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Northwest Africa 16784
Basic information Name: Northwest Africa 16784
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 16784
Observed fall: No
Year found: 2024
Country: (Northwest Africa)
Mass:help 650 g
Classification
  history:
Recommended:  Lunar (troct. melt breccia)    [explanation]

This is 1 of 4 approved meteorites classified as Lunar (troct. melt breccia).   [show all]
Search for other: Lunar meteorites
Comments: Approved 6 Jul 2024
Writeuphelp
Writeup from MB 113:

Northwest Africa 16784 (NWA 16784)

(Northwest Africa)

Purchased: January 2024

Classification: Lunar meteorite (troctolite melt breccia)

History: Acquired in January 2024 by Shun-Chung Yang from Ali Mftah in Algeria.

Physical characteristics: Many pieces with weathered exteriors and no discernable fusion crust.

Petrography: (D. Sheikh, Cascadia) Sample is a polymict breccia comprised of mm to cm-sized lithic (e.g., anorthosites, troctolites, pink spinel troctolites, impact-melt clasts) and mineral (e.g., isolated grains of olivine) clasts set within a dark melt matrix containing some observable vesicles. A variation in the matrix texture was observed across the sample, with at least two noticeable textures: 1) a texture comprised of olivine (~20 μm, ~15 vol. %) and pyroxene (~10 μm, <5 vol. %) poikilitically enclosed within a plagioclase-rich (~80 vol. %) melt; 2) a texture comprised of olivine grains (~20 μm, <5 vol. %) surrounded by radiating laths of plagioclase (~66 vol. %), olivine (~20 vol. %), and minor pyroxene (~9 vol. %) (laths vary from ~1-50 microns in longest dimension). Accessory phases identified throughout the sample include spinel, chromian spinel, Ca-phosphates, troilite, and ilmenite.

Geochemistry: Olivine (Fa25.0±3.5, range Fa15.7-30.6, Fe/Mn = 81±7, n=27), Pigeonite (Fs19.2±4.6Wo14.9±6.2, range Fs10.4-27.2Wo5.4-22.0, Fe/Mn = 56±10, n=10), High-Ca Pyroxene (Fs14.6±5.3Wo34.1±6.7, range Fs6.3-22.1Wo25.1-41.1, Fe/Mn = 58±5, n=6), Calcic Plagioclase (An95.7±0.6, range An94.3-97.2, n=28).

Classification: Lunar (anorthositic troctolite melt breccia) based on the overall predominance of plagioclase, and lesser olivine, within the various melt matrix lithologies according to Stoeffler et al. (1980). Possibly paired with either Touat 008 or NWA 16294 based on similarly described textural and/or chemical features.

Specimens: 21 g at Cascadia, main mass with Shun-Chung Yang.

Bibliography:
  • Stoeffler D., Knoell H.-D., Marvin U.B., Simonds C.H., and Warren, P.H. (1980) Recommended classification and nomenclature of lunar highland rocks - A committee report. In: Conference on the Lunar Highlands Crust, Houston, Tex., November 14-16, 1979, Proceedings. (A81-26201 10-91) New York and Oxford, Pergamon Press, 1980, p. 51-70. (link)
Data from:
  MB113
  Table 0
  Line 0:
Place of purchase:Algeria
Date:P January 2024
Mass (g):650
Pieces:many
Class:Lunar (troct. melt breccia)
Shock stage:high
Weathering grade:moderate
Fayalite (mol%):25.0±3.5
Ferrosilite (mol%):19.2±4.6, 14.6±5.3
Wollastonite (mol%):14.9±6.2, 34.1±6.7
Classifier:D. Sheikh, Cascadia
Type spec mass (g):21
Type spec location:Cascadia
Main mass:Shun-Chung Yang
Comments:CML 1761; submitted by Daniel Sheikh
Institutions
   and collections
Cascadia: Cascadia Meteorite Laboratory, Portland State University, Department of Geology, Room 17 Cramer Hall, 1721 SW Broadway, Portland, OR 97201, United States; Website (institutional address; updated 28 Oct 2011)
Catalogs:
References: Published in Meteoritical Bulletin, no. 113, in preparation (2024)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 9829 approved meteorites from (Northwest Africa) (plus 1851 unapproved names)

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