• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.305-317
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• 2005

This study addresses the preliminary results of rock slope stability analyses including hazard assessments for slope failure conducted on the selected sections of rural road cut slope which are about 4 km long. The study area is located in the Mt. Chuntae northeast of Busan and mainly composed of Cretaceous rhyolitic ash-flow tuff', fallout tuff, rhyolitc and andesite. The volcanic rock mass in the area has a number of discontinuities that produce a potentially unstable slope, as the present cut slope is more than 70 degrees in most of the slope sections. Discontinuity geometry data were collected at selected 8 scanline sections and analyzed to estimate important discontinuity geometry parameters to perform rock slope kinematic and block theory analyses. Kinematic analysis for plane sliding has resulted in maximum safe slope angles greater than $65^{\circ}$ for most of the discontinuities. For most of the wedges, maximum safe cut slope angles greater than $45^{\circ}$ were obtained. Maximum safe slope angles greater than 80" were obtained fur most of the discontinuities in the toppling case. The block theory analysis resulted in the identification of potential key blocks (type II) in the SL4, SL5, SL6 and SL8 sections. The chance of sliding taking place through a type ll block under a combined gravitational and external loading is quite high in the investigated area. The results support in-field observations of a potentially unstable slope that could become hazardous under external forces. The results obtained through limit equilibrium slope stability analyses show how a stable slope can become an unstable slope as the water pressure acting on joints increases and how a stable slope under Barton's shear strength criterion can fail as the worst case scenario of using Mohr-Coulomb criterion.

• Economic and Environmental Geology
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• v.43 no.5
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• pp.467-475
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• 2010

The Landsat and ASTER data have been used in mineralogical and lithological studies, and they have also proved to be useful tool in the initial steps for mineral exploration throughout Nevada mining district, US. Huge pyrophyllite quarry mines, including Jungang, Samsung, Kyeongju, and Naenam located in the southeastern part of Gyeongsang Basin. The geology of study area consists mainly of Cretaceous volcanic rocks, which belong into Cretaceous Hayang and Jindong Group. They were intruded by Bulgugsa granites, so called Sannae-Eonyang granites. To extraction of Ratio model for pyrophyllite deposits, tuffaceous rock and pyrophyllite ores from the Jungang mine used in reflectance spectral analysis and these results were re-sampled to Landsat and ASTER bandpass. As a result of these processes, the pyrophyllite ores spectral features show strong reflectance at band 5, whereas strong absorption at band 7 in Landsat data. In the ASTER data, the pyrophyllite ores spectral features show strong absorption at band 5 and 8, whereas strong reflectance at band 4 and 7. Based on these spectral features, as a result of application of $Py_{Landsat}$ model to hydrothermal alteration zone and other exposed sites, the DN values of two different areas are 1.94 and 1.19 to 1.49, respectively. The differences values between pyrophyllite deposits and concrete-barren area are 0.472 and 0.399 for $Py_{ASTER}$ model, 0.452 and 0.371 for OHIb model, 0.365 and 0.311 for PAK model, respectively. Thus, $Py_{ASTER}$ and $Py_{Landsat}$ model proposed from this study proved to be more useful tool for the extraction of pyrophyllite deposits relative to previous models.

• 한국해양학회지
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• v.30 no.5
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• pp.480-492
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• 1995

