Thermal Conductivity of CaSiO$_3$ Perovskite at Lower Mantle Conditions

TL;DR

This study combines theoretical ab initio calculations and experimental measurements to determine the thermal conductivity of CaSiO$_3$ perovskite under lower mantle conditions, revealing its significant impact on mantle heat transfer.

Contribution

It provides the first combined theoretical and experimental estimate of CaSiO$_3$ perovskite's thermal conductivity at mantle conditions, addressing previous knowledge gaps.

Findings

CaSiO$_3$ perovskite has a surprisingly high thermal conductivity.

Predicted and measured $ppa$ values are in good agreement.

CaSiO$_3$ perovskite could increase lower mantle ppa by about 10%.

Abstract

Thermal conductivity ($\kappa$) of mantle minerals is a fundamental property in geodynamic modeling. It controls the style of mantle convection and the time scale of the mantle and core cooling. Cubic CaSiO$_3$ perovskite (CaPv) is the third most abundant mineral in the lower mantle (LM) (7 vol%). However, despite its importance, no theoretical or experimental estimate of CaPv's $\kappa$ exists. Theoretical investigations of its properties are challenging because of its strong anharmonicity. Experimental measurements at relevant high pressures and temperatures are equally challenging. Here we present $ab$ $initio$ results for CaPv's $\kappa$ obtained using an established phonon quasiparticle approach that can address its strong anharmonicity. We also offer experimental measurements of $\kappa$. Predictions and measurements are in good agreement and reveal a surprisingly large $\kappa$ for cubic CaPv. Despite its relatively low abundance, CaPv's $\kappa$ might increase the lower mantle $\kappa$ by approximately 10%, if accounted for. $\kappa$ of mantle regions enriched in crust material will be more strongly impacted.