![]() |
||
|
Northwest Africa 7257 | |||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Basic information | Name: Northwest Africa 7257 This is an OFFICIAL meteorite name. Abbreviation: NWA 7257 Observed fall: No Year found: 2012 Country: (Northwest Africa) Mass: ![]() | ||||||||||||||||||||||||||||
Classification history: |
This is 1 of 307 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite). [show all] Search for other: Martian meteorites | ||||||||||||||||||||||||||||
Comments: | Approved 29 May 2012 | ||||||||||||||||||||||||||||
Writeup![]() |
Writeup from MB 100:
Northwest Africa 7257 (NWA 7257) (Northwest Africa) Purchased: 2012 January Classification: Martian meteorite (Shergottite) History: Purchased by David Gregory in January 2012 from a Moroccan dealer at the Tucson Gem and Mineral Show. Physical characteristics: A single, fresh gray stone (180 g) partially coated by light-brown weathering products. The medium-grained interior is dominated by randomly oriented elongate prismatic pyroxene grains and ~25 vol.% sparkling maskelynite. Petrography: (A. Irving and S. Kuehner, UWS): Medium grained (pyroxene up to 6 mm long by 0.8 mm wide, plagioclase up to 2.5 mm long by 0.7 mm wide), with an intersertal texture. Prismatic grains of twinned and complexly-zoned clinopyroxene are accompanied by squat laths of maskelynite and accessory ilmenite, Cr-bearing ulvöspinel, pyrrhotite, chlorapatite, merrillite and rare fayalite. Regions of K-rich mesostasis are composed of microlites in partly devitrified brownish glass. Melt inclusions within pyroxene (surrounded by radial microcracks) are rich in K and P, and contain rare daughter crystals of hercynite. Geochemistry: Pigeonite (Fs29.8-34.3Wo15.3-13.3, Fe/Mn=29-33), subcalcic augite (Fs21.1-38.9Wo32.4-29.1, Fe/Mn=26-34), ferropigeonite rims (Fs44.6-54.1Wo11.4-18.0, Fe/Mn=33-37), plagioclase (An44.0-45.1Or2.2-2.7). Oxygen isotopes (R. Tanaka, OkaU): analyses of acid-washed subsamples by laser fluorination gave, respectively δ17O 2.83, 2.85; δ18O 4.82, 4.74; Δ17O 0.294, 0.352 per mil. Classification: Achondrite (Martian, shergottite). Specimens: 20.1 g of type material and one polished thin section are on deposit at UWS. The main mass is held by DGregory. | ||||||||||||||||||||||||||||
Data from: MB100 Table 1 Line 1700: |
|
||||||||||||||||||||||||||||
Plots: | O isotopes: | ||||||||||||||||||||||||||||
Institutions and collections |
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012) DGregory: David Gregory, 230 First Avenue, Suite 108, St. Thomas, Ontario N5R 4P5, Canada (private address) OkaU: Institute for Study of the Earth's Interior, Okayama University, Misasa Tottori 682-0193, Japan (institutional address) |
||||||||||||||||||||||||||||
Catalogs: |
| ||||||||||||||||||||||||||||
References: | Published in Meteoritical Bulletin, no. 100, MAPS 49, E1-E101 (2014)
| ||||||||||||||||||||||||||||
Geography: |
Statistics: This is 1 of 9429 approved meteorites from (Northwest Africa) (plus 1876 unapproved names) |