NWA 5480 - Olivine Diogenite
Thin Section image
Name: Northwest Africa 5480
Found: July 2008
Location: Mali
TKW: 4912 grams
Classification: Achondrite (olivine diogenite)
"Scientists are very excited about NWA 5480 because it exhibits unique textural characteristics not previously found in any other known meteorites! They say the material must have been heated to a point where it became "plasticized" and mixed, presumably in the deep interior (mantle) of the NWA 5480 parent body (presumably Vesta-related). By analogy with deformed olivine-orthopyroxene-rich samples of the Earth's mantle (known as harzburgites), it appears likely that temperatures were high enough that NWA 5480 represents a solid residue after partial melting to produce molten magma, which presumably ascended towards the surface of the parent body. The "swirl" texture that can be seen on the interior and exterior graphically displays the flowing and mixing of the olivine and orthopyroxene grains, with intermingled chromite crystals."
History:
Found near Arg Shash, Mali in July 2008 and purchased by Greg Hupé in October/November 2008 from Moroccan dealers in Erfoud and Tagounite.
Physical characteristics:
Seven very fresh, dense, dark brown to pale green mottled stones lacking obvious fusion crust with a total weight of 4912 g. Sporadic large, black chromite grains (up to 1.5 cm across) are visible on the exterior of some stones.
Petrography:
(A. Irving and S. Kuehner, UWS) Medium to coarse grained, and composed mainly of olivine (57 vol.%) and orthopyroxene (42 vol.%), with minor chromite (1 vol.%) and accessory troilite and Ni-free metal. Plagioclase is absent. The distribution of olivine and orthopyroxene is very heterogeneous, with regions composed of up to 90% of either mineral, some in irregular, schlieren-like polygranular arrays. Olivine-rich regions (brown) are composed of clusters of small, polygonal to rounded grains intergrown with chromite and orthopyroxene; orthopyroxene-rich zones (pale green) consist of interlocking, larger oikocrysts of orthopyroxene containing numerous tiny chadacrysts of olivine.
Geochemistry:
Orthopyroxene (Fs24.8Wo1.8, FeO/MnO = 25.6), olivine (Fa30.2, FeO/MnO = 46.6), chromite [(Cr/ Cr+Al) = 0.828, Mg/(Mg+Fe) = 0.181-0.207, TiO2 = 0.71 wt.%]. Oxygen Isotopes (D. Rumble, CIW): replicate analyses of acid-washed bulk silicates by laser fluorination gave, respectively, d18O = 3.215, 3.509; d17O = 1.459, 1.611; D17O = -0.232, -0.234 per mil.
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10.7 gram complete slice - SOLD Item# 5480-107
10 gram Complete slice - NOT FOR SALE 
