• Economic and Environmental Geology
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• v.21 no.3
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• pp.235-255
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• 1988

Talc deposit of pipe-like form occurrs in the lower part of the Hyangsanri Dolomite with a strike of N40 -50 E and a dip of 40 -50 NW which is one formation of the Ogcheon Super Croup. The pipi-like ore body plunge at about $40^{\circ}$ to the west and are parallel to the lineation developed in the area. Structural formulae of tales occurred in this deposit are close to the ieal composition $Mg_6Si_8O_{20}(OH)_4$ showing limited deviation from ideal one. Substitution of Al for Si in tetrahedral site is of little or nothing ranging 0-0.04 and octahedral occupancy is close to six ranging 5.88-5.98 atoms per unit cell. Predominant octahedaral cation is Mg and proportion of divalent cations is generally over 97percent. Calcite -dolomite thermometry is obtained by determining the mol % $MgCO_3$using of EPMA and XRD methods. The peak metamorphic temperature can be estimated at $470{\pm}30^{\circ}C$ in the area whereas carbonates occurred at near talc ore show lower temperature than $400^{\circ}C$ that the calcite solvus limit is not well established. It indicates that the talc deposit was formed at the lower temperature that the metamorphic temperature. Cosequently, the formation of talc by metamorphism is questionable and the alteratin zone developed around the talc ore is very limited. The occurrence of talc ore in the dolomite as well as mineralogy, calcite-dolomite geothermometry, chlorite geothermometry, field and microscopic evidence suggest that siliceous ascending hydrothermal solution along the fracture is responsible for the formation of talc. It was considered that the slight fracturing of dolomite was formed by deformation prior to the mineralization.

• Economic and Environmental Geology
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• v.30 no.1
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• pp.15-23
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• 1997

Gold mineralization of the Ogkye gold mine was deposited mainly in quartz veins up to 150 cm wide which occupy fissures in Cambrian Pungchon limestone. Ore minerals are relatively simple as follows: pyrite, arsenopyrite, pyrrhotite, sphalerite, electrum and galena. On the basis of the Ag/Au ratio on ore grades, mode of occurrence and assoicated mineral assemblages, the Ogkye gold deposit can be classified as pyrite-type gold deposit (Group IIB). Fluid inclusion data indicate that ore minerals were deposited between $400^{\circ}$and $230^{\circ}C$ from relatively dilute fluids (0.2 to 7.3 wt.% eq. NaCl) containing $CO_2$. The ore mineralization resulted from a complex history of $CO_2$ effervescence and local concomitant boiling coupled with cooling and dilution of ore fluids. Gold deposition was likely a result of decrease of sulfur activity caused by sulfide deposition and/or $H_2S$ loss accompanying fluid unmixing. Sulfur isotope compositions of sulfide minerals (${\delta}^{34}S=3.5{\sim}5.9$‰) are consistent with ${\delta}^{34}S_{H_2S}$ value of 4.8 to 6.1‰, suggesting mainly an igneous source of sulfur partially mixed with wall-rock sulfur.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.1
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• pp.41-54
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• 2023

Illite is a common mineral that forms readily from feldspar and mica via hydrothermal alteration and exhibits various characteristics depending on the degree of hydrothermal alteration. To ensure continued mining of high-quality illite ore, it is crucial to understand the illitization. Thus, this study collected ores from two illite ore deposit and their surrounding alteration zones in Yeongdong-gun, Chungcheongbuk-do, a significant source of illite in the Republic of Korea, to determine the constituent mineral contents and textural characteristics. Polarized light microscopy analyses revealed that the illite ore deposit were highly illitized with little remaining textural characteristics of the parent mica schist, and only some quartz was present. The ore zone contained illite, muscovite, quartz, and feldspar, with illitization primarily occurring around feldspar and quartz. X-ray diffraction analyses identified that the content of illite/muscovite was approximately 50-75 wt.%, with a maximum of 75 wt.%. Additionally, X-ray fluorescence analyses indicated a linear increase in K₂O content with increasing illite content, showing the highest correlation among the major components analyzed. It is suggested that the illite in the Yeongdong area results from feldspar and quartz alteration by hydrothermal fluids along the fault, with illitization of feldspar occurring before that of quartz. The results of this study are expected to contribute to the development of high-quality illite ore deposit in Yeongdong, Chungcheongbuk-do.

