SPECTRAL REFLECTANCE STUDIES OF THE GRIMALDI REGION OF THE MOON

Near-infrared reflectance spectra were used to investigate the composi tion and origin of the various geologic units in the Grimaldi region a s well as the stratigraphy of the Grimaldi pre-impact target site. The results of our spectral analysis indicate that the portions of the He velius Formation that occur in the Grimaldi region are composed of nor itic anorthosite and anorthositic norite. Gabbroic material was excava ted from beneath Orientale-related units by small impact craters in th ree areas in the Grimaldi region. The primary ejecta deposits of the G rimaldi basin as well as the pre-Orientale floor unit are dominated by noritic anorthosite and anorthositic norite. The peak ring of Grimald i is composed, at least in part, of pure anorthosite. The anorthosites on the inner ring and elsewhere within Grimaldi were derived from a l ayer of pure anorthosite that exists at depth beneath a more pyroxene- rich unit.