A Geochemical Study of Selenium in Volcanic Exhalation and Sulfur Deposits. II. On the Behavior of Selenium and Sulfur in Volcanic Exhalation and Sulfur Deposits

Abstract

Abstract With regard to the temperature dependency of the sulfur/selenium ratio in volcanic gases, the factors which control the behavior of selenium and sulfur have been considered from the viewpoints of the chemical equilibrium, the vapor pressure and the thermal balance. It has been found, from the examination of the equilibrium constants, that, unlike the case with sulfur, the most probable form of selenium in volcanic gases is free selenium. The effect of the vapor pressuse is significant in controlling the transfer of selenium and sulfur into volcanic gases. The results of the calculation of the thermal balance show that the observed wide variation in selenium concentration is due to the addition of water vapor. On the other hand, it has been found that selenium and sulfur are extremely unsaturated at higher temperatures. This lack of saturation is caused by the dynamical processes of the introduction of these gases into volcanic gases.