Re-2: [meteorite-list] ringwoodite?

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:52 2004
Message-ID: <DIIE.000000440000106B_at_paulinet.de>

Tom aka James Knudson wrote:
 
> in a terrestrial rock, is there anything
> that resembles ringwoodite/shock veins?

Elton responded:

> Ringwoodite on earth is believed to be very plentiful just not on the
> surface. It is theorized to exist starting in a zone 50-80 kilometers
> below your foot. (Be it remembered that ringwoodite is the spinel habit
> / high pressure form of olivine (Mg,Fe SiOx))

"high pressure" is the key word in Elton's post. Rigwoodite [(Mg,Fe)2SiO4],
is often found in melt veins and melt pockets of highly shocked L chondrites
(shock stage S6) and forms in chondrites when meteoritic olivine is melted
by shock waves exceeding 50 GPa.

In terrestrial rocks it may be found because of the high pressures caused
by the large mass of our planet - in meteorites it exists because of the high
pressures released when asteroids collide.

Regards,

Bernd

>
> Superficially, I suppose there are a number of things which might
> resemble ringwoodite. Fluorite comes to mind but a hardness test should
> distinguish them. I don't remember seeing anything terrestrially that
> closely resembles a true shock fracture infilled with a melt material.
>
> Could you give a little more detail? Are you trying to identify
> something specifically or are you just asking so you could be prepared
> when you do find it?
>
> Elton
>
>
>
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To: jonee_at_epix.net
    knudson911_at_frontiernet.net
Cc: meteorite-list_at_meteoritecentral.com
Received on Mon 08 Sep 2003 07:08:03 AM PDT