• The Journal of the Petrological Society of Korea
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• v.9 no.3
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• pp.121-141
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• 2000

Granitic and pophyroblastic gneisses are widely distributed in the Seungju-Suncheon area, the southwestern part of the Sobacksan Massif. Two groups of metamorphic P-T conditions are recognized from granitic gneiss. $622-760^{\circ}C/6.2~7.4\;kbar$(Group I) are estimated from garnet cores and samples with weak retrograde metamorphism. $606~785^{\circ}C/3.7~5.4\;kbar$(Group II) are estimated from garnet rims which have lower pyrope and higher spessartine contents due to the effect of retrograde metamorphism. The metamorphic P-T conditions estimated from porphyroblastic gneiss are $489~669^{\circ}C$, 2.1~4.8 kbar which are similar to the P-T conditions of Group II in the granitic gneiss. The whole rock-garnet Sm/Nd isotopic ages determined from granitic and porphyroblastic gneisses are, respectively, $1417{\pm}52\;Ma\;and\;1421{\pm}14\;Ma$. These date indicate that intermediate-P/T type metamorphism represented by Group I may have occurred between the intrusion of granite gneiss and the intrusion of porphyroblastic gneiss(between 1890 Ma~2120 Ma) and two gneisses experienced low-P/T type metamorphism after the intrusion of porphyroblastic gneiss at 1417~1421 Ma.

• Economic and Environmental Geology
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• v.13 no.3
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• pp.185-192
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• 1980

The rocks exposed in the investigation area are andesite of Late Cretaceous age, and syenite and aplitic granite of Bulgugsa Series of Early Cretaceous Period, which is intruded in the older andesitic rock. The strike and dip of major joint is $N10^{\circ}$ to $60^{\circ}E$, and $70^{\circ}SE$ to vertical respectively. According to seismic exploration, lower velocity zone, deemed to be fractured and/or crushed zone, is appeared along the gully center of east flank of the area. Test drilling shows that andesite bedrock is mostly very hard, massive, and very fine to medium grained and has almost 100 percent RQD and core recovery. In comparision with andesitic bedrock, intruded syenite cores show that it is highly crush especially at the depth from 55m to 63m.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.197-212
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• 2020

This study was carried out material characteristics and firing conditions for some potteries in early and middle Neolithic period at the Munamri sites, where the first farmland remails were found in Korea. It is divided into six kinds of surface patterns for potteries such as the raised, bamboo tube and red painted (patternless) from the early Neolithic period (BC 4000 to 6000), and the patterns of horizontal herringbone, short slanted lined or lattice and incised thick line in the middle Neolithic period (BC 3000 to 4000), respectively. Based on the color measures, redness and yellowness of potteries were relatively high as condition of oxidation firings, were also observed black cores on the cross section of potteries. The firing temperature is divided into two groups having under 800℃ and 800to 900℃, the difference in patterns of the potteries are not confirmed. As a microtextures, the bamboo tube pattern potteries show the sericitization biotite, the quartz have developed a suture line textures, and altered alkali feldspars are occurred. X-ray diffraction analysis shows that the main minerals contained in potteries are chlorite and amphibole besides quartz, alkali feldspar and biotite. Considering the geology around the Munamri area is the biotite amphibole granite and soil layers within 10km radius are used as the raw materials for the potteries. The raw materials are presumed that the sources from the metamorphic rocks along the water systems through the mountains around the sites on the basis of well developed suture line textured quartz in potteries. Results on normalized geochemical compositions, the potteries by surface patterns are very similar to sources, and it is judged that was made by using the surrounding soils despite the long time difference from the early to middle in the Neolithic period.

