Elasticity of natural majorite and ringwoodite from the Catherwood meteorite

Stanislav V. Sinogeikin, Jay D. Bass, Abby Kavner, Raymond Jeanloz

Research output: Contribution to journalArticle

Abstract

Sound velocities and elastic moduli of natural polycrystalline majorite (Mg0.78Fe0.21Ca0.01)SiO3, and ringwoodite (Mg0.75Fe0.25)2SiO4 from the Catherwood meteorite were measured by Brillouin spectroscopy. These are the first acoustic measurements for such natural high-pressure phases with Fe contents comparable to that of the Earth's mantle. The adiabatic bulk modulus of majorite is KS= 164(4) GPa, and the shear modulus is μ=87(2) GPa, which are typical values for garnet-structured silicates. Both the elastic moduli and the sound velocities of natural cubic majorite are slightly lower than values for aluminosilicate garnets with comparable Fe contents. Moreover, the bulk and shear moduli of natural majorite are indistinguishable from those of pure Mg majorite, and the dependence of these moduli on Fe content is small. In contrast, ringwoodite (KS=193(3), μ=113(2)) exhibits a pronounced change in the aggregate elastic moduli and sound velocities with increasing Fe content. The addition of 10% Fe to γ-phase changes the velocity by an amount comparable to the velocity change across the β-γ transition in Mg2SiO4. It is therefore necessary to account for the effect of Fe in constructing mineralogical models of the transition zone.

Original languageEnglish (US)
Article number97GL03217
Pages (from-to)3265-3268
Number of pages4
JournalGeophysical Research Letters
Volume24
Issue number24
DOIs
StatePublished - 1997

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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