Meteoritics & Planetary Science 45, Nr 12, 1906–1928 (2011) doi: 10.1111/j.1945-5100.2010.01130.x The Northwest Africa 1500 meteorite: Not a ureilite, maybe a brachinite Cyrena Anne GOODRICH1*, Noriko T. KITA2, Michael J. SPICUZZA2, John W. VALLEY2, Jutta ZIPFEL3, Takashi MIKOUCHI4, and Masamichi MIYAMOTO4 1Planetary Science Institute, 1700 E. Ft. Lowell Road, Tucson, Arizona 85719, USA 2Wisc-SIMS, Department of Geoscience, University of Wisconsin, 1215 W. Dayton St., Madison, Wisconsin 53706, USA 3Forschungsinstitut und Naturmuseum Senckenberg, 60325 Frankfurt, Germany 4Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan *Corresponding author. E-mail:
[email protected] (Received 07 April 2010; revision accepted 28 August 2010) Abstract–The Northwest Africa (NWA) 1500 meteorite is an olivine-rich achondrite containing approximately 2–3 vol% augite, 1–2 vol% plagioclase, 1 vol% chromite, and minor orthopyroxene, Cl-apatite, metal and sulfide. It was originally classified as a ureilite, but is currently ungrouped. We re-examined the oxygen three-isotope composition of NWA 1500. Results of ultra-high precision (0.03& for D17O) laser fluorination analyses of two bulk chips, and high precision (0.3&) secondary ion mass spectrometry (SIMS) analyses of olivine and plagioclase in a thin section, show that the oxygen isotope composition of NWA 1500 (D17O=)0.22& from bulk samples and )0.18 ± 0.06& from 16 mineral analyses) is within the range of brachinites. We compare petrologic and geochemical characteristics of NWA 1500 with those of brachinites and other olivine-rich primitive achondrites, including new petrographic, mineral compositional and bulk compositional data for brachinites Hughes 026, Reid 013, NWA 5191, NWA 595, and Brachina.