Meteoritical Bulletin: Entry for Northwest Africa 773

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Northwest Africa 773

Basic information

Name: Northwest Africa 773
This is an OFFICIAL meteorite name.
Abbreviation: NWA 773
Observed fall: No
Year found: 2000
Country: Western Sahara
Mass: 633 g

Classification
history:

NHM Catalogue:	5th Edition	(2000)	Lunar (ol norite)
Meteoritical Bulletin:	MB 85	(2001)	Lunar (cumulate olivine norite with regolith breccia)
MetBase:	v. 7.1	(2006)	Lunar (norite)
Recommended:			Lunar (gabbro) [explanation]

This is 1 of 13 approved meteorites classified as Lunar (gabbro). [show all]
Search for other: Lunar meteorites

Comments:

Revised 12 Feb 2023: updated classification

Writeup

help

Writeup from MB 85:

Northwest Africa 773

Western Sahara

Found 2000 September

Lunar Meteorite (cumulate olivine norite with regolith breccia)

Three stones of 359, 224 and 50 g, totaling 633 g were sold to Marvin Killgore (SWML) by nomads who showed him the place of find on a flat dry desert plain near Dchira, Western Sahara. Mineralogy and classification (T. Fagan, UHaw; M. Killgore, SWML; J. Wittke and T. Bunch, NAU): consists of two distinct lithologies, cumulate rock and regolith breccia; shock stage, S2; weathering grade, W1. Cumulate portion: modes (vol%) are olivine = 54.7, pigeonite = 24.2, augite = 5, feldspar (including minor K-feldspar) = 15.6, opaques (troilite, chromite, Fe-metal, ilmenite) = 0.5; olivine, Fa_28–34, mean Fa₃₁, FeO/MnO = 99 ± 11 g/g; pigeonite, En₆₄Wo₁₁, FeO/MnO = 53 ± 6 g/g; augite, En₄₉Wo₃₆, FeO/MnO = 46 ± 6 g/g; plagioclase, An_88–91; Ba-rich K-feldspar, An₃Ab₄Or₉₃ with average BaO = 2.2 wt%. Breccia portion: contains fragments of cumulate portion as well as silica glass, hedenbergitic pyroxene, volcanic rocks, and unusual lithic clasts with fayalite + Ba-rich K-feldspar + silica + plagioclase; olivine and pyroxene in the breccia have a slightly wider compositional range towards lower Mg/(Mg + Fe) than in the cumulate portion of the rock. Chemical composition (D. Mittlefehldt, JSC): KREEP-rich with strong negative Eu-anomaly. Noble gases (O. Eugster, Physikalisches Institut, Bern): high solar wind component, ₄He/₂₀Ne = 9, indicative of regolith material. Specimens: type specimen, 15 g, NHM; main mass SWML.

Writeup from MB 112:

NWA 773: classification update

From A. Irving, UWS: Based on Fagan et al. (2003) and many subsequent pairings (see Crosslinks section on this page), NWA 773 should be classified as a gabbro instead of a norite.

Bibliography:

Fagan T. J., Taylor G. J., Keil K., Hicks T. L., Killgore M., Bunch T. E., Wittke J. H., Mittlefehldt D. W., Clayton R. N., Mayeda T. K., Eugster O., Lorenzetti S. and Norman M. D. (2003) Northwest Africa 773: Lunar origin and iron-enrichment trend. Meteoritics & Planetary Science 38, 529–554. (link)

Data from:
  MB85
  Table 4
  Line 213:

Origin or pseudonym:	Dchira, W. Sah.
Date:	6 Oct 2000
Latitude:	~26°46'N
Longitude:	~12°49'W
Mass (g):	633
Pieces:	3
Class:	Lunar

Institutions
and collections

JSC: Mailcode XI, 2101 NASA Parkway, NASA Johnson Space Center, Houston, TX 77058, United States; Website (institutional address; updated 28 Jul 2022)
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
NHM: Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom; Website (institutional address; updated 9 Dec 2011)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
Bern: University of Bern, University of Bern, Hochschulstrasse 4, CH-3012 Bern, Switzerland (institutional address)
Killgore: Marvin and Kitty Killgore, Southwest Meteorite Laboratory, P.O. Box 95, Payson, AZ 85547, United States; Website (private address)
SWML: Marvin and Kitty Killgore, Southwest Meteorite Laboratory, P.O. Box 95, Payson, AZ 85547, United States; Website (private address)
UHaw: Hawai'i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, United States (institutional address; updated 25 Oct 2011)

Catalogs:

Search for this meteorite in the Natural History Museum collection (U.K.):

References:

Published in Meteoritical Bulletin, no. 85, MAPS 36, A293-A322 (2001)
Published in Meteoritical Bulletin, no. 112, in preparation (2023)

Find references in NASA ADS:
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Photos:

Credit	Photos
Photos from the Encyclopedia of Meteorites:
Norbert Classen
Randy Korotev

Geography:

Western Sahara

Western Sahara

Coordinates:
Catalogue of Meteorites:	(26° 46'N, 12° 49'W)
Recommended::	(26° 46'N, 12° 49'W)

Statistics:
This is 1 of 117 approved meteorites from Saguia el Hamra, Western Sahara (plus 1 unapproved name)
This is 1 of 280 approved meteorites from Western Sahara (plus 20 unapproved names)

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Revision
history:

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