• Economic and Environmental Geology
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• 제50권6호
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• pp.435-443
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• 2017

The Hanae deposit is located within the Cretaceous Gyeongsang Basin. The Cu-bearing hydrothermal quartz vein formed by narrow open-space filling along fracture in the sedimentary rocks as Jindong Formation. The Hanae Cu-bearing hydrothermal deposit shows a paragenetic sequence of pyrrhotite-pyrite $\rightarrow$ pyrite-chalcopyrite-sphalerite(${\pm}$Bi-bearing tellurides) $\rightarrow$ Ag-bearing telluride mineralization $\rightarrow$ secondary mineralization. Fluid inclusion data indicate that the Hanae Cu-bearing hydrothermal mineralization occurred from dominantly aqueous fluids at temperatures of $400^{\circ}C-200^{\circ}C$. Equilibrium thermodynamic interpretation of the mineral paragenesis and assemblages combined with fluid inclusion data indicate that early main Cu-bearing ore mineralization in the vein starts at about $350^{\circ}C$ which corresponds to sulfur fugacity from about $10^{-9.2}$ to $10^{-8.7}bar$ with oxygen fugacity of about $10^{-32.1}$ to $10^{-29.8}bar$. Late main Cu-bearing ore mineralization in the vein occurs at about $250^{\circ}C$ which corresponds to sulfur fugacity from about $10^{-13.5}$ to $10^{-11.7}bar$ with oxygen fugacity of about $10^{-38.4}$ to $10^{-35.2}bar$. The late Ag-bearing telluride mineralization in the Hanae hydrothermal system occurs at about $200^{\circ}C$ which corresponds to minium Tellirium fugacity value of about $10^{-18}bar$ with sulfur fugacity of about $10^{-14.0}$ to $10^{-10.9}bar$.

• Korean Journal of Mineralogy and Petrology
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• 제34권2호
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• pp.107-120
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• 2021

The Komdok Pb-Zn deposit, which is the largest Pb-Zn deposit in Korea, is located at the Hyesan-Riwon metallogenic zone in Jiao Liao Ji belt included Paleoproterozoic Macheolryeong group. The geology of this deposit consists of Paleoproterozoic metasedimentary rocks, Jurassic Mantapsan intrusive rocks and Cenozoic basalt. The Komdok deposit which is a SEDEX type deposit occurs as layer ore and vein ore in the Paleoproterozoic metasedimentary rocks. Based on mineral petrography and paragenesis, dolomites from this deposit are classified four types (1. dolomite (D₀) as hostrock, 2. early dolomite (D₁) associated with tremolite, actinolite, diopside, sphalerite and galena from amphibolite facies, 3. late dolomite (D₂) associated with talc, calcite, quartz, sphalerite and galena from amphibolite facies, 4. dolomite (D₃) associated with white mica, chlorite, sphalerite and galena from quartz vein). The structural formulars of dolomites are determined to be Ca_1.00-1.20Mg_0.80-0.99Fe_0.00-0.01Zn_0.00-0.02(CO₃)₂(D₀), Ca_1.00-1.02M_0.97-0.99Fe_0.00-0.01Zn_0.00-0.02(CO₃)₂(D₁), Ca_0.99-1.03Mg_0.93-0.98Fe_0.01-0.05Mn_0.00-0.01As_0.00-0.01(CO₃)₂(D₂) and Ca_0.95-1.04Mg_0.59-0.68Fe_0.30-0.36Mn_0.00-0.01 (CO₃)₂(D₃), respectively. It means that dolomites from Komdok deposit have higher content of trace elements (FeO, MnO, HfO₂, ZnO, PbO, Sb₂O₅ and As₂O₅) compared to the theoretical composition of dolomite. These trace elements (FeO, MnO, ZnO, Sb₂O₅ and As₂O₅) show increase and decrease trend according to paragenetic sequence, but HfO₂ and PbO elements no show increase and decrease trend according to paragenetic sequence. Dolomites correspond to Ferroan dolomite (D₀, D₁ and D₂), and Ferroan dolomite and ankerite (D₃), respectively. Therefore, 1) dolomite (D₀) as hostrock was formed by subsequent diagenesis after sedimentation of Paleoproterozoic (2012~1700 Ma) silica-bearing dolomite in the marine evaporative environment. 2) Early dolomite (D₁) was formed by hydrothermal metasomatism origined metamorphism (amphibolite facies) associated with intrusion (1890~1680 Ma) of Paleoproterozoic Riwon complex. 3) Late dolomte (D₂) was formed from residual fluid by a decrease of temperature and pressure. and dolomite (D₃) in quartz vein was formed by intrusion (213~181 Ma) of Jurassic Mantapsan intrusive rocks.

