Sample Petrographic Description
Sample Number | GRO 95633 |
Newsletter | 20,2 |
Location | Grosvenor Mountains |
Field Number | 9898 |
Dimensions (cm) | 4.7 x 2.5 x 3.0 |
Weight (g) | 58.10 |
Original Classification | Eucrite (Brecciated) |
Updated Classification | Howardite |
Mineral Composition (%Fa & %Fs) | |
Ferrosilite (mol%): 32-57 | |
Weathering | |
B | |
Fracturing | |
A/B | |
Macroscopic Description - Cecilia Satterwhite | |
95% of the exterior of this achondrite is covered by shiny, black fusion crust. The fusion crust appears glassy in some areas. The interior reveals a complex breccia consisting of a wide variety of clasts in a light gray matrix. The largest clasts are fine grained dark gray melts. There is one large white (plagioclase) clast and several coarse grained yellow-green mineral clasts. Some areas are mottled with black and white patches. Some oxidation is scattered in the interior but is heavier along the edges. | |
Thin Section Description (,3) - Brian Mason | |
The section shows a microbreccia of plagioclase clasts (up to 1.8 mm) and basaltic fragments in a groundmass of comminuted plagioclase and dark brown glass. A few metal grains are present, surrounded by brown limonitic staining. Plagioclase composition is fairly uniform, An91-92; pyroxene composition in a basaltic clast ranges from Wo5Fs32 to Wo2Fs57. The meteorite is a brecciated eucrite. | |
Reclassification Notes (AMN 33,1) | |
Original classification in AMN 20, no. 2, as a brecciated eucrite. Subsequent studies and numerous thin sections reveal various eucritic lithologies and also orthopyroxene. Bulk compositions of [1] Mittlefehldt and Lindstrom, 2003 and [2] Okamoto et al. (2004) indicate clear >10% mixture of diogenitic material with the eucritic material. Therefore this sample is reclassified as a howardite. References:
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Antarctic Meteorite Images for Sample GRO 95633 | ||||
Lab Photo(s) : | ||||
Antarctic Meteorite Images for Sample GRO 95633 | ||||
Thin Section Photo(s) : | ||||
References for Sample GRO95633 | |
Shirai, N., Okamoto, C., Yamaguchi, A., Ebihara, M., 2016, Siderophile elements in brecciated HED meteorites and the nature of projectile materials in HED meteorites. Earth and Planetary Science Letters, 437, 57-65. | |
Mittlefehldt, D. W., 2015, Asteroid (4) Vesta: I. The howardite-eucrite-diogenite (HED) clan of meteorites. Chemie der Erde - Geochemistry, 75 Issue 2, Jun-15, 155-183, ISSN 0009-2819, http://dx.doi.org/10.1016/j.chemer.2014.08.002. | |
Mittlefehldt, D. W., Lindstrom, M. M., 2003, Geochemistry of eucrites: genesis of basaltic eucrites, and Hf and Ta as petrogenetic indicators for altered antarctic eucrites. Geochimica et Cosmochimica Acta, 67 Issue 10, 15-May-03, 1911-1934, ISSN 0016-7037, http://dx.doi.org/10.1016/S0016-7037(02)01411-4. | |
RELAB, , Reflectance Experiment Lab , catalogue of samples. |