[meteorite-list] iron meteorite cooling rates and Meteorite Men

From: Richard Montgomery <rickmont_at_meteoritecentral.com>
Date: Wed, 15 Dec 2010 16:47:46 -0800
Message-ID: <F88FD6988EEC4315B17B3BCC797CC083_at_bosoheadPC>

Hi List. (ot a chemist, me, just a collector, not ametorologist, just a
passionate meteorite guy.

This is mostly a question from Allan's post just now: I was always under
the impression that iron meteorites resulted from colliding differentiated
parent-bodies, and that the crystallization sequence was achieved after an
impact that exposed a core, molten NiFe suddenly ejected into space without
the shield of its former silicate mantle. Am I way off base? Does Thompson
structure develope within?


----- Original Message -----
From: "Alan Rubin" <aerubin at ucla.edu>
To: <meteorite-list at meteoritecentral.com>
Sent: Wednesday, December 15, 2010 4:21 PM
Subject: Re: [meteorite-list] iron meteorite cooling rates and Meteorite Men


> The iron meteorite cooling rates generally range from about 1 - 100?C/Myr.
> The reason for such slow rates is that the metal cores are buried deeply
> within silicate mantles and heat cannot readily escape. The coarseness of
> the Widmanstatten pattern is a function of cooling rate -- more slowly
> cooled irons will develop thicker kamacite lamellae. But there are two
> other factors that govern the coarseness of the structure -- the Ni
> concentration and the nucleation temperature. The lower the Ni
> concentration in the metal, the more kamacite will develop upon cooling.
> Metal that begins to nucleate at a higher temperature will have a longer
> period within which kamacite can grow.
>
>
>
>
>
> Alan Rubin
> Institute of Geophysics and Planetary Physics
> University of California
> 3845 Slichter Hall
> 603 Charles Young Dr. E
> Los Angeles, CA 90095-1567
> phone: 310-825-3202
> e-mail: aerubin at ucla.edu
> website: http://cosmochemists.igpp.ucla.edu/Rubin.html
>
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Received on Wed 15 Dec 2010 07:47:46 PM PST