• Economic and Environmental Geology
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• v.23 no.2
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• pp.127-133
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• 1990

Relation between fluid inclusions and mineralization has been studied for 30 granitoid specimens from 19 localities in South Korea. Polyphase inclusions are found in granitoid specimens of 9 localities. In the vicinities of 6 localities among them occurs any of W, Cu or Fe deposits of the vein-, stockwork-, skarn-or pegmatite-type. On the contrary, no ore deposit is reported near the granitoids characterized by no polyphase inclusion except only one locality. This fact implies that the occurrence of polyphase inclusions is a good indicator for such kinds of mineralization. Ores and country rocks of some of the deposits contain polyphase inclusions in their quartz crystals. The fact that many polyphase inclusions occur in granitoids and ore constituents suggests that highly saline hydrothermal solution played an important role for the formation of such kinds of deposits. On the contrary, the granite and the ore of the Mugug gold deposit have many fluid inclusions, but are free from the polyphase type.

• 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.

• Geophysics and Geophysical Exploration
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• v.12 no.3
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• pp.268-277
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• 2009

Recently as the interest in the development of domestic ore deposits has increased, we can easily find some studies on exploration geophysics-based ore deposit survey in literature. Geophysical surveys have been applied to the investigation of both metallic and non-metallic ore deposit. For metallic ore-deposit survey, the 2D electrical resistivity method has been popularly used, because metallic mineral deposits are generally more conductive than surrounding media. However, geological structures are 3D rather than 2D structures, which may lead to misinterpretation in 2D inversion section. In this study, 3D effects are examined for several 3D structures such as a width-varying dyke model and a wedge-shaped model. We also investigate the effects of the direction of survey line. Numerical results show that the width-varying dyke model yields some low resistivity zone in the deep part, which is independent of real ore-body location. For the wedge-shaped model, even though the survey line is located apart from the ore body, the 2D inversion section still shows low resistivity zone in the deep part. When the survey line is not perpendicular to the strike of the ore body, the low resistivity zone is slightly broader but shallower than that obtained along the survey line perpendicular to the strike. For the survey lines that have an angle smaller than $45^{\circ}$ with the strike of the ore body, the inversion results are totally distorted. From these results, we conclude that 2-D survey and interpretation can lead to misinterpretation of subsurface structures, which may be linked to economical loss. Eventually, we recommend to apply 3-D rather than 2-D electrical resistivity survey for ore-deposit survey.

• Economic and Environmental Geology
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• v.7 no.4
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• pp.157-173
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• 1974

The Red Hill deposit of the Dongjom Copper Mine is the most promising deposit of the mine and under intensive exploration at present although there are eight more deposits of vein type. With total 2160m drilling of 9 holes completed and 400m drilling on two holes underway, the nature of the Red Hill deposit has come more clear. The copper content in the whole ore body is meager so far as the exploration done up to present indicates, but there are evidences that mineralization covers all over the granodiorite cupola at the Red Hill area. The petrological work and assay on the samples taken by the writers indicate that granodiorite rocks can be divided into fresh zone and alteration zone. Alteration zone consists of potassic and argillic zones accompanyied by silicification zone on basis of Lowell and Guilbert model Argillic zone has closely related with a mineralization in the Red Hill deposit. It has been cleared that the alteration acompanyied with the mineralization took place not only &long vertical fissures but also in the irregular lateral zone, the nature of which is unknown. Judging from the results of exploration and petrochemical study on the Red Hill deposit which is imbedded in a southern part of the granodiorite cupola, it can be concluded by the writer's opinion that the Red Hill deposit is possibly a porphyry copper deposit, because the shape of the ore body, mineral zoning and paragenesis and wall rock alteration resemble to those of typical porphyry copper deposits. It is the writers' opinion that more exploration work is required so as to evaluate the deposit.

• Economic and Environmental Geology
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• v.50 no.5
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• pp.325-340
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• 2017

