Negative activation volume of oxygen self-diffusion in forsterite

Hongzhan Fei, Michael Wiedenbeck, Naoya Sakamoto, Hisayoshi Yurimoto, Takashi Yoshino, Daisuke Yamazaki, Tomoo Katsura

Research output: Contribution to journalArticle

Abstract

Oxygen self-diffusion coefficients (DOx) were measured in single crystals of dry synthetic iron-free olivine (forsterite, Mg2SiO4) at a temperature of 1600 K and under pressures in the range 10−4 to 13 GPa, using a Kawai-type multi-anvil apparatus and an ambient pressure furnace. Diffusion profiles were obtained by secondary ion mass spectrometry operating in depth profiling mode. DOx in forsterite increases with increasing pressure with an activation volume of −3.9 ± 1.2 cm3/mol. Although Mg is the fastest diffusing species in forsterite under low-pressure conditions, O is the fastest diffusing species at pressures greater than ∼10 GPa. Si is the slowest throughout the stable pressure range of forsterite. Based on the observed positive and negative pressure dependence of DOx and DMg (Mg self-diffusion coefficient), respectively, DOx + DMg in forsterite decreases with increasing pressure, and then increases slightly at pressures greater than 10 GPa. This behavior is in agreement with the pressure dependence of ionic conductivity in forsterite based on conductivity measurements (Yoshino et al., 2017), and can be used to explain the conductivity increase from ∼300 km depth to the bottom of the asthenosphere.

Original languageEnglish
Pages (from-to)1-8
Number of pages8
JournalPhysics of the Earth and Planetary Interiors
Volume275
DOIs
Publication statusPublished - Feb 1 2018

Fingerprint

forsterite
activation
oxygen
pressure dependence
conductivity
diffusion coefficient
asthenosphere
anvils
olivine
secondary ion mass spectrometry
ion currents
furnaces
low pressure
iron
mass spectrometry
single crystals
crystal
profiles
ion

Keywords

  • Activation volume
  • Forsterite
  • Ionic conductivity
  • Oxygen self-diffusion
  • Pressure dependence
  • Upper mantle

ASJC Scopus subject areas

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

Cite this

Negative activation volume of oxygen self-diffusion in forsterite. / Fei, Hongzhan; Wiedenbeck, Michael; Sakamoto, Naoya; Yurimoto, Hisayoshi; Yoshino, Takashi; Yamazaki, Daisuke; Katsura, Tomoo.

In: Physics of the Earth and Planetary Interiors, Vol. 275, 01.02.2018, p. 1-8.

Research output: Contribution to journalArticle

Fei, Hongzhan ; Wiedenbeck, Michael ; Sakamoto, Naoya ; Yurimoto, Hisayoshi ; Yoshino, Takashi ; Yamazaki, Daisuke ; Katsura, Tomoo. / Negative activation volume of oxygen self-diffusion in forsterite. In: Physics of the Earth and Planetary Interiors. 2018 ; Vol. 275. pp. 1-8.
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