• Journal of the Mineralogical Society of Korea
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• 제23권1호
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• pp.1-13
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• 2010

The Yugeum deposit in Youngduk in Gyungsangbuk-do is emplaced in the Cretaceous granitoids located in the Northeastem Gyeongsang Basin. Gold-bearing quartz veins filling the fracture with a direction of $N19^{\circ}{\sim}38^{\circ}W$ are most abundantly distributed within the Younghae granodiorite body. The formation of quartz veins can be classified into three main stages: barren quartz stage, auriferous quartz vein stage, and finally the extensive sulfide mineralization stage. Various sulfide minerals such as pyrite, chalcopyrite, galena, sphalerite, and arsenopyrite were precipitated during the hydrothermal gold mineralization process. Gold commonly occurs as fine-grained electrum in sulfides with high Au concentration (up to 93 wt%) compared to Ag. During the early gold mineralization stage, the temperature and pressure of the fluids are in the range of $220{\sim}250^{\circ}C$ and 730~1800 bar, and the oxygen fugacity is between $10^{-27}$ and $10^{-31.7}$ atm. On the other hand, the fluids of the late stage mineralization are characterized by temperature of $290{\sim}350^{\circ}C$ and pressure of 206~472 bar, and the oxygen fugacity is in the range of $10^{-26.3}{\sim}10^{-28.6}$ atm. The sulfur isotope compositions of sulfide minerals are in the range of $0.2{\sim}4.2^{\circ}/_{\circ\circ}$, while the ${\delta}^{34}SH_2S$ values range from 1.0 to $3.7^{\circ}/_{\circ\circ}$. The Ag/Au atomic ratios of electrum ranges from 0.15 to 1.10, and Au content is higher than Ag in most electrum. During the main gold mineralization stage at the relatively high temperature condition and with pH from 4.5 to 5.5, the stability of ${AuCl_2}^-$ increased while the stability of ${Au(HS)_2}^-$ decreased. Considering the pressure estimated in this deposit, the temperature of the ore fluid reached higher than $350^{\circ}C$ and ${AuCl_2}^-$ became an important species for the gold transportation. As mineralization proceeded with decreasing temperature and increasing pH and $f_{o2}$, the precipitation of sulfide minerals and accompanying electrum occurred.

• Economic and Environmental Geology
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• 제26권3호
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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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• 제50권2호
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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.

• Economic and Environmental Geology
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• 제23권3호
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• pp.287-308
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• 1990