Petrographic investigation has been carried out to determine the composition of the beach sediments and the affecting factors which have controlled their compositional variations from Hyupjae, Aeweol, Iho, Samyang, Hamdeok, Sehwa, Pyoseon, Jungmun, and Hwasun areas along the coast of the Cheju Island. Average mean sizes of the beach sediments are Hyupjae 2.2ø, Aeweol 0.8ø, Iho 1.4ø, Samyang 2.4ø, Hamdeok 1.6ø, Sehwa 1.5ø, Pyoseon 2.1ø, Jungmun 0.4ø, and Hwasun 0.9ø, thus, aries from 0.4 to 2.4ø. The beach sediments from Pyoseon and Hwasun areas are poorly sorted, those from Aeweol and Jungmun areas are moderately sorted and those from the rest of the areas are moderately well sorted. While-colored beach sediments in Hyupjae, Aeweol, Hamdeok, Sehwa, and Pyoseon areas are mostly composed of calcareous shells (more than 85%) such as mollusk, red algae, benthic foraminiferas, etc., whereas volcanic rock fragment is the dominant component of the black-colored beach sediments in Iho, Samyang, and Hwasun areas. Especially, the relatively white-colored beach sediment in Jungmun area, which is on e of the carbonate-dominant areas, shows a higher content of rock fragments than the other carbonate-dominant areas. The beach sediments in Pyoseon area show a high content of carbonate intercalates. Considering the contributions by organisms according to grain size, grains with the size range of 1∼2ø are mostly composed of calcareous red algae fragments, and grains with the size range of 2∼3ø consist of mollusk fragments. It is also notable that bryozoan fragments comprise about 48% of the sediment in Samyang area with the size range of 0∼1ø. The composition of the beach sediments in Cheju Island appears o be controlled by the riverine supply rate of volcanic rock fragments, the lithology of the rocks distributed ear the beaches, the direction of alongshore currents, and the direction of storms, etc.. It is suggested that the beach sediments in Iho and Samyang areas show black color because of the higher supply rate of the volcanic rock fragments from the nearby rivers, whereas those in the rest of the areas show white color due to the relatively lower content of volcanic rock fragments and higher content of carbonate components transported from shallow marine environment. In Hwasun area, the content of volcanic rock fragments is high, and they are directly from the tuffaceous rocks distributed nearby. Also, the volcanic rock fragments in Jungmun area are transported not only from the rivers nearby but also from the nearby tuffs by storm activities. The beach sediment in Pyoseon area contains a high content of carbonate intercalates, which formed in the nearby shallow marine environment through marine cementation. This indicates that active marine cementation occurs in shallow marine environment near Pyoseon area.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.205-217
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• 2024

This study evaluated the physical characteristics and quality of volcanic rocks distributed in the Jeju Island-Ulleung Island area as aggregate resources. The main rocks in the Jeju Island area include conglomerate, volcanic rock, and volcanic rock. Conglomerate is composed of yellow-red or gray heterogeneous sedimentary rock, conglomerate, and encapsulated conglomerate in a state between lavas. Volcanic rocks are classified according to their chemical composition into basalt, trachybasalt, basaltic trachytic andesite, trachytic andesite, and trachyte. By stratigraphy, from bottom to top, Seogwipo Formation, trachyte andesite, trachybasalt (I), basalt (I), trachybasalt (II), basalt (II), trachybasalt (III, IV), trachyte, trachybasalt (V, VI), basalt (III), and trachybasalt (VII, VIII). The bedrock of the Ulleung Island is composed of basalt, trachyte, trachytic basalt, and trachytic andesite, and some phonolite and tuffaceous clastic volcanic sedimentary rock. Aggregate quality evaluation factors of these rocks included soundness, resistance to abrasion, absorption rate, absolute dry density and alkali aggregate reactivity. Most volcanic rock quality results in the study area were found to satisfy aggregate quality standards, and differences in physical properties and quality were observed depending on the area. Resistance to abrasion and absolute dry density have similar distribution ranges, but Ulleung Island showed better soundness and Jeju Island showed better absorption rate. Overall, Jeju Island showed better quality as aggregate. In addition, the alkaline aggregate reactivity test results showed that harmless aggregates existed in both area, but Ulleungdo volcanic rock was found to be more advantageous than Jeju Island volcanic rock. Aggregate quality testing is typically performed simply for each gravel, but even similar rocks can vary depending on their geological origin and mineral composition. Therefore, when evaluating and analyzing aggregate resources, it will be possible to use them more efficiently if the petrological-mineralological research is performed together.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.121.2-121.2
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• 2010

