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Northwest Africa 12338
Basic information Name: Northwest Africa 12338
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12338
Observed fall: No
Year found: 2016
Country: (Northwest Africa)
Mass:help 1127 g
Meteoritical Bulletin:  MB 107  (2018)  Achondrite-ung
Recommended:  Achondrite-ung    [explanation]

This is 1 of 101 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 11 Dec 2018
Writeup from MB 107:

Northwest Africa 12338 (NWA 12338)

(Northwest Africa)

Purchased: 2016 Nov

Classification: Ungrouped achondrite

Physical characteristics: The repository specimen has a brown fusion crust surface and a light-gray, fresh interior.

Petrography: (Z.G. Guo, UWO) This is an unbrecciated basaltic meteorite with fine-grained ophitic texture including ~100 μm-sized clinopyroxene (~55%), and 100-500 μm-sized plagioclase (~35%). Plagioclase is not acicular, as usually found in eucrites, but instead is interstitial between clinopyroxene crystals. Olivine (~5%) is found as ~100 μm individual crystals. It has a low content (<1%) of metal (partially weathered), chromite and troilite. Undulatory (up to mosaic) extinction is observed in plagioclase, with silica veinlets, which indicate a moderate shock stage.

Geochemistry: (EMPA, Z.G. Guo and M. Beauchamp, UWO) Olivine Fa70.0±0.2, Fe/Mn=44±1 (n=10); pigeonite Fs40.5±3.3Wo10.6±4.1, Fe/Mn=30±1 (n=20); plagioclase An89.1±1.4 (n=10); Bulk chemistry (INAA, R. Korotev, WashU) Na2O 0.495%, CaO 10.2%, FeO 15.3%, and (all in ppm) Cr 3043, Co 16, Sr 92, Ba 19, La 1.05, Sm 0.74, Hf 0.52, Th 0.10, and U 0.16. (laser fluorination oxygen isotope analyses, A. Alexandre; L. Webb, UWO) acid-washed bulk rock powder Δ17O=-0.18±0.01, δ17O=1.980±0.203, δ18O=4.16±0.37 (n=2).

Classification: Achondrite, ungrouped. This meteorite is an anomalous eucrite-like basaltic meteorite similar to other specimens which have been found to diverge from the HED oxygen mass fractionation line (similarly to PCA 91007 and Pasamonte, and significantly above the HED line). It has geochemical characteristics of eucrites for major element mineral compositions, and of cumulate eucrites for bulk trace element chemistry. But its mineral sssemblage with the presence of igneous olivines, texture, and its oxygen isotopic composition indicate a different parent body from HED, thus an ungrouped achondrite classification.

Specimens: 24.0g at UWO including a probe mount.

Data from:
  Table 0
  Line 0:
Place of purchase:Erfoud, Morocco
Date:P 2016 Nov
Mass (g):1126.5
Shock stage:moderate
Weathering grade:low
Fayalite (mol%):70.0±0.2 (N=10)
Ferrosilite (mol%):40.5±3.3 (N=20)
Wollastonite (mol%):10.6±4.1 (N=20)
Classifier:Z.G. Guo, UWO
Type spec mass (g):24.0
Type spec location:UWO
Main mass:S. Tutorow
Comments:G688; submitted by A. Bouvier
Plots: O isotopes:  
   and collections
UWO: University of Western Ontario, Department of Earth Sciences, BGS 1026, 1151 Richmond St. N, London, Ontario, Canada N6A 5B7, Canada (institutional address; updated 18 Jul 2015)
WashU: Washington Univ., One Brookings Drive, St. Louis, MO 63130, United States (institutional address; updated 17 Oct 2011)
References: Published in Meteoritical Bulletin, no. 107, MAPS 55, 460-462
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     This is 1 of 7655 approved meteorites from (Northwest Africa) (plus 1972 unapproved names)

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