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Northwest Africa 10416
Basic information Name: Northwest Africa 10416
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 10416
Observed fall: No
Year found: 2015
Country: Mali
Mass:help 964 g
Meteoritical Bulletin:  MB 104  (2015)  Martian
Recommended:  Martian    [explanation]

This is 1 of 3 approved meteorites classified as Martian.   [show all]
Search for other: Martian meteorites
Comments: Approved 26 Dec 2015
Writeup from MB 104:

Northwest Africa 10416 (NWA 10416)


Purchased: April 2015

Classification: Martian meteorite

History: Reportedly found in Mali, purchased by Darryl Pitt.

Physical characteristics: Irregular, desert-varnished exterior without fusion crust. A saw cuts reveal green-orange olivine phenocrysts set in a groundmass of white plagioclase and light green pyroxene. Fine, dark, shock-melt veins are present.

Petrography: (C. Agee, UNM) This is an olivine basalt with ~10% olivine phenocrysts (~1 mm in diameter), and intergranular clinopyroxene (~50%) and labradorite plagioclase (~30%). The olivines and clinopyroxenes show igneous zoning. The clinopyroxenes have Mg-rich pigeonite cores and Fe, Ca-rich rims, some of the rims are augitic. Approximately ~10% of the plagioclase has been transformed to maskelynite. Maskelynite occurs primarily in contact with, or near shock melt veins. There is a significant amount of secondary alteration present in the olivines and plagioclase. The olivine alteration occurs primarily in the cores of grains, giving low microprobe totals, and is orange in color (olivine rims are unaltered, give normal totals, are transparent and green in color). The plagioclase alteration occurs in at least 50% of the grains observed, shows low microprobe totals, and depletion of Na and K relative to unaltered labradorite domains. Accessory ilmenite, Ti-Cr-Al-Fe spinel, chromite, and Fe-sulfide were observed throughout the sample.

Geochemistry: (C. Agee and N. Muttik, UNM) Olivine Fa50.7±7.5, Fe/Mn=57±2, n=19; clinopyroxene Fs27.6±7.0Wo9.7±8.0, Fe/Mn=32±2, n=128; plagioclase An63.5±4.3.1Ab36.0±4.2Or0.5±0.1, n=9. Shock melt vein (20 μm electron microprobe beam size) SiO2 47.3±2.3, TiO2 0.53±0.25, Cr2O3 0.42±0.17, Al2O3 15.9±2.6, MgO 10.2±2.0, FeO 14.1±3.2, MnO 0.33±0.06, NiO 0.01±0.01, CaO 8.8±1.3, Na2O 1.56±0.60, K2O 0.07±0.3, n=26. Bulk composition by quad ICPMS (L. Borg, LLNL) Mg 98729±6562, Al 31142±1894, Ca 46482±3540, Ti 3540±180, Mn 3687±212, Fe 132424±8398, La 0.22±0.01, Ce 0.59±0.04, Pr 0.11±0.01, Nd 0.79±0.02, Sm 0.61±0.03, Eu 0.35±0.01, Gd 1.16±0.06, Tb 0.30±0.01, Dy 2.15±0.05, Ho 0.46±0.02, Er 1.36±0.04, Tm 0.19±0.01, Yb 1.25±0.06, Lu 0.19±0.01 (all ppm, 2-sd). Oxygen isotopes (K. Ziegler, UNM) were performed on two types of material: 1) relatively unaltered material and 2) altered material with many orange olivine fragments. All samples were acid-washed and analyzed by laser fluorination. 1) "Unaltered" material: δ18O=4.539, 4.445, 4.392, 4.740, 4.627, 4.310, 4.500; δ17O=2.668, 2.674, 2.573, 2.760, 2.716, 2.500, 2.630; Δ17O=0.271, 0.327, 0.254, 0.257, 0.273, 0.224, 0.254; 2) "altered olivine" material: δ18O= 4.592, 7.323, 6.592, 8.214, 7.012, 6.091; δ17O =2.609, 4.041, 3.635, 4.471, 3.850, 3.353; Δ17O= 0.184, 0.174, 0.154, 0.134, 0.148, 0.137 (linearized, all per mil).

Classification: Martian. This is a martian meteorite based on oxygen isotopes, Fe/Mn of clinopyroxene and olivine, and An-content of plagioclase. This martian meteorite is unlike shergottite basalts in that only about 10% of the plagioclase has been converted to maskelynite. Shock pressures appear to have been lower than for shergottites and in this regard it most resembles NWA 8159. Like NWA 8159, this meteorite also shows a significant LREE-depletion. The altered olivine cores in this meteorite are inconsistent with terrestrial weathering which would normally show chemical attack on the outer surfaces or along internal fractures. The unaltered and altered domains in this sample have different oxygen isotope values, unaltered material gives values that fall within the range of SNC meteorites, whereas altered olivine material shows a much wider range of δ18O values (up to 8.214 permil).

Specimens: 31.0 g including several probe mounts and polished thin sections on deposit at UNM, DPitt holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P April 2015
Mass (g):963.8
Shock stage:high
Weathering grade:moderate
Fayalite (mol%):50.7±7.5
Ferrosilite (mol%):28.5±7.9
Wollastonite (mol%):7.7±5.2
Classifier:C. Agee, UNM
Type spec mass (g):31.0
Type spec location:UNM
Main mass:Darryl Pitt
Comments:Submitted by C. Agee
Plots: O isotopes:  
   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)
DPitt: Darryl Pitt, 225 West 83rd Street, New York, NY 10024, United States; Website (private address)
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 122 approved meteorites from Mali (plus 2 unapproved names)

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