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Northwest Africa 12907
Basic information Name: Northwest Africa 12907
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12907
Observed fall: No
Year found: 2019
Country: (Northwest Africa)
Mass:help 724 g
Classification
  history:
Meteoritical Bulletin:  MB 109  (2021)  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 29 Feb 2020
Writeuphelp
Writeup from MB 109:

Northwest Africa 12907 (NWA 12907)

(Northwest Africa)

Purchased: 2019

Classification: Primitive achondrite

History: Two single, identically appearing complete stones of 134 and 590 g were purchased from Moroccan dealers in April 2019.

Physical characteristics: Single stone, sand blasted brownish exterior lacking fusion crust. Broken surface reveals poly-phase aggregate of yellow and gray crystals. Many small vugs or vesicles are visible. Very dark patches appear to be shock melt.

Petrography: (C. Agee, UNM; X. Gu, CSU-China) Microprobe examination of a polished mount shows an ultramafic rock with approximately 60% olivine, 30% pyroxene, and 10% alkali-rich glass. Pyroxenes often mantle olivine phenocrysts and are zoned with low calcium pyroxene cores and subcalcic augite rims. Some olivines are euhedral with grain size ~500 μm. Glass of approximately trachytic composition is evenly distributed throughout, primarily in pockets ~100 μm. Troilite is ubiquitous as small (~20 μm) spherical blebs observed mostly in glass, although one large bleb ~1 mm was observed. Trace amounts of kamacite are present.

Geochemistry: (C. Agee, UNM; X. Gu, CSU-China) Olivine Fa20.0±2.6, Fe/Mn=48±4, n=12; low-Ca pyroxene Fs21.6±0.5Wo3.0±0.2, Fe/Mn=29±1, n=4; subcalcic augite Fs22.6±0.2Wo24.1±1.7, Fe/Mn=25±1, n=2; glass SiO2=64.8±0.7, TiO2=0.63±0.7, Al2O3=17.4±0.5, Cr2O3=0.01±0.01, MgO=0.7±0.4, MnO=0.04±0.03, FeO=2.9±1.2, CaO=2.9±0.5, Na2O=8.8±0.3, K2O=1.1±0.5 (wt%), n=6. Oxygen isotopes (K. Ziegler, UNM): 3 acid-washed fragments analyzed by laser fluorination gave δ18O= 4.950, 4.899, 5.195; δ17O= 3.672, 3.652, 3.848; Δ17O=1.058, 1.066, 1.105 (linearized, all per mil, TFL slope=0.528).

Classification: Primitive achondrite. Oxygen isotope values overlap with the L-LL chondrite field. Possibly related to NWA 11042, but not likely paired as it possesses no maskelynite, but does have glassy melt pockets and similar olivine and pyroxene compositions.

Specimens: 20.4 g including a probe mount on deposit at UNM, Zuokai Ke holds the main mass.

Data from:
  MB109
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2019
Mass (g):724
Pieces:2
Class:Achondrite-prim
Shock stage:high
Weathering grade:moderate
Fayalite (mol%):20.0±2.6
Ferrosilite (mol%):21.6±0.5, 22.6±0.2
Wollastonite (mol%):3.0±0.2, 24.1±1.7
Classifier:C. Agee, UNM
Type spec mass (g):20.4
Type spec location:UNM
Main mass:Zuokai Ke
Comments:Field name KE-45; submitted by C. Agee
Plots: O isotopes:  
Institutions
   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)
CSU: Department of Geosciences Colorado State University Fort Collins, CO 80523 , United States (institutional address; updated 21 Jan 2019)
Catalogs:
References: Published in Gattacceca J., McCubbin F. M., Grossman J., Bouvier A., Bullock E., Chennaoui Aoudjehane H., Debaille V., D’Orazio M., Komatsu M., Miao B. and Schrader D. L. (2021) The Meteoritical Bulletin, No. 109. Meteoritics & Planetary Science 56, 1626–1630.
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Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 9790 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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