論文

2017年2月

Grain size reduction due to fracturing and subsequent grain-size-sensitive creep in a lower crustal shear zone in the presence of a CO2-bearing fluid

Journal of Structural Geology
  • Takamoto Okudaira
  • ,
  • Norio Shigematsu
  • ,
  • Yumiko Harigane
  • ,
  • Kenta Yoshida

95
開始ページ
171
終了ページ
187
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1016/j.jsg.2016.11.001
出版者・発行元
Elsevier {BV}

To understand rheological weakening in the lower continental crust, we studied mylonites in the Paleoproterozoic Eidsfjord anorthosite, northern Norway. The zones of anorthositic mylonites range from a few millimeters to several meters thick, and include ultramylonites and protomylonites. They contain syn-kinematic metamorphic minerals, including Cl-bearing amphibole and scapolite. Thermodynamic analysis reveals that syn-deformational hydration reactions occurred at -600 degrees C and -700 MPa under CO2-bearing conditions. The protomylonites contain many fragmented plagioclase porphyroclasts. The fractures in porphyroclasts are filled with fine-grained plagioclase, suggesting that fracturing is a common mechanism of grain size reduction. The anorthite contents of fine-grained polygonal matrix plagioclase are different from those of porphyroclastic plagioclase, suggesting that the matrix grains nucleated and grew during syn-kinematic metamorphism. Plagioclase aggregates in the matrices of mylonites do not exhibit a distinct crystallographic preferred orientation, which implies that the dominant deformation mechanism was grain-size-sensitive creep. Consequently, in the lower crustal anorthositic mylonites, grain size reduction occurred via fracturing, rather than through dynamic. recrystallization, leading to grain-size-sensitive creep. The syn-kinematic recrystallization of minor phases at plagioclase grain boundaries may suppress the growth of plagioclase and contribute to the development of grain-size-sensitive creep. (C) 2016 Elsevier Ltd. All rights reserved.

リンク情報
DOI
https://doi.org/10.1016/j.jsg.2016.11.001
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000395225400012&DestApp=WOS_CPL
URL
http://www.scopus.com/inward/record.url?eid=2-s2.0-85011955352&partnerID=MN8TOARS
ID情報
  • DOI : 10.1016/j.jsg.2016.11.001
  • ISSN : 0191-8141
  • ORCIDのPut Code : 46163168
  • SCOPUS ID : 85011955352
  • Web of Science ID : WOS:000395225400012

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