Abstract. Thorium-rich, marie impact-melt breccias from the Apollo 14-17 missions, that is, those breccias identified with the composition known as "LKFM," are regarded largely as products of basin-forming impacts that penetrated the feldspathic crust and sampled underlying marie material and magma-ocean residuum carrying the compositional signature of KREEP (potassium, rare earth elements, phosphorous). Despite considerable compositional variation among such breccias, compositions of all of them correspond to mixtures of only four components: (1)