• Title/Summary/Keyword: uraniferous rock

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Hydrochemistry of Groundwater in the Uraniferous Sedimentary Rocks of the Ogcheon Belt, Republic of Korea (옥천대 우라늄 광화대 부근 퇴적암 지하수의 수리화학적 특성)

  • Hwang, Jeong
    • Journal of the Korean earth science society
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    • v.31 no.3
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    • pp.205-213
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    • 2010
  • A hydrochemical comparative study of groundwater in uraniferous sedimentary rock of the Ogcheon belt was carried out to investigate the genetic relationship between uraniferous groundwater of Daejeon area and uraniferous sedimentary rocks of the Ogcheon zone. The groundwater shows weak alkaline pH values rangingfrom 6.4 to 8.1 and low Eh values ranging from -50 to 225 mV. The groundwaters to Ca-$HCO_3$ type that shows high concentration of $Ca^{2+}$ and $HCO_3^_$ due to the dissolution of carbonate mineral in limestone. The concentration of uranium in the groundwater was measured very low below $3.2{\mu}g/L$, while it was detected as much as $1165{\mu}g/L$ in the mine waste water. The low Eh value of groundwater is one of the main causes of low uranium concentration of groundwater in uraniferous sedimentary rocks in the Ogcheon belt. It is suggested that the uranium of groundwater in granitic region of Daejeon area was not mainly provided from uraniferous sedimentary rocks in the Ogcheon belt.

Geological Review on the Distribution and Source of Uraniferous Grounwater in South Korea (국내 고함량 우라늄 지하수의 분포와 기원에 관한 지질학적 고찰)

  • Hwang, Jeong
    • The Journal of Engineering Geology
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    • v.28 no.4
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    • pp.593-603
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    • 2018
  • The most of groundwater with high U-concentration occur in the Jurassic granite of Gyeonggi massif and Ogcheon belt, and some of them occur in the Cretaceous granite of Ogcheon belt. On the contrary, they do not occur in the Jurassic granite of Yeongnam massif and the Cretaceou granite of Gyeongsang basin. The Jurassic and Cretacous granite, the host rock of high U-groundwater, were resulted from parental magma with high ratio of crustal material and highly differentiated product of fractional crystalization. These petrogenetic characteristics explain the geological evidence for preferential distribution of uraniferous groundwater in each host rock. It were reported recently that high U-content, low Th/U ratio and soluble mineral occurrence of uraninite in the two-mica granite of Daejeon area which have characteristics of S-type peraluminous and highly differntiated product. It is the mineralogical-geochemical evidences supporting the fact that the two-mica granite is the effective source of uranium in groundwater. The biotite granite and two-mica granite of Jurassic age were reported as biotite granite in many geological map even though two-mica granite occur locally. This fact suggest that the influence of two-mica granite can not be ignored in uraniferous groundwater hosted by biotite granite.

Characteristics of Uraniferous Minerals in Daebo Granite and Significance of Mineral Species (대보화강암내 함우라늄 광물의 산출특징과 존재형태의 중요성)

  • 추창오
    • Journal of the Mineralogical Society of Korea
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    • v.15 no.1
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    • pp.11-21
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    • 2002
  • A mineralogical study was made in order to identify the relationship between uranium content in groundwater and rock chemistry using core rocks recovered from the drilling holes for wells in the Daebo Granite areas. Uraniferous minerals are of primary origin and occur as inclusions in accessory minerals such as zircon, monazite, and xenotime. Since the uraniferous minerals are very small to be 1 ~ 2 $\mu$m in size, it is difficult to distinguish their mineralogical species precisely. The frequent presence of dissolution cavities or dissolved textures in the accessory minerals suggests that uraniferous minerals dissolved partially and contributed to the groundwater chemistry. Because there is no clear relationship between host rocks and groundwater for uranium concentration, mineralogical characteristics of uraniferous minerals, together with aqueous geochemical conditions favorable for uranium dissolution, could play important roles in groundwaster chemistry.

