Thermodynamic and elastic properties of uvarovite at mantle conditions: Insights from first-principles calculations

Abstract Uvarovite, an important garnet component in the Earth’s mantle, plays a critical role in interpreting seismic signatures of the deep Earth. In this study, we employed first-principles calculations based on density functional theory (DFT) to examine the thermodynamic and elastic properties of uvarovite under high-pressure and high-temperature conditions (up to 30 GPa and 3000 K). Our results show that elastic moduli and seismic velocities increase with pressure but decrease with temperature, displaying a slightly nonlinear response. The relatively low AVP of uvarovite suggests that its contribution to the observed seismic anisotropy in the upper mantle is likely negligible. We simulated the variations in density and wave velocity of uvarovite along the geotherm, and investigated the potential geophysical effects of its enrichment in different geological bodies. At depths of 50–250 km, uvarovite exhibits higher density while maintaining shear wave velocities (VS) comparable to the reference model, implying that minor compositional variations may drive density heterogeneities within the subcontinental lithospheric mantle (SCLM) and potentially promote craton delamination. At depths of 250–660 km, uvarovite shows higher density and lower seismic velocities (VP, VS) relative to the upper mantle (UM) and mantle transition zone (MTZ). Our results demonstrate that at 660 km depth, the addition of 20 vol.% uvarovite to pyrolite increases density by +4.0%, while reducing compressional wave (VP) and shear wave (VS) velocities by −2.0% to −2.9%. If uvarovite becomes locally enriched in the mantle transition zone, it is likely to generate seismically detectable low-velocity layers, which could significantly influence Earth's mantle dynamics.