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http://dx.doi.org/10.7854/JPSK.2014.23.2.61

Structural characteristics of the Yecheon Shear Zone in the Pukhumyeon-Pyeongeunmyeon area, Gyeongsangbukdo, Korea  

Kang, Ji-Hoon (Department of Earth and Environmental Sciences, Andong National University)
Publication Information
The Journal of the Petrological Society of Korea / v.23, no.2, 2014 , pp. 61-73 More about this Journal
Abstract
The dextral strike-slip Yecheon Shear Zone of (E)NE-(W)SW trend is developed in the Pukhumyeon-Pyeongeunmyeon area, Gyeongsangbukdo, in the central part of Sobaeksan Massif, Korea which mainly consists of Precambrian metasedimentary rocks and Mesozoic granite. This paper researched the relative formation time, the deformation temperature, and the distribution of ultramylonite zone of Yecheon Shear Zone from the analysis of their deformed rock structures and microstructures. There are the mylonite foliation and stretching lineation by shear deformation, and the (E)SE-vergence gentle plunging, moderately inclined tight fold defined by the gneissosity and mylonite foliation as ductilely deformed main rock structures. Flame perthites, myrmekites, microfractures, microkinks, kinkband, and undulatory extinction are recognized as characteristic microstructures in feldspars during ductile shear deformation. Patterns of c-axis fabrics of recrystallized quartz aggregate display single girdle and type I crossed girdle where the rhomb and basal slip systems are predominant. The shearing senses on sense-of-shear plane show top-to-the-NE and top-to-the-SW on the predominant NW-dipping and subordinate SE-dipping mylonite foliations, respectively. These characteristic rock structures and microstructures suggest that the Yecheon ductile shearing occurred under $350{\sim}450^{\circ}C$ deformation temperature after the tight folding. The (E)NE trending ultramylonite zone of Yecheon Shear Zone, which passes through the Pulnobong and the north part of Pakdalsan, is established from the zonal distribution of Precambrian metasedimentary rocks and the grain-size distribution of feldspars in the Precambrian metasedimentary rocks and quartzs in the Mesozoic granite.
Keywords
Pukhumyeon-Pyeongeunmyeon area of Sobaeksan Massif; Yecheon Shear Zone; shearing sense; deformation temperature; ultramylonite zone;
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Times Cited By KSCI : 2  (Citation Analysis)
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