• 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.

• Korean Journal of Heritage: History & Science
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• v.37
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• pp.285-307
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• 2004

Synthesize and examine petrological characteristic and geochemical characteristic by weathering formation of rock and progress of weathering laying stress on stone cultural properties of Unjusa temple of Chonnam Hwasun county site in this research. Examine closely weathering element that influence mechanical, chemical, mineralogical and physical weathering of rocks that accomplish stone cultural properties and these do quantification, wish to utilize by a basic knowledge for conservation scientific research of stone cultural properties by these result. Enforced component analysis of rock and mineralogical survey about 18 samples (pyroclastic tuff; 7, ash tuff; 4, granite ; 4, granitic gneiss; 3) all to search petrological characteristic and geochemical characteristic by weathering of Unjusa temple precinct stone cultural properties and recorded deterioration degree about each stone cultural properties observing naked eye. Major rock that constitution Unjusa temple one great geological features has strike of N30-40W and dip of 10-20NE being pyroclastic tuff. This pyroclastic tuff is ranging very extensively laying center on Unjusa temple and stone cultural properties of precinct is modeled by this pyroclastic tuff. Stone cultural propertieses of present Unjusa temple precinct are accomplishing structural imbalance with serious crack, and because weathering of rock with serious biological pollution is gone fairly, rubble break away and weathering and deterioration phenomenon such as fall off of a particle of mineral are appearing extremely. Also, a piece of iron and cement mortar of stone cultural properties everywhere are forming precipitate of reddish brown and light gray being oxidized. About these stone cultural properties, most stone cultural propertieses show SD(severe damage) to MD(moderate damage) as result that record Deterioration degree. X-ray diffraction analysis result samples of each rock are consisted of mineral of quartz, orthoclase,plagioclase, calcite, magnetite etc. Quartz and feldspar alterated extremely in a microscopic analysis, and biotite that show crystalline form of anhedral shows state that become chloritization that is secondary weathering mineral being weathered. Also, see that show iron precipitate of reddish brown to crack zone of tuff everywhere preview rock that weathering is gone deep. Tuffs that accomplish stone cultural properties of study area is illustrated to field of Subalkaline and Peraluminous, $SiO_2$(wt.%) extent of samples pyroclastic tuff 70.08-73.69, ash tuff extent of 70.26-78.42 show. In calculate Chemical Index of Alteration(CIA) and Weathering Potential Index(WPI) about major elements extent of CIA pyroclastic tuff 55.05-60.75, ash tuff 52.10-58.70, granite 49.49-51.06 granitic gneiss shows value of 53.25-67.14 and these have high value gneiss and tuffs. WPI previews that is see as thing which is illustrated being approximated in 0 lines and 0 lines low samples of tuffs and gneiss is receiving esaily weathering process as appear in CIA. As clay mineral of smectite, zeolite that is secondary weathering produce of rock as result that pick powdering of rock and clothing material of stone cultural properties observed by scanning electron micrographs (SEM). And roots of lichen and spore of hyphae that is weathering element are observed together. This rock deep organism being coating to add mechanical weathering process of stone cultural properties do, and is assumed that change the clay mineral is gone fairly in stone cultural properties with these. As the weathering of rocks is under a serious condition, the damage by the natural environment such as rain, wind, trees and the ground is accelerated. As a counter-measure, the first necessary thing is to build the ground environment about protecting water invasion by making the drainage and checking the surrounding environment. The second thing are building hardening and extirpation process that strengthens the rock, dealing biologically by reducing lichens, and sticking crevice part restoration using synthetic resin. Moreover, it is assumed to be desirable to build the protection facility that can block wind, sunlight, and rain which are the cause of the weathering, and that goes well with the surrounding environment.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.3
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• pp.202-212
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• 1992

