• Economic and Environmental Geology
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• v.19 no.3
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• pp.199-218
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• 1986

Arsenopyrite in arsenic and polymetallic ores from calcic Fe-W skarn deposit of the Ulsan mine, Republic of Korea, has been investigated by means of electron microprobe analysis and X-ray diffractometry. As a result, it is revealed that the Ulsan arsenopyrite may be classified into the following three species with different generation on the basis of its mode of occurrence, chronological order during polymetallic mineralization and chemical composition; arsenopyrites I, II and III. 1) Arsenopyrite I-(Ni, Co)-bearing species belonging to the oldest generation, which has crystallized together with (Ni, Co)-arsenides and -sulpharsenides in the early stage of polymetallic mineralization. In rare cases, it contains a negligible amount of antimony. It occurs usually as discrete grains with irregular outline, showing rarely subhedral form, and is diffused in skarn zone. The maximum contents of nickel and cobalt are 10.04 Ni and 2.45 Co (in weight percent). Occasionally, it shows compositional zoning with narrow rim of lower (Ni+Co) content. 2) Arsenopyrite II-arsenian species, in which (Ni+Co) content is almost negligible, may occur widely in arsenic ores, and its crystallization has followed that of arsenopyrite I. It usually shows subhedral to euhedral form and is closely associated with $l{\ddot{o}}llingite$, bismuth, bismuthinite, chalcopyrite, sphalerite, bismuthian tennantite, etc. It is worthy of note that arsenopyrite II occasionally contains particles consisting of both bismuth and bismuthinite. 3) Arsenopyrite III-(Ni, Co)-free, S-excess and As-deficient species is close to the stoichiometric composition, FeAsS. It occurs in late hydrothermal veins, which cut clearly the Fe-W ore pipe and the surrounding skarn zone. It shows euhedral to subhedral form, being extremely coarse-grained, and is closely associated with pyrite, "primary" monoclinic pyrrhotite, galena, sphalerite, etc. Among three species of the Ulsan arsenopyrite, arsenopyrite I does not serve as a geothermometer, because (Ni+Co) content always exceeds 1 weight percent. In spite of the absence of Fe-S minerals as sulphur-buffer assemblage, the presence of $Bi(l)-Bi_2S_3$ sulphur-buffer enables arsenopyrite II to apply successfully to the estimation of either temperature and sulphur fugacity, the results are, $T=460{\sim}470^{\circ}C$, and log $f(S_2)=-7.4{\sim}7.0$. With reference to arsenopyrite III, only arsenopyrite coexisting with pyrite and "primary" monoclinic pyrrhotite may serve to restrict the range of both temperature and sulphur fugacity, $T=320{\sim}440^{\circ}C$, log $f(S_2)=-9.0{\sim}7.0$. These temperature data are consistent with those obtained by fluid inclusion geothermometry on late grandite garnet somewhat earlier than arsenopyrite II. At the beginning of this paper, the geological environments of the ore formation at Ulsan are considered from regional and local geologic settings, and physicochemical conditions are suspected, in particular the formation pressure (lithostatic pressure) is assumed to be 0.5kb (50MPa). The present study on arsenopyrite geothermometry, however, does not bring about any contradictions against the above premises. Thus, the following genetical view on the Ulsan ore deposit previously advocated by two of the present authors (Choi and Imai) becomes more evident; the ore deposit was formed at shallow depth and relatively high-temperature with steep geothermal gradient-xenothermal conditions.

• Economic and Environmental Geology
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• v.15 no.3
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• pp.123-154
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• 1982

