insight into the long-standing dolomite problem and suggest an important role for microbial processes in formation of dolomite across a wide range of environmental conditions.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.