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Elephant Moraine 83333
Basic information Name: Elephant Moraine 83333
     This is an OFFICIAL meteorite name.
Abbreviation: EET 83333
Observed fall: No
Year found: 1983
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 188.6 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 9(1)  (1986)  Iron-octahedrite
AMN 13(1)  (1990)  IAB
Meteoritical Bulletin:  MB 76  (1994)  IAB
NHM Catalogue:  5th Edition  (2000)  IAB
MetBase:  v. 7.1  (2006)  IAB-sLL
Recommended:  Iron, IAB-sLL    [explanation]

This is 1 of 33 approved meteorites classified as Iron, IAB-sLL.   [show all]
Search for other: IAB complex irons, Iron meteorites, and Metal-rich meteorites
Writeuphelp
Writeup from AMN 9(1):

Sample No.: EET83333

Location: Elephant Moraine

Weight (g): 188.6

Field No.: 2797

Dimensions (cm): 5 x 4 x 2.5

Meteorite Type: Silicate-rich Octahedrite

Macroscopic Description: Roy S. Clarke, Jr.

This specimen is irregularly shaped, weathered and pitted, and mainly covered with a reddish brown coating of secondary oxides. Tiny areas of remnant fusion crust have been preserved in several depressions. Silicates are exposed at the bottoms of other depressions, the largest silicate area measuring 10 x 5 mm. Ablative melting of inclusions appears to have caused other surface depressions.

 

Polished Section Description: Roy S. Clarke, Jr.

A median section through the specimen provided an area of approximately 8 sq. cm for examination. The surface is silicate- rich, containing a number of silicate regions in the mm-size range, as well as numerous small individual crystals irregularly distributed in the metal. Silicate associations comprise 5-10% of the surface area, two clusters having maximum dimensions of 5 mm. The metal is polycrystalline kamacite with individual crystals in the mm-size range. Longest dimensions are normally less than 5 mm, and the shortest normally more than 1 mm. Taenite and pearlitic plessite areas are distributed along grain boundaries and at junctions of three or more kamacite grains. A striking feature of the etched surface is a continuous and unusually thick circumferential heat altered zone. The thickness of the a structure averages about 5 mm and ranges from 2 to 7 mm. About half of the area of the slice is heat altered. Although small areas of fusion crust were tentatively identified in surface depressions, none was recognized in polished section. Weathering is most obvious near the surface and has penetrated into the interior along grain boundaries.

 

Interior kamacite areas contain numerous straight Neumann bands and numerous curved subboundaries. Subboundaries are populated with occasional schreibersites, some of which have distinct rhabdite morphologies. Kamacite areas tend to be mottled, suggesting the presence of unresolvable microrhabdites. Large schreibersites occur along crystal boundaries, and several areas of massive schreibersite occur in association with silicate-troilite areas. Schreibersite also occurs at taenite borders. The plessite has a well developed pearlitic structure and is present in abundance consistent with a medium or coarse octahedrite. A distinct Widmanstätten pattern is not well enough developed to obtain reliable band widths.

 

Silicate areas contain coarse (0.1 to 0.5 mm), colorless, and trans-parent crystals associated with abundant troilite and traces of included kamacite and taenite. Graphite is irregularly associated with silicates, generally at silicate/metal interfaces. It is coarse-grained when present. All the troilite in this section occurs with silicates. Survey electron microprobe examination of the silicates identified plagioclase (An9), olivine (Fa5), and pyroxene (Fs7).

 

This individual is a silicate-rich octahedrite, probably a Group I meteorite. The unusually thick heat-altered zone suggests an atypical passage through the atmosphere. It is distinct from EET84300, another silicate-rich iron.

Data from:
  MB76
  Table 2
  Line 1593:
Origin or pseudonym:Main icefield
Mass (g):188.6
Class:IAB
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 9(1) (1986), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (76° 11'S, 157° 10'E)
     Recommended::   (76° 18' 7"S, 157° 17' 2"E)
Note: the NHM and MetBase coordinates are 13.6 km apart

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