Re-2: [meteorite-list] CH or CB Chondrite?

From: Jeff Grossman <jgrossman_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:55 2004
Message-ID: <5.1.0.14.2.20030914084208.01b881c8_at_gsvaresm02.er.usgs.gov>

I'm as confused about these groups as everybody else. Here's what I can add:

The NomCom does not make official decisions about meteorite groups. In
fact, nobody in the Meteoritical Society does. It's just a matter of
accepted usage. Joern Koblitz does what other editors, including the
Editor of the Meteoritical Bulletin, do: he decides what to do for himself.

Personally, I remain skeptical about the CB chondrite group. I am not
convinced that all of its members are even chondrites! That especially
goes for Bencubbin, Gujba, and Weatherford. QUE 94411 and HaH 237 are
apparently chondritic. Together, these 5 meteorites are too heterogeneous
texturally and chemically to qualify as a single discrete group, in my
opinion. Anyway, if I was editing a publication, I would still say
"Bencubbin-like meteorites" for the first 3 and "Carb. chondrite,
ungrouped" for the latter two. I've never looked at NWA 1814, but it too
sounds "Bencubbin-like".

All you have to do is look at the titles of these papers that Bernd cited
to understand that there is no consensus yet about how to classify all of
these CR-clan meteorites. The CR group and, for the most part, the CH group
seem secure and well accepted. But the Bencubbin-like ones are still
unsettled, in my opinion.

jeff

At 12:30 PM 9/14/2003 +0000, bernd.pauli_at_paulinet.de wrote:
>Alex wrote:
>
> > So my question is: is the CB designation still just a proposal (made
> > by the authors of these papers, and may be others), and has yet to
> > arrive at a status of general acceptance by the scientific community?
> > Should CH-BEN be abandoned? Are both of them valid side by side
> > for the time being?
>



> > Jeff Grossman, can you shed some light on this?
>
>When Weisberg et al. wrote their comprehensive paper on
>these primitive chondritic materials in 2001, they stated:
>
>Herein, we r e c o m m e n d designation of the CB
>(C, carbonaceous; B, bencubbinite) chondrites, a new
>grouplet that greatly extends of nebular/metal silicate
>and volatile element fractionations recorded in chondrites.
>These CB chondrites have significant similarities to the
>CR and CH chondrites, making theme part of the larger
>CR clan (e.g., Weisberg et al., 1990, 1995b).
>
>WEISBERG M.K. et al. (2001) A new metal-rich chondrite
>grouplet - CB chondrites (MAPS 36-3, 2001, pp. 401-418).
>
>So, at least, when the above paper was written and published,
>these designations (CBa, CBb) were still preliminary but if it
>still is ... well, Jeff may have more on this.
>
>Cheers,
>
>Bernd
>
>To: ase_at_planet-interkom.de
>Cc: meteorite-list_at_meteoritecentral.com
>
>
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Dr. Jeffrey N. Grossman phone: (703) 648-6184
US Geological Survey fax: (703) 648-6383
954 National Center
Reston, VA 20192, USA
Received on Sun 14 Sep 2003 09:10:25 AM PDT