Intracrystalline nucleation during the post-garnet transformation under large overpressure conditions in deep subducting slabs

Masayuki Nishi, Tetsuo Irifune, Hiroaki Ohfuji, Yoshinori Tange

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

The mechanism of the post-garnet transformation in natural single-crystalline pyropic garnet has been examined under large overpressure conditions of ∼31-43GPa using the multianvil apparatus with sintered diamond anvils. Intracrystalline nucleation was found to be dominant above 35-38GPa, while only grain-boundary nucleation is responsible at lower pressures. In addition, natural pyropic garnet transformed to a single phase of perovskite without decomposing to multiple phases above 38GPa. Both intracrystalline nucleation and polymorphic growth of the post-garnet transformation under large overpressure conditions would strongly enhance the transformation kinetics. Consequently, the post-garnet transformation may pwroceed rapidly in the subducting slab at depths near ∼950km, which would cause substantial rheological weakening of the subducting slab. The metastable post-garnet transformation may also cause the seismic discontinuities at a depth of 900-1080km depth, which is indeed observed beneath some subduction zones.

Original languageEnglish
Article numberL23302
JournalGeophysical Research Letters
Volume39
Issue number23
DOIs
Publication statusPublished - 2012 Dec 16
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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