• The Journal of Engineering Geology
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• v.23 no.4
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• pp.399-407
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• 2013

Some groundwater in Korea contains high U concentrations, especially where two-mica granite occurs in the Daejeon area. The elemental U in the two-mica granite is lower than that in normal granites elsewhere in the world, and U-minerals have yet to be reported in the two-mica granite in the Daejeon area. This study focuses on investigating the occurrence of U-minerals serving as the U source in groundwater. In situ gamma ray spectrometry and mineralogical analyses using EPMA were performed. U-count anomalies were identified in a granitic dyke and in hydrothermally altered granite. Uraniferous granitic dykes occur along the contact zone between the two-mica granite and mica-schist. The uraniferous parts within the two-mica granite are developed in the hydrothermally altered zone, which contains numerous quartz veinlets within a fracture zone. Hydrothermal alteration is dominated by potassic and prophylitic alteration. Uraninite is a common U-mineral in granitic dykes and hydrothermally altered granite. Coffinite and uranophane occur in the hydrothermally altered granite. All of these U-minerals are commonly accompanied by hydrothermal alteration minerals such as muscovite, chlorite, epidote, and calcite. It is concluded that granitic dyke and hydrothermally altered granite are the main source rocks of U in groundwater.

• Economic and Environmental Geology
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• v.32 no.5
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• pp.519-535
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• 1999

Precambrian metasedimetay rocks in the Sunchang Shear Zone (so-called Seologri and Yongamsan Formation) consist of black slate, phylite, mica schistm quartzite and rarely calc schist. The metamorphic rocks in the area have undergone at least three stages of metamorphism, which are two prograde (M1 and M2) and one contact metamorphism (M3). The metamorphism which made the most prevailing mineral assemblages in the area, is M2 stage metamorphism. The metamorphic grade of M2 methamorphism in metapelites increases from the Chlorite zone through Biotituzone, Garnet zone to Staurolite zone. The M1 stage metamorphism is recognized by kyanite and sillimanite pressure type regional metamorphism. The M3 stage methamorphism is represented in the contact boundary, which area is the chlorite zone and biotite zone near the Sunchang foliated granite and the namwon granite. The M3 stage methamorphism is characterized by andalusite bearing mineral assemblages. The peak temperature condition of M2 metamorphism estimated from coexising garnet and biotite (Kretz, 1990) is 518~598$^{\circ}C$.

• Economic and Environmental Geology
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• v.26 no.3
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• pp.349-361
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• 1993

The granitic rocks in the study area are divided into the schist and gneiss complex, Yongdok pluton, Yonghae pluton and Onjong pluton by their texture, fabric and relationship to the adjacent rocks in the field, Schist and gneiss complex occurs as xenolith or roof pendant in the Yongdok, Yonghae and Onjong plutons. The Yongdok pluton occurs in association with pegmatite and aplite in many places of its pluton. In the field it is obviously clarified that the Yongdok pluton is unconformably overlay by the Cretaceous sedimentary rocks. The Yonghae and Onjong plutons are gradationally changed each other, and these plutons truncate both the Yongdok pluton and the Cretaceous sedimentary rocks. Petrographically, the Yongdok pluton consists of granodiorite and granite with minor quartz monzonite. The Yonghae pluton is composed of diorite, quartz diorite, tonalite, and granodiorite. The Onjong pluton also ranges granodiorite to granite. Both the Yongdok and Yonghae-Onjong plutons are different in the constituent minerals, such as alkali feld~par, myrmekite, mica, sphene and mafic minerals. This suggests that each pluton might have been different crystallization sequence and characteristically different gological history during the crystallization period. Iron/magnesium ratio in biotite and hornblende from both the Yongdok and Yonghae-Onjong plutons gradually decrease as the differentiation index increasing in the whole rock. The decrease of this ratio strongly depend on the increase of opaque mineral contents. From the results of chemistry in the whole rocks and some mafic minerals, it is suggest that the granite plutons of the two different geological ages would have been suffered the environment of high oxygen fugacity in the process of magmatic emplacement and during the crystallization period.

