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Lunar Meteorite: Elephant Moraine (EET) 87521/96008 (paired stones)Antarctica, Allan Hills area |
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EET 87521. This meteorite was originally
classified as a brecciated eucrite, but it was later recognized to be a
brecciated lunar volcanic rock by Paul Warren of UCLA and Jeremy Delaney
of Rutgers. The cube is 1 cm on each side. Click on image for enlargement. From NASA photo S88-42979 |
| EET 87521. Fusion crust is
visible in this image. Click on image for enlargement. From NASA photo S88-42979. |
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EET 87521. The
interior of the meteorite. Click on image for enlargement. From NASA photo S90-32696 |
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| EET 96008. EET 96008 was
found 9 years after EET 87521 in the same region of the Elephant Moraine.
The stones are paired – they’re two different pieces of a single meteorite.
Click on image for enlargement. From NASA photo S97-08676 |
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EET 96008. The incomplete
fusion crust is evident on this face. Click on image for enlargement. From NASA photo S97-08673 |
| Listed in The
Meteoritical Bulletin, No. 76, Meteoritics 29,
100-143 (1994) Original classification from Antarctic Meteorite Newsletter, Vol. 11, No. 2, 1988 (p. 21) EET 87521Location: Elephant MoraineWeight (g): 30.7 Field No.: 4452 Dimensions (cm): 3.7 x 2.5 x 2 Meteorite Type: Brecciated Eucrite Physical Description: Carol SchwarzAbout 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.Petrographic Description: Brian MasonThe 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, En12-41, 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.Reclassification from EET87521Location: Elephant MoraineWeight (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 LindstromAbout 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 WarrenEET87521 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.ReferencesJ. Delaney (1989) Nature 342, 889-890.P. Warren and G. Kallemeyn (1989) Geochim. Cosmochim. Acta 53, 3323-3330. Oxygen Isotopic Composition: Robert ClaytonThe oxygen isotopic composition is d18O = +5.39, d17O = +2.79. These analyses are comparable to those of previously analyzed lunar meteorites and Apollo lunar samples and distinct from those of eucrites. |
| Listed in The
Meteoritical Bulletin, No. 82, Meteoritics & Planetary Science
33, A221-A239 (1998) from Antarctic Meteorite Newsletter, Vol. 21, No. 1, 1998 EET 96008Location: Elephant MoraineDimensions (cm): 4.5x3.5x1.5 Weight (g): 52.97 Meteorite Type: Lunar Basaltic Breccia Macroscopic Description: Kathleen McBride50% of this meteorite is covered by a black glassy fusion crust. Areas that lack fusion crust appear virtually unweathered. The fusion crust is very thinly distributed over the surface of the rock. The matrix is fine grained, medium gray with numerous inclusions. These inclusions are white, light gray and tan and are angular and subangular in shape. Metal and rust are not visible. This is a brecciated basalt, possibly lunar in origin.Thin Section (,4) Description: Brian MasonThe section shows a microbreccia of pyroxene and plagioclase clasts, up to 1.2 mm across; traces of nickel-iron and sulfide are present, as small scattered grains. Microprobe analyses show that most of the pyroxene ranges from Wo11Fs31 to Wo40 Fs18, with a few more iron-rich grains; plagioclase composition is An93-96. A few olivine grains of variable composition, Fa41-64, were analyzed. Fe/Mn in pyroxene is about 70. The meteorite is a lunar basaltic breccia. |
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