EFFECTS OF TEMPERATURE AND MANTLE DYNAMICS ON ESTIMATES OF THE THERMAL-CONDUCTIVITY IN THE DEEP MANTLE

Estimates are made of the thermal conductivity ki of the deep mantle as a function of the temperature jump Delta T across a thermal boundary layer at the core-mantle boundary (CMB). Three types of boundary layer, corresponding to differing physical processes at the CMB, are investigated, and the effect of temperature-dependent thermal conductivity is calculated for each. The consequences of lateral heterogeneities are considered. Results indicate that if the temperature jump Delta T seen by most of the mantle at the CMB is large (1350 K) then k(i) cannot be more than 6 W m(-1)K(-1) if the conductivity is constant, or 8 W m(-1)K(-1) if it is temperature dependent. If Delta T is small (350 K) then k(i) may be 16 W m(-1)K(-1) or higher. The dynamics of the boundary layer is important: results suggest that hot-spot plumes are not the only mechanism for removing heat from the core.