9407099 Schoonen The objective of the research is to evaluate through experimental studies and field work the role sulfur oxyanions may play in hydrothermal systems. Because little is known about the stability of these sulfur species, the PI has conducted experiments in the first stage of this program to study the stability of thiosulfate. For this funding cycle, the PI proposes to focus the experimental work on the formation of thiosulfate. Two pathways for thiosulfate formation: 1) H2S-SO4 equilibration in the presence of mineral surfaces and metal ions, and 2) H2S oxidation with FE(III) bearing minerals as oxidants will be studied to temperatures up to 250oC. A third major pathway, H2S oxidation by O2, is the focus of our field work. Yellowstone will be used as a natural lab to complement the experimental studies at Stony Brook. This field work will prepare us for the challenges of sampling deep hydrothermal fluids which is a long-term objective.
