Meteoritical Bulletin: Entry for Northwest Africa 4284

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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: 137 g

Classification
history:

Meteoritical Bulletin:	MB 95	(2009)	Achondrite (ungrouped)
Recommended:			Achondrite-ung [explanation]

This is 1 of 151 approved meteorites classified as Achondrite-ung. [show all]
Search for other: Achondrites, Ungrouped achondrites

Comments:

Approved 23 Dec 2008

Writeup

help

Writeup from MB 95:

Northwest Africa 4284

Algeria

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, Fs_24.5Wo_3.5, FeO/MnO = 28–30; olivine, Fa_24.6, FeO/MnO = 46–54; plagioclase. An₁₁Or_5.3; Ca pyroxene, Fs_8.2Wo_44.2; 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:
  MB95
  Table 2
  Line 45:

Place of purchase:	Algeria
Date:	2005
Mass (g):	137
Pieces:	1
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:

Institutions
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)

Catalogs:

References:

Published in Meteoritical Bulletin, no. 95, MAPS 44, 429-462 (2009)

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Geography:

Coordinates:

Unknown.

Statistics:
This is 1 of 9699 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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Revision
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