• Economic and Environmental Geology
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• v.4 no.2
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• pp.77-90
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• 1971

About four hundred deposits of iron, talc, fluorite, tungsten, molybdenum, lead, zinc and other polymetallic mineral deposits were plotted on the Ore Distribution Map of the Ockcheon Geosynclinal Area. These mineral deposits plotted on the map can be divided into the several metallogenic zones by the consideration of their geologic background including the sedimentary and tectonic cycles and the igneous activities in the geosynclinal evolution, as follows: a. Chungju iron and talc zones. b. Cheong-san copper bearing iron sulphide zone c. Kumsan-Muju fluorite-polymetallic zones. d. Cheong-an Puyong and Ein Suckseong gold zone e. Hwang-gan Seolcheon and Sangju gold zones. Chungju iron zone originated in the iron bed in the Kemyongsan Series corresponding to the Pre-Ockcheon Cycle of evolution history. In early period of the Ockcheon Cycle, Hyangsanri quartzite and Munjuri phyllitic formation corresponding to the lower terrigenous sequence were not mineralized while the next sequence of the Samsungsan basic igneous-metamorphic formation and the Changri limestone formation were mineralized by the copper bearing iron sulphide and the fluorite-polymetallic deposits respectively. Two generations of the gold zones are recognized. The earlier generation distributes directionaly in the outside of the Ockcheon sedimentary belt was followed by the earlier grantitic invasion of Jurasic in age, while the later generation scatters at random which was related to the nondirectional Cretaceous granitic intrusion of the Post-Ockcheon Cycle. Conclusively speaking, it was disclosed that the endogenic mineralization in the Ockcheon geosyn clinal zone was not conspicuous in its inner sedimentary belt except its limestone area but in its outer peripheral granitic or gneissic zones, and the related igneous activities occured in the Post-Ockcheon Cycle of evolution history.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.63-70
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• 2016

The aim of this study is the safety and an accident prevention in limestone terrain by the underground tunneling. The geology of the study area consists of a Paleozoic sedimentary sequence dominated by limestone, sandstone, shale, and carbonaceous shale. The sequence gently dips to the northeast but the joint contains steep with variable trend. A significant fracture zone is developed in the limestone and shale beds, sub-parallel to bedding, and follows in part the limestone-sandstone contact. Monitoring of groundwater levels in the area shows marked fluctuations in the water table, which repeatedly rose to a level of -4 m before sinking to -15 m. These cycles occurred in mid-May, 2007 and in early and middle June. The data indicate that these fluctuations were unrelated to rainfall that occurred during the study period. We infer that the fluctuations were associated with the development of underground karstic networks along the deep fracture zone, and overlying ground subsidence is likely related to the rapid sinking of groundwater and the associated strong downward suction force.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.511-524
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• 2015

Groundwater causing subsidence in limestone mines is uncommon, and thus relatively poorly investigated. This case study investigated the cause and possibility of future subsidence through an evaluation of ground stability at the Samsung limestone mine, Chungcheongbuk-do. The ground near the mine area was evaluated as unstable due to rainfall permeation, and subsidence in the unmined area resulted from groundwater level drawdown. Future subsidence might occur through the diffusion of subsidence resulting from the small thickness of the mined rock roof, fracture rock joints, and poor ground conditions around the mine. In addition, the risk of additional subsidence by limestone sinkage in corrosion cavities, groundwater level drawdown due to artificial pumping, and rainfall permeation in the limestone zone necessitates reinforcements and other preventative measures.

• Journal of the Mineralogical Society of Korea
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• v.23 no.4
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• pp.413-428
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• 2010

The Gukjeon Pb-Zn mine was recognized as skarn deposits which replaced the limestone layer of the Jeongkansan Formation by intrusion of biotite granite in late Cretaceous. The Jeongkansan Formation is mainly composed of tuffaceous shale, and interlayers of sandstone, andesitic tuff, limestone, and conglomerate. The limestone layer is located in the lower part of the Jeongkansan Formation with 6~8 m in thickness and about 500 m in length. The Gukjeon deposits are divided into the Jukgang ore bodies once mined underground and the eastern ore bodies. Main ores are sphalerite and galena, in association with small amounts of chalcopyrite, arsenopyrite, pyrite, and pyrrhotite, etc. Skarns mainly consist of clinopyroxenes and Ca-garnets, associated with actinolite, chlorite, axinite, and calcite, etc. The Jukgang ore bodies show symmetrical distribution of zoning outward, representing clinopyroxene (hedenbergite) zone, clinopyroxene-garnet (grossular) zone, garnet (andradite) zone, and alteration zone of hornfels. $Fe^{2+}$ contents in clinopyroxenes increase with decreasing sphalerite grade. Sphalerite ores are found in all zones and $Fe^{2+}$ contents in sphalerite increase in the same way as those in clinopyroxenes, implying that clinopyroxene and sphalerite are closely related each other. It is concluded that the Gukjeon ores occurred in the ore rich zone of high grade sphalerite with less pyrite in assoication with clinopyroxene.

