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Northwest Africa 4937
Basic information Name: Northwest Africa 4937
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 4937
Observed fall: No
Year found: 2007
Country: Morocco
Mass:help 212 g
Meteoritical Bulletin:  MB 94  (2008)  Winonaite
Recommended:  Winonaite    [explanation]

This is 1 of 81 approved meteorites (plus 1 unapproved name) classified as Winonaite.   [show all]
Search for other: Primitive achondrites, Winonaites
Comments: Approved 17 Apr 2008
Writeup from MB 94:

Northwest Africa 4937


Find: May 2007

Achondrite (winonaite)

History: Purchased by an anonymous Moroccan dealer in Bir Elmalh Mahbas, Morocco, in May 2007.

Physical characteristics: A brown, somewhat weathered stone (212 g, broken into several fragments) with visible metal and patches of brown fusion crust. Interior silicates are fresh, but metal is partly altered to reddish-brown iron hydroxides.

Petrography: (A. Irving and S. Kuehner, UWS) Coarse grained (0.6–1.5 mm) protogranular aggregate of silicate phases (mostly sodic plagioclase, orthopyroxene and clinopyroxene) with abundant rounded to cuspate grains of metal (kamacite) and accessory olivine, schreibersite and troilite. No chromite was found. The estimated mineral mode is metal (+ altered metal) 40, plagioclase 28, orthopyroxene 20, clinopyroxene 10, others 2 (see image). Olivine is very rare, and occurs only as small round inclusions (up to 100 μm) within clinopyroxene.

Geochemistry: Orthopyroxene (Fs7.4–7.9Wo2.4–2.7, FeO/MnO = 8.2–9.8, 0.52 wt% Cr2O3), clinopyroxene (Fs3.7–4.1 Wo40.6– 42.5, FeO/MnO = 6.3–8.1, 1.2 wt% Cr2O3), plagioclase (An14.9–18.6Or2.3–2.1), olivine (Fa7.0, FeO/MnO = 12.8). Oxygen isotopes (D. Rumble, CIW): δ18O = 4.370, 4.206; δ17O = 1.763, 1.738; Δ17O = -0.535, -0.474 (all‰).

Classification: Achondrite (winonaite). This specimen is a metal-rich gabbro-norite that contains less than 0.1 vol% olivine, and is much coarser grained than typical winonaites, yet it has oxygen isotope affinities to the latter group.

Specimens: A total of 20.1 g of sample and one polished mount are on deposit at UWS. The main mass is held by an anonymous collector.

Data from:
  Table 2
  Line 91:
Mass (g):212
Fayalite (mol%):7
Ferrosilite (mol%):7.4-7.9
Wollastonite (mol%):2.4-2.7
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):20.3
Type spec location:UWS
Main mass:anonymous
Comments:Oxygen isotopes: δ18O = 4.370; 4.206; δ17O = 1.763, 1.738; Δ17O = -0.535, -0.474 (all‰)
Plots: O isotopes:  
   and collections
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
CIW: Carnegie Insitution Washington, Geophysical Laboratory, 5251 Broad Branch Rd., NW, Washington DC 20015, United States (institutional address)
References: Published in Meteoritical Bulletin, no. 94, MAPS 43, 1551-1588 (2008)
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     This is 1 of 1991 approved meteorites from Morocco (plus 31 unapproved names) (plus 1 impact crater)

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