[meteorite-list] DIs in Fred's TAN 057

From: David Weir <dgweir_at_meteoritecentral.com>
Date: Tue Nov 1 14:54:30 2005
Message-ID: <4367C7F1.6080705_at_earthlink.net>

Hello Frederic,

It's ashame that you learned about your classification by UCLA from me
first, by reference to a published paper, rather than from the
laboratory management to whom you submitted it (and paid?). Since the
paper I referenced is in the newest (August 05) issue, it won't become
available for non-subscribers until next year. Your meteorite,
Tanezrouft 057, was simply included in an appendix table along with the
proposed new weathering index, which was the subject of the paper. The
petrologic type of the various CK and R chondrites were also given. As
Bernd suggested, the possibility of a typo is always possible. Since you
have obtained several disparate classifications, I will be interested to
follow the future research on this one.

The CK-CV group designation has been the subject of some debate, as can
be seen in the paper by Greenwood et al. (2003):

"Are CK Chondrites Really a Distinct Group or Just Equilibrated CVs?"

http://www.lpi.usra.edu/meetings/metsoc2003/pdf/5179.pdf

I hope your meteorite can help with this investigation.

Regards,
David



Meteoriteshow wrote:

> Hello david,
>
> Many thanks for your reply to my post on the List and please excuse
> me for my late reaction as I was out of home the all day since I sent
> my own posts. Your post is very interesting to me as I was still
> expecting the results of UCLA study on the CKs that John Wasson was
> supposed to send me. Therefore I did not know that they had reached
> such a conclusion, classifying Tnz057 as a CK5 rather than a C4an!!!
> What a surprise! Especially when Bertrand Devouard always told me
> after several studies on the more than 100g specimen that he has,
> that he is sure of the 4 degree of metamorphism but the problem being
> to "locate" it between the CV and CK groups. I have inserted in my
> website an abstract that Bertrand presented during a conference in
> Agadir in May this year and that you can see at
> http://info.meteoriteshow.free.fr/Archives-Meteoriteshow/angl/Tnz057/abstract-Tan057-B.Devouard.pdf
> in which he wrote what I just said and also mentioned a first
> approach of one of the main DIs that he found quite similar to the
> matrix of the main structure but with a different mineralogical
> composition with about 35%of pyroxene.
>
> When working on the classification, the first result provided to the
> Nom. Com. was to classify Tnz057 as a CK4. When working more on
> different areas of the type specimen, they then found out that
> sometimes the results were leading to the CK group and sometimes to
> the CV group... therefore the Nom. Com. was informed before the final
> publication of the MB87 and Tnz057 was classified as a C4an.
>
> Actually, should you have a pdf of the results obtained by UCLA, I
> would be glad to get a copy! I do not know if it is part of it, but
> the only results I had received from John Wasson is the fig1 of the
> paper and his first conclusion at that time was: "Here is a copy of
> Fig. 1 or our CK paper. Tenzrouft belongs to a group of CK
> chondrites that show a moderate depletion in Ni and Co. Some CKs
> also show a strong depletion in Au and Se but the Tenezrouft samples
> show only small depletions in these elements. We are confident that
> this reflects loss of on or more phases, probably sulfide(s), that
> contain these elements. We're not yet sure where the depletion
> occurred, in the parent body or during terrestrial weathering. My
> current guess is parent body, but that may change by the time we
> submit the paper."
>
> Then you can see that as some of the meteorites that are a bit
> "special", Tnz057 is also "on the edge" and I guess that we will have
> to wait for more woek to be done on it before we can have a final
> classification...
>
> Many thanks for your interest and all the best!
>
> Frederic Beroud http://www.meteoriteshow.com IMCA member # 2491
> (http://www.imca.cc/)
>
>
> ------------------------------------------------------------------------
>
>
Received on Tue 01 Nov 2005 02:54:25 PM PST