Lattice thermal conductivity of MgSiO3 perovskite and post-perovskite at the core-mantle boundary

Thermal conductivity is essential for controlling the rate of core heat loss and long-term thermal evolution of the Earth, but it has been poorly constrained at the high pressures of Earth's lowermost mantle. We measured the lattice component of thermal diffusivity, heat transport by scattering of phonons, of both MgSiO3 perovskite (Pv) and post-perovskite (PPv) at high pressures of up to 144 GPa and at room temperature. Lattice thermal conductivity of Pv-dominant lowermost mantle assemblage obtained in this study is about 11 W/m/K, while PPv-bearing rocks exhibit similar to 60% higher conductivity. Since such Pv value is comparable to the conventionally assumed lowermost mantle conductivity, our findings do not significantly alter but support the recent notion of high core-mantle boundary heat flow along with a young inner core and high temperatures in the early deep Earth. (C) 2012 Elsevier B.V. All rights reserved.