Petrochemical, K-Ar dating, Sand Rb/Sr isotopes, metallogenic zoning, paleomagnetic and geotectonic studies of the Gyongsang basin were carried out to examine applicability of plate tectonics to the post-late Cretaceous igneous activity and metallogeny in the southeastern part of Korean Peninsula. The results obtained are as follows: 1. Bulgugsa granitic rocks range from granite to adamellite, whose Q-Ab-Or triangular diagram indicates that the depth and pressure at which the magma consolidated increase from coast to inland varying from 6 km, 0.5-3.3 kb in the coastal area to 17 km, 0.5-10 kb in the inland area. 2. The volcanic rocks in Gyongsang basin range from andesitic to basaltic rocks, and the basaltic rocks are generally tholeiitic in the coastal area and alkali basalt in the inland area. 3. The volcanic rocks of the area have the initial ratio of Sr^{87}/Sr^{86} varying from 0.706 to 0.707 which suggests a continental origin; the ratio of Rb/Sr changing from 0.079-0.157 in the coastal area to 0.021-0.034 in the inland area suggests that the volcanism is getting younger toward coastal side, which may indicate a retreat in stage of differentiation if they were derived from a same magma. The K_2O/SiO_2 (60%) increases from about 1.0 in the coastal area to about 3.0 in the inland area, which may suggest an increase indepth of the Benioff zone, if existed, toward inland side. 4. The K-Ar ages of volcanic rocks were measured to be 79.4 m.y. near Daegu, and 61.7 m.y. near Busan indicating a southeastward decrease in age. The ages of plutonic rocks also decrease toward the same direction with 73 m.y. near Daegu, and 58 m.y. near Busan, so that the volcanism predated the plutonism by 6 m.y. in the continental interior and 4 m.y. along the coast. Such igneous activities provide a positive evidence for an applicability of plate tectonics to this area. 5. Sulfur isotope analyses of sulfide minerals from 8 mines revealed that these deposits were genetically connected with the spacially associated ingeous rocks showing relatively narrow range of ${\delta}^{34}S$ values (-0.9‰ to +7.5‰ except for +13.3 from Mulgum Mine). A sequence of metallogenic zones from the coast to the inland is delineated to be in the order of Fe-Cu zone, Cu-Pb-Zn zone, and W-Mo zone. A few porphyry type copper deposits are found in the Fe-Cu zone. These two facts enable the sequence to be comparable with that of Andean type in South America. 6. The VGP's of Cretaceous and post Cretaceous rocks from Korea are located near the ones($71^{\circ}N$, $180^{\circ}E$ and $90^{\circ}N$, $110^{\circ}E$) obtained from continents of northern hemisphere. This suggests that the Korean peninsula has been stable tectonically since Cretaceous, belonging to the Eurasian continent. 7. Different polar wandering path between Korean peninsula and Japanese islands delineates that there has been some relative movement between them. 8. The variational feature of declination of NRM toward northwestern inland side from southeastern extremity of Korean peninsula suggests that the age of rocks becomes older toward inland side. 9. The geological structure(mainly faults) and trends of lineaments interpreted from the Landsat imagery reveal that NNE-, NWW- and NEE-trends are predominant in the decreasing order of intensity. 10. The NNE-trending structures were originated by tensional and/or compressional forces, the directions of which were parallel and perpendicular respectively to the subduction boundary of the Kula plate during about 90 m.y. B.P. The NWW-trending structures were originated as shear fractures by the same compressional forces. The NEE-trending structures are considered to be priginated as tension fractures parallel to the subduction boundary of the Kula plate during about 70 m.y. B.P. when Japanese islands had drifted toward southeast leaving the Sea of Japan behind. It was clearly demonstrated by many authors that the drifting of Japanese islands was accompanied with a rotational movement of a clock-wise direction, so that it is inferred that subduction boundary had changed from NNE- to NEE-direction. A number of facts and features mentioned above provide a suite of positive evidences enabling application of plate tectonics to the late Cretaceous-early Tertiary igneous activity and metallogeny in the area. Synthesizing these facts, an arc-trench system of continental margin-type is adopted by reconstructing paleogeographic models for the evolution of Korean peninsula and Japan islands. The models involve an extention mechanism behind the are(proto-Japan), by which proto-Japan as of northeastern continuation of Gyongsang zone has been drifted rotationally toward southeast. The zone of igneous activity has also been migrated from the inland in late-Cretaceous to the peninsula margin and southwestern Japan in Tertiary.

• Economic and Environmental Geology
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• v.19 no.1
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• pp.67-83
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• 1986

