Thermal Conductivity at the Base of the Earth's Lower Mantle

Knowledge of thermal conductivity of mantle minerals is crucial for understanding heat transport from the Earth's core to mantle. Theoretical studies of bridgmanite and ferropericlase have inferred thermal conductivity values ranging from 3 to 9 W/m/K at the base of the convecting mantle [1,2]. Here we present the results of direct measurements of thermal conductivity of single-crystal and multi-phase assemblages of lower mantle minerals at similar conditions (up to 124 GPa, 2500 K) using transient laser heating in a diamond anvil cell. We find that the thermal conductivity of pyrolite is approximately 10 W/m/K. This confirms the finding of Ref. [2] that typical estimates of mantle [3] and core [4] adiabats can be reconciled with 10 to 15 TW of heat flux across a 100 km thick thermal boundary layer at the bottom of the mantle.

[1] X. Tang et al. (2014), GRL, 41, 2746-2752, doi:10.1002/2014GL059385.

[2] S. Stackhouse et al. (2015) EPSL, 427, 11-17, doi:10.1016/j.epsl.2015.06.050

[3] J. M. Brown and T. J. Shankland (1981) GJI, 66, 3, 579-596, doi:10.1111/j.1365-246X.1981.tb04891.x

[4] Pozzo et al. (2012), Nature, 485, 355- 358, doi:10.1038/nature11031