• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.1026-1036
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• 2014

Real-time monitoring for environmental factors (temperature, salinity, chlorophyll-a, etc.) and fugacity of carbon dioxide ($fCO_2$) was conducted at an oyster Crassostrea gigas farm in Goseong Bay, south coast of Korea during 2-4th of November, 2011. Surface temperature and salinity were ranged from $17.9-18.7^{\circ}C$ and 32.7-33.8, respectively, with daily and inter-daily variations due to tidal currents. Surface $fCO_2$ showed a range of $390-510{\mu}atm$ and was higher than air $CO_2$ during the study period. Surface temperature, salinity and $fCO_2$ are showed significant correlations with chl.-a and nutrients, respectively. It means when chl.-a value is high in surface water of the oyster farm, active biological production consume $CO_2$ and nutrients from environments and produce oxygen, suggesting a tight feedback between biological processes and environmental reaction. Thus, factors affecting the surface $fCO_2$ were evaluated using a simple mass balance. Temperature and biological productions by phytoplankton are the main factors for $CO_2$ drawdown from afternoon to early night, while biological respiration increases seawater $CO_2$ at night. Air-sea exchange fraction acts as a $CO_2$ decreasing gear during the study period and is much effective when the wind speed is higher than $2-3m\;s^{-1}$. Future studies about organic carbon and biological production/respiration are required for evaluating the roles of oyster farms on carbon sink and coastal carbon cycle.

• Economic and Environmental Geology
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• v.20 no.1
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• pp.35-60
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• 1987

The geochemical characteristics including minerals, major and trace elements chemistries of the Proterozoic, Jurassic and Cretaceous granites in Korea are systematically summarized and intended to decipher the origin and crystallization process in connection with the tectonic evolution. The granites in Korea are classified into three different ages of the granites with their own distinctive geochemical patterns: 1) Proterozoic granitoids; 2) Jurassic granites(cratonic and mobile belt); 3) Cretaceous-Tertiary granites. The Proterozoic granite gneisses (I-type and ilmenite-series) formed by metamorphism of the geochemically evolved granite protolith. The Proterozoic granites (S-type and ilmenite-series) produced by remobilization of sialic crust. The Jurassic granites (S-type and ilmenite-series) were mainly formed by partial melting of crustal materials, possibly metasedimentary rocks. The Cretaceous granites (I-type and magnetite-series) formed by fractional crystallization of parental magmas from the igneous protolith in the lower crust or upper mantle. The low temperature ($315{\sim}430^{\circ}C$) and small temperature variations (${\pm}20{\sim}30^{\circ}C$) in the cessation of exsolution of perthites for the Proterozoic and Jurassic granites might have been caused by slow cooling of the granites under regional metamorphic regime. The high ($520^{\circ}C$) and large temperature variations (${\pm}110^{\circ}C$) of perthites for the Cretaceous granites postulate that the rapid cooling of the granitic magma. In terms of the oxygen fugacity during the feldspar crystallization in the granite magmas, the Jurassic mobile belt granites were crystallized in the lowest oxygen fugacity condition among the Korean granites, whereas the Cretaceous granites in the Gyeongsang basin at the high oxygen fugacity condition. The Jurassic mobile belt granites are located at the Ogcheon Fold Belt, resulting by closing-collision situation such as compressional tectonic setting, and emplaced into a Kata-Mesozonal ductile crust. The Jurassic cratonic granites might be more evolved either during intrusion through thick crust or owing to lower degree of partial melting in comparison with the mobile belt granites. The Cretaceous granites are possibly comparable with a continental margin of Andinotype. Subduction of the Kula-Pacific ridge provided sufficient heat and water to trigger remelting at various subcrustal and lower crustal igneous protoliths.

