• Economic and Environmental Geology
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• v.46 no.2
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• pp.153-163
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• 2013

The Ogcheon Au-Ag deposit consists of two quartz veins that fill the NE or NW-trending fissures in the metasedimentary rocks of unknown age. The quartz veins occur mainly in the massive type with partially breccia and cavity. They can be found along the strike for about minimum 50 m and varied in thickness from 0.1 to 0.3 m. The mineralogy of quartz veins from the Ogcheon deposit is mainly composed of hydrothermal alteration minerals such as pyrite, quartz, sericite, chlorite, clay minerals and sulfides including pyrite, pyrrhotite, arsenopyrite, sphalerite, chalcopyrite and galena. Fluid inclusion data from quartz indicate that homogenization temperatures and salinity of mineralization range from 184 to $362^{\circ}C$ and from 0.0 to 6.6 wt.% eq. NaCl, respectively. These suggest that ore forming fluids were progressively cooled and diluted from mixing with meteoric water. Sulfur(${\delta}^{34}S$: 0.4~8.4‰) isotope composition indicates that ore sulfur was derived from mainly magmatic source although there is a partial derivation from the host rocks. The calculated oxygen(${\delta}^{18}O$: 4.9~12.1‰) and hydrogen(${\delta}D$: -92~-74‰) isotope compositions suggest that magmatic and meteoric ore fluids were equally important for the formation of the Ogcheon deposit and then overlapped to some degree with another type of meteoric water during mineralization.

• Economic and Environmental Geology
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• v.44 no.3
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• pp.193-201
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• 2011

The Geopung Cu deposit consists of two subparallel quartz veins that till the NE-trending fissures in Triassic Cheongsan granite. The quartz veins occur mainly massive with partially cavity and breccia. They can be followed along strike for about 500 m and varies in thickness from 0.2 to 2.2 m. Based on the mineralogy and paragenesis of veins, mineralization of quartz veins can be divided into hypogene and supergene stages. Hypogene stage is associated with hydrothermal alteration minerals such as sericite, pyrite, quartz, chlorite, clay minerals and sulfides such as pyrite, arsenopyrite, pyrrhotite, marcasite, sphalerite, stannite, chalcopyrite and galena. Supergene stage is composed of geothite. Fluid inclusion data from quartz indicate that homogenization temperatures and salinity of hypogene stage range from 163 to $356^{\circ}C$ and from 0.2 to 7.2 wt.% eq. NaCl, respectively. They suggest that ore forming fluids were progressively cooled and diluted from mixing with meteoric water. Sulfur (${\delta}^{34}S$: 4.3~9.2‰) isotope composition indicates that ore sulfur was derived from mainly magmatic source although there is a partial derivation from the host rocks. The calculated oxygen (${\delta}^{18}O$: 0.9~4.0‰) and hydrogen (${\delta}D$: -86~-69‰) isotope compositions suggest that magmatic and meteoric ore fluids were equally important for the formation of the Geopung Cu deposit and then overlapped to some degree with another type of meteoric water during mineralization.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.575-589
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• 2009

Groundwater has been extracted for irrigation in Sacheon-Hadong area, which is close to the South Sea. We analyzed chemical components of groundwater to examine the effects of seawater intrusion and agricultural activities in the study area. Most groundwater samples displayed the Na/Cl concentration ratios similar to that of seawater (0.55) with an increasing tendency of electrical conductivity ($227-7,910\;{\mu}S/cm$) towards the coast. In addition, statistical interpretation of the cumulative frequency curves of Cl and $HCO_3$ showed that 30.1% of the groundwater samples were highly affected by seawater intrusion. Groundwaters in the study area mostly belonged to the Ca-Cl and Na-Cl type, demonstrating that they were highly influenced by seawater intrusion and cation exchange. The result of oxygen-hydrogen isotope analysis demonstrated slightly higher $\delta^{18}O$ ((-8.53)-(-6.13)‰) and ${\delta}D$ ((-58.7)-(-43.7)‰) comparing to mean oxygen-hydrogen isotope ratios in Korea. As a result of nitrogen isotope analysis, the $\delta^{15}N-NO_3$ values ((-0.5)-(19.1)‰) indicate two major sources of nitrate pollution (organic nitrogen in soil and animal and human wastes) and mixed source of the two. However, denitrification may partly contribute as a source of nitrogen. According to factor analysis, four factors were identified among which factor 1 with an eigenvalue of 6.21 reflected the influence of seawater intrusion. Cluster analysis indicated the classification of groundwater into fresh, saline, and mixed ones.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.13-23
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• 2001

