Thermophysical properties of deep ocean sediments∗

Abstract This report presents laboratory measurements of several thermal and mechanical properties for two reconstituted ocean sediments. Thermal conductivity and diffusivity were obtained at temperatures up to 420° C for one sediment and at 600 bars pressure for both sediments. Values obtained for conductivity generally ranged from 0.8 to 1.0 W/mK and tended to decrease with temperature. Diffusivity values ranged from 2.2 to 2.9 X 10‐7 m2/s, with a peak around 200°C. Good agreement was obtained between measured thermal properties and calculations of the properties, using a simple mixture model. The sediments used were reconsolidated illite and smectite obtained from dredging and coring operations in the North Pacific Ocean. Permeability and shear strength data were obtained at room temperature and pressure both before and after the thermal properties measurements. Both properties were found to increase by more than an order of magnitude after pressurization and heating. The shear strength increase is consistent with SEM examination, which indicated the formation of a precipitate that might have caused cementing of platelets. The observed increase in permeability is as yet unexplained.