제주도는 지질학적으로 제4기에 형성된 화산섬으로 지금까지 고온의 지열징후는 보고된 바 없으나, 남한에서 가장 최근까지 화산활동이 있었던 것으로 기록되어 있어 화산활동과 관련된 심부 지열자원 부존 가능성은 아직 열려있다고 할 수 있다. 본 연구에서는 제주도에서 지열부존 가능성을 타진하고 제주도 심부 지질구조 파악을 목적으로 2차원 및 3차원 자기지전류 (MT) 탐사를 수행하였다. 탐사는 중산간지역에서 한라산을 중심으로 동, 서, 남, 북의 4방향 4측선과 제주 서부지역에 남북방향의 1측선을의 총 5개 측선에 대해 수행하였으며, 이에 대한 MT 탐사자료의 2차원 및 3차원 역산을 통하여 한라산 하부 및 주변의 심부 지질구조를 파악하고자 하였다. 역산 해석 결과는 천부 구조는 기존 시추조사 결과 밝혀진 층서구조의 형태를 잘 나타내어 획득된 자료의 신뢰도가 높음을 지시하였다. 즉, 제주도 최 상부를 피복하고 있는 현무암 등의 화산암류는 고비저항(수백 ohm-m)으로, 그 하부의 해성 미고결퇴적층(U층 및 서귀포층)은 저비저항으로, 그리고 최하부의 응회암이나 화강암으로 구성된 기반암은 1,000 ohm-m 이상의 고비저항 층으로 잘 구분되어 나타났다. 특히, 제주도에서 특징적으로 해수면 하부 수십 ~ 수백 m에 존재하는 것으로 알려진 미고결퇴적층이 10 ohm-m 내외로 측선 전반에 걸쳐 나타났다. 이는 기존의 시추결과에서 미고결 퇴적층이 제주도 전역에 걸쳐 해수면 하부 100 m 내외의 심도에서 관찰되는 것과 일치하는 결과이다. 기반암 하부에서는 특징적으로 모든 측선의 중앙부에서 저비저항 이상대가 영상화되었으며 이는 2차원 역산과 3차원 역산해석에서 공통적으로 나타났다. 특히, 3차원 해석에서는 이러한 저비저항 이상대가 한라산 정상에서 서북쪽 부근에 나타나는데 이는 과거의 화산활동과 관련된 지질학적인 구조에 의한 영향일 가능성과 측선의 양단과 중앙에서 주변 바다의 영향이 다르게 나타나기 때문일 가능성으로 볼 수 있다. 즉, 전자는 심부에 발단된 각각의 파쇄대가 모든 측선의 중앙부에서 교차하거나 이를 통한 한라산의 생성과정과 연관된 지질학적인 구조일 가능성을 의미한다. 만약 한라산을 형성한 화성활동의 영향이 아직 지하 심부에 남아있다면 지열수의 부존 혹은 마그마의 통로가 되었을 단층의 영향으로 한라산 하부에 저비저항 이상대로 나타날 가능성이 높다. 그러나 후자에 의한 가능성도 배제할 수는 없으므로 향후 주변바다에 대한 영향을 고려한 3차원 역산해석이나 심부시추 등을 통한 상세한 지질조사 등 추가적인 연구가 이루어져야 할 것으로 판단된다.

• Journal of Conservation Science
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• v.18 s.18
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• pp.19-32
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• 2006

The stone pagoda of the Bunhwangsa temple made by piling small brick-shaped stones. The major rock forming stone bricks are andesites with variable genesis. Rock properties of the pagoda roof stone suffer partly including multiple peel-offs, exfoliation, decomposition like onion peels, cracks forming round lines and falling off stone pieces. The stylobates and tabernacles in all the four directions the pagoda are mostly composed of granitic rocks. Those rock properties are heavily contaminated by lichens and mosses with the often marks of inorganic contamination by secondary hydrates that are dark black or yellowish brown. Within the four tabernacles and northern pagoda body situated to relatively high humidity. There are even light gray precipitate looking like stalactites between the northern and western rocks of the body Their major minerals are calcite, gypsum and clays. The stone lion standing in the southeast and northeast side are alkali granite, while that in the southwest and northwest lithic tuff. Total rock properties of the pagoda are 9,708 pieces, among the all properties, fractured blocks are 11.0%, fall out blocks are 6.7% and covered blocks by precipitates are 7.0%, respectively. The pagoda has highly deteriorated the functions of the rock properties due to physical, chemical and biological weathering, therefore, we suggest that this pagoda has need to do long term monitoring and synthetic conservation researches.

• The Journal of the Petrological Society of Korea
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• v.13 no.1
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• pp.1-15
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• 2004

In this study we propose that the ‘enclaves’ which occur in the granites should be translated into ‘Po-yu-am’in Korean. Also we suggest some criteria to discriminate the mafic microgranular enclaves (MME) of igneous origin from the xenoliths, which possibly come from the plutonic, volcanic and sedimentary country rocks. The color of the MME is gray green∼dark gray and the mineral grains are fine and equigranular. The MME are generally of ellipsoidal shape and can be easily found within the granites. They do not show any evidence of contact metamorphism by granite host. On the other hand. the xenoliths are generally of angular shape and are of the same mineral assemblage and texture as the country rocks around the granites. The distribution of the xenoliths is mostly concentrated along the intruding plane of the granites near the country rocks. The xenoliths were partly metamorphosed by the granite intrusion. The xenoliths from the plutonic rocks are easily distinguished from the MME in terms of their angular shape and coarser grain size, but they do not have any metamorphic mineral assemblage and texture. The xenoliths from the tuffaceous rocks show angular shape and porphyritic and pyroclastic textures. Large size xenoliths from the sedimentary rocks specifically preserve bedding structure which are indicative of the sedimentary strata. However, the sedimentary xenoliths of small size are often difficult to distinguish from the MME. Metamorphic minerals and texture are a useful key to discriminate the small-sized sedimentary xenoliths from the MME. In summary the xenoliths in the granites can be megascopic ally distinguished from the MME by comparing their color, shape, grain size and remnant original structure like bedding. Additionally the metamorphic mineral assemblage and texture are microscopic discriminators between the xenoliths and the MME in the granites.

