Diamonds are crucial in understanding the deep Earth’s carbon cycle, offering essential insights into the composition and processes of deep mantle. To effectively explore diamond-rich regions, it is essential to understand their unique seismic signatures. In this study, we employed ab initio PBEsol methods to calculate thermodynamic and elastic properties of diamonds under the Earth’s mantle conditions. Our findings show good agreement with experimental data at lower pressures and temperatures and extend the analysis up to 140 GPa and 4000 K, allowing for a comprehensive examination of the entire mantle. The elastic moduli of diamonds exhibit notable nonlinear responses to pressure and temperature variations. Additionally, the elastic anisotropy of ASpo of diamonds is significantly pronounced. We calculated density and wave velocity profiles for diamonds along mantle geotherms, revealing that diamond have higher bulk and shear moduli and lower density when compared to the reference state (PREM) of the lower mantle. We also calculated the density and seismic wave velocities (VP, VS) in a peridotitic mantle mixture as a function of the diamond content. The results indicate that even minimal amounts of diamond integrated with the background mantle can substantially reduce density and enhance seismic velocities in the lower mantle. As a result, we predict diamond may accumulate in the upper mantle over time. The diamond-rich regions will exhibit exceptionally high and anisotropic seismic velocities under Earth’s extreme pressure and temperature conditions, as well as on other planetary bodies. These findings provide new approaches for probing diamond-rich zones and investigating the role of carbon in Earth’s geological history.

This content is PDF only. Please click on the PDF icon to access.
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.