Silicon and magnesium diffusion in a single crystal of MgSiO3 perovskite

Junshan Xu, Daisuke Yamazaki, Tomoo Katsura, Xiaoping Wu, Patrick Remmert, Hisayoshi Yurimoto, Sumit Chakraborty

Research output: Contribution to journalArticle

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Abstract

Si and Mg self-diffusion coefficients were measured simultaneously in single crystals of MgSiO3 perovskite under lower mantle conditions. There is little difference in Si volume diffusivity measured directly using single crystals (this study) and those retrieved from experiments with polycrystals (earlier studies). This agreement between studies establishes the reliability of Si diffusion coefficients measured in perovskite. Within the uncertainties of our measurements, no anisotropy in the diffusion of either Si or Mg could be resolved. Diffusion of Si and Mg in perovskite are described by an Arrhenius equation, D=D0 exp (-H/RT) at 25GPa, with D 0=5.10×10-11m2/s for Si and 4.99×10-11m2/s for Mg, H=308kJ/mol for Si, and 305kJ/mol for Mg. Mg diffusivity in MgSiO3 perovskite is distinctly lower than those measured in olivine, wadsleyite, and ringwoodite. We find that Mg has very similar diffusivity to Si in perovskite. As a consequence, the rheological properties of the lower mantle may be controlled by the coupled motion of Si and Mg. A point defect-based model is discussed that may account for the diffusion behavior of Si and Mg in MgSiO3 perovskite. Our data indicate that, within realistic ranges of temperature, grain size, and state of stress, both diffusion creep as well as dislocation creep may be observed in the lower mantle.

Original languageEnglish
Article numberB12205
JournalJournal of Geophysical Research B: Solid Earth
Volume116
Issue number12
DOIs
Publication statusPublished - Dec 1 2011

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perovskite
Silicon
Magnesium
silicon
magnesium
Single crystals
crystal
diffusivity
Earth mantle
single crystals
lower mantle
diffusion coefficient
polycrystals
olivine
wadsleyite
ringwoodite
point defects
dislocation creep
grain size
Creep

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Silicon and magnesium diffusion in a single crystal of MgSiO3 perovskite. / Xu, Junshan; Yamazaki, Daisuke; Katsura, Tomoo; Wu, Xiaoping; Remmert, Patrick; Yurimoto, Hisayoshi; Chakraborty, Sumit.

In: Journal of Geophysical Research B: Solid Earth, Vol. 116, No. 12, B12205, 01.12.2011.

Research output: Contribution to journalArticle

Xu, Junshan ; Yamazaki, Daisuke ; Katsura, Tomoo ; Wu, Xiaoping ; Remmert, Patrick ; Yurimoto, Hisayoshi ; Chakraborty, Sumit. / Silicon and magnesium diffusion in a single crystal of MgSiO3 perovskite. In: Journal of Geophysical Research B: Solid Earth. 2011 ; Vol. 116, No. 12.
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