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Northwest Africa 11042
Basic information Name: Northwest Africa 11042
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11042
Observed fall: No
Year found: 2016
Country: Mauritania
Mass:help 90.1 g
Classification
  history:
Meteoritical Bulletin:  MB 106  (2018)  Achondrite-prim
Recommended:  Achondrite-prim    [explanation]

This is 1 of 12 approved meteorites classified as Achondrite-prim.   [show all]
Search for other: Primitive achondrites
Comments: Approved 13 Feb 2017
Writeuphelp
Writeup from MB 106:

Northwest Africa 11042 (NWA 11042)

Mauritania

Purchased: 2016

Classification: Primitive achondrite

History: Purchased by Abdelhadi Aithiba in Morocco, 2016.

Physical characteristics: Single complete stone covered in black fusion crust. Broken surface reveals a phaneritic mix of pale-yellow olivine grains, light-green pyroxene grains, glassy maskelynite patches, and dark-colored shock melt pockets. A single, fine, dark shock melt vein was also observed in hand sample.

Petrography: (C. Agee, UNM) Microprobe examination of two polished mounts shows an ultramafic rock with approximately 46% olivine, 38% pyroxene, 15% maskelynite and 1% chromite. Fe-sulfide is a minor but ubiquitous phase. Trace amounts of Fe-Ni metal and chlorine-rich apatite are present. Dominant igneous texture consists of poikilitic olivine and pyroxene grains most in the size range 500-1500 μm. Plagioclase has been completely transformed to maskelynite. Maskelynite domains appear smooth and glassy, and are associated with radiating fractures into surrounding olivine and pyroxenes. Shock melt pockets are scattered throughout, some up to ~500 μm in diameter, also surrounded by radiating fractures.

Geochemistry: (C. Agee, M. Spilde, Z. Vaci, UNM) olivine Fa24.6±0.2, Fe/Mn=50±2, n=20; low-Ca pyroxene Fs20.2±0.4Wo4.0±0.4, Fe/Mn=30±2, n=29; augite Fs10.5±0.1Wo39.5±0.1, Fe/Mn=22±1, n=2; maskelynite Ab83.4±1.7An11.9±1.8Or4.8±0.4, n=10. LA-ICPMS (M. Humayun, FSU) Bulk rock: SiO2 46.35, TiO2 0.11, Al2O3 2.34, Cr2O3 0.36, FeO 17.93, MnO 0.43, MgO 28.61, CaO 2.39, Na2O 1.01, K2O 0.07, P2O5 0.08, S 0.31 (all wt%); La 0.40, Ce 1.27, Pr 0.16, Nd 0.84, Sm 0.28, Eu 0.10, Gd 0.41, Tb 0.08, Dy 0.544, Ho 0.12, Er 0.37, Tm 0.06, Yb 0.36, Lu 0.06, Ni 102, Co 26, Th 0.060, U 0.036 (all ppm). Noble gases (D. Weimer, H. Buseman, ETHZ) results on two sample fragments without fusion crust, 20 and 100 mg, gave 129Xe/132Xe= ~1.8, 36Ar/132Xe= ~600, 84Kr/132Xe= 3 (100 mg) and 6 (20 mg); U,Th-He age ~0.2 Ga. Oxygen isotopes (K. Ziegler, UNM): 8 acid-washed fragments analyzed by laser fluorination gave, respectively δ18O= 4.33, 4.45, 4.36, 4.54, 4.64, 4.42, 4.49, 4.46; δ17O= 3.33, 3.38, 3.34, 3.42, 3.52, 3.35, 3.41, 3.36; Δ17O= 1.04, 1.04, 1.04, 1.03, 1.07, 1.02, 1.03, 1.00 (linearized, all per mil, TFL slope=0.528); weighted average δ18O= 4.46; δ17O= 3.34; Δ17O= 1.03.

Classification: Primitive achondrite. Δ17O values coincide with the L-chondrite field. The bulk rock pattern is LREE-depleted as expected for an igneous cumulate rock. Possibly related to NWA 4284, but not paired, as NWA 4284 has no shock melt pockets, no maskelynite, and a higher modal abundance of plagioclase.

Specimens: 18.5 g, including a probe mount, on deposit at UNM, Abdelhadi Aithiba holds the main mass.

Data from:
  MB106
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2016
Mass (g):90.1
Pieces:1
Class:Achondrite-prim
Shock stage:high
Weathering grade:low
Fayalite (mol%):24.6±0.2
Ferrosilite (mol%):20.2±0.4, 10.5±0.1
Wollastonite (mol%):4.0±0.4, 39.5±0.1
Classifier:C. Agee, UNM
Type spec mass (g):18.5
Type spec location:UNM
Main mass:Abdelhadi Aithiba
Comments:Submitted by C. Agee
Plots: O isotopes:  
Institutions
   and collections
TM: Geoscience Museum, Transvaal Museum, P. O. Box 413, Pretoria 0001, South Africa (institutional address; updated 3 Mar 2011)
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015)
FSU: Department of Geological Sciences, Florida State University, Tallahassee FL 32306-4100, United States (institutional address; updated 16 Dec 2010)
Catalogs:
References: Published in Gattacceca J., Bouvier A., Grossman J., Metzler K., and Uehara M. (2019) Meteoritical Bulletin, no. 106. Meteorit. Planet. Sci. 54 in press.
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Geography:

Mauritania
Coordinates:Unknown.

Statistics:
     This is 1 of 101 approved meteorites from Mauritania (plus 1 unapproved name) (plus 2 impact craters)

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