Oriented hand samples were collected from Gobangsan Formation and Nogam Formation in the north of Danyang and south of Yeongchun, from Bansong Group in and around Danyang, from Nampo Group in Chungnam Coalfield, from Gyeongsang Supergroup distributed from Waegwan through Daegu to Gyeongsan and from Daegu to Goryong, and from volcanic flows in Jeongog area and Jeju Island to study the paleomagnetism of southern Korea since Permian. Stepwise alternating field and thermal demagnetization experiments were carried out to determine optimum fields and temperatures. Observed mean paleomagnetic directions are as follows: $D=331.5^{\circ}$, $I=25.1^{\circ}$, $a95=12.8^{\circ}$ for Permian, $D=325.6^{\circ}$, $I=46.1^{\circ}$, $a95=11.8^{\circ}$ for Triassic, $D=313.4^{\circ}$, $I=43.1^{\circ}$, $a95=16.0^{\circ}$ for early Jurassic, $D=41.3^{\circ}$, $I=64.6^{\circ}$, $a95=4.5^{\circ}$ for early Cretaceous, $D=28.3^{\circ}$, $I=58.1^{\circ}$, $a95=2.3^{\circ}$ for late Cretaceous, $D=2.0^{\circ}$, $I=55.8^{\circ}$, $a95=6.6^{\circ}$for Quaternary. To describe the tectonic translocation of southern Korean block, northern Eurasian continental block was used as a reference frame. For each age since Permian the expected northern Eurasian field directions in terms of paleolatitude and declination were calculated. The paleolatitudes of Permian ($13.2^{\circ}N$) and early Jurassic ($25.1^{\circ}N$) obtained from the study area are quite different from those of Permian ($66.0^{\circ}N$) and early Jurassic ($68.1^{\circ}N$) which are expected for northern Eurasia. The declinations of Permian ($331.5^{\circ}$) and early Jurassic ($313.4^{\circ}$) are also quite different from those of the Permian ($56.6^{\circ}$) and the early Jurassic ($47.5^{\circ}$) expected for northern Eurasia. The Cretaceous paleolatitude is similar to the expected within error limit, but the declination for the same period is significantly different from that of the expected for the northern Eurasia. From the above evidences it is suggested that the south Korean land mass had moved from low latitude in Permian to north and sutured to northern continental block since early Jurassic. The relative rotations of early Cretaceous($27.4^{\circ}$) and late Cretaceous($10.8^{\circ}$) to northern Eurasian continent reveal that the Korean land mass might be rotated clockwise in two different times, probably in late Early Cretaceous and in Tertiary.

• Economic and Environmental Geology
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• v.24 no.2
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• pp.131-150
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• 1991

The Weolseong diatreme was temporally and spatially related to the intrusion of the Gadaeri granite, and was -mineralized by meteoric aqueous fluids. In the Nokdong As-Zn deposit, pyrite, aresenopyrite and sphalerite are the most abundant sulfide minerals. They are associated with minor amount of magnetite, pyrrhotite, chalcopyrite and cassiterite, and trace amounts of Pb-Sb-Bi-Ag sulphosalts. The AsZn ore probably occurred at about $350^{\circ}C$ according to fluid inclusion and compositional data estimated from the arsenic content of arsenopyrite and iron content of sphalerite intergrown with pyrrhotite + chalcopyrite + cubanite. Heating studies of fluid inclusions in quartz indicate a temperature range between 180 and $360^{\circ}C$, and freezing data indicate a salinity range from 0.8 to 4.1 eq.wt % NaCl. The coexisting assemblage pyrite + pyrrhotite + arsenopyrite suggests that $H_2S$ was the dominate reduced sulfur species, and defines fluid parameter thus: $10^{-34.5}$ < ${\alpha}_{S_2}$ < $10^{-33}$, $10^{-11}$ < $f_{S_2}$ < $10^{-8}$, -2.4 < ${\alpha}_{S_2}$ < -1.6 atm and pH= 5.2 (sericte stable) at $300^{\circ}C$. The sulfur isotope values ranged from 1.8 to 5.5% and indicate that the sulfur in the sulfides is of magmatic in origin. The carbon isotope values range from -7.8 to -11.6%, and the oxygen isotope values from the carbonates in mineralized wall rock range from 2 to 11.4%. The oxygen isotope compositions of water coexisting with calcite require an input of meteoric water. The geochemical data indicate that the ore-forming fluid probably was generated by a variety of mechanisms, including deep circulation of meteoric water driven by magmatic heat, with possible input of magniatic water and ore component.

• Economic and Environmental Geology
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• v.44 no.4
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• pp.313-320
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• 2011

