A Geochemical Study of Selenium in Volcanic Exhalation and Sulfur Deposits

Abstract

Abstract Regarding selenium in volcanic materials collected at fumaroles of the Nasudake (36°07′N, 139°57′E) and the Kuju (33°07′N, 131°13′E) volcanoes, Japan, the following results have been obtained. 1) The selenium content in condensed water has no relation to that of sulfur and chlorine. The selenium content in certain sulfur deposits is strongly affected by the mode of occurrence, such as sublimation and solidification, as well as by the outlet temperature of the fumarole. The ratio of selenium to sulfur in both condensed water and sulfur deposit is related with gas temperature at the outlet of fumarole. The higher the gas temperature, the lower the degree of fractionation between selenium and sulfur. 2) The S/Se ratio in the original volcanic gases at Nasudake is close to 1.8×104, found in fumarolic gases with the highest temperature. The S/Se ratio in sulfur deposit is at least one-seventh that in condensed water. 3) Continuous observation over a short period (3 hr.) showed that the selenium content in condensed water varies considerably with time, while the sulfur content remains constant.