Bacteriogenic Origin of Secondary Minerals in Ohio Based on Carbon and Sulfur Isotope Compositions

Abstract

The origin of secondary minerals in northwestern Ohio has been attributed to a variety of causes including magmatic and bacterial activity. This research was conducted to determine whether secondary calcite, pyrite, sphalerite, galena, and celestite in Ohio result from bacterial processes. This combination of minerals is similar to those of Mississippi Valley type deposits, which have yielded economic wealth in other areas. The carbon isotope composition in secondary calcite establishes a link with petroleum by exhibiting S13C values of -21.5o/oo to -27.6o/oo. The δ34S values of sulfide minerals (-24.2o/oo to +7.0o/oo) demonstrate consistent depletion in the heavy sulfur isotope compared to coexisting sulfate minerals whose δ34S values range from +28.4%o/oo to +66.4o/oo. The isotope fractionation of carbon and sulfur minerals confirms that sulfurreducing bacteria metabolized hydrocarbons by means of oxygen derived by reduction of sulfate to sulfide. The CO2 and H2S released by bacteria resulted in the deposition of secondary carbonate and sulfide minerals in the rocks of northwestern Ohio.