• Journal of the Mineralogical Society of Korea
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• v.20 no.1 s.51
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• pp.35-46
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• 2007

Shinyemi skarn deposits occur as Fe-Mo skarn type and Pb-Zn-Cu hydrothermal replacement type along the contact between Cretaceous Shinyemi granitoids and Cambro-Ordovician mixed limestone and dolostone sequence of the Choseon Supergroup. In the lower part of Western Shinyemi ore body two stages of skarn formation have been observed: the early, stage I (magnesian) skarn with Fe mineralization and the late, stage II(calcic) skarn with Mo mineralization. The stage I skarn spatially is overprinted by stage II skarn. The stage I skarn is predominantly composed of olivine, magnetite and diopside whereas, the stage II skarn is dominated by hedenbergite and garnet. The skarnification process occurred in two stages, both prograde and retrograde for stage I and stage II skarns. In stage I, the prograde skarns, mainly composed of anhydrous silicate minerals, were formed at relatively higher temperatures (about $400\;to\;550^{\circ}C$) under low $CO_{2}$ fugacity ($X_{CO2}<0.1$) conditions. On the other hand, the retrograde skarns that consisted of hydrous minerals were formed at lower temperatures (about $300\;to\;400^{\circ}C$).

• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.158-160
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• 2007

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• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.250-251
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• 2001

• Journal of the Mineralogical Society of Korea
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• v.21 no.1
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• pp.1-15
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• 2008

The Cretaceous Gajok gold-silver deposit within porphyry granite is located nearby the Cretaceous Pungam basin at the northeastern area in Republic of Korea. The Gajok gold-silver deposit is distinctively composed of a multiple-complex hydrothermal veins with comb, crustiform chalcedony quartz and vug textures, implying it was formed relatively shallower depth. The hypogene open-space filling veins could be divided into 5 paragenetic sequences, increasing tendency of Ag-rich electrum and Ag-phases with increasing paragenetic time. Electrum with high gold contents (${\sim}50$ atomic % Au) as well as sphalerite with high FeS contents (${\sim}6$ mole % FeS) are representative ore minerals in the middle stage. The late stage is characterized by silver-phase such like native silver and/or argentite, coexisting with Ag-rich electrum ($10{\sim}30$ atomic % Au) and Fe-poor sphalerite (< 1 mole % FeS). The ore-forming fluids evolution started at relatively high temperature and salinity (${\sim}360^{\circ}C$, ${\sim}7\;wt.%$ eq. NaCl) and were evolved by dilution and mixing mechanisms on the basis of fluid inclusion study. The gold-silver mineralization proceeded from ore-forming fluids containing greater amounts of less-evolved meteoric waters(${\delta}^{18}O$; $-0.6{\sim}-6.7\;%o$). These results imply that gold-silver mineralization of the Cretaceous Gaiok deposit formed at shallow-crustal level and could be categorized into low-sulfidation epithermal type, related to Cretaceous igneous activity.

• 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 Petrological Society of Korea Conference
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• 2009.05a
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• pp.118-119
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• 2009

• Economic and Environmental Geology
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• v.26 no.3
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• pp.259-265
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• 1993

The variation of H/F coefficient (Hubnerite/Feberite coefficient) and the temperature of formation with depth have been studied for the hydrothermal tungsten-quartz veins from Ssangjeon, Weolag, Cheongyang, and Sannae mines. All samples were selected at the same paragenetic stage and mineral assemblege according to depth. The studied mines provide an opportunity to examine and regional variations in wolframite composition in different provinces. The formation temperature is linearly related to the depth. At the Weolag, Cheongyang and Sannae mines, the H/F ratio of wolframite and filling temperatures of fluid inclusions in quartz show a general tendency to decrease at shallow levels, in spite of different geological settings. This implies the pH of fluid will decrease vertically with falling temperature and the high H/F ratio of wolframite in deep zone result in an increase of pH with depth. The Ssangjeon mine exhibits a tendency to increase slightly upwards at shallow level. This implies a different geochemical environment (high pH environment) for the Ssangjeon mine, as compared to the other three mines. The H/F coefficient pattern suggests that it is a useful geothermometer for vein-type tungsten deposits in Korea. The H/F coefficient as an indication of depth should be examined for use in exploration.

