Chemistry of Diogenites and Evolution of their Parent Asteroid

Diogenites are orthopyroxenite meteorites [1]. Most are breccias, but remnant textures indicate they were originally coarse-grained rocks, with grain sizes of order of cm. Their petrography, and major and trace element chemistry support an origin as crustal cumulates from a differentiated asteroid. Diogenites are genetically related to the basaltic and cumulate-gabbro eucrites, and the polymict breccias known as howardites, collectively, the HED suite. Spectroscopic observations, orbit data and dynamical arguments strongly support the hypothesis that asteroid 4 Vesta is the parent object for HED meteorites [2]. Here we discuss our new trace element data for a suite of diogenites and integrate these into the body of literature data. We use the combined data set to discuss the petrologic evolution of diogenites and 4 Vesta.