• Economic and Environmental Geology
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• v.26 no.2
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• pp.117-127
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• 1993

Ag-Au vein ores from the Weolyu mine, Youngdong district, contain significant germanium (up to 145g/t, average 34.9g/t), in the form of argyrodite ($Ag_8GeS_6$). Mineral chemistries of argyrodite and its associated minerals were determined by electron probe microanalysis. Twenty eight elements in thirteen ore samples were analyzed using an ICP mass spectrometer. Argyrodite occurs in the paragenetically later mineral assemblage consisting of carbonates+quartz+native silver+argentite+Ag-sulfosalts, indicating that the germanium mineralization represents the culmination of a complex mineral sequence which includes early gold and late silver deposition. The mean formula of the argyrodite is $Ag_{7.90}\;(Ge_{0.76}Sn_{0.04})S_6$, with minor amounts of Cu, Fe, Sb, As, Sn, and Zn. The Weolyu argyrodite shows systematic substitutions of Ag by Cu, and of Ge by Sb. Chemical analyses of vein ores indicate that metals were precipitated in the order of $Fe{\rightarrow}Pb$, $Zn{\rightarrow}Cu{\rightarrow}Ag$, Sb, As, Ge. Germanium has a strong geochemical affmity with As and Sb, and Cu, Pb, Zn, Mo, and Sr show weak positive correlations with Ge. Germanium deposition at Weolyu was mainly a result of cooling of hydrothermal fluids (down to $175^{\circ}C{\sim}210^{\circ}C$, due to increasing involvement of cooler meteoric waters in the epithermal system.

• Journal of the Mineralogical Society of Korea
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• v.31 no.3
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• pp.137-147
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• 2018

The aim of this study was to leach penalty elements, such as Bi and As, effectively through microwave leaching of a gold concentrate sample containing penalty elements with nitric acid solution. For this purpose, the time effect of microwave leaching, nitric acid concentration effect, and sample addition effect in a microwave were examined. The experiment, demonstrated that the leaching rate of penalty elements increased as microwave leaching time and nitric acid concentration increased and concentration addition decreased. When a microwave heating experiment was carried out on the concentrate and ore minerals, Bi was removed by as much as 90%, and the phase of arsenopyrite was transformed in the order of arsenopyrite (FeAsS), pyrrhotite (FeS), and hematite ($Fe_2O_3$). When the X-ray diffraction (XRD) analysis was carried out with solid residue, elemental sulfur and anglesite were identified. The intensity of the XRD peaks of elemental sulfur and anglesite increased, and the peaks were sharper when the microwave leaching time was 12 min instead of 1 min, the nitric acid concentration was 4 M in rather than 0.5 M, and the concentration addition was 30 g rather than 5 g. This was probably because more elemental sulfur and anglesite were generated in the leaching solution as the leaching efficiency increased. Bi can be leached as valuable elements in the leaching solution through microwave leaching processes while they are released to the environment through a microwave heating processes.

• Geosciences Journal
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• v.22 no.6
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• pp.881-889
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• 2018

The Geodo skarn deposit is located in the Taebaeksan Basin, central eastern Korean Peninsula. The geology of the deposit consists of Cambrian to Ordovician calcareous sedimentary rocks and the Cretaceous Eopyeong granitoids. The skarns at Geodo occur around the Eopyeong granitoids, which consist, from early to late, of magnetite-bearing equigranular quartz monzodiorite, granodiorite, and dykes. These dykes emanated randomly from equigranular granodiorite and some of dykes spatially accompany skarns. Skarn Fe mineralization, referred as Prospect I and II in this study, is newly discovered beyond previously known skarns adjacent to the quartz monzodiorite. These discoveries show a vertical and lateral variation of skarn facies, grading from massive reddish-brown garnet-quartz in a lower and proximal zone to banded in an upper and distal zone, reflecting changes in lithofacies of the host rocks. Skarn veins in distal locations are parallel to sedimentary laminae, suggesting that lithologic control is important although proximal skarn has totally obliterated primary structures, due to intense retrograde alteration. Skarns at Geodo are systematically zoned relative to the causative dykes. Skarn zonation comprises proximal garnet, distal pyroxene, and vesuvianite (only in Prospect I) at the contact between skarn and marble. Retrograde alteration is intensely developed adjacent to the contact with dykes and occurs as modification of the pre-existing assemblages and progressive destruction such as brecciation of the prograde assemblages. The retrograde alteration assemblages consist predominantly of epidote, K-feldspar, amphibole, chlorite, and calcite. Most of the magnetite (the main ore mineral), replaces calc-silicate minerals such as garnet in the lower proximal exoskarn, whereas it occurs massive in distal pyroxene and amphibole in the upper and distal exoskarn. The emanation of dykes from the equigranular granodiorite has provided channelways for ascent of skarn-forming fluids from a deep source, whereas the style and nature of skarns suggest that originally structurally-controlled skarn-forming fluids may migrate long distances laterally to produce skarn in calcareous sedimentary rocks.

