[meteorite-list] Chondrule Formation vs Chondrule Conglomerate

From: Marc Fries <m.fries_at_meteoritecentral.com>
Date: Sat May 14 08:58:29 2005
Message-ID: <1229.69.140.92.248.1116075399.squirrel_at_webmail.ciw.edu>

Howdy

   My impression upon seeing this meteorite isn't that it necessarily
accreted quickly, but that it accreted in an environment that lacked
smaller particles. With no small bits scattered about, there was no
material to make up the typical matrix. Alternatively, even if it
accreted quickly in a "typical" environment, it would have gathered up
fine-grained bits and formed a matrix anyway. How you'd accrete a
meteorite in a region devoid of tiny bits is beyond me, though.
Perhaps a high velocity gas component swept out all the smaller
particles before accretion?
   This is a spectacular meteorite! Are there are plans afoot to register
it with some sort of special descriptor, like conglomerate or
matrix-free or something?

Cheers,
MDF

> G'day List,
>
> I was just reading through a section of 'Planetary Materials - Reviews in
> Mineralogy, Volume 36' regarding Chondrules when one particular sentence
> stuck out. It says:
>
> "A transient heating event melted the dustballs, and they were
> subsequently
> cooled, initially at rates around hundreds of degrees per hour or faster,
> before accreting into their chondritic parent bodies (e.g. Wasson 1993,
> Hewins 1996)."
>
> So, taking this at face value then how does one account for the "Chondrule
> Conglomerates" which have started popping up? E.g.
> http://www.meteorites.com.au/features/nwa2892.html
>
> I find it intriguing that if the chondrules were cooling at such a rapid
> rate, then these meteorites would need to have accreted faster or at least
> as fast. My 'very basic' understanding also would lead me to believe that
> if
> these are Type-3 chondrites, then it rules out later metamorphism? (E.g.
> Remelting of chondritic parent body.)
>
> Could these chondritic parent bodies have accreted this fast?
>
> Thoughts?
>
> Cheers,
>
> Jeff
>
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-- 
Marc Fries
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Carnegie Institution of Washington
Geophysical Laboratory
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Received on Sat 14 May 2005 08:56:39 AM PDT