title: Iron isotopic fractionation between silicate mantle and metallic core at high pressure.
abstract: The +0.1‰ elevated56Fe/54Fe ratio of terrestrial basalts relative to chondrites was proposed to be a fingerprint of core-mantle segregation. However, the extent of iron isotopic fractionation between molten metal and silicate under high pressure-temperature conditions is poorly known. Here we show that iron forms chemical bonds of similar strengths in basaltic glasses and iron-rich alloys, even at high pressure. From the measured mean force constants of iron bonds, we calculate an equilibrium iron isotope fractionation between silicate and iron under core formation conditions in Earth of ∼0-0.02‰, which is small relative to the +0.1‰ shift of terrestrial basalts. This result is unaffected by small amounts of nickel and candidate core-forming light elements, as the isotopic shifts associated with such alloying are small. This study suggests that the variability in iron isotopic composition in planetary objects cannot be due to core formation.
authors.affiliation: Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Jin
authors.identifier: 0000-0002-1670-8199
authors.initials: J
authors.lastname: Liu
authors.affiliation: Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637, USA.
authors.forename: Nicolas
authors.identifier: 0000-0002-1330-2038
authors.initials: N
authors.lastname: Dauphas
authors.affiliation: IMPMC-UMR CNRS 7590, Sorbonne Universités, UPMC, IRD, MNHN, Muséum National d'Histoire Naturelle, 61 rue Buffon, 75005 Paris, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Roskosz
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Hu
authors.affiliation: Center for High Pressure Science and Technology Advanced Research (HPSTAR), Pudong, Shanghai 201203, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.|Department of Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Wenli
authors.initials: W
authors.lastname: Bi
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Jiyong
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Esen E
authors.initials: EE
authors.lastname: Alp
authors.affiliation: Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637, USA.
authors.forename: Justin Y
authors.initials: JY
authors.lastname: Hu
authors.affiliation: Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78712, USA.|Center for High Pressure Science and Technology Advanced Research (HPSTAR), Pudong, Shanghai 201203, China.
authors.forename: Jung-Fu
authors.initials: JF
authors.lastname: Lin