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Northwest Africa 2646
Basic information Name: Northwest Africa 2646
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 2646
Observed fall: No
Year found: 2004
Country: (Northwest Africa)
Mass:help 9.3 g
Classification
  history:
Meteoritical Bulletin:  MB 90  (2006)  Martian (plagioclase-olivine clinopyroxenite)
Recommended:  Martian    [explanation]

This is 1 of 2 approved meteorites classified as Martian.   [show all]
Search for other: Martian meteorites
Comments: Approved 25 Jun 2005
Writeuphelp
Writeup from MB 90:

Northwest Africa 2646

Algeria or Morocco

Find: December 2004

Achondrite (Martian, plagioclase-olivine clinopyroxenite)

History: A 9.3 g, broken stone (allegedly part of a larger specimen found at an unknown site in Algeria or Morocco) was purchased from a Moroccan dealer in December 2004 for N. Oakes.

Petrography and Geochemistry: (T. Bunch and J. Wittke, NAU; A. Irving and S. Kuehner, UWS) The specimen is relatively coarse-grained and has an overall gray color, but grain surfaces have a thin whitish coating. It is modally heterogeneous and is composed of ~40.7% pigeonite, ~24.3% augite, ~21.6% olivine, and ~11.4% maskelynite, with 2% chromite, ilmenite, merrillite, and pyrrhotite. Euhedral to subhedral chromite (Cr/(Cr+Al) = 0.869, Mg/(Mg+Fe) = 0.12) and augite (Fs19–23Wo26–36; FeO/MnO = 22–27; Cr2O3 = 0.6, Al2O3 = 2.2 [both wt%]) appear to have crystallized first, followed by subhedral to anhedral olivine (Fa38–44; FeO/MnO = 35–56). These are poikilitically enclosed in large oikocrysts of pigeonite (Fs24.4Wo5.7 zoned to Fs34.4Wo12.1; FeO/MnO = 26–32); augite and olivine chadacrysts tend to be clustered. Laths of plagioclase (now maskelynite, An58.4–60.7Or0.9), some in clusters, occur interstitially to pigeonite grains. All maskelynite grains are rimmed by zones up to 40 µm in width consisting of a mixture of fine grained calcite, hydrous Al-rich silicate (possibly kaolinite), and very minor calcium chloride, which appear to be replacing the primary feldspar. This specimen has affinities to the six recognized “lherzolitic shergottites,” but differs from them in having a higher abundance of plagioclase and more ferroan mafic mineral compositions.

Classification: Achondrite (Martian, plagioclase-olivine clinopyroxenite); minimal weathering.

Specimens: A 3.4 g type specimen and one polished thin section are on deposit at NAU. One polished mount is on deposit at UWS. N. Oakes holds the main mass.

Data from:
  MB90
  Table 2
  Line 37:
Place of purchase:Morocco
Date:Dec 2004
Mass (g):9.3
Pieces:1
Class:Martian
Type spec mass (g):3.4
Institutions
   and collections
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
Oakes: Nelson Oakes, Route 1, House 50C, Uniondale, PA 18470, United States; Website (private address)
Catalogs:
References: Published in Meteoritical Bulletin, no. 90, MAPS 41, 1383-1418 (2006)
Find references in NASA ADS:
Find references in Google Scholar:
Photos:
CreditPhotos
Photos from the Encyclopedia of Meteorites:
Nelson Oakes   
Norbert Classen   
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 6846 approved meteorites from (Northwest Africa) (plus 2038 unapproved names)

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