• Economic and Environmental Geology
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• v.43 no.5
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• pp.529-541
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• 2010

• Economic and Environmental Geology
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• v.47 no.4
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• pp.317-333
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• 2014

The Pocheon iron (-copper) deposit, located at the northwestern part of the Precambrian Gyeonggi massif in South Korea, genetically remains controversial. Previous researchers advocated a metamorphosed (-exhalative) sedimentary origin for iron enrichment. In this study, we present strong evidences for skarnification and Fe mineralization, spatially associated with the Myeongseongsan granite. The Pocheon deposit is composed of diverse carbonate rocks such as dolostone and limestone which are partially overprinted by various hydrothermal skarns such as sodic-calcic, calcic and magnesian skarn. Iron (-copper) mineralization occurs mainly in the sodic-calcic skarn zone, locally superimposed by copper mineralization during retrograde stage of skarn. Age data determined on phlogopites from retrograde skarn stage by Ar-Ar and K-Ar methods range from $110.3{\pm}1.0Ma$ to $108.3{\pm}2.8Ma$, showing that skarn iron mineralization in the Pocheon is closely related to the shallow-depth Myeongseongsan granite (ca. 112 Ma). Carbon-oxygen isotopic depletions of carbonates in marbles, diverse skarns, and veins can be explained by decarbonation and interaction with an infiltrating hydrothermal fluids in open system ($XCO_2=0.1$). The results of sulfur isotope analyses indicate that both of sulfide (chalcopyrite-pyrite composite) and anhydrites in skarn have very high sulfur isotope values, suggesting the $^{34}S$ enrichment of the Pocheon sulfide and sulfate sulfur was derived from sulfate in the carbonate protolith. Shear zones with fractures in the Pocheon area channeled the saline, high $fO_2$ hydrothermal fluids, resulting in locally developed intense skarn alteration at temperature range of about $500^{\circ}$ to $400^{\circ}C$.

• Economic and Environmental Geology
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• v.36 no.4
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• pp.257-268
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• 2003

The Cretaceous magmatism in the Gyeongsang Basin, Korea, led to the formation of two contrasting metallogenic provinces: the Haman-Gunbug-Goseong(-Changwon) (HGGC) and the Euiseong (EU). The mineralization in the HGGC metallogenic province represents copper, gold and iron of porphyry-related deposits that display close relationships in time and space with subvolcanic granitoids. Much of copper-gold-forming events in this province are consistently constrained to the period between ca. 89 and 81 Ma. The hydrothermal systems of copper-gold vein deposits in the HGGC province are associated with ore-forming fluids of high to intermediate temperature (300∼50$0^{\circ}C$) with high salinity (20∼55 equiv. wt. % NaCl). The ore-forming fluids become progressively more diluted by the incorporation of decreased quantities of magmatic water further from the nearby intrusion, suggesting significant input and fluid mixing of a meteoric water component to the magmatic fluids during the late stage of geothermal systems. In contrast, the EU metallogenic province is characterized by polymetallic vein deposits that are consistently constrained to a period of 78∼60 Ma. The geothermal systems of polymetallic vein deposits in the EU province are derived from a narrow range of intermediate temperature (200∼40$0^{\circ}C$) with relatively low salinity(1∼7 equiv. wt.% NaCl). It may represent a mixed fluid of magmatic and meteoric waters. The base-metal mineralization in the Gyeongsang Basin shows a close spatial and temporal distinction between the proximal environment derived from shallow-level granitoids in the southwestern HGGC province and the distal condition derived from volcanic environments in the northwestern EU province.