Sample Petrographic Description
Sample Number | EET 99407 |
Newsletter | 23,2 |
Location | Elephant Moraine |
Field Number | 12346 |
Dimensions (cm) | 4.5 x 3.0 x 2.0 |
Weight (g) | 60.04 |
Original Classification | Brachinite |
Pairing | EET 99402; EET 99407; |
Mineral Composition (%Fa & %Fs) | |
Fayalite (mol%): 35 | |
Weathering | |
B | |
Fracturing | |
B | |
Macroscopic Description - Kathleen McBride | |
Both of these meteorites' exterior surfaces are rough, black and granular in appearance. EET99407 has some gray-black fusion crust. The interiors have a granular crystalline texture that is somewhat friable. The matrix is gray to black in color with dark gray crystalline mineral grains cemented by fine rusty material. Some areas appear like they've been melted together. | |
Thin Section Description (,4) - Tim McCoy | |
These meteorites are so similar that a single description suffices. The sections are composed dominantly of equant olivine (Fa35; 0.2-1.5 mm in diameter) with 120º triple junctions. Calcic pyroxene (Fs10-12; Wo43-46) and plagioclase (An38-40; Or0.1-0.3) comprise a few percent of the meteorite each and are heterogeneously distributed. Minor chromite and iron sulfides are also present. The rocks are moderately shocked, with planar fractures in olivine and mosaicism in feldspar. The meteorites are probably brachinites. | |
Oxygen Isotopic Composition - T. K. Mayeda, Robert N. Clayton | |
Our analysis for EET 99402 gives: delta-18=+3.57, delta-17=+1.65. This is indistinguishable from Brachina, for which the values are: +3.48, +1.61 (Clayton and Mayeda, 1996). |
Antarctic Meteorite Images for Sample EET 99407 | ||||
Lab Photo(s) : | ||||
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References for Sample EET99407 | |
Mittlefehldt, D.W., and McCoy, T.J., 2015, Achondrites and Irons: Products of Magmatism on Strongly Heated Asteroids. 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. 79-99. | |
Day, J.M.D., Corder, C.A., Rumble III, D., Assayag, N., Cartigny, P., and Taylor, L.A., 2015, Differentiation processes in FeO-rich asteroids revealed by the achondrite Lewis Cliff 88763, Meteoritics & Planetary Science, 50, 1750-1766, doi:10.111/maps.12509. | |
Keil, K., 2014, Brachinite meteorites: Partial melt residues from an FeO-rich asteroid. Chemie der Erde - Geochemistry, 74, 311-329, ISSN 0009-2819, http://dx.doi.org/10.1016/j.chemer.2014.02.001. | |
Greenwood, R. C., Franchi, I. A., Gibson, J. M., Benedix, G. K., 2012, Oxygen isotope variation in primitive achondrites: The influence of primordial, asteroidal and terrestrial processes. Geochimica et Cosmochimica Acta, 94, 1-Oct-12, 146-163, ISSN 0016-7037, http://dx.doi.org/10.1016/j.gca.2012.06.025. | |
Day, J. M. D., Taylor, L. A., Walker, R. J., Ash, R. D., Liu, Y., Rumble III, D., Irving, A. J., Goodrich, C. A., Tait, K., McDonough, W. F., 2012, Origin of felsic achondrites Graves Nunataks 06128 and 06129, and ultramafic brachinites and brachinite-like achondrites by partial melting of volatile-rich primitive parent bodies. Geochimica et Cosmochimica Acta, 81, 15-Mar-12, 94-128, ISSN 0016-7037, http://dx.doi.org/10.1016/j.gca.2011.12.017. | |
Rochette, P., Gattacceca, J., Bourot-Denise, M., Consolmagno, G., Folco, L., Kohout, T., Pesonen, L., Sagnotti, L., 2009, Magnetic classification of stony meteorites: 3. Achondrites. Meteoritics & Planetary Science, 44, 405-427, http://dx.doi.org/10.1111/j.1945-5100.2009.tb00741.x. | |
Mittlefehldt, D. W., Bogard, D. D., Berkley, J. L., Garrison, D. H., 2003, Brachinites: Igneous rocks from a differentiated asteroid. Meteoritics & Planetary Science, 38, 1601-1625. |