Date of Award

January 2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Stephan H. Nordeng

Abstract

New approaches in carbonate geochemistry are aiding geoscientists in

understanding dolomite formation. Dolomite is largely absent in modern depositional

environments but is present in ancient rocks. The current problem is the inability to

synthesize it under low-temperature conditions in the laboratory. Until recently

laboratory preparation of dolomite required elevated temperatures (<100oC) to overcome

kinetic barriers. One novel approach involves using bacteria to overcome the kinetic

barriers that have frustrated efforts to synthesize dolomite at near surface temperatures.

This study presents preliminary results of experiments in which three strains of bacteria

were used to inoculate a magnesium deficient amorphous calcium carbonate (Mg-ACC)

medium (CO3

2-: Mg2+: Ca2+ in 2:1:1 ratio). The bacteria used include an aerobic strain,

Virgibacillus marismortui (ATCCÎ 700626™) and two anaerobic strains, Desulfovibrio

desulfuricans subsp. deslufuricans (ATCCβ9577™) and Escherichia coli. All the

experiments were conducted at 30oC and 37˚C for 40 days. Preliminary XRD results are

consistent with the precipitation of a carbonate phase with a dolomite-like XRD peak

near 31˚ 2θ, Cu kα radiation. Similar peaks were not apparent for the experiments using

the aerobic strain nor the bacteria free control. These results indicate that the two strains

of anaerobic bacteria may aid in the formation of a magnesium-rich carbonate phase

similar to dolomite at low temperature, within short periods of time.

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