• Economic and Environmental Geology
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• v.27 no.3
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• pp.219-229
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• 1994

The Sangra Pb-Zn deposit is located in the Gampo area. Most Cretaceous sedimentary rocks and Paleogene felsic intrusives in the study area have experienced intense propylitization. Such propylitization and Pb-Zn mineralization in ore veins are involved with the fluid having very low oxygen isotopic composition.Sulfurisotopic equilibrium temperature during the main Pb-Zn mineralization (late stage I) is calculated as $T=275^{\circ}{\sim}295^{\circ}C$. Oxygen and sulfur fugacity in late stage I fluid is estimated as $logfO_2=-34.4{\sim}-29.1$ and $logfS_2=-12.0{\sim}-8.2$ bars. It is inferred that the sulfur isotopic composition oflate stage I fluid was very high such as ${\delta}^{34}S_{{\Sigma}S}=+22.4{\sim}+22.5$‰ and the origin of sulfur was ocean water sulfate. Oxygen and hydrogen isotopic composition of water in ore-forming fluid was gradually increased and more abundantly affected by ocean water from early to late mineralization stage as follows; (late stage I) ${\delta}^{18}O_{H2O}=-7.2{\sim}-1.1$‰, ${\delta}D_{H2O}=-87{\sim}-84$‰, (stage II) ${\delta}^{18}O_{H2O}=-2.4{\sim}-0.8$‰, ${\delta}D_{H2O}=-39{\sim}-21$‰ (stage III) ${\delta}^{18}O_{H2O}=+0.7{\sim}+12.6$‰, ${\delta}D_{H_2O}=-49{\sim}-42$‰. The pH in ore-forming fluid was about 4.7 during late stage I and is thought to have been gradually decreased from late stage I to stage II mineralization.

• Economic and Environmental Geology
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• v.29 no.1
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• pp.1-11
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• 1996

Magnetite ores of the Janggun mine are embedded in dolomitic limestone of the Janggun Limestone Formation contacting with Chunyang granite, and are closely associated with skarn minerals. Mineralization of magnetite deposits can be divided into two stages as deep-seated skarn stage and shallow hydrothermal replacement stage. Mineralogies of skarn stage consist of magnetite, pyrrhotite and base-metal sulfides, and those of hydrothermal stage is base-metal sulfides, native bismuth, bismuthinite, tetrahedrite, boulangerite, bournonite and stannite. The FeS mole % in sphalerite and As atom % in arsenopyrite range from 22.47 to 26.30 and from 31.39 to 31.66 in skarn stage, and are from 17.54 to 32.54 and 28.87 to 30.70 in hydrothermal stage, respectively. Based on mineralization characteristics, mineral assemblages, chemical compositions and thermodynamic considerations, formation temperatures, sulfur fugacities ($-logf_2$), pH and oxygen fugacity ($-logfo_2$) estimated to be from 345 to $382^{\circ}C$, from 8.1 to 9.7atm, from 6.5 to 7.2 and from 30.5 to 31.2atm in the skarn stage, respectively, and temperature and $-logfs_2$ are from 245 to $315^{\circ}C$ and from 10.4 to 13.2atm in the hydrothermal stage.

• Economic and Environmental Geology
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• v.29 no.3
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• pp.395-405
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• 1996

The Donjin deposits which is located in the Chinan Basin, are emplaced along $N10{\sim}40^{\circ}E$ trending fissure sets. So it is a sort of fissure-filling ore deposits. The results of paragenetic studies suggest two stages of hydrothermal mineralization; stage I: base-metal sulfides stage, stage II: late base-metal sulfides, electrum and silver-bearing sulfosalts stage. Au: Ag ratios of the electrums show that Ag atomic% are higher than that of Au. The temperature and salinity of the Donjin deposits estimated from fluid inclusion and sulfur isotope geothermometry are as follows; stage I: $240{\sim}315^{\circ}C$, 2.4~7.1 NaCl eq. wt.%, stage II: $190{\sim}268^{\circ}C$, 4.6~8.4 NaCl eq. wt.%. The estimated oxygen and sulfur fugacity during first stage mineralization, based on phase relation of associated minerals, range from $10^{-35}{\sim}10^{-39.7}$ atm. and$10^{-11}{\sim}10^{-13.4}$ atm., respectively. All these evidences suggest that the Dongjin deposits are polymetallic meso-epithermal ore deposits.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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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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• v.28 no.6
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• pp.541-551
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• 1995

