The elastic constants of MgSiO3 perovskite at pressures and temperatures of the Earth's mantle

TL;DR

This study uses advanced computer simulations to determine the elastic properties of MgSiO3 perovskite at mantle conditions, helping interpret seismic data and revealing significant temperature variations and heterogeneity in Earth's lower mantle.

Contribution

It provides the first ab initio molecular dynamics calculations of MgSiO3 perovskite's elastic properties at mantle pressures and temperatures, linking mineral physics with seismic tomography.

Findings

Lower mantle temperature contrast of about 800K at 1000 km depth

Temperature difference exceeds 2000K near the core-mantle boundary

Indications of significant anelasticity or heterogeneity in the mantle

Abstract

The temperature anomalies in the Earth's mantle associated with thermal convection1 can be inferred from seismic tomography, provided that the elastic properties of mantle minerals are known as a function of temperature at mantle pressures. At present, however, such information is difficult to obtain directly through laboratory experiments. We have therefore taken advantage of recent advances in computer technology, and have performed finite-temperature ab initio molecular dynamics simulations of the elastic properties of MgSiO3 perovskite, the major mineral of the lower mantle, at relevant thermodynamic conditions. When combined with the results from tomographic images of the mantle, our results indicate that the lower mantle is either significantly anelastic or compositionally heterogeneous on large scales. We found the temperature contrast between the coldest and hottest regions of the mantle, at a given depth, to be about 800K at 1000 km, 1500K at 2000 km, and possibly over 2000K at the core-mantle boundary.