• Economic and Environmental Geology
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• v.48 no.2
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• pp.103-114
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• 2015

Jinsan gold deposit is a hydrothermal vein type deposit consisting of several fissure filling quartz veins developed within the Changri Formation of the Ogcheon Supergroup in Geumsan, Chungnam. This study is to provide an efficient exploration and development strategies based on the characteristics of the geology, geological structure, core logging, and ore vein occurrence and grade for the four pits (New pit, Main pit, Yanghapan pit and Teugho pit). Quartz veins are mostly developed with the strike of $N10^{\circ}-25^{\circ}W$ and $N5^{\circ}-20^{\circ}E$, and the thickness is in the range of 0.1~0.5 m, sometimes extending to over 1m. Although the quartz veins commonly form massive shape, they sometimes show zonal structure, comb structure as well as brecciated texture. Major ore minerals are pyrite and chalcopyrite, and pyrrhotite, sphalerite, galena, marcasite, electrum and chalcocite are also accompanied as minor phases. Gray and milky white quartz veins, which are occasionally crosscut by calcite vein, also include fluorite. Ore evaluations for the 22 samples revealed that the samples from the pits generally have very low Au contents, lower than 1 g/t, but some clay samples of drilled core show very high Au concentrations, up to 141 g/t, indicating that Au content is much higher within fault gouges rather than within fresh quartz veins. This may represent that gold might have been reworked and reprecipitated by hydrothermal fluids in association with reactivation of the faults, and thus suggest that ore occurrence in this deposit is very complex and irregular and therefore more precise and systematic exploration is required.

• Economic and Environmental Geology
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• v.44 no.1
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• pp.21-35
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• 2011

Inorganic and organic geochemical characteristics of Devonian bitumen carbonates in Alberta were studied using two drilling cores, Saleski 03-34-88-20w4 and Saleski 08-01-88-20w4, taken from the Core Research Center of Canada. The results of elements analyses showed high Total Inorganic Carbon, low Total Nitrogen and Total Sulfur, and Rock-Eval pyrolysis showed double $CO_2$ peaks in the oxidation part. These mean that the Devonian bitumen carbonates are mainly composed of dolomite formed by diagenesis, and its crystal texture is dominantly subhedral to anhedral but often euhedral. Bitumen contents were 3.6~19.0% in Saleski 3-34-88-20w4 and 5.0~16.4% in Saleski 08-01-88-20w4, respectively. As samples color become dark, bitumen and Total Organic Carbon contents are generally increasing in two cores. The results of biomarker analyses showed that the contents of resins and asphaltenes were 5~28% higher than those of saturated hydrocarbon, interring that the bitumen has been heavily biodegradated. According to the results of carbon isotope analyses in each component of bitumen, asphaltenes had highest values and the others had constant values. However, their values were varied in the range of normal crude oil (-18~-30‰).

• Economic and Environmental Geology
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• v.49 no.5
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• pp.349-360
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• 2016

This study determined mineralogical characteristics and discussed the meaning of mineralogical changes of the lower Choseon Supergrouop in the Weondong area based on the field geological investigation and the drilling core description using X-ray diffraction (XRD) mineral quantification and Scanning Electron Microscopy (SEM) observation. 100 samples with depth were collected from the core (250 m long) at a site in the study area. Especially, to investigate the changes from the upper Daegi Formation to the lower Hwajeol Formation, the samples were collected closely with the interval of about 0.3 m at this section. All samples were made into power using mortar for XRD. Mineral quantitative analysis was executed using Relative Intensity Ratio (RIR) method with corundum as an internal standard phase. Calcite, $2M_1$ illite and quartz are main constituents in most of samples. Dolomite and siderite are significantly observed in the Sesong Formation. As the results of quantitative analysis for the major minerals, the upper Daegi Formation is dominated by calcite with over 80%. The Sesong Formation includes high percentage of dolomite and siderite with the intercalation of thin layers containing high calcite and $2M_1$ illite contents. Hwajeol Formation is characterized by the alternation between thin layers of $2M_1$ illite and quartz-dominated layer (IQDL) and calcite-dominated layer (CDL). IQDL is more frequent in the lower part, whereas CDL is more common in the upper part. The boundary between Daegi Formation and the Sesong Formation is distinct, whereas the boundary between the Sesong Formation and the Hwajeol Formation tends to be changed gradually in mineralogy. The result of SEM observation shows that quartz and $2M_1$ illite are detrital, and a significant amount of calcite also shows detrital form with some recrystallized one, indicating that the repeated influx of terrestrial materials had changed the mineralogy of the shallow sea depositional environment in the early Paleozoic era.

