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Northwest Africa 13921
Basic information Name: Northwest Africa 13921
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 13921
Observed fall: No
Year found: 2020
Country: (Northwest Africa)
Mass:help 807 g
Meteoritical Bulletin:  MB 110  (2022)  Achondrite-ung
Recommended:  Achondrite-ung    [explanation]

This is 1 of 151 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 29 May 2021
Writeup from MB 110:

Northwest Africa 13921 (NWA 13921)

(Northwest Africa)

Purchased: 2020 Jul

Classification: Ungrouped achondrite

History: Purchased by Didi Baidari in July 2020 from a dealer in Tindouf, Algeria and subsequently acquired by Luc Labenne.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL) Complex specimen consisting of some polymineralic lithic clasts and irregularly-shaped mineral grains within a dominant quench-textured groundmass. Lithic clasts are relatively coarse grained gabbroic assemblages composed of olivine, low-Ca pyroxene (patchily-zoned orthopyroxene and pigeonite) and highly calcic plagioclase with accessory kamacite, taenite, Ti-chromite and troilite. Separate irregularly shaped (apparently resorbed) mineral grains are olivine, orthopyroxene, pigeonite, augite, exsolved pigeonite, silica polymorph and calcic plagioclase. The groundmass or matrix is composed mainly of radiating arrays of very thin, acicular, strongly-zoned pyroxene grains, some of which are oriented perpendicular to edges of the larger mineral grains and appear to have nucleated on them. Accessory phases in the matrix include kamacite (with taenite rims), ilmenite, troilite and pentlandite.

Geochemistry: Olivine (Fa29.4-40.9, FeO/MnO = 53-63, N = 9), low-Ca pyroxene (Fs17.5Wo1.0, FeO/MnO = 27; Fs25.9-27.7Wo1.0-4.7, FeO/MnO = 38-47, N = 4), pigeonite (Fs36.9-45.5Wo5.9-10.0, FeO/MnO = 28-32, N = 2), subcalcic augite (Fs40.4-48.6Wo20.0-26.7, FeO/MnO = 28-31, N = 2; Fs72.0Wo24.4, FeO/MnO = 43), pigeonite host (Fs46.3Wo11.4, FeO/MnO = 32), augite exsolution lamella (Fs29.1Wo36.1, FeO/MnO = 31), calcic plagioclase (An87.3-93.1Or0.5-0.1, N = 7). Oxygen isotopes (K. Ziegler, UNM): analyses of 7 acid-washed subsamples by laser fluorination gave, respectively, δ17O 1.770, 1.963, 1.851, 1.875, 1.757, 1.900, 1.856; δ18O 3.691, 4.092, 3.885, 3.905, 3.706, 4.012, 3.913; Δ17O -0.179, -0.197, -0.200, -0.187, -0.199, -0.218, -0.210 per mil (all data linearized).

Classification: Achondrite (ungrouped, mafic, melt-textured with remnant lithic and mineral clasts). Although the mineralogy of some components in this specimen (except for the Ni-bearing metal) have some resemblance to those in typical diogenites and eucrites, oxygen isotopes do not not support such a relationship. In fact, oxygen isotopic compositions are displaced closer to the TFL than the fields for diogenites and main group eucrites, and plot near the results for anomalous eucrites Pasamonte, Moama, and Allan Hills 78132. This specimen may represent an anomalous mafic, olivine gabbroic achondrite which has been partially melted and rapidly quenched.

Specimens: 23.4 g including one polished thin section at UWB; remainder with Mr. D. Baidari.

Data from:
  Table 0
  Line 0:
Place of purchase:Tindouf
Date:P 2020 Jul
Mass (g):807
Shock stage:low
Weathering grade:low
Fayalite (mol%):29.4-40.9
Ferrosilite (mol%):17.5-27.7; 36.9-45.5; 40.4-48.6
Wollastonite (mol%):1.0-4.7; 5.9-10.0; 20.0-26.7
Classifier:A. Irving, UWS, and P. Carpenter, WUSL
Type spec mass (g):23.4
Type spec location:UWB
Main mass:L. Labenne
Comments:Work name DB-14; submitted by A. Irving
Plots: O isotopes:  
   and collections
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
WUSL: Washington Univ., One Brookings Drive, St. Louis, MO 63130, United States (institutional address; updated 17 Oct 2011)
UWB: University of Washington, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023)
Labenne: 23, rue de Esperance, 75013 Paris, France; Website (private address; updated 29 Aug 2012)
References: Published in Gattacceca J., McCubbin F.M., Grossman J., Bouvier A., Chabot N.L., D'Orazio M., Goodrich C., Greshake A., Gross J., Komatsu M., Miao B., and Schrader D. (2022) The Meteoritical Bulletin, No. 110. Meteorit. Planet. Sci. 1-4
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     This is 1 of 9699 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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