Mineral-water interaction and hydrogeochemistry in the Samkwang mine area, Korea

The abandoned Samkwang mine area was chosen as the research site for radioactive waste disposal in Korea. The study site chiefly consists of Pre-cambrian granitic gneiss, which is considered as potential host rock of a radioactive waste repository. In this study, the chemical composition and residence time of groundwater collected at different depths and locations in the mine adits and boreholes nearby the mine were investigated. The factor analysis of hydrochemical data was applied to illustrate mineral-water reaction processes controlling the chemical composition of groundwater. Three chemical types of groundwater were recognized: Ca-HCO3 type of shallow groundwater and Ca(Mg)-SO4(HCO3) type of shallow and deep groundwater in the mine, and Na-HCO3 type of borehole groundwater. Tritium level indicates that the deep and borehole groundwater is older water recharged before 1950's, and that shallow groundwater is younger water recharged after 1950's. Thermodynamic equilibrium states between major minerals and water samples were calculated in the term of the activities of chemical constituents. The results of this study show that groundwater chemistry in the study area was evolved through the dissolution of calcite, chlorite, albite and sulfides, and the precipitation of clay and oxide minerals. The results of this study would be useful for the assessment of hydrochemical and mineralogical effects on the fate of radionuclides along groundwater pathways in the abandoned mine as a potential radioactive waste repository.