Olivine-dominated asteroids and meteorites: Distinguishing nebular and igneous histories
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CitationSunshine, J. M., Bus, S. J., Corrigan, C. M., McCoy, T. J., & Burbine, T. H. (2007). Olivine‐dominated asteroids and meteorites: Distinguishing nebular and igneous histories. Meteoritics & Planetary Science, 42(2), 155-170.
PublisherThe Meteoritical Society
JournalMeteoritics & Planetary Science
AbstractMelting models indicate that the composition and abundance of olivine systematically co-vary and are therefore excellent petrologic indicators. However, heliocentric distance, and thus surface temperature, has a significant effect on the spectra of olivine-rich asteroids. We show that composition and temperature complexly interact spectrally, and must be simultaneously taken into account in order to infer olivine composition accurately. We find that most (7/9) of the olivine-dominated asteroids are magnesian and thus likely sampled mantles differentiated from ordinary chondrite sources (e.g.,pallasites). However, two other olivine-rich asteroids (289 Nenetta and 246 Asporina) are found to be more ferroan. Melting models show that partial melting cannot produce olivine-rich residues that are more ferroan than the chondrite precursor from which they formed. Thus, even moderately ferroan olivine must have non-ordinary chondrite origins, and therefore likely originate from oxidized R chondrites or melts thereof, which reflect variations in nebular composition within the asteroid belt. This is consistent with the meteoritic record in which R chondrites and brachinites are rare relative to pallasites.