Permeability, electrical resistivity, and thermal conductivity measurements were performed on samples from the Bent Hill area of the Middle Valley on the northern Juan de Fuca Ridge. Thermal conductivity measurements were also made on samples from the Trans-Atlantic Geotraverse (TAG) hydrothermal area in the Mid-Atlantic Ridge for direct comparison with previous studies and the Middle Valley results. Electrical resistivity and permeability measurements were made as a function of confining pressure on 15 samples comprising different lithologic compositions found in the Bent Hill area. The effect of pressure on electrical resistivity values is relatively small and the observed frequency dependence is highly controlled by the sulfide content in these rocks. Permeabilities are in the 10-16-10-20 m2 (0.1-100 µD) range. Although permeability does not recover in samples that undergo significant permanent deformation, the elastic permeability dependence on confining pressure is relatively small. Permeability correlates with porosity. Permeability anisotropy correlates with the presence of oriented sulfide veins with increased flow parallel to the veins. Thermal conductivity measurements made on 41 samples from Middle Valley and 9 samples from the TAG area show systematic variations due to changes in composition and a weak relationship with porosity for sedimentary samples from Middle Valley. A comparison between the divided-bar and the half-space needle-probe methods of measuring thermal conductivity shows good agreement for the Leg 169 measurements unlike previous results from Legs 139 and 158. The discrepancies observed in earlier studies seem to be related to the long times used in the older measurements for the optimal T vs. ln(t) data interval. The apparatus used during Leg 169 was smaller, sampled a smaller volume of core, and in high conductivity material was not influenced by boundary effects.
1Iturrino, G.J., Davis, E., Johnson, J., Gröschel-Becker, H., Lewis, T., Chapman, D., and Cermak, V., 2000. Permeability, electrical, and thermal properties of sulfide, sedimentary, and basaltic units from the Bent Hill area of Middle Valley, Juan de Fuca Ridge. In Zierenberg, R.A., Fouquet, Y., Miller, D.J., and Normark, W.R. (Eds.), Proc. ODP, Sci. Results, 169 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/169_SR/chap_08/chap_08.htm>. [Cited YYYY-MM-DD]
2Borehole Research Group, Lamont-Doherty Earth Observatory of Columbia University, Route 9W, Palisades NY 10964-8000, USA. iturrino@ldeo.columbia.edu
3Geological Survey of Canada, GSC Pacific - Sidney Subdivision, Pacific Geoscience Centre, PO Box 6000, 9860 West Saanich Road, Sidney, BC V8L 4B2, Canada.
4New England Research Inc., 76 Olcott Drive, White River Junction VT 05001, USA.
5Division of Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami FL 33149, USA.
6Department of Geology and Geophysics, University of Utah, 135 South 1460 East, Salt Lake City UT 84112-0111, USA.
7Geophysical Institute, Czech Academy of Science, 141-31 Praha 4, Czechoslovakia.
Date of initial receipt: 3 January 1999
Date of acceptance: 14 February 2000
Date of publication: 31 August 2000
Ms 169SR-115