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Northwest Africa 4286 | |||||||||||||||||||||||||||
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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: ![]() | ||||||||||||||||||||||||||
Classification history: |
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![]() |
Writeup from MB 91:
Northwest Africa 4286 Algeria 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: MB91 Table 2 Line 278: |
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Institutions 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) |
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Catalogs: |
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References: | Published in Meteoritical Bulletin, no. 91, MAPS 42, 413-466 (2007)
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Geography: |
Statistics: This is 1 of 8904 approved meteorites from (Northwest Africa) (plus 1871 unapproved names) |