[meteorite-list] Slickenside not only tectonic

From: Matt Morgan <mmorgan_at_meteoritecentral.com>
Date: Thu Apr 22 09:49:03 2004
Message-ID: <000201c145c8$ea604d00$71af1618_at_2K>

Hi everyone:
I would like to add that swelling clays in soils can also produce
slickensides. Tectonic events are not the only cause.
They do occur, albeit in smaller scale than from tectonic forces, all
over the Front Range of Colorado due to expandible and collapsible
solis. Basically the soil will heave then relax, multiple times,
creating multiple slicekenside surfaces. Could this happen on a
meteorite parent body?

They can occur from impact as well, by reactivating old fault planes.
I've seen examples of these from Vredefort (I think). But you cannot
always tell that they are FROM the impact event.

Best wishes,
==========
Matt Morgan
Mile High Meteorites
www.mhmeteorites.com
P.O. Box 151293
Lakewood, Colorado 80215
email: mmorgan_at_mhmeteorites.com
Fax: 303-763-6917


-----Original Message-----
From: meteorite-list-admin_at_meteoritecentral.com
[mailto:meteorite-list-admin_at_meteoritecentral.com] On Behalf Of
Starbits_at_aol.com
Sent: Tuesday, September 25, 2001 12:41 AM
To: bernd.pauli_at_lehrer1.rz.uni-karlsruhe.de; moonrock25@webtv.net
Cc: meteorite-list_at_meteoritecentral.com
Subject: Re: [meteorite-list] Slickenside


<Charlie wrote: What I would like to know is if this slickenside formed
during a tectonic event on the parent body, an impact event in space,
explosive breakup in earth's atmosphere, or other?>

Slickensides are formed by tectonic events. They are formed when
opposite
sides of rock faults move in different directions. The extreme pressure

generates frictional heat as the rock faces are forced past each other
partially melting a thin veneer of rock at the interface. This results
in a
smoothing of rough edges and a polished looking surface. Harder
protrusions
gouge grooves in the opposite rock as it slides by.

They would not be formed by explosive breakup in the earth's atmosphere.
In
such a breakup pieces would be flying apart from each other whereas in
slickensides the opposite is happening the rock faces are being forced
against each other.

They could possibly be formed by an impact event in space, not by the
explosive part of the impact, but by tectonic reactions along faults
during
or after the impact.

<Bernd wrote: ... and some meteorites that are reported to exhibit
slickensides:>

I have a piece of Mocs which shows good slickensides. There is a photo
at
the following URL. It is not a great photo, but you can see the
grooves and
that some parts are more reflective (polished) than others. Another
meteorite that exhibits slickensides is Gobabeb.

http://www.geocities.com/starbits.geo/photo/slickensides.JPG

Eric Olson
http://www.star-bits.com

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Received on Tue 25 Sep 2001 09:49:35 AM PDT