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Northwest Africa 13479
Basic information Name: Northwest Africa 13479
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 13479
Observed fall: No
Year found: 2020
Country: (Northwest Africa)
Mass:help 25.9 g
Classification
  history:
Recommended:  C2-ung    [explanation]

This is 1 of 24 approved meteorites classified as C2-ung.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 2), and Ungrouped chondrites
Comments: Approved 11 Nov 2020
Writeuphelp
Writeup from MB 109:

Northwest Africa 13479 (NWA 13479)

(Northwest Africa)

Purchased: 2020 Aug

Classification: Carbonaceous chondrite (C2, ungrouped)

History: Purchased by Rachid Chaoui in August 2020 from a Mauritanian dealer.

Petrography: (A. Irving, UWS, P. Carpenter, WUSL; L. Garvie, ASU) Small, well-formed chondrules (apparent diameter 250±210 µm, N = 23) and sparse very fine grained, amoeboid CAI are set within a very fine grained matrix (~65 vol.%, opaque in thin section). Phases identified by EPMA include kamacite (as droplets and separated grains), Fe and Fe-Ni sulfides (typically intergrown and altered), an Fe2O3 oxide phase, and an apparently hydrous, Fe-rich silicate phase with bladed morphology. Powder X-ray diffraction confirms the presence of phyllosilicates, tochilinite, regularly interstratified tochilinite/cronstedtite and maghemite, plus minor calcite and dolomite.

Geochemistry: Olivine (Fa24.1±14.4, range Fa1.0-44.7, N = 5; Cr2O3 in ferroan olivine 0.27-0.53 wt.%, mean wt.%, sd wt.%, N = 7), low-Ca pyroxene (Fs3.2±2.8Wo2.5±2.3, range Fs0.8-6.2Wo0.8-5.6, N = 4). clinopyroxene (Fs5.1±0.1Wo35.0±0.4, range Fs5.0-5.1Wo34.7-35.2, N = 2). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively, δ17O -8.313, -7.758, -7.724; δ18O -4.447, -2.727, -3.473; Δ17O -5.966, -6.318, -5.890 per mil (all data linearized).

Classification: Carbonaceous chondrite (C2 ungrouped). The presence of phyllosilicates and tochilinite establishes this specimen as a C2 chondrite, yet its oxygen isotopic composition plots far from the established array for CM2 chondrites (to much more 16O-rich compositions) and even further from values for CR2 chondrites. Although the oxygen isotopic composition is close to those for a few CV chondrites, an affinity to CV or CK chondrites is excluded on other grounds (notably the relatively small mean chondrule size and absence of Cr-magnetite). Chondrule sizes are within the range for CO chondrites, but oxygen isotopes plot well below the array for CO chondrites (to more negative Δ17O values). The presence of maghemite is an additional anomalous feature.

Specimens: 6.1 g including one polished thin section at UWB; remainder with Mr. R. Chaoui.

Data from:
  MB109
  Table 0
  Line 0:
Place of purchase:Mauritania
Date:P 2020 Aug
Mass (g):25.9
Pieces:6
Class:C2-ung
Shock stage:S2
Weathering grade:low
Fayalite (mol%):24.1±14.4
Ferrosilite (mol%):3.2±2.8
Wollastonite (mol%):2.5±2.3
Classifier:A. Irving, UWS, P. Carpenter, WUSL, and L. Garvie, ASU
Type spec mass (g):6.1
Type spec location:UWB
Main mass:R. Chaoui
Comments:RC136.4; submitted by A. Irving
Plots: O isotopes:  
Institutions
   and collections
ASU: Center for Meteorite Studies, Arizona State University, Tempe, Arizona 85287-1404, United States; Website (institutional address; updated 14 Jan 2012)
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)
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)
Catalogs:
References: Published in Meteoritical Bulletin, no. 109, in preparation (2020)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 7885 approved meteorites from (Northwest Africa) (plus 1958 unapproved names)

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