This study reports on the genesis and mineralogical characteristics of the clay minerals in the soils derived from the five major parent rocks of granite, granite-gneiss, limestone, shale, and basalt in Korea. The investigation on the mineralogical aspects of primary and secondary minerals of the rocks and coarse fractions in the soils have been already reported. In this report, the identification of clay minerals in the soil clay fractions was done through the analyses of chemical, X-ray diffraction, and thermal methods. The studies showed clearly that much of the clay minerals was evolved by the weathering of primary minerals and some were further developed by the transformation of secondary minerals. Cation exchange capacity(CEC) of the clay fractions increased with higher amotunts of vermiculite, chlorite, and illite, however, decreased with higher hydroxy octahedral sheet within the interlayer spaces of vermiculite even if dominant clay with vermiculite. Feldspars in the granite and granite-gneiss might be completely transformed to kaolin mineral, Illite, chlolrite, and vermiculite formed by the alteration of micas, amphibole, augite, and primary chlorile seem to be subsequently transformed to the mixed layer minerals such as illite/vermiculite, illite/chlorite, and chlorite/vermiculite. These weathering products may be ultimately transformed into kaolin minerals. The smectite minerals in the clay fractions of the soils developed on the limestone are considerably present and they seem to be formed directly by the precipitation from high Mg solution and/or by the transformation of vermiculite from micas and chlorite in the parent materials. Abundant presence of illite in the soil clays developed on the shale is considered to have inherited from the fine particles and more resistant hydrous muscovite. The weathering sequences of the hydrous muscovite were as follows according to the degree of soil development ; hydrous muscovite ${\rightarrow}$ illite/vermiculite mixed layer(Inceptisols, Daegu series) and hydrous muscovite ${\rightarrow}$ illite/vermiculite mixed layer ${\rightarrow}$ vermiculite ${\rightarrow}$ kaolin mineral(Alfisols, Buyeo series). The plagioclase in the basalt might be mostly weathered to kaolin minerais. The augite in the basalt is likely to be transformed through progressive stage of weathering, augite ${\rightarrow}$ chlorite ${\rightarrow}$ chlorote/vermiculite mixed layer ${\rightarrow}$ vermiculite ${\rightarrow}$ kaolin. Another weathering sequence of augite could be expected, augite ${\rightarrow}$ chlorite ${\rightarrow}$ illite by the presence of illite and illite/vermiculite mixed layer in the clay fractions. Vermiculite and gibbsite were quantified from thermogravimetry(TG) and kaolin minerals, from both TG and differerential thermal analysis (DTA). Vermiculite in Jangseong series from the limestone was the dominant clay mineral of 21.7 percent and had a range in the order of 9.2 percent in Buyeo series to 5.4 percent in Daegu series from the shale. The rest soils ranged from 8.8 to 28.3 percent. Kaolin minerals were the dominant clay mineral of 32.7 percent in Asan series from the granite-gneiss and Gueom series of 32.0 percent from the basalt. The soils from the limestone ranged from 9.4 to 14.9 percent. The rest soils ranged from 8.9 to 28.6 percent. Gibbsite were 3.9 and 2.3 percent for Weoljeong and Chahang series from the granite, respectively. In Asan and Cheongsan series from the giranite-gneiss were 1.4 and 4.5 percent, respectively, and 3.6 percent in Jangpa series from the basalt.

• Conservation Science in Museum
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• v.19
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• pp.1-18
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• 2018

The Stele for National Preceptor Hongbeop from the Jeongtosa Temple site in Chungju is one of the most important stone cultural heritage items for exemplifying the style of the Goryeo era. Despite its obvious value, this relic has been stored in a weathered condition at the National Museum of Korea. It had suffered various dismantling and displacements during the Japanese colonial period and had long been exposed in the open air. The stele was selected as a subject for the Stone Monuments Restoration Project launched by the National Museum of Korea in 2015. In preparation for its outdoor exhibition as part of the restoration project, this study investigated the characteristics of its materials, produced a map of its deterioration from weathering, and carried out ultrasonic analysis of the materials to provide findings useful for conservation treatment. The materials analysis revealed that the turtle-shaped pedestal of the stele was made from two-mica granite consisting of medium-grained quartz, plagioclase, alkali feldspar, biotite, and muscovite. Its body stone is crystalline marble, the rock-forming mineral in which is medium-grained calcite in a rose-pink color with dark grey spots. The dragon top of the stele is made of crystalline marble, the major component of which is medium-grained calcite of a light-grey color. The deterioration consists of 21.5% abrasion on the stone body, with its south face most damaged, and 18.6% granular disintegration, with the north face most damaged. The ultrasonic material characterization conducted for mapping the general condition of weathering shows low values on the parts-assembly area of the turtle-shaped pedestal and on the upper portion of the stone body. It is considered that there is dislocation due to partial blistering and fracturing as well as to the differences in surface treatment. Prior to the outdoor exhibition of the stele, the surface was cleaned of contaminants and was consolidated based on the scientific investigation in order to prevent weathering from the external environment.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.359-370
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• 2009