The Ogmae alunite-kaolinite deposit occurs in acidic tuff, the Hwangsan Tuff, of upper Crataceous age in the Haenam volcanic field, SW Jeonnam. This deposit characterized by advanced argillic alteration formed $71.8{\pm}2.8{\sim}73.9{\pm}2.8$ Ma ago in very shallow depth environment with acid-sulfate solution. Wallrock alteration can be classified into four zones from the center to the margin of the deposit: alunite, kaolinite, illite, and silicified zone. The mineral assemblage in the alunite zone, ore zone, is alunite-quartz-pyritekaolinite. Consideration of stability relation of these minerals suggests that the maximum alteration temperature is estimated at about $250^{\circ}C$ with solution pH of 3 or below assuming that pressure does not exceed 0.3 Kb. Alunite occurs as two different types; replacement and vein-type deposit. The former one consists of fine grained alunite and the later one coarse grained and relatively pure alunite that formed by open space filling. Isomorphous substitution of Na for K in these two types of alunites range 0 to 40 %, indicating that Na/K ratio in the solution is spontaneously changed during the alteration process. Alunite which has higher Na substitution probably formed in an earlier stage while the solution sustain high Na/K ratio. K-Ar age of alunites indicate that the replacement alunite formed earlier($73.9{\pm}2.8Ma$) than the vein-type alunite($71.8{\pm}2.8Ma$). The ${\delta}^{34}S$ value of pyrite and alunite indicate that those minerals formed at isotopically nonequillibrium state. The ${\delta}^{16}O$ and ${\delta}D$ values, of kaolintics 5.0 to 9.0‰ and -54 to -99‰, respectively, indicate that those are formed by hydrothermal solution having magmatic origin which have been diluted by low ${\delta}D$ meteoric water.

• Journal of the Korean earth science society
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• 제25권6호
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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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• 제26권3호
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• pp.311-325
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• 1993

The Ohto and Tohyun copper mine which are located 4 km southeast of Euiseong, Gyeongsangbukdo, Republic of Korea show various common geologic and mineralogic features. Both copper deposits are of hydrothermal-vein types, and associated with fracture system developed during formation of the Geumseong-san caldera in late Cretaceous age. According to structures and mineral assemblages, the mineralization processes have progressed in four stages: three hypogene mineralization stages and one supergene stage. Three hypogene stages are 1) stage I forming $N5{\sim}20^{\circ}E$ veins in the Ohto mine, 2) stage II building $N5^{\circ}W{\sim}N5^{\circ}E$ veins in the Tohyun mine, and 3) stage ill bringing $N80^{\circ}E$ veins which crosscut veins of the stage II. The vein ores consist mainly of pyrite, arsenopyrite, galena and chalcopyrite, minor or trace amounts of magnetite, hematite, pyrrhotite, stannite, bournonite, boulangerite, stibnite, galenobismutite, native bismuth, marcasite, geothite and malachite. The main gangue minerals are quartz and calcite. Wallrock is altered by sericitization, chloritization, pyritization, carbonitization and argillization. Arsenic and copper contents in arsenopyrite increase from stage I to stage III (from 31.28 to 33043 atom.% As) and (from 0.04 to 0040 atom.% Co). Going from stage I to stage III Fe and Mn contents in sphalerite decreases from 12.56 to 0.44 wt.% and from 0.24 to 0.01 wt.%, respectively. The compositional data of arsenopyrite in the early stage I indicate a temperature of $420{\sim}365^{\circ}C$ and sulfur fugacity of $10^{-6.5}{\sim}10^{-8.3}$ atm. Chalcopyrite and pyrrhotite assemblage suggest that Middle stage I was deposited at below $334^{\circ}C$. The compositional data of arsenopyrite in early stage II suggest a temperature range of $425{\sim}390^{\circ}C$ and sulfur fugacity codition of $10^{-6.4}{\sim}10^{-7.3}$ atm. Based on fluid inclusion the Middle stage II was regarded as to be deposited at $420{\sim}337^{\circ}C$ (Chi et al., 1989). Referring composition of sphalerite and stannite middle-late stage II seem to be deposited around $246^{\circ}C$ and $10^{-16.5}$ atm. sulfur fugacity. The ${\delta}^{34}S$ values of sulfide minerals in the Stage I, II, III range from 4.9 to 7.6%0 and indicate igneous ore fluid origin. Based on differences in mineral assemblages, chemical composition and chemical environments of Ohto and Tohyun mine its mineralization are considered to be formed at diffent mineralization ages and by different ore fluids.