• Geophysics and Geophysical Exploration
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• v.24 no.3
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• pp.73-77
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• 2021

Induced polarization (IP) is useful for mineral exploration and hydrogeological studies by visualizing the electrochemical reactions at the interface between polarized minerals and groundwater. Frequency-domain IP (FDIP) is not actively applied to field surveys because it takes longer to acquire data, despite its higher data quality than conventional time-domain IP. However, data quality is more important in current mineral exploration as the targets gradually shift to deep or low-grade ore bodies. In addition, the measurement time reduced by automated instrumentation increases the potential for FDIP field applications. Therefore, we demonstrate that FDIP can detect mineral exploration targets by performing geophysical logging in the boreholes of a skarn deposit, in South Korea. Alternating current (AC) resistivity, percent frequency effect (PFE) and metal factor (MF) were calculated from impedance values obtained at two different frequencies. Skarn zones containing magnetite or pyrite showed relatively low AC resistivity, high PFE, and high MF compared to other zones. Therefore, FDIP surveys are considered to be useful for mineral exploration.

• Resources Recycling
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• v.31 no.2
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• pp.3-11
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• 2022

Owing to the global development of high-strength alloys and renewable energy industries, the demand for vanadium, a key raw material in these industries, is expected to increase. Until now, vanadium has been recovered as a by-product of the industry, but interest in its direct recovery from minerals has increasing with its significantly increasing demand. In particular, the recovery of vanadium from stone coal ore and vanadium titano-magnetite (VTM) containing vanadium has been actively researched in China, which has the largest reserves and production of vanadium in the world. In Korea, a large amount of VTM also occurs in the northern part of Gyeonggi-do, and fundamental research and technical development is being conducted to recover vanadium. It is necessary to understand the current status of the separation technology used worldwide to satisfy the demand for metals such as vanadium, which currently depends on imports.

• Economic and Environmental Geology
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• v.55 no.1
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• pp.53-61
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• 2022

The Gasado Au-Ag deposit is located within the south-western margin of the Hanam-Jindo basin. The geology of the Gasado is composed of the late Cretaceous volcaniclastic sedimentary rocks and acidic or intermediate igneous rocks. Within the deposit area, there are a number of hydrothermal quartz and calcite veins, formed by narrow open space filling along subparallel fractures in the late Cretaceous volcaniclastic sedimentary rock. Vein mineralization at the Gasado is characterized by several textural varieties such as chalcedony, drusy, comb, bladed, crustiform and colloform. The textures have been used as exploring indicators of the epithermal deposit. Mineral paragenesis can be divided into two stages (stage I, ore-bearing quartz veins; stage II, barren carbonate veins) considering major tectonic fracturing event. Stage I, at which the precipitation of Au-Ag bearing minerals occurred, is further divided into three substages (early, middle and late) with paragenetic time based on minor fractures and discernible mineral assemblages: early, marked by deposition of pyrite and pyrrhotite with minor chalcopyrite, sphalerite and electrum; middle, characterized by introduction of electrum and base-metal sulfides with minor argentite; late, marked by argentite and native silver. Au-Ag-bearing mineralization at the Gasado deposit occurred under the condition between initial high temperatures (≥290℃) and later lower temperatures (≤130℃). Changes in stage I vein mineralogy reflect decreasing temperature and fugacity of sulfur (≈10^-10.1 to ≤10^-18.5atm) by evolution of the Gasado hydrothermal system with increasing paragenetic time. The Gasado deposit may represents an epithermal gold-silver deposit which was formed near paleo-surface.

• Economic and Environmental Geology
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• v.55 no.5
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• pp.465-475
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• 2022

The seafloor massive sulfide deposits are important mineral resources for base and precious metals, and their ore genesis and metal contents are mainly controlled by wall-rock leaching process and/or magmatic volatile input from the underlying magma chamber. However, the contribution of two different metal sources to the seafloor hydrothermal mineralization significantly varies in diverse geological settings and thus still remains controversial. In this review, mineralogical and geochemical characteristics of SMS deposits from mid-ocean ridges (MORs) and volcanic arcs were investigated to understand the contribution from different metal sources and to suggest future challenges that need to be addressed. As a result, the genetic occurrences of enargite and cubanite, galena and barite indicate the effects of magmatic input and water-rock interaction, respectively. Also, the distributional behaviors of Co, As, and Hg in pyrite and FeS content of sphalerite could be useful empirical indicators to discriminate the significant roles of different metal sources between MOR and Arc settings. To date, as most studies have focused on sulfide samples recovered from the seabed, further studies on magmatic sulfides and sulfate minerals are required to fully understand the genetic history of SMS deposits.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.475-499
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• 2023

