NORTHWEST AFRICA 13167


C2-ungrouped
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Purchased 2019
no coordinates recorded

Five partially fusion-crusted stones having a combined weight of 1,027 g were purchased from a Moroccan source. Analyses and classification was conducted at the Natural History Museum in Berlin, Germany (A. Greshake) and the University of New Mexico (oxygen isotope analysis; K. Ziegler), and it was determined that NWA 13167 is an ungrouped carbonaceous chondrite of petrologic type 2.

NWA 13167 has a black, highly-porous matrix composed of phyllosilicates, carbonates, Fe-sulfides, and forsteritic olivine, the latter containing FeNi-metal inclusions. Chondrules are small (~300 µm) compared to those in CV and CK chondrites, and CAIs are rare.

An oxygen isotope analysis was conducted at the University of New Mexico (K. Ziegler) employing laser fluorination. Northwest Africa 13167 has an O-isotopic composition that is more 16O-rich than that of CM chondrites and is distinct from both CV and CK chondrites (see diagram below).

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Diagram from MetBull 109

Notably, the oxygen isotope values of NWA 13167 are similar to those of several ungrouped meteorites, including the C-ungrouped NWA 8781 and C3-ungrouped NWA 12416, as shown in the MetBull diagrams below and highlighted in the diagram from Greenwood et al. (2020):

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Diagram from MetBull 107

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Diagram from MetBull 108

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Diagram credit: Greenwood et al., GCA, vol. 277, p. 381 (2020, open access link)
'Linking asteroids and meteorites to the primordial planetesimal population'
(https://doi.org/10.1016/j.gca.2020.02.004)

Other ungrouped meteorites with oxygen isotope values similar to NWA 13167 are the C3-ungrouped Telakoast 001, NWA 13984, and NWA 13671, as shown in the MetBull diagrams below and highlighted in the diagram from Irving et al. (2021):

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Diagram from MetBull 110

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Diagram from MetBull 110

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Diagram from MetBull 110

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Diagram credit: Irving et al., 84th MetSoc, #6218 (2021)

Other C2- and C3-ungrouped meteorites with oxygen isotope values that are 16O-rich similar to NWA 13167 continue to be found, including NWA 13479 and NWA 14179 shown in the MetBull diagrams below:

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Diagram from MetBull 109

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Diagram from MetBull 110

Further isotopic analyses including 54Cr will help resolve any potential genetic relationships that may exist between NWA 13167 and other ungrouped carbonaceous chondrites. Northwest Africa 13167 has experienced a low degree of terrestrial weathering, and it has features indicative of very weak shock (S2). The specimen of NWA 13167 shown above and below is a 10.93 g partially crusted cut stone acquired from Philippe Schmitt-Kopplin. The bottom photo is a scan of NWA 13167 that has been color and contrast adjusted to enhance the interior detail.

NWA 13167 10.93 g Section
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Photos courtesy of Philippe Schmitt-Kopplin

NWA 13167 10.93 g Section, Detail Enhanced
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