• Economic and Environmental Geology
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• v.52 no.4
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• pp.275-290
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• 2019

Geochemical study was conducted to elucidate the origin of fluorine (F) distributed in the rocks within the four areas of Yongyudo and Sammokdo, Incheon, which have been used as the source area of land reclamation for the $3^{rd}$ and $4^{th}$ stage construction sites of the Incheon International Airport. The main geology of the study area is Triassic biotite granite. Fluorine is contained at high levels in biotite granite, mylonite, and dykes (andesite and, basaltic-andesite). Furthermore, the higher concentrations of fluorine in the biotite granite can be contributed to fluorite. The results of microscopic analyses reveal that the fluorite was mostly observed as small vienlets together with quartz. This features support that fluorite was naturally formed due to the secondary process of hydrothermal fluids. In addition, fluorine was investigated to be highly enriched in a large amount of mica within the veins. In the case of mylonite, a high levels of fluorine was contributed to a large amount of sericite. The sericites contained in the mylointe, differently to those of the biotite granite, filled the micro-fractures of quartz formed as a result of mylonitization and included small cataclastic quartz grains. This indicates that fluorine was naturally enriched due to the alteration of hydrothermal fluids filling fractured zones formed by mylonitization. Consequently, the results of petrological and mineralogical study confirm that the fluorine distributed in the rocks within the Yongyudo and Sammokdo originated naturally.

• The Journal of the Convergence on Culture Technology
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• v.8 no.1
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• pp.507-512
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• 2022

The subjects of the study are the sedimentary rock slope of the Mesozoic Gyeongsang Supergroup, which has a high risk of failure. The rocks of the slope shall be sandstone, siltstone and dacite, and discontinuities shall develop beddings, shear joints, extension joints, and dacite dyke boundary planes. The type and scale of failure varies depending on the type of rock and the strike/dip of the discontinuities, but the planar failure prevails. Based on the face-mapping data, SMR, physical and mechanical testing of rocks, the critical equilibrium analysis, all representative sections required a countermeasure method because the acceptable safety factor during dry and rainy seasons were far below Fs=1.5 and Fs=1.2. After applying the countermeasure method, both the dry and wet conditions of the slope exceeded the allowable safety factor. In particular, the face-mapping data of the slope-face, the geological cross-sections of several representative sections perpendicular to the slope-face, and the critical equilibrium analysis and the presentation of countermeasure methods that have been reviewed based on them are expected to be reasonable tools for the slope stability.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2002.10a
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• pp.17-30
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• 2002

삼척-도계지역 일대에 분포하는 조선누층군의 풍촌층 석회석은 품위 및 암상에따라 상부고품위대와 하부석회암대로 분대가 가능한데, 이는 삼척-태백간을 북북동으로 흐르는 오십천을 경계로 서쪽에 분포하는 풍촌층과 비교할 때 다소간의 암상차이를 보인다. 즉, 풍촌층의 특징중에 하나인 중부백운암대가 본 역 일대에서는 백운암화가 미약하여 비교적 소폭으로 확인되며, 상부백색대 역시, 발달정도가 미약한 특징을 보인다. 시추탐사결과 확인된 삼척-도계지역의 풍촌층 상부고품위대는 일반적으로 상부백색대$(\pm15m)$ - 백운암대$(\pm5m)$ - 암회색대$(\pm50m)$로 구분되는 것으로 나타났다. 각각의 품위는 상부백색대 : CaO $53_4\~55.6\%$, 백운암대 : MgO $3.0\~18.4\%$, 암회색대 : CaO $50.4\~54.2\%$로 나타나 제철용으로의 사용이 가능하나 백운암대에 대한 선별채광이 부분적으로 요망된다. 이들 석회석은 오십천대단층의 수반단층인 수조의 NNE계열 정단층들에 의해 빈번히 단절되어 있으며 일부지역에서는 EW향의 역단층에 의해 규제되기도 한다. 상기 제단층들은 석회암층을 단절시킬 뿐만 아니라 단층각력, 단층점토, 암맥 등의 불순대를 수반하므로 개발에 장애요소가 되고 있다. 상부고품위대 부존표고는 지역에 따라 다소 차이가 있으나 200ML 내외에서 대부분 확인이 가능하며 지표노출 규모는 작은 편이나 $10^{\circ}$이하의 완경사로 화절층 하부에 부존되어 있어 갱도 채광에 적합한 형태를 이루고 있다.