• Economic and Environmental Geology
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• v.50 no.4
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• pp.303-311
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• 2017

The laboratory scale experiment was performed to evaluate the sealing capacity of the capping rock such as tuff and mudstone, measuring the intial supercritical $CO_2$ ($scCO_2$) injection pressure and the $scCO_2$-water-rock reaction for 90 days. The drilling cores sampled from 800 m in depth around the Janggi basin, Korea were used for the experiment. The mineralogical changes of mudstone and tuff were measured to evaluate the geochemical stability during the $scCO_2$-water-rock reaction at $CO_2$ storage condition (100 bar and $50^{\circ}C$). The rock core was fixed in the high pressurized stainless steel cell and was saturated with distilled water at 100 bar of pore water pressure. The effluent of the cell was connected to the large tank filled with 3 L of water and 2 L of $scCO_2$ at 100 bar, simulating the subsurface injection condition. The $scCO_2$ injection pressure, which was higher than 100 bar, was controlled at the influent port of the cell until the $scCO_2$ begin to penetrate into the rock and the initial injection pressure (> 100 bar) of $scCO_2$ into the rock was measured for each rock. The mineralogical compositions of mudstones after 90 days reaction were similar to those before the reaction, suggesting that the mudstone in the Janggi basin has remained relatively stable for the $scCO_2$ involved geochemical reaction. The initial $scCO_2$ injection pressure (${\Delta}P$) of a tuff in the Janggi basin was 15 bar and the continuous $scCO_2$ injection into the tuff core occurred at higher than 20 bar of injection pressure. For the mudstone in the Janggi basin, the initial $scCO_2$ injection pressure was higher than 150 bar (10 times higher than that of the tuff). From the results, the mudstone in Janggi basin was more suitable than the tuff to shield the $scCO_2$ leakage from the reservoir rock at subsurface.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.289-302
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• 2023

The study area was Gangnim-myeon, Hoengseong-gun, Gangwon-do, composed of the Chiaksan gneiss complex, and it was revealed that the concentrations of uranium (U) and thorium (Th) within the groundwater of the study area exceeded their water quality standards. Hence, artificial weathering experiments were conducted to elucidate mineralogically the mechanisms of their leaching using drilling cores obtained from the corresponding groundwater aquifers. First of all, the mineralogical compositions of core samples were observed, and the results indicated that the content of clinochlore, a member of the chlorite group of minerals that can form through low- and intermediate-temperature metamorphisms, was relatively higher. In addition, the Th concentration was measured ten times higher than that of U. The results of artificial weathering experiments suggested that the Th concentrations gradually increased through the dissolution of radioactive-element-bearing minerals up to the first day, and then they tended to decrease. It could be attributed to the fact that Th was leached with the dissolution of thorite, which might be a secondary mineral, and then dissolved Th was re-precipitated as the various forms of salt, such as sulfate. Even though the U content was lower than that of Th in the core samples, the U concentration was one hundred times higher than that of Th after the weathering experiments. It is likely caused by the gradual dissolution and desorption of U included in intensively weathered thorite or adsorbed as a form of UO₂²⁺ on the mineral surface. In addition, the leaching tendency of U and Th was positively correlated with the bicarbonate concentration. However, the concentrations between U and Th in groundwater exhibited a relatively lower correlation, which might result from the fact that they occurred from different sources, as aforementioned. Among various kinetic models, the parabolic diffusion and pseudo-second-order kinetic models were confirmed to best fit the dissolution kinetics of both elements. The period that would be taken for the U concentration to exceed its drinking-water standard was inferred using the regressed parameters of the best-fitted models, and the duration of 29.4 years was predicted in the neutral-pH aquifers with relatively higher concentrations of HCO₃, indicating that U could be relatively quickly leached out into groundwater.

• Economic and Environmental Geology
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• v.53 no.1
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• pp.23-32
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• 2020

Geological CO₂ sequestration is a global warming response technology to limit atmospheric emissions by injecting CO₂ captured on a large scale into deep geological formations. The presented results concern mineralogical and hydrogeological investigations (FE-SEM, XRD, XRF, and MICP) of mudstone samples from drilling cores of the Pohang basin, which is the research area for the first demonstration-scale CO₂ storage project in Korea. They aim to identify the mineral properties of the mudstone constituting the caprock and to quantitatively evaluate the hydrogeologic sealing capacity that directly affects the stability and reliability of geological CO₂ storage. Mineralogical analysis showed that the mudstone samples are mainly composed of quartz, K-feldspar, plagioclase and a small amount of pyrite, calcite, clay minerals, etc. Mercury intrusion capillary pressure analysis also showed that the samples generally had uniform particle configurations and pore distribution and there was no distinct correlation between the estimated porosity and air permeability. The allowable CO₂ column heights based on the estimated pore-entry pressures and breakthrough pressures were found to be significantly higher than the thickness of the targeting CO₂ injection layer. These results showed that the mudstone layers in the Yeongil group, Pohang basin, Korea have sufficient sealing capacity to suppress the leakage of CO₂ injected during the demonstration-scale CO₂ storage project. It should be noticed, however, that the applicability of results and analyses in this study is limited by the lack of available samples. For rigorous assessment of the sealing efficiency for geological CO₂ storage operations, significant efforts on collection and multi-aspect evaluation for core samples over entire caprock formations should be accompanied.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.143-159
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• 2024

