Comments on the genesis and evolution of Apollo XI ‘soil’

Abstract

Estimates of compositions of Apollo XI elastic materials and igneous rocks, derived from a review of published data, are used to construct major-element variation diagrams. Compositional differences between ‘soil’ and igneous rocks, previously ascribed by Goles and co-workers to the presence of a cryptic component, do not result solely from admixture of anorthositic lithic fragments. Some inferences on fractionation trends and fractionation mechanisms for lunar igneous rocks can also be drawn from the variation diagrams. The cryptic component is probably laterally-transported material from the region near Tranquility Base. It may convey information about the composition of large portions of the lunar surface. Ancient cryptic components, carrying similar information, perhaps could be studied in lunar breccias.