Radiative conductivity and abundance of post-perovskite in the lowermost mantle

TL;DR

This study measures the radiative thermal conductivity of post-perovskite at core-mantle boundary conditions, revealing its significant abundance and impact on Earth's deep mantle dynamics.

Contribution

It provides the first experimental determination of radiative conductivity of post-perovskite under relevant conditions, highlighting its role in Earth's lowermost mantle.

Findings

Post-perovskite's radiative conductivity is ~40% lower than bridgmanite.

Post-perovskite is as abundant as bridgmanite in the lowermost mantle.

Results have implications for deep Earth thermal and dynamic models.

Abstract

Thermal conductivity of the lowermost mantle governs the heat flow out of the core energizing planetary-scale geological processes. Yet, there are no direct experimental measurements of thermal conductivity at relevant pressure-temperature conditions of Earth's core-mantle boundary. Here we determine the radiative conductivity of post-perovskite at near core-mantle boundary conditions by optical absorption measurements in a laser-heated diamond anvil cell. Our results show that the radiative conductivity of Mg0.9Fe0.1SiO3 post-perovskite (< 1.2 W/m/K) is ~ 40% smaller than bridgmanite at the base of the mantle. By combining this result with the present-day core-mantle heat flow and available estimations on the lattice thermal conductivity we conclude that post-perovskite is as abundant as bridgmanite in the lowermost mantle which has profound implications for the dynamics of the deep Earth.