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Allan Hills A77140
Basic information Name: Allan Hills A77140
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77140
This meteorite may also be called Allan Hills 77140 (ALH 77140) in publications.

Observed fall: No
Year found: 1977
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 78.6 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 1(2)  (1978)  L3
Meteoritical Bulletin:  MB 76  (1994)  L3
NHM Catalogue:  5th Edition  (2000)  L3
NIPR Catalogue:  2000 Edition  (2000)  L3
MetBase:  v. 7.1  (2006)  L3.5
Recommended:  L3.5    [explanation]

This is 1 of 95 approved meteorites classified as L3.5.   [show all]
Search for other: L chondrites, L chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Writeuphelp
Writeup from AMN 4(1):

Sample No.: ALHA77140

Location: Allan Hills

Field No.: Y77123124

Weight (gms): 78.62

Meteorite Type: Tentatively L3 Chondrite

 

Physical 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.

 

Petrographic Description: Brian Mason

The section examined consists of an elliptical non-chondritic enclave, 8x5 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.

Data from:
  MB76
  Table 2
  Line 110:
Origin or pseudonym:Main icefield
Mass (g):78.6
Class:L3
Weathering grade:Ce
Fayalite (mol%):8-44
Ferrosilite (mol%):2-17
Comments:26Al=40±4; 77011 pairing group
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 4(1) (1981), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (76° 43'S, 159° 40'E)
     Recommended::   (76° 43'S, 159° 40'E)

Statistics:
     This is 1 of 39173 approved meteorites from Antarctica (plus 5051 unapproved names)
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