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    Magnesium isotope evidence that accretional vapour loss shapes planetary compositions

    Hin, R. and Coath, C. and Carter, P. and Nimmo, F. and Lai, Y.-J. and Pogge von Strandmann, Philip A.E. and Willbold, M. and Leinhardt, Z. and Walter, M. and Elliott, T. (2017) Magnesium isotope evidence that accretional vapour loss shapes planetary compositions. Nature 549 , pp. 511-514. ISSN 0028-0836.

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    Abstract

    It has long been recognized that Earth and other differentiated planetary bodies are chemically fractionated compared to primitive, chondritic meteorites and, by inference, the primordial disk from which they formed. However, it is not known whether the notable volatile depletions of planetary bodies are a consequence of accretion1 or inherited from prior nebular fractionation2. The isotopic compositions of the main constituents of planetary bodies can contribute to this debate3, 4, 5, 6. Here we develop an analytical approach that corrects a major cause of measurement inaccuracy inherent in conventional methods, and show that all differentiated bodies have isotopically heavier magnesium compositions than chondritic meteorites. We argue that possible magnesium isotope fractionation during condensation of the solar nebula, core formation and silicate differentiation cannot explain these observations. However, isotopic fractionation between liquid and vapour, followed by vapour escape during accretionary growth of planetesimals, generates appropriate residual compositions. Our modelling implies that the isotopic compositions of magnesium, silicon and iron, and the relative abundances of the major elements of Earth and other planetary bodies, are a natural consequence of substantial (about 40 per cent by mass) vapour loss from growing planetesimals by this mechanism.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): Inner planets, Geochemistry, Early solar system
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: Philip Pogge von strandmann
    Date Deposited: 26 Oct 2017 06:54
    Last Modified: 29 Jul 2019 06:17
    URI: http://eprints.bbk.ac.uk/id/eprint/20168

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