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Northwest Africa 12869
Basic information Name: Northwest Africa 12869
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12869
Observed fall: No
Year found: 2019
Country: Mali
Mass:help 4.3 kg
Meteoritical Bulletin:  MB 108  (2020)  Achondrite-prim
Recommended:  Achondrite-prim    [explanation]

This is 1 of 16 approved meteorites classified as Achondrite-prim.   [show all]
Search for other: Primitive achondrites
Comments: Approved 21 Sep 2019
Writeup from MB 108:

Northwest Africa 12869 (NWA 12869)


Purchased: 2019

Classification: Primitive achondrite

History: Single stone purchased by Abdelhadi Aithiba in Taoudenni, Mali, 2019.

Physical characteristics: Dark brown, weathered, irregular shaped exterior. Broken surfaces show dark brown, green, and honey-colored grains.

Petrography: (C. Agee, UNM) This meteorite contains approximately 70% olivine, 20% low-Ca pyroxene, 5% plagioclase, and 10% kamacite+troilite. The texture is poikiolitic to equigranular with typical grain sizes 100-500 μm. Many triple junctions are present. Fine crosscutting Fe-oxide veinlets were seen throughout. No chondrules observed.

Geochemistry: (C. Agee, UNM) Olivine Fa34.7±0.2, Fe/Mn=86±5, n=10; low-Ca pyroxene Fs26.2±1.3Wo3.6±0.4, Fe/Mn=58±8, n=6; plagioclase An47.4±0.5Ab51.5±0.5Or1.2±0.1, n=4. Oxygen isotopes (K. Ziegler, UNM): 3 acid-washed fragments analyzed by laser fluorination gave δ18O= 3.668, 3.584, 3.181; δ17O= 0.225, 0.170, -0.072; Δ17O= -1.712, -1.722, -1.752 (linearized, per mil, TFL slope=0.528).

Classification: Primitive achondrite. This a plagioclase-bearing harzburgite with oxygen isotopes similar to CR/CH chondrites, however the high Fa-content and Fe/Mn of olivine is inconsistent with a direct genetic link to CR/CH. Possibly paired with or related to NWA 3250 and NWA 6901, and broadly similar in geochemistry to other primitive achondrites that have olivine compositions ~Fa30-35 and oxygen isotopes in the vicinity of the CR/CH field such as NWA 3100 and Tafassasset.

Specimens: 22 g including a probe mount on deposit at UNM, Abdelhadi Aithiba holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Mali
Date:P 2019
Mass (g):4300
Shock stage:low
Weathering grade:moderate
Fayalite (mol%):34.7±0.2
Ferrosilite (mol%):26.2±1.3
Wollastonite (mol%):3.6±0.4
Classifier:C. Agee, UNM
Type spec mass (g):22
Type spec location:UNM
Main mass:Abdelhadi Aithiba
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)
References: Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150
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     This is 1 of 122 approved meteorites from Mali (plus 2 unapproved names)

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