|Northwest Africa 6693|
|Basic information||Name: Northwest Africa 6693|
This is an OFFICIAL meteorite name.
Abbreviation: NWA 6693
Observed fall: No
Year found: 2011
Mass: 5.1 kg
This is 1 of 75 approved meteorites classified as Achondrite-ung. [show all]
Search for other: Achondrites, Ungrouped achondrites
|Comments:||Approved 6 May 2011|
Writeup from MB 99:
Northwest Africa 6693 (NWA 6693)
Found: March 2010
Classification: Ungrouped achondrite
Petrography: The largest pyroxene is poikilitic, 5 mm across, with mainly plagioclase chadacrysts, but pyroxenes with blocky shapes and 1-2 mm maximum dimensions are more common. Olivines are blocky, to 1 mm. Plagioclase is consistently fine-grained and anhedral (interstitial). No chondrules visible. Mineral abundances (vol%) are 70.3 pyroxene, 15.6 olivine, 13.4 plagioclase, 0.6 Cr-spinel, 0.4 Ni-rich metal, ~0.002 Ni-rich sulfide, and trace merrillite.
Geochemistry: The silicate compositions cluster tightly near: low-Ca pyx, En57Wo3.3 with FeO/MnO = 90 (not HED, not martian); feldspar, Ab92Or2.5; olivine Fo47-51. The pyroxene in places contains small lamellae, only rarely (where blebby) large enough for EPMA, of En40Wo40 high-Ca pyroxene. Cr-spinel composition is 57.8 wt% Cr2O3, 32.0 wt% FeO, ~2.1 wt% Fe2O3, 2.8 wt% TiO2, 1.7 wt% MgO. The Ni-rich metal is tightly clustered at 81 wt% Ni. O isotopic composition (B-G. Choi and I. Ahn, using CO2 laser-fluorination at Seoul-NU; avg. of 2 similar replicate analyses): δ18O = 4.32‰, δ17O = 1.19‰ and Δ17O = -1.08‰ (per mil).
Classification: Ungrouped achondrite. No other achondrite has such ferroan mafic silicates (mg~59 low-Ca pyroxene, Fo~50 olivine) in such high modal abundance. The extremely sodic plagioclase (Ab92) and Ni-rich (81 wt%) metal are also distinctive.
Specimens: A 28.4 g type specimen is on deposit at UCLA.
UCLA: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, United States (institutional address; updated 17 Oct 2011)
Seoul-NU: Department of Earth Science Education, Room# 13-426, Seoul National University, Seoul, Korea, 151-748, South Korea (institutional address; updated 20 Dec 2014)
Thompson: Edwin Thompson, 5150 Dawn St., Lake Oswego, OR 97035, United States (private address)
|References:||Published in Meteoritical Bulletin, No. 99, April 2012, MAPS 47, E1-E52 (2012) [published online only]|
This is 1 of 1218 approved meteorites from Morocco (plus 11 unapproved names)
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