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Northwest Africa 11187
Basic information Name: Northwest Africa 11187
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11187
Observed fall: No
Year found: 2016
Country: (Northwest Africa)
Mass:help 36.7 g
Meteoritical Bulletin:  MB 106  (2018)  Achondrite-ung
Recommended:  Achondrite-ung    [explanation]

This is 1 of 119 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 10 Apr 2017
Writeup from MB 106:

Northwest Africa 11187 (NWA 11187)

(Northwest Africa)

Purchased: 2016 Oct

Classification: Ungrouped achondrite

History: Purchased by John Higgins in October 2016 from a dealer in Nouakchott, Mauritania.

Petrography: (A. Irving and S. Kuehner, UWS) Relatively coarse grained with poikilitic texture. Large (up to 6 mm) oikocrysts of exsolved magnesian pigeonite (consisting of low-Ca pyroxene host and crystallographically-irrational diopside exsolution lamellae) enclose smaller (up to 1.3 mm) chadacrysts of Cr-poor forsteritic olivine (which exhibit narrow, more magnesian rims). Accessory phases are bladed graphite and kamacite.

Geochemistry: Forsterite (Fa5.4-5.6, FeO/MnO = 11-14, Cr2O3 = 0.4 wt.%; rim Fa2.0, FeO/MnO = 5, Cr2O3 = 0.3 wt.%; N = 4), low-Ca pyroxene host (Fs4.8-4.9Wo4.9-4.8, FeO/MnO = 7-8, N = 2), diopside exsolution blebs and stringers (Fs2.9-3.0Wo36.7-36.8, FeO/MnO = 6, N = 2). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively, δ17O 1.450, 1.544, 1.581; δ18O 6.003, 6.198, 6.318; Δ17O -1.720, -1.729, -1.755 per mil.

Classification: Ungrouped achondrite. Although oxygen isotope values plot near the trend for ureilites, they also plot near (but below) the wide field of values for acapulcoites and lodranites. In contrast with ureilites, the olivine in this specimen is not Cr-rich, and although there are slightly more magnesian rims they are not accompanied by fine grained Fe metal blebs. Additionally the presence of Ni-bearing metal (kamacite), exsolved pigeonite and forsteritic olivine are not characteristic of ureilites, nor is the poikilitic texture.

Specimens: 7.4 g including one polished thin section at UWB; remainder with Mr. J. Higgins.

Data from:
  Table 0
  Line 0:
Place of purchase:Nouakchott, Mauritania
Date:P 2016 Oct
Mass (g):36.67
Shock stage:low
Weathering grade:low
Fayalite (mol%):5.4-5.5
Ferrosilite (mol%):4.8-4.9
Wollastonite (mol%):4.9-4.8
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):7.4
Type spec location:UWB
Main mass:J. Higgins
Comments:JH16-15[G]; 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, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
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 8674 approved meteorites from (Northwest Africa) (plus 1882 unapproved names)

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