全州附近 花崗岩의 延性變形作用 = Ductile Deformation of Granitic Rock in the Vicinity of Jeonju, Korea

다국어 초록 (Multilingual Abstract)

A ductile shear zone trending N 50 E develops in Jurassic granite in the vicinity of Jeonju, Chollabuk-do. This shear zone shows oblique (normal-dextral) strike slip movement sense which is indicated from S-C mylonite, shear band, displaced broken grain, asymmetric porphyroclasts and grain shape preferred orientation and takes open fold resulting from later deformation.
Microstructural observation of grain size, grain shape, grain boundary morphology and internal deformation features of individual grains through the shear zone shows high strains of intense deformation at the shear zone center and metasediment contact, while low strains at the shear zone tip and shear zone boundary.
Strain history of this shear zone is interpreted to be noncoaxial and inhomogeneous during the deformation, resulting from the combination of simple shear and pure shear. Evidences for non-coaxial inhomogeneous deformation occur from S-C mylonite and asymmetrical porphyroclasts, displaced broken grains, minor fold of mylonite foliation, local intense strain zone in the microscopic observation and field, Strain analysis for quartz aggregate represents flattening type(K<1) of strain with Rs = 2.75-4.5.
Deformation mechanisms of the shear zone are not easy to determine, but dislocation creep may be operated at the earlier and grain boundary sliding followed from grain size reduction at the later stage, giving rise to mylonitic layering and finally grain growth phenomena are also recognized.