Some Alteration Phenomena in the Volcanic Rocks at the Fumaroles, Volcano Yakedake, Prefectures Nagano-Gifu

Abstract

1. The Volcano Yakedake (Prefectures Nagano-Gifu), in Central Japan has been almost dormant since 1932, only with weak fumarole activity in and around its summit dome. 2. Temperature of the fumarole gases, steam vapour with or without a little amount of H₂S and SO₂, is not higher than 100℃. 3. The water in these five craterlets on the summit faintly contains some chemical components and in the two of them, some influences of volcanic emanation are found in the composition of the water. 4. In the peripheries of the active fumaroles, some alteration minerals such as halotrichite, alunogen, and natron-alunite, were identified. The former two are mixed with each other in various proportion. The chemical transformation of the volcanic rocks in its alteration processes is here discussed.