9708501 Cuhel Yellowstone Lake, WY is situated in the caldera of one of the largest volcanic eruptions known. Geothermally heated water percolating through the relic chamber is highly enriched in carbonates, silicates, chloride, and methane, with some location additionally rich in iron and sulfide. The proposed interdisciplinary research will provide background necessary to begin modeling basin-wide fluxes of mineral components to elucidate the contribution of geothermally altered groundwaters to the biogeochemistry of receiving systems. The overall objective is to develop a quantitative understanding leading to a biogeochemical flux and mass balance model for the hydrothermal vent system. Specific objectives include: (1) determining the importance of vent and fumarole emanations relative to shallow groundwater and sediment-water flux, (2) identifying short and long-term variability in submarine vent activity, (3) assessing the potential geochemical interactions of phosphate and arsenic with iron during formation of iron oxides formed via vent fluid interactions with cold lake water, (4) determining the relative importance of abiotic sulfur oxidation and microbially-mediated sulfur oxidation, (5) determining the specific contributions of photosynthethic, heterotrophic and chemolithotrophic biomass production, and (6) analyzing transformations of S by measuring the stable isotope composition of minerals, organic matter, and micro- and macroorganisms. This proposal was submitted in response to the Environmental Geochemistry and Biogeochemistry (EGB) solicitation, NSF 96-152. The proposed research is collaborative with J. Maki of Marquette University. The project is being jointly funded by the Divisions of Earth Sciences, Environmental Biology, Chemistry, and the MPS Office of Multidisciplinary Activities.
