• The Journal of Engineering Geology
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• v.23 no.4
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• pp.477-491
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• 2013

Natural radionuclides in groundwater in the Danyang area were investigated to characterize the behaviors of uranium and radon with respect to lithology and physico-chemical components, which can aid our understanding of their occurrence, properties, and origins. To this end, a total of 100 groundwater samples were collected and analyzed, and radionuclide levels were used to construct detailed concentration maps. The water type of the groundwater, assessed using a Piper diagram, is mainly Ca-Na-$HCO_3$. The concentrations of uranium range from 0.02 to $251.0{\mu}g/L$ (average, $3.85{\mu}g/L$) and only 1% exceed USEPA's MCL (Maximum Contaminant Level). Uranium is enriched in groundwaters of Cretaceous granites and Precambrian metamorphic rocks, whereas it is depleted in groundwaters of sedimentary rocks. The concentrations of radon range from 13 to 28,470 pCi/L (average, 2397 pCi/L). Only 15% of the samples exceed AMCL (Alternative Maximum Contaminant Level) of 4000 pCi/L. The radon concentration is highest in groundwater of Cretaceous granites and lowest in groundwater of sedimentary rocks. In conclusion, the distribution and occurrence of radionuclides are intimately related to the basic geological characteristics of the rocks in which the radiogenic minerals are primarily contained. The behavior of uranium is only weakly related to that of radon (correlation coefficient = 0.15). There are also weak correlations between radionuclides and the main chemical components, pH, EC, Eh, and well depth. Of note, the correlation coefficient between radon and $SiO_2$ is 0.68, and that between radon and $HCO_3$ is -0.48. Factor analysis shows that radionuclides behave somewhat independently of each other because there are no significant factors that control the behavior of chemical components as well as radionuclides. The detailed concentration maps during this study will be used to establish useful database of radionuclide distribution and geological properties throughout Korea.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.36-45
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• 2013

We analyzed natural radionuclides in 80 wells in volcanic rock areas and investigated environmental characteristics. Uranium and radon concentrations ranged from ND to $9.70{\mu}g/L$ (median value: 0.21) ${\mu}g/L$, 38~29,222 pCi/L (median value: 579), respectively. In case of gross-${\alpha}$, 26 samples exceeded MDA (minimum detectable activity, < 0.9 pCi/L) value and the activity values ranged from 1.05 to 8.06 pCi/L. The radionuclides concentrations did not exceed USEPA MCL (maximum contaminant level) value of Uranium ($30{\mu}g/L$) and gross-${\alpha}$ (15 pCi/L). But Rn concentrations in 4 samples exceeded USEPA AMCL (Alternative maximum contaminant level, 4,000 pci/L) and one of them showed a significantly higher value (29,222 pCi/L) than the others. The levels of uranium concentrations in volcanic rock aquifer regions were detected in order of andesite, miscellaneous volcanic rocks, rhyolite, basalt aquifer regions. Radon, however, was detected in order of miscellaneous volcanic rocks, rhyolite, andesite, basalt aquifer regions. The correlation coefficient between uranium and radon was r = 0.45, but we found that correlations of radionuclides with in-situ data or major ions were weak or no significant. The correlation coefficient between the depth of wells and uranium concentrations was a slightly higher than that of depth of wells and radons. Radionuclide concentrations in volcanic rock aquifers showed lower levels than those of other rock aquifers such as granite, metamorphic rock aquifers, etc. This result may imply difference of host rock's bearing-radioactive-mineral contents among rock types of aquifers.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.71-78
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• 2016

This study aimed to evaluate the occurrence of natural radionuclides in Korean groundwater. Groundwater radionuclide data for the period 2000-2011 were obtained from the National Institute of Environmental Research and published literature, classified into five groups according to host rock type, and used to construct detailed concentration maps. Radon, uranium, gross-α, and radium concentrations ranged from 0.4 to 64,688.0 pCi/L (mean: 4,907 pCi/L), 0 to 2,297 μg/L (mean: 27.5 μg/L), 0 to 312 pCi/L (mean: 3.9 pCi/L), and 0 to 17.4 pCi/L (mean: 0.2 pCi/L), respectively. Radon concentrations in 562 of a total 1,501 wells (i.e., 53.5%) exceeded 4,000 pCi/L, which is the acceptable contamination threshold established by the United States Environmental Protection Agency. Uranium, gross-α, and radium concentrations exceeded the respective thresholds of 30 μg/L, 15 pCi/L, and 5 pCi/L in 121 of 1,031 wells (11.9%), 34 of 978 wells (3.5%), and 4 of 89 wells (4.5%), respectively. The mean radionuclide concentration in groundwaters hosted by igneous and metamorphic rocks was higher than that in groundwaters hosted by other rock types, such as volcanics, carbonates, and other sedimentary rocks. The correlations between individual radionuclides were weak or insignificant.

