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Science 13 February 2009:
Vol. 323. no. 5916, pp. 912 - 914
DOI: 10.1126/science.1166329
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Reports

Equilibrium Iron Isotope Fractionation at Core-Mantle Boundary Conditions

Veniamin B. Polyakov

The equilibrium iron isotope fractionation between lower mantle minerals and metallic iron at core-mantle boundary conditions can be evaluated from the high-pressure 57Fe partial vibrational density of states determined by synchrotron inelastic nuclear resonant x-ray scattering spectroscopy using a diamond anvil. Ferropericlase [(Mg,Fe)O] and (Fe,Mg)SiO3–post-perovskite are enriched in heavy iron isotopes relative to metallic iron at ultrahigh pressures, as opposed to the equilibrium iron isotope fractionation between these compounds at low pressure. The enrichment of Earth and Moon basalts in heavy iron isotopes relative to those from Mars and asteroid Vesta can be explained by the equilibrium iron isotope fractionation during the segregation of Earth's core and the assumption that Earth was already differentiated before the Moon-forming "giant impact."

Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow Region, Russia. E-mail: polyakov{at}iem.ac.ru

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
How Did Earth Accrete?.
A. N. Halliday and B. J. Wood (2009)
Science 325, 44-45
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