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Northwest Africa 15468
Basic information Name: Northwest Africa 15468
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 15468
Observed fall: No
Year found: 2022
Country: Mali
Mass:help 30 kg
Classification
  history:
Meteoritical Bulletin:  MB 112  (2024)  OC4-melt breccia
Recommended:  OC4-melt breccia    [explanation]

This is 1 of 6 approved meteorites classified as OC4-melt breccia.   [show all]
Search for other: Melted chondrites, Ordinary chondrites, and Ordinary chondrites (type 4-7)
Comments: Approved 29 Jan 2023
Writeuphelp
Writeup from MB 112:

Northwest Africa 15468 (NWA 15468)

Mali

Find: 2022

Classification: OC4-melt breccia

History: Found at an undisclosed location in Mali in 2022. Most of the material (~30 kg) was purchased from a dealer in Niger by Taleb Ahmed Boulaouane, who sold ~13 kg to Nicholas Gessler. Other material was purchased in June 2022 by Ziyao Wang (1.8 kg) from a meteorite dealer in China and by Shun-Chung Yang (~5 kg) from a dealer in Erfoud, Morocco.

Physical characteristics: The individual dark brown pieces lack fusion crust and some exhibit significant weathering. Interiors of some of the stones are much fresher; cut and polished surfaces have a very distinctive appearance in being overall deep brown in color, but with irregularly-distributed small, shiny metal grains and numerous thin metal coatings or veins along grain or segment boundaries. The proportion of metal to silicate is variable, but is up to ~45 vol.% in some portions.

Petrography: (A. Irving, UWS, P. Carpenter, WUSL and J. Boesenberg, BrownU; A. Greshake, MNB) Three specimens were studied in detail at separate institutions. The unmelted portions of the specimens are composed of well-formed equilibrated chondrules (apparent diameter 500±260 µm, N = 30) containing forsteritic olivine, magnesian orthopyroxene (predominantly enstatite), pigeonite, subcalcic diopside, diopside and devitrified feldspathic glass set in a relatively coarse grained matrix containing abundant kamacite (altered to varying ° to Fe oxides), taenite, chromite, troilite and chlorapatite, but evidently no plagioclase. Partially melted portions have thin metal veins surrounding chondrule-bearing domains. Clasts have shock stage S2.

Geochemistry: Forsterite (Fa8.5±0.4, range Fa8.0-9.2, FeO/MnO = 16-20, N = 20), magnesian orthopyroxene (Fs8.6±1.1Wo0.7±0.5, range Fs7.9-12.3Wo0.2-2.0, FeO/MnO = 10-18, N = 16), magnesian pigeonite (Fs9.6±1.8Wo6.7±0.1, range Fs8.3-10.9Wo6.7-6.6, FeO/MnO = 8-12; Fs6.6Wo17.3, FeO/MnO = 10; N = 3), subcalcic diopside (Fs8.6±0.3Wo25.2±0.2, range Fs8.4-8.8Wo25.7-24.8, FeO/MnO = 12-14, N = 2; Fs5.0±0.2Wo37.0±0.8, range Fs4.7-5.1Wo36.1-37.7, FeO/MnO = 7-9, N = 3), diopside (Fs4.3±1.0Wo43.1±2.5, range Fs3.1-5.7Wo39.9-47.2, FeO/MnO = 6-10, N = 8). Oxygen isotopes (D. Ibarra, BrownU): analyses of both acid-washed and unwashed subsamples of the freshest interior WZY-124 material by laser fluorination gave, the following closely comparable results: unwashed δ17O=4.034, δ18O=6.974, Δ17O=0.366 per mil; acid-washed δ17O=3.909, δ18O=6.608, Δ17O=0.433 per mil (TFL slope value = 0.526). All data were normalized to San Carlos olivine analyzed concurrently, per the recommendations of Sharp and Wostbrock (2021). Magnetic susceptibility was measured at UWB and MNB on the freshest interior material and gave a mean value of log χ (× 10-9 m3/kg)=5.60.

Classification: Ordinary chondrite (OC4-melt breccia). This meteorite has relatively high metal content and magnetic susceptibility. Macroscopic observations show considerable heterogeneity in metal distribution, suggesting the meteorite is a melt breccia. The equilibrated mafic silicate compositions are much more magnesian than observed in H chondrites. The oxygen isotopic composition plots above the terrestrial fractionation line, but it is distant from the established trend for H, L, and LL ordinary chondrites.

Specimens: 112 g including two polished thin sections at UWB; 40 g including one polished thin section at MNB; remainder with Mr. N. Gessler (~13 kg), WangZ (1710 g), Mr. S.-C-Yang (~5 kg) and Mr. Taleb Ahmed Boulaouane (~8 kg).

Data from:
  MB112
  Table 0
  Line 0:
Place of purchase:Niger, China and Erfoud
Date:2022
Mass (g):30000
Pieces:many
Class:OC4-melt breccia
Weathering grade:W1/W3
Fayalite (mol%):8.5±0.4
Ferrosilite (mol%):8.6±1.1
Wollastonite (mol%):0.7±0.5
Magnetic suscept.:5.60
Classifier:A. Irving, UWS, P. Carpenter, WUSL and J. Boesenberg, BrownU; A. Greshake, MNB
Type spec mass (g):152
Type spec location:40 g MNB, 112 g UWB
Main mass:N. Gessler, WangZ, S.-C. Yang, Taleb Ahmed Boulaouane
Comments:Work names WZY-124, BAT-2022-9-16 and SCY-77; submitted by A. Irving and A. Greshake
Plots: O isotopes:  
Institutions
   and collections
MNB: Museum für Naturkunde, Invalidenstraße 43, D-10115 Berlin, Germany (institutional address; updated 24 Dec 2011)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
WUSL: Washington Univ., One Brookings Drive, St. Louis, MO 63130, United States (institutional address; updated 17 Oct 2011)
UWB: University of Washington, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023)
Gessler: Nicholas Gessler, 2010 Calgary Lane, Los Angeles, CA 90077, United States (private address; updated 7 Jul 2016)
BrownU: Joseph Boesenberg Brown University Dept of Earth, Environmental and Planetary Sciences (DEEPS) 324 Brook Street Providence, RI 02912 , United States (institutional address; updated 13 Jun 2024)
WangZ: Ziyao Wang, Hebei GEO University North Campus, Huai An dong road 127, Shijiazhuang, Hebei Province , China (private address; updated 25 Jun 2021)
Catalogs:
References: Published in Gattacceca J., McCubbin F. M., Grossman J. N., Schrader D. L., Cartier C., Consolmagno G., Goodrich C., Greshake A., Gross J., Joy K. H., Miao B. and Zhang B. (2024) The Meteoritical Bulletin, no. 112. Meteoritics & Planetary Science 59, 1820–1823. ?
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Photos:
CreditPhotos
Photos uploaded by members of the Encyclopedia of Meteorites.
    (Caution, these are of unknown reliability)
chen wang                                 
Chunliang Zhang                  
Cyril Chedoz   
Qi Lv               
White Dragon   
Ziyao Wang                        
Public domain photographs:
A. Irving            
Geography:

Mali
Coordinates:Unknown.

Statistics:
     This is 1 of 122 approved meteorites from Mali (plus 2 unapproved names)

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