36. DATA REPORT: CORRECTED THERMAL CONDUCTIVITY DATA, LEG 1311
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reflect shortcomings in the experimental method, including poor contacts between the samples and needles, nonsymmetry of the samples and standards, and positioning of the heater and thermistor slightly below the surface of the epoxy block. Freshwater (0.61 W/m °C), fused silica (1.38 W/m °C), and Macor ceramic (1.61 W/m °C) were used during Leg 131 as standards for needle probe measurements. Many of the materials cored during this leg had conductivities higher than that of the Macor, however, making it necessary to calibrate the ODP instrument over a wider range. During the cruise we also used a piece of massive basalt, recovered from a junk basket after Hole 504B cleaning operations on Leg 111, as an additional standard. A subsample of this basalt was sent to the U.S. Geological Survey (USGS) laboratory in Menlo Park for testing prior to Leg 131, but their divided-bar system was not operational at that time. We were able to obtain an estimated conductivity of 1.93 W/m °C for this sample from the USGS needle probe system (which had been separately calibrated against their divided bar system), run in half-space mode; we used this value for calibrating the ODP instrument during Leg 131. After the cruise was completed, the conductivity of the basalt standard was determined with greater accuracy to be 2.05 W/m °C using a divided-bar apparatus (C. Williams, pers. comm., 1990).