• Water for future
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• v.8 no.2
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• pp.30-40
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• 1975

Hydrogeological survey and geophysical prospecting have been carried out in Saudi Arabia for the purpose of finding groundwater in the soil and rock at the request of General trading company in Jeddah, Saudi Arabia. The surveyed area is located on $38^{\circ}-39^{\circ}$ 30' in longitude and $26^{\circ}-26^{\circ}$ 30' in latitude. The topography of this area is dominated by northwest southeast mountain range composed mostly of precambrian rocks and basalt of tertiary period. Geology is mainly composed of greenstone, granite, andesite, diorite rhyolite of pre-cambrian era and sandstone of cambrian period which are underlained by basalt and andesite of tertiary period and alluvium of quaternary unconformably. The instruments used in this investigation are TR-18B2 radioactivity unit which isjapanese patented and A.C. Terrameter, a resistivity meter manufactured by ABEM of Stockholm, Sweden. Radioactivity method has been conducted along the Alula-Khaybar road, totally 164Km by the car-borne. As a result of the above survey 16 places have been selected and these anomalies show 1.2N-1.6N compared to background of each area in intensity with width of 10-50m. Resistivity vertical profiling which made use of Schlumberger configuration method has been made over selected areas by radioactivity method to provide hydrogeological information for a water resources survey. The result of resistivity shows that good aquifers are located in the western part of surveyed area where sedimentary rock is distributed. The strata showing 10-50, ${\Omega}-m$ in resistivity are thought to be waterbearing layer. The variations in aquifer resistivity found, are thought to be due to verying clay content, which could be related to aquifer yield. It has proved impossible to detect small salinity variation in the buried aquifer by geophysics. As a result of resistivity prospecting 10 places are recommended to be drilled at the anomalies as shown attached map. yields from the proposed holes have been estimated approximately from $20m^3$ to $200m^3$ per day. Prior to drilling for groundwater, test boring using ${\c}4"$ should be drilled in order to obtain more reliable hydrogeological information for the construction of perfect wells.ells.

• The Journal of the Petrological Society of Korea
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• v.8 no.1
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• pp.34-45
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• 1999

Mafic granulite xenoliths are found in precambrian porphyroblastic gneiss of the Mt. Jiri area, SW Sobaegsan massif, Korea. The xenoliths are rounded to ellipsoidal in shape, 50-100 cm in length and coarse-grained with granoblastic and foliated texture. The xenoliths consist of orthopyroxene, garnet, biotite, plagioclase, quartz, ilmenite and secondary orthoamphibole. Orthopyroxene is mostly resorbed and rimmed by coronitic orthoamphiboles. Garnets occur as porphyblasts and are zoned with higher pyrope content in cores than in rims. Geothermo-barometry results yield conditions of about $800-850^{\circ}C$, 6 kb and $500^{\circ}C$, 4 kb for early and retrograde stages of equilibration, respectively. According to available geochronological data, it is suggested that the granulite facies metamorphism occurred prior to 2.1-1.9Ga and that the area was superimposed by the high-grade (over $600-700^{\circ}C$) metamorphism between 1.9-1.7Ga, followed by cooling during uplift.

• The Journal of the Petrological Society of Korea
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• v.13 no.3
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• pp.152-160
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• 2004

$^{40}Ar-^{39}39/Ar$ ages were determined from the biotites and plagioclases separated from the Precambrian gneisses of Gyeonggi Massif. Biotites yield $1,294{\pm}46,\;1,241{\pm}39\;and\;1,217{\pm}39Ma(2{\sigma}\;errors)$, and plagioclases yield $934{\pm}25,\;872{\pm}19,\;819{\pm}15(2{\sigma})Ma$. These ages are significantly different from the U-Pb zircon ages obtained from the identical samples ($1,613{\pm}51~2,168{\pm}24Ma(2{\sigma})$, Song et al., 2001). The ages of biotites and plagioclases can be interpreted to represent independent regional thermal events. The Mesoproterozoic ages recorded by the biotites can be interpreted as a consequence of regional metamorphism followed by differential uplift. We propose that plagioclases record Neoproterozoic ages which are related with igneous activities under the regional extensional regime, related with the breakup of the supercontinent Rodinia existed at that time.

