• Economic and Environmental Geology
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• v.24 no.4
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• pp.335-346
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• 1991

It is observed that calcareous nodules of the Hwajeol Formation are locally skarnized in the Sangdong district, in which the skarn mineralization extends 5 Km westward from the Sangdong mine area to the Hwajeolchi area. After a hidden granite beneath the Sangdong mine was discovered by exploration drillings, the exploration teams of the Sangdong mine and the Korean Mining Promotion Corporation have assumed that the skarn nodule of the Hwajeol Formation was derived from emplacement of a granite in deep place and the occurrence of hidden ore bodies below the skarn, and they have discovered high grades of tungsten orebody in the same horizon of the Sangdong ore body. Mutual genetic relatioships between epidote and garnet may be explained by following chemical reactions $Ca_2FeA_{12}$ $Si_3O_{12}(OH)+CaCO_3=Ca_3(Fe,\;Al)_2$ $SiO_{12}+1/2CO_2+1/2H^+Ca_3FeSi_3O_{12}+SiO_2+CO_2=2CaFeSi_{12}O_6+CaCO_3+1/2O_3$. It is concluded that epidote and garnet are useful as target minerals indicating a potential occurrence of deep seated hidden ore body. Since the epidote may inform the emplacement of the granite, while the garnet in the skarn nodule of the Hwajeol Formation may reflect a strong hydrothermal mineralization taking place from the depth.

• Economic and Environmental Geology
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• v.42 no.1
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• pp.1-8
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• 2009

The Haman mineralized area is located within the Cretaceous Gyeongsang Basin along the southeastern part of the Korean peninsula. Almost all occurrences in the Haman area are representative of copper-bearing polymetallic hydrothermal vein-type mineralization. Within the area are a number of fissure-filling hydrothermal veins which contain tourmaline, quartz and carbonates with Fe-oxide, base-metal sulfide and sulfosalt minerals. The Gunbuk, Jeilgunbuk and Haman mines are each located on such veins. The ore and gangue mineral paragenesis can be divided into three distinct stages: Stage I, tourmaline + quartz + Fe-Cu ore mineralization; Stage II, quartz + sulfides + sulfosalts + carbonates; Stage III, barren calcite. Equilibrium thermodynamic data combined with mineral paragenesis indicate that copper minerals precipitated mainly within a temperature range of $350^{\circ}C$ to $250^{\circ}C$. During early mineralization at $350^{\circ}C$, significant amounts of copper ($10^3$ to $10^2\;ppm$) could be dissolved in weakly acid NaCl solutions. For late mineralization at $250^{\circ}C$, about $10^0$ to $10^{-1}\;ppm$ copper could be dissolved. Equilibrium thermodynamic interpretation indicates that the copper in the Haman-Gunbuk systems could have been transported as a chloride complex and the copper precipitation occurred as a result of cooling accompanied by changes in the geochemical environments ($fs_2$, $fo_2$, pH, etc.) resulting in decrease of solubility of copper chloride complexes.

• Proceedings of the KSEEG Conference
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• 1999.04a
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• pp.153-153
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• 1999

• Economic and Environmental Geology
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• v.24 no.2
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• pp.107-129
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• 1991

The Yonghwa gold-silver deposits are emplaced along $N15^{\circ}{\sim}25^{\circ}W$ trending fissures in middle Cretaceous porphyritic granite or Precambrian Sobaegsan gneiss complex. The results of paragenetic studies suggest that vein filling can be subdivided into four identifiable stages; state I: the main sulfide stage, characterized by base-metal sulfide minerals, iron oxides and minor electrum, stage II: electrum stage, stage III: electrum and silver-bearing sulfosalts stage, stage IV: post ore stage of carbonates and quartz. The ore mineralogy suggests that depositional temperature of the formation of the gold and silver minerals are estimated as 200 to $250^{\circ}C$ and 140 to $180^{\circ}C$, respectively. Sulfur fugacity of the formation of the gold and silver minerals are estimated as $10^{-14.0}$ to $10^{-12.2}$ atm and $10^{-18.5}$ to $10^{-17.2}$ atm, respectively. A consideration of the pressure regime during ore deposition bases on the fluid inclusion evidence of boiling suggests lithostatic pressure of less than 180 bars. This range of pressure indicate that vein system lay at depth of 700m below the surface at the time during mineralization. Salinities of ore-bearing fluids range from 0.4 to 6.9 wt.% equivalent NaCl. The sulfur and carbon isotopic data reveal that these elements were probably derived from a deep-seated source. The ${\delta}^{18}O$ of the hydrothermal fluid was determined from ${\delta}^{18}O$ values of quartz and calcite. Oxygen and hydrogen isotopic studies reveal that meteoric water dominate over ore-bearing fluid.

