Davemaoite Elasticity Reveals Slab‐Induced Heterogeneity in the Mantle Transition Zone

The observed 2%–7% low-shear velocity (VS) anomalies near the subducted slab at the bottom mantle transition zone (MTZ) indicate strong lateral heterogeneity, which is commonly attributed to subducted oceanic crust. However, davemaoite, a major constituent of the subducted oceanic crust, has been poorly constrained in its elasticity, hindering accurate velocity modeling and obscuring the origin of these low-velocity features. Here we report single-crystal elasticity of Ti-bearing davemaoite with the composition of Ca(Si0.57Ti0.43)O3 under high pressure-temperature and found that Ti incorporation significantly reduces velocities and alters the pressure dependence of the shear modulus. Further velocity modeling demonstrated that subducted crusts with varying Ti content have seismic signatures of 1.7(2)–6.8(5)% low-VS at the bottom MTZ, consistent with the observed low-VS structure in the region. These findings highlight the role of slab-derived chemical heterogeneity in generating mantle seismic anomalies and provide new experimental constraints on the structure and dynamics of the deep Earth.