The Antarctic achondrite,Grove Mountains 021663: An olivine‐rich winonaite |
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| Authors: | Shijie LI Shijie WANG Huiming BAO Bingkui MIAO Shen LIU Ian M COULSON Xiongyao LI Yang LI |
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| Institution: | 1. Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;2. Department of Geology and Geophysics, E235 Howe‐Russell Geoscience Complex, Louisiana State University, Baton Rouge, LA 70803‐4101, USA;3. Department of Resources and Environmental Engineering, Guilin Institute of Technology, Guilin 541004, China;4. Solid Earth Studies Laboratory, Department of Geology, The University of Regina, Regina, Saskatchewan, Canada S4S 0A2;5. Graduate University of the Chinese Academy of Sciences, Beijing 100039, China |
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| Abstract: | Abstract– The Grove Mountains (GRV) 021663 meteorite was collected from the Grove Mountains region of Antarctica. The meteorite is composed primarily of olivine (Fa5.4), orthopyroxene (Fs4.7Wo3.0), chromian diopside (En53.6Fs2.4Wo44), troilite, kamacite, and plagioclase (Ab74.5Or4An21.5). Minor phases include schreibersite and K‐feldspar. The meteorite is highly weathered (W3) and weakly shocked (S2). We determine a whole rock oxygen isotopic composition of δ18O = 7.50‰, δ17O = 3.52‰. Comparisons of these data with other primitive achondrites have resulted in the reclassification of this meteorite as a member of the winonaite group. The occurrences of troilite, metal, and schreibersite in GRV 021663 indicate that these minerals were once completely molten. Euhedral inclusions of pyroxene within plagioclase further suggest that these may have crystallized from a silicate melt, while the depletion of plagioclase, metal, and troilite indicates that GRV 021663 could represent a residuum following partial melting on its parent asteroid. Trace element distributions in silicate minerals do not, however, confirm this scenario. As with other winonaite meteorites, the formation of GRV 021663 probably relates to brecciation and mixing of heterogeneous lithologies, followed by varying degrees of thermal metamorphism on the parent body asteroid. Peak metamorphic conditions may have resulted in localized partial melting of metal and silicate mineralogies, but our data are not conclusive. |
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