• Economic and Environmental Geology
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• v.15 no.4
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• pp.189-204
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• 1982

The Geodo mine is located in the southern limb of the Hambaeg syncline. Geology of the area consists of Paleozoic-Mesozoic sedimentary Rocks and Cretaceous igneous rocks. The important igneous rocks presumably related to skarnization and ore mineralization in the area, are the early granodiorite and the late porphyritic granodiorite. Two mineralogical types of ore deposits are recognized in the area. They are the Fe-Cu deposits in the Myobong formation and the Au-Bi-Cu deposits in the Hwajeol formation. Contact metamorphism due to granodiorite intrusion includes hornfelsization, exoskarnization and endoskarnization. Wall-rock alterations related to the Fe mineralization are grouped into the hydrothermal replacement skarnization and the hydrothermal filling skarnization. Another hydrothermal alteration is associated with the Cu mineralization. Various mineralogical analyses have been applied for the identification of minerals. They include optical microscopy, chemical analysis, etching test, X-ray diffraction, and infrared absorption spectroscopic analyses. The ore minerals in these ore deposits are classified into two groups;hypogene and supergene minerals. Hypogene minerals consist of magnetite, pyrite, chalcopyrite, and chalcocite. Supergene minerals consist of chalcocite, bornite, and geothite. Ore minerals show various kinds of ore texture: open-space filling, exsolution, replacement, and cementation texture. The gangue minerals consist of quartz, diopside, epidote, garnet and plagioclase in the hornfelsic zone, garnet, diopside, scapolite, actinolite, sericite, chlorite, quartz, and calcite in the skarn zone, and, epidote, chlorite, sericite, quartz, and calcite in the late hydrothermal alteration zone. This study shows that the Fe-Cu deposits are of metasomatic pipe type with the later hydrothermal fillings, and the Au-Bi-Cu deposits are of hydrothermal fissure-filling type. The mineralization is probably related to the intrusion of porphyritic granite.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.214-233
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• 2002

Igneous rocks of Mt. Mudeung area are composed of Pre-Cambrian granite gneiss, Triassic hornblende-biotite granodiorite, Jurassic quartz diorite and Cretaceous igneous rocks. The Cretaceous igneous rocks consist of volcanic rocks (Hwasun andesite, Mudeung-san dacite and Dogok rhyolite) and granitic rocks (micrograpic granite and quartz porphyry). Major elements of the Cretaceous igneous rocks represent calc-alkaline rock series and correspond to a series of differentiated products from cogenetic magma. Igneous activity of Mt. Mudeung area started from volcanic activity, and continued to intrusive activity at end of the Cretaceous. In chondrite normalized REE pattern, most of igneous rocks of Mt. Mudeung area show similar pattern of Eu (-) anomaly. This is a characteristic feature of granite in continental margin by tectonic movement. Variation diagrams of total REE vs. La/Yb V vs. SiO$_2$ indicate differentiation and magnetite fractionation sequential trend of Hwasun andesite longrightarrowMudeungsan dacitelongrightarrowquartz porphyry. In mineral composition of these igneous rocks in mt. Mudeung area, composition of plagioclase and biotite coincidence with variation of whole rock composition, and emplacement and consolidation of magma is about 15 km (about 4.9 Kbar) in Jurassic quartz diorite and 2.0~3.2 km (0.6~1.0 Kbar) in Triassic hornblende-biotite granodiorite used by amphibolite geobarometer. Parental magma type of these granitic rocks of nt. Mudeung area corresponds to VAG field in Pearce diagram, and I-type in ACF diagram.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.2
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• pp.95-106
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• 2023

Quartz (SiO₂) is among the major rock-forming minerals in the earth's crust. The atomistic structures of SiO₂ may evolve during diverse frictional processes. The reduction of friction of quartz-rock accompanied by its amorphization, hydration, and formation of silica gel provides mineralogical insights into earthquakes and related phenomena. Ball milling, together with rotary shear experiments have been useful to infer the atomic origins of such processes. In this study, optimal experimental conditions for ball milling for amorphization of SiO₂ were determined by taking into account various process variables. The crystallinity of SiO₂ gradually decreased and became amorphous as the ball milling time increased at a high milling speed. The degree of wear of the milling media and its effect on the amorphization of SiO₂ were analyzed using distinct milling materials (zirconia, stainless steel). The amount of ball wear increased with increasing milling time. Furthermore, the worn stainless steel particles from balls tend to interact with amorphized SiO₂ to form Si-O-Cr. These results aid in understanding the process of atomistic structural changes caused by ball milling of divserse materials with relatively high hardness, such as SiO₂, and understanding various geological friction processes.

