AW: [meteorite-list] Sikhote-Alin Question

From: Martin Altmann <altmann_at_meteoritecentral.com>
Date: Wed Jun 28 05:50:59 2006
Message-ID: <001901c69a98$55c18450$4f41fea9_at_name86d88d87e2>

Here a pic with a troilite in Sikhote.
http://it.geocities.com/mcomemeteoritecollection/SikhoteAlin.JPG

I would guess, that it would have been rather a lenticular troilite torn
out. Schreibersite surrounding troilite or alone, wouldn't mark such a sharp
border in my opinion, especially not in Sikhote, where we find it often in
large skeletons of crystals.

But where I have problems of understanding, is, how such a circular shape
could have survived in a shrapnel at those high forces at the impact?
Wouldn't be some deformation to be expect, as e.g. it happened to this
inclusion in a shrapnel?
http://www.meteorite.com/gallery/mh_sikhote-11.jpg

Unfortunately now the pics from that auction seems not to be available
anymore. Weren't there other regular shaped pits connected to that hole?
To me it looks like a later deformation.

Just a guess,
Buckelboo



-----Urspr?ngliche Nachricht-----
Von: meteorite-list-bounces_at_meteoritecentral.com
[mailto:meteorite-list-bounces_at_meteoritecentral.com] Im Auftrag von Jeff
Kuyken
Gesendet: Mittwoch, 28. Juni 2006 11:23
An: Meteorite-list_at_meteoritecentral.com; bernd.pauli@paulinet.de
Betreff: Re: [meteorite-list] Sikhote-Alin Question

That would make sense Bernd. I initially noticed that it looks like two of
them right next to each other.

>formed parallel cylinders 10-40 mm in diameter

Cheers,

Jeff



----- Original Message -----
From: bernd.pauli_at_paulinet.de
To: Meteorite-list_at_meteoritecentral.com
Sent: Wednesday, June 28, 2006 6:38 AM
Subject: [meteorite-list] Sikhote-Alin Question


Eric wrote:

"Anyone want to take a stab at what it might be.
 I have no good explanations. Here is a link to
 the auction"

<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=3239&item=2300021628
91>

OK, ... taking a stab at what it might be. If it is NOT one of those
impact-produced surface craters that McHone and M. Killgore describe
in "Impact-produced surface craters on Sikhote-Alin irons" (cp. MAPS
33-4, Supplement, 1998, p. A101), it might be troilite surrounded by
schreibersite + swathing kamacite.

Buchwald wrote about Sikhote-Alin:

"Troilite occurs in minor amounts, mostly associated with the
schreibersite skeleton crystals which in many instances may have
nucleated upon the troilite. The troilite forms 1-10 mm nodules
and lenticular bodies. In most cases it forms the central part
of cm-sized, intricate, lace-like textures where schreibersite
filaments and hieroglyphs radiate from the troilite in structures
that suggest coarse-grained eutectics (+). Similar structures are
present in, e.g., Sao Juliao, Sandia Mountains and S a n t a
L u z i a*."

.., and on p. 1074, Buchwald wrote about Santa Luzia*:

BUCHWALD V.F. (1975) Iron Meteorites (Univ. of
California, 1975, Vol.3, excerpts from p. 1074):

"Not only is the troilite elongated parallel to the present exterior
surface,
but the schreibersite-metal eutectics (+) associated with it also appear to
have formed parallel cylinders 10-40 mm in diameter. Later, swathing
kamacite
has grown around these cylinders in the solid state to form concentric
shells,
5-15 mm thick. Troilite forms the central part of the cylinders, but, since
it pinches and swells irregularly, it may or may not be present in a given
section perpendicular to the cylinders."

(+) McSWEEN H.Y. (1999) Meteorites and Their Parent Planets
Cambridge University Press, Glossary, p. 290): the liquid that
occurs at the lowest temperature in a chemical system.

So, maybe, we are looking at a cross-section of such a cylinder.

Well, probably not quite as interesting as the ongoing discussion
about fraudulent trade practices, but, anyway, ... my stab ;-)


Bernd

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Received on Wed 28 Jun 2006 05:50:47 AM PDT