Chromite oxidation by manganese oxides in subseafloor basalts and the presence of putative fossilized microorganisms

Geochemical Transactions

Research Article

Nils G Holm¹  Curt Broman¹  Magnus Ivarsson² 

[1] Department of Geological Sciences, Stockholm University, SE-106 91, Stockholm, Sweden;Department of Palaeozoology, Swedish Museum of Natural History, Box 50007, SE-104 05, Stockholm, Sweden;

关键词: Chromite;    Manganese Oxide;    Ocean Drill Program;    Filamentous Structure;    Rhodochrosite;   

DOI  :  10.1186/1467-4866-12-5

 received in 2010-09-16, accepted in 2011-06-03,  发布年份 2011

来源: Springer

【 摘 要 】

Chromite is a mineral with low solubility and is thus resistant to dissolution. The exception is when manganese oxides are available, since they are the only known naturally occurring oxidants for chromite. In the presence of Mn(IV) oxides, Cr(III) will oxidise to Cr(VI), which is more soluble than Cr(III), and thus easier to be removed. Here we report of chromite phenocrysts that are replaced by rhodochrosite (Mn(II) carbonate) in subseafloor basalts from the Koko Seamount, Pacific Ocean, that were drilled and collected during the Ocean Drilling Program (ODP) Leg 197. The mineral succession chromite-rhodochrosite-saponite in the phenocrysts is interpreted as the result of chromite oxidation by manganese oxides. Putative fossilized microorganisms are abundant in the rhodochrosite and we suggest that the oxidation of chromite has been mediated by microbial activity. It has previously been shown in soils and in laboratory experiments that chromium oxidation is indirectly mediated by microbial formation of manganese oxides. Here we suggest a similar process in subseafloor basalts.

【 授权许可】

CC BY   
© Ivarsson et al; licensee Chemistry Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.