[meteorite-list] deformed etch pattern

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:02:29 2004
Message-ID: <3C946A96.E9CCAC3C_at_lehrer1.rz.uni-karlsruhe.de>

Greg Redfern wrote:

> an unusual etch pattern present in a Canyon Diablo Rim. Contrast
> the nearly featureless RIM etch pattern with that of an etched
> "plains" Canyon Diablo specimen. The Rim specimen was subjected
> to great heat from the impact event which essentially erased the
> Widmanstätten lines.


Hi Greg and List,

An interesting specimen! While the Widmanstätten pattern
is still recognizable, the bandwidth seems to have been
"squeezed", the lines are bent, the pattern looks much
more "diffuse" than the unshocked specimen recovered
from the surrounding plain.

By the way, Buchwald mentions 7 different alteration stages:

BUCHWALD V.F. (1975) Handbook of Iron Meteorites, Volume 2, pp. 390-397:

1. Original unshocked material
2. Shock-hardened masses
3. Shock-annealed masses
4. Shock-annealed to recrystallization
5. Shock-annealed to alpha2-transformation
6. Shock-annealed to alpha2-transformation and
   recrystallization of cohenite and schreibersite
7. Partly remelted specimens

Another interesting feature of your "rim specimen" is the small thin
schreibersite skeleton crystals some of which which are oriented at
a 90° angle in the middle of the picture.


Best Sunday
morning wishes,

Bernd
Received on Sun 17 Mar 2002 05:06:14 AM PST