The Taebaegsan Mineralized District is the most prospective region for the useful mineral commodities such as a coal, non-metallic, metallic mineral in South Korea. From a general point of view, Cambro- Ordovician limestone formations, Myobong slate and Pungchon (Daegi) limestone, are the most fertilizable formations in the Taebaegsan Mineralized District. The geology around Weondong mine area consists mainly of Carboniferous-Triassic formations and Cambro-Ordovician formations intruded by rhyolite/quartz porphyry. The great overthrusted fault of N40~$50^{\circ}E$ direction, so called Weondong overthrust fault, is observed in the central part of the mine area and the NS fault system cuts the overthrusted fault. By postulating from the favorable geological and structural condition around Weondong area, the possibility of deep seated hidden ore bodies is expected. In 2010, on the basis of the results of LOTEM and CSAMT survey, the cross-hole survey was performed for the investigation of the hidden polymetallic ore body in the deep parts of the Weondong mine area and the grade of the newly-discovered orebody is as follows; (1) The cut-off grade for lead-zinc 3%; an weighted average grade 5.50% (2.7 m), (2) The cutoff grade for copper 0.1%; an weighted average grade 0.91% (14.65 m), (3) The cut-off grade for iron 30%; an weighted average grade 38.18% (3.3 m), (4) $WO_3$ for each cut-off grade(0.01%, 0.05%, 0.1%); an weighted average grade 0.29 wt. % (8.8 m), 1.15 wt. % (2.1 m), 1.97 wt. % (1.2 m), (5) $MoS_2$ for each cut-off grade(0.01%, 0.1%); an weighted average grade 0.15 wt. % (6.3S m), 0.28 wt. % (3.15 m), (6) $Ta_2O_5$ for each cut-off grade (0.01%, 0.1%); an weighted average grade 0.13% (19.S m), 1.11% (1.8 m), (7) $Nb_2O_5$ for each cut-offgrade (0.01%, 0.1%); an weighted average grade 0.06% 11.5 m), 0.15% (3.0 m).

• Economic and Environmental Geology
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• v.44 no.4
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• pp.273-288
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• 2011

Chon-Ashuu copper mining claim area is located, in terms of the geotectonic setting, in the northern part of the suture line which is bounded with the marginal part of Issik-kul micro-continent on the southern part of North Tien-Shan terrane. The geological blocks of Chon-Ashuu districts belong to the southern tip of Kazakhstan orocline. The rock formation of this area are composed of the continental crust or/and arc collage and the paleo-continental fragments-accretionary wedge complex of pre-Altaid orogenic materials. ASI(Alumina Saturation Index) of Paleozoic plutonic rocks in Chon-Ashuu area belong to the peraluminous and metaluminous rocks which were generated from fractional crystallization of Island and volcanic arc crusts in syn-post collisional plate. The geology of the ChonAshuu area consists of upper Proterozoic and Paleozoic rock formations. According to Harker variation diagrams for Chon-Ashuu arenaceous sedimentary rocks, the silty sandstone of Chon-Ashuu area showing the mineralogical immaturity were derived from Island arc or the marginal environments of active continent in Cambro-Carboniferous period. Numerous intrusive rocks of Chon-Ashuu area are distributed along north east trending tectonic structures and are bounded on four sides by the conjugate pattern. The most common type of the plutonic rocks are granodiorite and monzodiorite. According to the molecular normative An-Ab-Or composition (Barker, 1979), the plutonic rocks in Chon-Ashuu area are classified into tonalite - trondhjemite - granodiorite (TTG) series which are an aggregation of rocks which is the country rock of copper mineralization, that are formed by melting of hydrous mafic crust at high pressure.

• Economic and Environmental Geology
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• v.44 no.5
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• pp.399-412
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• 2011

A DEM (digital elevation model) is produced using a digital topographic map and is now a commonly used tool in geologic surveys. This study aimed to clarify the relationship between knickpoints and faults in the Namdae stream by analyzing a DEM of the area. The Namdae drainage basin was divided into three subbasins (S1, S2 and S3) and their knickpoints developed for the middle to mid-upper regions were extracted from the DEM. The relative steepness Ks and concavity depending on the incision rate was higher in S1 than in S2 and S3 regions. We assumed that the incision rate caused by active erosion resulted from several faults crossing the basins rather than differences in rock types. There are 77 knickpoints in the Namdae drainage area, including the low-ranking branch, and 24 of thses are on the main river system (S1, S2, S3). Of these 77 knickpoints, 27 (38%) are matched by faults, and from the three basins, 13 (54%) correspond with faults, indicating that the knickpoints are connected closely with the faults. For example the average Ks (relative steepness), was 38.8, but in the overlapping area of the Samdang and Doocheon faults the Ks value was 42.99~43.39. We suggest that the faults resulted in geomorphic deformation such as the high-Ksn knickpoints. There was little evdence of relationship between the knickpoints and rock boundaries, with 54% of the knickpoints distributed on the S1, S2, and S3 subbasins. We concluded that the drainage basin knickpoints are the result of fault movement and are a type of geomorphologic deformation that could be useful for surveying Quaternary faults or fault extension.

