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Northwest Africa 8159
Basic information Name: Northwest Africa 8159
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 8159
Observed fall: No
Year found: 2013
Country: Morocco
Mass:help 149.4 g
Meteoritical Bulletin:  MB 102  (2013)  Martian (augite basalt)
Recommended:  Martian (augite basalt)    [explanation]

This is the only approved meteorite classified as Martian (augite basalt).
Search for other: Martian meteorites
Comments: Approved 10 Dec 2013
Writeup from MB 102:

Northwest Africa 8159 (NWA 8159)


Purchased: 2013

Classification: Martian (augite basalt)

History: Purchased by Brahim Tahiri from a Moroccan hunter and sent to his partner Sean Tutorow for classification in 2013.

Physical characteristics: Single stone, weathered exterior with yellow-brown patina, light colored desert soil coating on one side. Saw cut reveals a very fine-grained, gray-green interior, with a few small melt veins present, but one vein was up to 1 mm thick, lithology offsets at vein boundaries suggest slight brecciation.

Petrography: (C. Agee, UNM) Microprobe examination of a two polished mounts shows intergranular texture with approximately 50% augite, 40% plagioclase and maskelynite, 5% olivine. Augites have equant habits 10-200 μm with igneous zoning. Some augite crystals are rimmed with Fs-rich orthopyroxene. Plagioclase with shock-fractured prismatic laths up to 500 × 100 μm, but many are smaller (~50 × 10 μm), approximately half of the plagioclase has been converted to maskelynite, and is observed as unfractured, glassy casts. Olivine ~100 μm, most with resorbed or coronal grain boundaries. Ubiquitous magnetite, most grains 10-100 μm. Minor ilmenite, merrillite, Cl-apatite, and Cr-spinel. Trace calcite and barite assumed to be desert weathering products.

Geochemistry: (C. Agee, N. Muttik, F. McCubbin, UNM) EMPA. Augite Fs38.6±11Wo30.4±11.0, Fe/Mn=36±4, n=78; orthopyroxene rims Fs62.3±5.9Wo0.6±0.3, Fe/Mn=23±3, n=6; plagioclase An58.2±2.3Ab41.5±2.4Or0.3±0.2, n=7; maskelynite An58.1±1.8Ab41.6±1.7Or0.2±0.0, n=5; olivine Fa66.2±3.8, Fe/Mn=50±5, n=15; large shock melt vein (mean value from EMPA with 20 μm beam) SiO2=46.14±0.94, TiO2=0.67±0.09, Al2O3=10.63±1.22, Cr2O3=0.14±0.02, FeO=24.89±1.92, MnO=0.50±0.04, MgO=4.02±0.39, CaO=9.10±0.38, Na2O=1.80±0.17, P2O5=0.29±0.03, Cl=0.067±0.022 (all wt%), n=10. (Karen Ziegler, UNM) Oxygen isotope values of 5 acid-washed aliquots of bulk sample, 1.2, 1.2, 1.8, 2.0, 1.0 mg, gave δ17O = 2.406, 2.405, 2.093, 2.532, 2.329, δ18O = 4.089, 3.947, 3.328, 4.197, 3.880, Δ17O = 0.247, 0.321, 0.336, 0.316, 0.280 (linearized, all permil).

Classification: Martian (augite basalt). This is a martian meteorite based on oxygen isotopes, Fe/Mn of augite and olivine, and An-content of plagioclase and maskelynite. This martian meteorite is a fine grained olivine-bearing augite basalt that does not appear to be a SNC type although there are some aspects of it that resemble SNC. The augite and olivine compositions and crystallization trends are similar to nahklites, in particular MIL 03346. It does not resemble most shergottites in that pigeonite is absent, and orthopyroxene is only a minor phase present as Fe-rich rims on some augite grains, however plagioclase compositions are similar to shergottites, in particular the low potassium labradorites in QUE 94201. Shock pressures appear to have been lower than for shergottites, perhaps similar to Chassigny and some nakhlites, as only about half the plagioclase has been transformed to maskelynite. Magnetite is the dominant oxide phase in this meteorite, the only other martian meteorite that shares this aspect is basaltic breccia NWA 7034 and its pairings.

Specimens: 24.57 g including a two probe mounts on deposit at UNM, Reed holds 2.21 g, Sean Tutorow holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2013
Mass (g):149.39
Class:Martian (augite basalt)
Classifier:C. Agee, UNM
Type spec mass (g):24.57
Type spec location:UNM
Main mass:Sean Tutorow
Comments:Submitted by C. Agee
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)
Reed: Blaine Reed, P.O. Box 1141, Delta, CO 81416, United States; Website (private address)
References: Published in Meteoritical Bulletin, no. 102, MAPS 50, 1662, September 2015
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     This is 1 of 2089 approved meteorites from Morocco (plus 32 unapproved names) (plus 1 impact crater)

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