MINOR MAJOR ELEMENT VARIATION WITHIN AND AMONG DIOGENITE AND HOWARDITE ORTHOPYROXENITE GROUPS

Diogenites are orthopyroxenites that may contain chromite and olivine as accessory minerals. Howardite breccias contain orthopyroxenite clasts with similar properties compared to monomict diogenites. We used statistical methods and variation plots of major and minor elements in orthopyroxene and chromite to show whether or not howardite orthopyroxenites are related to monomict diogenites, and to assess their petrogenesis. Our results fail to establish any evidence that monomict diogenites are significantly different from howardite orthopyroxenites in terms of major and minor elements. We also found no differences between Antarctic diogenites and non-Antarctic diogenites. Although element variation plots show compelling evidence that most diogenites originated by igneous fractionation, linear trends among the various diogenites and howardite orthopyroxenite clasts are either non-existent or ill-defined. This militates against an origin from a single magma body, but suggests an origin from multiple magma bodies in the parent planetoid.