Chemical Dispersion Among Apollo 15 Olivine-Normative Mare Basalts

Abstract

New analyses of Apollo 15 olivine-normative mare basalts for major and minor elements combined with a synthesis of all published data for them provide no support for the hypothesis that the coarser-grained varieties (olivine microgabbros) consist of two chemical groups. Instead, analyses of the coarse and fine basalts are consistent with their being a single group. The dominant control is that of olivine. The magnitude of olivine fractionation required is great enough to suggest that substantial olivine separation rather than merely short-range unmixing is required. The few coarse picritic basalt samples (feldspathic peridotites) appear to be olivine cumulates from the same parent magma.