• Proceedings of the KSEEG Conference
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• 2002.10a
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• pp.17-30
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• 2002

삼척-도계지역 일대에 분포하는 조선누층군의 풍촌층 석회석은 품위 및 암상에따라 상부고품위대와 하부석회암대로 분대가 가능한데, 이는 삼척-태백간을 북북동으로 흐르는 오십천을 경계로 서쪽에 분포하는 풍촌층과 비교할 때 다소간의 암상차이를 보인다. 즉, 풍촌층의 특징중에 하나인 중부백운암대가 본 역 일대에서는 백운암화가 미약하여 비교적 소폭으로 확인되며, 상부백색대 역시, 발달정도가 미약한 특징을 보인다. 시추탐사결과 확인된 삼척-도계지역의 풍촌층 상부고품위대는 일반적으로 상부백색대($\pm$15m) - 백운암대($\pm$15m) - 암회색대($\pm$50m)로 구분되는 것으로 나타났다. 각각의 품위는 상부백색대 : CaO 53.4~55.6%, 백운암대 : MgO 3.0~l8.4%, 암회색대 : CaO 50.4~54.2%로 나타나 제철용으로의 사용이 가능하나 백운암대에 대한 선별채광이 부분적으로 요망된다. 이들 석회석은 오십천대단층의 수반단층인 수조의 NNE계열 정단층들에 의해 빈번히 단절되어 있으며 일부지역에서는 EW향의 역단층에 의해 규제되기도 한다. 상기 제단층들은 석회암층을 단절시킬 뿐만아니라 단층각력, 단층점토, 암맥 등의 불순대를 수반하므로 개발에 장애요소가 되고 있다. 상부고품위대 부존표고는 지역에 따라 다소 차이가 있으나 200ML 내외에서 대부분 확인이 가능하며 지표노출 규모는 작은 편이나 $10^{\circ}$이하의 완경사로 화절층 하부에 부존되어 있어 갱도 채광에 적합한 형태를 이루고 있다.

• The Journal of the Petrological Society of Korea
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• v.12 no.3
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• pp.119-134
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• 2003

