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" <aeru...@ucla.edu>
To: <meteorite-list@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 - 100ºC/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: aeru...@ucla.edu
website: http://cosmochemists.igpp.ucla.edu/Rubin.html
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