SEARCHING THE SINUS-AMORIS - USING PROFILES OF GEOLOGICAL UNITS, IMPACT AND VOLCANIC FEATURES TO CHARACTERIZE A MAJOR TERRANE INTERFACE ON THE MOON

Geochemical profiles of surface units, impact, and volcanic features a re studied in detail to determine the underlying structure in an area of extensive mare/highland interface, Sinus Amoris. This study region includes and surrounds the northeastern embayment of Mare Tranquillita tis. The concentrations of two major rock-forming elements (Mg and Al) , which were derived from the Apollo 15 orbital geochemical measuremen ts, were used in this study. Mapped units and deposits associated with craters in the northwestern part of the region tend to have correlate d low Mg and Al concentrations, indicating the presence of KREEP-enric hed basalt. Found along the northeastern rim of Tranquillitatis were a reas with correlated high Mg and Al concentration, indicating the pres ence of troctolite. Distinctive west/east and north/south trends were observed in the concentrations of Mg and Al, and, by implication, in t he distribution of major rock components on the surface. Evidence for a systematic geochemical transition in highland or basin-forming units may be observed here in the form of distinctive differences in chemis try in otherwise similar units in the western and eastern portions of the study region.