Yuksipryeong two-mica granite presents strongly peraluminous characteristics in both mineralogy and geochemistry. It has high aluminum saturation index with 1.15∼l.20 and high corundum with 2.20∼2.98 wt% CIPW norm. As the color index is <16% and FeO$\^$T/+ MgO + TiO$_2$is average 1.9 wt％, it corresponds to leucogranite. Yuksipryeong two-mica leucogranite shows negative linear trend for TiO$_2$, Al$_2$O$_3$, FeO, Fe$_2$O$_3$, MgO, CaO, K$_2$O, P$_2$O$\_$5/, Rb, Ba, and Sr as SiO$_2$increases, and the positive relation of Zr and Th, which result from feldspar, biotite, apatite and zircon fractionation. Pegmatitic dike has higher SiO$_2$and P$_2$O$\_$5/, but lower another major elements. Yuksipryeong two-mica leucogranite has lower Rb, but higher Ba and Sr than Manaslu, Hercynian two-mica leucogranites, and S-type granites in Lachlan Fold Belt. Pegmatitic dike has higher Rb and Nb but lower Ba, Sr, Zr, Th, and Pb contents than Yuksipryeong two-mica leucogranite, resulting in removing or mobilizing for some trace elements from the granitic melt. Yuksipryeong two-mica leucogranite has total REEs with 95.7∼l23.3 ppm, and chondrite-normalized REE pattern is very steep ((La/Yb)$\_$N/ = 6.9∼24.8), light REEs (LREEs)-enriched End heavy REEs (HREEs)- depleted pattern with low to moderate Eu anomalies (Eu/Eu＊= 0.7∼0.9). While pegmatitic dike has low total REEs with 7.0 ppm, and chondrite-normalized REE pattern is flat-pattern ((La/Yb)$\_$N/ = 2.1) with strong negative Eu anomalies (Eu/Eu＊= 0.2). The melt compositions having formed two-mica leucogranites depend on not only the source rock but also the amounts of the residual remaining after melting of source rocks. The CaO/Na$_2$O and Rb/Sr-Rb/Ba ratios depend mainly on the composition of source rocks in the strongly peraluminous granite, that is, plagioclase/clay ratio of the source rocks. Yuksipryeong two-mica leucogranite has higher CaO/Na$_2$O and lower Rb/Sr-Rb/Ba ratios than Manaslu and Hercynian two-mica leucogranites (Millevaches and Gueret) derived from clay-rich, plagioclase-poor (polite), which suggest that the probable source rocks for Yuksipryeong two-mica leucogranite is clay-poor, plagioclase-rich quartzofeldspathic rocks. As the concentrations of Al$_2$O$_3$remain nearly constant but those of TiO$_2$increases as increasing temperature in the strong peraluminous melt, the Al$_2$O$_3$/TiO$_2$ratio may reflect relative temperature at which the melts have formed. Comparing the polite-derived Manaslu and Hercynian two- mica leucogranites, Manaslu two-mica leucogranite has higher Al$_2$O$_3$/TiO$_2$ratio than latter, and its melt have formed at relatively lower temperature ($\leq$ 875$^{\circ}C$) than Hercynian two-mica leucogranites. Likewise, comparing the quartzofeldspathic rock-derived granites, Yuksipryeong two-mica granite has higher Al$_2$O$_3$/TiO$_2$, ratio than S-type granites in Lachlan Fold Belt (>875$^{\circ}C$). The melt formed Yuksipryeong two-mica leucogranite are considered to have been formed at temperature at below the maximum 875$^{\circ}C$C$.

• The Journal of Engineering Geology
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• v.2 no.1
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• pp.70-91
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• 1992

Cheju and Oahu island are similar in geology, characterized by same types of volcanic activities during the late Tertiary to the early Quaternary. The occurrence of groundwater in both islands depend on two basic elements, permeability of volcanic rocks and precipitation. However, groundwater occurrence in Oahu is much more controlled by dike complex in the regional volcanic rocks. There are two different types of groundwater in both islands. One is perched groundwater standing at any high altitude, and the other is basal groundwater developed near the coastal area. The groundwater quality of Cheju island is good in general for drinking. But many wells near the eastern coastal area are salt intruded due to over pumping activities and the area of salt water intrusion has increased landward from the year of 1970. This feature of salt water contamination is similar at Pearl Harbour in Oahu island. In order to prevent this salt water contamination into fresh groundwater reservoir on Cheju island, it is urgently asked to make groundwater flow study along the coastal area on terms of groundwater potentials and their maximum ultimate exploration.

• Economic and Environmental Geology
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• v.3 no.2
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• pp.123-133
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• 1970