• Journal of the Mineralogical Society of Korea
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• v.28 no.2
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• pp.109-126
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• 2015

Because fault gouge developed at the center of fault is recognized as one of the most important weak sites, it is evident that clay mineralogy and physical properties greatly affect the rock stability. The purpose of this study is to establish the relationship of mineralogy and physical factors that control rock stability in fault zones. We analyzed a total of 51 samples from 16 main faults which were selected from a Korea fracture map, using XRD, SEM, and physical analyses like unit weight, friction and cohesion properties. Though it is considered that the most common clay minerals comprising fault gouge are kaolinite, illite and smectite, clay mineralogy slightly varies depending on lithology: illite > smectite > kaolinite and chlorite in volcanic rocks, kaolinite and chlorite > illite > smectite in sedimentary rocks, and illite > smectite > kaolinite and chlorite in abundance, respectively. Friction angle decreases with increasing clay content. Cohesion increases with increasing clay content below the 45 % region while it decreases with increasing clay content at the region higher than 45%, with some scatters in the data. It is likely that these results are ascribed to the physical heterogeneity of fault gouges with varying content of different clay minerals.

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.239-246
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• 2008

Yeongweol sericite deposit of Gangwon Province is regarded as one of the sericite deposits derived from granitic rocks due to post-magmatic alkali metasomatism, and the other sericite deposit of the same origin is the Daehyun mine of Gyungbug Province. Sericite ores were originated from leucocratic granitic stocks of Cambrian-Triassic age which intruded the pegmatitic migmatite of the unknown age and granite of the Pre-cambrian age, respectivcly. Jangsan quartzite of the lowermost formations of the Paleozoic era, which played as the capping rock protected from the leakage of the hydrothermal solution. It is well known that those sericite deposits arc formed during formation of the geosyncline, and they are also situated in the margins of the Hambaeg Syncline. Leucocratic granites commonly contain pegmatites with tourmaline crystals, and are rich in potassium feldspars, and sodium plagioclase as well. Sericitized ores are mainly found as we go up to the higher elevations or to the margins of the stocks. And some of the Highest grade sericite ores show the monominerallic character composed of nearly pure sericite probably doc to the ultra greisenization. Chemical analysis shows higher $Na_{2}O$ and $K_{2}O$ contents $(2.00\sim7.03wt%)$ as the sericitizations arc preceded and they represent obvious greisenization. But low CaO contents $(0.05\sim4.51wt%)$ indicate that albitizations are so weak. Pyrophyllite of the Youngweol area is often accompanied by the sericite, indicating rather stronger thermal effect than the Daehyun mine. It is known that there are several Sn deposits originated from greisenization in the Taebaegsan region. And greisens are inclined to contain W, Mo and several REE's such as Be, Nb and Li, and so Taebaegsan region interbedded with lots of carbonate formations are still worthwhile to survey for those metallic deposits.

• Journal of Conservation Science
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• v.25 no.4
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• pp.347-361
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• 2009

The Pohang Chilpori is the area with abundant petroglyphs in Korea. The form of the shield, female sex organs, and yut board on the outcrops or float rocks which are composed of the rhyolitic rock are engraved on Chilpori and Shinheungri Petroglyphs. The rhyolitic rock is composed of the phenocryst and groundmass with quartz and feldspar. The rock surface shows mostly yellowish brown color and the rock surface is very irregular by serious weathering, and illite and kaolinite, a kind of the clay minerals, are produced. Deterioration aspects are mainly of surface exfoliation, grain peel-off, damages, scribbling. Chilpori Petroglyph (1) plane has been eroded by running water, in (2) plane has been abrased is on the rock surface, in (3) plane shows surface exfoliation and the various part of the rock surface in plane (4) has become the soil. The corrasion and black phenomenon of the Shinheungri Petroglyph (1) plane was formed by running water, and surface exfoliation and scribbling in plane (2) is serious. Deterioration factors are geomorphologic states, plants, rock of weak to weathering, and artificial influence such as a scribbling and a forest fire. For conservation of the these petroglyphs, study for rock surface conservation and the arrangement of around petroglyphs and construction of water wall are necessary.

• Geophysics and Geophysical Exploration
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• v.17 no.1
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• pp.11-20
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• 2014

To reveal shear-wave velocities ($v_s$) and site characterization of Wonju, Korea, Rayleigh waves were recorded at 78 sites of lower altitude using 12 to 24 4.5-Hz vertical geophones for 20 days during the period of February to September 2013. Dispersion curves of the Rayleigh waves obtained by the extended spatial autocorrelation method were inverted using the damped least-squares method to derive $v_s$ models. From these 1-D models, the average $v_s$ to a depth of 30 m ($v_s30$), $v_s$ of weathered rocks, depths to these basement rocks, and average $v_s$ of the overburden layer were derived to be $16.3{\pm}0.7m$, $576{\pm}8m/s$, $290{\pm}7m/s$, and $418{\pm}13m/s$, respectively, in the 95% confidence range. To determine adequate proxies for $v_s30$, we computed correlation coefficients of $v_s30$ with topographic slope (r = 0.46) and elevation (r = 0.43). An empirical linear relationship is presented as a combination of individually estimated $v_s30$ with weighting factors of 0.45, 0.45, and 0.1 for topographic slope, elevation, and mapped lithology, respectively. Due to a weak correlation between $v_s30$ obtained from inversion of dispersion curves and the proxy-based estimation (r = 0.50), however, the relatively large error range should be considered for applications of this relationship.

