TY - JOUR
T1 - Origin and evolution of two contrasting thermal groundwaters (CO2-rich and alkaline) in the Jungwon area, South Korea
T2 - Hydrochemical and isotopic evidence
AU - Koh, Yong Kwon
AU - Choi, Byoung Young
AU - Yun, Seong Taek
AU - Choi, Hyeon Su
AU - Mayer, Bernhard
AU - Ryoo, Si Won
PY - 2008/12/30
Y1 - 2008/12/30
N2 - In the Jungwon area, South Korea, two contrasting types of deep thermal groundwater (around 20-33 °C) occur together in granite. Compared to shallow groundwater and surface water, thermal groundwaters have significantly lower δ18O and δD values (> 1‰ lower in δ18O) and negligible tritium content (mostly < 2 TU), suggesting a relatively high age of these waters (at least pre-thermonuclear period) and relatively long subsurface circulation. However, the hydrochemical evolution yielded two distinct water types. CO2-rich water (PCO2 = 0.1 to 2 atm) is characterized by lower pH (5.7-6.4) and higher TDS content (up to 3300 mg/L), whereas alkaline water (PCO2 = 10- 4.1-10- 4.6 atm) has higher pH (9.1-9.5) and lower TDS (< 254 mg/L). Carbon isotope data indicate that the CO2-rich water is influenced by a local supply of deep CO2 (potentially, magmatic), which enhanced dissolution of silicate minerals in surrounding rocks and resulted in elevated concentrations of Ca2+, Na+, Mg2+, K+, HCO3- and silica under lower pH conditions. In contrast, the evolution of the alkaline water was characterized by a lesser degree of water-rock (granite) interaction under the negligible inflow of CO2. The application of chemical thermometers indicates that the alkaline water represents partially equilibrated waters coming from a geothermal reservoir with a temperature of about 40 °C, while the immature characteristics of the CO2-rich water resulted from the input of CO2 in Na-HCO3 waters and subsequent rock leaching.
AB - In the Jungwon area, South Korea, two contrasting types of deep thermal groundwater (around 20-33 °C) occur together in granite. Compared to shallow groundwater and surface water, thermal groundwaters have significantly lower δ18O and δD values (> 1‰ lower in δ18O) and negligible tritium content (mostly < 2 TU), suggesting a relatively high age of these waters (at least pre-thermonuclear period) and relatively long subsurface circulation. However, the hydrochemical evolution yielded two distinct water types. CO2-rich water (PCO2 = 0.1 to 2 atm) is characterized by lower pH (5.7-6.4) and higher TDS content (up to 3300 mg/L), whereas alkaline water (PCO2 = 10- 4.1-10- 4.6 atm) has higher pH (9.1-9.5) and lower TDS (< 254 mg/L). Carbon isotope data indicate that the CO2-rich water is influenced by a local supply of deep CO2 (potentially, magmatic), which enhanced dissolution of silicate minerals in surrounding rocks and resulted in elevated concentrations of Ca2+, Na+, Mg2+, K+, HCO3- and silica under lower pH conditions. In contrast, the evolution of the alkaline water was characterized by a lesser degree of water-rock (granite) interaction under the negligible inflow of CO2. The application of chemical thermometers indicates that the alkaline water represents partially equilibrated waters coming from a geothermal reservoir with a temperature of about 40 °C, while the immature characteristics of the CO2-rich water resulted from the input of CO2 in Na-HCO3 waters and subsequent rock leaching.
KW - CO-rich and alkaline
KW - Jungwon area, Korea
KW - hydrogeochemistry
KW - isotopes
KW - thermal groundwater
KW - water-rock interaction
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U2 - 10.1016/j.jvolgeores.2008.09.008
DO - 10.1016/j.jvolgeores.2008.09.008
M3 - Article
AN - SCOPUS:57049180134
VL - 178
SP - 777
EP - 786
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
SN - 0377-0273
IS - 4
ER -