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Demonstration of significant abiotic iron isotope fractionation in nature

Thomas D. Bullen, Arthur F. White, Cyril W. Childs, Davisson V. Vivit and Marjorie S. Schulz
Demonstration of significant abiotic iron isotope fractionation in nature
Geology (Boulder) (August 2001) 29 (8): 699-702


Field and laboratory studies reveal that the mineral ferrihydrite, formed as a result of abiotic oxidation of aqueous ferrous to ferric Fe, contains Fe that is isotopically heavy relative to coexisting aqueous Fe. Because the electron transfer step of the oxidation process at pH >5 is essentially irreversible and should favor the lighter Fe isotopes in the ferric iron product, this result suggests that relatively heavy Fe isotopes are preferentially partitioned into the readily oxidized Fe(II)(OH) (sub x(aq)) species or their transition complexes prior to oxidation. The apparent Fe isotope fractionation factor, alpha (sub ferrihydrite-water) , depends primarily on the relative abundances of the Fe(II) (sub (aq)) species. This study demonstrates that abiotic processes can fractionate the Fe isotopes to the same extent as biotic processes, and thus Fe isotopes on their own do not provide an effective biosignature.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 29
Serial Issue: 8
Title: Demonstration of significant abiotic iron isotope fractionation in nature
Affiliation: U. S. Geological Survey, Menlo Park, CA, United States
Pages: 699-702
Published: 200108
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 17
Accession Number: 2001-076333
Categories: Isotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2001083
Illustration Description: illus.
Secondary Affiliation: Victoria University, NZL, New Zealand
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200124
Program Name: USGSOPNon-USGS publications with USGS authors
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