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Northwest Africa 8691
Basic information Name: Northwest Africa 8691
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 8691
Observed fall: No
Year found: 2014
Country: (Northwest Africa)
Mass:help 66 g
Meteoritical Bulletin:  MB 104  (2015)  LL4-6
Recommended:  LL4-6    [explanation]

This is 1 of 91 approved meteorites classified as LL4-6.   [show all]
Search for other: LL chondrites, LL chondrites (type 4-7), Ordinary chondrites, and Ordinary chondrites (type 4-7)
Comments: Approved 16 Apr 2015
Writeup from MB 104:

Northwest Africa 8691 (NWA 8691)

(Northwest Africa)

Purchased: 2014

Classification: Ordinary chondrite (LL4-6)

History: One subrounded stone weighing 66 g was found in Morocco in 2014. David Holden acquired the sample from a meteorite prospector in Erfoud 2014.

Physical characteristics: The stone is orangish-brown and has a rounded-angular shape. There is no relict fusion crust remaining on the exterior. The cut face of the interior of the stone is orangish-brown and shows chondrules, clasts and fresh flakes of metal.

Petrography: Description and classification (A. Love, App): Sample displays brecciated structure containing chondrules, chondrule fragments and light and dark-colored clasts of various petrologic grades set within an oxidized, fine-grained fragmental matrix containing ~1.5 vol% FeNi metals. Clasts display weakly to totally recrystallized chondritic textures and shock-darkened and shock melted textures. Weakly recrystallized clasts display distinct chondrules in a recrystallized matrix. Totally recrystallized clasts lack distinct chondrules and have plagioclase grains with an average largest dimension of 43.45 μm. Chondritic host rock contains well-defined chondrules with average diameter of 0.7 mm. Three porphyritic pyroxene chondrules with zoned phenocrysts and low Fs compositions (Fs7.25-17.09) were observed within the matrix.

Geochemistry: (A.Love, App) Olivine Fa34.2±0.7, N=16; Low Ca pyroxene Fs24.3±0.9Wo3.4±1.9, N=7; Fs10.7±4.5Wo1.0±0.2, N=3. Mean olivine composition is outside normal range for LL chondrites. Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively, δ17O = 3.963, 4.079, 3.892; δ18O = 5.916, 5.731, 5.349; Δ17O = 0.839, 1.053, 1.068 (all per mil). Average of triplicate analyses of acid-washed subsamples by laser fluorination gave, respectively, δ17O = 3.978; δ18O = 5.665; Δ17O = 0.987 (all per mil). Oxygen isotopes plot in LL region above the TFL.

Specimens: An endcut slice and small fragments weighing 12.99 g, a polished mount and polished thin section are currently on deposit at App.

Data from:
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2014
Mass (g):66
Shock stage:S3
Weathering grade:W2
Fayalite (mol%):34.2±0.7
Ferrosilite (mol%):24.3±0.9,10.7±4.5
Wollastonite (mol%):3.4±1.9; 1.0±0.2
Classifier:A. Love, App
Type spec mass (g):13.5
Type spec location:App
Main mass:David Holden
Comments:Submitted by Anthony Love
Plots: O isotopes:  
   and collections
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015)
App: Department of Geology, 572 Rivers St., Appalachian State University, Boone, NC 28608, United States (institutional address; updated 7 Mar 2013)
References: Published in Meteoritical Bulletin, no. 104, MAPS 52, 2284, Octover 2017, http://onlinelibrary.wiley.com/doi/10.1111/maps.12930/full
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     This is 1 of 9776 approved meteorites from (Northwest Africa) (plus 1862 unapproved names)

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