Antarctic meteorite ALHA81005 - Not just another lunar anorthositic norite

It is contended that 81005 requires the existence of a component that is poor in large-ion lithophile elements, at least as mafic as anorthositic norite, and magnesian rather than ferroan. While no such component has yet been observed in nearside samples, as an end-member in mixing models it would conveniently account for the composition of some polymict samples that heretofore have been difficult to explain as mixtures of endogenous rock types. The results presented here therefore suggest that the early lunar crust contained a significant proportion of both ferroan and magnesian anorthositic norites as primary igneous rocks. It is acknowledged that this conclusion is at variance with models that treat materials of anorthositic norite composition as mixtures of anorthosite plus norite, troctolite, and dunite.