Geochemistry of Geothermal Water in Pohang, Korea

Abstract

Hydrogeochemical and isotopic characteristics were investigated for groundwater of the Tertiary basin in southeastern part of Korea where deep drilling is in progress for geothermal investigation. According to geology, the aquifer was distinguished as alluvial, tertiary sedimentary bedrock (bedrock groundwater), and fractured volcanic rock (deep groundwater). Groundwater of each aquifer is distinctively separated in Eh-pH conditions and concentrations of Cl, F, B and HCO3. Deep groundwater has very low levels of 3H and 14C whereas alluvial groundwater has those of recent precipitation level. However one of deep groundwater show mixed characteristics in terms of hydrochemistry which indicates effect of pumping. Deep groundwaters have temperature of 38 to 43oC whereas bedrock and alluvial groundwater have temperature less than 20oC. Fractured basement rock aquifer has a different hydrogeological setting from the bedrock and alluvial aquifer considering hydrogeochemical and isotopic characteristics, and temperature.