Formation of metastable assemblages and mechanisms of the grain-size reduction in the postspinel transformation of Mg2SiO4

Tomoaki Kubo, Eiji Ohtani, Takumi Kato, Satoru Urakawa, Akio Suzuki, Yuichi Kanbe, Ken Ichi Funakoshi, Wataru Utsumi, Kiyoshi Fujino

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Abstract

An in situ X-ray observation of the postspinel transformation kinetics was made using intense synchroton radiation. We confirmed that Mg2SiO4 spinel transforms into fine lamellae of SiO2 stishovite and periclase, and/or MgSiO3 ilmenite and periclase as an intermediate step in the postspinel transformation. These metastable assemblages eventually disappear and form the stable assemblages of MgSiO3 perovskite and periclase. Initial grain size just after the postspinel transformation drastically changes with overpressure. Viscosity of the subducting slab into the lower mantle, which is thought to be deformed by grain-size-sensitive creep, would depend on overpressure needed for the postspinel transformation at geological time scale.

Original languageEnglish
Pages (from-to)807-810
Number of pages4
JournalGeophysical Research Letters
Volume27
Issue number6
DOIs
Publication statusPublished - Mar 15 2000

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ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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