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Rn Occurrences in Groundwater and Its Relation to Geology at Yeongdong Area, Chungbuk, Korea
충북 영동군의 복합 지질과 지하수 라돈 함량과의 연관성에 대한 고찰
Econ. Environ. Geol. 2018 Oct;51(5):409-28
Published online October 31, 2018;  https://doi.org/10.9719/EEG.2018.51.5.409
Copyright © 2018 the Korean society of economic and environmental gelology.

Sang-Ho Moon1*, Soo-Young Cho1 and Sunghyun Kim2
문상호1* ·조수영1 ·김성현2

1Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, 34132, Korea
2GeoGreen21, 901 E&C Venture Dream Tower, Digital-ro 33 gil 55, Guro-gu, Seoul 08376, Korea
1한국지질자원연구원 지질환경연구본부 지하수연구센터, 2(주)지오그린21
Received August 16, 2018; Revised September 5, 2018; Accepted October 18, 2018.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
Yeongdong area is located on the border zone between Precambrian Yeongnam massif and central southeastern Ogcheon metamorphic belt, in which Cretaceous Yeongdong sedimentary basin exists. Main geology in this area consists of Precambrian Sobaeksan gneiss complex, Mesozoic igneous and sedimentary rocks and Quaternary alluvial deposits. Above this, age-unknown Ogcheon Supergroup, Paleozoic sedimentary rocks and Tertiary granites also occur in small scale in the northwestern part. This study focuses on the link between the various geology and Rn concentrations in groundwater. For this, twenty wells in alluvial/weathered zone and sixty bedrock aquifer wells were used. Groundwater sampling campaigns were twice run at wet season in August 2015 and dry season in March 2016. Some wells placed in alluvial/weathered part of Precambrian metamorphic rocks and Jurassic granite terrains, as well as Cretaceous porphyry, showed elevated Rn concentrations in groundwater. However, detailed geology showed the distinct feature that these high-Rn groundwaters in metamorphic and granitic terrains are definitely related to proximity of aquifer rocks to Cretaceous porphyry in the study area. The deeper wells placed in bedrock aquifer showed that almost the whole groundwaters in biotite gneiss and schist of Sobaeksan gneiss complex and in Cretaceous sedimentary rocks of Yeongdong basin have low level of Rn concentrations. On the other hand, groundwaters occurring in rock types of granitic gneiss or granite gneiss among Sobaeksan gneiss complex have relatively high Rn concentrations. And also, groundwaters occurring in the border zone between Triassic Cheongsan granites and two-mica granites, and in Jurassic granites neighboring Cretaceous porphyry have relatively high Rn concentrations. Therefore, to get probable and meaningful results for the link between Rn concentrations in groundwater and surrounding geology, quite detailed geology including small-scaled dykes or vein zones should be considered. Furthermore, it is necessary to take account of the spatial proximity of well location to igneous rocks associated with some mineralization/hydrothermal alteration zone rather than in-situ geology itself.
Keywords : Yeongdong area, geology, Rn concentrations of groundwater, proximity to Cretaceous porphyry, mineralization/hydrothermal alteration zone

 

October 2018, 51 (5)