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Northwest Africa 7475
Basic information Name: Northwest Africa 7475
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7475
Observed fall: No
Year found: 2012
Country: (Northwest Africa)
Mass:help 80.2 g
Classification
  history:
Meteoritical Bulletin:  MB 102  (2013)  Martian (basaltic breccia)
Recommended:  Martian (polymict breccia)    [explanation]

This is 1 of 17 approved meteorites classified as Martian (polymict breccia).   [show all]
Search for other: Martian meteorites
Comments: Approved 6 May 2013
Revised 16 Nov 2018: Updated class; see NWA 7034)
Writeuphelp
Writeup from MB 102:

Northwest Africa 7475 (NWA 7475)

(Northwest Africa)

Purchased: 2012 Sep

Classification: Martian meteorite (basaltic breccia)

History: Purportedly recovered at the find site for NWA 7034 near Bir Anzarane, southern Morocco in 2012 and purchased by Luc Labenne from a Moroccan dealer in September 2012.

Physical characteristics: Black, partly fusion-crusted stone (80.2 g) consisting of black and white angular clasts plus dark spheroidal objects in a black matrix.

Petrography: (A. Wittmann, R. Korotev, P. Carpenter and B. Jolliff, WUSL; A. Irving and S. Kuehner, UWS; D. Moser and I. Barker, UWO) Complex breccia composed of angular to rounded mineral clasts, lithic fragments, and spheroidal objects (up to 5 mm in diameter), in a fine grained, dark matrix rich in magnetite. Minerals present include a variety of pyroxenes (orthopyroxene, pigeonite, subcalcic augite, augite and hedenbergite), sodic to intermediate plagioclase, Ti-bearing magnetite, chlorapatite, ilmenite, pyrite, maghemite, hematite, alkali feldspar, anorthoclase, rutile, and monazite. Many clasts exhibit 50 μm-thick mantles of concentrically aligned, accreted debris >5 μm in size. Clast types range from monomineralic feldspar and pyroxene fragments <1 mm size to polymineralic clasts that are aphanitic-glassy (some with igneous contacts to the host matrix). Crystallized melt clasts have textures ranging from sub-ophitic to ophitic, granular and poikilitic with grain sizes of plagioclase and pyroxene <0.5 mm. Some spheroidal objects are composed of glass or fine grained quench assemblages, whereas others consist of concentrically zoned grain aggregates with radial shrinkage fractures.

Geochemistry: (A. Wittmann, WUSL; S. Kuehner, UWS) Orthopyroxene (Fs19-48Wo1-5, FeO/MnO = 27-45; n = 38), pigeonite (Fs25-44Wo5-19, FeO/MnO = 23-45; n = 9), subcalcic augite (Fs17-30Wo29-41, FeO/MnO = 17-41; n = 18), augite (Fs9-18Wo45-49, FeO/MnO = 18-61; n = 5), hedenbergite (Fs37-44Wo43-48, FeO/MnO = 40-65; n = 2), plagioclase (An10-58Or1.9-6.8; n = 35), alkali feldspar (An0.8-13Or53-90Cn1-6; n = 10), anorthoclase (An22-26Or10-20; n = 2), magnetite (0.3-16.1 wt.% Cr2O3, 0.25-0.38 wt.% NiO; n = 15), ilmenite (3-5 wt.% MgO; n = 8), pyrite (up to 2.8 wt.% Ni; n = 7).

Classification: Martian (basaltic breccia). This specimen is essentially identical in texture and mineralogy to NWA 7034 and NWA 7533, and is evidently paired with those distinctive stones.

Specimens: 16.1 g of type material and one polished thin section are on deposit at UWB. The remaining material is held by Labenne.

Data from:
  MB102
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2012 Sep
Mass (g):80.2
Pieces:1
Class:Martian (basaltic breccia)
Shock stage:medium
Weathering grade:low
Ferrosilite (mol%):19-48; 25-44; 17-30; 9-18; 37-44
Wollastonite (mol%):1-5; 5-19; 29-41; 45-49; 43-48
Classifier:A. Wittmann, WUSL; A. Irving and S. Kuehner, UWS
Type spec mass (g):16.1
Type spec location:UWB
Main mass:L. Labenne
Comments:Submitted by A. Irving
Institutions
   and collections
UWO: University of Western Ontario, Department of Earth Sciences, BGS 1026, 1151 Richmond St. N, London, Ontario, Canada N6A 5B7, Canada (institutional address; updated 18 Jul 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, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
Labenne: 23, rue de Esperance, 75013 Paris, France; Website (private address; updated 29 Aug 2012)
Catalogs:
References: Published in Meteoritical Bulletin, no. 102, MAPS 50, 1662, September 2015
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 6900 approved meteorites from (Northwest Africa) (plus 2035 unapproved names)

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