• Economic and Environmental Geology
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• v.28 no.4
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• pp.395-404
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• 1995

The geologic structure of the Cheju volcanic island has been investigated by analyzing the gravity and magnetic data. Bouguer gravity map shows apparent circular low anomalies at the central volacanic edifice, and the maximum difference of the anomaly values on the island appears to be 30 mgal. The subsurface structure of the island is modeled by three-dimensional depth inversion of gravity data by assuming the model consists of a stacked grid of rectangular prisms of volcanic rocks bounded below by basement rocks. The gravity modeling reveals that the interface between upper volvanic rocks and underlying basement warps downward under Mt. Halla with the maximum depth of 5 km. Magnetic data involve aeromagnetic and surface magnetic survey data. Both magnetic anomaly maps show characteristic features which resemble the typical pattern of total magnetic anomalies caused by a magnetic body magnetized in the direction of the geomagnetic field in the middle latitude region, though details of two maps are somewhat different. The reduced-to-pole magnetic anomaly maps reveal that main magnetic sources in the island are rift zones and the Halla volcanic edifice. The apparent magnetic boundaries inferred by the method of Cordell and Grauch (1985) are relatively well matched with known geologic boundaries such as that of Pyosunri basalt and Sihungri basalt which form the latest erupted masses. Inversion of aeromagnetic data was conducted with two variables: depth and susceptibility. The inversion results show high susceptibility bodies in rift zones along the long axis of the island, and at the central volcano. Depths to the basement are 1.5~3 km under the major axis, 1~1.5 km under the lava plateau and culminates at about 5 km under Mt. Halla. The prominent anomalies showing N-S trending appear in the eastern part of both gravity and magnetic maps. It is speculated that this trend may be associated with an undefined fault developed across the rift zones.

• The Journal of the Petrological Society of Korea
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• v.1 no.2
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• pp.104-123
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• 1992

We present petrography, mineral chemistry of amphibole and plagioclase, and major and trace element chemistry for the Ogcheon metabasites occurring in the Poun and Mungyong areas to understand metamorphism, and to define chemical characteristics of parental rocks and their implication for tectonic environment. The Ogcheon metabasites often preserve relict igneous textures, although no primary phases are observed. They are mainly composed of amphibole (actinolite+hornblende)+plagioclase+epidote+chlorite+sphene+opaque oxides, indicating epidote amphibolite facies metamorphism. Coarse-grained amphiboles frequently have actinolitic composition in the core, and hornblende along the margin and cleavage, which can be interpreted either as miscibility gap or as result of polymetamorphism. Although presumed polymetamorphic events in the Ogcheon supergroup favor the latter possibility, further metamorphic studies are necessary to solve the problem. Amphibole and plagioclase chemistries suggest greenschist (epidote-amphibolite, if miscibility gap is present) to amphibolite facies metamorphism of possibly medium pressure. The major and trace element data of whole rocks indicate that the Ogcheon metabasites are transitional to tholeiitic basalts belonging to within-plate environment. Absence of evidences indicating deep sea environment suggests that the Ogcheon metabasites emplaced in an intra-cratonic, possibly rift environment which failed to proceed to an oceanic rift. Chemical variation of the metabasites toward a granitic pluton indicates K loss closer to the pluton, suggesting that caution should be taken when K is involved in a discussion.

• Journal of the Korean Geographical Society
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• v.51 no.4
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• pp.473-490
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• 2016

This study aims to analyze the regional geomorphology of the Chugaryeong Tectonic Valley which has been one of the most important areas for Korean geomorphological research. Though the Chugaryeong Tectonic Valley has been thought important for the tectonic settings and orographic processes in Korea, geomorphological and geological discussions still are sustaining for finding out evidences of the settings. The Chugaryeong valley region has many geomorphic themes such as tectonic structure, volcanics, river, mountain, terrace, lake and sediment layers. The research of the valley focuses on the comprehensive analysis of the previous references mainly including geomorphic naming, geomorphology and geology, and history of the study for estimating the origin of tectonic valley, formation of the lave plateau, change of river structure by dissection, restoration of the landform before lava eruption, and the processes and age dating of the various landforms. Conclusively, the Chugaryeong Tectonic Valley may be recognized as the linear region of the tectonic and volcanic landforms with other various applied geomorphic settings.

