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Northwest Africa 11729
Basic information Name: Northwest Africa 11729
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11729
Observed fall: No
Year found: 2017
Country: Mauritania
Mass:help 345 g
Meteoritical Bulletin:  MB 107  (2018)  Eucrite-an
Recommended:  Eucrite-an    [explanation]

This is 1 of 15 approved meteorites classified as Eucrite-an.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Comments: Approved 7 Apr 2018
Writeup from MB 107:

Northwest Africa 11729 (NWA 11729)


Purchased: 2017 Dec

Classification: HED achondrite (Eucrite, anomalous)

History: Purchased by Rachid Chaoui in December 2017 from a Mauritanian dealer and subsequently acquired by Bob Falls.

Physical characteristics: A single brownish stone (345 g) mostly coated by black fusion crust. The interior exhibits a breccia texture with beige clasts stained light orange by terrestrial weathering.

Petrography: (A. Irving and S. Kuehner, UWS) Breccia composed of closely packed microgabbroic clasts plus some genomict breccia clasts within a sparse matrix of related debris. Minerals are exsolved ferroan pigeonite, calcic plagioclase, silica polymorph, ilmenite Ti-chromite, fayalitic olivine and minor zircon. Terrestrial weathering has resulted in extensive alteration of primary troilite to Fe hydroxides and some cross-cutting hydroxide veinlets.

Geochemistry: Orthopyroxene host (Fs69.6Wo1.7, FeO/MnO = 29), clinopyroxene exsolution lamella (Fs33.2Wo42.1, FeO/MnO = 30), clinopyroxene host (Fs30.9Wo43.5, FeO/MnO = 32), orthopyroxene exsolution lamella (Fs69.5Wo1.9, FeO/MnO = 36), fayalite (Fa73.9-74.1, FeO/MnO = 47, N = 2), plagioclase (An82.3-84.3Or0.7-0.5, N = 2). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively, d17O 2.680,3.062, 2.301; d18O 5.540, 6.312, 4.934; D17O -0.245, -0.271, -0.304 per mil.

Classification: Eucrite (anomalous monomict breccia, microgabbroic, highly ferroan). The pyroxenes in this specimen are much more ferroan than in any other known eucrites: ferrosilite contents in orthopyroxene are almost 70 mol.%. The oxygen isotopic composition is also unusual with a higher d18O than other main group eucrites.

Specimens: 22.5 g including one polished thin section at UWB; remainder with Mr. R. Falls.

Data from:
  Table 0
  Line 0:
Place of purchase:Mauritania
Date:P 2017 Dec
Mass (g):345
Shock stage:low
Weathering grade:moderate
Fayalite (mol%):73.9-74.1
Ferrosilite (mol%):69.5-69.6
Wollastonite (mol%):1.9-1.7
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):22.5
Type spec location:UWB
Main mass:R. Falls
Comments:Work name RC97.1; 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)
UWB: University of Washington, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023)
References: Published in Meteoritical Bulletin, no. 107, MAPS 55, 460-462
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     This is 1 of 221 approved meteorites from Mauritania (plus 2 unapproved names) (plus 2 impact craters)

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