Timing, Abundance, and Spatial Extent of Initial Magmatism on the Moon Explained By Cumulate Mantle Overturn

We have recently quantified the timing, abundance, and spatial extent of lower mantle melting induced by cumulate overturn on the Moon through a series of 3D geodynamical models. Our dynamical modeling indicates that overturn of thin (~30-50 km) and weak ilmenite-bearing cumulates (IBC) triggers a rapid, short-lived, and widespread period of lower mantle melting which reproduces the key geochronological, volume, and spatial characteristics associated with the onset of secondary magmatism on the Moon (Figs. 1,2), and without energy contributions from KREEP (potassium, rare earth elements, phosphorus, radiogenic U, Th). Within the guiding paradigms of global differentiation via magma ocean crystallization and subsequent cumulate mantle overturn, our model provides explanation for near contemporaneous primary and secondary crust production constrained by geochronology of returned lunar samples and meteorites.

In this abstract, we discuss our results in context with several intricacies of lunar chronology including models of a long-lived magma ocean, the hypothesis that mantle overturn was induced by the giant South Pole-Aitken basin forming impact, and ancient lunar zircon.