Sample Petrographic Description
Sample Number | ALH 81025 |
Newsletter | 6,1 |
Location | Allan Hills |
Field Number | 1598 |
Dimensions (cm) | 9.5 x 8.0 x 4.5 |
Weight (g) | 379.00 |
Original Classification | LL3 Chondrite |
Updated Classification | L3.6 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%): 1-41;Ferrosilite (mol%): 3-40 | |
Weathering | |
C | |
Fracturing | |
B | |
Macroscopic Description - Roberta Score | |
Although ALH 81025 is extremely weathered, many clasts, both rounded and irregular, are apparent on the exterior. One notable exterior clast is 7 x 5 mm in diameter. The bottom surface is iridescent brown and covered with squall-like marks. The interior is extensively weathered. | |
Thin Section Description - Brian Mason | |
The section shows a close-packed aggregate of chondrules and chondrule fragments up to 3.5 mm across; in a fine-grained matrix of olivine, pyroxene, troilite, and a little nickel-iron. Chondrule types include porphyritic olivine, granular olivine and olivine-pyroxene, barred olivine, and radiating pyroxene. Much of the pyroxene is polysynthetically twinned clinobronzite. Intergranular glass is present in the chondrules, usually turbid but sometimes transparent and purple-brown. Weathering is extensive, with small areas of brown limonite throughout the section. Microprobe analyses show that olivine and pyroxene have variable composition. Olivine composition ranges from Fa1 to Fa41, with a mean of Fa18 (per cent mean deviation FeO is 76). Pyroxene composition ranges from Fs3 to Fs40, with a mean of Fs15 (per cent mean deviation FeO is 75). Purple glass in a chondrule has the following mean composition (weight per cent): SiO2 56.8, Al2O3 24.1, FeO 3.7, MgO 2.4, CaO 0.4 K2O 4.1, Na2O 8.8, TiO2 1.2, MnO 0.69. The texture and the variable mineral compositions indicate type 3, and the low metal content suggests LL group, hence the meteorite is tentatively classified LL3. It is possibly paired with ALHA79003 (Scott et al., Meteoritics, 17, 65-75, 1982), 81030, 81031, and 81032. | |
Reclassification Notes (AMN OUTSIDE) | |
Classification updated in Meteoritical Bulletin 76. |
Antarctic Meteorite Images for Sample ALH 81025 | ||||
Lab Photo(s) : | ||||
Antarctic Meteorite Images for Sample ALH 81025 | ||||
Thin Section Photo(s) : | ||||
References for Sample ALH81025 | |
Simon, S. B., Sutton, S. R., Grossman, L., 2016, The valence and coordination of titanium in ordinary and enstatite chondrites. Geochimica et Cosmochimica Acta, 189, 377-390. | |
Schultz, L., Franke, L., 2004, Helium, neon, and argon in meteorites: A data collection. Meteoritics & Planetary Science, 39, 1889-1890, http://dx.doi.org/10.1111/j.1945-5100.2004.tb00083.x. | |
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. | |
Sears, D. W. G., Hasan, F. A., Batchelor, J. D., Lu, J., 1991, Chemical and physical studies of type 3 chondrites. XI-Metamorphism, pairing, and brecciation of ordinary chondrites. Proceedings Lunar and Planetary Science Conference, 21, 493-512. | |
Schultz, L., Kruse, H., 1989, Helium, neon, and argon in meteorites—A data compilation. Meteoritics, 24, 155-172. | |
Sears, D. W., Hasan, F. A., 1987, The type three ordinary chondrities: A review. Surveys in geophysics, 9(1), 43-97. | |
Sears, D. W. G., Weeks, K. S., 1986, Chemical and physical studies of type 3 chondrites—VI: Siderophile elements in ordinary chondrites. Geochimica et Cosmochimica Acta, 50 Issue 12, Dec-86, 2815-2832, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(86)90229-2. | |
Marvin, U. B., Mason, B., 1984, Field and laboratory investigations of meteorites from Victoria Land, Antarctica. Smithsonian Contributions to the Earth Sciences Number, 26, 134. |