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Northwest Africa 11992
Basic information Name: Northwest Africa 11992
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11992
Observed fall: No
Year found: 2007
Country: (Northwest Africa)
Mass:help 337 g
Classification
  history:
Recommended:  LL3    [explanation]

This is 1 of 295 approved meteorites classified as LL3.   [show all]
Search for other: LL chondrites, LL chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Comments: Approved 9 Oct 2018
Writeuphelp
Writeup from MB 107:

Northwest Africa 11992 (NWA 11992)

(Northwest Africa)

Purchased: 2007, Sept

Classification: Ordinary chondrite (LL3)

History: Found in northwest Africa, donated to Cascadia July 2012.

Physical characteristics: In cut slices, exterior is dark gray and shiny, interior is gray with well-defined chondrules and has less metal than typically observed in fresh ordinary chondrites. Minimal weathering staining.

Petrography: (A. Ruzicka, S. Goudy, Cascadia) Thin section shows well-defined chondrules with cluster chondrite texture and little intervening matrix. Glassy chondrule mesostases present but not abundant. Roughly half of low-Ca pyroxene grains show twinning suggestive of clinoenstatite polytype. Shock stage is S4. Shock effects are heterogeneous with S1 and S4 olivine grains predominant. Some bleached chondrules. Minimal weathering effects.

Geochemistry: (M. Hutson, Cascadia) Olivine (Fa30.0±4.0, N = 140; Cr2O3 0.05±0.02 wt%, N = 56), low-Ca pyroxene (Fs20.2±6.8Wo1.4±1.1, N = 143).

Classification: LL3 chondrite, estimated subtype 3.7. Iron contents in olivine and low-Ca pyroxene unusually high for LL3. LL indicated by low metal content and low weathering grade and overlap with LL for olivine Fa and low-Ca pyroxene Fs. Type 3 indicated by texture, presence of chondrule glass, abundance of clinoenstatite, and variable olivine and pyroxene compositions. Subtype indicators can be best reconciled with subtype of 3.7 to 3.8: Fa contents suggest 3.7-3.9, Fs contents suggest 3.4-3.9, olivine chrome contents suggest 3.5.

Specimens: A total of 22.7 g in one slice, a polished thin section, and potted butt are available at Cascadia. Mr. McKenzie holds the main mass.

Data from:
  MB107
  Table 0
  Line 0:
Place of purchase:Denver
Date:P 2007, Sept
Mass (g):337
Pieces:1
Class:LL3
Shock stage:S4
Weathering grade:W1
Fayalite (mol%):30.0
Ferrosilite (mol%):20.2
Wollastonite (mol%):1.4
Classifier:M. Hutson, S. Goudy, A. Ruzicka, Cascadia
Type spec mass (g):22.7
Type spec location:Cascadia
Main mass:Mr. Ronnie McKenzie, Pretoria, South Africa
Comments:Specimen numbers RM-4 and CML0677.; submitted by Alex Ruzicka
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. 107, in preparation (2018)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 6438 approved meteorites from (Northwest Africa) (plus 2025 unapproved names)

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