Microstructures in β-Mg1.8Fe0.2SiO4 experimentally deformed at transition-zone conditions

Thomas G. Sharp, Gilles Y.A. Bussod, Tomoo Katsura

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


The microstructures that develop in experimentally deformed β-Mg1.8Fe0.2SiO4 have been investigated by petrographic and transmission electron microscopy to determine the deformation mechanisms that are active under transition-zone conditions. Advances in the application of the multi-anvil apparatus to deformation studies allowed us to deform β-Mg1.8Fe0.2SiO4 at pressures of 14 GPa and greater and 1450°C. San Carlos olivine was transformed to β-phase and allowed to relax at an average strain rate of 1 × 10-5 for 3 h and subsequently deformed at a constant strain rate of 1 × 10-4. The olivine to β-phase transformation and deformation result in a bimodal grain size with the large grains having a preferred orientation. Deformation by dislocation creep and subgrain formation causes grain size reduction and nearly identical microstructures in the relaxed and high strain-rate samples. The dominant slip systems involved in the deformation of polycrystalline β-phase appear to be (010)[100] and (010)[001]. Slip in the [001] direction occurs by the glide of disassociated dislocations and produces Shockley-type stacking faults. The anisotropy that develops from the olivine to β-phase transformation under stress and subsequent dislocation creep may have profound effects on dynamic processes in the transition zone.

Original languageEnglish (US)
Pages (from-to)69-83
Number of pages15
JournalPhysics of the Earth and Planetary Interiors
Issue number1-3
StatePublished - Oct 1994
Externally publishedYes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Geophysics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science


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