The Seongdo Pb-Zn deposit, located in the northwestern part of the Ogcheon Metamorphic Belt, consists of skarn ore replacing limestone within the Hwajeonri Formation of Ogcheon Group and hydrothermal vein ore filling the fracture of host rock. Skarn minerals comprise mostly hedenbergitic pyroxene, garnet displaying oscillatory zonal texture composed of grossular and andradite, and a small amount of wollastonite, tremolite, and epidote, indicating reducing condition of formation. Ore minerals of skarn ore include sphalerite and galena with a small amount of pyrite, pyrrhotite, and chalcopyrite. In hydrothermal vein ore, arsenopyrite, sphalerite, chalcopyrite, and pyrite occur with a small amount of galena, native Bi, and stannite. Chemical compositions of sphalerite vary from 17.4 mole% FeS in average for dark grey sphalerite, 3.6 mole% for reddish brown sphalerite in skarn ore, and to 10.3 mole% FeS in hydrothermal vein ore. In comparison with representative metallic deposits in South Korea on the FeS-MnS-CdS diagram, skarn and hydrothermal vein ore plot close to the field of Pb-Zn deposits and Au-Ag deposits, respectively. Arsenic contents of arsenopyrite in hydrothermal vein ore decrease from 31.93~33.00 at.% in early stage to 29.58~30.21 at.% in middle stage, and their corresponding mineralizing temperature and sulfur fugacity are $441{\sim}490^{\circ}C$, $10^{-6}{\sim}10^{-4.5}atm$. and $330{\sim}364^{\circ}C$, <$10^{-8}atm$. respectively. Phase equilibrium temperatures calculated from Fe and Zn contents for coexisting sphalerite and stannite in hydrothermal vein are $236{\sim}254^{\circ}C$. Sulfur isotope compositions are 5.4~7.2‰ for skarn ore and 5.4~8.4‰ for hydrothermal vein ore, being similar or slightly higher to magmatic sulfur, suggesting that ore sulfur was mostly of magmatic origin with partial derivation from host rocks. However, much higher sulfur isotope equilibrium temperatures of $549^{\circ}C$와 $487^{\circ}C$, respectively for skarn ore and hydrothermal ore, than those estimated from phase equilibria imply that isotopic equilibrium has not been fully established.

• Economic and Environmental Geology
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• v.55 no.2
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• pp.171-181
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• 2022

The Geochang Au-Ag deposit is located within the Yeongnam Massif. Within the area a number of hydrothermal quartz and calcite veins were formed by narrow open-space filling of parallel and subparallel fractures in the granitic gneiss and/or gneissic granite. Mineral paragenesis can be divided into two stages (stage I, ore-bearing quartz vein; stage II, barren calcite vein) by major tectonic fracturing. Stage I, at which the precipitation of major ore minerals occurred, is further divided into three substages (early, middle and late) with paragenetic time based on minor fractures and discernible mineral assemblages: early, marked by deposition of pyrite with minor pyrrhotite and arsenopyrite; middle, characterized by introduction of electrum and base-metal sulfides with minor sulfosalts; late, marked by hematite with base-metal sulfides. Fluid inclusion data show that stage I ore mineralization was deposited between initial high temperatures (≥380℃ ) and later lower temperatures (≤210℃ ) from H₂O-CO₂-NaCl fluids with salinities between 7.0 to 0.7 equiv. wt. % NaCl of Geochang hydrothermal system. The relationship between salinity and homogenization temperature indicates a complex history of boiling, fluid unmixing (CO₂ effervescence), cooling and dilution via influx of cooler, more dilute meteoric waters over the temperature range ≥380℃ to ≤210℃. Changes in stage I vein mineralogy reflect decreasing temperature and fugacity of sulfur by evolution of the Geochang hydrothermal system with increasing paragenetic time. The Geochang deposit may represents a mesothermal gold-silver deposit.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.753-765
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• 2021

The Dongwon Au-Ag deposit is located within the Paleozoic Taebaeksan province, Okcheon belt. Mineral paragenesis can be divided into two stages (stage I, ore-bearing quartz veins; stage II, barren carbonate veins) by major tectonic fracturing. Stage I, at which the precipitation of major ore minerals occurred, is further divided into three substages(early, middle and late) with paragenetic time based on minor fractures and discernible mineral assemblages: early, marked by deposition of pyrite with minor magnetite, pyrrhotite and arsenopyrite; middle, characterized by introduction of electrum and base-metal sulfides with minor sulfosalts; late, marked by argentite, Cu-As (and/or Sb) and Ag-Sb sulfosalts with base-metal sulfides. Fluid inclusion data show that stage I ore mineralization was deposited between initial high temperatures (≥430℃) and later lower temperatures (≤230℃) from fluids with salinities between 6.0 to 0.4 wt. percent equiv. NaCl. The relationship of salinity and homogenization temperature suggest that ore mineralization at Dongwon was deposited mainly due to fluid boiling, cooling and dilution via influx of cooler, more dilute meteoric waters. Changes in stage I vein mineralogy reflect decreasing temperature and fugacity of sulfur by evolution of the Dongwon hydrothermal system with increasing paragenetic time. The Dongwon deposit may represents a Korean-type and/or Au-Ag type mesothermal/epithermal gold-silver deposit.