[meteorite-list] Chondritic parent bodies

From: Jeff Grossman <jgrossman_at_meteoritecentral.com>
Date: Wed, 09 Sep 2009 14:47:03 -0400
Message-ID: <4AA7F827.4010409_at_usgs.gov>

Backing up and extending what Alan said, in current usage, a slash means
one of two things: 1) there are properties of this meteorite that are
intermediate or transitional between the two classes, or 2) The
classifier could not decide which group it was due to some kind of
limitation in methodology or samples. In the case of Holbrook, it is
the first meaning. A variety of properties have been measured that put
Holbrook near the L/LL boundary, including O isotopes and metal composition.

So what does that mean? Nobody knows. Either the L and LL asteroids
had overlapping properties, in which case we don't know which was
originally home to Holbrook, or there are other asteroids with
intermediate properties that could be the parent of Holbrook.

The L and LL groups are not particularly well resolved from each other
in many properties, although it is certain they are not all from one
asteroid. I am confident that quite a number of classified L chondrites
are from the LL body and vice versa, and not just limited to the ones
that are called L/LL.

Jeff

Dave Gheesling wrote:
> Bernd, Alan, and List,
> Thank you both for the diplomatic and informative responses. While we're on
> the subject, might one of you (or anyone else) expand on, say, the L/LL6
> classification designation? Holbrook was recently moved from an L6 to such
> a classification, and I have a few others in my collection which are not
> breccias (and presumably are entirely from one parent body and not two) but
> yet have this classification assigned to them...which, "by definition,"
> would imply connection with both the L and LL parent bodies, presumably
> anyway.
> Thanks, and all best,
> Dave
> www.fallingrocks.com
>
> -----Original Message-----
> From: meteorite-list-bounces at meteoritecentral.com
> [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of
> bernd.pauli at paulinet.de
> Sent: Wednesday, September 09, 2009 12:47 PM
> To: Meteorite-list at meteoritecentral.com
> Subject: [meteorite-list] Chondritic parent bodies
>
> Hello Dave, Alan, and List,
>
> Here is a paper that may be of interest with regard to LL chondrite parent
> bodies:
>
> Dixon E.T., Bogard D.D. and Garrison D.H. (2002) 40Ar-39Ar Chronology of LL
> Chondrites (Lunar and Planetary Science XXXIII, 1114.pdf).
>
> They even discuss *three* models:
>
> 1. The onion-shell model
> 2. The rubble-pile model
> 3. The re-assembly model
>
>
> Best wishes,
>
> Bernd
>
>
>
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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 Wed 09 Sep 2009 02:47:03 PM PDT