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Northwest Africa 4284
Basic information Name: Northwest Africa 4284
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 4284
Observed fall: No
Year found: 2005
Country: (Northwest Africa)
Mass:help 137 g
Meteoritical Bulletin:  MB 95  (2009)  Achondrite (ungrouped)
Recommended:  Achondrite-ung    [explanation]

This is 1 of 99 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 23 Dec 2008
Writeup from MB 95:

Northwest Africa 4284


Find: 2005

Achondrite (ungrouped)

History: A 137 g partial stone with partial crust was purchased in Erfoud, Morocco in 2005.

Petrography (T. Bunch and J. Wittke, NAU): Igneous textures include hypidimorphic-granular, ophitic, and poikilitic (orthopyroxene oikocrysts enclose olivine). NWA 4284 is composed of mm to submillimeter-sized grains of (in order of abundance) orthopyroxene, olivine, plagioclase, Ca pyroxene, FeS, and chromite. Taenite metal occurs in rare, isolated clusters of coarser-grained orthopyroxene-olivineplagioclase- taenite.

Geochemistry: Orthopyroxene, Fs24.5Wo3.5, FeO/MnO = 28–30; olivine, Fa24.6, FeO/MnO = 46–54; plagioclase. An11Or5.3; Ca pyroxene, Fs8.2Wo44.2; chromite, Cr# = 0.88; and taenite, Ni = 21.5 (no kamacite was found).

Oxygen isotopes (D. Rumble, CIW): a cleaned and metal-free sample was analyzed by laser fluorination. Replicate analyses are, respectively, δ17O = 3.253, 3.227‰; δ18O = 4.195. 4.247‰; Δ17O = 1.046, 0.993‰.

Classification: Achondrite (ungrouped). Mineral compositions and oxygen isotopes indicate that this stone has an L chondrite heritage, but the lack of chondrules and obvious igneous textures, indicate a later melt origin.

Specimens: type example, 21 g and one thin section, NAU; main mass holder is Edwin Thompson.

Data from:
  Table 2
  Line 45:
Place of purchase:Algeria
Mass (g):137
Class:Achondrite (ungrouped)
Fayalite (mol%):24.6
Ferrosilite (mol%):24.5
Wollastonite (mol%):3.5
Classifier:T. Bunch and J. Wittke, NAU
Type spec mass (g):21
Type spec location:NAU
Main mass:Thompson
Plots: O isotopes:  
   and collections
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
CIW: Carnegie Insitution Washington, Geophysical Laboratory, 5251 Broad Branch Rd., NW, Washington DC 20015, United States (institutional address)
Thompson: Edwin Thompson, 5150 Dawn St., Lake Oswego, OR 97035, United States (private address)
References: Published in Meteoritical Bulletin, no. 95, MAPS 44, 429-462 (2009)
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     This is 1 of 7374 approved meteorites from (Northwest Africa) (plus 1957 unapproved names)

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