Sulfide Flanges: Geological, Chemical and Biological Energetics of Active, Exposed Hydrothermal Systems

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The formation of submarine sulfide deposits and the activities involved in chemosynthetically-based hydrothermal food webs are two processes that are energetically interdependent and spatially coincident. Most of the important reactions occur in the subsurface and are therefore generally inaccessible to direct observation. Recently discovered high-temperature pools of buoyant hydrothermal fluid trapped beneath overhanging massive sulfide flanges in the Endeavor vent field on the Juan de Fuca ridge offer an opportunity to document the physical and chemical processes occurring within well-exposed, nearly self-contained, miniature hydrothermal systems that span the temperature range from 350 C to ambient. The project will mount a combined field, laboratory, and theoretical study of a number of these flange-pool systems. The intent is to map thoroughly the geological, geochemical, thermal, and biological relationships within a selected group of flanges, then place a variety of instruments in, on, and around the flanges to collect continuous information about temperature and flux variations over a period of 8 to 10 days. TLhe flanges studied on the bottom will be retrieved for laboratory dissection and analysis involving 3-D mapping of the porosity, permeability, mineralogy, structure, texture, fluids, and microbial distributions.