On the Properties and Intersection Feature of the Ductile Shear Zone (Chonju shear zone) near Yongkwang-Eub

영광(靈光) 부근(附近) 연성전단대(延性剪斷帶)(전주전단대(全州剪斷帶))의 성질(性質)과 교차양상(交叉樣相)에 관(關)하여

Ductile shear zones developed in Jurassic granites in the Yonggwang area show NE trend at the eastern part and nearly EW trend at the western part, respectively. Judged from shear sense indicators, they have resulted from dextral strike-slip movement. The intersection of both trends is thought to be due to the truncation and offset of NE shear zone Chonju Shear zone by the brittle Yonggwang fault which runs in near EW direction with sinistral movement sense. The simple shear deformation was predominate through the deformation in this ductile shear zone. Based on this deformation mechanism, the shear strain (${\gamma}$) estimated in domain 1 increases from 0.14 at the shear zone margin to 9.41 toward the center of shear zone. Total displacement obtained only from this measured section(JK 59 to JK14) appecars to be 1434.5 meters. The sequential development of microstructures can be divided into three stages; weakly-foliated, well-foliated and banded-foliated stages. In the weakly-foliated stage dislocation glide mechanism might be predominant. In the well-foliated stage grain boundary migration and progressive misorientation of subgrains was remarkable during dynamic recovery and recrystallization. In the banded-foliated stage grain boundary sliding and microfracturing mechanisms accompanied with crushing and cracking were marked. According to strain analysis from quartzites of the metasedimentary rocks, strain intensity (${\gamma}$) of the samples within the ductile shear zone ranges from 2.7 to 5.7, while that of the samples out of the ductile shear zone appears to be about 1.7.