[meteorite-list] Incomparable New Meteorite - NWA 5480

From: Greg Hupe <gmhupe_at_meteoritecentral.com>
Date: Sat, 20 Dec 2008 16:21:04 -0500
Message-ID: <9EC26156701B4337A0359CA78172A959_at_Gregor>

Dear List Members,

To celebrate the holiday season, I would like to announce an exciting new
meteorite:

NWA 5480; a fresh, and incomparable new Olivine Diogenite. Several stones
were found in Arg Shash, Mali in July 2008 by nomadic meteorite hunters.
Samples from two different stones were sent to the University of Washington
(UofW) where they were analyzed and determined to be meteoritic. Eventually
seven stones with a combined Total Known Weight (TKW) of 4912 grams were
purchased in October/November 2008, and the full type sample was analyzed at
UofW and multiple oxygen isotope studies were performed at the Carnegie
Institution, Washington, DC. Cosmic-ray exposure (CRE) analysis is currently
being performed by scientists in Japan to determine how long this meteorite
had been in space before landing on Earth. With the addition of NWA 5480,
there are now seven known members of the "Olivine Diogenite" group (three
specimens are from Antarctica and four are from Northwest Africa). NWA 5480
is texturally very different from the others and is the most olivine-rich,
and may represent the deepest specimen of the Vesta mantle yet discovered!


Image of 108.2-gram complete slice displaying mottled appearance of matrix:
http://www.lunarrock.com/nwa5480/nwa5480slice.jpg



Close-up image of NWA 5480 showing gemmy crystals (image measures 25mm
wide): http://www.lunarrock.com/nwa5480/nwa5480closeup.jpg



Image of large 1.5cm chromite grains on 507-gram stone:

http://www.lunarrock.com/nwa5480/nwa5480chromite.jpg



False-color BSE image of NWA 5480 showing olivine grain distribution:

http://www.lunarrock.com/nwa5480/nwa5480bse.jpg



NWA 5480 is a very dense and hard meteorite but takes an extremely nice
polish, which highlights the dazzling crystals that make up the matrix of
this remarkable material.



Classification submitted to the Meteoritical Bulletin for NWA 5480:

Northwest Africa 5480

Mali

Find: July 2008

Achondrite (olivine diogenite)



History: Found near Arg Shash, Mali in July 2008 and purchased by Greg Hup?
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.

Classification: Achondrite (olivine diogenite).

Specimens: A total of 21.4 g of sample and one polished thin section are on
deposit at UWS. Mr. G. M. Hup? holds the main mass.



I would like to thank the scientists who tirelessly studied NWA 5480.
Without their hard work, we would not be able to enjoy this fantastic new
Olivine Diogenite!



Best regards,
Greg

====================
Greg Hupe
The Hupe Collection
NaturesVault (eBay)
gmhupe at htn.net
www.LunarRock.com
IMCA 3163
====================
Click here for my current eBay auctions:
http://search.ebay.com/_W0QQsassZnaturesvault
Received on Sat 20 Dec 2008 04:21:04 PM PST