Hydrogen diffusivity in wadsleyite and water distribution in the mantle transition zone

Ryota Hae, Eiji Ohtani, Tomoaki Kubo, Takao Koyama, Hisashi Utada

研究成果: Contribution to journalArticle査読

70 被引用数 (Scopus)

抄録

The kinetics of the hydrogen diffusivity in synthesized polycrystalline wadsleyite was measured by IR spectroscopy in order to determine the diffusion coefficient of hydrogen in wadsleyite, the major constituent mineral in the mantle transition zone, with the composition of (Mg0.89Fe0.11)2SiO4. The hydration experiments were conducted at 15-16 GPa and temperature range from 900 to 1200 °C with Mg(OH)2 as the water source by Kawai-type multi-anvil apparatus. The diffusion rate obtained here is considered to be an effective diffusion coefficient with the grain size of ∼9 μm involving contributions both from the lattice diffusion and the grain boundary diffusion. The temperature dependence of diffusion of hydrogen in polycrystalline wadsleyite was determined to be DH = 9.6 × 10-6 exp [-123 (±32) (kJ mol-1)/RT] at 15 GPa. Hydrogen diffusion rate in wadsleyite is roughly consistent with the average diffusivity of hydrogen in olivine. In recent years, several authors have suggested a possibility of the hydrous transition zone, and the distribution and transport properties of water are still debated. On the basis of water-dependence of the electrical conductivity the water content in the mantle transition zone was estimated from the observed conductivity by using the Nernst-Einstein relation. The results obtained here show that the distribution of water should be quite heterogeneous throughout the mantle transition zone.

本文言語英語
ページ(範囲)141-148
ページ数8
ジャーナルEarth and Planetary Science Letters
243
1-2
DOI
出版ステータス出版済み - 3 15 2006

All Science Journal Classification (ASJC) codes

  • 地球物理学
  • 地球化学および岩石学
  • 地球惑星科学(その他)
  • 宇宙惑星科学

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