Chemistry and mineralogy of earth's mantle. the spin state of iron in Fe3+-bearing Mg-perovskite and its crystal chemistry at high pressure

Izumi Mashino, Eiji Ohtani, Naohisa Hirao, Takaya Mitsui, Ryo Masuda, Makoto Seto, Takeshi Sakai, Suguru Takahashi, Satoshi Nakano

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

Valence, spin states, and crystallographic sites of Fe in (Mg,Fe)SiO3perovskite were investigated using energy-domain 57Fe-synchrotron Mössbauer spectroscopy and powder X-ray diffraction up to 86 GPa. The volumes of Fe3+-bearing perovskite in this study are slightly smaller than those of Mg endmember perovskite. Our Mössbauer data suggest that Fe3+prefers A sites coupled with Mg vacancies, which is consistent with previous data at ambient conditions. Fe3+in the A site remains in a high-spin state up to 86 GPa, and some fraction of the A site is occupied by Fe2+at pressures above 30 GPa. Fe2+in the A sites is also in a high-spin state up to 86 GPa. The coupled substitution from Mg2+to a highspin state of Fe3+and Mg2+vacancy would make the volume of perovskite smaller than that of Mg end-member perovskite. If the lower mantle is saturated in silica, perovskite containing high-spin Fe3+in A site has a higher density. Such silica oversaturated regions could sink by the density difference.

Original languageEnglish
Pages (from-to)1555-1561
Number of pages7
JournalAmerican Mineralogist
Volume99
Issue number8-9
DOIs
Publication statusPublished - Aug 1 2014
Externally publishedYes

Keywords

  • ferric iron
  • Mössbauer spectroscopy
  • Perovskite
  • spin state
  • X-ray diffraction

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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