Porosity and hydraulic properties of sediments from the Galapagos spreading center and their relation to hydrothermal circulation in the oceanic crust

Journal Article · Thu Feb 10 04:00:00 EST 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB088iB02p01009· OSTI ID:6151878

Karato, S; Becker, K

Density and porosity of sediments were measured on DSDP legs 69 and 70 samples from the Galapagos spreading center. Permeability and the hydraulic impedance of each sediment layer were estimated from measured values of porosity. The gradients of porosity and density with depth where sediment layers are thin (< or approx. =50 m thick) are anomalously high compared with those of other areas and with the upper part of thicker sediment layers in this area. A good correlation was found between the anomalous porosity and density gradients and the present-day heat flow. We interpret these observations to suggest that these high gradients may be due to active hydrothermal circulation through a thin sediment cover, which is inhibited by a thicker sediment layer, and that the pattern of hydrothermal circulation may be essentially fixed with the moving plate. Hydraulic impedance of the sediment layer was estimated from the observed depth variation of porosity and was shown to increase rapidly with its thickness. Our interpretation that a threshold thickness of about 50 m would inhibit direct diffuse discharge or recharge of hydrothermal flow through the undisturbed sediment layer yields an average permeability of the underlying basement layer of about 3-6 x 10/sup -14/ m/sup 2/ (30-60 mdarcies).

• Research Organization: Ocean Research Institute, University of Tokyo, Nakano, Tokyo 164, Japan
• OSTI ID: 6151878
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 88:B2; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150301 -- Geothermal Exploration &amp; Exploration Technology-- Geophysical Techniques &amp; Surveys
58 GEOSCIENCES
580500* -- Oceanography-- (1980-1989)
CONVECTION
DENSITY
EARTH CRUST
ENERGY SYSTEMS
GEOTHERMAL SYSTEMS
HEAT FLOW
HYDROTHERMAL SYSTEMS
OCEANIC CRUST
PACIFIC OCEAN
PERMEABILITY
PHYSICAL PROPERTIES
POROSITY
SEA-FLOOR SPREADING
SEAS
SEDIMENTS
SURFACE WATERS