A Finding of Ultramafic Mylonitic Pseudotachylyte and Its Seismogenic Significance: Toward a Better Understanding of Seismogenic Processes in the Mantle

• OBATA Masaaki

  Kyoto University, Graduate School of Science, Division of Earth and Planetary Sciences

• UEDA Tadamasa

  Kyoto University, Graduate School of Science, Division of Earth and Planetary Sciences JSPS Research Fellow

Bibliographic Information

Other Title

• 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―
• 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―

Abstract

 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.

Journal

• Journal of Geography (Chigaku Zasshi)

  Journal of Geography (Chigaku Zasshi) 120 (3), 439-451, 2011

  Tokyo Geographical Society

Keywords

• earthquakes
• fault
• mantle
• peridotite
• frictional melting
• mylonite

Details

• CRID: 1390001204228954880
• NII Article ID: 10030372677
• NII Book ID: AN00322536
• DOI: 10.5026/jgeography.120.439
• ISSN: 18840884
• ISSN: 0022135X
• NDL BIB ID: 11163076
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I11163076
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed