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Northwest Africa 4286
Basic information Name: Northwest Africa 4286
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 4286
Observed fall: No
Year found: 2005
Country: (Northwest Africa)
Mass:help 71 g
Meteoritical Bulletin:  MB 91  (2007)  L-melt rock
Recommended:  L-melt rock    [explanation]

This is 1 of 46 approved meteorites classified as L-melt rock.   [show all]
Search for other: L chondrites, L chondrites (type 4-7), Melted chondrites, Ordinary chondrites, and Ordinary chondrites (type 4-7)
Comments: Approved 28 Mar 2007
Writeup from MB 91:

Northwest Africa 4286


Find: 2005

Ordinary chondrite (L melt rock)

History: A stone was found in southern Algeria in 2005 and sold in Erfoud in November 2005.

Physical characteristics: A 71 g partial stone with no residual crust is reddish brown in color with raised, small (<1 mm) bumps of lightly oxidized metal and sulfide.

Petrography: (T. Bunch and J. Wittke, NAU) Very dark interior that is mostly shock-melted with three distinct grain sizes: 1) shocked and unmelted olivine and orthopyroxene fragments (<0.3 mm), 2) melt-crystallized olivine > orthopyroxene > plagioclase > augite (<0.05 mm), and 3) very fine grained matrix (<0.01 mm) that consists of olivine, orthopyroxene, SiO2-rich feldspathic glass, and tiny metal melt spheres. Large oblate to rounded melt-formed taenite is commonly mantled by sulfide and is <3 mm in size. No metal-sulfide eutectic structures were noted. There is a strong directional flow orientation of the metal-sulfide complexes. No residual kamacite and taenite is partially oxidized.

Mineral compositions and geochemistry: Olivine megacrysts (Fa23.6; FeO/MnO = 50), midsize olivine (Fa20.2–27.6; FeO/MnO = 44–54). Orthopyroxene megacrysts (Fs19.6Wo2.6; FeO/MnO = 33), augite (Fs15.6Wo30.4). Taenite (Ni = 15.2 wt%) and chromite fragments (Cr/[Cr+Al] = 0.84).

Classification: Ordinary chondrite (L melt rock); S5, moderate weathering. This sample is similar to NWA 2085, but lacks metal-sulfide eutectic structures.

Type specimen: A total of 14.6 g and one thin section are on deposit at NAU. Thompson is holder of the main mass.

Data from:
  Table 2
  Line 278:
Place of purchase:Erfoud, Morocco
Mass (g):71
Class:OC (L melt)
Shock stage:S5
Weathering grade:moderate
Fayalite (mol%):23.6
Ferrosilite (mol%):19.6
Classifier:T. Bunch and J. Wittke, NAU
Type spec mass (g):14.6
Type spec location:NAU
Main mass:Thompson
   and collections
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
Thompson: Edwin Thompson, 5150 Dawn St., Lake Oswego, OR 97035, United States (private address)
References: Published in Meteoritical Bulletin, no. 91, MAPS 42, 413-466 (2007)
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     This is 1 of 8904 approved meteorites from (Northwest Africa) (plus 1871 unapproved names)

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