AW: [meteorite-list] Tafassasset classification

From: M come Meteorite Meteorites <mcomemeteorite2000_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:54 2004
Message-ID: <20021002183946.6537.qmail_at_web10307.mail.yahoo.com>

Hello all

Another paired is probably Grein 004
Regards

Matteo

--- Norbert Classen <trifid_at_timewarp.de> wrote:
> Hello Bernd, Svend, Anne, and List,
>
> I discussed this subject several times with my old
> friend Dr. Otto,
> the German researcher who did the original analysis
> on Tafassasset
> (Freiburg), a stone that was originally submitted to
> the NomCom.
> as Tenere 001, a new ungrouped primitive achondrite
> similar to
> Divnoe, and the brachinites. He was more than
> suprised that the
> paired Tafassasset (Paris) has been submitted as an
> equilibrated
> CR chondrite.
>
> He gave me several reasons for his original
> classification of Taf-
> Frei as a primitive achondrite, but I can't remember
> them all right
> now (you know, I don't have a degree in mineralogy,
> petrology, and/
> or cosmochemistry). But I remember his central
> argument: primitive
> achondrites show a more or less completely
> recrystallized matrix
> that looks entirely different from even highly
> equilibrated chondrites.
> He showed me several thin sections of various PACs,
> and equilibrated
> chondrites, and in fact, Tafassasset closely
> resembles other primitive
> achondrites, such as Divnoe, Reid 027, and Zag (b).
> No equilibrated
> chondrite has such a coarse grained matrix, which is
> a typical sign
> for recrystallization (if I got Dr. Otto right).
>
> There were other points in Dr. Otto's argumentation
> that convinced
> me of his point of view, and his view is obviously
> backed up by the
> research that Dr. Zipfel et al performed on
> Tafassasset, more recently.
> Obviously, there is some resistance to accept the
> fact that this nice
> meteorite is no extraordinary CR - something that
> has to do with
> the self importance of certain scientists that made
> extraordinary
> claims, but failed to provide extraordinary proofs.
>
> Just my two Tafs,
> Norbert
>
>
> > -----Original Message-----
> >
> > Svend wrote:
> >
> > > J. Zipfel from the MPI in Mainz says that
> refractory lithophiles
> > > fractionated compared to a typical CR
> composition is leading to
> > > a possible classification as primitive
> achondrite. Does anybody
> > > know about a final classification yet?
> >
> >
> > Hello Anne, Svend and List,
> >
> > In the Abstract issue of MAPS (vol. 37-7, July
> 2002, p. A155),
> > Jutta Zipfel et al. published an abstract re:
> Tafassasset. In the
> > discussion part, the authors state:
> >
> > The figure illustrates that both samples have
> compositions clearly
> > fractionated from CI and other chondrite groups.
> Tafassasset has AI/Mg
> > and Mn/Mg ratios similar to other primitve
> achondrites, indicating
> > incipient partial melting involving mobilization
> of SiO2 (+/- A1203,
> > CaO, etc.) -, P205- and S-rich melts. Although the
> bulk compositions
> > are heterogeneous, characteristic element
> signatures (e.g., low Zn,
> > Mn/Mg,depletion in refractory lithophile elements)
> e x c l u d e
> > a relationship to CR chondrites and support
> pairing of Taf-Pa and
> > Taf-Frei*.
> >
> > * Taf-Pa is the Paris material - Taf-Frei the
> Freiburg material
> >
> >
> > Cheers,
> >
> > Bernd
> >
> > ______________________________________________
> > Meteorite-list mailing list
> > Meteorite-list_at_meteoritecentral.com
> >
>
http://www.pairlist.net/mailman/listinfo/meteorite-list
> >
>
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Received on Wed 02 Oct 2002 02:39:46 PM PDT