FEO AND TIO2 CONCENTRATIONS IN THE SOUTH-POLE AITKEN BASIN - IMPLICATIONS FOR MANTLE COMPOSITION AND BASIN FORMATION

We use newly developed spectroscopic methods for determining FeO and T iO2 abundances to study the huge (2500 km diameter) South Pole-Aitken basin. The floor of this basin shows iron and titanium values which ar e weakly correlated and largely range from 7 to 14 wt % FeO and from 0 .5 to 1.5 wt % TiO2. This composition is consistent with an approximat e 1:1 mixture of lower crustal material like that found elsewhere on t he Moon and mantle rock containing 10-16 wt % FeO and < 0.1 wt % TiO2. Although mantle rock appears to compose about 50% of the floor deposi ts, models of the formation of large impact basins predict that virtua lly all the floor materials ought to be derived from the mantle.