• Journal of the Mineralogical Society of Korea
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• v.7 no.1
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• pp.1-13
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• 1994

The industrial minerals play an important role in mining sector. More than 70 % of total mineral production come from industrial mineral sector. This paper reviews geological occurrence of kaolin, pyrophyllite and limestone, and current demand-supply status of major industrial minerals in the Republic of Korea. The kaolin is mainly distributed in the Kyeongsang province, formed by deep weathering of Precambrian anorthosite on mountainside of gentle slope. The pyrophyllite mainly occurs in the Kyeongsang and Chulla provinces, formed by hydrothermal alteration of late Cretaceous andesitic and rhyolitic rocks. Pyrophyllite comprises massive and lenticular bodies and contains minor amounts of kaolin, alunite and pyrite, in some places andalusite and illite. The limestone(Great Limestone Series of Cambrian age) is distributed widely in the Kwangwon and Chungcheong provinces. The limestone bodies are approzimately 70 km long and 3 km wide, elongated NE-ward, and show high grade of CaO content. In 1992, the self-sufficiency ratio of 44 nonfuel (metallic and non-metallic) minerals was no more than 30 percent. However, the ratio of 27 industrial minerals (non-metallic) represents high value of about 72 percent. The export/productjon ratio of the industrial minerals shows decreasing patterns from 12.2 % in 1983 to 4.2 % in 1992. Also the import/production ratio shows rapidly decreasing pattern from 84 % in 1983 to 38.2 % in 1992.

• Economic and Environmental Geology
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• v.10 no.1
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• pp.1-18
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• 1977

Chongyang tungsten ore deposits, one of the most important tungsten mines in South Korea, me open space filling hydrothermal vein deposits embedded in Precambrian biotite gneiss and, Cretaceous (?) granite porphyry. Some wolframite-bearing quartz veins are closely associated with -quartz porphyries which strike about $N15^{\circ}-25^{\circ}W$ and dip $800^{\circ}SE$ to vertical. Mineralization took place in near vertical vein systems of 5 to 2000 meter long in the biotite gneiss and granite porphyry stock during early Cretaceous and Tertiary (?) period. The hydrothermal mineral paragensis has indicated that there were two major stages: vein and vug stages. The principal vein mineral is wolframite in a gangue of quartz with small amount of fluorite, pyrite, beryl and carbonate minerals. Present in minor amounts are molybdenite, bithmuthinite, native bismuth, arsenopyrite, galena, chalcopyrite, pyrrhotite, sphalerite and scheelite. Fluid inclusion study from the minerls at Chongyang mine reveals that vein stage fluids attained a temperature range of $200^{\circ}C-355^{\circ}C$ and vug stage $160^{\circ}C-350^{\circ}C$. The filling temperatures show the higher range of $200^{\circ}-355^{\circ}C$ in quartz and $280^{\circ}C-348^{\circ}C$ in beryls, whereas the lower emperature range of $283^{\circ}C-295^{\circ}C$ in rhodochrosite and $160^{\circ}-253^{\circ}C$ in fluorites. These temperatures are in reasonably good agreement with mineral paragnesis in this ore deposits. Volfamite minerals were analysed for major components. $WO_3$, MnO and FeO by wet chemical method. Chemical analysis indicates that they contain 70.56-71.54% $WO_3$, 8.52-10.01% MnO and 10.00-11.58% FeO. MnO/FeO ratios of wolframites shows the range of 0.78-0.94 which maybe indicates a comparatively high temperature type of hydrothermal deposits.

• Economic and Environmental Geology
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• v.10 no.1
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• pp.19-35
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• 1977

The study area is located in between Hacheonri and Weolgulri, Jecheon-gun where the formations of Okcheon group and Chosun group come in contact and the stratigraphy and geological age of the Okcheon group have been debated among previous workers. The dolomitic limestone which distributed at Cheongam and Dumusil is clarified as the Hyangsanri dolomite formation and the quartzite distributed at Cheongam and Howeunri as Taehyangsan quartzite formation. The newly named Soorumsan schist interbedded in the Great Limestone Series was previously classified Seochangri formation. It is also classified that the formation formerly named as Seochangri was divided into newly named Manji schist which seems to be correlated to Kemyeongsan and Munjuri formation. The formation formerly named as Buknori is clarified as Hwanggangri formation. The Samtaesan formation has been clarified as the lower and upper limestone beds which belong to the Great Limestone Series. The area divided into two groups, that is, Okcheon system of Pre-cambrian age occupies western part and the Great Limestone Series of Chosun system of Cambro-Ordovician age eastern part of this area. Okcheon system consists in ascending order of Manji schist, Hyangsanri dolomite, Taehyangsan quartzite, Munjuri schist, and Hwanggangri formation of meta-tillite. The Great Limestone Series of Chosun group consists in ascending order of lower limestone, Soorumsan schist, Hoosanri quartzite and upper limestone formations. Busan augen gneiss seems to be igneous origin. Unmetamorphosed shale interbed can be traced in the Soorumsan schist. Previous study (Kims, 1974) reveals that meta-volcanic rocks are distributed from south to north along contact zone of the Okcheon and Chosun groups, and it has been confirmed that the meta-volcanics crop out continuously from the adjacent southern quardrangle into the southern part of the area studied, intruding along the fault zone between the Okcheon and Chosun groups which seems to be upthrust as in the area south. This evidence coincides with Kims' work (1974) which states that the Precambrian Okcheon group is largely overturned and thrusted over the Chosun group.

