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Northwest Africa 7809 | |||||||||||||||||||||||||||||
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Basic information | Name: Northwest Africa 7809 This is an OFFICIAL meteorite name. Abbreviation: NWA 7809 Observed fall: No Year found: 2013 Country: (Northwest Africa) Mass: ![]() | ||||||||||||||||||||||||||||
Classification history: |
This is 1 of 7 approved meteorites classified as EH-melt rock. [show all] Search for other: EH chondrites, Enstatite chondrites, Enstatite chondrites (type 4-7), Enstatite-rich meteorites, and Melted chondrites | ||||||||||||||||||||||||||||
Comments: |
Approved 14 Nov 2013 Revised 11 May 2019: Reclassification | ||||||||||||||||||||||||||||
Writeup![]() |
Writeup from MB 102:
Northwest Africa 7809 (NWA 7809) (Northwest Africa) Purchased: 2013 Feb Classification: Enstatite achondrite (Aubrite) History: Purchased by Jason Utas in February 2013 from a Moroccan dealer at the Tucson Gem and Mineral Show. Physical characteristics: Light colored granular stone (230 g) with orange staining. Petrography: (A. Irving and S. Kuehner, UWS) Relatively equigranular aggregate of predominantly enstatite with accessory albite, Si-bearing kamacite, Ti-Cr-bearing troilite and daubreelite. The specimen is cross-cut by thin goethite veins. Geochemistry: Enstatite (Fs0.3-0.5Wo0.1-0.4). Classification: Aubrite. Specimens: 20.1 g of material and one polished thin section are at UWB. The remaining material is held by JUtas. Writeup from MB 108: NWA 7809: reclassification.
NWA 4799, NWA 7214, NWA 7809, and NWA 11071 contain unfractionated modal abundances of plagioclase, troilite, and metal, which is similar to other enstatite chondrite meteorites. These NWA samples contain higher abundances of metal (7-14 vol.%) compared to aubrites. The only silicate phases in these samples are enstatite and plagioclase, whereas aubrites present olivine and diopside. Meteorites of enstatite chondrite parentage typically do not contain diopside or olivine. Other distinguishing features are metal/troilite ratios and Ti concentrations in troilite. Aubrites contain lower metal/troilite ratios and high Ti in troilite, whereas enstatite chondrite meteorites show the opposite characteristics (as these NWA meteorites do). The metal in these samples presents a higher concentration of Si compared to the aubrites (4 wt.% Si in the NWA samples versus 0.9 wt. % Si in aubrites. Graphite was also observed in these samples, which is not typically found in aubrites. The NWA meteorites show an affinity for an EH chondritic parent body origin, as seen by low Ti in troilite, high Si in metals, the presence of niningerite and graphite, and the lack of diopside and forsterite. As metal and troilite are observed as inclusions within enstatite grains, it suggests the rocks were formed by complete melting. For the complete petrographic, mineralogical and geochemical analyses of these four meteorites, and references to data listed above, see Udry et al. (2019) | ||||||||||||||||||||||||||||
Bibliography: |
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Data from: MB102 Table 0 Line 0: |
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Plots: | O isotopes: | ||||||||||||||||||||||||||||
Institutions and collections |
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012) UWB: University of Washington, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012) JUtas: Jason Utas, United States (private address; updated 8 Jun 2010) |
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Catalogs: |
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References: | Published in Meteoritical Bulletin, no. 102, MAPS 50, 1662, September 2015 Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150
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Geography: |
Statistics: This is 1 of 9116 approved meteorites from (Northwest Africa) (plus 1873 unapproved names) |