Differentiation of volcanic emanation around the boiling point of water in geothermal regions in Japan

Abstract

The nature of the differentiation of the volcanic emanations around the boiling point of water has been made clear in detail by this study in some geothermal regions./The chemical composition of the parent volcanic emanation supplied at the Atosanupuri-Kawayu geothermal district has been calculated by the theory of the differentiation of the magmatic emanation proposed by the present authors. The chemical composition of the parent volcanic emanation obtained is not so different from that of the volcanic emanation observed usually at the active volcanoes. The facts observed at these geothermal districts support one of the process of the differentiation of the magmatic emanation, that is, the elimination of hydrogen chloride and sulfur dioxide from volcanic gases and the formation of acidic hot springs around the boiling point of water. Hydrogen chloride and sulfur dioxide supplied in deep places are usually eliminated from the volcanic emanation on the way up to the ground surface by the above mentioned processes of differentiation of the magmatic emanation and are not observed in fumarolic gases of low temperatures in such geothermal districts. When the drilling holes have enough depths to collect directly the parent volcanic emanations, hydrogen chloride and sulfur dioxide can be detected in their volcanic emanations. The volcanic gases from drilling holes at the Oowakidani geothermal district are the case which clearly demonstrates such situations.