Silicon content of fumarolic gases and the formation of a siliceous sublimate

Abstract

A siliceous sublimate, collected from an active fumarole of Kuju Volcano, was analyzed for major constituents.The water soluble fraction of the sublimate contains large quantities of halogen acids and silicon, and the insoluble fraction consists of hydrated silica with a trace amount of native sulfur. In order to as certain the presence of gaseous silicon compounds in fumarolic gases, condensate samples were collected from high temperature fumaroles of Kuja and Nasudake Volcanoes with a silica-free sampling device. The silicon and fluorine contents of fumarolic gases range from 1 to 52 mg Si/kg H20 and 1 to 320 mg F/kg 1120, res pectively.Silicon is transported probably as fluoride in fumarolic gases, and the sublimate is formed by hydrolysis of silicon fluoride when the gas temperature falls to the boiling point of water.