Bentonite layers are intercalated within the basal conglomerates in the Tertiary sedimentary basins of Kampo, Janggi and Pohang, southeastern Korea. Eighteen samples of the bentonites went through X-ray diffraction, scanning electron microscopy, heavy mineral analyses, chemical analyses and oxygen, hydrogen stable isotope analyses to define the mineralogical characters of the bentonites. Heavy minerals such as zircons, apatites, amphiboles and biotites separated from bentonites show clean and euhedral surfaces, which are the characteristic features of volcanic origin. But biotites from the Chunbook Conglomerate are found as altered and heavily broken flakes which implies longer transportation of these bentonites. $TiO_{2}/Al_{2}O_{3} ratios of <2 $\mu$m particle fractions (the Chunbook Conglomerate 0.031; Janggi 0.029; Kampo 0.025) suggest that those are originated from volcanic tuffs. That is, the higher the value is, the more mafic in chemical compositions of the original tuffs. Authigenic montmorillonite and zeolite minerals were observed by SEM, which indicates diagenesis origin of bentonites. But the samples from the Chunbook Conglomerate showed only chaotically packed clay flakes in the matrix of sands or conglomerates, which implies detrital influence, not authigenic origin. The structural formulae of montmorillonite from these basins reflects their environment of formation. Fe (Ⅵ) can show the redox condition of its past environment and much lower $Fe^{2+}(Ⅵ)/Fe^{3+}(Ⅵ)$ ratios in montmorillonite of the Chunbook Conglomerate imply the greater oxidizing influence. Calculated burial depths from oxygen stable isotope data of the samples from the Chunbook Conglomerate generally fall to the range of 929~963 m whereas the real burial depth of this area is only 530~580 m. This could be explained as the bentonites of the Chunbook conglomerate had not been formed in situ. Discriminant analyses with the data from chemical analyses and structural formulae of montmorillonites show that bentonites from three different basins could definitely be distinguished with each other. This result arises from the different chemical compositions of original volcanic ashes and the difference of sedimentary environments.

• Economic and Environmental Geology
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• v.28 no.2
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• pp.93-108
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• 1995

The Bobae sericite deposit occurs in rhyodacite of the Cretaceous volcanogenic sedimentary rocks, Upper Yucheon Group, in the western part of Pusan. The alteration zones are divided into the phyllie and prophylitic zone based on the mineral assemblages. The phyllic zone is subdivided into three subzones; Andalusite-Pyrophyllite, Sericite and Albite subzones. Oxides vs. $Al_2O_3$ contents show variations corresponding to mineral assemblage in each alteration zone. On the basis of bulk chemical compositions, it was found that $SiO_2$ increases in the Andalusite-Pyrophyllite subzone and $K_2O$ in the Sericite subzone. The oxygen, hydrogen and sulfur isotope analysis indicates that the fluids were originally derived from the residual magmatic solution. It has been mixed with abundant meteoric water later. The ore-forming temperatures obtained from sericite (illite) geothermometer are about $250{\sim}350^{\circ}C$. Considering the phase stability relation, PoT conditions of the andalusite-pyrophyllite subzone were estimated to be less than 0.5 kb and almost $400^{\circ}C$, respectively. The K-Ar ages of sericites indicate that the clay deposit is genetically related to the Cretaceous-Paleogene Masan Hornblende-Biotite Granite.

