Lunar basins and craters - Evidence for systematic compositional changes of bombarding population

Abstract

Of the 33 lunar samples considered in the investigation, 31 came from the North Ray Crater. The relationship between meteoritic component and rock type is studied. There appears to be some correlation between the meteoritic component, as given by the Ir/Au ratio, and the rock type, as given by the U content. The relation of ancient meteoritic components to basins and craters is examined, taking into account the resolution of groups, the relative ages from clast-matrix relations, assignments to specific basins or craters, and the relation between meteoritic components and Woenke's 'primary matter'. A table shows seven meteorite-free samples which are all low-alkali cataclastic anorthosites, or anorthositic clasts in light-matrix breccias. The origin of ancient meteoritic bodies are also investigated. The latest data strengthen earlier conclusions that the basin-forming objects were genetically related to the moon.