AW: AW: [meteorite-list] Tafassasset classification

From: Norbert Classen <trifid_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:54 2004
Message-ID: <NCBBKMGDKLMGIBALJOFCKEMKCOAA.trifid_at_timewarp.de>

Hi Matteo, hi List,

"Grein 004" as well as "Tenere 001" are just synonyms for the
Tafassasset Freiburg mass, a single stone weighing 3610 grams.
It's no pairing. Just to avoid further confusion...

Best,
Norbert

> -----Original Message-----
>
> 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
> > >
> > > ______________________________________________
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> > >
> >
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> > >
> >
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>
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Received on Wed 02 Oct 2002 05:37:32 PM PDT