ABSTRACT

Kinetic dissolution experiments show that the rate of Al³⁺ dissolution from microcline is greater in sulfuric acid than in hydrochloric acid of the same pH value and temperature. Approximately linear relations were obtained by plotting the concentration of Al³⁺ against those of H⁺, Cl^- and HSO₄^- in 27 water samples collected in the Kusatsu hot-spring area; the highest value of the correlation coefficients was found for Al³⁺ - HSO₄^-, which suggests that Al³⁺ and HSO₄^- might have been derived from the same source. Since sulfuric acid is considered to be formed at or near the earth's surface, it is reasonable to suppose that Al³⁺ in the thermal solution was extracted from wall rocks of relatively shallow depths under the influence of sulfuric acid.