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 ∼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.

► We measured lattice thermal diffusivity of MgSiO3 perovskite and post-perovskite up to 144 GPa.
► Obtained thermal conductivity of perovskite-dominant lowermost mantle is about 11 W/m/K.
► Post-perovskite exhibits ∼70% higher conductivity than perovskite.
► Our findings support the recent estimates of high heat flux across the core–mantle boundary.