• Journal of The Geomorphological Association of Korea
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• v.17 no.1
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• pp.1-14
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• 2010

This paper deals with the classification and distribution of geomorphic surfaces and analysis on effects of geomorphic processes on the landforms in the inaccessable DMZ (Demilitarized Zone) to Wonsan Bay of East Sea coast of Chugaryeong Rift Valley, Central Korea. DEM (Digital Elevation Model) and Landsat images are used for the above anlaysis. The geomorphic surfaces are classified by TPI (Topographical Position Index) for the analysis of the convexity and concavity calculated using topographical elements such as elevation, steepness, and relief. In the Chugayreong Valley, 10 geomorphic surfaces are classified as steep valley, shallow valley, upland drainage, U-shaped valley, plain, open slope, upper slope, local ridge, midslope ridge, and high ridge. Zonal Statistics presents average characteristics of geomorphological processes of surfaces by the relationships between bedrock and relief, surface and relief, and between surface and NDVI. So, these analysis can help to understand geomorphological process such as dissection of lava plateau and watershed divide evolution.

• The Journal of the Petrological Society of Korea
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• v.7 no.2
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• pp.111-131
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• 1998

The migmatitic gneiss in the Odesan Gneiss Complex has small amount of quartzite, amphibolite and marble and the Kuryong Group which contact with migmatitic gneiss unconformitly, also contains some amphibolite. Preview studies of this area had regarded that the amphibolites contact with marble had been produced by metasomatism from the pelitic and calcareous sediments mixtures, but the amphibolite is reinterpreted as igneous origin. $SiO_2$ content of the amphibolite is 45.9~52.7 wt%, which corresponds to basaltic composition. MgO content has narrow range (4.6~6.87 wt%) and major and trace element are plotted against MgO,$TiO_2, P_2O_5$, Hf, Zr are reduced and Cr and Ni are increased their content with increasing MgO. This phenomenon indicates that the basaltic magma as the protolith of the amphibolite had frationated with the crystallization of the pyroxene and/or olivine. REE pattern has smoothly decrease from LREE to HREE. Eu/Eu(0.83~1.19) show the flat Eu anomaly, which indicate small fractional crystallization of plagioclase. HREE is enriched in the garnet-bearing amphibolites. Several discrimination diagram for the basaltic magma show that the amphibolite of the study area is originated tholeiitic basaltic magma indicating continental rift environment. Due to determine the metamorphic condition garnet-hornblende geothermometry and hornblende-plagioclase geobarometry are used. Peak metamorphic temperature range of the amphibolite $788~870^{\circ}C$ and is deduced toward the northeastern part. The calculated temperature from the amphibolite has slightly higher than the temperature of the metapelites but the trend of metamorphic grade which decrease from western to eastern part progradly is similar to each other. The metamorphic pressure calculated by garnet- hornblede-plagioclase geobarometry is 4~5kb. But ilmenite-plagioclase pair enclosed in garnet show 8 kb at $700^{\circ}C$ by garnet-ilmenite-rutile-plagioclase geobarometery. The zonal profile of garnet in sample 84 shows the bell-shape profile, which grossular content decreases whereas pyrope content increases progressively. This means that the amphibolite has undergone the clockwise P-T-t path which is shown in the migmatitic gneiss of the Odesan Gneiss Complex.

• Proceedings of the Korean Quaternary Association Conference
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• 2004.06a
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• pp.49-50
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• 2004

