THE VARIATION OF THERMAL TRANSPORT PROPERTIES IN THE EARTHS CRUST

Abstract

Thermal conductivity and thermal diffusivity were determined simultaneously on collections of granites and amphibolites by means of a finite pulse length method. The measurements were performed at pressures up to 500 MPa and at temperatures up to 800°C. Results of investigations of other metamorphic rocks are also presented which were obtained by using the Angstrom method. From the pressure and temperature dependence of the thermal transport parameters their variations within the crust are calculated. It was found that the thermal behaviour is dominated by the influence of the temperature. In the upper crust we have a strong decrease of the thermal diffusivity and a smaller decrease of the conductivity. The effect of pressure becomes increasingly important in the lower crust. Therefore, there is a flat minimum of the thermal transport parameters near the Moho. The importance of different mechanisms influencing the rock behaviour is discussed.