Sample Petrographic Description
Sample Number | ALH 78100 |
Newsletter | 4,1 |
Location | Allan Hills |
Field Number | 439 |
Dimensions (cm) | 5.0 x 4.5 x 0.9 |
Weight (g) | 84.95 |
Original Classification | Iron-Group IIA |
Updated Classification | Iron-IIAB |
Pairing | ALH 78100; ALH 81013; |
Macroscopic Description - Roy S. Clarke, Jr. | |
This specimen is a thin, flat, slightly irregular plate, 5 cm x 4.5 cm x 0.9 cm. It appears to be an individual that was oriented during atmospheric flight. The anterior surface is rounded at the edges and the posterior surface is flat. Weathering may have been a factor in shaping as the posterior surface is more heavily weathered than the anterior. The posterior surface is covered with an essentially featureless reddish brown oxide. The anterior surface is also oxide covered, but it contains numerous 1 to 2 mm pockmarks. Both surfaces are tool marked from an attempt to cleave the specimen. | |
Thin Section Description - Roy S. Clarke, Jr. | |
A microetched median section of approximately 3 cm of surface area was examined. It is single crystal kamacite containing Neumann bands and inclusions. Schreibersite is abundant as rhabdites, and is also present as lamellar schreibersite and as hieroglyphic schreibersite surrounding troilite-daubreelite inclusions. Troilite-daubreelite inclusions are also present with only small bordering schreibersites. The anterior surface edge has an ablation rim of α2 averaging about 0.7 mm wide. No α2 was observed on the posterior surface. Fusion crust was not present, and surfaces are covered with terrestrial oxide up to 0.25 mm thick. The specimen appears to be a hexahedrite or Group IIA meteorite. | |
Reclassification Notes (AMN OUTSIDE) | |
ALH 78100 was re-classified to IIAB based on the work of Wasson, J. T., Huber, H., Malvin, D. J., 2007, Formation of IIAB iron meteorites. Geochimica et Cosmochimica Acta, 71, 760-781. |
Antarctic Meteorite Images for Sample ALH 78100 | ||||
Lab Photo(s) : | ||||
References for Sample ALH78100 | |
Rubin, A. E., 2018, Carbonaceous and noncarbonaceous iron meteorites: Differences in chemical, physical, and collective properties. Meteoritics & Planetary Science, 53, 2357–2371. | |
Wasson, J. T., Huber, H., Malvin, D. J., 2007, Formation of IIAB iron meteorites. Geochimica et Cosmochimica Acta, 71 Issue 3, 1-Feb-07, 760-781, ISSN 0016-7037, http://dx.doi.org/10.1016/j.gca.2006.09.032. | |
Jarosewich, E., 1990, Chemical analyses of meteorites: A compilation of stony and iron meteorite analyses. Meteoritics, 25, 323-337. | |
Nishiizumi, K., Elmore, D., Kubik, P. W., 1989, Update on terrestrial ages of Antarctic meteorites. Earth and Planetary Science Letters, 93(3), 299-313. | |
Malvin, D. J., Wang, D., Wasson, J. T., 1984, Chemical classification of iron meteorites—X. Multielement studies of 43 irons, resolution of group IIIE from IIIAB, and evaluation of Cu as a taxonomic parameter. Geochimica et Cosmochimica Acta, 48 Issue 4, Apr-84, 785-804, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(84)90101-7. | |
Marvin, U. B., Mason, B., 1982, Catalog of Meteorites from Victoria Land, Antarctica 1978-1980. Smithsonian Contributions to the Earth Sciences, 24, 97. |