Sample Petrographic Description
Sample Number | MIL 090340 |
Newsletter | 34,1 |
Location | Miller Range |
Field Number | 20519 |
Dimensions (cm) | 1.5 x 1.25 x 1.25 |
Weight (g) | 4.69 |
Original Classification | Ureilite |
Updated Classification | Achon. Ungrouped |
Pairing | MIL 090405; MIL 090206; MIL 090340; MIL 090356; MIL 090805; MIL 090963; |
Mineral Composition (%Fa & %Fs) | |
Fayalite (mol%): 27-30 | |
Weathering | |
C | |
Fracturing | |
A/B | |
Macroscopic Description - Kathleen McBride | |
The exteriors have shiny dark brown fusion crust with some rusty patches and pits. The interiors are dark gray to black with crystalline textures, rust and high metal. | |
Thin Section Description (,2) - Cari Corrigan, Linda Welzenbach | |
These sections consist of an aggregate of equigranular (up to 1-2 mm) olivine grains. Individual olivine grains are rimmed by carbon-rich material containing grains of metal. Olivine has cores of Fa27-30. Pyroxene grains have compositions of Fs10-26 and Wo2-44. These meteorites are ureilites. | |
Reclassification Notes (AMN 35,2) | |
Four previously announced MIL samples that have been classified as “ureilite” (MIL 090340, 090356, 090206, 090805), are being reclassified here to “ungrouped achondrite”. They are all very similar to two additional samples — MIL 090963 and MIL 090405 — and may instead represent 6 meteorites that are related to brachinites, based on Ca and Cr content of the olivines, O– isotopes, and olivine rim mineralogy (e.g., Warren and Rubin, 2012, LPSC abstract #2528; Goodrich et al., 2012, MetSoc abstract #5272). Although these meteorites may be related to brachinites, they are not true brachinites and so the classification “ungrouped achondrite” will be used until a further change is necessary. We specifically want to call attention to the fact that they are not ureilites so that researchers will not mistakenly request them as such. Concomitantly, we feel that researchers who are interested in brachinites may find these samples of interest and may not have noticed them previously due to the ureilite label. |
Antarctic Meteorite Images for Sample MIL 090340 | ||||
Lab Photo(s) : | ||||
Antarctic Meteorite Images for Sample MIL 090340 | ||||
Thin Section Photo(s) : | ||||
References for Sample MIL090340 | |
Day, J. M., Corder, C. A., Assayag, N., & Cartigny, P., 2019, Ferrous oxide-rich asteroid achondrites. Geochimica et Cosmochimica Acta, 266, 544-567, https://doi.org/10.1016/j.gca.2019.04.005. | |
Hasegawa, H., Mikouchi, T., Yamaguchi, A., Yasutake, M., Greenwood, R. C., & Franchi, I. A., 2019, Petrological, petrofabric, and oxygen isotopic study of five ungrouped meteorites related to brachinites. Meteoritics & Planetary Science, 54, 752-767. | |
Goodrich, C. A., Kita, N. T., Sutton, S. R., Wirick, S., & Gross, J. , 2017, The Miller Range 090340 and 090206 meteorites: Identification of new brachinite?like achondrites with implications for the diversity and petrogenesis of the brachinite clan. . Meteoritics & Planetary Science, 52, 949-978, doi: 10.1111/maps.12846. | |
Greenwood, R. C., Burbine, T. H., Miller, M. F., & Franchi, I. A. , 2017, Melting and differentiation of early-formed asteroids: The perspective from high precision oxygen isotope studies. . Chemie Der Erde-Geochemistry, 77, 1-43, http://dx.doi.org/10.1016/j.chemer.2016.09.005. |