Microscale heterogeneity of Fe isotopes in >3.71 Ga banded iron formation from the Isua Greenstone Belt, southwest Greenland

Research Article| August 01, 2007 Microscale heterogeneity of Fe isotopes in >3.71 Ga banded iron formation from the Isua Greenstone Belt, southwest Greenland Martin J. Whitehouse; Martin J. Whitehouse 1Laboratory for Isotope Geology, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden Search for other works by this author on: GSW Google Scholar Christopher M. Fedo Christopher M. Fedo 2Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Martin J. Whitehouse 1Laboratory for Isotope Geology, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden Christopher M. Fedo 2Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, USA Publisher: Geological Society of America Received: 03 Dec 2006 Revision Received: 05 Mar 2007 Accepted: 23 Mar 2007 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2007) 35 (8): 719–722. https://doi.org/10.1130/G23582A.1 Article history Received: 03 Dec 2006 Revision Received: 05 Mar 2007 Accepted: 23 Mar 2007 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Martin J. Whitehouse, Christopher M. Fedo; Microscale heterogeneity of Fe isotopes in >3.71 Ga banded iron formation from the Isua Greenstone Belt, southwest Greenland. Geology 2007;; 35 (8): 719–722. doi: https://doi.org/10.1130/G23582A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We present Fe isotope compositions for magnetite crystals from >3.7 Ga banded iron formation (BIF) from the Isua Greenstone Belt and younger, spatially related pyrite obtained in situ by secondary ion mass spectrometry (SIMS). Across a distance of several millimeters, individual magnetite crystals of BIF show δ56Fe values up to 2‰, and within single magnetite-rich layers, there is a >2‰ range in δ56Fe. The highest positive δ56Fe values are consistent with those predicted by the equilibrium fractionation factor for oxidation of ferrous to ferric Fe in aqueous solution at a likely Early Archean ocean temperature of ∼70 °C, and further suggest that subsequent precipitation of ferric oxides was sufficiently slow that kinetic fractionation effects were minimal. These high values also imply that the supply of oxidant was limited. Heterogeneity in δ56Fe values is attributed to diagenetic reactions occurring in limited-volume pore waters, isolated from the bulk ocean (δ56Fe = 0‰), with development of isotope reservoir effects. Secondary pyrite in BIF and a conglomerate also show a distinct enrichment in heavy Fe isotopes, interpreted as redistribution and/or fractionation during postformational events. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.