Lunar Cumulate Mantle Overturn: A Model Constrained by Ilmenite Rheology

Lunar cumulate mantle overturn has been proposed to explain the abundances of TiO 2 and heat‐producing elements (U, Th, and K) in the source region of lunar basalts. Ilmenite‐bearing cumulates (IBCs) that were formed near the end of lunar magma ocean solidification are the driving force for overturn. IBCs are enriched with dense TiO 2 and FeO contents and have lower viscosity and solidus than those of the underlying lunar cumulate mantle. We...