CaSiO3 perovskite in Earth’s deep mantle University of Oxford in United Kingdom

CaSiO ₃ Davemaoite is a high-pressure and high-temperature calcium silicate perovskite mineral with a cubic crystal structure (Tschauner et al., 2021). It is expected to be the third most abundant mineral in the Earth’s lower mantle. Sound velocity measurements found that Davemaoite has lower seismic wave velocities than other major mantle minerals, and Davemaoite-bearing subducted oceanic crust may cause the observed low-seismic structures in the mantle (e.g. Thomson et al, 2019). Furthermore, Davemaoite is likely the weakest lower-mantle phase, controlling the dynamics of the slab subduction process (Immoor et al., 2022).

Despite the importance of understanding the physical and chemical properties of Davemaoite in the lower mantle, the phase stability of this mineral in the lower mantle is poorly constrained, particularly the phase transition to its tetragonal counterpart. A recent study suggested that the cubic-tetragonal phase might intersect with the pressure-temperature path in “cold” subducted slabs (Thomson et al., 2019).

This project is motivated by controversy around the position of the cubic-tetragonal phase boundary of Davemaoite in the lower mantle, which is pivotal to (1) understand its role in explaining seismic observables in the lower mantle, as well as (2) quantifying its importance for understanding slab dynamics and slab delamination. The results from this project will have major impacts on our understanding of the seismic signature of Davemaoite in the lower mantle, the dynamic behavior of subducting slabs, and future research aiming to quantify chemical heterogeneity in the deep mantle from seismic tomography.

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