Thorium concentrations in the lunar surface. III - Deconvolution of the Apenninus region

A technique of deconvoluting orbital-gamma ray data which improves spatial resolution and contrast has been applied to Th concentrations in the Apenninus region of the moon. The highest concentration seen from orbit has been found along the northern edge of the data track at Archimedes, requiring a component more highly fractionated in KREEP than the Apollo 15 medium-K Fra Mauro basalt. The results show generally diminishing Th levels extending outward from the Imbrium Basin, and impact penetration of basalt flows in Mare Imbrium to eject sub-mare Th-rich material. The results reinforce the hypothesis that the highlands which border and underlie the western maria contain a pre-mare layer of volcanically-derived KREEP material.