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Northwest Africa 13689
Basic information Name: Northwest Africa 13689
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 13689
Observed fall: No
Year found: 2020
Country: (Northwest Africa)
Mass:help 165 g
Recommended:  C3.00-ung    [explanation]

This is 1 of 4 approved meteorites classified as C3.00-ung.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 3), and Ungrouped chondrites
Comments: Approved 1 Aug 2021
Revised 8 Aug 2021: corrected class
Writeup from MB 110:

Northwest Africa 13689 (NWA 13689)

(Northwest Africa)

Purchased: 2020 Oct

Classification: Carbonaceous chondrite (C3, ungrouped)

History: Bought from a mineral dealer in Nouakchott, Mauritania.

Physical characteristics: Individual meteorites with fusion crust, showing a network of contraction cracks.

Petrography (K. Metzler, IfP): Carbonaceous chondrite, consisting of small chondrules, chondrule fragments, AOAs, and some CAIs (up to ~250 µm), embedded in a black, fine-grained matrix. The mean apparent chondrule size is 140±80 µm (50-510 µm; n=60). Mostly type I chondrules, but some type II chondrules and chondrule fragments occur. Many chondrules are rimmed by accretionary dust mantles. Point counting on BSE images revealed ~30 area% (vol%) fine-grained matrix, including dust mantles. Nearly all preexisting metal and sulfide appears to be replaced by pure magnetite (free of MgO, Al2O3, TiO2, and Cr2O3). Some tiny relics of very Ni-rich metal (~Fe40Ni60) and sulfides (troilite and pentlandite) are present in the centers of magnetite grains. Some dust mantles are crosscut by magnetite veins. Magnetic properties (J. Gattacceca, CEREGE): magnetic susceptibility log χ (× 10-9 m3/kg) = 4.98 ; saturation magnetization Ms=16.33 Am2/kg indicates a magnetite content of 17.8 wt%.

Geochemistry: Mineral compositions and geochemistry: Mean value of randomly chosen olivine grains: Fa4.5±9.0 (0.4-39.5; n=30). Mean value of randomly chosen low-Ca pyroxene grains: Fs2.3±2.6 Wo1.9±1.4 (Fs0.6-13.1 Wo0.5-4.9; n=30). EPMA analysis (J. Gattacceca, CEREGE) of 29 ferroan olivine give 0.32±0.12 wt% Cr2O3. The analytical total in the matrix obtained by EPMA with a defocused beam is 84 wt%, with FeO = 31 wt%. Semi-quantitative X-ray diffractometry (P. Schmidt-Beurmann, Inst. Min, Univ. Münster) revealed ~15±5 wt% magnetite and no indications for phyllosilicates. Oxygen isotope analysis (J. Gattacceca, C. Sonzogni, CEREGE) of a 1.5 mg aliquot obtained from a bulk 15 mg sample yield δ18O=0.468‰ and δ17O=-4.084‰.

Classification: Carbonaceous chondrite based on the predominance of type I chondrules, CAI occurrence, and O isotopic composition. Petrologic type 3 based on the strong chemical variation of olivine and pyroxene and the absence of phyllosilicates. Petrologic subtype 3.00, due to the concentration and standard deviation of Cr2O3 in ferroan olivine. Ungrouped due to the oxygen isotopic composition which is in the CV-CK-CL range and the exceptionally high fraction of magnetite (~18 wt%).

Data from:
  Table 0
  Line 0:
Place of purchase:Nouakchott, Mauritania
Date:P 2020 Oct
Mass (g):165
Shock stage:C-S1
Weathering grade:low
Fayalite (mol%):4.5±9.0
Ferrosilite (mol%):2.3±2.6
Wollastonite (mol%):1.9±1.4
Magnetic suscept.:4.98
Classifier:K. Metzler, IfP
Type spec mass (g):20
Type spec location:IfP
Main mass:Ben Hoefnagels
Comments:Submitted by K. Metzler, IfP
Plots: O isotopes:  
   and collections
CEREGE: CEREGE BP 80 Avenue Philibert, Technopole de l'Arbois 13545 Aix-en-Provence Cedex 4 France, France (institutional address; updated 29 Oct 2018)
IfP: Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany (institutional address; updated 23 Jan 2012)
References: Published in Meteoritical Bulletin, no. 110, in preparation (2021)
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Public domain photographs:
Knut Metzler         

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

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