• Economic and Environmental Geology
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• v.26 no.3
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• pp.289-309
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• 1993

Milyang pyrophyllite deposit which was formed by hydrothermal alteration occurs in Late Cretaceous andesitic tuff in the Milyang area, Gyeongsangnamdo. The wall rock alteration and genesis of the Milyang pyrophyllite deposit were studied. The ore minerals are composed dominantly of pyrophyllite accompanied by small amounts of quartz, kaolinite, pyrite, dumortierite and diaspore. The alteration halo of this deposit can be divided into three zones on the basis of mineral assemblage; pyrophyllite, sericite and chlorite zone. The common mineral assemblages of each alteration zone are as follows: (1) pyrophyllite zone; pyrophyllite-quartz-kaolinite-pyrite-dumortierite-diaspore, (2) sericite zone; sericite-quartz-pyrite-kaolinite, and (3) chlorite zone; chlorite-plagioclase-quartz. Major element chemistry shows that characteristic depletion in MgO, CaO, and $Na_2O$ and relative increase in FeO from less altered chlorite zone to extensively altered pyrophyllite zone corresponding to variation in mineral assemblages. The paragenesis of ore minerals, oxygen isotope data, chlorite and illite geothermometry suggest that ore deposit was formed at about $250{\sim}330^{\circ}C$. Both hydrogen and silica activities are high in pyrophyllite zone. Potassium activity increases in sericite zone while hydrogen activity becomes low in chlorite zone. The pyrophyllite zone was formed relatively higher temperature than those of sericite and chlorite zones. The ore fluid was considered to be magmatic water in origin derived from the residual granitic magma which interacted with meteoric water.

• Economic and Environmental Geology
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• v.32 no.2
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• pp.129-139
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• 1999

Hydrothermal gold deposits of the Trabong district in Vietnam occur as single-stage quartz $\pm$ calcite veins (0.3-1.2 m thick) which fill fault fractures in graphite-bearing gneiss and schist of the Chulai Complex and Kham Duc Formation of the Proterozoic age. Ore grades are 1.3 to 92.4 g/ton Au. Ore mineralogy is very simple, consisting mainly of pyrite with minor amounts of base-metal sulfides and electrum. Gold grains occur in two assemblages as follows: (1) early, Fe-rich (7.2-10.4 mole % FeS) sphalerite + electrum (50.4-64.3 atom % Au) assemblage occurring as inclusions in pyrite; (2) late, Fe-poor «4.7 mole % FeS) sphalerite + galena + electrum (47.6-81.7 atom % Au) assemblage occurring along fractures of pyrites. Based on fluid inclusion data and thermochemical considerations of ore mineral assemblages, ore minerals were formed at high temperatures (about $230^{\circ}C$ to $420^{\circ}C$) from $H_{2}O-CO_{2}(-CH_{4})$-NaCI fluids with the sulfur fugacity of about $10^{-6}$ to $10^{-10}$ atm. Fluid inclusion data also indicate that ore mineralization occurred mainly as a result of fluid unmixing accompanying $CO_2$ effervescence. Calculated oxygen and measured hydrogen isotope compositions of mineralizing waters (${\delta}^{18}O_{V-SMOW}$ values = 5.3 to 8.6$\textperthousand$, ${\delta}D_{V-SMOW}$ values = - 60 to - 52$\textperthousand$), along with the sulfur isotope compositions of vein sulfides (${\delta}^{34}S_{CDR}$ values = - 1.2 to 2.8$\textperthousand$) and carbon isotope compositions of inclusion $CO_2$ (${\delta}^{13}C_{PDB}$ values = - 4.7 to - 2.0$\textperthousand$) indicate that the high temperature (mesohypothermal) gold mineralization formed from a magmatic fluid.