• Journal of the Korean earth science society
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• v.25 no.4
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• pp.251-264
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• 2004

The Charnockite in Sancheong region is quarzofeldspathic rock containing orthopyroxene and garnet with a color dark than common granitic rocks. The Chamockite are mostly massive and medium to coarse-grained with K-feldspar phenocryst, but reveal weak foliation. The rock consist mainly of quartz, K-feldspar, plagioclase and orhopyroxene, with biotite, garnet, and anthophyllite. In petrochemistry, the Chamockite has 61-65% $SiO_2$ contents, varying gradually into the margin contacted with orthogneiss, which have compositions of felsic igneous rocks. Major element show almost systematical variation with those of the marginal orthogneisses, except the hornblende gneiss and anorthosite. The Charnockite and orthogneisses show the tholeiitic differentiational trend. Trace and rare earth element abundance patterns in the Charnockite show remarkable negative Sr and Eu anomalies similar to orthogneisses, but different from the hornblende gneiss and anorthosite. Eu contents of the Charnockite are richer than that of orthogneisses. The metamorphic condition of the Charnockite were tested by an orthopyroxene-garnet geotherrnorneter and a plagioclase-garnet geobarometer. Estimated P-T conditions are about $761^{\circ}C$ and 7 kbar at peak metamorphism, but $653^{\circ}C$ and 6.4 kbar at retrograde metamorphism. This suggests that the Charnockite have from an early stage of high-grade metamorphism to represent the granulite facies and then to a late stage medium-grade metamorphism belonging to the amphibolite facies.

• 한국해양학회지
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• v.26 no.2
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• pp.117-132
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• 1991

Marine total magnetic intensity over the southern part of the Ulleung Basin and geomagnetic data measured at a land base station are analyzed. Fourteen days observation of geomagnetic field at a fixed on-land base station showed how the geomagnetic field around the study area behaves. geomagnetic data at the base station can also be used as correction data for a diurnal variation. Magnetic anomalies in the study area do not reflect an effect of sea bottom topography but mainly subsurface basement. The southern part of the Ulleung Basin can be devided into two zones according to a different anomaly pattern; along the coastal shelves the isolated anomalies with a short wave and a strong amplitude are dominant, and toward the open sea the anomalies become much more subdued. The high anomaly zone adjoined to land is interpreted to be caused by granitic intrusives or volcanic rocks, and the weak anomaly zone to the outer sea to be arisen from an existence of deep basement. A spectrum analysis is applied to estimate magnetic basement depths from three anomaly profiles with a long period and a weak amplitude toward the outer sea. The calculated depths are 7.0km, 5.0km, and 2.6km respectively from outer profile. The basement might be correlated with the mixed layer of tuff, basalt, and sediment, which had been defined as L-2 layer in the Yamato basin and the Japan Basin.

• Economic and Environmental Geology
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• v.35 no.2
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• pp.121-136
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• 2002

The $CO_2$-rich springs in the Kyungpook Province has been found at 16 locations. Most of the $CO_2$-rich springs outflow along either fault zones or the geologic boundary between Mesozoic granites and their adjacent rocks. The $CO_2$-rich water samples show a high $CO_2$ concentration ( $P_{CO2}0.46 to 5.21 atm), weak acidic pHs, wide electrical conductivity values ranging from 422 to 2,280 $\mu\textrm{S}$/cm, and high re content. They are classified into the ca-HC $O_3$ type in chemical composition.$\delta$$^{18}$ O and $\delta$$^2$H data indicate that $CO_2$-rich water is meteoric origin. The $\delta$$^{13}$ C values (-1.5$\textperthousand$ to -6.1$\textperthousand$ PDB) suggest that dissolved $H_2$C $O_3$$^{0}$ C $O_3$- are mainly derived from a deep-seated $CO_2$ and carbonate minerals. The thermodynamic equilibrium state between $CO_2$-rich water and major minerals, and hydrochemical characteristics indicate that major source minerals determining the chemical composition of $CO_2$-rich water are carbonate minerals, plagioclase, K-feldspar and Fe-oxides. Under high $CO_2$ pressure and the weak acidic condition, most of the $CO_2$-rich water samples are thermodynamically in the dissolution state with respect to albite and carbonate minerals.