Elasticity of CaSiO₃–CaTiO₃ perovskite at lower-mantle pressures

Abstract. Calcium silicate perovskite (named davemaoite, Ca-Pv for short) is believed to be the third most abundant mineral in Earth's lower mantle. Knowledge of its elasticity is important to constrain velocities of pyrolite and basalt models in lower-mantle conditions and then decipher the origins of seismic signatures via comparison with observed seismic velocities. Here elasticities and sound velocities of cubic CaSiO3–CaTiO3 perovskites at lower-mantle pressures have been investigated by first-principles calculations. The incorporation of titanium into cubic Ca-Pv increases C11 but decreases C12 and C44 at high pressures. As a result, elastic moduli (KS and G) and wave velocities (VP and VS) decrease with increasing Ti content. Cubic CaSiO3 exhibits high-seismic-velocity anisotropies at low pressures, which gradually decrease with increasing pressure, reaching minimum values near the lowermost mantle. In contrast, Ti-bearing Ca-Pv shows an initial decrease in velocity anisotropies, followed by a progressive increase at higher pressures. Compositional effects on elastic properties and velocity anisotropies of cubic CaSiO3–CaTiO3 perovskites are significant at lower-mantle pressures. Considering the amounts of Ca-Pv in pyrolite and basalt models, Ti-bearing Ca-Pv may be responsible for the observed seismic velocity anomalies associated with subducted oceanic crust and a potential source of seismic anisotropies in the lower mantle.