Sample Petrographic Description
Sample Number | ALH 82100 |
Newsletter | 6,2 |
Location | Allan Hills |
Field Number | 2999 |
Dimensions (cm) | 3.5 x 3.5 x 2.5 |
Weight (g) | 24.30 |
Original Classification | C2 Chondrite |
Updated Classification | CM2 Chondrite |
Pairing | ALH 82100; ALH 82131; ALH 84036; ALH 84039; ALH 84046; ALH 84050; ALH 84053; ALH 90407; ALH 99500; |
Mineral Composition (%Fa & %Fs) | |
Fayalite (mol%): 1-47;Ferrosilite (mol%): 1-2 | |
Weathering | |
A | |
Fracturing | |
A | |
Macroscopic Description - Carol Schwarz | |
Patchy fusion crust occurs mainly on the bottom of this carbonaceous chondrite. Small sub-millimeter inclusions are visible on the exterior surfaces of the stone. There are no fractures. The north face has a rough texture from weathering. The interior is also black with a few very small inclusions. | |
Thin Section Description (,2) - Brian Mason | |
The section shows numerous small colorless grains (up to 0.3 mm) and irregular aggregates (up to 0.6 mm), mainly of olivine, and sparse chondrules, in a black matrix, translucent brown in thinned areas. Trace amounts of nickel-iron and troilite are present as widely dispersed minute grains. Microprobe analyses show olivine compositions in the range Fa1-47, but most grains are low-iron and the mean is Fa5; pyroxene is very rare, two grains of clinoenstatite (Fs1-2 ) being analyzed. The meteorite is a C2 chondrite | |
Reclassification Notes (AMN 17,1) | |
Many carbonaceous chondrites were initially classified as C2 in early newsletters. These are mostly CM2, based on matrix properties, chondrules abundance and sizes, and therefore all these samples have been reclassified more specifically here as CM2. | |
Notes | |
ALH 82100, ALH 82131, and ALH 84036, ALH 84039, ALH 84046, ALH 84050, ALH 84053, ALH 90407, and ALH 99500 are all from the far western icefield; although they have been paired for many years with ALH 81002, the latter is nearly 80 km away and too far to be reasonably paired given the ice flow regimes in that region. Additionally, available observations suggest ALH 99500 was erroneously paired with ALH 83100 - instead we suggest pairing with ALH 82100. AMN 45 no. 2. |
Antarctic Meteorite Images for Sample ALH 82100 | ||||
Lab Photo(s) : | ||||
Antarctic Meteorite Images for Sample ALH 82100 | ||||
Thin Section Photo(s) : | ||||
References for Sample ALH82100 | |
Hiroi, T., Ohtsuka, K., Howard, K.T., Robertson, K.R., and Milliken, R.E., Kaiden, H., Imae, N., Misawa, K., Kojima, H., Sasakia, S., Matsuokaa, M., Nakamura, T., Bish, D.L., 2021, UV-visible-infrared spectral survey of Antarctic carbonaceous chondrite chips. Polar Science, 29, 100723, https://doi.org/10.1016/j.polar.2021.100723. | |
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. | |
Sephton, M. A., Bland, P. A., Pillinger, C. T., Gilmour, I., 2004, The preservation state of organic matter in meteorites from Antarctica. Meteoritics & Planetary Science, 39, 747-754. | |
Benoit, P. H., Sears, D. W. G., Akridge, J. M. C., Bland, P. A., Berry, F. J., Pillinger, C. T., 2000, The non-trivial problem of meteorite pairing. Meteoritics & Planetary Science, 35, 393-417. | |
Grady, M. M., Wright, I. P., Pillinger, C. T., 1991, Comparisons between Antarctic and non-Antarctic meteorites based on carbon isotope geochemistry. Geochimica et Cosmochimica Acta, 55 Issue 1, Jan-91, 49-58, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(91)90398-O. | |
Marvin, U. B., MacPherson, G. J., 1989, Field and Laboratory Investigations of Meteorites from Victoria Land and the Thiel Mountains Region, Antarctica 1982-1983 and 1983-1984. Smithsonian Contributions to the Earth Sciences Number, 28, 146. | |
Scott, E. R. D., 1984, Pairing of meteorites found in Victoria Land, Antarctica. Memoirs of National Institute of Polar Research., Special issue 35, 102-125, http://ci.nii.ac.jp/naid/110000009967/en/. | |
RELAB, , Reflectance Experiment Lab , catalogue of samples. |