ABSTRACT

Chemical and isotopic compositions were analyzed on geothermal steam from fumaroles and wells in the Takinoue geothermal area. The distribution of deuterium and oxygen-18 in water samples suggests that the fumarole steam discharge is formed from the rising geothermal fluid through a single-step steam separation process at temperatures of approximately 150∼240°C. On the basis of N₂/Ar, He/Ar and CO₂/N₂ ratios, and δ¹³C values of carbon dioxide in steam, it is concluded that the gas components dissolved in the Takinoue geothermal waters are mixtures of magmatic gases and meteoric waters.