• Economic and Environmental Geology
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• v.21 no.2
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• pp.149-164
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• 1988

Electrum-sulfide mineralization of the Samgwang and Sobo mines of the Cheongyang Au-Ag area was deposited in two stages of quartz and calcite veins that fill fault zones in granite gneiss. Radiometric dating indicates that mineralization is Early Cretaceous age (127 Ma). Fluid inclusion and sulfur isotope data show that ore mineralization was deposited at temperatures between $340^{\circ}$ and $180^{\circ}C$ from fluids with salinities of 1 to 8 wt. % equiv. NaCl and a ${\delta}^{34}S_{{\sum}S}$ value of 2 to 5 per mil. Evidence of fluid boiling (and $CO_2$ effervescence) indicates a range of pressures from < 200 to $\approx$ 700 bars, corresponding to depths of ${\approx}1.5{\pm}0.3\;km$ in a hydrothermal system which alternated from lithostatic toward hydrostatic conditions. Au-Ag deposition was likely a result of boiling coupled with cooling. Meaured and calculated hydrogen and oxygen isotope values of ore-forming fluids indicate a significant meteoric water component, approaching unexchanged paleometeoric water values. Comparison of these values with those of other Korean Au-Ag deposits reveals a relationship among depth, Au/Ag ratio and degree of water-rock interaction. All investigated Korean Jurassic and Cretaceous gold-silver-bearing deposits have fluids which are dominantly evolved meteoric waters, but only deeper systems (${\geq}1.5\;km$) are exclusively gold-rich.

• Journal of the Korean Chemical Society
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• v.29 no.4
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• pp.426-436
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• 1985

Preparative and kinetic photochemical reactions of several benzanilides were studied. Several substituted benzanilides were synthesized by acylation of substituted anilines with substituted benzoyl chlorides. While benzanilide gave a photo-Fries type reaction product, 2-chlorobenzaniline, 2-bromobenzanilide, and 2-methoxybenzanilide gave a photocyclization reaction product, phenanthridone. Since 8-chlorophenanthridone was obtained from 2,2'-dichlorobenzanilide, the carbonyl phenyl is the excited site. Quantum yield of photocyclization of 2-chlorobenzanilide, 2'-chlorobenzanilide, and 2-methoxybenzanilide were obtained. 2-Chlorobenzanilide was photocyclized effectively and 2'-chlorobenzanilide ineffectively. Since the oxygen present in the reaction medium retarded the photocyclization reaction of 2-chlorobenzanilide, the triplet state of 2-chlorobenzanilide is involved. The mechanism of the photocyclization of 2-chlorobenzanilide is suggested: $\pi-complex$ between carbonyl phenyl and N-phenyl was formed from the triplet state of 2-chlorobenzanilide; neighbour phenyl (N-phenyl) assists for leaving of chlorine from carbonyl phenyl to make an intermediate, cyclized conjugated radical, because electron donating group on the N-phenyl ring accelerated the reaction; hydrogen detachment from the intermediate is obviously not a rate determined step because there was no isotope effect on the rate of photocyclization. The photocyclization reaction rate of 2-methoxybenzanilide was faster in the presence of oxygen than in the absence of oxygen. Thus, the singlet excited state of 2-methoxybenzanilide is involved in the reaction. Probably, the intermediate, methoxyhydro-phenanthridone is oxidized by oxygen in the medium to give phenanthridone.

• Korean Journal of Food Science and Technology
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• v.44 no.4
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• pp.401-410
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• 2012

This study examines the authenticity discrimination of the circulated honey by using stable isotope ratio methods. In the case of domestic honey, the range of ${\delta}^{13}C$ for the samples labeled as pure honey was about -27- -21‰ at the $C_3$ origin, and the range of that for artificial honey was over -19‰ at the $C_4$ origin. The range of ${\delta}^{13}C$ for all imported honey was over -27- -23‰ originating from the $C_3$ plant. According to the nectar-source, ${\delta}^2H$ and ${\delta}^{18}O$ for domestic honey were significantly different for 6 and 5 groups, respectively. However, we could not explain the detailed relationship as well as the geographical feature of ${\delta}^2H$ and ${\delta}^{18}O$. The difference for ${\delta}^2H$ and ${\delta}^{18}O$ in the wide range of latitude, such as between Australia and Canada, was more or less shown. However, it was difficult to find out the trends of ${\delta}^2H$ and ${\delta}^{18}O$ for imported honey versus the geographical information in the similar latitudinal country.