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Northwest Africa 11431
Basic information Name: Northwest Africa 11431
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11431
Observed fall: No
Year found: 2017
Country: Mauritania
Mass:help 524 g
Meteoritical Bulletin:  MB 106  (2018)  Martian (shergottite)
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 318 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 13 Oct 2017
Writeup from MB 106:

Northwest Africa 11431 (NWA 11431)


Find: 2017 Jun

Classification: Martian meteorite (Shergottite)

History: Found in June 2017 in Mauritania in a region directly south of the NWA 6963 strewnfield (located near Fej Arrih to the north in adjacent Morocco), and puchased by Ben Hoefnagels in July 2017 from a Moroccan dealer.

Physical characteristics: A single stone (524 g) with a flat prismatic shape almost completely coated by black fusion crust. The interior is gray with evident glassy maskelynite.

Petrography: (A. Irving and S. Kuehner, UWS) Medium-grained, diabasic texture. Composed predominantly of zoned clinopyroxene and maskelynite with accessory Fe-bearing merrillite, titanomagnetite, ilmenite (with rare baddeleyite inclusions), silica polymorph, fayalite and pyrrhotite.

Geochemistry: Pigeonite (Fs36.2-51.6Wo8.1-12.8, FeO/MnO = 31-37, N = 4), subcalcic augite (Fs21.6-42.0Wo30.1-31.3, FeO/MnO =30-42, N = 4), fayalite (Fa85.5, FeO/MnO = 60), maskelynite (An38.4-42.3Or4.5-3.0, N = 2). The most ferroan subcalcic augite rims are notably aluminous (Al2O3 = 2.2-2.5 wt.%) and yield low oxide sums plus high cation totals indicative of the presence of minor ferric iron. Magnetic susceptibility (P. Rochette, CEREGE) log χ (× 10-9 m3/kg) = 3.22.

Classification: Martian (shergottite, diabasic). This specimen has many similarities to the NWA 6963 stones and evidently comes from an extension of the same strewnfield into Mauritania.

Specimens: 26.5 g including one polished thin section and one polished thick section at UWB; remainder with Mr. B. Hoefnagels.

Data from:
  Table 0
  Line 0:
Place of purchase:Morocco
Date:2017 Jun
Mass (g):524
Class:Martian (shergottite)
Shock stage:high
Weathering grade:low
Fayalite (mol%):85.5
Ferrosilite (mol%):36.2-51.6; 21.6-42.0
Wollastonite (mol%):8.1-12.8; 30.1-31.3
Magnetic suscept.:3.22
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):26.5
Type spec location:UWB
Main mass:B. Hoefnagels
Comments:Work name BH112; submitted by A. Irving
   and collections
CEREGE: CEREGE BP 80 Avenue Philibert, Technopole de l'Arbois 13545 Aix-en-Provence Cedex 4 France, France (institutional address; updated 10 Jun 2023)
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 Gattacceca J., Bouvier A., Grossman J., Metzler K., and Uehara M. (2019) Meteoritical Bulletin, no. 106. Meteorit. Planet. Sci. 54 in press.
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     This is 1 of 217 approved meteorites from Mauritania (plus 2 unapproved names) (plus 2 impact craters)

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