위에서 상논(詳論)한것을 요약(要約)하면, 1) 본(本) 지성(地城)을 구성(構成)하는 지질(地質)은 신나통(新羅統)의 퇴적암류(堆積岩類), 이를 관입(貫入)하는 불국사순(佛國寺純)의 화강록암(花崗綠岩) 및 암맥(岩脈)으로 되어 있다. 2) 광구일대(鑛區一帶)의 퇴적암류(堆積岩類)는 원내(原來)의 퇴적상(堆積相)과 화강섬록암(花崗閃綠岩)의 관입등(貫入等)으로 규화(珪化)되 어 규암(珪岩) 또는 규화(珪化)된 혼펠스로 변(變)하여 있다. 3) 지질구조(地質構造)는 단순(單純)한 배사(背斜)를 나타내 며 퇴적암(堆積岩) 및 화강섬록암중(花崗閃綠岩中)에 수(數) sets의 절이(節理)가 발달(發達)하여 이들에 따라 광화작용(鑛化作用)이 이루어졌다. 4) 광상(鑛床)은 퇴적암(堆積岩) 및 화강섬록암중(花崗閃綠岩中)의 열하에 연(沿)하여 배태(胚胎)하며 연(軟)망간광(鑛) 광맥(鑛脈)과 금은광맥(金銀鑛脈)의 2종(種)이 발달(發達)된다. 5) 금은광맥(金銀鑛脈)은 맥폭(脈幅)이 좁고 주향방향(走向方向)의 연장(延長)이 단속(斷續)되 며 분석결과(分析結果) 금(金)은 없고 은(銀)은 23.3g/t 내지(乃至) 913.3g/t 이여서 가행가치(稼行價直)가 없다. 6) 망강광맥(鑛脈)은 수조(數條)있으나 주목(注目)만한 것은 제(第)4갱맥(坑脈)과 제(第)5갱맥(坑脈)으로서, 전자(前者)는 연장(延長) 120m, 평균맥폭(平均脈幅) 0.5m 추정(推定)되며, 평균품위(平均品位)는 Mn 약(約) 17.5%이다. 후자(後者)도 연장(延長) 120m, 평균맥폭(平均脈幅) 0.6m 추정(推定)되며, 평균품위(平均品位)는 15.7%이다. 7) 광맥(鑛脈)은 후화강섬록암시기(後花崗閃綠岩時期)의 열하의 방위(方位)에 지배(支配)받으며, 주향(走向) 및 경사방향(傾斜方向)으로 전변(轉變)한다. 그러나 규암질모암(珪岩質母岩)의 성질(性質)로 보아 광상(鑛床)이 팽대(膨大)하여질 가능성(可能性)은 없다. 8) 망간 및 금은광맥(金銀鑛脈)은 열수광상(熱水鑛床)에 속(屬)한다.

• The Journal of Engineering Geology
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• v.27 no.4
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• pp.417-427
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• 2017

This study aims to present cases of rock slope failures caused by geological structures. Status of slope failures, results of cause analysis and stabilizing methods are introduced, focusing primarily on rock slope failures caused by specific geologic structures, such as intersection of faults infilled with clay, foliation and fault shear zone by dike intrusion and deep-seated clayey layer along lithologic boundary. Detailed geological survey, geophysical exploration and boring survey were conducted for cause analysis. Stabilizing method to prevent further slope failures and to ensure long-term stability of slopes were established, considering characteristics of geological structures, types of failure and geological conditions.

• Journal of the Korean earth science society
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• v.22 no.6
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• pp.548-557
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• 2001

Ultramafic rocks in the Yesan talc ore deposits area are unknown age plutonic rocks which intruded PreCambrian Yoogoo gneiss, and were intruded by Jurassic biotite granite, and Cretaceous acidic and mafic dykes. The ultramafic rocks consist mainly of serpentinite with some amphibolite and talc ore body. The serpentinites are divided 5 rock types (S1${\sim}$S5) on the basis of the developed degree of serpentine phenocrysts and layerings. It seems that the original rocks of the serpentinites were co-magmatic peridotites (dunite and pyroxene peridotite). Main serpentinization from the original rocks was occurred during amphibolite facies regional metamorphism in Choongnam area which Yoogoo gneiss was affected. Main steatitization from the serpentinites was hydrothermal alteration by ascended hydrothermal fluid through crush zones.

• Journal of the Korean earth science society
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• v.26 no.6
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• pp.584-596
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• 2005

Morphology, surface sediments, sedimentation rates and sea-cliff erosion have been monitored, for one year to investigate the shoreline changes and tidal beach characteristics in Cheonsu Bay along the west coast of Korea. The seacliff of the bay consists of intensively weathered sedimentary rocks and soft soil, showing an erosion range of $-58.9\~73.3cm/yr$ by a weak wave forcing. Active sea-cliff erosions are recognized by peculiar geomorphic features, including saw teeth-shaped coastline, gravels, relict weathered basement-rock and 'Island Stack' exposed on the high-tide beach surface. The beach sediments show low compositional maturity at the south and north headlands and gradually high towards the central part. This observation seems to be caused by the fact that beach sediments are to originate from the both headlands in the study area and then transported by long-shore current associated with a wave action.