Clay mineral in the volcanic ash erupted from Shinmoe-dake, Kirishima volcanoes in 1992

Abstract

Volcanic ash from 1992 eruption of Shinmoe-dake was investigated. Smectite and gypsum are present besides feldspar, pyroxenes, hornblende and cristobalite. An energy dispersive X-ray analysis indicates that the smectite is a Fe-rich smectite. The smectite resulted from rock alteration by a geothermal system within the cone at relatively low temperatures before the eruption.