The Yeongdeog gold-silver deposits at Jipum, Gyeongsangbugdo, is of a middle Paleogene $(45.52{\pm}1.02Ma)$ vein type, and is hosted in shale and sandstone of Cretaceous age. Based on mineral paragenesis, vein structure and mineral assemblages, the ore mineralization can be divided into two distinct depositional stages. The early stage is associated with base-metals such as pyrite, arsenopyrite (27.99~30.99 at%), hematite, rutile, pyrrhotite, sphalerite (10.53~18.42 FeS mole%), chalcopyrite and galena with wallrock alteration such as chlorite, sericite and pyrite. The late stage is characterized by the Au-Ag mineralization such as electrum, Ag-bearing tetrahedrite, freibergite, pyrargyrite, unidentified mineral, pyrite, sphalerite (1.08~5.57 FeS mole%), chalcopyrite and galena. Fluid inclusion data indicate that fluid temperatures and salinities range from 343 to $227^{\circ}C$ and from 8.3 to 5.7 wt% eq. NaCl in early stage, respectively. Temperatures and salinities of NaCl eq. wt% range from 299 to $225^{\circ}C$ and from 12.9 to 4.3 in late stage, respectively. They suggest that complex cooling histories were occured by the mixing of the fluids. Sulfur fugacity $(-logfs_2)$ deduced by mineral assemblages and composition ranges from 8.3 to 14.7 atm. in early stage, and from 8.8 to 14.5 atm. in late stage. It suggests that the mineralization was related to decrease of temperature in early stage and fluctuations of $fS_2$ with decrease of temperature in late stage. Sulfur and oxygen isotope compositions are 4.48~5.60‰ and 9.25~10.8% in early stage, and late stage is 4.84~7.00‰ and 5.7‰, respectively. It indicated that hydrothermal fluids may be magmatic origin with some degree of mixing of another water during paragenetic time.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.3
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• pp.215-232
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• 2020

The study area of Nokjeonri in Yeongwol belongs to the Taebaeksan Mineralized District. Ca and Mg skarn and related ore mineralization are developed in the Pungchon formation along the contact with the Imog granite. Ca skarn hosted in limestone mostly comprises garnet and pyroxene. Mg skarn developed in dolomite includes olivine and serpentine. Magnetite-hematite and pyrrhotite(±scheelite)-pyritegalena-sphalerite were mineralized during early and late stage, respectively. Garnet compositions are dominated by andradite series in proximal area and grossular series in distal area. Pyroxene compositions correspond to diopside series in majority. These compositional changes indicate that the fluids varied from oxidizing condition to reducing condition due to increased reaction with carbonated wall rocks as the fluids moved from the granite to a distal place. Fe₂O₃ and MgO concentrations of magnetite are higher in Mg skarn than those in Ca skarn, while FeO shows opposite trend. The Zn/Fe ratio of sphalerite increases with distance from the Imog granite. The δ³⁴S values of sulfide minerals are similar to those of the Imog granite, indicating magmatic origin in ore sulfur. Mineralization was established in the order of skarn, oxide and sulfide minerals with decreasing temperature and oxygen fugacity and increasing sulfur fugacity.

