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| Allan Hills A81001 | |||||||||||||||||||||||||||||||||
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| Basic information | Name: Allan Hills A81001 This is an OFFICIAL meteorite name. Abbreviation: ALHA81001 This meteorite may also be called Allan Hills 81001 (ALH 81001) in publications. Observed fall: No Year found: 1981 Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)] Mass:  52.9 g | ||||||||||||||||||||||||||||||||
| Classification history: |
This is 1 of 131 approved meteorites classified as Eucrite-unbr. [show all] Search for other: Achondrites, Eucrites, and HED achondrites | ||||||||||||||||||||||||||||||||
| Writeup |
Writeup from AMN 6(1):
Sample No.: ALHA81001 Location: Allan Hills Field No.: 1505 Weight (gms): 52.9 Meteorite Type: Eucrite (anomalous)
Physical Description: Roberta Score This achondrite is covered on two surfaces with a shiny black fusion crust. The interior appears massive and is a smokey gray color. Many cracks penetrate the interior of this meteorite. After drying in a nitrogen cabinet for several hours, a minute amount of white deposit lines one crack. Dimensions: 4.5 x 4.0 x 4.5 cm.
Petrographic Description: Brian Mason The section is translucent in pale brown-gray, with some darker areas, giving a patchy appearance. With crossed polars the material is seen to consist of pyroxene prisms up to 0.5 mm long, mostly with straight extinction, in a glassy groundmass. No opaque minerals are present. Microprobe analyses show the pyroxene has rather uniform composition, averaging Wol.6En40Fs59 , with 0.4% A12O3, 0.2% TiO2, 0.9% MnO, and 0.6% Cr2O3. Broad-beam analyses give an approximate bulk composition (weight percent) as follows: SiO2 49, Al2O3 14, FeO 18, MgO 6.7, CaO 10, Na2O 0.2, K2O <0.1, TiO2 0.9, Cr2O3 0.6, MnO 0.7. This composition agrees with that of an average eucrite, except that Na2O is lower (in most eucrites Na2O is about 0.5%); however, the texture is quite different from any described eucrite. The overall impression from the texture is that the material represents a rapidly quenched melt. Writeup from AMN 33(1):
ALHA81001
original classification in AMN 6, no. 1, as an anomalous eucrite. Later
reclassified in AMN 17, no. 1, as a polymict eucrite. Numerous thin sections
reveal no brecciation and subsequent chemical and textural studies [1, 2, 3] all suggest reclassification as
unbrecciated eucrite.
[1] P.H.Warren et al., Papers 21st Symp. Ant. Met., NIPR Tokyo, 1996, p.195 [2] Mittlefehldt, D.W., and Lindstrom, M.M. (2003) Geochemistry of eucrites: Genesis of basaltic eucrites, and Hf and Ta as petrogenetic indicators for altered Antarctic eucrites. Geochimica et Cosmochimica Acta, 67, no. 10, 1911-1935. [3] Mayne, R.G., McSween, Jr., H.Y., McCoy, T.J., and Gale, A., (2009) Petrology of the unbrecciated eucrites. Geochimica et Cosmochimica Acta, 73, 794-819. | ||||||||||||||||||||||||||||||||
| Data from: MB76 Table 2 Line 524: |
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| References: | Published in Antarctic Meteorite Newsletter 33(1) (2010), JSC, Houston Published in Antarctic Meteorite Newsletter 6(1) (1983), JSC, Houston Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Geography:
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Statistics: This is 1 of 44248 approved meteorites from Antarctica (plus 3802 unapproved names) | ||||||||||||||||||||||||||||||||
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