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Northwest Africa 7634
Basic information Name: Northwest Africa 7634
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7634
Observed fall: No
Year found: 2012
Country: (Northwest Africa)
Mass:help 866 g
Meteoritical Bulletin:  MB 103  (2014)  CO3
Recommended:  CO3    [explanation]

This is 1 of 616 approved meteorites (plus 1 unapproved name) classified as CO3.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 3), CM-CO clan chondrites, and CO chondrites
Comments: Approved 1 Jul 2014
Revised 2 Jun 2019: Corrected O isotopes
Writeup from MB 103:

Northwest Africa 7634 (NWA 7634)

(Northwest Africa)

Purchased: 2012 Nov

Classification: Carbonaceous chondrite (CO3)

History: Purchased by J. Utas in November 2012 from a dealer in Zagora, Morocco.

Physical characteristics: A single stone (866 g) with ablated fusion crust on its exterior and a very fine grained, deep-brown interior.

Petrography: (A. Irving and S. Kuehner, UWS) Fine-grained assemblage of small, rounded and broken chondrules (maximum size 0.7 mm, but mostly much smaller), angular mineral grains and fairly abundant tiny CAIs in a dusty matrix rich in ferroan olivine with accessory kamacite, taenite and troilite. Minerals in CAI include Mg-spinel, Fe-rich spinel, perovskite, Al-rich diopside, gehlenite and monticellite.

Geochemistry: Olivine (Fa1.9-66.8; Cr2O3 in ferroan olivine = 0.0.11-0.35 wt.%, mean = 0.16 wt.%, sd = 0.08 wt.%, N = 10), orthopyroxene (Fs1.7-6.6Wo3.0-1.1), diopside (Fs1.6Wo44.6; Fs3.9Wo51.0). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively, δ17O = -4.886, -5.597; δ18O = -5.220, -5.794; Δ17O = -7.800, -8.749 (all per mil).

Classification: Carbonaceous chondrite (CO3). This specimen is unusually fine grained and unusually rich in CAI fragments. Its O isotopic composition plots down and to the left of the main field for CO chondrites on an δ18O vs. δ17O diagram. Its O isotopes may be anomalous or may extend the range for whole rock CO chondrites measured so far.

Specimens: A total of 27 g of material and one polished mount are on deposit at UWB. The main mass is held by J. and P. Utas.

Writeup from MB 108:
NWA 7634, correction

The oxygen isotopes published in MB103 were incorrect. The actual values are:  δ17O = -7.800, -8.749; δ18O = -4.886, -5.597; Δ17O = -5.220, -5.794 (all ‰)
Data from:
  Table 0
  Line 0:
Place of purchase:Zagora
Date:P 2012 Nov
Mass (g):866
Shock stage:S2
Weathering grade:W0/1
Fayalite (mol%):1.9-66.8
Ferrosilite (mol%):1.7-6.6
Wollastonite (mol%):3.0-1.1
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):20.5
Type spec location:UWB
Main mass:J. Utas
Comments:34.1; 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, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
References: Published in Meteoritical Bulletin, no. 103, MAPS 52, 1014, May 2017, http://onlinelibrary.wiley.com/doi/10.1111/maps.12888/full
Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150
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     This is 1 of 8745 approved meteorites from (Northwest Africa) (plus 1880 unapproved names)

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