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Northwest Africa 2975
Basic information Name: Northwest Africa 2975
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 2975
Observed fall: No
Year found: 2005
Country: Algeria
Mass:help 70.1 g
Meteoritical Bulletin:  MB 90  (2006)  Martian (basaltic shergottite)
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 329 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 16 Jan 2006
Revised 3 Feb 2006: Revised writeup
Writeup from MB 90:

Northwest Africa 2975


Find: 2005

Achondrite (Martian, basalticshergottite)

History: A minimally weathered fully encrusted wholestone of 70.1 g was purchased in Erfoud, Morocco, by M. Farmer in November2005.

Petrography: (T. Bunch and J. Wittke, NAU; A.Irving, UWS) A medium-grained (<3.1 mm greatest dimension) basalticshergottite that consists of ~57.3 vol% augite and pigeonite pyroxenes, and38.3 vol% plagioclase (present as shock-formed maskelynite and glasses) withminor opaques (2.7 vol%) and phosphates (1.7 vol%) arranged in a weaklyfoliated subophitic to granular texture. Accessory phases include ulvöspinel,ilmenite, chlorapatite, merrillite, pyrrhotite, Si-Al-Na-K-rich glasses, andbaddeleyite. Vesicular black glass veins (<3 mm in width) and pockets (up to6 mm) are prominent.

Geochemistry: Pigeonite (Fs35.2–57.6Wo12.6–16.5;FeO/MnO = 28–38) and augite (Fs27.2–41.5Wo30.8–35.2) showmottled compositional zoning. Fe-rich margins of pigeonite contain very thin(0.2–0.5 µm) orthopyroxene exsolution lamellae. Maskelynite is compositionallyhomogeneous An55Or1.8 in contrast to mesostasismaskelynite (An48–60Or9.2) and glasses. Melt inclusions(15–60 µm, longest dimension) in ulvöspinel have rims of Fe-rich pigeonite (Fs73.5Wo5.8),merrillite, and pyrrhotite; cores are Si-Al-K-Na-rich glass. Bulk composition:Calculated average bulk composition based on analyzed phases and their modes ofthree melt inclusions is: SiO2 = 70.2, Al2O3 =8.5, TiO2 = 0.8, FeO = 2.1, MnO = 0.2, MgO = 2.35, CaO = 3.5, Na2O= 0.95, K2O = 2. 1, and P2O5 = 2.8 (all wt%)with trace amounts of NiO, CoO, and S. One melt inclusion contains onlyfayalite (Fa84) mantled around a core of glass (K2O =6.4, SiO2 = 78; both wt%).

Classification: Achondrite (Martian basalticshergottite); moderate to high shock, minimal weathering.

Specimens: A 20.2 g type specimen and one thinsection are on deposit at NAU*. An anonymous owner holds the main mass.

Data from:
  Table 0
  Line 0:
Type spec location:NAU* type specimen now at UWB. 20.2 g at UWB; remainder with owner.
Comments:Work name 826, thin section RTO2
Data from:
  Table 2
  Line 188:
Place of purchase:Algeria
Mass (g):70.1
Type spec mass (g):20.2
   and collections
NAU*: Collection discontinued. Specimens redistributed as shown in individual meteorite records, United States (institutional address; updated 24 Jun 2024)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
UWB: University of Washington, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023)
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States (institutional address; updated 12 Apr 2012)
References: Published in Meteoritical Bulletin, no. 90, MAPS 41, 1383-1418 (2006)
Published in Meteoritical Bulletin, no. 113, in preparation (2024)
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     This is 1 of 1376 approved meteorites from Algeria (plus 31 unapproved names) (plus 4 impact craters)

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