[meteorite-list] AD-NWA 6928 A Rare Noritic Diogenite meteorite

[Gary Fujihara]

Aloha listoids,

One week ago I made a pre-announcement of a new achondrite meteorite that has turned out to be an incredible new diogenite.  I would like to introduce NWA 6928 NORITIC DIOGENITE.

At first glance this specimen was thought to be a eucrite, but after analysis, Dr Tony Irving has revealed that this is a rare specimen related to diogenites, as in fact one of only three known noritic diogenites. Scientists at University of Washington, among other research institutes, have been involved in a revision of the terminology for diogenites, expanding them from typical varieties (now called orthopyroxenitic diogenites) to harzburgitic diogenites (what we used to call olivine diogenites) and dunitic diogenites (like NWA 2968 and NWA 5784), and even to those with >10% plagioclase (logically noritic diogenites). NWA 6928 can in no way be a eucrite, because the pyroxene is not pigeonite, but instead orthopyroxene (with a composition way more magnesian and in the range for diogenites).  Inclusions of chromite are present, and exhibits similar evidence for shock (undulose extinction, cataclasis) to that seen typically in (orthopyroxenitic) diogenites.  Dr Irving has conferred with Dr Ted Bunch on this analysis, who concurs.   

NWA 6928 is an extremely fresh specimen with relatively coarse grained, cumulate texture composed of 80 vol.% orthopyroxene (Fs33.4-34.1Wo2.5-1.2; FeO/MnO = 31-33) and 19 vol.% interstitial, anorthitic plagioclase, with accessory Ti-Al-bearing chromite, troilite and merrillite.  This specimen appears to be a very fine example of a rare type of achondrite related to diogenites.  A sample has been sent to Okayama University for oxygen isotope analysis.

There is no doubt this is an intriguing new meteorite, and I am honored to bring this specimen to the public.  

NWA 6928 uncut stone
http://bigkahuna-meteorites.com/Images/NWA6928-MMa.jpg

NWA 6928 polished slice
http://bigkahuna-meteorites.com/Images/NWA6928-7.79a.jpg

NWA 6928 available full slices
http://bigkahuna-meteorites.com/NWA6928.html

Thanks for looking and have a great day!

Gary Fujihara
Big Kahuna Meteorites (IMCA#1693)
105 Puhili Place, Hilo, Hawai'i 96720
http://bigkahuna-meteorites.com/
http://shop.ebay.com/fujmon/m.html  
(808) 640-9161