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Northwest Africa 11071
Basic information Name: Northwest Africa 11071
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11071
Observed fall: No
Year found: 2016
Country: (Northwest Africa)
Mass:help 23.8 g
Classification
  history:
Meteoritical Bulletin:  MB 106  (2018)  Aubrite
Recommended:  EH-melt rock    [explanation]

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 3 Mar 2017
Revised 11 May 2019: Reclassification
Writeuphelp
Writeup from MB 106:

Northwest Africa 11071 (NWA 11071)

(Northwest Africa)

Purchased: 2016 Jul

Classification: Enstatite achondrite (Aubrite)

History: A batch of small brownish stones was purchased by Roger Jones in July 2016 from a dealer in Guelmim, Morocco.

Petrography: (A. Irving and S. Kuehner, UWS) Aggregate of predominantly enstatite (to 1.6 mm) with accessory albite, oligoclase, silica polymorph, daubreelite, altered kamacite, schreibersite and perryite. Grain boundaries are stained with iron hydroxides from alteration of primary metal.

Geochemistry: Enstatite (Fs0.0-0.1Wo0.5-0.7, N = 2), albite (Ab92.4An1.6Or6.0), oligoclase (An16.0Or2.5), metal (Si 1.6-3.3 wt.%, Ni 2.0-3.6 wt.%, Co 0.4 wt.%).

Classification: Aubrite.

Specimens: 4.8 g including one polished mount at UWB; remainder with Mr. R. Jones.


Writeup from MB 108:
NWA 11071: 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:
  • Udry A., Wilbur Z.E., Rahib R.R., McCubbin F.M., Vander Kaaden K.E., McCoy T.J., Ziegler K., Gross J., DeFelice C., Combs L., and Turrin B.D. (2019) Reclassification of four aubrites as enstatite chondrite impact melts: Potential geochemical analogs for Mercury. Meteorit. Planet. Sci. 54, 785-810 (link)
Data from:
  MB106
  Table 0
  Line 0:
Place of purchase:Guelmim
Date:P 2016 Jul
Mass (g):23.8
Pieces:several
Class:Aubrite
Shock stage:low
Weathering grade:low
Ferrosilite (mol%):0.0-0.1
Wollastonite (mol%):0.5-0.7
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):4.8
Type spec location:UWB
Main mass:R. Jones
Comments:RBJ16-5; submitted by A. Irving
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)
Catalogs:
References: Published in Gattacceca J., Bouvier A., Grossman J., Metzler K., and Uehara M. (2019) Meteoritical Bulletin, no. 106. Meteorit. Planet. Sci. 54 in press.
Published in Meteoritical Bulletin, no. 108, in preparation (2019)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 6900 approved meteorites from (Northwest Africa) (plus 2027 unapproved names)

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