To infer the provenance of raw iron materials utilized in iron production at the archaeological sites in Gyeongsang province, petrographic and geochemical analyses were conducted for smelting samples and major iron ores sourced from ore deposits. The smelting samples excavated from various iron archaeological sites were classified into different types according to their refining processes, such as iron bloom, iron bloom slag, pig iron, pig iron slag, forging iron flake, smithery iron, iron flake, and arrowhead. These samples exhibited discernable differences in their mineralogical components and texture. The enrichments of major elements such as aluminum and calcium in silicate minerals of the residual slags and the high contents of trace elements such as nickel and copper in some iron-making relics reflect the characteristics of raw iron ores, and thus can be regarded as potential indicators for inferring the provenance of source materials. In particular, the compositional ranges of Pb-Sr isotope ratios for the iron smelting samples were classified into three categories: 1) those exhibiting similar ratios to those of the raw iron ores, 2) those enriched in strontium isotope ratio, and 3) those enriched in both lead and strontium isotope ratios. The observed distinct Pb-Sr isotope characteristics in the iron smelting samples suggest the potential contribution of specific additives being introduced during the high-temperature refining process. These results provide a new perspective on the interpretation of the provenance study of the iron archaeological samples in Gyeongsang province, particularly in terms of the potential contribution of additives on the refining process.

• Journal of the Korean earth science society
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• v.43 no.6
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• pp.749-761
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• 2022

As the number of National and UNESCO Global Geoparks has increased, awareness of geological heritage and local government interests have also increased. In this study, data from the geological heritage sites in the Ulsan area were summarized, a practical use plan for geological heritage was prepared based on the assessment results, and the expected effects were also presented. The value for 33 of 112 geological heritage sites identified through literature surveys was evaluated. In terms of the geological heritage types in Ulsan, there were two geological, one geomorphological, and thirty mixed-heritage sites. In the context of the geological heritage of Ulsan, rivers and coastal topography were found to be dominant, and various geomorphological and geological features, such as fossils, folds, faults, shear zones, minerals, and ore deposits are included. Based on the assessment results, there were three, eighteen, nine, and three sites in Classes I, II, III, and IV, respectively. Considering the intrinsic and subsidiary values of geological heritage, the Gangdong Coast, Jujeon Coast, Taehwagang area, Daewangam area, the Daegokri-Cheonjeonri track sites, and Mujechineup are likely to be listed as potential geosites. When the endorsement of the geopark has been promoted alongside these geosites, it can contribute to the sustainable preservation and maintenance of the geosites, satisfy the demand for science education through geo-education, and support the sustainable development of the local economy following the detailed standards for geopark certification in the Natural Parks Act. This is expected to increase the brand value of Ulsan Metropolitan City.

• Economic and Environmental Geology
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• v.45 no.4
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• pp.385-396
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• 2012

The geochemical high-grade uranium anormal zone has been reported in the Shinbo mine and its eastern areas, Jinan-gun, Jeollabuk-do located in the southwestern part of Ogcheon metamorphic zone, Korea. In this paper is reported the time-relationship between deformation and growth of metamorphic minerals in the eastern area of Shinbo mine, which consists of the Precambrian metasedimentary rocks (quartzite, metapelite, metapsammite) and the age-unknown pegmatite and Cretaceous porphyry which intrude them, and is considered the relative mineralization time on the basis of the previous research's result. The D1 deformation formed the straight-type Si internal foliation which is defined mainly as the arrangement of elongate quartz, biotite, opaque mineral in andalusite porphyroblast. The D2 deformation, which is defined by the microfolding of Si foliation, formed S2 crenulation cleavage. It can be divided into two sub-phases, early crenulation and late crenulation. The former occurs as the curvetype Si foliation in the mantle part of andalusite. The latter occurs as S1-2 composite foliation which warps around the andalusite. The andalusite porphyroblast began to grow under non-deformation condition after the formation of S1 foliation which corresponds to the straight-type Si foliation. It continued to grow before the late crenulation phase. The age-unknown pegmatite intruded after the D2 deformation and grew the fibrous sillimanite which random masks the S1-2 composite foliation. The D3 deformation formed F3 fold which folded the S1-2 composite foliation, D2 crenulation, fibrous sillimanite. It means that the intrusion of pegmatite related to the growth of the fibrous sillimanite took place during the inter-tectonic phase of D2 and D3 deformations. The retrograde metamorphism is recognized by the chloritization of biotite and two-way cleavage lamellae which is parallel to the S1-2 composite foliation and the F3 fold axial surface in the andalusite porphyroblast. It occurred during the D2 late crenulation phase and D3 deformation. In considering of the previous research's result inferring the most likely candidate for the uranium source rock as pegamatite, it indicates that the age-unknown pegmatite intruded during the inter-tectonic phase of D2 and D3 deformations, i.e. during the retrograde metamorphism related to the uplifting of crust, and formed the uranium ore zone around the Shinbo mine.