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The physical properties of oceanic basement rocks from deep drilling on the Mid-Atlantic Ridge

1976; American Geophysical Union; Volume: 81; Issue: 23 Linguagem: Inglês

10.1029/jb081i023p04042

2156-2202

R. D. Hyndman, Malcolm J. Drury,

Seismic Waves and Analysis

Journal of Geophysical Research (1896-1977)Volume 81, Issue 23 p. 4042-4052 Vertical Structure of the Oceanic Lithosphere The physical properties of oceanic basement rocks from deep drilling on the Mid-Atlantic Ridge R. D. Hyndman, R. D. HyndmanSearch for more papers by this authorM. J. Drury, M. J. DrurySearch for more papers by this author R. D. Hyndman, R. D. HyndmanSearch for more papers by this authorM. J. Drury, M. J. DrurySearch for more papers by this author First published: 10 August 1976 https://doi.org/10.1029/JB081i023p04042Citations: 125AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract The physical properties of compressional and shear velocity, electrical resistivity, bulk and grain density, porosity and water content, and thermal conductivity have been measured on a large collection of basalt samples and a few gabbros and serpentinized peridotites recovered by drilling on the mid-Atlantic ridge near 37°N. Samples were recovered to 582 m into basaltic basement in one hole, and rocks that may be representative of the lower crust were recovered from another hole. The mean compressional velocity of the basalts of 5.94 km s−1 agrees well with previous fresh unweathered sea floor basalts. It, however, can be reconciled with the much lower average upper crustal layer 2 seismic refraction velocities generally observed only by the presence of extensive large-scale fracturing and voids in the crust. The laboratory velocities of the gabbros are consistent with upper layer 3, or oceanic layer, refraction velocities. Lower layer 3 refraction velocities are consistent with a composition of a mix of gabbro and unserpentinized peridotite. Poisson's ratio for little-weathered laboratory samples of basalt is found to decrease systematically with decreasing velocity. The mean electrical resistivity of the basalts is 220 ohm m at 25°C. A close dependence of resistivity on porosity and a moderate increase in resistivity with pressure suggest conduction primarily through pore fluid. The basalt resistivity decreases rapidly with increasing temperature, the mean becoming about 20 ohm m at 100°C and about 5 ohm m at 150°C. The mean basalt bulk density is 2.795 g cm−3, the mean porosity is 7.8%, and the mean thermal conductivity at 21°C is 3.97 mcal cm−1 s−1 °C−1. References Archie, G. E., The electrical resistivity log as an aid in determining some reservoir characteristics, Trans. 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Citing Literature Volume81, Issue23Solid Earth and Planets10 August 1976Pages 4042-4052 ReferencesRelatedInformation