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Northwest Africa 12540 | |||||||||||||||||||||||||||||||
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Basic information | Name: Northwest Africa 12540 This is an OFFICIAL meteorite name. Abbreviation: NWA 12540 Observed fall: No Year found: 2018 Country: (Northwest Africa) Mass: ![]() | ||||||||||||||||||||||||||||||
Classification history: |
This is 1 of 15 approved meteorites classified as Eucrite-an. [show all] Search for other: Achondrites, Eucrites, and HED achondrites | ||||||||||||||||||||||||||||||
Comments: | Approved 12 Apr 2019 | ||||||||||||||||||||||||||||||
Writeup![]() |
Writeup from MB 108:
Northwest Africa 12540 (NWA 12540) (Northwest Africa) Purchased: 2018 Nov Classification: HED achondrite (Eucrite, anomalous) History: Purchased by Aziz Habibi in November 2018 from a Mauritanian dealer. Petrography: (A. Irving and S. Kuehner, UWS; P. Carpenter, WUSL) Recrystallized breccia containing ~8 vol% (estimated from BSE imagery) of Fe-Ni metal (kamacite with taenite). Precursor angular grains of exsolved pigeonite and calcic plagioclase are discernible, but much of the plagioclase has been recrystallized into microgranular aggregates. Accessory phases include silica polymorph, ilmenite and troilite. Magnetic susceptibility log χ (× 10-9 m3/kg) = 4.25 is more than one order of magnitude higher than in the usual eucrites (log χ (× 10-9 m3/kg) = 2.95±0.30, n=70, Rochette et al. 2009) and in agreement with the observed metal content. Geochemistry: Orthopyroxene host (Fs46.3-48.8Wo4.6-1.6, FeO/MnO = 25-26, N = 3), clinopyroxene exsolution lamellae (Fs19.5-22.9Wo42.7-38.8, FeO/MnO = 23-25, N = 3), plagioclase (An88.3-89.8Or0.3), kamacite (Ni = 4.3 wt.%), taenite (Ni = 51.0 wt.%). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave δ17O 1.778, 1.909, 1.786; δ18O 3.911, 4.120, 3.936; Δ17O -0.287, -0.266, -0.292 per mil. Classification: Eucrite (anomalous, annealed metal-rich breccia). This specimen has an unusually high amount of Ni-bearing metal and also exhibits extensive post-brecciation annealing textures. Specimens: 26.8 g including one polished thin section at UWB; remainder with Mr. A. Habibi. | ||||||||||||||||||||||||||||||
Data from: MB108 Table 0 Line 0: |
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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) 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, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012) |
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Catalogs: |
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References: | Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150
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Photos: |
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Geography: |
Statistics: This is 1 of 9305 approved meteorites from (Northwest Africa) (plus 1873 unapproved names) |