Thermal and Magmatic Evolution of the Moon

Thermal models that attempt to explain the asymmetric magmatic evolution of the Moon are still in their infancy. At present, two scenarios seem most plausible for the formation of the Procellarum KREEP Terrane and the long duration of magmatic activity there. First, KREEP may have become concentrated within the PKT as a result of the crust there being thinner than typical. Subsequently, radiogenic heating within this layer would have heated the underlying mantle giving rise to a wide compositional range of basalts. Secondly, a degree- 1 downwelling of ilmenite-rich cumulates may have concentrated both the residual magma-ocean KREEP layer and subsequent magmatism in one hemisphere as has been proposed by Parmentier et al. (2000, 2001). Although the degree- 1 upwelling model of Zhong et al, (2000) can not be dismissed, this seems to be the least plausible model as current estimates of core size would disallow such a hemispheric upwelling. Moreover, this model does not address the origin of the KREEP enhancement found within the Imbrium and Oceanus Procellarum region. Copyright © Mineralogical Society of America.