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Northwest Africa 13411
Basic information Name: Northwest Africa 13411
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 13411
Observed fall: No
Year found: 2018
Country: Morocco
Mass:help 264 g
Recommended:  OC5-an    [explanation]

This is the only approved meteorite classified as OC5-an.
Search for other: Ordinary chondrites, Ordinary chondrites (type 4-7)
Comments: Approved 22 Nov 2020
Writeup from MB 109:

Northwest Africa 13411 (NWA 13411)

Western Sahara, Morocco

Purchased: 2018

Classification: OC5-an

History: The 190.96 and 73.03 g samples were found near Adrar, Algeria, by a meteorite prospector in 2018. Dave Lehman and his partner acquired the samples from the finder.

Physical characteristics: Samples are irregularly shaped and brown. Interior of sample is orangish brown and contains abundant chondrules and weathered metal and sulfides.

Petrography: Description and Classification (A. Love, App) Sample has a chondritic texture composed of numerous close-packed equilibrated chondrules set within a comminuted matrix of the chondritic lithology. This matrix is crosscut by ubiquitous FeNiOH veinlets. When viewed using backscattered electron imaging, the olivines and pyroxene have almost identical gray-scale colors. The sample is composed of BO, PO (dominant), PP (clinoenstatite is rare but present) and rare Al-rich chondrules with an average apparent diameter of 395±219 µm (n=131). Some pyroxenes are zoned from enstatite cores to augite rims. The sample contains secondary plagioclase with an average grainsize of 29 µm (n=15). Additional minerals are: chromite, K-rich feldspar, apatite, kamacite, taenite, troilite and gypsum. Despite a comprehensive search for reduced sulfide and phosphide phases commonly associated with enstatite and forsterite chondrites, none were found in this sample.

Geochemistry: (A. Love, App) Olivine (Fa8.35±0.15, Fe/Mn=16.97±0.58, n=18), low-Ca pyroxene (Fs8.47±0.26Wo1.09±0.32, Fe/Mn=10.78±0.39, n=18); high-Ca pyroxene rims (Fs3.44±0.08Wo46.93±2.71, n=4). plagioclase of variable composition (Ab18.17-83.41Or0.66-12.88, n=6); FeNi metal (6.71±0.21wt% Ni and 1.09±0.02wt% Co, n=9). Oxygen Isotopes: (Karen Ziegler, UNM) analyses of acid-washed subsamples by laser fluorination gave (all per mill): δ17O=4.199, 3.277, 3.836, 3.592, 3.666, 3.102; δ18O=5.891, 5.520, 6.526, 5.464, 6.433, 5.240; Δ17O=1.089, 0.362, 0.390, 0.707, 0.269, 0.335.

Classification: Ordinary chondrite (OC5-an, C-S2, W3) Based on chondritic texture and presence of weathered and unweathered metal, this sample has similarities with ordinary chondrites. Based on mineral compositions and oxygen isotopes, this is an anomalous ordinary chondrite. Equilibrated compositions and grainsize of secondary plagioclase indicate this sample corresponds to petrologic type 5. Oxygen isotope compositions plot at a distance from the slope 1 line for equilibrated ordinary chondrites. Mean Δ17O composition is below the standard range for unequilibrated H chondrites and the standard deviation of the Δ17O is higher than that recorded in the entire range of unequilibrated ordinary chondrites. Co concentrations in kamacite fall between values measured in L and LL chondrites (Rubin, 1990).

Specimens: Dave Lehman and a partner hold the main mass. Two slices totaling 25.08g and a polished thin section and mount are on deposit at App.

Data from:
  Table 0
  Line 0:
State/Prov/County:Western Sahara
Date:P 2018
Mass (g):264.2
Shock stage:C-S2
Weathering grade:W3
Fayalite (mol%):8.3±0.1
Ferrosilite (mol%):8.5±0.3; 3.4±0.1
Wollastonite (mol%):1.1±0.3; 46.9±2.7
Magnetic suscept.:5.01
Classifier:A. Love, App
Type spec mass (g):25.08
Type spec location:App
Main mass:Dave Lehman
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. 109, in preparation (2020)
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     This is the only approved meteorite from Western Sahara, Morocco
     This is 1 of 1556 approved meteorites from Morocco (plus 22 unapproved names) (plus 1 impact crater)

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