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Northwest Africa 1670 meteorite (NWA 1670), Northwest Africa Meteorites

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Non-native locality type:Meteorite
Meteorite Type:Angrite


Angrite, Quenched (achondrite)
Find, 2003; 29 g

Northwest Africa 1670 (NWA 1670) is a single stone brought from the desert of northern Africa and sold in Erfoud, Morocco. The fusion crust is nearly gone, but the interior does not appear heavily weathered. The porphyritic interior hosts a number of prominent olivine xenocrysts as well as less prominent pyroxene xenocrysts. The phenocrysts are significantly more Mg-rich than the less prominent, smaller crystals and grains of the very fine-grained groundmass. The groundmass hosts bundles of fassaite-plagioclase intergrowths and dendritic olivine as well as small anorthite microcrysts. Minor kirschteinite appears as a late phase. Minor and very minor accessories include chromite, hercynite, kamacite,Ti-magnetite, and various spinels. Ca-carbonates are also reported, but are not mineralogically characterized in the cited sources. The carbonates have suggested to some authors that some unusual features of the angrite group may be due to carbonized melts — possible meteoritic analogues of terrestrial melilites or, even, carbonatites.

NWA 1670 is one of 15 recovered angrite meteorites. [8 angrites are apparently fragments of a single fall.] The fine-grained groundmass and various textures due to the rapid cooling of NWA 1670 and a few other angrites have occasioned the distinction between 'plutonic' angrites and 'quench' angrites. The 'quench' angrites include D'Orbigny, NWA 1296 and several other angrites [Cf. Grady et al., 2015]. Crystallization ages of ~4.62-4.64 Ga have been reported for several of the quench angrites, including NWA 1670, making them some of the oldest dated rocks of the Solar System.

Mineral List


12 valid minerals.

Meteorite/Rock Types Recorded

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References

Mikouchi, T., McKay G., Koizumi E., Monkawa, A. & Miyamoto, M. (2003) Northwest Africa 1670: A new quenched angrite. Meteoritics & Planetary Science 38(7,Suppl.): A115.

Russell, S. S. & 7 others (2004) The Meteoritical Bulletin, No. 88, 2004 July: Meteoritics & Planetary Science 39 (8, Suppl.): A215–A272. (Aug 2004).

Jambon A., Boudouma, O., Fonteilles, M., Le Guillou, C., Badia D. & Barrat, J. A. (2008) Petrology and mineralogy of the angrite Northwest Africa 1670. Meteoritics & Planetary Science 43:1783–1795.

Grady, M. M., Pratesi, G. & Moggi-Cecchi, V. (2015) Atlas of Meteorites. Cambridge University Press: Cambridge, United Kingdom. 373 pages.

External Links

http:www.lpi.usra.edu/meteor/metbull.php?code=17405 -NWA1670@MetBullDatabase
http://www.lpi.usra.edu/meteor/get_original_photo.php?recno=5631103 -NWA1670 photo
http://www.lpi.usra.edu/meteor/docs/mb88.pdf -MetBulletin#88
http://adsabs.harvard.edu/abs/2015E%26PSL.420...45S - Pb-Pb age

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