• Economic and Environmental Geology
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• v.16 no.1
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• pp.1-10
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• 1983

The Yeonhwa (I, II) and Keodo mines, neighboring in the middle part of the Taebaegsan mineral belt, contain three distinct classes of skarn deposits: the zinc-lead skarn at Yeonhwa (I, II), the iron skarn at Keodo south (Jangsan orebodies), and the copper skarn at Keodo north (78 orebodies). The present study characterizes the three classes of skarn deposits mainly in terms of skarn/ore associations examined from chemical compositional point of view, and applies existing quantitative phase diagrams to some pertinent mineral assemblages in these mines. At Yeonhwa I the Wolam I orebody shows a vertical variation in skarn minerals ranging from clinopyroxene/garnet zone on the lower levels through clinopyroxene (without garnet) zone on the intermediate levels, and finally to rhodochrosite veins on the upper levels and surface. Ore minerals, sphalerite and galena, associate most closely with the intermediate clinopyroxene zone. At Keodo, the Jangsan iron skarn hosted in quartz monzodiolite as a typical endoskarn, shows a skarn zoning, from center of orebody to outer side, magnetite zone, magnetite/garnet zone, garnet clinopyroxene zone, and clinopyroxene/epidote/plagioclase zone. The 78 copper skarn in the Hwajeol limestone indicates a zoning, from quartz porphyry side toward limestone side, orthoclase/epidote zone, epidote/clinopyroxene zone, and clinopyroxene/garnet zone; chalcopyrite and other copper sulfides tend to be in clinopyroxene/garnet zone. Mioroprobe analyses of clinopyroxenes and garnets from the various skarn zones mentioned above revealed that the Yeonhwa zinc/lead skarns are characterized by johansenitic clinopyroxene (Hd 25-78, Jo 15-23) and manganoan andraditic garnet (Ad 13-97, Sp 1-24), whereas the Jangsan iron skarn at Keodo by Mn-poor diopsidic clinopyroxene (Di 78-93, Jo 0.2-1.0) and Mn-poor grossularitic grandite (Gr 65-77, Sp 0.5-1.0). The 78 copper skarn at Keodo is characterized by Mn-poor diopsidic-salite (Di 66-91, Jo 0.2-1.1) and Mn-poor andraditic grandite(Ad 40-74, Sp 0.5-1.1). The compositional charateristics of iron, copper, and zinc-lead skarns in the Yeonhwa-Keodo mines are in good correlations with those of the foreign counterparts. Compiling a $T-XCO_2$ phase diagram for the Jangsan endoskarns, a potential upper limit of temperature of the main stage of skarn formation is estimated to be about $530^{\circ}C$, and a lower limit to be $400^{\circ}C$ or below assuming $XCO_2=0.05$ at P total=1kb. Applying a published log $fS_2$-log $fo_2$ diagram to the Keodo 78 and Yeonhwa exoskarns, it is revealed that copper sulfides and zinc-lead sulfides do not co-exist stably below log $fS_2=-4$ and log $fO_2=-23$ at $T=400^{\circ}C$ and ${\times}CO=1$ atm.

• Economic and Environmental Geology
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• v.2 no.1
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• pp.1-12
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• 1969

