Journal article

Publication year: 2017

Pages: 209-225

Journal: Geochimica et Cosmochimica Acta

Volume number: 214

ISSN: 0016-7037

DOI Link: https://doi.org/10.1016/j.gca.2017.07.027

Publisher: Elsevier

Abstract: 
It was proposed to utilize siderite FeCO3 in mid to late Archaean Superior type banded as a proxy to constrain the CO2 partial pressure of Archaean atmospheres. Implicit in this proposition is that siderite was a primary carbonate mineral that crystallized directly from Fe2+ enriched Archaean seawater, in equilibrium with atmospheric CO2. To our knowledge that proposition has not been demonstrated to be valid. We test with water-gas exchange experiments under controlled CO2 partial pressures if siderite can be stabilized as a primary mineral in Fe2+ bearing seawater. Reduced seawater proxies enriched in Fe2+ and Mn2+ are equilibrated with reduced N-2-CH4-CO2-H-2 gas phases with variable CO2. The solid phases stabilized in Fe2+ enriched water compositions are amorphous ferrous iron hydroxy carbonates. Crystalline siderite FeCO3 is not found to be a stable phase. The phases precipitating from Mn2+ enriched water include crystalline rhodochrosite MnCO3 and possibly amorphous Mn-enriched phases. Based on these results we advise against using siderite in banded iron formations as a CO2 sensor for the Archaean atmosphere. (C) 2017 Elsevier Ltd. All rights reserved.

Harvard Citation style: Gab, F., Ballhaus, C., Siemens, J., Heuser, A., Lissner, M., Geisler, T., et al. (2017) Siderite cannot be used as CO2 sensor for Archaean atmospheres, Geochimica et Cosmochimica Acta, 214, pp. 209-225. https://doi.org/10.1016/j.gca.2017.07.027

APA Citation style: Gab, F., Ballhaus, C., Siemens, J., Heuser, A., Lissner, M., Geisler, T., & Garbe-Schönberg, D. (2017). Siderite cannot be used as CO2 sensor for Archaean atmospheres. Geochimica et Cosmochimica Acta. 214, 209-225. https://doi.org/10.1016/j.gca.2017.07.027