• Geophysics and Geophysical Exploration
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• v.20 no.3
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• pp.137-145
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• 2017

High-grade limestone applied to various chemical industries is abundant within upper Pungchon formation in Taebaeksan basin, South Korea. Geophysical exploration is one of the most efficient methods to investigate subsurface geological structure in an extensive area. Since the geophysical exploration for the high-grade limestone has rarely been conducted in Korea, its appropriate strategy has not been set up yet. In this study, we focused on to suggest the reasonable strategy and accumulate geophysical databases which are essential for interpreting geophysical images by characterizing laboratory physical properties of in-situ rocks. Hence, rocks were obtained from drilled cores consisting of lower Hwajeol formation, Pungchon formation, and dykes in Jeongseon area, Gangwon province. Geophysical laboratory experiments and petrography of the rocks were conducted. Since susceptibility values of the rocks in Pungchon Formation were obviously lower than those of upper Hwajeol and dykes, it is considered that the lithological boundaries could be distinguished by magnetic survey. In addition, electrical properties of the rocks in middle Pungchon formation were relatively different compared with those of upper/lower Pungchon formations. Thus, induced polarization is shown to be able to detect the high-grade limestone in upper Pungchon formation.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.387-393
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• 2015

Fault breccia, produced by fracturing and comminution of host rock during fault activity, is a common component within fault cores. Fault breccia may display a preferred orientationin accordance with the sense of motion on the fault. Here we use a numerical analysis technique to study the effects of the distribution and content of breccia in fault core on the elastic moduli. The analytical models are grouped into those in which breccias display a preferred orientation within fault core and those in which breccias are randomly oriented. The breccia compositions considered here are granite and shale, and the breccia contents are 10 wt%, 20 wt%, and 30 wt%. Our results show that for all the cases considered, differences in the deformation moduli fall within the range 0.1%~1.1% and differences in the elastic moduli fall within the range 0.02~0.4 MPa. Thus, the distribution and content of fault breccia have almost no effect on the elastic moduli.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.322-331
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• 2007

In this study, electrical resistivity tomography (ERT) were conducted to find the mineralized zone at the Geumpung mine in Dojeon-ri, Susan-myeon, Jecheon-si, Chungcheongbuk-do. The deviation of the inclined borehole was measured to obtain the exact positions of the electrodes for correcting apparent resistivity values from ERT. Geophysical loggings such as resistivity and natural gamma were conducted to obtain the properties of the material near the borehole. Measurements of the physical properties of the cores, such as porosity, water content, density, susceptibility, resistivity were performed to analyze the correlation between physical properties and resistivity. Grade analysis for core sample was also conducted to identify relationship between grade and resistivity. Rock property analysis shows that the resistivity is more dominated by susceptibility and grade than by porosity and water content in the mineralized zone. The results of ERT are well consistent with geophysical logging data and geologic column. So ERT is powerful method to identify conductive mineralized zone.

• Journal of the Korean earth science society
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• v.29 no.3
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• pp.221-245
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• 2008

The precambrian granitic gneiss and porphyroblastic gneiss are widely distributed in the Gwangyang-Hadong area of Korea. This study focuses on the geochemical properties and metamorphic P-T conditions of these gneisses. These gneisses are plotted according to granodiorite domain on an IUGS silica-alkali diagram. Geochemical properties of major elements suggest that these rocks are of the sub-alkalic rock series, and were farmed from S-type magmas which were generated in a syn-collision tectonic environment. The amounts of trace elements (Zn, Sc, Sr, V, etc.) decreased as $SiO_2$ concentrations increased. Almandine and spessartine mol%'s and XFe are higher in garnet rims, while pyrope mol%'s are higher in the garnet cores. This seems to be the result of garnet growth and retrogressive metamorphism. Metamorphic zones are divided into sillimanite-cordierite, sillimanite, garnet, and biotite zones. Metamorphic P-T conditions estimated from the gneisses indicate high temperature and low to medium pressure metamorphism (689-757$^{\circ}C$, 5.0-5.6 kbar), followed by medium temperature, low pressure retrorade metamorphism (579-628$^{\circ}C$, 3.1-4.5 kbar), and overprinted retrogade metamorphism (502-558$^{\circ}C$, 1.6-2.3 kbar).

• Journal of Conservation Science
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• v.37 no.2
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• pp.77-89
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• 2021

