Measurement of thermal diffusivity of rocks at high pressure

A method for measurement of thermal diffusivity at high hydrostatic pressure was developed by adapting a radial symmetry heat flow method wherein a sinusoidal heat wave is applied to the cylindrical surface of the sample. The accuracy of the measuring system was tested using Pyroceram 9606. Data obtained were within 5% of published values at all temperatures to 400 C and a dependence upon pressure was observed. Thermal diffusivity of three crystalline igneous rock specimens was measured at temperatures from 32 to 400 C and pressures from 0.1 to 200 MPa. The results for Creighton quartz diorite showed only limited temperature and pressure dependence. In the case of Stripa and Westerly granites, this dependence was found to be more substantial. Thermal diffusivity of Strips granite decreased by more than 50% from 32 to 400 C and that of Westerly granite decreased by approximately 40% over the same range.