https://repository.kopri.re.kr/handle/201206/11561 Mon, 06 Apr 2026 01:06:52 GMT 2026-04-06T01:06:52Z https://repository.kopri.re.kr/handle/201206/13586 Title: Tectonic constraints on formation and evolution of microplates in the Indian and Pacific Oceans: reviews and statistical inferences Authors: Choi, Hakkyum; Kim, Seung-Sep; Park, Sung-Hyun Abstract: Oceanic plates are growing through narrow boundaries, such as mid-ocean ridges and transform faults. However, the discovery of diffuse plate boundary suggests another type of plate boundary that accommodates difference in plate motion via internal deformation. Along the Central and Southeast Indian ridges, for example, the Capricorn and Macquarie microplates exhibit widespread diffuse boundaries and hence divide the Indo-Australian Plate further into the Indian, Australian, Capricorn, and Macquarie plates. As for microplates distributed along the East Pacific Rise and Pacific-Antarctic Ridge in the Pacific Ocean, however, the typical plate boundaries surrounding the given microplate are distinctly established. Global plate reorganization involving the changes in plate motion or in spreading direction can be accommodated by forming a microplate through ridge extinction, ridge propagation, and pseudofault formation. However, relations between these tectonic processes have not been quantitatively assessed. In particular, we aim to examine tectonic constrains on the formation processes of microplates with diffuse plate boundary. In this study, we compare plate size, plate age, full-spreading rates, thermal structures, total rotation, and rotation rate for the 9 microplates including extinct plates (i.e., Capricorn, Macquarie, and Mammerickx* microplates in the Indian and Southern Oceans; Galapagos, Easter, Juan Fernandez, Bauer*, Friday*, and Selkirk* microplates in the Pacific Ocean; extinct plates are denoted with asterisks). From this comparison, we find that the microplate formation would require certain tectonic conditions (e.g., full-spreading rates faster than 70-80 mm/yr and rotation rates faster than 5-6 degrees/m.y.) to evolve into an independent and rigid plate with respect to the neighboring plates. If the conditions are not met, the same tectonic reorganization would result in a microplate with diffuse plate boundaries. Wed, 01 Dec 2021 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/13586 2021-12-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/13046 Title: Magnetic Constraints on Off-Axis Seamount Volcanism in the Easternmost Segment of the Australian-Antarctic Ridge Authors: Choi, Hakkyum; Kim, Seung-Sep; Park, Sung Hyun Abstract: The Australian-Antarctic Ridge (AAR) is an intermediate-spreading rate system located between the Southeast Indian Ridge and Macquarie Triple Junction of the Australian-Antarctic-Pacific plates. KR1 is the easternmost and longest AAR segment and exhibits unique axial morphology and various volcanic structures. We identified three asymmetric seamount chains positioned parallel to the seafloor spreading direction, which were indicative of prevalent off-axis volcanism in the vicinity of segment KR1. Two-dimensional magnetic modeling was used to predict the magnetization polarity of the seamounts, as well as to constrain their formation time and duration. The magnetic modeling revealed that the majority of the examined seamounts were formed over a period of less than ∼600 kyrs. The seamount formation primarily occurred during two distinct volcanic pulses from 0.16-1.14 to 1.58-2.69 Ma. A temporal gap of 200-650 kyrs between the formation time of the seamounts and seafloor was estimated for certain seamounts that were formed much later than their underlying seafloor and at a distance of 10-20 km from the KR1 axis. Typically, such off-axis seamount activity is related to axial mantle convection caused by excessive magma supply near the ridge crest. Considering the scale of off-axis volcanism and thickening lithosphere ∼20 km away from the axis with intermediate-spreading rates, small-scale upwelling made feasible by the fertile mantle heterogeneity is proposed as the mechanism for the seamount formations at off-axis distances, and the geochemically enriched compositions of the seamounts support this alternative explanation. Wed, 01 Sep 2021 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/13046 2021-09-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/11786 Title: Upper mantle seismic anisotropy beneath the Northern Transantarctic Mountains inferred from peridotite xenoliths near Mt. Melbourne, northern Victoria Land, Antarctica Authors: Kim, Daeyeong; Park, Munjae; Park, Yongcheol; Qi, Chao; Kim, Hwayoung; Lee, Mi Jung; Michibayashi, Katsuyoshi Abstract: Microstructural investigations of mantle xenoliths from the Mt. Melbourne area were undertaken to reveal the origin of S-wave splitting beneath northern Victoria Land, Antarctica. The six analyzed peridotites contain various deformation features. The rotated olivine maxima of [100] and [010] into horizontal and vertical orientations, respectively, are classified into five samples with a D-type crystallographic preferred orientation (CPO) and one sample as an A-type CPO. The D-type olivine fabric can be explained by multiple slip systems of {0kl}[100] at low-temperature and high-stress conditions; therefore, both compressional and extensional regimes during subduction and rifting, respectively, could be applied in this study. With an assumption that olivine a-axes are aligned along the direction of mantle flow to form maximum S-wave splitting, the observed delay time of 0.9？1.3 s beneath northern Victoria Land can be partially explained by the anisotropy in the mantle peridotites. The remaining seismic anisotropy can be explained by the presence of melt pockets trapped along tectonic faults that developed perpendicular to the fast S-wave splitting direction. This study therefore demonstrates that the NE？SW-trending S-wave splitting beneath northern Victoria Land, Antarctica, results from the existence of both mantle peridotites as well as melt pockets trapped along the tectonic faults. Mon, 01 Feb 2021 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/11786 2021-02-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/12825 Title: The Antarctic is calling Authors: Park, Sung Hyun Abstract: 남극 중앙해령 1차 부터 5차 까지 전체 내용 소개, 바다와 지구에 대한 글, 외국 조사선 승선내용, 남극 중앙해령 연구 업적 간단히 소개 Wed, 01 Jul 2020 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/12825 2020-07-01T00:00:00Z