• 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.26 no.2
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• pp.145-154
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• 1993

Gold-silver deposits in the Kwangyang-Seungju area are emplaced along $N4^{\circ}{\sim}10^{\circ}W$ to $N40^{\circ}{\sim}60^{\circ}W$ trending fissures and fault in Pre-cambrian Jirisan gneiss complex or Cretaceous diorite. Mineral constituents of the ore from above deposits are composed mainly of pyrite, arsenopyrite, pyrrhotite, magnetite, sphalerite, chalcopyrite, galena and minor amount of electrum, tetrahedrite, miargyrite, stannite, covellite and goethite. The gangue minerals are predominantly quartz and calcite. Gold minerals consist mostly of electrum with a 56.19~79.24 wt% Au and closely associated with pyrite, chalcopyrite, miargyrite and galena. K-Ar analysis of the altered sericite from the Beonjeong mine yielded a date of $94.2{\pm}2.4\;Ma$ (Lee, 1992). This indicates a likely genetic tie between ore mineralization and intrusion of the middle Cretaceous diorite ($108{\pm}4\;Ma$). The ${\delta}^{34}S$ values ranged from +1.0 to 8.3‰ with an average of +4.4‰ suggest that the sulfur in the sulfides may be magmatic origin. The temperatures of mineralization by the sulfur isotopic composition with coexisting pyrite-galena and pyrite-chalcopyrite from Beonjeong and Jeungheung mines were $343^{\circ}C$ and $375^{\circ}C$ respectively. This temperature is in reasonable agreement with the homogenization temperature of primary fluid inclusion quartz ($330^{\circ}C$ to $390^{\circ}C$; Park.1989). Four samples of quartz from ore veins have ${\delta}^{18}O$ values of +6.9~+10.6‰ (mean=8.9‰) and three whole rock samples have ${\delta}^{18}O$ values of +7.4~+10.2‰ with an average of 7.4‰. These values are similar with those of the Cretaceous Bulgugsa granite in South Korea (mean=8.3‰; Kim et al. 1991). The calculated ${\delta}^{18}O_{water}$ in the ore-forming fluid using fractionation factors of Bulgugsa et al. (1973) range from -1.3 to -2.3‰. These values suggest that the fluid was dominated by progressive meteoric water inundation through mineralization.

• Economic and Environmental Geology
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• v.36 no.2
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• pp.75-87
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• 2003

The Haman-Gunbuk mineralized area is located within the Cretaceous Gyeongsang Basin along the southeastern part of the Korean peninsula. Major ore minerals, magnetite, scheelite, molybdenite and chalcopyrite, together with base-metal sulfides and minor sulfosalts, occur in fissure-filling tourmaline, quartz and carbonates veins contained within Cretaceous sedimentary and volcanic rocks anu/or granodiorite (118{\pm}$3.0 Ma). The ore and gangue mineral paragenesis can be divided into three distinct stages: Stage 1, tourmaline+quartz+Fe-Cu ore mineralization; Stage II, quartz+sulfides+sulfosalts+carbonates; Stage 111, barren calcite. Earliest fluids are recorded in stage I and early por-tions of stage II veins as hypersaline (35~70 equiv. wt.% NaCl+KCl) and vapor-rich inclusions which homogenize from ~30$0^{\circ}C$ to $\geq$50$0^{\circ}C$. The high-salinity fluids are complex chloride brines with significant concentrations of sodium, potassium, iron, copper, and sulfur, though sulfide minerals are not associated with the early mineral assemblage produced by this fluid. Later solutions circulated through newly formed fractures and reopened veins, and are recorded as lower-salinity(less than ~20 equiv. wt.% NaCl) fluid inclusions which homogenize primarily from ~200 to 40$0^{\circ}C$. The oxygen and hydrogen isotopic compositions of fluid in the Haman-Gunbuk hydrothermal system represents a progressive shift from magmatic-hydrothermal dominance during early mineralization stage toward meteoric-hydrothermal dominance during late mineralization stage. The earliest hydrothermal fiuids to circu-late within the granodiorite stock localiring the ore body at Haman-Gunbuk could have exsolved from the crystal-lizing magma and unmixed into hypersaline liquid and $H_2O$-NaCl vapor. As these magmatic fluids moved throughfractures, tourmaline and early Fe, W, Mo, Cu ore mineralization occurred without concomitant deposition of othersulfides and sulfosalts. Later solutions of dominantly meteoric origin progressively formed hypogene copper and base-metal sulfides, and sulfosalt mineralization.