Geochemical evidence for K-metasomatism related to uranium enrichment in Daejeon granitic rocks near the central Ogcheon Metamorphic Belt, Korea

  • Hwang, Jeong;Moon, Sang-Ho
    • Geosciences Journal
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    • v.22 no.6
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    • pp.1001-1013
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    • 2018
  • A new type of uranium occurrence in Korea was identified in pegmatitic and hydrothermally altered granite in the Daejeon area. The U-bearing parts typically include muscovite, pink-feldspar and sericite as alteration minerals. In this study, the geochemical characteristics and alteration age of the granitic rocks were examined to provide evidence for hydrothermally-enriched uranium. The K-Ar ages of muscovite coexisting with U-bearing minerals were determined as 123 and 128 Ma. The U-bearing rocks have relatively low ($CaO+Na_2O$), high $K_2O$ contents, and high alteration index values by major element geochemistry. The trace element geochemistry shows that the uraniferous rocks have significantly low Th/U ratios and strongly differentiated features. The rare earth element patterns indicate that the uraniferous rocks have a low total REE and LREE contents with depletion of Eu. Considering the geochemical variation of the granitic rock major, trace and rare earth elements, it can be concluded that uranium enrichment in pegmatites and altered granite should be genetically related to post-magmatic hydrothermal alteration of K-metasomatism after emplacement of the two-mica granite. This is the first report for geochemical characteristics of Mesozoic granite-related U-occurrences in South Korea. This study will help further research for uranium deposits with similarities in geological setting, mineralogy and age data between South China and Korea, and can also be expected to help solve the source problems related to high uranium concentrations in some groundwater occurring in the granitic terrane.

Radon Concentrations in Groundwater of the Goesan Area, Korea (괴산지역 지하수의 라돈 함량)

  • Cho, Byong-Wook
    • Journal of Soil and Groundwater Environment
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    • v.22 no.5
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    • pp.63-70
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    • 2017
  • Radon concentrations were measured in 250 groundwater samples collected from the Goesan area where uraniferous black slate and granites abundantly occur in the formations. The measured radon levels ranged from 0.90 to 7,218.7 Bq/L with the median value of 54.3 Bq/L, similar to the value measured in the nationwide survey in 4,853 wells (52.1 Bq/L). The median value was highest in the Cretaceous granite area (390.0 Bq/L) while it was as low as 20.0~58.8 Bq/L in the Ogcheon meta-sedimentary rock areas. About 23.6% of the total samples exceeded the WHO guideline value of 100 Bq/L established in 2011. The exceeding rate was 69.0, 39.4, and 7.0~13.7% in the Cretaceous granite area, Jurassic granite area, and Ogcheon meta-sedimentary rock areas, respectively.

Radon-222 Concentrations of Metropolitan Subway Stations and Soils in the Seoul (서울 지하철역(地下鐵驛) 승강장(昇降場) 및 토양내(土壤內) 유해(有害)라돈함량(含量) 연구(硏究))

  • Hong, Young-Kook;Kim, Sung-Oh;Kim, Tong-Kwon
    • Economic and Environmental Geology
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    • v.31 no.3
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    • pp.215-222
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    • 1998
  • The radon (Rn-222) potential of metropolitan subway stations and soils in Seoul city were delineated using alpha-track filter and EDA-200 radon detectors, respectively. The uranium (U) and thorium (Th) contents were also determined using a Multi Channel Analyzer to identify the sources of radon gas. The average U concentrations in Seoul varies according to basement rock types. For example, there is $9.40{\pm}10.11ppm$ in the Precambrian metasedimentary rock (PM), $9.08{\pm}2.85ppm$ in the Jurassic Kwanaksan granite (JK) and $4.94{\pm}1.43ppm$ in the Jurassic Seoul granite (JS). Uranium contents in soil samples are $10.30{\pm}4.74ppm$ in JK, $10.10{\pm}7.43ppm$ in PM and $6.69{\pm}3.95ppm$ in JS and these closely reflect the content of uraniferous minerals. The levels of soil radon are $604{\pm}273pCi/L$ in JK, $502{\pm}275$ in JS and $262{\pm}211pCi/L$ in PM. The soil radon concentrations are shown to reflect soil permeability and porosity rather than their U contents. The mean indoor radon contents in subway stations are $1.50{\pm}0.62pCi/L$ on the 4th line, $1.41{\pm}0.95pCi/L$ on the 3rd line, $0.84{\pm}0.13pCi/L$ on the 1st line and $0.80{\pm}0.25pCi/L$ on the 2nd line. The subway stations located in the JK have the highest average radon concentration with $2.04{\pm}0.65pCi/L$, where levels of $1.57{\pm}0.81pCi/L$ occur in the JS and $0.80{\pm}0.23pCi/L$ in the PM. The highest radon levels of 4.1 pCi/L occur mainly in Keongbokkung station on the 3rd line and these exceed 4 pCi/L of the US EPA action level.

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