[meteorite-list] breccia formation

From: Dave Harris <entropydave_at_meteoritecentral.com>
Date: Thu Apr 22 09:55:43 2004
Message-ID: <003701c197b1$1a0f4b20$849f0050_at_default>

Hello,
I've just got some cute little NWA 788 from Jim Strope (thanks Jim!) and
noted they are brecciated. This got me wondering about how the process of
brecciation occurred in the parent body and I realised that I didn't know.
So, can I assume that the meteorite, prior to ejection from the parent
asteroid was already a brecciated rock lying on the surface or embedded in
the lithosphere, or does brecciation occur when the regolith is pounded by
an impact, fusing together all the different rocks lying around on the
surface of the planetoid?
I would have thought that if brecciated meteorites were formed by fusing
together the different lithologies lying about on the parent body at the
time of impact, then shock melts would be very apparent - I am not aware
that this is the case in the vast majority of brecciated meteorites
therefore implying that the brecciation I see was already in the parent rock
prior to ejection.
If that is the case, how did the different lithologies get compressed
together in the first place? I didn;t think that there would have been
enough gravitational attraction on a 'typical' parent body to have enabled
the processed that would allow the asteroid to be able to create this sort
of metamorphosed (ie brecciated) rock.
Please forgive my obvious "geology 101" type question, but I am, after all,
starting a geology degree so need all the help I can get!
I know squat all but I need to learn!!!!

very best and await your wisdom to illuminate my intellectual darkness!

--
In gentle decay,
dave
http://www.meteorites.ic24.net/index.html
http://www.thc.u-net.com/davethc1.htm
"I have a proof that x^n+y^n=z^n never has integer solutions for n>2.
However, it won't fit into my signature file...."

Received on Mon 07 Jan 2002 02:25:43 PM PST