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

doi:10.1016/j.tecto.2005.07.010

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 journal › Article › peer-review

44 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 language	English
Pages (from-to)	227-237
Number of pages	11
Journal	Tectonophysics
Volume	407
Issue number	3-4
DOIs	https://doi.org/10.1016/j.tecto.2005.07.010
Publication status	Published - 2005 Oct 7

Bibliographical note

Funding Information:
We thank W.M. Lamb and J. Newman for discussions on feldspar microstructures, and R. Guillemette and S. Choi for initial electron microprobe analyses on our samples. We appreciate thorough and constructive reviews by K. Kanagawa, an anonymous referee and J.-P. Burg which improved the paper significantly. This research was supported by KOSEF grant R02-2003-000-10039-0 to JHR.

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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10.1016/j.tecto.2005.07.010

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

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.",

keywords = "Dynamic recrystallization, Grain-size reduction, Granitic mylonite, Granular flow, Yecheon shear zone",

author = "Ree, {Jin Han} and Kim, {Hyeong Soo} and Raehee Han and Haemyeong Jung",

note = "Funding Information: We thank W.M. Lamb and J. Newman for discussions on feldspar microstructures, and R. Guillemette and S. Choi for initial electron microprobe analyses on our samples. We appreciate thorough and constructive reviews by K. Kanagawa, an anonymous referee and J.-P. Burg which improved the paper significantly. This research was supported by KOSEF grant R02-2003-000-10039-0 to JHR.",

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AU - Han, Raehee

AU - Jung, Haemyeong

N1 - Funding Information: We thank W.M. Lamb and J. Newman for discussions on feldspar microstructures, and R. Guillemette and S. Choi for initial electron microprobe analyses on our samples. We appreciate thorough and constructive reviews by K. Kanagawa, an anonymous referee and J.-P. Burg which improved the paper significantly. This research was supported by KOSEF grant R02-2003-000-10039-0 to JHR.

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N2 - 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.

AB - 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.

KW - Dynamic recrystallization

KW - Grain-size reduction

KW - Granitic mylonite

KW - Granular flow

KW - Yecheon shear zone

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

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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