40th Lunar and Planetary Science Conference (2009) 1682.pdf NOBLE GAS DISTRIBUTIONS IN THE YAMATO 000593 NAKHLITE DECIPHERED BY LASER ABLATION ANALYSIS AND MINERAL SEPARATION. K. Nagao1, J. Park2, R. Okazaki3, N. Imae4 and H. Kojima4. 1Laboratory for Earthquake Chemistry, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan (
[email protected]), 2ARES, NASA, Johnson Space Center, Houston, TX 77058, USA, 3Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Hakozaki, Fukuoka 812-8581, Japan, 4Antarctic Meteorite Research Center, National Institute of Polar Research, Kaga 1-chome, Itabashi-ku, Tokyo 173-8515, Japan. Introduction: Three meteorites Yamato (Y) steps from 400 to 1800ºC) was applied to the mineral 000593 (13.7 kg), Y000749 (1.3 kg) and Y000802 (22 separates; olivine (75.5 mg), plagioclase (18.1 mg), g) were discovered in Yamato ice field in Antarctica and pyroxene (187.9 mg). However, noble gases ex- by the Japanese Antarctic Research Expedition in 2000 tracted from olivine and plagioclase at 1800ºC gave (JARE-41). They were recognized as paired nakhlites meaningless results due to small amounts of extracted from view points of petrological and mineralogical noble gases, which were comparable with blank levels. observations as well as recovered locations [1]. For noble gas extraction by laser microprobe (Nd- Nakhlites are cumulates [2] and consist of mostly YAG pulse laser, 1064 nm), a meteorite plate with magnesian augite, microcrystalline mesostasis and ~300 µm thick was used. Optical microprobe and smaller amounts of Fe-rich olivine. Parent magma for Scanning electron microprobe observations on the nakhlites may be different from shergottites, because polished surface of the plate showed abundant nakhlites have high volatile contents, in contrast to mesostasis, probably weathering products, while id- shergottites, but are LREE-enriched [3].