• Economic and Environmental Geology
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• v.34 no.4
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• pp.319-328
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• 2001

The Fe-REE deposit of the Hongcheon-Jaeun district occurs in Precambrian gneiss, and is classified into two ore bodies: the Jaeun ore body (northern ore body) and the Hongcheon ore body (southern ore body). Ecomonically important minerals consist of magnetite, monazite, strontianite and barite. Based on mineral assemblages and textures, the mineralization can be classified into two stages (Na-carbonatite stage and Fe-carbonatite stage). Main REE minerals were precipitated during the Fe-carbonatite stage. Some evidences of the carbonatite origin include: 1) strontianite-monazite exolution texture, 2) strontianite-barite exolution texture, 3) the occurrence of acmite of igneous origin at the area with abundant rare earth minerals, 4) the occurrence of the mineral assemblage consisting of carbonate minerals + magnetite + REE minerals. Therefore, we suggest that Fe-REE mineralization in the study area was related to carbonatite of igneous origin.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.119-122
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• 1998

Chemical analysis, measurement of pumping rates of 60 production wells and depth to water tables of 57 monitoring wells were carried to protect depletion of water resources and deterioration of water quality for the commercial portable ground-water. Borehole depth of production well averages 149m(31 boreholes), casing depth is 28m(29 boreholes), production rate is 70 $m^3$/day and depth to water table of monitoring well is 23.26m, respectively. The geology of 60 wells can be divided into Daebo granite(20), Okchun metarmorphic complex(18), Precambrian granitic gneiss(15), Bulguksa granite(4), Cheju volcanics(2), Cretaceous sedimentary rock(1). Average electrical conductivity and pH are 152$\mu$S/cm, and 7.35, respectively. The contents of major cation and anion predominantly $Ca^{2+}$>N $a^{+}$>M $g^{2+}$> $K^{+}$ and HC $O_{3}$$^{－}$ >S $O_{4}$$^{2-}$>Cl￣>F￣. Water type is predominantly $Ca^{2+}$-HC $O_{3}$$^{－}$(81.7%). It's possible that water chemistry of some wells were affected not only by the geology of boreholes penetrated but by inflows of surface water or shallow ground-water. Therefore, it is strongly necessary to steadily monitor the water quality and hydrogeologic conditins of production wells.ells.ls.ells.

• Journal of the Korean earth science society
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• v.26 no.7
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• pp.661-667
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• 2005

It was preliminarily considered that Jangdo wetland was a concave landform formed by the weathering of granite intruding Precambrian silicified metasedimentary rocks. Various granite-weathered topography was observed. The formation scenario of Jangdo wetland is as follows. By flood or slope mass movement of regolith, rock fragments were moved to form a low-relief slope landform. As a result, wetland was formed. By analyzing the slope soil and wetland sediment, we conjectured that Jangdo wetland depended on the influence of peripheral slope soil. In these concavelandform environment, the supply of water and organic materials was sustained for a long time to form a organicnondegradable wetland environment. In addition, the plants appropriate to this wetland environment were settled to thicken the wetland. This is how the present Jangdo wetland was thought to be formed.

• The Journal of the Petrological Society of Korea
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• v.15 no.2 s.44
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• pp.81-89
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• 2006

Pb isotopic compositions were determined from the ore deposits of Beonam, Dongjin, Jeoksang and Bukchang mines distributed within Jeolabuk-do. As a result, individual mine shows significantly different values of Pb isotopic compositions from each other. Pb isotopic values of the Beonam, Bukchang and Dongjin mines altogether from linear variation, but it is too steep to represent their formation age. Instead, such trend suggests that these ore leads were originated from binary mixing. Precambrian basement rocks and Mesozoic granitoids are suggested for such two end-members. The relative contribution of lead from each source seems to be quite different for each ore deposit, implying that the circulation of the ore-forming fluid was very localized when they were formed. In the case of Dongjin mine it seems significant portion of the ore leads were originated from the basement rocks, which suggests that related igneous rock seems to have acted as heat source to generate circulation of the fluid rather than the source of the ore-forming elements.