9316328 Crozaz Several projects mostly based on the results obtained with prior NSF support are planned: a) comprehensive microanalytical studies of interstellar SiC and graphite in order to elucidate their formation in stars, b) trace element and isotopic studies of eucrites and ureilites to clarify the origin of these meteorite classes, and c) trace element measurements of Siberian eclogites to understand their formation and relationship to similar samples from their kimberlites. Extreme differences in isotopic composition compared to solar system material identify SiC and graphite grains from primitive meteorites as circumstellar dust. Isotopic measurements of these grains combined with astrophysical theory are contributing new insights into nucleosynthesis and stellar evolution. Future work on interstellar grains from separates prepared at the University of Chicago will emphasize the complete understanding of the dust, and to this end will combine ion microprobe isotopic measurements with determinations of trace element abundances as well as detailed physical studies in the TEM. To better understand the petrogenesis of eucrite and ureilite meteorites, minor and trace element abundances (particularly rare earth elements) will be determined by in situ ion microprobe measurements. A study of Siberian eclogites will be extended to additional xenoliths assumed to have sampled a wide range of depths within the mantle. Eclogite inclusions present in some of the Siberian diamonds will also be analyzed to determine whether the diamonds are cogenetic with the eclogite hosts.
