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Hydrothermal seepage patterns above a buried basement ridge, eastern flank of the Juan de Fuca Ridge
Earth Sciences Department, University of California, Santa Cruz, California, USA
Department of Geosciences, University of Bremen, Bremen, Germany
Earth Sciences Department, University of California, Santa Cruz, California, USA
Global Undersea Research Unit, University of Alaska Fairbanks, Fairbanks, Alaska, USA
Department of Oceanography, University of Hawaii, Hawaii, USA
Department of Geosciences, University of Bremen, Bremen, Germany
Sandia National Laboratories, Carlsbad, New Mexico, USA
We use the distributions of sediment physical properties and modeled basement overpressures to estimate the spatial distribution of fluid seepage through sediments over and around the “First Ridge,” a buried basement ridge on the eastern flank of Juan de Fuca Ridge. Fluid discharge rates differ by 1 order of magnitude because of differences in sediment hydraulic properties and by 2 orders of magnitude resulting from differences in sediment thickness and basement overpressure. Sediment type distribution appears to have resulted from differences in local seafloor relief. Compression index (ease of consolidation) increases with proportion of hemipelagic material, from 0.5 at 30% hemipelagic to 1.4 at 95% hemipelagic. Permeability at 50% porosity decreases with proportion of hemipelagic material, from 2 × 10−16 m2 at 30% hemipelagic to 6 × 10−18 m2 at 95% hemipelagic. Modeled seepage rates, derived from basement overpressures and sediment physical properties, range from 0 to 27 mm/yr. The average seepage rate over the entire 11 km of ridge within our study area is 1.3 mm/yr. On the basis of the model results, half of the total volume flux of seepage from the First Ridge is contributed from 25% of the study area, with flow rates ≥1.1 mm/yr. Low seismic reflection amplitude anomalies are generally correlated with areas of high seepage rates.
Received 27 February 2003; accepted 29 September 2003; published 14 January 2004.
Citation: (2004), Hydrothermal seepage patterns above a buried basement ridge, eastern flank of the Juan de Fuca Ridge, J. Geophys. Res., 109, B01102, doi:10.1029/2003JB002476.
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