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Geophysical Monograph Series



  • Deep-sea ecology—Congresses
  • Mid-ocean ridges—Congresses



Environmental conditions within active seafloor vent structures: Sensitivity to vent fluid composition and fluid flow

Margaret Kingston Tivey

Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

Environmental conditions within chimneys and flanges of seafloor vent deposits are deduced by estimating rates of fluid flow, and calculating temperatures and compositions of pore fluids by considering diffusive and advective transport across the structures. The composition and temperature of seawater and vent fluid at the bounds and the physical configuration (pore and mineral distribution) of the chimney or flange are factored into the calculations. Calculated conditions, particularly the pH and the oxidation state of pore fluids, differ significantly from conditions calculated assuming batch mixing of vent fluid and seawater, and are sensitive to the composition of the end-member vent fluid, and different styles of mixing. The temperature of the transition from oxidized to reduced conditions can vary from <3°C to ∼90°C. Thus thermophilic aerobes and mesophilic anaerobes may reside within vent structures. The calculated available metabolic energy within vent structures is dominantly a function of the oxidation state of the pore fluid, and differs little from amounts calculated for batch mixing. The pH of pore fluids within thin chimneys and flanges is low, ranging from <3 to 4.5 at temperatures of 80°C to 120°C unless there is advection inward of seawater across a 1-layer wall, or outward of vent fluid that has a chloride concentration close to or greater than that of seawater, in which case pH is near neutrality. These results indicate a wide range of environments present within seafloor vent deposits. The conclusion that pH within pore fluids of most thin chimneys and flanges is low indicates that initial enrichments for hyperthermophiles from seafloor vent samples should be made under low pH conditions.

Citation: Kingston Tivey, M. (2004), Environmental conditions within active seafloor vent structures: Sensitivity to vent fluid composition and fluid flow, in The Subseafloor Biosphere at Mid-Ocean Ridges, Geophys. Monogr. Ser., vol. 144, edited by W. S. Wilcock et al., pp. 137–152, AGU, Washington, D. C., doi:10.1029/144GM09.


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