푸른 진주라 불리는 훕스굴호는 러시아 국경에 인접한 몽고 북부의 청정호수로 해발 약 1,645m 지점에 위치한다. 훕스굴호의 길이는 약 136km이고, 폭은 20-40km이며, 최대수심은 약 262m 이다. 이 호수의 물은 세계에서 가장 깨끗한 담수 중 하나로 몽고 지표수원의 약 70%를 공급하고 있다. 훕스굴호는 바이칼 열곡대내에 형성된 일종의 구조호로 약 240만년 내지 400만년전에 형성된 것으로 추정되고 있다. 훕스굴호는 자연공원으로 지정되어 보호되고 있으며, 따라서 호수의 유역은 다행스럽게도 인간활동에 오염되거나 교란되지 않아 다양하고 흥미로운 육상/수성 생물상을 보유하고 있으며, 퇴적물 기록 역시 후기 신생대 동안의 중앙아시아의 지구환경 및 기후변화 연구에 매우 적합하다. 바이칼 시추사업 (Baikal Drilling Project)은 신생대 후기 동안의 중앙아시아의 지구조진화 및 전지구적 기후변화를 규명하기 위해 미국, 러시아, 일본, 독일 등이 참여한 다국가 공동사업이다. 바이칼 시추사업 연구팀은 지난 15년간 많은 노력과 예산을 투자하여 바이칼 호로부터 총 1,600m에 이르는 방대한 양의 퇴적물 코아를 성공적으로 회수하였고, 이 시료를 이용하여 후기 신생대 동안의 중부 유라시아 대륙의 고기후/고환경 진화과정을 성공적으로 규명하였다. 바이칼 시추사업이 성공적으로 진행됨에 따라, 이 사업에 참여했던 러시아와 일본의 과학자들은 바이칼호의 서쪽에 위치한 몽고 북부의 훕스굴에도 많은 관심을 가지게 되었으며, 동시에 바이칼 시추사업의 후속사업으로 훕스굴 시추사업을 새롭게 추진하게 되었다. 한편, 대륙내부에서의 제4기 지구환경 및 기후 변화 과정에 많은 관심을 가지고 연구해 오던 한국지질자원연구원도 2003년에 정식 회원으로 훕스굴 시추사업에 합류하였다. 훕스굴 시추사업 연구팀은 몽고의 지질광물자원연구소 (대표연구기관), 러시아의 지구화학연구소, 일본의 나고야대학교 그리고 한국의 지질자원연구원 등 4개국의 연구기관으로 구성되어 있다. 이들 4개 연구기관은 시추획득 및 기초연구 수행에 필요한 연구비를 현금 혹은 현물 (장비 포함)의 형태로 공동부담하고 있으며, 따라서 획득한 시추코아에 대해서도 각 연구기관이 전 구간에 대해 동일하게 25%의 소유권을 가지고 있다. 훕스굴 시추사업은 2008년까지 수행될 계획이며, 시추작업은 2005년까지 완료될 계획이다. 연구 진행과 관련하여, 공동연구의 명분을 높이고 분석의 효율성을 높이기 위해서 시료채취 및 기초자료 획득은 4개국의 연구원이 모여 공동으로 수행한 후의 결과물을 서로 공유하고, 자세한 전문분야 연구는 각 국의 대표기관이 독립적으로 수행하는 방식을 택하였다. 훕스굴에 대한 제1차 시추작업은 2004년 3월 말에 실시하였다. 시추작업 결과, 약 80m의 시추 코아가 성공적으로 회수되어 현재 러시아 이르쿠츠크 지구화학연구소에 보관중이다. 이 시추코아는 2004년 8월 중순경에 4개국 연구팀원들에 의해 공동으로 기재된 후에 분할될 계획이다. 분할된 시료는 국내로 운반되어 다양한 전문분야별 연구에 이용될 것이다. 한편, 제2차 시추작업은 2004년 12월에서 2005년 2월 사이에 실시될 계획이다. 수백만년에 이르는 장기간에 걸쳐 지구환경변화 기록이 보존되어 있는 훕스굴호에 대한 시추사업은 후기 신생대 동안 유라시아 대륙 중부에서 일어난 지구환경 및 기후변화를 이해함과 동시에 이러한 변화가 육상생태계 및 지표지질환경에 미친 영향을 이해하는데 크게 기여할 것이다.

• The Journal of the Petrological Society of Korea
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• v.21 no.3
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• pp.367-383
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• 2012

The Gyeongsang Arc is the most notable of the Korea Arc that is composed of several volcanic arcs trending to NE-SW direction in the Korean peninsula. The Hayang Group has many volcanogenic interbeds of lava flows by alkaline or calc-alkaline basaltic volcanisms during early Cretaceous. Late Cretaceous calc-alkaline andesitic and rhyolitic volcanisms reconstructed the Gyeongsang Arc that consist of thick volcanic strata on the Hayang Group in The Gyeongsang Basin. The volcanisms characterize first eruptions of basaltic and andesitic lavas with small pyroclastics, and continue later eruptions of dacitic and rhyolitic ash-fall and voluminous ash-flow with some calderas and then domes and dykes. During the Early Cretaceous (about 120 Ma), oblique subduction of the Izanagi plate to NNW from N direction results in sinistral strike-slip faults to open a pull-apart basin in back-arc area of the Gyeongsang Arc, in which erupted lava flows from generation of magma by a decrease in lithostatic pressure. Therefore the Gyeongsang Basin is interpreted into back-arc basin reconstructed by a continental rifting. Arc volcanism began in about 100 Ma with exaggeration of the back-arc basin in the Gyeongsang, and then changed violently to construct volcanic arcs. During the Late Cretaceous (about 90 Ma), orthogonal subduction of the Izanagi plate to NW from NNW direction ceased development of the basin to prolong violent volcanisms.