In the Sangdong Mine area, Taebaegsan series (Pre-Cambrian) and Chosun System (Cambro-ordovician) are widely distributed. The Chosun System consists of Yangdug Series (Jangsan Quartzite and Myobong Slate) and The Great Limestone Series (Pungchon Limestone, Shesong Shale, Hwajeol Formation and Dongjeom Quartzite). The mineralized zone containing the main ore body of the Sangdong Mine was developed in the Myobong Slate formation. The result of the field and microscopic study on the mineral paragenesis and it's wall rock alteration in the tungsten ore deposit shows the following features. The orogenic movements of the Post-Chosun System in the Hambaeg Geosyncline are closely related to the tungsten ore deposition in the area, the ore minerals are composed mainly of scheelite, powelite molybdenite and sulfide minerals, and gangue minerals are hornblende, diopside, garnet, quartz, phlogopite, tremolite, biotite, muscovite, fluorite, etc., main ore body was enriched by scheelite bearing quartz vein filling into interstices of formerly mineralized zones, and the minor faults, faults of N $60^{\circ}-70^{\circ}W$, $45^{\circ}-60^{\circ}NE$ and joints, which were formed at the end of the mineralization and the slate. Country rock of the ore body was altered into the following several zones from the outside to the inside; lowgrade recrystalline aureole, silicified sericite zone, and diopside-hornblende zone. Under the microscopic observation of 195 samples taken from throughout ore body can be classified into 10 different groups by their mineral paragenesis as shown in table 2. The garnet-diopside group is primary skarn and it shows gradational change to the groups of later stage by the successive processes of metasomatism. From the stage of quartz-bearing group, the dissemination of scheelite is seen. The crystallization of scheelite in the bed started with the quartz deposition and continued to the last stage when quartz vein intruded into the main ore body. In the field and the under ground investigation a durable limestone bed in thickeness about 20 meters and their remnants in ore body are observed and under microscope calcite remnants are recognized. Hence it is posturated that the ore material moved up through the faults, shear zones or feather cracks and was assimilated with the interbeded limestone, after that the body was affected by the successive differentiated ore solution by gradational increasing in $SiO_2$, $K_2O$ and $H_2O$. Evidently this ore deposit shows the features resulted from pyrometasomatic processes.

• Economic and Environmental Geology
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• v.29 no.1
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• pp.25-33
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• 1996

Stable isotopic ratios of the carbonate rocks and chemical compositions of the matrix of pebble bearing phyllitic rocks known as the Hwanggangri Formation, which are in hot debate on their origin such as tillite, debris flow and turbidite, were determined to interpret their depositional environment. Argillaceous matrix of the pebble bearing phyllitic rocks has a high content of CaO (av. 19.5%) and MgO (av. 8.3%), corresponding to calcareous sandy shale. No difference of chemical compositions including trace elements and REE is in the matrices between the Hwanggangri and the Kunjasan Formations. Carbonate rocks from the Okchon zone and outside of the zone range $-2.5{\sim}+6.1$‰ in ${\delta}^{13}C$ and $+5.8{\sim}+25.9$‰ in ${\delta}^{18}O$, indicating normal marine limestone. However, unusally $^{13}C$ enriched carbonate rocks might be deposited in the highly evaporated sedimentary basin. A wide variation of ${\delta}^{18}O$ values is responsible for metamorphism with a $^{18}O$ depleted meteoric water. Isotopic equilibrium temperatures by graphite-calcite geothermometer show a higher metamorphic temperature ($547{\sim}589^{\circ}C$) in the Okchon zone than those ($265{\sim}292^{\circ}C$) in the Samtaesan Formation of the Chosun group. Rhythmic alternation of relatively thin shale with thin limestone in the Kounri Formation is not cherty layer but thin limesilicate bed by metasomatic replacement. Judging from the isotopic and chemical compositions of the carbonate rocks and calcareous matrix of the pebble bearing phyllitic rocks, the Hwangganari Formation was deposited in the shallow marine environment favorable to debris flow.

• Economic and Environmental Geology
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• v.18 no.4
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• pp.381-397
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• 1985

A petrological study has been done in the pyeongchang-Jaecheon area which is a northwestern part of the basement of Ogcheon zone for the purpose of comparison of the area to the Nogjeon-Yeongchun area which is the antipodal basement of the zone in the petrological and geotectonical view points. The major units of the area are Precambrian granitic gneissic complex, banded gneiss, linea ted leucocratic gneiss and pegmatitic leucogranitic gneiss in the west, elongated exposure of quartz schist (or partly quartzite) and phyllite, named as Jungdaegal-bong Group correlated to the lower sequence of Joseon Group, in the middle, and limestone and calcic dolomite, Iptanri Formation, correlated to the middle of Joseon Group in the east. Igneous plutons are distributed in the areas of gneissic complex and limestone formation as well as in the Eosangcheon and Daedaeri areas in the southeastern out of the area. Present study reveals that the gneissic complex are the products of granitization to metamorphism of amphibolite facies in the order of above mentioned from the metasediments of schists and calcareous rocks. A notable characteristics of the phyllite of Jungdaegal-bong Group is the presence of syntectonically segregated quartz rods in the forms of lens, swirl or boudinage in evenly distributed in the phyllitic to chloritic matrix. Igneous rocks range in composition from gabbro through diorite, granodiorite, to schistosed and porphyritic granites in stock and dike. The orogenic movement of the Ogcheon zone initiated in the middle Proterozoic time, pre-sedimentation of Ogcheon Group and superposed the granitization in Permian, Jurassic Daebo orogeny with granitic batholiths and stocks, and Cretaceous plutonic intrusion.

