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Northwest Africa 12522
Basic information Name: Northwest Africa 12522
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12522
Observed fall: No
Year found: 2018
Country: Algeria
Mass:help 1128 g
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 186 approved meteorites (plus 1 unapproved name) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 27 Mar 2019
Writeup from MB 108:

Northwest Africa 12522 (NWA 12522)


Purchased: 2018

Classification: Martian meteorite (Shergottite)

History: Two complete stones purchased by Jay Piatek from Abdelhadi Aithiba in Morocco, November 2018. The two stones were found together in the Algerian Desert near Ouargla, reportedly as part of a find of several stones with total mass of ~9 kg.

Physical characteristics: The two stones, 1071 g and 57 g, are both covered in fusion crust. The larger stone has smooth, wind-polished fusion crust on about 10% of its surface. The rest of the stone appears to have been buried in the sand and not wind-polished, but has instead extremely fresh and shiny black fusion crust. Flow lines and roll-over edges are present in this fusion crust. The smaller stone may have been completely buried in the sand as it has only very fresh-appearing fusion crust and one small chipped area which exposes the interior. Broken surfaces on both stones reveal shiny maskelynite patches that are visible with the naked eye. A piece of the fusion crust was imaged using BSE, showing it to be highly vesicular with average thickness ~450 μm.

Petrography: (C. Agee, UNM) The two major phases in this meteorite are clinopyroxene and maskelynite. Ubiquitous minor phases are merrillite, apatite, titanomagnetite, ilmenite, and troilite. The clinopyroxene has a modal abundance of approximately 60%, with significant core to rim zoning observed in backscatter electron images, indicating an igneous crystallization trend with Mg-rich pigeonite cores, mantled by augite, and rimmed with ferropigeonite. Clinopyroxene average grain sizes are approximately 300-500 μm. Maskelynite has modal abundances of approximately 30%, and most grains are thin and elongate with maximum length ~1 mm. Merrillite is about five times more abundant than apatite in this sample.

Geochemistry: (C. Agee, UNM) Clinopyroxene Fs43.8±19.1Wo21.8±6.7, core to rim range Fs30.2Wo13.6 (Mg-pigeonite) - Fs22.6Wo38.7 (augite) - Fs78.4Wo4.6 (ferropigeonite), Fe/Mn=33±5, n=48; maskelynite An50.7±2.7Ab47.6±2.2Or1.7±0.6, n=17; fusion crust (20 μm defocused electron beam) SiO2=45.4±1.0, TiO2=1.2±0.3, Al2O3=7.3±2.1, Cr2O3=0.10±0.10, MgO=7.0±3.9, FeO=21.0±1.4, MnO=0.52±0.04, CaO=9.9±0.0, Na2O=1.5±0.5 (all wt%), n=11; merrillite CaO=46.4±0.4, P2O5=44.4±0.3, FeO=5.2±0.4, MgO=0.7±0.3, Na2O=1.5±0.1, (all wt%), n=19; apatite CaO=53.3±0.3, P2O5=40.5±0.1, FeO=1.3±0.1, MgO=0.2±0.2, Na2O=0.12±0.04, SiO2=0.87±0.06, F=1.2±0.1, Cl=2.3±0.2, (all wt%), n=4; titanomagnetite FeO=54.0±3.0, Fe2O3=15.1±6.4, TiO2=26.6±5.0, Al2O3=1.8±1.8±0.4, MnO=0.57±0.06, (all wt%), n=27; ilmenite FeO=49.4±0.7, TiO2=48.5±1.4, MnO=0.77±0.03, (all wt%), n=4. Oxygen isotopes (K. Ziegler, UNM): acid-washed fragment analyzed by laser fluorination gave δ18O= 4.426; δ17O= 2.567; Δ17O= 0.230 (linearized, per mil, TFL slope=0.528).

Classification: Geochemically evolved pyroxene-phyric basalt, clinopyroxene compositional zoning trends are similar to QUE 94201, maskelynite composition is similar to Los Angeles.

Specimens: 21 g including a probe mount on deposit at UNM, Jay Piatek holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2018
Mass (g):1128
Class:Martian (shergottite)
Shock stage:high
Weathering grade:low
Ferrosilite (mol%):43.8±19.1
Wollastonite (mol%):21.8±6.7
Classifier:C. Agee, UNM
Type spec mass (g):21
Type spec location:UNM
Main mass:Jay Piatek
Comments:Field name AB300; submitted by C. Agee, UNM
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)
References: Published in Meteoritical Bulletin, no. 108, in preparation (2019)
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     This is 1 of 958 approved meteorites from Algeria (plus 26 unapproved names) (plus 4 impact craters)

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