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.169-179
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• 2005

Acidic metavolcanic rocks distributed around the Chungju iron deposit show significantly high abundances of rare earth elements and high field strength elements. Relatively high ${\epsilon}_{Nd}$(0) values and lack of negative Nb anomaly suggest that assimilation of crustal material is not involved in their generation. They are plotted within the within-plate environment according the tectonic discrimination diagrams. Such geochemical characteristics are very similar to the acidic metavolcanic rocks of Munjuri Formation. They also show geochemical characteristics of Al-type magma of Eby (1992). All such diagnostic characters indicate differentiation of mantle-derived magma produced from the rift environment, related to the breakup of continent. In contrast to the alkali granites and the rare metal deposit both having age of c. 330 Ma, Sm-Nd isotopic data of the acidic metavolcanic rocks do not form well defined isochron. However, the alkali granites reveal low ${\epsilon}_{Nd}$(0) values, while the acidic metavolcanic rocks and the rare metal deposit both have significantly higher ${\epsilon}_{Nd}$(0) values. Considering such differences, we propose following generation hypothesis: The acidic metavolcanic rocks around Chungju iron deposit was erupted at 750 Ma as rest of the acidic metavolcanic rocks of Gyemyeongsan and Munjuri Formations. About 330 Ma ago, partial melting of existing Al-type igneous materials and some old crustal materials produced alkali granite. The rare metal deposit was also produced by redistribution of related materials within the acidic volcanics due to hydrothermal activities occurred at the same time. Sm-Nd isotopic systematics of the acidic metavolcanic rocks were disturbed during the regional metamorphic event at ca. 280 Ma.

• Journal of Science Education
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• v.32 no.2
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• pp.121-145
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• 2008

The purposes of this study were to identify the misconceptions that students have on the magma and plate tectonics and to present the implications in developing textbooks as well as related curriculum of high school textbooks. Data were collected through questionnaire, consisting of some questions, short essays, and descriptive drawings, developed by the research team. A total of 140 high school students(9th graders) responded to those questionnaires and were interviewed for further information. It was reported that participants displayed various misconceptions related to magma and plate tectonics. The identified misconceptions are as follows: For the definition of magma, the 31% of participants misunderstood magma as lava. In respect to the generative mechanism of magma at subduction zone, over 90% of students responded that it is generated by frictional heat. The source of misconceptions were identified as a result from textbooks and related reference-books. For the concept of plates, 87% of students conceived 'crust or a lower part of the plates' as 'plates'. Most participants hold the right concept of oceanic ridge, whereas, 66% of them considered 'rift valley' as either 'divergence of continental plates' or 'converging boundary'. 63% of them defined 'collision boundary of continental plate' as either 'subduction zone' or 'diverging boundary'. For the definitions of the trench and Benioff zone, 86% of students responded them as the place of subduction or differing density between two converging plates. The students' misconceptions were resulted from the errors and insufficient explanation, inappropriate figures, and data presented in textbooks, reference-books, lecture, and web sites. The results of this study are implied to contribute the improvement of students' misconceptions.

• Journal of the Korean Geographical Society
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• v.40 no.6 s.111
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• pp.716-729
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• 2005

In the Yeongpyeong River, one of the branches of Hantan River, there 4 fluvial terraces are identified. During the Quaternary, lava flow from Hantan River had gone 4.5km into upstream Part of the Yeongpyeong River and damed its entrance, and resultantly its lower basin had become a lava-damed paleolake. This study deals with fluvial terrace surface classification, stratigraphic analysis, deposits analysis, and OSL age dating in from Gungpyeongri to Seongdongri in lower reach of Yeongpyeong River, in order to identify Seomorphological Process of the terrace landforms relating to duration of lava-damed paleolake. Terrace surface T4, named Baekeuiri Formation, has been located under Jeongok lava layer to indicate pre-lava river bed. Terrace surfaces T3 and T2 are supposed to be formed during paleolake time, based on $3{\~}4m$ thick sand deposits including pebble and cobble layers, and clay and silt layers intersected with sand ones in nearly horizontal bedding. Terrace T1 is estimated to be formed as post-lake fluvial terrace after dissection of lava dam, based on the more fresh phase of deposits and very low height from present riverbed. The results of the OSL age dating for the T3 deposit layers indicate approximately $33{\~}40ka$, and still lake phase at that time.