• Economic and Environmental Geology
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• v.7 no.2
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• pp.45-62
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• 1974

Scheelite deposits in Sangdong mine are divided into three parallel vein groups, namely "Hanging-wall vein" which is located in the lowest parts of Pungchon Limestone, "Main vein" the most productive vein replaced a intercalated limestone bed in Myobong slate, "Foot-wall veins" a group of several thin veins parallel to main vein in Myobong slate. Besides the above, there are many productive quartz veins imbedded in the above veins and Myobong slate. Molybdenite and wolframite are barren in the former three veins group but associates only in quartz veins. Both main vein and foot-wall veins show regular zonal distribution, quartz rich zone in the center, hornblende rich zone surrounding the quartz rich zone and diopside rich zone in the further outside to the marginal parts of the vein. According to the distribution of three main minerals, quartz, hornblende and diopside the main vein can be divided into three zones which are in turn grouped into 7 subzones by distinct mineral paragenesis. They are summerized as follows: A. Diopside rich zone: 1. garnet-diopside.fl.uorite subzone 2. diopside-zoisite-quartz subzone 3. diopside-plagioclase subzone B. Hornblende rich zone: 4. hornblende-diopside-quartz subzone 5. hornblende-quartz-chlorite subzone 6. hornblende-plagioclase-quartz.sphene subzone C. Quartz rich zone: 7. quartz-mica-chlorite subzone The foot-wall veins can similarly be divided by mineral paragenesis into 3 zones, 6 subzones as follows: A. diopside rich zone: 1. garnet-diopside-quartz.fl.uorite subzone 2. garnet-diopside-wollastonite subzone B. Hornblende rich zone: 3. quartz-hornblende-chlorite subzone 4. hornblende-plagioclase-quartz subzone 5. hornblende-diopside-quartz subzone C. Quartz rich zone: 6. quartz-mica subzone The hanging-wall vein is generally grouped into 9 subzones by the mineral paragenesis which show random distribution. They are as follows: 1. diopside-garnet-fluorite subzone 2. diopside-zoisite-quartz subzone 3. diopside-hornblende-quartz-fluorite subzone 4. wollastonite-garnet-diopside subzone 5. hornblende-chlorite-quartz subzone 6. quartz-plagioclase-hornblende-sphene subzone 7. quartz-biotite subzone 8. quartz-calcite subzone 9. calcite-altered minerals subzone Among many composing minerals, garnet specially shows characteristic distribution and optical properties. Anisotropic and euhedral grossularite is generally distributed in the hanging wall vein and lower parts of the main vein, whereas isotropic and anhedral andradite in the upper parts of the main vein. Plagioclase (anorthite) and sphene are distributed ony near the foot-wall side of the aboveveins. wollastonite is a characteristic mineral in upper parts of the hang-wall vein. Molybdenite is distributed in the upper parts of quartz veins and wolframite in lower parts of quartz veins.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.63-70
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• 2002

In tunnel construction, the information on the rock quality and the location of fault or fracture are crucial for economical design of support pattern and for safe construction of the tunnel. The grade of rock is commonly estimated through the observation with the naked eye of recovered cores in drilling or from physical parameters obtained by their laboratory test. Since drilling cost is quite expensive and terrains of planned sites for tunnel construction are rough in many cases, however, only limited information could be provided by core drilling Electrical resistivity and EM surveys may be a clue to get over this difficulty. Thus we have investigated electrical resistivity and EM field data providing regional Information of the rock Quality and delineating fault and fracture over a rough terrain. In this paper, we present some case histories using electrical resistivity and EM survey for the site investigation of tunnel construction. Through electrical resistivity and EM survey, the range and depth of coal seam was clearly estimated, cavities were detected in limestone area, and weak zones such as joint, fault and fracture have been delineated.