超マフィックマイロナイトシュードタキライトの発見とその地震発生学的意義―マントル地震の震源過程の解明に向けて―

  • 小畑 正明
    京都大学大学院理学研究科地球惑星科学専攻地質学鉱物学教室
  • 上田 匡将
    京都大学大学院理学研究科地球惑星科学専攻地質学鉱物学教室 日本学術振興会特別研究員DC

書誌事項

タイトル別名
  • A Finding of Ultramafic Mylonitic Pseudotachylyte and Its Seismogenic Significance: Toward a Better Understanding of Seismogenic Processes in the Mantle
  • チョウマフィックマイロナイトシュードタキライト ノ ハッケン ト ソノ ジシン ハッセイガクテキ イギ マントル ジシン ノ シンゲン カテイ ノ カイメイ ニ ムケテ
  • Toward a Better Understanding of Seismogenic Processes in the Mantle
  • ―マントル地震の震源過程の解明に向けて―

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抄録

 This paper reviews the occurrence of pseudotachylyte having a mylonitic texture of a ultramafic composition, originally reported by Ueda et al. (2008a), as a new type of pseudotachylyte—mylonitic pseudotachylyte—and discusses its seismogenic significance in the context of deep to intermediate-depth earthquakes in the mantle. Referring to widely accepted definitions of pseudotachylyte and mylonite, it is emphasized that mylonitic fault-vein pseudotachylytes represent frozen melts generated by frictional melting of host rocks during earthquakes. It is also emphasized that the mylonitic pseudotachylyte is a complex, integrated product of a whole sequence of seismogenic processes including pre-seismic (ductile) shear localization and recrystallization, followed by a (brittle) seismic rupture and comminution and frictional heating-and-melting, and further, by rapid cooling and crystallization, with or without co-seismic or post-seismic shear deformation. Although unraveling and accurate analyses of the whole processes is a difficult task because of the extremely fine-grained nature of the pseudotachylytes and the recrystallization overprints therein, careful petrographic analyses of such rocks should provide useful insights into the seismogenic processes bridging the gap between conventional seismological, geological and petrological methods. A need for a multidisciplinary approach is emphasized for a better understanding of seismogenic processes in the mantle.

収録刊行物

  • 地学雑誌

    地学雑誌 120 (3), 439-451, 2011

    公益社団法人 東京地学協会

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