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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
Recommended:  Achondrite-prim    [explanation]

This is 1 of 14 approved meteorites classified as Achondrite-prim.   [show all]
Search for other: Primitive achondrites
Comments: Approved 29 Feb 2020
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:
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2019
Mass (g):724
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:  
   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)
References: Published in Meteoritical Bulletin, no. 109, in preparation (2020)
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     This is 1 of 7552 approved meteorites from (Northwest Africa) (plus 1969 unapproved names)

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