Hi Mendy, Yes, NWA 7731 crust is quite fresh. The standard weathering grades for ordinary chondrites based on the oxidation of iron-nickel-metal is somewhat problematic for the most unequilibrated of the 3-subtypes because the matrix is actually a very fine opaque mixture of sulfur and iron that is hard to characterize for degree of weathering. In the meantime, since it was classified, we have done oxygen isotopes on the bulk sample and they are very heterogeneous (some actually plot on the TFL) as one would expect based on the earlier work on Semarkona. There has been ion probe and Raman done at Hawaii and some of this will be reported at the 2014 LPSC -- I'll post the abstract when they are published later this January. There is some indication that extraterrestrial aqueous alteration has affected the matrix -- but even Semarkona has some of this type of aqueous alteration. Subtypes <3.00 ( like L2.9 etc.) are not used in OC even though some aqueous alteration might be present. A while back Hutchison et al. (1987) proposed that Semarkona is in fact LL2, but it doesn't seem like that idea ever caught on.
Carl Agee ************************************* Carl B. Agee Director and Curator, Institute of Meteoritics Professor, Earth and Planetary Sciences MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 Tel: (505) 750-7172 Fax: (505) 277-3577 Email: a...@unm.edu http://meteorite.unm.edu/people/carl_agee/ On Fri, Dec 20, 2013 at 10:13 AM, Mendy Ouzillou <ouzil...@yahoo.com> wrote: > Wow Darryl, that slice of NWA7731 is amazing. I vaguely recall a discussion > on the list regarding this L3.00, but do not recall the weathering. Based on > the description in the MetBull it is hard to ascertain the actual weathering > grade. From the picture of the crust in the listing, it looks pretty fresh. > > Hoping Carl can jump in and provide some insights and hoping I have not asked > this vaguely familiar question before. > > > Mendy Ouzillou > > > >>________________________________ >> From: Darryl Pitt <dar...@dof3.com> >>To: meteorite-list List <meteorite-list@meteoritecentral.com> >>Sent: Thursday, December 19, 2013 9:17 PM >>Subject: [meteorite-list] ADVERT: Subtype 3.00 — NO RESERVE >> >> >> >> >>Hi Folks! >> >>Hoping you're well. >> >>Select auctions ending late this afternoon — all with no reserve: >> >>http://bit.ly/1gHpc8M >> >>Featuring.... >> >>NWA 7731 - subtype 3.00 - along with Semarkona (which is untouchable) this is >>THE most primitive, unequilibrated planetary material that exists—and it's a >>complete slice! >> >>NWA 5717 - subtype 3.05 - two edges of fusion crust along with a rare dark >>inclusion; >> >>TISSINT - two edges sides of fusion crust; >> >>VALERA - the only meteorite known to have killed an animal; >> >>KAINSAZ - rare CO3.2 witnessed fall; >> >>NWA 7944 - a new, fresh Martian meteorite; >> >>NWA 7214 - the freshest aubrite obtainable (W0/W1) that is not a witnessed >>fall; >> >> >>Good luck and Happy Holidays! >> >> >>______________________________________________ >> >>Visit the Archives at http://www.meteorite-list-archives.com >>Meteorite-list mailing list >>Meteorite-list@meteoritecentral.com >>http://six.pairlist.net/mailman/listinfo/meteorite-list >> >> > ______________________________________________ > > Visit the Archives at http://www.meteorite-list-archives.com > Meteorite-list mailing list > Meteorite-list@meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list ______________________________________________ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
