|Northwest Africa 7533|
|Basic information||Name: Northwest Africa 7533|
This is an OFFICIAL meteorite name.
Abbreviation: NWA 7533
Observed fall: No
Year found: 2012
Country: (Northwest Africa)
Mass: 84 g
This is 1 of 63 approved meteorites classified as Achondrite-ung. [show all]
Search for other: Achondrites, Ungrouped achondrites
|Comments:||Approved 11 Dec 2012|
Writeup from MB 101:
Northwest Africa 7533 (NWA 7533)
Purchased: June 2012
Classification: Ungrouped achondrite
Petrography: (R. Hewins, MNHNP) Breccia, largest objects (~1 cm) are flattened, oval or curved fine-grained melt bodies containing crystal fragments, often with melt mantles or coatings. The melt rocks have a fine-grained subophitic to fasciculate texture (grain size 2-5 μm) and are characterized by clots with central oxides (magnetite, chromite or ilmenite) in a mass of pyroxene dendrites embedded in aureoles of plagioclase. Clasts (to ~2 mm) are dominantly crystal clasts of pyroxenes and feldspars, with magnetite and chlorapatite, small coarse-grained noritic-monzonitic fragments (>1 mm grains) made up of several of these phases, microbasalts with subophitic to granoblastic textures (grain size 1-5 μm) and melt spheres (~100 μm to >3 mm). Pyroxenes include orthopyroxene, inverted pigeonite, pigeonite (in microbasalts), and augite. Feldspars include plagioclase, anorthoclase, orthoclase and perthite. Inverted pigeonite contains 10 μm exsolution lamellae. Olivine occurs as dendrites in one melt sphere. The fine-grained interclast matrix is difficult to discern because clasts have sizes down to ~5 μm; it consists of anhedral μm-sized plagioclase with sub-μm pyroxene surrounding and embedded in it plus magnetite, often symplectitic or lacy. Rare pyrite is replaced by magnetite and hydrated or oxidized magnetite.
Geochemistry: (R. Hewins and B. Zanda, MNHNP) Orthopyroxene from Fs21.9Wo1.9 to Fs49.4Wo5.0, FeO/MnO = 34.6 (n=29), and augite from Fs15.4Wo40.5 to Fs30.5Wo39.5. Inverted pigeonite from Fs40Wo2 with Fs21Wo44 lamellae to Fs48Wo6 with Fs21Wo44 lamellae. Plagioclase An41±8Ab56±7Or3±1 (n=55), perthite An3±2Ab22±7Or74±9 and An4±2Ab89±3Or7±2, anorthoclase An5±2Ab83±13Or12±11, orthoclase An2±0Ab21±1Or77±1, chromite with up to 52.4 wt% Cr2O3, magnetite and ilmenite with up to 5.7 wt% MgO, apatite with 1.8 to 5.4 wt% Cl. Maghemite identified by XRD. Oxygen isotopes: (J. Gattacceca, CEREGE) IR-laser fluorination/mass spectrometry gave δ18O=5.92, δ17O=3.65, Δ17O= 0.57 (all per mil).
Classification: Achondrite ungrouped. Breccia, probably paired with NWA 7034. The oxygen isotopic values are identical to those of that ungrouped achondrite breccia, and the range of mineral compositions of the two meteorites are very similar. Some of the pyroxene compositions are also very close to those of ALH 84001.
Specimens: 17 g, MNHNP, main mass with finder
Avenue Philibert, Europole de l'Arbois
13545 Aix-en-Provence Cedex 4
France, France (institutional address; updated 17 Nov 2011)
MNHNP: Museum National d'Histoire Naturelle, 61 Rue Buffon, LMCM-CP52, 75005 Paris, France, France; Website (institutional address; updated 8 Nov 2012)
Labenne: 23, rue de Esperance, 75013 Paris, France; Website (private address; updated 29 Aug 2012)
|References:||Published in Meteoritical Bulletin, no. 101, MAPS 47, in preparation (2013)|
This is 1 of 4156 approved meteorites from (Northwest Africa) (plus 2438 unapproved names)
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