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Elephant Moraine 87521
Basic information Name: Elephant Moraine 87521
     This is an OFFICIAL meteorite name.
Abbreviation: EET 87521
Observed fall: No
Year found: 1987
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 30.7 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 11(2)  (1988)  Eucrite
AMN 13(1)  (1990)  Lunar (basaltic breccia)
Meteoritical Bulletin:  MB 76  (1994)  Lunar-basaltic
NHM Catalogue:  5th Edition  (2000)  Lunar (basalt)
MetBase:  v. 7.1  (2006)  Lunar (basalt)
Recommended:  Lunar (basalt)    [explanation]

This is 1 of 19 approved meteorites classified as Lunar (basalt).   [show all]
Search for other: Lunar meteorites
Writeuphelp
Writeup from AMN 11(2):

Sample No.: EET87521

Location: Elephant Moraine

Weight (g): 30.7

Field No.: 4452

Dimensions (cm): 3.7 x 2.5 x 2

Meteorite Type: Brecciated Eucrite

 

Macroscopic Description: Carol Schwarz

About 30% of this smooth rounded specimen is covered with black to brown shiny fusion crust. The interior of this breccia is dark and fine-grained with white and yellowish inclusions. It is coherent and has several large 2-3 mm white inclusions located near the exterior of the specimen.

 

Thin Section (,2) Description: Brian Mason

The section shows a microbreccia of pale brown pyroxene and colorless plagioclase clasts, up to 1.2 mm across, in a comminuted groundmass of these minerals. Pyroxene compositions show a wide range: Wo15-39, Fs41-61, En 12-41, but cluster around Wo20Fs45 and Wo37Fs48 (one grain is Wo22Fs61). One grain of Fe-rich olivine, Fa91, was analyzed. Plagioclase composition is An68-89. An SiO2 polymorph, probably tridymite, is present in accessory amounts. The meteorite is a brecciated eucrite, but the iron-rich nature of the pyroxenes and the presence of fayalitic olivine distinguishes it from most eucrites.


[From AMN 13(2):]

RECLASSIFICATION

Sample No. EET87521

Location: Elephant Moraine

Weight (g): 30.7

Field No: 4452

Dimensions(cm): 3.7 x 2.5 x 2

Meteorite Type: Lunar Basaltic Breccia

 

Macroscopic Description: Carol Schwarz and Marilyn Lindstrom

About 30% of this smooth rounded specimen is covered with black to brown shiny fusion crust. The interior of this coherent breccia is dark and fine-grained and contains numerous small white and yellow inclusions. Two 2-3 mm clasts are visible on the surface: One is a white clast consisting of plagioclase with 10-15% yellow and black mafic minerals; the other is a buff-colored clast made up of plagioclase and 35-50% yellow and black mafic minerals.

 

Thin Section (EET87521,8 & ,9) and Bulk Composition (EET87521,6) Description: Jeremy Delaney and Paul Warren

EET87521 was originally classified as a eucrite. However, more detailed investigations indicate that it is a very-low-titanium (VLT) basaltic breccia of lunar derivation. The modal mineralogy is 5-10% olivine, 45-50% pyroxene, 35-40% plagioclase and 1-2% ilmenite, chromite, ulvospinel/magnetite, sulfide, silica minerals, and FeNi-metal. The matrix of the meteorite also contains several percent of glass similar in composition to the bulk meteorite. The olivine ranges in composition from Fo65 to Fo5, a range typical of VLT mare basalts, and shows a strong bimodality with clusters centered at Fo57-65 and Fo5-15. Intermediate olivine compositions are uncommon. Molar Fe/Mn ratios of the olivine are 90-100. The pyroxene is pigeonite/subcalcic augite/augite with a composition range of En65Wo5-10 to En20Wo15-40. Most pyroxene is iron-rich and comparable to eucritic pyroxene, but is generally more calcic than eucritic pyroxene. The pyroxene does not show the bimodal distribution of the olivine. Pyroxene Fe/Mn ratios are 50-75. These ratios are typical of mare basalts, and much higher than those of basaltic achondrites (30-40). The feldspar is mostly An93-97 with a few more sodic grains present. Several clasts within the thin sections have survived with textures little altered by brecciation. These clasts tend to be relatively coarse-grained, by mare basalt standards.

 

Thin section [,9] contains a small (1 mm) clast of what is probably a highlands impact melt breccia. This extremely fine-grained clast contains at least 70% plagioclase. It also contains the only observed grains of FeNi-metal, with compositions (average 94.1% Fe, 4.53% Ni, 0.37% Co) typical of metals derived as "contamination" from metal-rich meteorites.

 

The bulk composition of EET87521 has been studied by INAA, using two adjacent chips, 278-290 mg in mass. The TiO2 concentration is 0.8-1.1%, and results for ratios such as Fe/Mn, Ga/Al, Na/Ca, and Co/Cr indicate that this sample is lunar, and certainly not a eucrite. In general, the bulk composition shows a striking resemblance to VLT mare basalts from Luna 24. Perhaps the most significant difference is that EET87521 has higher concentrations of incompatible elements, especially light REE. This difference might be caused by the highlands component associated with the FeNi-bearing clast. However, the bulk-rock Ni content (29-43 μg/g) indicates that the total proportion of non-VLT "contaminant" is probably small.

 

References;

J. Delaney (1989) Nature 342, 889-890.

P. Warren and G. Kallemeyn (1989) Geochim. Cosmochim. Acta 53, 3323-3330.

 

Oxvgen Isotopic Composition: Robert Clayton

The oxygen isotopic composition is δ18O = +5.39, δ17O = +2.79. These analyses are comparable to those of previously analyzed lunar meteorites and Apollo lunar samples and distinct from those of eucrites.

 

Data from:
  MB76
  Table 2
  Line 1695:
Origin or pseudonym:Meteorite City
Mass (g):30.7
Class:Lun-B
Weathering grade:A
Fayalite (mol%):35-95
Ferrosilite (mol%):25-65
Plots: O isotopes:  
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 11(2) (1988), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Photos:
CreditPhotos
Photos from the Encyclopedia of Meteorites:
From NASA photo S88-42979   
Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (76° 11'S, 157° 10'E)
     Recommended::   (76° 11'S, 157° 10'E)

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