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.149-156
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• 2005

Ar-Ar, carbon AMS and OSL dating was carried out to clarify the age of the human footmarks on the Hamori Formation, Jeju Island, Korea. $^{40}Ar/^{39}Ar$ ages of trachybasalt from the Songaksan Tuff, which is underlain by the Hamori Formation, range between $10.6{\pm}19.9\;Ka$ and $11.7{\pm}26.3\;Ka$. Radiocarbon AMS ages of humin fractions extracted from sediment samples yielded the maximum limit age of the Hamori Formation as $15,161{\pm}70\;yr$ B.P. The OSL dating of the top and bottom layers of the Hamori Formation gave $6.8{\pm}0.3\;ka$ and $7.6{\pm}0.5\;ka$, respectively, suggesting that timing of the human footmarks formation can be constrained as between ca 6,800 yr B.P. and 7,600 yr B.P.

• Korean Journal of Plant Taxonomy
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• v.38 no.4
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• pp.583-599
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• 2008

Dokdo, small island located in the eastern end of the Korean Peninsula, has been an uninhabited island for long time due to long distance from the land. Moreover, the steep slope of volcanic tuff at Dokdo is well drained for high permeability and Dokdo has few plain areas, swamps and very thin soil layers. In this study, pollen analysis at Dokdo was attempted on the profile of organic sandy soil for the first time in Korea owing to the marine climate environment with high humidity and precipitation including snowfalls in spite of unprofitable condition geologically or geomorphologically. While many historical, political researches have been accumulated for territorial problem of Dokdo with Japan, natural scientific researches with field work are not sufficient, and few paleoecological researches have been done. As a result of pollen analysis, the ratio of the NAP(Non-Arboreal Pollen) and spore was higher than AP(Arboreal Pollen), and the vegetation change existed by showing dramatic decrease of AP at the upper layer. AP was composed of almost Pinus, and a little Alnus, Quercus, Betula, Carpinus, Picea and Ulmus. NAP was composed of Gramineae, Compositae, Chenopodiaceae Cyperaceae, Caryophyllaceae, Liliaceae, Umbelliferae, Artemisia, Lobelia, Rumex, Polygonum. Increase of the NAP such as Gramineae, Artemisia and Chenopodiaceae, they would mostly have been transported from the other areas because agricultural activity is impossible at Dokdo. While one reason of Pinus thunbergii decrease could be regarded as environmental change, the other reason would be lumbering of pine trees by human activity which is adapted to Dokdo environment.

• The Journal of the Petrological Society of Korea
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• v.23 no.1
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• pp.1-15
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• 2014

The Yeongam mineralized zone is located in the southwestern part of the Korean peninsula, including the Sangeun, Eunjeok and Baramjai mines. This zone is located in the northeastern part of the Mokpo-Haenam-Yeongam volcanic circular structure. The 13 sites of quartz vein with mineralization are developed in the Sangeun-Eunjeok-Baramjai area, within rhyolitic welded tuff, showing N-S or NNW trend with highly dipping to the west. The quartz veins occur as a single vein or a bundle of veins with width of 1-5 cm in each. The existence of faults parallel to the quartz veins indicates that the faulting occurred before and after the development of quartz veins and mineralization. The quartz veins and mineralized zone are displaced by NW-trending sinistral strike-slip faults. The extension of the Sangeun-Eunjeok mineralized belt is traced to the south, following a NNW-trending tectonic line, and the Au-Ag contents are analysed in the 12 sites of quartz veins. Contents of gold and silver are 12.3 g/t and 1,380.0 g/t in Eunjeok mine, 2.7 g/t, 23.5g in Sangeun mine, and <0.1 g/t, 5.7 g/t in Baramjai mine respectively. Therefore, a highly Ag-Au mineralized zone is not developed in the southern part of the studied area.