Sample Petrographic Description
Sample Number | ALH 81258 |
Newsletter | 8,1 |
Location | Allan Hills |
Field Number | 1651 |
Dimensions (cm) | 1.0 x 1.0 x 0.5 |
Weight (g) | 1.08 |
Original Classification | CV3 Chondrite |
Updated Classification | CV 3.7 Chondrite Oxidized A |
Pairing | ALH 81003; ALH 81258; ALH 84028; |
Mineral Composition (%Fa & %Fs) | |
Fayalite (mol%): 0-28;Ferrosilite (mol%): 0-1 | |
Weathering | |
B | |
Fracturing | |
A/B | |
Macroscopic Description - Roberta Score | |
The stone is mostly covered with a vesicular black fusion crust. | |
Thin Section Description (,1) - Brian Mason | |
The section shows numerous chondrules up to 2 mm across and irregular crystalline aggregates, up to 3 mm in maximum dimension, set in a minor amount of dark brown to black, semi-opaque matrix. The chondrules and aggregates consist mainly of granular olivine with minor amounts of polysynthetically twinned pyroxene. Trace amounts of nickel-iron are present as minute grains. Sulfide is present in small amounts, finely dispersed throughout the matrix and sometimes concentrated in chondrule rims. Microprobe analyses of chondrule olivine show a wide compositional range: Fa0-28, mean Fa11. The matrix appears to consist largely of fine-grained iron-rich olivine, Fa40-60. Pyroxene in the chondrules is clinoenstatite, mostly near Fs1, but with occasional Fe-rich grains. The meteorite is a C3V chondrite, very similar to ALHA81003; the possibility of pairing should be considered. | |
Reclassification Notes (AMN 46,1) | |
Reclassification and pairing based on Raman spectroscopy (petrologic type 3.7), and on Ni content of metal and sulfide and magnetic susceptibility (Oxidized A). Details are reported in Righter et al. (2022); doi: 10.1111/maps.13932. |
Antarctic Meteorite Images for Sample ALH 81258 | ||||
Lab Photo(s) : | ||||
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Antarctic Meteorite Images for Sample ALH 81258 | ||||
Thin Section Photo(s) : | ||||
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References for Sample ALH81258 | |
Righter, K., Neff, K. E., 2007, Temperature and oxygen fugacity constraints on CK and R chondrites and implications for water and oxidation in the early solar system. Polar Science, 1 Issue 1, Aug-07, 25-44, ISSN 1873-9652, http://dx.doi.org/10.1016/j.polar.2007.04.002. | |
Krot, A. N., Hutcheon, I. D., Brearley, A. J., Pravdivtseva, O. V., Petaev, M. I., Hohenberg, C. M., 2006, Timescales and Settings for Alteration of Chondritic Meteorites. Meteorites and the Early Solar System II, D. S. Lauretta and H. Y. McSween Jr. (eds.),. University of Arizona Press, Tucson, 943, 525-553. | |
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. | |
Krot, A. N., Petaev, M. I., Scott, E. R. D., Choi, B.-G., Zolensky, M. E., Keil, K., 1998, Progressive alteration in CV3 chondrites: More evidence for asteroidal alteration. Meteoritics & Planetary Science, 33, 1065-1085. | |
Krot, A. N., Petaev, M. I., Zolensky, M. E., Keil, K., Scott, E. R. D., Nakamura, K., 1998, Secondary calcium-iron-rich minerals in the Bali-like and Allende-like oxidized CV3 chondrites and Allende dark inclusions. Meteoritics & Planetary Science, 33, 623-645. | |
Krot, A. N., Scott, E. R. D., Zolensky, M. E., 1995, Mineralogical and chemical modification of components in CV3 chondrites: Nebular or asteroidal processing?. Meteoritics, 30, 748-775. | |
Scott, E. R. D., Keil, K., Stöffler, D., 1992, Shock metamorphism of carbonaceous chondrites. Geochimica et Cosmochimica Acta, 56 Issue 12, Dec-92, 4281-4293, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(92)90268-N. | |
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. |