| Abstract |
Geochemical studies have been carried out on the deep hot waters discharged from geothermal wells in the Nigorikawa Basin located in southwestern Hokkaido, Japan. Geothermal reservoirs in this area can be classified into three types based on the relationship between the enthalpy and C1 concentrations of hot waters. Each reservoir is separated by the existence of the caldera, and the reservoir located outside of the caldera is the most productive. Concentration of Ca, So4 and CO3 in is controlled by the solubility of anhydrite and calcite. On the other hand, concentration of Na and K is controlled by the equilibrium between hot waters and sodium and potassium minerals. |