Geochemical and Isotopic Compositions and Geothermometry of Thermal Waters in the Magumsan Area, South Korea

The Magumsan thermal waters of the southeastern Korean Peninsula are pumped out of six deep wells (average depth, 300 m) at temperatures of 30.8–49 °C. The thermal waters are chemically classified into two groups: NaHCO3 type (40 °C), both of which have chemical compositions that are distinct from l...

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Bibliographic Details
Published in:Water (Basel) 2019, Vol.11 (9), p.1774
Main Authors: Jeong, Chan-Ho, Lee, Byeong-Dae, Yang, Jae-Ha, Nagao, Keisuke, Kim, Kyu-Han, Ahn, Sang-Won, Lee, Yong-Cheon, Lee, Yu-Jin, Jang, Hyeon-Woo
Format: Article
Language:English
Subjects:
Aquifers
Chemical composition
Deep wells
Geotemperature
Geothermometers
Groundwater
Heat
Helium
Hydrogen sulfide
Isotopes
Mass spectrometry
Meteoric water
Oxidation
Radioisotopes
Scientific imaging
Seawater
Sodium chloride
Sulfur
Thermal energy
Thermal water
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Summary:The Magumsan thermal waters of the southeastern Korean Peninsula are pumped out of six deep wells (average depth, 300 m) at temperatures of 30.8–49 °C. The thermal waters are chemically classified into two groups: NaHCO3 type (40 °C), both of which have chemical compositions that are distinct from local groundwater (Ca–HCO3 type). δ18O and δD values suggest that the thermal waters originate from meteoric water and they are isotopically fractionated by silicate hydration or H2S exchange. δ34S values (+7.0 to +15%) of dissolved sulfate in the thermal waters reflect enrichment in 34S through kinetically controlled oxidation of magmatic pyrite in the thermal aquifer and mixing with paleo-seawater. On the 3He/4He vs. 4He/20Ne diagram, the thermal waters plot along a single air mixing line of dominant crustal He, which indicates that the heat source for the thermal waters is non-volcanogenic thermal energy that is generated from the decay of radioactive elements in crustal rocks. Chalcedony geothermometry and thermodynamic equilibrium calculations using the PHREEQC program indicate a reservoir temperature for the immature thermal waters of 54–86 °C and 55–83 °C, respectively.
ISSN:2073-4441
2073-4441
DOI:10.3390/w11091774