[meteorite-list] NWA 1836 (Twisted Sister) - Cataclastic?

From: Jeff Kuyken <info_at_meteoritecentral.com>
Date: Thu Aug 4 02:35:23 2005
Message-ID: <001b01c598be$b53980e0$b3578b90_at_mandin4f89ypwu>

G'day,

I have some questions about NWA 1836 I'm hoping someone may be able to
answer or clarify.

The classification description says that NWA 1836 is a "highly contorted
mass of eucrite clasts with cataclastic mantles that are in turn covered by
partially melted to recrystallized masses."

>From what I could find "cataclastic" refers to rocks that experience sudden
high-pressure and low-temperature conditions, resulting mainly in a change
in texture of the original rock. My understanding is that this term is
usually reserved for rocks found in places like those along tectonic fault
lines.

So are these conditions present in the parent-body? I would have thought
that most high-pressure conditions would also be associated with
high-temperature conditions. (i.e. impact) So is there in fact enough
movement within the parent-body to cause a cataclastic effect and would it
just be limited to some of the larger bodies?

And the last part mentions "that are in turn covered by partially melted to
recrystallized masses." Does this mean there was later melting from a
separate and/or different event?

Sorry, there are a few questions here but I found it to be quite
interesting. If it is indeed "cataclastic" in the traditional sense then I
guess NWA 1836 could tell us a lot more about the kind of conditions present
on the parent-bodies, making this meteorite even more special.

Thanks in advance,

Jeff
Received on Thu 04 Aug 2005 02:35:26 AM PDT