• Geotechnical Engineering
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• v.12 no.2
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• pp.33-42
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• 1996

The weathering of mudrock in the Pohang area is mainly caused by slaking and swelling when the mudrock is absorbed with water. In this regard, this paper chows the results of chemical analysis and the identification of rock-forming minerals from XRD. It also compares the slaking and swelling characteristics of mudrocks sampled from 3 different sites. The chief rock -forming minerals are the quartz, and the several types of clay minerals. The slake durability indices are ranged from 71% to 96%, and these values are closely related to the liquid limit of the powdered nock specimen. In a similar manner to the slaking characteristics the greatest values of the swelling pressure and the swelling strain were measured from the mudrock specimen with the highest value of liquid limit. The greatest measured values of the swelling pressure and the swelling strain are 9.4 kg 1 cm2 and 33.5% respectively. The residual sheer strength of mudrock decreases as the number of wet -diy cycles increases, and the residual strength at 5 cycles are measured to c,=0.24kg/cm2 and p,=28$^{\circ}$. The lowest residual strength is measured at the fresh rock -rock contact surface in the moist condition of which values are cr: 0 and n,: 21.5$^{\circ}$.

• Journal of Conservation Science
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• v.5 no.1 s.5
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• pp.41-68
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• 1996

Stone-cultural-properties, distributed In the area, have been investigated and studied on the characteristics and the rock phases in the geological and conservational point of view. Stone-Buddhas in the area can be subdivided into Maebul-, General -, and Massive rock-types according to their styles. The rocks used in these stone-cultural-properties are mainly massive, coarse grained biotite granite of the Jurassic age, which is widely distributed around the Reckon-gun area. However, quartz-feldspathic banded gneiss, marble, phyllite and hornblendite are also used. These rocks are mainly distributed in the Yongin-gun area. This suggests that the rocks used. These rocks are strongly influenced by chemical weathering so that the rock surface is very irregular with $2\~3mm$ relief. Biotite granite used shows generally weathered surface of brown color due to chemical weathering of feldspars. Moss are pervasive partly on the surface to show black and/or green colors. The strong weathering may induce secondarily to appear the igneous lineation, onion-structure, and/or minor cracks latent in the rocks. The cultural properties In the area are relatively well conserved except Maebuls and one(Duchangri 3-story) pagoda. However, one stone-buddha may be grinded recently by machine to take off the weathered surface resulting in the loss of its age and the original detailed shape. For conservation, they must be scientifically considered on the shape, kind of the rock phase and characteristics of the weathered phenomena.

• Economic and Environmental Geology
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• v.43 no.5
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• pp.443-453
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• 2010

The Samsung gold-silver deposit consists of quartz veins that fill along the fault zone within Cretaceous shale and sandstone. Mineralization is occurred within fault-breccia zones and can be divided into two stages. Stage I is main ore mineralization and stage II is barren. Stage I is associated with wall-rock alteration minerals(sericite, pyrite, chlorite, quartz), rutile, base-metal sulfides(pyrrhotite, pyrite, sphalerite, chalcopyrite, galena), and electrum. Stage II occur quartz, calcite and pyrite. Fluid inclusion data indicate that homogenization temperatures and salinities of stage I range from 145 to $309^{\circ}C$ and from 0.4 to 12.4 wt.% NaCl, respectively. It suggests that hydrothermal fluids were cooled and diluted with the mixing of meteoric water. The main deposition of base-metal sulfides and electrum occurred as a result of cooling and dilution at temperature between $200^{\circ}C$ and $300^{\circ}C$. Sulfur(9.3~10.8‰) isotope composition indicates that ore sulfur was mainly derived from a magmatic source as well as the host rocks. The calculated oxygen[-2.3~0.9‰(quartz: 0.3‰, 0.9‰, calcite: -2.3‰)] and hydrogen[-86~-76‰(quartz: -86‰, -82‰, calcite: -76‰)] isotope compositions indicate that hydrothermal fluids may be meteoric origin with some degree of mixing of another meteoric water for paragenetic time.

• Economic and Environmental Geology
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• v.44 no.2
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• pp.171-180
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• 2011

For 21 rock samples consisting of granite, sandstone and the effective thermal conductivity (TC) was measured with the LFA-447 Nanoflash, and mineralogical compositions were also determined from XRD analysis. The structural models were used to examine the effects of quartz content and the size of minerals on TC of rocks. The experimental results showed that TC of rocks was strongly related to quartz content with $R^2$ value of 0.75. Therefore, the proposed regression model can be a useful tool for an approximate estimation of TC only from quartz content. Some samples with similar values of quartz content, however, illustrated great differences in TC, presumably caused by differences in the size of minerals. An analysis from structural models showed that TC of rocks with fine-grained minerals was likely to fall in the region between Series and EMT model, and it moved up to ME and Parallel model as the size of minerals increased. This progressive change of structural models implies that change of TC depending on the size of minerals is possibly related to the scale of experiments; TC was measured from a disk sample with a thickness of 3 mm. Therefore, in case of measurements with a thin sample, TC can be overestimated as compared to the real value in the field scale. The experimental data illustrated that the scale effect was more pronounced for rocks with bigger size of minerals. Thus, it is worthwhile to remember that using a measured TC as a representative value for the real field can be misleading when applied to many geothermal problems.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.163-176
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• 2009

