[meteorite-list] Slickenside

From: James Baxter <jbaxter112_at_meteoritecentral.com>
Date: Thu Apr 22 09:49:02 2004
Message-ID: <200109240313.XAA16738_at_web1.po.com>

Hello Berndt,Charlie

As I recall from my past geology courses eons ago slickensides are
formed from the movement of rocks relative to each other along
fracture planes in fault zones in terrestrial rocks.A kind of cool
thing you can do is rub your finger along the grooves which make up
the slickensides.They feel rough when you move your finger in the
direction opposite to which the adjacent rock moved to form the
slickesides and smooth when you rub in the same direction the
adjacent rock moved because it sheared off any microscopic
projections or rough edges as it moved.Again based on my feeble
memory of the distant past,that's one way to determine movement
diection along a fault in the field.

I have two pieces of Zag each of which show killer slickensides so I
assume this is a common feature of Zag and must represent mechanical
disruption at some point in its history.

Best Wishes,
JIm Baxter



------------------ Reply Separator --------------------
Originally From: Bernd Pauli HD <bernd.pauli_at_lehrer1.rz.uni-
karlsruhe.de>
Subject: [meteorite-list] Slickenside
Date: 09/23/2001 11:00pm


Charlie wrote:

> Can anyone clarify for me the origin of slickenside in meteorites?
I
> understand the term as it applies to terrestrial soils and
sediments. I
> have a large individual of Plainview(1917). It's a flat specimen,
with
> one side fully crusted. The other side looks more like a broken
> surface, with crust lipping over the edge from the crusted side.
This
> "broken" surface is covered with glossy striations in large patches
that
> I'm assuming is slickenside. 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?


Hello Charlie and List,

All I can contribute is a comment from our former, very
competent list member Frank Stroik many years ago:

"slickensides are identified by shiny mirror like surfaces on an
otherwise rough rock - they are the product of faulting in a rock
body; as the crust shifts, even slightly, the roughness of the rock
tends to smooth."

... and some meteorites that are reported to exhibit slickensides:

Magombedze (H6): In places where the meteorite has been broken exactly
along these veins, exposed metal grains are smeared and streaked and
show obvious slickensides [MacPHERSON G.J. et al. (1993) Magombedze:
A new H chondrite with light-dark structure (Meteoritics 28-1, 1993,
138-142)].

ALHA77225 (H4): The B surface has what appear to be slickensides, but
because of the severe weathering of the specimen it is impossible to
determine this unambiguously [MARVIN U.B. and MASON B. (1982) Catalog
of Meteorites from Victoria Land, Antarctica, 1978-1980 (Smithsonian
Contributions 24, p. 23)].

ALHA77254 (L5): The B surface has slickensides [Marvin, U.B. and
Mason B. (1980) Catalog of Antarctic Meteorites, 1977-1978,
Smithson. Contr. Earth Sci. 23, p.32].

ALHA78108 (H5): Many slickensided surfaces were exposed during
processing [MARVIN U.B. and MASON B. (1982) Catalog of Meteorites
from Victoria Land, Antarctica, 1978-1980 (Smithson. Contr. 24, p.
28)].

LON 94102 (C2): Slickenside-like features are visible on
the surface (Macroscopic Description: Kathleen McBride)

> Also, regarding Plainview(1917), can anyone tell me if the newest
> edition of the Catalog makes reference to this meteorite being a
> possible witnessed fall from 1903(?)?

No, Charlie, it doesn't.

Best wishes,

Bernd

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Received on Sun 23 Sep 2001 11:13:15 PM PDT