• Journal of the Korean earth science society
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• v.25 no.6
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• pp.484-494
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• 2004

The Soowang Au-Ag deposits occur as quartz veins which filled fissures in middle Cretaceous porphyritic granite an/or gneiss of the Precambrian Sobaegsan gneiss complex. The paragenetic studies suggest that vein filling can be divided into four identifiable stages (I to IV). Stage I is the main sulfide stage, characterized by the deposition of base-metal sulfide and minor electrum. Stage II is the electrum stage, whereas stage III represents a period of the deposition of silver-bearing sulfosalts and minor electrum. Stage IV is the post ore stage. Mineralogical and fluid inclusion evidences suggest that mineralization of the Soowang deposits were deposited by the cooling of the fluids from initial high temperatures 300$^{\circ}C$ to later low temperatures 150$^{\circ}C$. The salinity of the fluids were moderate, ranging from 10.4wt.% equivalent NaCl in sphalerite to 3.1wt.% equivalent NaCl in barite. The gold-silver mineralization of the Soowang mine occurred at temperatures between 140 and 250$^{\circ}C$ from fluids with log $fs_2$ from -12 to -18 atm. A consideration of the pressure regime during ore deposition, based on the fluid inclusion evidence of boiling, suggests lithostatic pressure of less than 210 bars. This pressure condition indicates that vein system of the Soowang deposit formed at depth around 800 m below the surface at the time of gold-silver mineralization.

• Economic and Environmental Geology
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• v.21 no.4
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• pp.367-380
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• 1988

Most of the gold (-silver) vein deposits at Yeongdong District are mainly distributed in the precambrian metamorphic rocks. Based on the Ag/Au total production and ore grade ratios, the chemical composition of electrum and the associated sulfides, the gold(-silver) deposits at Yeongdong District may be classified into 4 classes: pyrrhotite - type gold deposits( I), pyrite - type gold deposits (IT A; massive vein), pyrite - type gold deposits (II B; nonmassive vein) and argentite - type gold - silver deposits(III). The chemical study on electrum(including native gold) revealed that Au content (2.8 to 92.4 atomic%) of electrums varies very widely for different classes of deposits. The Au content of electrum associated with pyrrhotite (Class I), ranging from 47.1 to 92.4 atomic% Au, is clearly higher than that associated with pyrite (Classes IIA, IIB and III). In contrast, classes I, II, and III deposits do not show clear differences in Au content of electrum. In general, pyrrhotite - type gold deposits(I) are characterized by features such as simply massive vein morphology, low values in the Ag/Au total production and ore grade ratios, the absence or rarity of silver - bearing minerals except electrum, and distinctively simple mineralogy. Although the geological and mineralogical features and vein morphology of pyrite - type gold deposits(IIA)are very similar to those of pyrrhotite - type gold deposits (I), Class II A deposits reveal significant differences in the associated iron sulfide (i. e. pyrite) with electrum and Au content of electrum. The Ag/Au total production and ore grade ratios from Class II A deposits are relatively slightly higher than those from Class I deposits. Pyrite - type gold deposits(II B) and argentite - type gold - silver deposits (III) have many common features; complex vein morphology, medium to high values in the Ag/Au total production and ore grade ratios and the associated iron sulfide (i. e. pyrite). In contrast to Class II B deposits, Class III deposits have significantly high Ag/Au total production and ore grade ratios. It indicates distinct difference in the abundance of silver minerals (i. e. native silver and argentite). The fluid inclusion analyses and mineralogical data of electrum tarnish method indicate that the gold mineralization of Classes I and II A deposits was deposited at temperatures between $230^{\circ}$ and $370^{\circ}C$, whereas the gold (-silver) mineralization of Classes ITB and ill formed from the temperature range of $150^{\circ}-290^{\circ}C$. Therefore, Classes I and IT A deposits have been formed at higher temperature condition and/or deeper positions than Classes IIB and III.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.85-96
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• 2017

Gold mineralization of Samjeong and Yongjang gold mines in Uichang area shows characteristics of Bonanza-type gold deposits. Ores are mainly developed along the contact parts between quartz vein and arkosic sandstone beds(Fe-rich bed) in sedimentary rock. Electrum, silver sulfide and sulfate minerals are mainly in the ores. On the other hand, gold mineralization is less developed in cherty rock and andesitic rock than arkosic sandstone. The study highlights characteristics of gold precipitation in the deposit on the basis of numerical modelling of the reactions between the assumed hydrothermal ore fluids with multicomponent heterogeneous equilibrium calculations. Aqueous species, gases and minerals, containing electrum are included in the calculations. The reaction result between hydrothermal ore fluids and arkosic sandstone show that pH increasing in the ore-forming fluid would trigger precipitation of quartz, chlorite, sericite, chalcopyrite, galena, pyrite, electrum, actinolite and feldspar. The numerical modelling also illustrates the drastic increase of pH and desulfidation lead to precipitation of electrum. Ag/Au ratios in the ore vary with pH conditions and subsequently precipitation of silver-bearing sulfides such as acanthite and polybasite. The modelling of the reaction between andesitic rock and ore-forming fluid shows that mineral assemblages of the case are analogous to ones of the reaction between arkosic sandstone and fluid except the latter has little portion of electrum. The abovementioned modelling results suggest that gold-silver mineralization is bounded by host rocks at the study area.