Arsenic and heavy metals leached out as a result of oxidation of tailings exposed to the surface pose a serious environmental contamination of mine areas. This study investigated how arsenic behavior is controlled by a variety of processes, such as oxidation of sulfides and formation or alteration of secondary minerals, based on mineralogical methods. The study was carried out using the tailing samples obtained from Nakdong mine located in Jeongseongun, Gangwondo. After separating magnetic and non-magnetic minerals using pretreated tailing samples, each mineral sample was classified according to their colors and metallic lusters observed by the stereoscopic microscope. Subsequently, the mineralogical properties were determined using various instrumental analyses, such as x-ray diffractometer (XRD), energy dispersive spectroscopy (EDS), and electron probe micro analyzer (EPMA). The literature review confirmed that various ore minerals were identified in the Nakdong ore deposits. In this study, however, there were observed a few original ore minerals as well as secondary and/or tertiary minerals newly formed as a result of weathering including oxidation. In particular, we did not recognize pyrrhotite which has been known to originally exist in a large abundance, but peculiarly colloform-type iron (oxy)hydroxides were identified, which indicates most of pyrrhotite has been altered by rapid weathering due to its large reactivity. In addition, a secondary scorodites filling the fissure of weathered primary arsenopyrites were identified, and it is speculated that arsenic is immobilized through such a alteration reaction. Also, we observed tertiary iron (oxy)hydroxides were formed as a result of re-alteration of secondary jarosites, and it suggests that the environment of tailing has been changed to high pH from low pH condition which was initiated and developed by oxidation reactions of diverse primary ore minerals. The environmental change is mainly attributed to interactions between secondary minerals and parental rocks around the mine. As a result, not only was the stability of secondary minerals declined, but tertiary minerals were newly formed. As such a process goes through, arsenic which was immobilized is likely to re-dissolve and disperse into surrounding environments.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.671-687
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• 2022

It has been reported that about 47% of groundwater wells within 10 km from the coastline in the western/southern coastal areas of Korea were affected by seawater. It has been interpreted that the cause of groundwater salinization is seawater intrusion. The Gilsan stream in the Seocheon area was a tidal stream until the Geumgang estuary dam was constructed and operated. Therefore, it is likely that the Gilsan stream catchment was deposited with sediments containing high-saline formation water prior to the use of landfill farmland at this catchment area. The groundwater in this study area showed EC values ranging from 111 to 21,000 µS/cm, and the water quality types were diverse including Ca(or Na)-HCO₃, Ca(or Na)-HCO₃(Cl), Na-Cl(HCO₃), Na-Cl types. It is believed that this diversity of water quality is due to the mixing of seawater and fresh groundwater generated by infiltration of precipitation and surface water through soil and weathered part. In this study, we discussed whether this water quality diversity and the presence of saline groundwater are due to present seawater intrusion or to remnant high-saline pore water in sediments during flushing out process. For this, rain water, surface water, seawater, and groundwater were compared regarding the water quality characteristics, tritium content, oxygen/hydrogen stable isotopic composition, and ⁸⁷Sr/⁸⁶Sr ratio. The oxygen/hydrogen stable isotopic compositions indicated that water composition of saline groundwaters with large EC values are composed of a mixture of those of fresh groundwater and surface water. Also, the young groundwater estimated by tritium content has generally higher NO₃ content. All these characteristics showed that fresh groundwater and surface water have continued to affect the high-saline groundwater quality in the study area. In addition, considering the deviation pattern in the diagrams of Na/Cl ratio versus Cl content and SAR (sodium adsorption ratio) versus Cl content, in which two end members of fresh surface-ground water and seawater are assumed, it is interpreted that the groundwater in the study area is not experiencing present seawater intrusion, but flush out and retreating from ancient saline formation water.