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Northwest Africa 7258
Basic information Name: Northwest Africa 7258
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7258
Observed fall: No
Year found: 2011
Country: Morocco
Mass:help 310 g
Meteoritical Bulletin:  MB 100  (2012)  Martian (shergottite) 
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 326 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 25 May 2012
Writeup from MB 100:

Northwest Africa 7258 (NWA 7258)


Found: 2011

Classification: Martian meteorite (Shergottite)

History: Purchased through Hmanis (Ali and Simon).

Physical characteristics: Interior is pale green-tinged grey. A paper-thin patch of rusty discoloration is visible beneath the fusion crust. Shock classification S5, based on complete maskelynitization, and on mosaic extinction in pyroxenes.

Petrography: Texture and mode are very Shergotty-like. Pyroxene (75 vol%) laths are up to 4 × 0.5 mm, mildly aligned; zoning shows Shergotty-like Wo-bimodality, starting near En59Wo11 and En46Wo34. Plagioclase/maskelynite (20 vol%) is Ab50Or2.2 to Ab52Or7 (59 analyses).

Geochemistry: Bulk-rock INAA and fused-bead EPMA results from two 0.5-g chips include Ga/Al = 0.00051, Al2O3 = 5.2 wt%. REE are ~15 × CI chondrites, except REE near Tb ~20 × CI. Siderophile contents are at typical shergottite levels (e.g., 70 µg/g Ni).

Classification: Bulk O-isotopic composition is martian (B-G. Choi and I. Ahn, CO2 laser-fluorination at KOPRI): δ18O = 4.716, δ17O = 2.804, and Δ17O = +0.33 (all per mil). Among NWA shergottites, it features a unique combination of mode, texture, and Al-poor, REE-rich bulk composition.

Specimens: The UCLA material is derived from a single sawn corner of the meteorite.

Data from:
  Table 1
  Line 1701:
Origin or pseudonym:Goulmin
Place of purchase:Morocco
Mass (g):310
Class:Martian (shergottite)
Shock stage:high
Weathering grade:minimal
Ferrosilite (mol%):diverse
Wollastonite (mol%):bimodal
Classifier:P. Warren, UCLA
Type spec mass (g):20.8
Type spec location:UCLA
Main mass:E. Thompson
Comments:Submitted by Paul Warren
Plots: O isotopes:  
   and collections
UCLA: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, United States (institutional address; updated 17 Oct 2011)
KOPRI: Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon, Korea, 406-840, South Korea; Website (institutional address; updated 20 Dec 2014)
Thompson: Edwin Thompson, 5150 Dawn St., Lake Oswego, OR 97035, United States (private address)
References: Published in Meteoritical Bulletin, no. 100, MAPS 49, E1-E101 (2014)
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     This is 1 of 2094 approved meteorites from Morocco (plus 32 unapproved names) (plus 1 impact crater)

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