Sample Petrographic Description
Sample Number | ALH 77140 |
Newsletter | 1,2 |
Location | Allan Hills |
Field Number | Y77123124 |
Dimensions (cm) | 4.6 x 3.3 x 3.0 |
Weight (g) | 78.62 |
Original Classification | L3 Chondrite |
Updated Classification | L3.5 Chondrite |
Pairing | ALH 77011; ALH 77015; ALH 77031; ALH 77033; ALH 77034; ALH 77036; ALH 77043; ALH 77047; ALH 77049; ALH 77050; ALH 77052; ALH 77115; ALH 77140; ALH 77160; ALH 77163; ALH 77164; ALH 77165; ALH 77166; ALH 77167; ALH 77170; ALH 77175; ALH 77178; ALH 77185; ALH 77211; ALH 77214; ALH 77241; ALH 77244; ALH 77249; ALH 77260; ALH 77303; ALH 78013; ALH 78015; ALH 78017; ALH 78037; ALH 78038; ALH 78041; ALH 78162; ALH 78170; ALH 78176; ALH 78180; ALH 78186; ALH 78188; ALH 78235; ALH 78236; ALH 78238; ALH 78239; ALH 78243; ALH 79001; ALH 79045; ALH 80133; ALH 81025; ALH 81030; ALH 81031; ALH 81032; ALH 81053; ALH 81060; ALH 81061; ALH 81065; ALH 81066; ALH 81069; ALH 81085; ALH 81087; ALH 81121; ALH 81145; ALH 81156; ALH 81162; ALH 81190; ALH 81191; ALH 81214; ALH 81229; ALH 81243; ALH 81259; ALH 81272; ALH 81280; ALH 81292; ALH 81299; ALH 83038; ALH 85155; |
Mineral Composition (%Fa & %Fs) | |
Fayalite (mol%): 8-44;Ferrosilite (mol%): 2-17 | |
Weathering | |
Ce | |
Fracturing | |
B | |
Macroscopic Description - | |
The specimen is roughly conical shaped. The basal portion is irregular and appears to be a broken surface. The remainder of the meteorite's surface is only slightly pitted and is suggestive of a fusion crust. The entire meteorite is a dark reddish-brown with considerable rust-like staining. The extensive weathering of the stone has apparently removed or altered most of the fusion crust. | |
Thin Section Description - Brian Mason | |
The section examined consists of an elliptical non-chondritic enclave, 8 x 5 mm, completely enclosed in highly chondritic material. The enclave consists of polysynthetically-twinned clinoenstatite (somewhat variable composition, averaging Wo0.2Fs7En93) poikilitically enclosing irregular to globular isotropic or weakly anisotropic masses. These masses have variable composition (SiO2 59-83%, FeO 15-31%, MgO 5-9%, K2O 2.7-4.3%, Na2O 0.6-2.6%, Al2O3 ~0.3%, CaO, TiO2, <0.1%); they appear to be devitrified glass, and some analyses are close to that of merrihueite. The enclave has a little interstitial nickel-iron and troilite. The chondritic portion consists of a close-packed mass of chondrules, with a relatively small amount of fine-grained matrix. Chondrules range in diameter from 0.2 to 2 mm, and exhibit a variety of form and structure; the component consists of granular aggregates of olivine and polysynthetically-twinned clinopyroxene, sometimes with a little interstitial glass. Both olivine and clinopyroxene are highly variable in composition. Olivine ranges from Fa8 to Fa44, with an average of Fa25; pyroxene ranges from Fs2 to Fs17, with an average of Fs7 and a low calcium content, averaging 0.2% CaO. Troilite and nickel-iron are interstitial to the chondrules, and part of the nickel-iron has weathered to limonitic material. The highly variable composition of olivine and pyroxene indicates a type 3 chondrite, and the mean composition of the olivine and the amount of nickel-iron suggest L group, so the meteorite is tentatively classified L3; however, certain assignment of group should await further investigation. |
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Reclassification Notes (AMN OUTSIDE) | |
Classification updated in Meteoritical Bulletin 76. |
Antarctic Meteorite Images for Sample ALH 77140 | ||||
Thin Section Photo(s) : | ||||
References for Sample ALH77140 | |
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. | |
Velbel, M. A., 1988, The Distribution and Significance of Evaporitic Weathering Products on Antarctic Meteorites. Meteoritics, 23, 151-159. | |
Evans, J. C., Reeves, J. H., 1987, 26Al survey of Antarctic meteorites. Earth and Planetary Science Letters, 82 Issues 3-4, Apr-87, 223-230, ISSN 0012-821X, http://dx.doi.org/10.1016/0012-821X(87)90197-X. | |
Marvin, U. B., Mason, B., 1980, Catalog of Antarctic Meteorites 1977-1978. Smithsonian Contributions to the Earth Sciences, Number 23, 50. |