9706142 Schoonen The goal of this project is to use the sulfur oxyanion speciation of hydrothermal solutions and acid crater lakes as indicators of magmatic-hydrothermal and volcanic processes. The effort will focus on two processes: 1) sulfur hydrolysis and 2) the changes in S-speciation in acid crater lakes due to the discharge of H2S and SO2 gas. Sulfur hydrolysis may be important in (1) hydrothermal systems as a source of sulfate where native sulfur occurs in the subsurface (e.g., as buried solfataras); and (2) in crater lakes where the sulfur oxyanion speciation during quiescent times is likely to be controlled by colloidal sulfur or pools of molten sulfur. Upon increased activity, crater lakes act as a scrubber of magmatic S-bearing gases. The influx of these gases changes the sulfur oxyanion speciation in crater lakes drastically (polythionates, SnO62- , are lost from solution), but details are not understood. The research strategy is based on a combination of field work and experimental work. The goal of the field work is to develop a sampling and preservation protocol for sulfur oxyanions based on the notion that these anions can be retained on a resin. A protocol in which columns with this resin are used to preserve the speciation would allow for the study of crater lakes and hydrothermal systems around the world. Experiments will be conducted to simulate sulfur hydrolysis and condensation of sulfur gases in crater lakes.
