Grain-size reduction of feldspars by fracturing and neocrystallization in a low-grade granitic mylonite and its rheological effect

Jin Han Ree, Hyeong Soo Kim, Raehee Han, Haemyeong Jung

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Feldspar grain-size reduction occurred due to the fracturing of plagioclase and K-feldspar, myrmekite formation and neocrystallization of albitic plagioclase along shear fractures of K-feldspar porphyroclasts in the leucocratic granitic rocks from the Yecheon shear zone of South Korea that was deformed under a middle greenschist-facies condition. The neocrystallization of albitic plagioclase was induced by strain energy adjacent to the shear fractures and by chemical free energy due to the compositional disequilibrium between infiltrating Na-rich fluid and host K-feldspar. With increasing deformation from protomylonite to mylonite, alternating layers of feldspar, quartz and muscovite developed. The fine-grained feldspar-rich layers were deformed dominantly by granular flow, while quartz ribbons were deformed by dislocation creep. With layer development and a more distributed strain in the mylonite, lower stresses in the quartz-rich layers resulted in a larger size of dynamically recrystallized quartz grains than that of the protomylonite.

Original languageEnglish
Pages (from-to)227-237
Number of pages11
JournalTectonophysics
Volume407
Issue number3-4
DOIs
Publication statusPublished - 2005 Oct 7

Keywords

  • Dynamic recrystallization
  • Grain-size reduction
  • Granitic mylonite
  • Granular flow
  • Yecheon shear zone

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

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