• Economic and Environmental Geology
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• v.30 no.2
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• pp.163-174
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• 1997

Precambrian metapelites and metapsammites of the Jinan-Osu area (so-called Seologri and Yongamsan Formation) consist of black slate, phyllite, mica schist, quartzite and rarely calc schist. They are intruded by Sunkagsan granite gneiss, Foliated granodiorite, Amphibolite, Sunchang foliated granite and Namwon granite. Mylonite texture, crenulation cleavage and minor shear zone are common. The meta-sedimentary rocks include various rock-fragments xenoliths in size (up to 3 cm) and rock-type. They have various porphyroblastic spots in size (up to 1 cm) and their mineral composition is different. The xenoliths are schists, granite and quartzite, which are rectangular or lens form and recrystallized muscovite, chlorite and quartz. Spots are andalusite and biotite aggregates extensively replaced by chlorite. The metamorphic terrain is divided into three zones of progressive metamorphism on the basis of mineral assemblage. They are chlorite zone, chloite-biotite zone and andalusite-biotite zone ascending order, from west to east approximately. Isograd reactions are phengitic muscovite + chlorite = less phengitic muscovite + biotite + quartz + $H_2O$ and muscovite + chlorite + quartz = andalusite + biotite + $H_2O$ between the chlorite zone and chlorite-biotite zone, and between the chloritebiotite zone and andalusite-biotite zone, respectively. Sample B6 (exposed near the Obong-ri) includes staurolites and greenish biotites, that is different in mineral assemblage and chemical composition from the meta-sedimentary rocks. Sample A12 (exposed near the Shinam-ri) has greenish white spots (up to 1 cm in diameter) mainly composed of Kfeldspar, quartz and sillimanite replaced by muscovite.

• Economic and Environmental Geology
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• v.30 no.6
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• pp.531-541
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• 1997

Unconsolidated sediments of Youngjong Island were investigated to consider the vertical distribution of clay minerals and their origin. At least three sedimentation units can be recognized by color, magnetic susceptibility, and pH. X-ray diffraction analysis of clay size fraction reveals that illite is the most abundant phase (52.06%), and chlorite (27.16%), kaolinite (16.92%), smectite (3.86%) occur next to it. Detailed XRD study suggests that illitic materials contain fairly large amount of ordinary muscovite derived from the mica schist in Youngjong Island and adjacent area. The relative amount of kaolinite and chlorite is less than those of samples from estuary mouth of several rivers that flow to Yellow Sea and South Sea. Especially smectite content of the present sample is much higher than those of estuary sediments. These indicate that the unconsolidated sediments of tidal-flat deposit in Youngjong Island are largely affected by marine influence and partly affected by sediment in influx from China. However, some degree of source of this unconsolidated sediments is inland origin from adjacent estuary sediment and in situ or nearby weathered materials.

• Economic and Environmental Geology
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• v.1 no.1
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• pp.9-34
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• 1968

Manganese ore deposits of the Samhan Changgun Properties are located at the valley of west-lope-side of Changgun-bong (1132m) occupied over the Myon border between Sochon-myon and Jaesan-myon Pongwha-gun, Kyongsang-Pukdo. Geology of the more property and it's vicinity consists of Wonnan formation and Yulri formation of pre-Cambrain and Changgun limestone formation, Mica-schist formation, quartizite formation and Jaesan formation (containing coal bearing zone the unknown age. And granites and dykes were intruded into the above formation later. 1. Management deposits is embedded the formation of Janggun limestone especially Contact zone in the contact zone to of Chunyang Granite limestone enclosed by Granite, and Maginal zone of fault line in the limestone. Therefore, Chunyang Granite is Closely related to ore deposit. Pegmatite which is near by ore deposit was intruded before mineralization and it seems to be a channelway of ore solution. The most important ore deposits of property grouped into south deposit, east deposit, east-Gachon deposit, South-Gachon deposit, Durimgok deposit and West deposit, out-crops at several place. Besides these deposits there also are several prospects on outcrop scathered. Hydrothermal alteration take place strongly in the well rock and it's sequence are Characterized as following; 1) Dolomitization 2) Carbonization 3) Mamgamotozation 4) Pyritization 5) Silicification 6) Oxidation 2. The grade of manganese dioxide is up to Mn 45% in Maximum, but generally, averaging Mn 30~35% of high grade ore and averaging Mn 30~32% of manganese carbonates are mined in his property.

• Economic and Environmental Geology
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• v.19 no.1
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• pp.19-24
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• 1986

The Samkwang mine is one of gold deposits distributed mainly in the southwestern province (Chungnam) of the Korean peninsula. Golds occur in quartz veins aged of $223{\pm}4MA$ according to K-Ar age dating from muscovite in a pegmatitic quartz vein. Quantz veins intrude Precambrian biotite-granite gneiss and mica schist of unknown age. Fluid inclusions in the quartz show a range of homogenization temperatures from 159 to $274^{\circ}C$. A calculated temperature from the isotopes of the galena-sphalerite pair is $375^{\circ}C$. Two phases-fluid inclusions homogenized either by liquid or vapor phase are frequently observed in specimens over $260^{\circ}C$, which may indicate the boiling of the fluids. Pressure of formation of the quartz veins inferred by the homogenization temperatures of liquid-$CO_2$ bearing fluid is 1kb. Based on these data, it is assumed that the temperature of the formation of the Samkwang mine may lie in between $350^{\circ}-230^{\circ}C$. ${\delta}^{34}S_{{\Sigma}s}$ values of sulphide minerals show narrow range of +2.1 to +4.6, and show a trend of enrichments of $^{34}S$ in the fluid from deep to the surface. ${\delta}^{34}S_{{\Sigma}s}$ in the fluid estimated is less than 3 permil, suggesting sulphur fluid originated from the magma.

