The chemical composition of the Earth: Enstatite chondrite models

M. Javoy, E. Kaminski, F. Guyot, D. Andrault, C. Sanloup, M. Moreira, S. Labrosse, A. Jambon, P. Agrinier, A. Davaille, C. Jaupart

Research output: Contribution to journalArticlepeer-review

Abstract

We propose a new model of Earth's bulk composition based on enstatite chondrites (E-chondrites), the only chondrite group isotopically identical to the Earth. This model allows a quantitative study of accretion and differentiation processes in the early Earth. Conditions for core formation are evaluated using data on silica-iron equilibrium at high pressure and temperature and the exchange budget equation SiO2 + 2Fe = Si + 2FeO, which is the result of IW and Si-SiO2 oxygen buffers' interaction and controls the evolution of mantle f(O2). Based on that equation, ranges for the compositions of the Bulk Silicate Earth, the lower mantle and the core are deduced from the compositions of E-chondrites and their constituents. For these ranges of compositions, we show that during core differentiation, the mantle f(O2) evolves naturally from approximate to IW-3.2 to IW-1.4 +/- 0.1. The model compositions are tightened using geophysical constraints on (1) the amount of light elements in the core, (2) the petrology of the upper and lower mantle and (3) the thermal and convective structure of the lower mantle. Our results indicate that the lower mantle is enriched in Si and Fe, which is consistent with recent geophysical studies, and depleted in highly refractory elements, notably in Uranium and Thorium. (C) 2010 Elsevier BM. All rights reserved.

Original languageEnglish
Pages (from-to)259-268
Number of pages10
JournalEarth and Planetary Science Letters
Volume293
Issue number3-4
DOIs
Publication statusPublished - 1 May 2010

Keywords

  • chemical earth models
  • enstatite chondrites
  • Redox state
  • isotopic anomalies
  • core composition
  • heterogeneous mantle
  • early Earth
  • radioactive heating
  • LOWER MANTLE
  • ISOTOPIC COMPOSITION
  • SOLAR-SYSTEM
  • NOBLE-GASES
  • SEISMIC VELOCITIES
  • NITROGEN ISOTOPES
  • LOWERMOST MANTLE
  • LIGHT-ELEMENTS
  • HIGH-PRESSURE
  • OUTER CORE

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