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Science 20 June 2008:
Vol. 320. no. 5883, pp. 1620 - 1622
DOI: 10.1126/science.1157166
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Reports

Iron Isotope Fractionation During Magmatic Differentiation in Kilauea Iki Lava Lake

Fang-Zhen Teng,1*{dagger} Nicolas Dauphas,1 Rosalind T. Helz2

Magmatic differentiation helps produce the chemical and petrographic diversity of terrestrial rocks. The extent to which magmatic differentiation fractionates nonradiogenic isotopes is uncertain for some elements. We report analyses of iron isotopes in basalts from Kilauea Iki lava lake, Hawaii. The iron isotopic compositions (56Fe/54Fe) of late-stagemeltveins are 0.2 permil ({per thousand}) greater than values for olivine cumulates. Olivine phenocrysts are up to 1.2{per thousand} lighter than those of whole rocks. These results demonstrate that iron isotopes fractionate during magmatic differentiation at both whole-rock and crystal scales. This characteristic of iron relative to the characteristics of magnesium and lithium, for which no fractionation has been found, may be related to its complex redox chemistry in magmatic systems and makes iron a potential tool for studying planetary differentiation.

1 Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA.
2 United States Geological Survey, Reston, VA 20192, USA.

* Present address: Isotope Laboratory, Department of Geosciences and Arkansas Center for Space and Planetary Sciences, University of Arkansas, 113 Ozark Hall, Fayetteville, AR 72701, USA.

{dagger} To whom correspondence should be addressed. E-mail: fteng{at}uark.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Equilibrium Iron Isotope Fractionation at Core-Mantle Boundary Conditions.
V. B. Polyakov (2009)
Science 323, 912-914
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Science. ISSN 0036-8075 (print), 1095-9203 (online)