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Microbial mediation of iron mobilization and deposition in iron formations since the early Precambrian

D. Ann Brown
Microbial mediation of iron mobilization and deposition in iron formations since the early Precambrian (in Evolution of early Earth's atmosphere, hydrosphere, and biosphere; constraints from ore deposits, Stephen E. Kesler (editor) and Hiroshi Ohmoto (editor))
Memoir - Geological Society of America (2006) 198: 239-256

Abstract

It is suggested that sedimentary deposition of iron in sediments from the Archean to the present day can be attributed largely to microbial mediation. Results from laboratory experiments, using a microbial consortium enriched from the source of a biofilm growing on a rock face in an underground research laboratory, are used to advance a plausible explanation for the mobilization, precipitation, transport, and deposition of iron. The consortium produces its own local environments independent of the prevailing atmosphere. It is able to extract iron from minerals such as biotite and magnetite, as well as from a chelated solution; this iron is then metabolized, mainly through dissimulatory iron reduction, to provide cell energy, after which it is immediately precipitated. All organisms require energy for growth and reproduction, but because iron redox reactions are inefficient a large amount of iron must be processed, either directly through metabolism or indirectly due to the local microbial redox microenvironment, with the result that vast quantities accumulate as waste. This precipitate could be the main source of iron in sedimentary iron formations. Siderite and ferrihydrite, the main precipitates, may occur in close juxtaposition within a biofilm. The oxidation state of the iron precipitate is controlled by the nutrient supply, which in turn influences the metabolism of the biofilm organisms and hence their redox. Subsequently, this iron, enmeshed within the biofilm, is either deposited in sediments as fine layers or rolled by wave or current action into particles and granules, which can form structures similar to those found in banded iron formations (BIFs).


ISSN: 0072-1069
Coden: GSAMAQ
Serial Title: Memoir - Geological Society of America
Serial Volume: 198
Title: Microbial mediation of iron mobilization and deposition in iron formations since the early Precambrian
Title: Evolution of early Earth's atmosphere, hydrosphere, and biosphere; constraints from ore deposits
Author(s): Brown, D. Ann
Author(s): Kesler, Stephen E.editor
Author(s): Ohmoto, Hiroshieditor
Affiliation: University of Manitoba, Department of Geological Sciences, Winnipeg, MB, Canada
Affiliation: University of Michigan, Department of Geological Sciences, Ann Arbor, MI, United States
Pages: 239-256
Published: 2006
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 0-8137-1198-3
References: 97
Accession Number: 2007-006051
Categories: Sedimentary petrologyStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: Pennsylvania State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200703
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