Porosity and hydraulic properties of sediments from the Galapagos Spreading Center and their relation to hydrothermal circulation in the oceanic crust.

S. I. Karato, Keir Becker

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18 Citations (Scopus)

Abstract

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 <50m 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 50m 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 10-4m2 (30-60mdarcies).-Authors

Original languageEnglish (US)
Pages (from-to)1009-1017
Number of pages9
JournalJournal of Geophysical Research
Volume88
Issue numberB2
StatePublished - 1983
Externally publishedYes

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hydrothermal circulation
spreading center
hydraulic property
hydraulics
oceanic crust
crusts
Sediments
sediments
Porosity
porosity
Hydraulics
sediment
Density (specific gravity)
gradients
permeability
impedance
Deep Sea Drilling Project
basements
heat transmission
heat flow

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

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title = "Porosity and hydraulic properties of sediments from the Galapagos Spreading Center and their relation to hydrothermal circulation in the oceanic crust.",
abstract = "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 <50m 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 50m 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 10-4m2 (30-60mdarcies).-Authors",
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TY - JOUR

T1 - Porosity and hydraulic properties of sediments from the Galapagos Spreading Center and their relation to hydrothermal circulation in the oceanic crust.

AU - Karato, S. I.

AU - Becker, Keir

PY - 1983

Y1 - 1983

N2 - 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 <50m 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 50m 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 10-4m2 (30-60mdarcies).-Authors

AB - 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 <50m 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 50m 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 10-4m2 (30-60mdarcies).-Authors

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