https://repository.kopri.re.kr/handle/201206/5078 2026-04-14T23:42:42Z https://repository.kopri.re.kr/handle/201206/9089 Title: Microstructural study of high-pressure rocks and ices from Antarctica: Approaches from the electron backscatter diffraction (EBSD) technique Authors: Kim, Daeyeong 2017-04-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8332 Title: Trench-normal seismic anisotropy generated by lawsonite eclogites from the southern Motagua fault zone, Guatemala Authors: Kim, Daeyeong; Rhee, Jin-Han; Shunsuke Endo; Wallis, Simon Abstract: We present the results of EBSD analyses on extremely fresh lawsonite eclogites from southern Motagua fault zone, Guatemala for understanding seismic properties of subducting oceanic crust. The CPO of omphacite is characterized by (010)[001] with AVS of 1.4-2.7%, whereas that of lawsonite defined by (001)[010] with 3.4-14.7% AVS. The seismic anisotropy of lawsonite eclogite is calculated as 1.2-4.1% AVP and 1.8-6.8% AVS. Based on an assumption of the high modal abundance and strong fabric of lawsonite, the AVS of eclogite is estimated as ~11.7% in the case of 75% lawsonite and 25% omphacite. For events that propagate more or less parallel to the maximum extension direction, X, the fast S-wave velocity (VS) causing trench-normal seismic anisotropy for orthogonal subduction. Our study suggests that lawsonite in both blueschist and eclogite may play the key role in the formation of complex pattern of seismic anisotropy observed in NE Japan: weak trench-parallel in the forearc basin and trench-normal in the backarc. * Main contents of this study has been published in Tectonophysics (2016, vol 677-678, 88-98, doi: 10.1016/j.tecto.2016.04.012). 2016-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8333 Title: Rheological behavior of glaucophane and lawsonite in experimentally deformed blueschists Authors: Kim, Daeyeong; Azuma, Shintaro; Seto, Yusuke; Miyake, Akira; Michibayashi, Katsuyoshi; Wallis, Simon; Katayama, Ikuo Abstract: We performed a series of simple-shear deformation experiments on blueschist at 400？500 C and 1？2.5 GPa. Microstructures of samples deformed at 1？2 GPa are brittle, while they deformed at 2.5 GPa display ductile features. J-indices of glaucophane CPOs systematically decrease by increasing shear strain and confining pressure, and the angle to the shear direction is similar to that of a strain ellipsoid. These results, together with the variable orientations of recrystallized fine grains in a SAED image at 2 GPa, suggest that the brittle-ductile transition of glaucophane occurs at 2 GPa. On the other hand, lawsonite shows abundant fractures in the most specimens and a poor correlation among the J-index, shear strain, and confining pressure. The results demonstrate the predominant role of glaucophane on rheology of blueschist rather than lawsonite. Considering a strong fabric in the starting material and dry experimental condition, the brittle-ductile transition of glaucophane could occur at much shallower pressure than 2 GPa. Therefore our results indicate the dehydration embrittlement of subducting oceanic crust as an important factor in the origin of intermediate-depth earthquakes. 2016-01-01T00:00:00Z