このエントリーをはてなブックマークに追加
ID 25983
本文ファイル
著者
Karato, Shun-ichiro
キーワード
rheology
flow law
Peierls stress
olivine
water
NDC
地球科学・地学・地質学
抄録(英)
Low-temperature high-stress rheology of olivine was investigated under water-saturated conditions by large strain shear deformation experiments using the Griggs-type apparatus. Samples at T = 1273-1373 K and P = 2 GPa under water-saturated conditions deformed under a significantly lower applied stress than expected from the power-law relation and the strain rate increases more rapidly with stress. These observations suggest that an exponential flow law operates under the present experimental conditions, in which the stress dependence of activation enthalpy is characterized by the Peierls stress. The Peierls stress is determined between 1.6 and 2.9 GPa depending on the choice of the form of stress-dependence of the activation enthalpy. These values are significantly smaller than the Peierls stress under dry conditions (9.1 GPa). We suggest that water (hydrogen) incorporated in the olivine lattices decreases the Peierls stress, and hence the rate of deformation in the exponential creep is significantly enhanced by the presence of water. The reduction of the Peierls stress by water results in the highly anisotropic weakening effect of water that causes the fabric transitions in olivine. The transition between the power-law and the exponential creep occurs at relatively low stress ~100 MPa at a geologically relevant strain rate of 10-15 s-1 when temperature is lower than 1273 K and under water-rich conditions. Hence the exponential creep might be dominated in olivine-rich rocks at low temperature and high stress under water-rich conditions, and such regions could be widespread in the subduction zone upper mantle where the cold lithospheric plates sink into the mantle.
掲載誌名
Physics of the Earth and Planetary Interiors
168巻
3-4号
開始ページ
125
終了ページ
133
出版年月日
2008-07
出版者
Elsevier Science BV
ISSN
0031-9201
NCID
出版者DOI
言語
英語
NII資源タイプ
学術雑誌論文
広大資料タイプ
学術雑誌論文
DCMIタイプ
text
フォーマット
application/pdf
著者版フラグ
author
権利情報
Copyright (c) 2008 Elsevier B.V.
関連情報URL
部局名
理学研究科