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Northwest Africa 5958
Basic information Name: Northwest Africa 5958
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 5958
Observed fall: No
Year found: 2009
Country: Morocco
Mass:help 286 g
Classification
  history:
Meteoritical Bulletin:  MB 99  (2011)  C3.0-ung
Recommended:  C2-ung    [explanation]

This is 1 of 19 approved meteorites classified as C2-ung.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 2), and Ungrouped chondrites
Comments: Approved 30 Dec 2010
Revised 26 Apr 2017: Reclassification
Writeuphelp
Writeup from MB 99:

Northwest Africa 5958 (NWA 5958)

SW Morocco

Found: 2009

Classification: C3.0-ung

History: Purchased by Greg Hupé in September 2009 from a Moroccan dealer in Tagounite.

Physical characteristics: A single, fresh, light-gray stone broken into numerous fragments and weighing 286 g.

Petrography: (T. Bunch and J. Wittke, NAU; A. Irving and S. Kuehner, UWS) The overall texture is fragmental/clastic, with a variety of small objects (mostly 0.05-2.5 mm) set in a dark, fine-grained matrix. Chondrules are predominantly PP, PO, Mg-rich POP and other types. Intact chondrules have multiple (up to 5) accretion rims. Mesostasis is not abundant within chondrules, but where present consists of interlaced quench crystals of fayalite or ferrohortonolite and subcalcic ferroaugite. Some chondrule fragments have discontinuous "veins" of acicular/bladed fayalite. Some PP chondrules contain interstitial grains of carbon (4-16 vol%; grain size = 0.001-0.024 mm; some hexagonal or pseudohexagonal in shape). Carbon grains also are found as fragments in the matrix, and forsterite grains have small carbon clumps. Other rare objects are xenoliths of different fine grained carbonaceous chondrite lithologies, small CAIs and an irregularly-shaped 2.5 mm clast of fragmented calcite.

Geochemistry: The overall compositional range for olivine is Fa0.15-88 (FeO/MnO = 77-148; Cr2O3 = 0.15-0.86 wt.%). Olivine of intact PO chondrule phenocrysts (N = 8) is Fa0.15-2.5. Olivine in zoned chondrule fragments: rims Fa25-58, mean Fa46 (Cr2O3 = 0.23-0.75 wt.%, mean 0.48 wt.%), cores Fa10-28 , mean Fa21 (Cr2O3 = 0.32-0.86 wt.%, mean 0.54 wt.%). Ferroan olivine is Fa68-88. Enstatite in PP chondrules (Fs0.2-2.5Wo1.3); diopside (Fs3.4Wo46); subcalcic ferroaugite in enstatite PP chondrule mesostasis (Fs67Wo19). Kamacite (Ni = 5.5 wt.%, Cr = 1.05 wt.%); chromite [Cr/(Cr+Al) = 0.94-0.96]; troilite (Ni = 2.3 wt.%). Oxygen isotopes (D. Rumble, CIW): two acid-washed subsamples analyzed by laser fluorination gave, respectively δ18O =-8.803, -9.869; δ17O =-11.398, -12.530; Δ17O = -6.768, -7.339 per mil.

Classification: Carbonaceous chondrite (ungrouped, 3.0), S1, W1. This is an unequilibrated chondrite with an extremely 16O-rich bulk oxygen isotopic composition plotting on an extension of the CCAM line.

Specimens: A total of 20.9 g of sample, one polished thin section and a polished thick section are on deposit at UWS. The main mass is held by GHupé.


Writeup from MB 106:
Northwest Africa 5958: Reclassification

Based on the work of Jacquet et al. (2016), NWA 5958 is reclassified as an ungrouped C2 chondrite related to CM2 chondrites. Bulk analyses reveal CM-like chemistry, but the revised O isotopic composition is still more 16O-rich than known CM. Hydration of matrix and mesostasis, oxidation of metal indicate significant, if moderate aqueous alteration. A type 2 classification is thus more appropriate.
Bibliography:
  • Jacquet E., Barrat J.-A., Beck P., Caste F., Gattacceca J., Sonzogni C., and Gounelle M. (2016) Northwest Africa 5958: A weakly altered CM-related ungrouped chondrite, not a CI3. Meteorit. Planet. Sci. 51, 851-869 (link)
Data from:
  MB99
  Table 0
  Line 0:
Place of purchase:Tagounite
Date:2009
Mass (g):286
Pieces:>10
Class:C3.0-ung
Shock stage:S1
Weathering grade:W1
Fayalite (mol%):0.15-88
Ferrosilite (mol%):0.2-2.5; 3.4; 67
Wollastonite (mol%):1.3; 46; 19
Classifier:T. Bunch and J. Wittke; A. Irving and S. Kuehner
Type spec mass (g):20.9
Type spec location:UWS
Main mass:G. Hupe
Comments:Submitted by A. Irving and T. Bunch
Plots: O isotopes:  
Institutions
   and collections
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
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)
GHupé: Gregory M. Hupé, 9003 Placid Lakes Blvd., Lake Placid, FL 33852, United States; Website (private address)
Hupe: (old address—now see GHupé or AHupé) G. and A. Hupe, 2616 Lake Youngs Court SE, Renton, WA 98058., United States (private address)
Catalogs:
References: Published in Meteoritical Bulletin, No. 99, April 2012, MAPS 47, E1-E52 (2012) [published online only]
Published in Gattacceca J., Bouvier A., Grossman J., Metzler K., and Uehara M. (2019) Meteoritical Bulletin, no. 106. Meteorit. Planet. Sci. 54 in press.
Find references in NASA ADS:
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Photos:
CreditPhotos
Photos uploaded by members of the Encyclopedia of Meteorites.
    (Caution, these are of unknown reliability)
Gregor H.   
John Lutzon   
Geography:

Morocco
Coordinates:Unknown.

Statistics:
     This is 1 of 1374 approved meteorites from Morocco (plus 16 unapproved names) (plus 1 impact crater)

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