|Northwest Africa 2828|
|Basic information||Name: Northwest Africa 2828|
This is an OFFICIAL meteorite name.
Abbreviation: NWA 2828
Observed fall: No
Year found: 2005
Country: (Northwest Africa)
Mass: 8.67 kg
This is 1 of 63 approved meteorites classified as Aubrite. [show all]
Search for other: Achondrites, Enstatite-rich meteorites, Aubrites, and Enstatite achondrites
|Comments:||Approved 11 Jun 2006|
Writeup from MB 91:
Northwest Africa 2828
Mauritania or Algeria
Find: December 2005
History: Purchased in December 2005 by Greg Hupé from a Moroccan dealer in Tagounite.
Physical characteristics: Thirty-six pale gray to whitish stones lacking fusion crust with a total weight of 8672 g. Several stones have exterior light orange staining, and two stones contain one or two dark brown cross-cutting veins (1–2 mm wide) of magnetic, fine-grained iron oxide and hydroxide minerals.
Petrography: (A. Irving and S. Kuehner, UWS) Monomict microbreccia, which is mostly fairly uniform but contains sporadic small, rounded clasts (up to 4 mm across). Relatively fine but variable grain size (0.3–1.5 mm), and composed predominantly of bladed grains of essentially pure enstatite (exhibiting lamellar twinning) with ~15 vol% oligoclase, accessory altered troilite with fresh, subparallel exsolution blades of daubreelite, and sporadic rounded to ellipsoidal grains of graphite (up to 1.2 mm across). Small (<0.2 mm) lobate cavities partly filled with fine-grained calcite, silica, and an Fe-bearing mineral are present in the interior of even the freshest stones, and may represent former oldhamite grains. Small grains found as inclusions within enstatite are fresh Ti-free troilite, pure Mn-alabandite, daubreelite, fresh oldhamite (some Mn-bearing), schreibersite, and very rare specks of kamacite and taenite. Minor barite and calcite are present, probably the products of terrestrial weathering.
Mineral compositions and geochemistry: Pyroxene (En99.8Wo1.4; Al2O3 = 0.21 wt%), plagioclase (An13.5–15.3 Or3.0–4.4). Oxygen isotopes: (D. Rumble, CIW) Analyses of two whole-rock fragments by laser fluorination gave, respectively, δ18O = 5.50, 5.56; δ17O = 2.89, 2.90; Δ17O = +0.001, −0.026 (all ‰).
Classification: Achondrite (aubrite). Weathering effects in most stones are limited to alteration of interior troilite and probable oldhamite, and minor orange staining and dissolution on exterior surfaces. This aubrite appears to be completely different in appearance and texture from more metal-rich enstatite-rich meteorites NWA 002, NWA 1067, NWA 2736, and NWA 2965.
Type specimen: A total of 20.1 g and two polished thin sections are on deposit at UWS. GHupé; holds the main mass.
NAU: Geology, Bldg 12
Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
CIW: Carnegie Insitution Washington, Geophysical Laboratory, 5251 Broad Branch Rd., NW, Washington DC 20015, United States (institutional address)
GHupé: Gregory M. Hupé, 9003 Placid Lakes Blvd., Lake Placid, FL 33852, United States; Website (private address)
Reed: Blaine Reed, P.O. Box 1141, Delta, CO 81416, United States; Website (private address)
|References:||Published in Meteoritical Bulletin, no. 91, MAPS 42, 413-466 (2007)|
This is 1 of 3542 approved meteorites from (Northwest Africa) (plus 2642 unapproved names)
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