論文

査読有り
2015年

蛇紋岩の力学的性質とそのテクトニックな意義

地学雑誌
  • 平内健一,片山郁夫

124
3
開始ページ
371
終了ページ
396
記述言語
日本語
掲載種別
研究論文(学術雑誌)
DOI
10.5026/jgeography.124.371
出版者・発行元
公益社団法人 東京地学協会

Serpentine minerals (lizardite, chrysotile, and antigorite) are a major group of hydrous phyllosilicates resulting from the hydrothermal alteration of mantle peridotite. Their distinct rheological properties mean that serpentine minerals have a strong influence on the mechanical and seismogenic behavior of faults and plate boundaries in both continental and oceanic settings. In this paper we review the results of laboratory experiments performed to understand the frictional and mechanical properties, and deformation mechanisms of serpentinite. Frictional sliding experiments at low slip rates show that antigorite exhibits velocity-strengthening behavior (a−b > 0) over a wide range of temperature (25-400°C) , while values of (a−b) for chrysotile become negative as temperature increases (25-281°C) . This indicates that the stability of slip along serpentinite-bearing faults depends on the serpentine species and fault depth. Frictional sliding of antigorite at seismic slip rates leads to weakening by flash heating. Axial compression experiments at confining pressures of up to 4 GPa show that antigorite is stronger than lizardite by at least a factor of two. The flow law for dislocation creep of antigorite based on stress values at 〜15% strain also predicts differential stresses that are substantially lower than those for the dislocation creep of olivine at natural strain rates (10−10 to 10−14 s−1) . This suggests that the viscosity of serpentinite promotes slab–mantle decoupling. However, the antigorite flow law should be used with caution because antigorite starts to deform by semi-brittle flow after 〜20% strain. Large-strain simple-shear deformation of antigorite aggregates at high pressure (1 GPa) results in a strong alignment of antigorite c-axes normal to the shear plane. This observation explains the trench-parallel anisotropy beneath the Ryukyu subduction zone. Although dehydration embrittlement is considered a primary cause of intermediate-depth earthquakes, recent high-pressure experiments on antigorite show stable sliding behavior or detect no acoustic emissions during dehydration reactions. We emphasize that the presence of talc derived from the metasomatic alteration of serpentine further weakens and stabilizes the slab–mantle interface and promotes long-lived ( > 1 Ma) detachment faulting.

リンク情報
DOI
https://doi.org/10.5026/jgeography.124.371
CiNii Articles
http://ci.nii.ac.jp/naid/130005087137
CiNii Books
http://ci.nii.ac.jp/ncid/AN00322536
URL
http://id.ndl.go.jp/bib/026597766
URL
https://jlc.jst.go.jp/DN/JLC/20012933547?from=CiNii
ID情報
  • DOI : 10.5026/jgeography.124.371
  • ISSN : 0022-135X
  • CiNii Articles ID : 130005087137
  • CiNii Books ID : AN00322536

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