Natural aggregate is an essential resource for human activities, closely related to construction. The aggregate demand has been increasing annually, and due to the nature of the resource, it is difficult to procure from distant locations. This study identifies the distribution and characteristics of aggregate-bearing areas as part of a municipal-level aggregate resource survey conducted in Nonsan City, Korea, in 2023. Nonsan City is located approximately 35 km straight distance from the Geum River estuary and lies at the passageway of the main stream of the Geum River. The topography of Nonsan City features eastern mountainous areas and western plains, creating an east-high-west-low geomorphic setting, with 33 streams distributed across the city, including tributaries of the Geum River like Nonsan Stream, Noseong Stream, and Ganggyeong Stream. All streams originate from the highlands in the north and east, converge with Nonsan Stream, and then join the west bank of the main stream of the Geum River at the western boundary of Nonsan City. Drilling core results show shallow depths in the highlands to the north and east, deepening towards the west, reaching a maximum depth of 25 m near the main stream of the Geum River. The total reserve of land aggregates is calculated to be 246,789,000 m³, with a developable amount of 172,750,000 m³. The total reserve of river aggregates is 5,236,000 m³, with a developable amount of 3,765,000 m³. The distribution of aggregates varies according to the geomorphic, geologic, and development pattern of the river system. Reserves are scarce in mountainous areas but are abundant in regions with rivers and wide alluvial plains, although reserves appear at depths greater than 4m. The distribution of aggregate resources in Nonsan City is influenced by stream activities and sea level changes, with the tidal range of the Yellow Sea acting as an unfavorable condition for the preservation of aggregate resources.

• Proceedings of the KSEEG Conference
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• 2001.05b
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• pp.42-63
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• 2001

The detail survey on the Songsanri tomb site including the Muryong royal tomb was carried out during the period from May 1 , 1996 to April 30, 1997. A quantitative analysis was tried to find changes of tomb itself since the excavation. Main subjects of the survey are to find out the cause of infiltration of rain water and groundwater into the tomb and the tomb site, monitoring of the movement of tomb structure and safety, removal method of the algae inside the tomb, and air controlling system to solve high humidity condition and dew inside the tomb. For these purposes, detail survery inside and outside the tombs using a electronic distance meter and small airplane, monitoring of temperature and humidity, geophysical exploration including electrical resistivity, geomagnetic, gravity and georadar methods, drilling, measurement of physical and chemical properties of drill core and measurement of groundwater permeability were conducted. We found that the center of the subsurface tomb and the center of soil mound on ground are different 4.5 meter and 5 meter for the 5th tomb and 7th tomb, respectively. The fact has caused unequal stress on the tomb structure. In the 7th tomb (the Muryong royal tomb), 435 bricks were broken out of 6025 bricks in 1972, but 1072 bricks are broken in 1996. The break rate has been increased about 250% for just 24 years. The break rate increased about 290% in the 6th tomb. The situation in 1996 is the result for just 24 years while the situation in 1972 was the result for about 1450 years. Status of breaking of bircks represents that a severe problem is undergoing. The eastern wall of the Muryong royal tomb is moving toward inside the tomb with the rate of 2.95 mm/myr in rainy season and 1.52 mm/myr in dry season. The frontal wall shows biggest movement in the 7th tomb having a rate of 2.05 mm/myr toward the passage way. The 6th tomb shows biggest movement among the three tombs having the rate of 7.44mm/myr and 3.61mm/myr toward east for the high break rate of bricks in the 6th tomb. Georadar section of the shallow soil layer represents several faults in the top soil layer of the 5th tomb and 7th tomb. Raninwater flew through faults tnto the tomb and nearby ground and high water content in nearby ground resulted in low resistance and high humidity inside tombs. High humidity inside tomb made a good condition for algae living with high temperature and moderate light source. The 6th tomb is most severe situation and the 7th tomb is the second in terms of algae living. Artificial change of the tomb environment since the excavation, infiltration of rain water and groundwater into the tombsite and bad drainage system had resulted in dangerous status for the tomb structure. Main cause for many problems including breaking of bricks, movement of tomb walls and algae living is infiltration of rainwater and groundwater into the tomb site. Therefore, protection of the tomb site from high water content should be carried out at first. Waterproofing method includes a cover system over the tomvsith using geotextile, clay layer and geomembrane and a deep trench which is 2 meter down to the base of the 5th tomb at the north of the tomv site. Decrease and balancing of soil weight above the tomb are also needed for the sfety of tomb structures. For the algae living inside tombs, we recommend to spray K101 which developed in this study on the surface of wall and then, exposure to ultraviolet light sources for 24 hours. Air controlling system should be changed to a constant temperature and humidity system for the 6th tomb and the 7th tomb. It seems to much better to place the system at frontal room and to ciculate cold air inside tombs to solve dew problem. Above mentioned preservation methods are suggested to give least changes to tomb site and to solve the most fundmental problems. Repairing should be planned in order and some special cares are needed for the safety of tombs in reparing work. Finally, a monitoring system measuring tilting of tomb walls, water content, groundwater level, temperature and humidity is required to monitor and to evaluate the repairing work.