• Economic and Environmental Geology
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• 제21권1호
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• pp.45-56
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• 1988

Many hydrothermal skarn-type iron ore deposits inchiding Mulgeum, Yangseong, Maeri and Kimhae mines are distributed in the south-eastern Gyeongnam Province, Korea. The deposits are magnetite veins which occurred in propylitized andesitic rock near the contact with late Cretaceous Masanite. Symmetrical zoned skarns are commonly developed around the magnetite veins. The order of the skarn zones from the vein is garnet-quartz skarn, epidote skarn, and epidote-orthoclase skarn. The garnets include isotropic or anisotropic andradite($Ad_{100{\sim}70}$), and the epidotes are composed of pistacite($Ps_{21-31}$). Fe contents of the epidotes generally increase toward the magnetite veins. Epidotes and garnets often show compositional variations from grain to grain, that is, their Fe and Al contents vary inversely. This suggests that the variations depend mainly upon $fo_2$ during the skarnization. Oxygen and carbon isotope analyses of minerals from andesitic rock, micrographic granite, major skarn zones and post-mineralization zones were conducted to provide the information on the formation temperature, the origin and the evolution of the hydrothermal solution forming the iron ore deposits. Becoming more distant from the ore vein, temperatures of skarn zones represent the decreasing tendency, but most ${\delta}O^{18}$ and ${\delta}O^{18}_{H_2O}$ values of skarn minerals represent no variation trend, and also the values are relatively low. Judging from all the isotopic data from the ore deposits, the major source of hydrothemal solution altering the skarn zones and precipitating the ore bodies was magmatic water derived from the more deeply seated micrographic granite. This high temperature hydrothermal solution rising through the fissures of propylitized andesitic rock was mixed with some meteoric water, and the extensive isotopic exchange occurred with the propylitized andesitic rock. During this process, the temperature and ${\delta}O^{18}_{H_2O}$ value of hydrothermal solution were lowered gradually. At the stage of iron ore precipitation, because after all the alteration was already finished, the oxygen isotopic exchange with the wall rock was nearly not taken. The relatively high ${\delta}O^{18}$ and ${\delta}O^{18}_{H_2O}$, and relatively low ${\delta}C^{13}$ values of calcites of post mineralization stage, are the results of leaching of the high ${\delta}O^{18}$ chert xenolith in the andesitic rock and low ${\delta}C^{13}$ andesitic rock.

• Economic and Environmental Geology
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• 제42권3호
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• pp.167-175
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• 2009

The geology of Sepola district in Mali is consisted of Birrimian group with metasedimentary rocks of lower Proterozoic and volcanoclastics, and later intrusive igneous rocks. Ore diposit in this district has the characteristics of vein- and disseminated-type gold deposit which was formed by infilling the secondary fracture zones related to the large-scale fault zone of NW direction within Birrimian group. It is confirmed as promising that Barani district has the gold grade of 0.53${\sim}$9.21 g/t with the extension of 1.3 km and width of 1 to 20.1 m. The ore mineralogy is simple with electrum, pyrite and galena. Fineness of gold grain ranges from 848 to 915(average 891) indicating mesothermal to hypothermal environment. Fluid inclusions are classified as liquid-rich type I. gas-rich type II and liquid-$CO_2$ bearing type III. Primary and pseudosecondary inclusions homogenize from 236 to 393$^{\circ}C$ with salinity of 0.0 to 8.6 wt% NaCl. Secondary inclusions homogenize from 103 to 184$^{\circ}C$ with salinity of 0.7 to 8.6 wt.%. From the relationship between homogeniztion temperature and salinity, it may be thought that auriferous fluid experienced dilution and cooling through inflow of meteoric water after fluid unmixing derived from pressure decrease in the temperature range of 400 to 250$^{\circ}C$. From the massive occurrence of quartz vein, simple mineralogy with paucity of sulfide, and presence of liquid-$CO_2$ bearing with high homogenization temperature, it is thought that gold mineralization in Sepola district correspods to the mesothermal to hypothermal ore deposit.