THERMAL-PROPERTIES OF GNEISSES AND AMPHIBOLITES - HIGH-PRESSURE AND HIGH-TEMPERATURE INVESTIGATIONS OF KTB-ROCK SAMPLES

The German Continental Deep Drilling Program (KTB) provided the opport unity to carry out a number of different investigations on the same ro cks. So, factors influencing thermal transport properties could be qua ntified. Measurements of thermal diffusivity of amphibolites result in (0.8 +/- 0.2) x 10(-6) m(2) s(-1) under ambient conditions. New data are given for pressure and temperature dependence of thermal transport properties. The comparison of the effect of uniaxial and hydrostatic pressure yields a different behaviour in the lower pressure range up t o 50 MPa. Linear relationships between thermal transport parameters an d pressure are observed in the pressure range from 50 up to 1000 MPa w ith pressure coefficients (0.75 +/- 0.41) x 10(-1) GPa(-1) and (0.61 /- 0.30) x 10(-1) GPa(-1) for the thermal conductivity and thermal dif fusivity, respectively. Temperature has a stronger influence on the th ermal conductivity than pressure with respect to depth. Thermal diffus ivity decreases in the order of 30% from the Earth's surface up to 10 km depth. The anisotropy of the thermal parameters does not depend on pressure and water saturation but it strongly decreases at high temper ature. (C) 1998 Elsevier Science B.V. All rights reserved.