The pyrophyllite deposits located in Jinhae area have been studied through field observations and laboratory works including the X-ray diffraction (XRD), X-ray fluorescence (XRF), Electron probe microanalyzer (EPMA) and Inductively Coupled Plasma (ICP). The pyrophyllite deposits consist of mainly illite, dickite, pyrophyllite, diaspore, chlorite, pyrite and copiapite. According to the mineral assemblages, geological occurrences and alteration modes, the altered rocks can be classified into four types: Type A; quartz with silicifictaion, Type B; quartz + illite with illitization, Type C; quartz + dickite + illite with kaolin alteration, Type D; pyrophyllite + illite + dickite + diaspore with pyrophyllite alteraion. Rocks in Type A, which is generated by silicifictaion, have high $SiO_2$ contents more than 90 wt% and distinctive equigranular textures with microcrtstalline quartz. The pyrophyllites from the study area belong to 2M polytype. The host rocks of the pyrophyllite ore in this mine are rhyolitic rock, andecitic tuff and volcanic breccia. The alteration products seem to be controlled by the different lithology of the host rocks. The hydrothermal solution formed the deposits would be inferred to the acidic and have relatively high ionic activity of hydrogen and silica judging from alteration mineral assemblage. Pyrophyllite alteraion zone is generated by highest temperature condition of all alteration zone.

• Journal of Conservation Science
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• v.25 no.4
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• pp.347-361
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• 2009

The Pohang Chilpori is the area with abundant petroglyphs in Korea. The form of the shield, female sex organs, and yut board on the outcrops or float rocks which are composed of the rhyolitic rock are engraved on Chilpori and Shinheungri Petroglyphs. The rhyolitic rock is composed of the phenocryst and groundmass with quartz and feldspar. The rock surface shows mostly yellowish brown color and the rock surface is very irregular by serious weathering, and illite and kaolinite, a kind of the clay minerals, are produced. Deterioration aspects are mainly of surface exfoliation, grain peel-off, damages, scribbling. Chilpori Petroglyph (1) plane has been eroded by running water, in (2) plane has been abrased is on the rock surface, in (3) plane shows surface exfoliation and the various part of the rock surface in plane (4) has become the soil. The corrasion and black phenomenon of the Shinheungri Petroglyph (1) plane was formed by running water, and surface exfoliation and scribbling in plane (2) is serious. Deterioration factors are geomorphologic states, plants, rock of weak to weathering, and artificial influence such as a scribbling and a forest fire. For conservation of the these petroglyphs, study for rock surface conservation and the arrangement of around petroglyphs and construction of water wall are necessary.

• Economic and Environmental Geology
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• v.28 no.1
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• pp.25-31
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• 1995

In Dongnam area, Cretaceous igneous rocks, such as diorite, porphyritic granite, and quartz porphyry intruded Paleozoic sedimentary rocks, such as Myobong slate and Pungchon limestone. The Dongnam Fe-Mo skarn deposits were imposed on the diorite(endoskarn) and the Myobong slate(exoskarn). The ore deposits consist mainly of magnetite and molybdenite with small amounts of sulfides, such as galena, sphalerite, pyrite, chalcopyrite, and pyrrhotite. The igneous rocks show nearly constant $^{206}Pb/^{204}Pb(18.80{\sim}19.06)$ and $^{207}Pb/^{204}Pb(15.71{\sim}15.72)$ ratios. Their $^{207}Pb/^{204}Pb$ ratios higher than the typical ratios of orogene suggest that the igeneous rocks were formed from lower crust(or mantle) - derived magma excessively contaminated by upper crustal materials such as high radiogenic Precambrian basement rocks. The lead isotopic compositions of the igneous rocks, the Pungchon limestone, and the ore minerals show a well defined linear in $^{206}Pb/^{204}Pb$ - $^{207}Pb/^{204}Pb$ plot. The lead isotopic compositions of the igneous rocks are similar to those of magnetite and galena, which were formed at early skarn stage and significantly lower than those of altered quartz porphyry, molybdenites, and pyrite, which were formed at late epithermal alteration stage. Considering the systematic variation of the lead isotopic compositions in the ore minerals according to hydrothermal stages, the variation may be due to a relative variation in surrounding rock(Pungchon limestone) involvement in hydrothermal ore solution leaching the surrounding rock. Therefore, the variation of the lead isotopic compositions in ore minerals can be modeled in terms of the mixing of the leads derived from the igneous rocks as low radiogenic source and the surrounding rock(Pungchon limestone) as high radiogenic source.