[meteorite-list] Re: Slickenside

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu Apr 22 09:49:03 2004
Message-ID: <20010925171647.85606.qmail_at_web10407.mail.yahoo.com>

<Eric wrote: "They would not be formed by explosive
breakup in the earth's atmosphere.">

I still wouldn't rule out this event as being one of
the causes of the deformation we are seeing in some
meteorites. If you replace the words "explosive
breakup" with "rapid deceleration in the atmosphere",
you are now dealing with unimaginable compressional
forces that are easily sufficient to produce these
kinds of deformation.

To paraphrase a published paper that I recently read,
it's as if the rear of the bolide is trying to pass
through its front end.

The last time (Feb 1999) that we had this discussion,
I suggested that we may need to come up with a new
term for this type of deformation in meteorites,
because the trained geologists were having difficulty
extending this terrestrial phenomenon to planetary
bodies of low mass/gravity. But, now, I would like to
withdraw that suggestion. If we can extend the term
slickenside to processes involving low confining
pressures (as in the example given by Matt Morgan)
then its usage can be broadened to include the various
forms of deformation exhibited in meteorites.

And it's such a great sounding word, too. What could
replace it?

Bob V.


------------- Original Message ------------------
[meteorite-list] Slickenside

Starbits_at_aol.com Starbits@aol.com
Tue, 25 Sep 2001 02:41:01 EDT

<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 01:16:47 PM PDT