Abstract

Several CO₂-rich springs in the Chungcheong area, i.e., the Angsung spring, the Chojung spring, the Myungam spring, the Bukang spring and the Daepyung spring have been long known for their particular water chemistry. The occurrences of these springs are closely related to the geologic structure of Mesozoic granite such as dyke swarms, fault zones and the geologic boundary between granite and its adjacent gneiss. The CO₂-rich water samples show a high CO₂ concentration (P_CO2 0.25 atm to 0.99 atm), weak acidic pHs and the electrical conductivity ranging from 101 to 2,950 mS/cm. The CO₂-rich water samples are classified into the Ca-HCO₃ type and the Ca(Na)-HCO₃ type in chemical composition. Environmental isotopic data (²H/¹H, ¹⁸O/¹⁶O) indicated that CO₂-rich water was meteoric
origin. The δ¹³C values of CO₂-rich water range from -3.1‰ to -6.8‰ PDB. The values indicate that H₂CO₃⁰ and HCO₃^- of the water samples are mainly originated from a deep-seated source and partly contributed from carbonate minerals. The major minerals determining the chemistry of CO₂-rich water are probably the carbonate minerals which are present as veins and secondary minerals, and the plagiocalse in granite and gneiss.

Keywords CO₂-rich springs, geologic structure, chemical composition, δ¹³C, deep seated source