ABSTRACT

The steam, water and dissolved sulphate in the discharges from the Otake geothermal bores have been isotopically analyzed. The results show that the Otake geothermal water is derived from local meteoric water with ¹⁸O shift of a few per mill. From the oxygen isotopic fractionation between dissolved sulphate and water, assuming equilibrium conditions, isotopic equilibrium temperature has been estimated for each bore. Estimated temperatures range from 180 to 280°C, and they are consistent with the measured and chemically estimated temperatures.