• 보존과학연구
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• s.16
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• pp.123-128
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• 1995

For establishing the plan of scientific conservation on the Kyongch′onsa and site of Won-gaksa 10 floors pagodas, the investigation on the rocks consisting these pagodas has been made on the rock phase and weathering characteristics. The Kyongch′onsa pagoda consists of fine grained pale graylimestone containing abundant fossils of shell and fragments of organisms. The site of Won-gaksa pagoda is composed of marble of pale gray, white and/or light brown color, which is intercalated with thin mica schist. The marble, the recrystallized limestone, consists mainly of recrystallized calcite accompanied with minor amount of muscovite. Especially carbonate rocks are somewhat different in chemical weathering from such granitic rocks. The field survey and laboratory experiment using polarizing microscope had been done during 30 days from Feb, 13 to March, 31, 1995. The rocks equivalent to that of the site of Kyongch′onsa were identified from the Myobong limestone formation and taken samples around the road from P′yongch′ang to Mitan, P′yongch′ang-gun. The rocks similar to that of the site of Won-gaksa pagoda were distributed around Pan-un-ri, Chunch′on-myon, Yong-wol-gun. The rocks of the Silluksa pagoda consisting of white recrystallized limestone with banded structure are similar to the marble of the Hyangsan-riformation distributed around Suanbo, Ch′ungch′ongbuk-do.

• Journal of the Korean earth science society
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• v.21 no.3
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• pp.302-314
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• 2000

Keumseong area in the southern part of the Jecheon city, the Ogcheon Belt, consists of Precambrian Dangdusan Metamorphic Complex, Dori Formation of the Choseon Supergroup, and Jurassic Jecheon Granite. The Dangdusan Metamorphic Complex consists of quartz schist, mica schist. quartzite and pegmatite. The Dori Formation is composed of mainly laminated limestone. The rocks in the study area have been undergone at least three phases of deformations since Paleozoic period. The Dangdusan Metamorphic Complex is outcrop at three areas in the study area, which are exposed along the faults and occurred as inlier within the Dori Formation. Previous authors interpreted the uplift of the Dangdusan Metamorphic Complex by the Dangdusan Fault, but we could not find any evidences related to the Dangdusan Fault. Thus, we interpret the uplift of the Dangdusan Metamorphic Complex due to the D$_2$ Weolgulri and Dangdusan thrusts and post-D$_2$ Jungbodeul, Kokyo and Jungjeonri faults. The uplift of the Busan Metamorphic Complex to the west of the study area was interpreted by ductile deformation. However, the Dangdusan Metamorphic Complex is formed by brittle thrusts and faults in this study. According to deformation sequence, the characters of deformations in the Choseon and Ogcheon suprergroups had been changed from ductile to brittle deformations through the time. Therefore, we interpret the Dangdusan Metamorphic Complex is exposed later than the Busan Metamorphic Complex.

• Journal of Korean Society of Forest Science
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• v.104 no.4
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• pp.588-597
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• 2015

This study was carried out to identify the reasons of the landslide by land creeping in South Korea in order to provide basic information for establishing the management plan for prevention. Total 29 sites of landslide areas caused by land creeping were observed in South Korea. Among them, the soil-composition of most frequent landslide areas occurred by land creeping was colluvium landslide as 75.9% (22 sites), followed by clay soil landslide as 10.3% (3 sites), bedrock landslide as 6.9% (2 sites), and weathered rock landslide as 6.9% (2 sites). According to the types of parental rocks, the investigated landslide areas were divided into 3 types: 1) metamorphic rocks including schist, phylite, migmatitic gneiss, quartz schist, pophyroblastic gneiss, leucocratic granite, mica schst, banded gneiss and granitic gneiss, 2) sedimentary rocks including limestone, sandstone or shale and mudstone, 3) igneous rocks such as granite, andesite, rhyolite and masanite. As a result, it was noticed that the landslides occurred mostly at the metamorphic rocks areas (13 sites; 44.8%), followed by sedimentary rock areas (12 sites; 41.4%), and igneous rock areas (4 sites; 13.8%). Looking at the direct causes of the landslide, the anthropological activities (71%) such as cut slopes for quarrying, construction of country house, plant, and road, farming of mountain top, and reservoir construction were the biggest causes of the landslides, followed by the land creeping landslides (22%) caused by geological or naturally occurred (22%), and cliff erosions (7%) by caving of rivers and valleys.