Davemaoite Exists Throughout the Earth’s Lower Mantle

Lin Wang, Nobuyoshi Miyajima, Fei Wang, Tomoo Katsura

Nature Geoscience 18, 365-369 (2025) https://www.nature.com/articles/s41561-025-01657-9

Davemaoite, a calcium silicate perovskite mineral, is key to understanding the mantle's chemical evolution and geodynamics. It incorporates many incompatible elements and has low rheological strength and seismic velocity. However, whether davemaoite exists independently or dissolves into bridgmanite in the lower mantle remains unclear.
To investigate this, we used cutting-edge ultrahigh-pressure multi-anvil techniques to measure calcium solubility in bridgmanite under lower mantle conditions. We found that calcium solubility in bridgmanite is extremely low. While solubility increases slightly with temperature, it decreases with pressure, and bridgmanite composition has minimal effect. Our thermodynamic data, extrapolated to core-mantle boundary conditions, shows that bridgmanite cannot dissolve all davemaoite in typical mantle compositions, even when the mantle begins melting. Therefore, davemaoite remains a distinct phase alongside bridgmanite throughout the lower mantle.
This low calcium solubility in bridgmanite suggests that davemaoite-rich domains formed at the core-mantle boundary during late-stage basal magma ocean crystallization. These domains could store trace elements and source some ocean island basalts like High-μ. Radioactive isotopes like 238U accumulating in davemaoite may have delayed inner core formation by keeping the core hot. These domains might also explain large low-shear-wave-velocity provinces, given davemaoite's low seismic velocity.

Figure: Large low-shear wave velocity province (LLSVP) explained by the persistence of davemaoite in the lower mantle