Formation of magnetite and iron-rich carbonates by thermophilic iron-reducing bacteria

Chuanlun Zhang; Hojatollah Vali; Shi Liu; Yul Roh; Dave Cole; Joseph L. Kirschvink; Tullis C. Onstott; David S. McKay; Tommy James Phelps

doi:10.1117/12.278809

11 July 1997 Formation of magnetite and iron-rich carbonates by thermophilic iron-reducing bacteria

Chuanlun Zhang, Hojatollah Vali, Shi Liu, Yul Roh, Dave Cole, Joseph L. Kirschvink, Tullis C. Onstott, David S. McKay, Tommy James Phelps

Author Affiliations +

Proceedings Volume 3111, Instruments, Methods, and Missions for the Investigation of Extraterrestrial Microorganisms; (1997) https://doi.org/10.1117/12.278809
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

Abstract

Laboratory experiments were performed to study the formation of iron minerals by a thermophilic (45 - 75 degree(s)C) fermentative iron-reducing bacterial culture (TOR39) obtained from the deep subsurface. Using amorphous Fe(III) oxyhydroxide as an electron acceptor and glucose as an electron donor, TOR39 produced magnetite and iron-rich carbonates at conditions consistent, on a thermodynamic basis, with Eh (-200 mV to -415 mV) and pH (6.2 to 7.7) values determined for these experiments. Analyses of the precipitating solid phases by X-ray diffraction showed that the starting amorphous Fe(III) oxyhydroxide was nearly completely converted to magnetite and Fe-rich carbonate after 20 days of incubation. Increasing bicarbonate concentration in the chemical milieu resulted in increased proportions of siderite relative to magnetite and the addition of MgCl₂ caused the formation of magnesium-rich carbonate in addition to siderite. The results suggest that the TOR39 bacterial culture may have the capacity to form magnetite and iron-rich carbonates in a variety of geochemical conditions. These results may have significant implications for studying the past biogenic activities in the Martian meteorite ALH84001.

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Chuanlun Zhang, Hojatollah Vali, Shi Liu, Yul Roh, Dave Cole, Joseph L. Kirschvink, Tullis C. Onstott, David S. McKay, and Tommy James Phelps "Formation of magnetite and iron-rich carbonates by thermophilic iron-reducing bacteria", Proc. SPIE 3111, Instruments, Methods, and Missions for the Investigation of Extraterrestrial Microorganisms, (11 July 1997); https://doi.org/10.1117/12.278809

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