Sample Petrographic Description
| Sample Number | GRO 95551 |
| Newsletter | 20,2 |
| Location | Grosvenor Mountains |
| Field Number | 10945 |
| Dimensions (cm) | 6.5 x 4.0 x 4.0 |
| Weight (g) | 213.39 |
| Original Classification | Chondrite (Anomalous) |
| Updated Classification | Chondrite Ungrouped |
| Mineral Composition (%Fa & %Fs) | |
| Fayalite (mol%): 1-2;Ferrosilite (mol%): 1 | |
| Weathering | |
| C | |
| Fracturing | |
| A | |
| Macroscopic Description - Kathleen McBride | |
| The exterior of this unusual meteorite has thin patches of black fusion crust. Most of the surface has a rusty brown melted appearance with exposed clasts. The clasts are large, rounded and greenish-white with coarse crystalline textures. The interior is rusty and heavily weathered. A variety of inclusions are visible, some are black, very fine-grained and angular. There are a number of rounded objects less then 2-3 mm that could be chondrules. One large clast is greenish-yellow in color, others are rusty. This meteorite was very coherent and difficult to break. | |
| Thin Section Description (,2 ,11 ,13 ,15) - Brian Mason | |
| The sections show a breccia of two types of clasts, chondritic and achondritic. The chondritic clasts range up to 15+ mm, and consist of a variety of chondrules and chondrule fragments (up to 1.8 mm across) in a matrix of nickel-iron with minor troilite. Microprobe analyses of the chondrules gave the following compositions: olivine, Fa1-2; pyroxene, Fs1, with a few more iron-rich grains. The nickel-iron contains no silicon. The achondritic clasts are up to 11 mm across and consist of highly-shocked enstatite (or clinoenstatite). GRO 95551,15 contains a fine-grained carbonaceous clast, 3.6 mm across. The meteorite is anomalous, and resembles Bencubbin (Geochim. Cosmochim. Acta, v.42, p.507, 1978) and Weatherford (Geochim, Cosmochim, Acta, v.32, p.661, 1968). | |
| Reclassification Notes (AMN OUTSIDE) | |
| GRO 95551 has similar mineralogy, petrology, and textures to bencubbinites, but has distinctly different oxygen isotopic composition. Because of these anomalous one-of-a-kind properties, GRO 95551 was re-classified as an ungrouped chondrite. See Weisberg, M. K., Prinz, M., Clayton, R. N., Mayeda, T. K., Sugiura, N., Zashu, S., & Ebihara, M. (2001). A new metal‐rich chondrite grouplet. Meteoritics & Planetary Science, 36(3), 401-418. | |
| Antarctic Meteorite Images for Sample GRO 95551 | ||||
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| Antarctic Meteorite Images for Sample GRO 95551 | ||||
| Thin Section Photo(s) : | ||||
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| References for Sample GRO95551 | |
| Greenwood, R.C., Burbine, T.H., and Franchi, I.A., 2020, Linking Asteroids and meteorites to the primordial planetesimal population. Geochimica et Cosmochimica Acta, 277, 377-406, doi: 10.1016/j.gca.2020.02.004. | |
| Rotelli, L., Trigo-Rodríguez, J. M., Moyano-Cambero, C. E., Carota, E., Botta, L., Di Mauro, E., & Saladino, R., 2016, The key role of meteorites in the formation of relevant prebiotic molecules in a formamide/water environment. Scientific reports, 6, 38888. | |
| Weisberg, M. K., Ebel, D. S., Nakashima, D., Kita, N. T., & Humayun, M., 2015, Petrology and geochemistry of chondrules and metal in NWA 5492 and GRO 95551: A new type of metal-rich chondrite. Geochimica et Cosmochimica Acta, 167, 269-285. | |
| Weisberg, M.K., and Righter, K., 2015, Primitive Asteroids: Expanding the Range of Known Primitive Materials. In Righter, K., Corrigan, C.M., McCoy, T.J., and Harvey, R.P. Meteorites: A Pictorial Guide to the Collection, First Edition, AGU Wiley, pp. 65-77. | |
| Allen, C., Allton, J., Lofgren, G., Righter, K., Zolensky, M. E., 2011, Curating NASA's extraterrestrial samples-Past, present, and future. Chemie der Erde - Geochemistry, 71 Issue 1, 2011, 1-20, ISSN 0009-2819, http://dx.doi.org/10.1016/j.chemer.2010.12.003. | |
| Qin, L., Alexander, C. M. O'D., Carlson, R. W., Horan, M. F., Yokoyama, T., 2010, Contributors to chromium isotope variation of meteorites. Geochimica et Cosmochimica Acta, 74 Issue 3, 1-Feb-10, 1122-1145, ISSN 0016-7037, http://dx.doi.org/10.1016/j.gca.2009.11.005. | |
| Rochette, P., Kohout, T., Pesonen, L., Quirico, E., Sagnotti, L., Skripnik, A., Gattacceca, J., Bonal, L., Bourot-Denise, M., Chevrier, V., Clerc, J. P., Consolmagno, G., Folco, L., Gounelle, M., 2008, Magnetic classification of stony meteorites: 2. Non-ordinary chondrites. Meteoritics & Planetary Science, 43, 959-980, http://dx.doi.org/10.1111/j.1945-5100.2008.tb01092.x. | |
| Schultz, L., Franke, L., 2004, Helium, neon, and argon in meteorites: A data collection. Meteoritics & Planetary Science, 39, 1889-1890, http://dx.doi.org/10.1111/j.1945-5100.2004.tb00083.x. | |
| Campbell, A. J., Humayun, M., 2003, Formation of metal in Grosvenor Mountains 95551 and comparison to ordinary chondrites. Geochimica et Cosmochimica Acta, 67 Issue 13, 1-Jul-03, 2481-2495, ISSN 0016-7037, http://dx.doi.org/10.1016/S0016-7037(02)01405-9. | |
| Sugiura, N., Zashu, S., Weisberg, M. K., Prinz, M., 2000, A nitrogen isotope study of bencubbinites. Meteoritics & Planetary Science, 35, 987-996. | |
| , PLATE Preface-Pictorial Guide to Selected Meteorites, 2015, In Righter, K., Corrigan, C.M., McCoy, T.J., and Harvey, R.P. Meteorites: A Pictorial Guide to the Collection, First Edition, AGU Wiley, Book Plates. | |