ABSTRACT

Gas components contained in geothermal steams discharged from wells at the Matsukawa geothermal areas were examined geochemically. The original deep seated gases of Northeast Japan are suggested to be uniform with respect to He, Ar and N₂ and are emitted through geothermal wells and/or fumaroles after mixing in various proportions with atmospheric air dissolved in ground water. Geothermal wells of the Matsukawa area are divided into two groups by the geological structure, of the area which controls the variation in concentrations of tritium and major gas components occurs. The influence of the geological barrier can be considered to be limited in a shallow horizon. The correlation between gas components indicates that the reaction, 2NH₃ = N₂ + 3H₂, is in equilibrium, but the reaction, CH₄ + 2H₂O = CO₂ + 4H₂, is not in equilibrium under the condition of the Matsukawa geothermal reservoir.