Official Meteoritical Bulletin entry for Northwest Africa 4468:
Northwest Africa 4468 Northwest Africa Find: Summber 2006 Achondrite (Martian, basaltic shergottite)
History: Found in the western part of the Sahara in summer 2006 and purchased in Laâyoune by G. Hupé in July 2006. Physical characteristics: A single 675 g ellipsoidal stone, mostly coated by shiny black fusion crust, and broken at one end revealing the pale yellow-green interior. Petrography: (A. Irving and S. Kuehner, UWS) Large ovoid pyroxene oikocrysts (2–10 mm across) enclosing chadacrysts of Ti-poor chromite and olivine are set in an interstitial matrix of 35% olivine, 30% clinopyroxene, 25% maskelynite (all vol%), Ti-chromite, ilmenite, merrillite, Cl-apatite (as prisms up to 0.8 mm long), and pyrrhotite. Inclusions (up to 300 µm across) surrounded by radial shock relaxation fractures occur within matrix olivine grains; some are quenched melt inclusions and others consist mainly of maskelynite. The specimen is cross-cut by sporadic, thin, dark, glassy shock veins (Irving et al. 2007). Mineral compositions and geochemistry: Pyroxene oikocrysts are zoned from orthopyroxene cores (Fs24.5Wo4.4; FeO/MnO = 35.4) with mantles of pigeonite (Fs26.3Wo6.3; FeO/MnO = 29.4) to augite rims (Fs17.9Wo33.6; FeO/MnO = 24.9). Olivine chadacrysts (as magnesian as Fa28.8) typically become progressively more ferroan from pyroxene core to rim (up to Fa39.9). Matrix olivine (Fa40.7; FeO/MnO = 50.2), matrix clinopyroxene (Fs31.3Wo8.1, Fs19.6Wo31.3), matrix maskelynite (An38.7–54Or3.9–2.3); maskelynite in inclusions within olivine is inhomogeneous and K-Na-rich (Or52.6Ab40.7An6.7). Classification: Achondrite (Martian, basaltic shergottite). Type specimen: A total of 20.2 g and one large 3.8 × 2.8 cm thin section are on deposit at UWS. G. Hupé holds the main mass.
Scientific abstracts and news regarding NWA 4468:
L. E Borg, A. M. Gaffney, and D. DePaolo
(2008) PRELIMINARY AGE OF MARTIAN METEORITE NORTHWEST AFRICA 4468 AND ITS
RELATIONSHIP TO THE OTHER INCOMPATIBLE-ELEMENT-ENRICHED SHERGOTTITES.
Lunar and Planetary Science XXXIX. (abs. 1851). http://www.lpi.usra.edu/meetings/lpsc2008/pdf/1851.pdf
J. G. Spray and S. Boonsue.
(2011) SHOCK-INDUCED MELT POCKET FORMATION IN NWA 4468:
EVIDENCE FOR PHASE TRANSFORATION-INDUCED IMPLOSION.
Planetary and Space Science Centre. http://www.lpi.usra.edu/meetings/metsoc2011/pdf/5201.pdf
A. J. Irving, S. M. Kuehner, R. L. Korotev and G. M. Hupé
(2007) PETROLOGY AND BULK COMPOSITION OF PRIMITIVE ENRICHED OLIVINE
BASALTIC SHERGOTTITE NORTHWEST AFRICA 4468. (abs. 1526). http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1526.pdf
Complete polished slice of NWA 4468.
Thin Section image in partially Cross-Polarized Light (pyroxene and olivine colors, maskelynite gray, glass veins and chromite black).
Description coming Soon!
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