[meteorite-list] Terrestrial Pseudotachylites

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:53 2004
Message-ID: <DIIE.0000004000001CAF_at_paulinet.de>

Matt wrote:

> Pseudotachylites are not *just* impact-specific fault melts.
> They may also form along TECTONIC fault planes here on earth
> and I have heard of them associated with mass-wasting deposits.


Hello Matt and List,

RONDOT J. (1989) Pseudotachylite and mylolisthenite
(Meteoritics 24-4, 1989, pp. 320-321, excerpts):

The name pseudotachylyte (now pseudotachylite) has been adopted in
recognition of the fact that these rocks have a great similarity to
tachylyte, in particular its dark color and intrusive aspect. The name
mylolisthenite, from "mulon" to mill and "olistanein" to slide, has been
introduced to distinguish a special type of autochthonous breccia different
from pseudo-tachylite and from allochthonous breccia filling fractures in
the bottom of the astroblemes. Unlike the pseudotachylites, the mylolisthenites
are pale grey, green or red and are found in sedimentary as well as in crystalline
rocks. Tectonic pseudotachylite, found in small quantities in crystalline rocks
along some major fault and thrust planes, has been the object of a lot of descript
-ions and studies. The complex network of black, aphanitic or glassy veins is filled
with partly fused rock with crystalline powder. Pseudotachylite found in highly deformed
rocks is itself rarely deformed and it is formed in a single episode of slip. It is a
product of faulting in the brittle zone of rock deformation.


Best wishes,

Bernd
Received on Thu 25 Mar 2004 12:32:33 PM PST