[meteorite-list] Portales Valley Classification Info

From: Jeff Grossman <jgrossman_at_meteoritecentral.com>
Date: Tue May 17 13:32:23 2005
Message-ID: <5.1.0.14.2.20050517123117.021a0d60_at_gsvaresm02.er.usgs.gov>

I was the lazy editor of the MetBull when PV fell, so I can tell you the story.

Basically, two scientists were in communication with the NomCom during the
classification, Dave Kring and Alan Rubin. There were two schools of
thought on what to call it, and these were not really that far
apart. Kring, the person that submitted the initial classification,
described PV as an H6 chondrite with abundant veins of metallic shock
melt. His initial interpretation was that the source of the metal was the
H chondrite host, and that the metal was basically the same thing you see
in small shock veins in many chondrites, just on a larger scale. All of
the material appeared to be of H chondrite affinity and many clasts were
H6. Rubin wanted to call it an H chondrite impact melt breccia. He too
considered all the components to be of H chondrite origin, but thought the
IMB designation would alert people to the fact that the texture was so
interesting. (Of course, the texture is different from other melt breccias
as well.)

As you can see, both researchers thought PV was H chondrite material and
both thought that shock effects dominated the texture. So there was no way
we were going to call it a new group... it was from the H parent body and
didn't contain weird or foreign material. In the end, we agreed to go with
the submitter's classification as an H6 with remarkable shock effects, and
Rubin agreed that he'd call it an H impact melt breccia in the literature
(which he did). It hardly seemed to matter since these two classifications
were so close.

If I had to publish the announcement again today as editor, knowing what we
do now, I'd probably go with "H melt breccia". But there is still no clear
line between H6 chondrites with abundant shock veins and melt pockets and
those like PV, which probably should have the presence of melt noted in the
classification.

Jeff

At 12:11 PM 5/17/2005, Tom Knudson wrote:
>Hi List, back in March of 2004, I made a lot of enemies on the list for
>asking;
>
>" I have to ask, was Portales Valley classified as a H6 ordinary
>chondrite because "they" were to lazy to make up a new classification? It
>would seem to me that this unique meteorite deserves it's own group instead
>of being shoved into an already existing group.
> I do not feel like we have found every type of meteorite yet, are "they
>going do this with all of them, just sticking them in existing categories,
>or will they make a new one if need be?"
>
>I was called everything from an idiot to a stupid mother $#*&^# by a lot of
>people on the list for questioning the classification. I was put in my
>place, never question the scientists, if they said it was a H6 ordinary
>chondrite, then it was!
>
>Just thought it was interesting . : )
>
>
>Thanks, Tom
>peregrineflier <><
>
>----- Original Message -----
>From: "Robert Woolard" <meteoritefinder_at_yahoo.com>
>To: <meteorite-list_at_meteoritecentral.com>
>Sent: Monday, May 16, 2005 7:21 PM
>Subject: [meteorite-list] Portales Valley Classification Info
>
>
> > Hello List,
> >
> > Well for years now, I know a lot of us were puzzled
> > by the classification of Portales Valley as an " H6
> > ordinary chondrite". (See my article in the May 2001
> > issue of Meteorite, titled " Portales Valley - A Not
> > So Ordinary (Ordinary Chondrite??)! " In the recent
> > past, the classification was modified a bit, being
> > changed to read as an " H6 Impact Melt Breccia ".
> >
> > I am excited to be able to say that there is a
> > distinct chance the true uniqueness of PV may soon be
> > reflected in a possible new moniker for this
> > intriguing meteorite. David Weir was kind enough to
> > make me aware of a new and comprehensive paper by Alex
> > Ruzicka, Marvin Killgore, David Mittlefehldt, and Marc
> > Fries in the current MAPS. In this detailed work, we
> > now have the proposed reclassification of PV as an "
> > H7, metallic-melt breccia (primitive achondrite)",
> > with the case made for a new meteorite type
> > designation of "Portalesite" due to this metallic-melt
> > breccia characteristic.
> >
> > You can read David's updated description of PV on
> > his excellent website here:
> >
> > http://www.meteoritestudies.com
> >
> > Many thanks to David for news of this exciting
> > paper, and to the authors of the paper as well.
> >
> > Sincerely,
> > Robert Woolard
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > __________________________________
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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 Tue 17 May 2005 01:32:18 PM PDT