• Economic and Environmental Geology
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• v.42 no.4
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• pp.289-300
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• 2009

The Geodo mine area, had been developed for Fe and Cu ores since 1963 and abandoned in recent decades, is located in the central part of the Taebaeksan mineralized district. This area comprises of the Jangsan, Myobong, Pungchon, Hwajeol, Dongjeom, and Dumugol Formations in ascending stratigraphic order. These Formations were intruded by the Cretaceous Eopyeong granitoids that appears to produce the Geodo skarn. Their compositions are relatively oxidized quartz monzodiorite to granodiorite (magnetite series, $Fe_2O_3/FeO=0.3{\sim}1.1$). Mineralizations related skarn deposit occur in the Myobong, Pungchon, and Hwajeol Formations. The proximal skarn is zoned from andraditic garnet ($Ad_{44-95}Gr_{1-53}$) predominant adjacent to the Eopyeong granitoids to diopsidic pyroxene ($Hd_{10-100}Di_{0-89}$) predominant away from the one. The differential proportion of garnet and pyroxene is generated by water/rock ratio and their source, such as magmatic and meteoric water. This is useful tool for assessment the overall oxidation state of the entire skarn system. Gold occurs in proximal red to brownish garnet skarn, and genetically associated with Bi- and Te-bearing minerals. Skarn deposit developed in the Geodo mine area is considered as oxidized Au skarn category, based on chemical composition of the Eopyeong granitoids, zonation of skarn, and gold occurrences. Garnet-rich skarn zone will be the main target for exploration of gold in the study area. However, it is needed to the detailed survey on vertical zonation of this area as well as lateral zonation. The result of this survey would provide an important basis for the exploration of the skarn Au deposit in the Geodo mine area.

• Economic and Environmental Geology
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• v.51 no.4
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• pp.309-322
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• 2018

Naturally occurring asbestos (NOA) occurs in rocks and soils as a result of natural weathering and human activities. It is proved that inhalation of asbestos fibers can lead to increase risk of developing several diseases such as lung cancer and malignant mesothelioma. The parent rocks of asbestos have been mainly associated with (ultra)mafic and carbonate rock. The previous studies on NOA were mainly limited to (ultra)mafic rock-hosted asbestos, but studies on carbonate rock-hosted asbestos are relatively rare in S. Korea. Therefore, this study was aimed to examine mineralogical characteristics of carbonate rock-hosted NOA at three sites including Muju and Jangsu, Jeonbuk province and Asan, Chungnam province. Types of rocks at the three sites mainly consisted of Precambrian metasedimentary rocks, carbonate rock, and Cretaceous and Jurassic granites. Asbestos-containing carbonate rock samples were obtained for mineralogical characterization. XRD, PLM, EPMA, SEM and EDS analyses were used to characterize mineralogical characteristics of the carbonate rock-hosted NOA. From the carbonate rock, fibrous minerals were occurred acicular and columnar forms in the three sites. Fibrous minerals were composed of mainly tremolite and associated minerals included possibly asbestos containing materials (ACM) such as talc, vermiculite, and sepiolite. The length and aspect ratios of tremolite were similar to the standard asbestiform (length >$5{\mu}m$, length:width = 3:1). These results indicate that both non-asbestiform and asbestiform tremolite with acicular forms occurred in carbonate rocks at three sites. Geological and geochemical characteristics and mineral assemblages indicate tremolite and associated minerals might be formed by hydrothermal alternation and/or hydrothermal veins of carbonate rocks due to intrusion of acidic igneous rocks.

• Korean Journal of Environmental Agriculture
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• v.25 no.2
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• pp.138-146
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• 2006

To understand the status of water quality and work out a suitable countermeasures in Seonakdong watershed which has poor agro- environmental condition because of severe point and non-point source pollution by popularized city and near sea, we investigated the pollution sources and water quality from '03 and '05 and the result were mapped with GIS and RS for end-users's convenient comprehense and conjunction of water quality and geological data. The most degraded tributary was Hogeo stream which was affected directly by highly popularized Gimhae city, the main pollution source of the watershed. The pollution of tributaries in watershed increased the T-N of main body that reached over 4 mg/L during dry season. Pyeonggang stream and the lower part of main water way were suffered from high salt contents induced near sea and the EC value of those area were increased to 2.25 dS/m. The delivered loads of T-N and T-P were largest in Joman river as 56% and 61% of total delivered loads 1mm tributaries because of lots of stream flow. When Management mandate for irrigation water in Seonakdong river watershed was mapped for estimating integrated water quality as the basis of classification of EC and T-N contents in water, Hogeo and Shineo catchments were showed the requiring countermeasures none against nutrients hazard and Pyeonggang catchment was the vulnerable zone against nutrients and salts hazard. As the result, Seonakdong watershed had very various status of water quality by characteristics of catchments and countermeasures for improving water quality and crop productivity safely should changed depend on that.