In this study, materials and color formation techniques were assessed for black potteries excavated from the Janghyeon-dong, Jungsan-dong and Gyodong-ri sites during the Proto-Three Kingdoms period in Ulsan, Korea. Although the black potteries were black superficially, the inner cores were either black or reddish yellow. Microscopy analysis identified that body clay was used for reddish iron oxide rich soils with quartz, alkali feldspar and mica, along with grains of myrmechite texture. Additionally, as marginal differences exist in the contents of SiO₂, Fe₂O₃ and CaO, the composition of the host rock and clay distributed around the sites was affected. Thus, we can deduce that pottery was made by soiling at a short distance. Raman spectroscopy results revealed that the black layer of the black pottery was used as amorphous combustion carbon. In addition, as a transparent layer of brown lacquer was observed on the substrate that was in contact with the surface layer, the black layer of the pottery induced black color development by a combination of combustion carbon and lacquer. Based on the mineral composition and microtexture of the body clay, the firing temperature of the potteries seemed to range from 750 to 850℃, whereas the lacquer layer was pyrolyzed at 468℃ by thermal analysis. Therefore, a combined layer of combustion carbon and lacquer, which formed the black color, was painted after the body clay was fired.

• The Journal of Engineering Geology
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• v.14 no.1
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• pp.29-46
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• 2004

It is important to identify geometries of fracture that act as a conduit of fluid flow for characterization of ground water flow in fractured rock. Fracture geometries control hydraulic conductivity and stream lines in a rock mass. However, we have difficulties to acquire whole geometric data of fractures in a field scale because of discontinuous distribution of outcrops and impossibility of continuous collecting of subsurface data. Therefore, it is needed to develop a method to describe whole feature of a target fracture geometry. This study suggests a new approach to develop a method to characterize on the whole feature of a target fracture geometry based on the Fourier transform. After sampling of specimens along a target fracture from borehole cores, effective frequencies among roughness components were selected by the Fourier transform on each specimen. Then, the selected effective frequencies were averaged on each frequency. Because the averaged spectrum includes all the frequency profiles of each specimen, it shows the representative components of the fracture roughness of the target fracture. The inverse Fourier transform is conducted to reconstruct an averaged whole roughness feature after low pass filtering. The reconstructed roughness feature also shows the representative roughness of the target subsurface fracture including the geometrical characteristics of each specimen. It also means that overall roughness feature by scaling up of a fracture. In order to identify the characteristics of permeability coefficients along the target fracture, fracture models were constructed based on the reconstructed roughness feature. The computation of permeability coefficient was performed by the homogenization analysis that can calculate accurate permeability coefficients with full consideration of fracture geometry. The results show a range between $10^{-4}{\;}and{\;}10^{-3}{\;}cm/sec$, indicating reasonable values of permeability coefficient along a large fracture. This approach will be effectively applied to the analysis of permeability characteristics along a large fracture as well as identification of the whole feature of a fracture in a field scale.

• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.194-201
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• 2021

Induced polarization (IP) effect is known to be caused by electrochemical phenomena at interface between minerals and pore water. Spectral induced polarization (SIP) method is an electrical survey to localize subsurface IP anomalies while injecting alternating currents of multiple frequencies into the ground. This method was effectively applied to mineral exploration of various ore deposits. Titanomagnetite ores were being produced by a mining company located in Gonamsan area, Gwanin-myeon, Pocheon-si, Gyeonggi-do, South Korea. Because the ores contain more than 0.4 w% vanadium, the ore deposit is called as Gwanin vanadiferous titanomagnetite (VTM) deposit. The vanadium is the most important of materials in production of vanadium redox flow batteries, which can be appropriately used for large-scale energy storage system. Systematic mineral exploration was conducted to identify presence of hidden VTM orebodies and estimate their potential resources. In geophysical exploration, laboratory geophysical measurement of rock samples is helpful to generate reliable property models from field survey data. Therefore, we performed laboratory SIP data of the rocks from the Gwanin VTM deposit to understand SIP characteristics between ores and host rocks and then demonstrate the applicability of this method for the mineral exploration. Both phase and resistivity spectra of the ores sampled from underground outcrop and drilling cores were different of those of the host rocks consisting of monzodiorite and quartz monzodiorite. Because the phase and resistivity at frequencies below 100 Hz are mainly dependent on the SIP characteristics of the rocks, we calculated mean values of the ores and the host rocks. The average phase values at 0.1 Hz were ores: -369 mrad and host rocks: -39 mrad. The average resistivity values at 0.1 Hz were ores: 16 Ωm and host rocks: 2,623 Ωm. Because the SIP characteristics of the ores were different of those of the host rocks, we considered that the SIP survey is effective for the mineral exploration in vanadiferous titanomagnetite deposits and the SIP characteristics are useful for interpreting field survey data.