Sample Petrographic Description
Sample Number | EET 99400 |
Newsletter | 23,2 |
Location | Elephant Moraine |
Field Number | 12322 |
Dimensions (cm) | 7.5 x 4.5 x 3.5 |
Weight (g) | 233.80 |
Original Classification | Howardite |
Pairing | EET 87509; EET 83376; EET 87510; EET 87518; EET 87531; EET 87532; EET 92022; EET 99400; EET 99408; |
Mineral Composition (%Fa & %Fs) | |
Ferrosilite (mol%): 17-22 | |
Weathering | |
B | |
Fracturing | |
B | |
Macroscopic Description - Kathleen McBride | |
Both of these achondrites have black shiny fusion crust with polygonal fractures covering 20% of the exterior. The interior is concrete gray with angular to sub angular black, white, tan and gray clasts. Olivine crystals are visible. There is no visible metal, but thin minor fractures are present. | |
Thin Section Description (,5) - Tim McCoy | |
These meteorites are so similar that a single description suffices. The sections show a groundmass of comminuted pyroxene and plagioclase (up to 0.5 mm) with fine- to coarse-grained basaltic and pyroxenitic clasts ranging up to 1 mm. Pyroxene consists of orthopyroxene (Fs17-27Wo0-1), pigeonite (Fs42-50Wo13-15) and augite (Fs24Wo37). The Fe/Mn ratio of pyroxene is ~30. Plagioclase is An80-94Or0-1. The meteorites are howardites. | |
Notes | |
An initially defined pairing group (e.g., AMN 11, 2) consisting of EET 87503, EET 87509, EET 87510, EET 87512, EET 87518, and EET 87531 has been re-evaluated by Mittlefehldt et al. (2013). Based on petrography, mineralogy, petrology, bulk composition, and find locations, EET 87503 was removed from this group (and instead paired with EET 87513), and EET 87512 was removed from this group to be unpaired. The original group also gained EET 92002, EET 83376 (previously unpaired), EET 87532 (previously unpaired), and two from 1999 field season EET 99400 and EET 99408. Thus, the newly revised pairing groups are EET 87503 (503 and 513) and EET 87509 (EET 87509, EET 87510, EET 87518, and EET 87531, EET 87532, EET 83376, EET 92022, EET 99400 and EET 99408). EET 87512 is unpaired. |
Antarctic Meteorite Images for Sample EET 99400 | ||||
Lab Photo(s) : | ||||
References for Sample EET99400 | |
Moriarty, D. P., Pieters, C. M., 2016, Complexities in pyroxene compositions derived from absorption band centers: Examples from Apollo samples, HED meteorites, synthetic pure pyroxenes, and remote sensing data. Meteoritics & Planetary Science, 51(2), 207-234. | |
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. | |
Cartwright, J. A., Ott, U., Mittlefehldt, D. W., 2014, The Quest for Regolithic Howardites Part 2: Surface Origins Highlighted by Noble Gases. Geochimica et Cosmochimica Acta, 140, 488-508. | |
Mittlefehldt, D. W., Herrin, J. S., Quinn, J. E., Mertzman, S. A., Cartwright, J. A., Mertzman, K. R., Peng, Z. X., 2013, Composition and petrology of HED polymict breccias: The regolith of (4) Vesta. Meteoritics & Planetary Science, 48, 2105-2134, http://dx.doi.org/10.1111/maps.12182. | |
RELAB, , Reflectance Experiment Lab , catalogue of samples. |