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Northwest Africa 4520
Basic information Name: Northwest Africa 4520
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 4520
Observed fall: No
Year found: 2000
Country: (Northwest Africa)
Mass:help 23.2 g
Meteoritical Bulletin:  MB 91  (2007)  Ureilite
Recommended:  Ureilite    [explanation]

This is 1 of 649 approved meteorites classified as Ureilite.   [show all]
Search for other: Achondrites, Ureilites
Comments: Approved 28 Mar 2007
Writeup from MB 91:

Northwest Africa 4520

Northwest Africa

Find: 2000

Achondrite (ureilite)

History: Purchased in Alnif in 2000.

Physical characteristics: A total mass of 23.2 g comprises a single stone that is a flat ellipsoid with the longest axis of 3.5 cm. The external color is dark brown, covered with moderately weathered fusion crust and some partly broken edges.

Petrography: (H. Takeda, Chiba; A. Yamaguchi, NIPR) The sample contains olivine only, observed in two polished thin sections made 2 cm apart. One section shows a typical ureilite texture with carbonaceous veins, in which Fe-metal, silica, and rare Na-K-rich aluminous silicate are present. Olivine ranges in size from ~1.5 × 0.9 mm to 0.6 × 0.3 mm. A large part of the other thin section consists of large olivine crystals up to 3.2 × 2.7 mm in size, with thin grain boundaries essentially without opaque materials. Small olivine grains (0.2 × 0.1 mm) with carbonaceous veins are present around the large olivine part. Olivine crystals have minor cracks, but shock effects are minor. Some grain boundaries are filled with Ca carbonate from interaction with the terrestrial environment.

Mineral compositions and geochemistry: Olivine (cores = Fo79–82, rims = Fo90). Oxygen isotopes: (M. Kusakabe, OkaU) δ17O = 3.32, δ18O = 8.07 (both ‰).

Classification: Achondrite (olivine-rich ureilite), minor weathering.

Type specimen: A total of 6 g and two thin sections are on deposit at NIPR. Fectay hold the main mass.

Plots: O isotopes:  
   and collections
NIPR: Antarctic Meteorite Research Center, National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan; Website (institutional address; updated 9 Dec 2013)
Chiba: Chiba Institute of Technology, Tsudanuma, Narashino, Chiba 275-0016, Japan (institutional address)
Fectay: Bruno Fectay and Carine Bidaut, La Memoire de la Terre SARL, 39800 Aumont, France; Website (private address)
OkaU: Institute for Study of the Earth's Interior, Okayama University, Misasa Tottori 682-0193, Japan (institutional address)
References: Published in Meteoritical Bulletin, no. 91, MAPS 42, 413-466 (2007)
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     This is 1 of 9429 approved meteorites from (Northwest Africa) (plus 1876 unapproved names)

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