• Economic and Environmental Geology
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• v.51 no.6
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• pp.493-507
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• 2018

The Wooseok deposit in Jecheon belongs to the Hwanggangri Mineralized Distict of the northeastern Ogcheon Metamorphic Belt. Its geology consists mostly of limestone of the Choseon Supergroup and the Cretaceous Muamsa granite intruded at the eastern area of the deposit. The deposit shows vertical occurrence of skarn and hydrothermal vein ores with W-Mo-Fe and Cu-Pb-Zn mineralization and skarn is developed only at lower levels of the deposit. Skarn minerals are replaced or cut by ore minerals in paragenetic sequence of magnetite-hematite, molybdenite-scheelite-wollframite, and higher abundances of pyrrhotite-chalcopyrite-pyrite-sphalerite-galena. Garnet has chemical compositions of $Ad_{65.9-97.8}Gr_{0.3-32.0}Pyr_{0.9-3.0}$, corresponding to andradite series, and pyroxene compositions are $Hd_{4.5-49.7}Di_{42.3-93.9}Jo_{0.5-7.9}$, prevailing in diopside compositions, both of which suggest oxidized conditions of skarnization. On the FeS-MnS-CdS ternary diagram, FeS contents of sphalerite in vein ores decrease with increasing MnS contents from bottom to top levels, possibly relating to W mineralization in deep and Pb-Zn mineralization in shallow level. Sulfur isotope values of sulfide minerals range from 5.1 to 6.8‰, reflecting magmatic sulfur affected by host rocks. W-Mo skarn and Pb-Zn vein mineralization in the Wooseok deposit were established by spatio-temporal variation of decreasing temperature and oxygen fugacity with increasing sulfur fugacity from bottom to top levels.

• Economic and Environmental Geology
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• v.27 no.4
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• pp.345-361
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• 1994

Lens shaped titanomagnetite ore bodies in the Soyeonpyeong iron mine are embedded in amphibolites, which were intruded into Precambrian metasediments such as garnet-mica schist, marble, mica schist, and quartz schist. Mineral chemistry, K-Ar dating and hydrogen and oxygen stable isotopic analysis for the amphibolites and titanomagnetite ores were conducted to interpret petrogenesis of amphibolite and ore genesis of titanomagnetite iron ore deposits. Amphibolites of igneous origin have unusually high content of $TiO_2$, ranging from 0.94 to 6.39 wt.% with an average value of 4.05 wt.%. REE patterns of the different lithology of the amphibolite show the similar trend with an enrichment of LREE. Amphiboles of amphibolites are consist mainly of calcic amphiboles such as ferro-hornblende, tschermakite, ferroan pargasite, and ferroan pargasitic hornblende. K-Ar ages of hornblende from amphibolite and gneissic amphibolite were determined as $440.04{\pm}6.39Ma$ and $351.03{\pm}5.21Ma$, respectively. This indicates two metamorphic events of Paleozoic age in the Korean peninsula which are correlated with Altin orogeny in China. The titanomagnetite mineralization seems to have occurred before Cambrian age based on occurrence of orebodies and ages of host amphibolites. The Soyeonpyeong iron ores are composed mainly of titanomagnetite, ilmenite, and secondary minerals such as ilmenite and hercynite exsolved in titanomagnetite. The temperature and the oxygen fugacity estimated by the titanomagnetite-ilmenite geothermometer are $500{\sim}600^{\circ}C$ (ave. $550^{\circ}C$) and about $2{\pm}10^{-23}bar$, respectively. Hornblendes from ores and amphibolites which responsible for magnetite ore mineralization, have a relatively homogeneous isotopic composition ranging from +0.8 to +3.9 ‰ in ${\delta}^{18}O$ and from -87.8 to -113.3 ‰ in ${\delta}D$. The calculated oxygen and hydrogen isotopic compositions of the fluids which were in equilibrium with hornblende at $550^{\circ}C$, range from 2.8 to 5.9‰ in ${\delta}^{18}O_{H2O}$ and from -60.41 to -81.31 ‰ in ${\delta}D_{H2O}$. The ${\delta}^{18}O_{H2O}$ value of magnetite ore fluids are in between +6.4 to + 7.9 ‰. All of these values fall in the range of primary magmatic water. A slight oxygen shift means that $^{18}O$-depleted meteoric water be acted with basic fluids during immiscible processes between silicate and titaniferous oxide melt. Mineral chemistry, isotopic compositions, and occurences of amphibolites and orebodies, suggest that the titanomagnetite melt be separated immisciblely from the titaniferous basic magma.