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Geochimica et Cosmochimica Acta 89 (2012) 31-45
Iron isotope fractionation in planetary crusts
Kun Wang ( ) 1, Frédéric Moynier 1, Nicolas Dauphas 2, Jean-Alix Barrat 3, Paul Craddock 2, Corliss K. Sio 2
(04/07/2012)

We present new high precision iron isotope data (δ56Fe vs. IRMM-014 in per mil) for four groups of achondrites: one lunar meteorite, 11 martian meteorites, 32 howardite-eucrite-diogenite meteorites (HEDs), and eight angrites. Angrite meteorites are the only planetary materials, other than Earth/Moon system, significantly enriched in the heavy isotopes of Fe compared to chondrites (by an average of +0.12‰ in δ56Fe). While the reason for such fractionation is not completely understood, it might be related to isotopic fractionation by volatilization during accretion or more likely magmatic differentiation in the angrite parent-body. We also report precise data on martian and HED meteorites, yielding an average δ56Fe of 0.00 ± 0.01‰. Stannern-trend eucrites are isotopically heavier by +0.05‰ in δ56Fe than other eucrites. We show that this difference can be ascribed to the enrichment of heavy iron isotopes in ilmenite during igneous differentiation. Preferential dissolution of isotopically heavy ilmenite during remelting of eucritic crust could have generated the heavy iron isotope composition of Stannern-trend eucrites. This supports the view that Stannern-trend eucrites are derived from main-group eucrite source magma by assimilation of previously formed asteroidal crust. These new results show that iron isotopes are not only fractionated in terrestrial and lunar basalts, but also in two other differentiated planetary crusts. We suggest that igneous processes might be responsible for the iron isotope variations documented in planetary crusts.
1 :  McDonnell Center for the Space Sciences
Washington University in Saint-Louis
2 :  Origins Laboratory
University of Chicago
3 :  Domaines Océaniques
INSU – Institut d'écologie et environnement – Institut Universitaire Européen de la Mer (IUEM) – Université de Bretagne Occidentale (UBO) – Observatoire des Sciences de l'Univers – CNRS : UMR6538
Planète et Univers/Sciences de la Terre/Géochimie

Sciences de l'environnement/Milieux et Changements globaux

Planète et Univers/Sciences de la Terre/Planétologie
RARE-EARTH ELEMENTS – EUCRITE PARENT BODY – LUNAR METEORITES – MASS-SPECTROMETRY – MAGMATIC DIFFERENTIATION – EXPERIMENTAL CALIBRATION – REDOX CONDITIONS – PETROLOGY – GEOCHEMISTRY – MANTLE
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