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

[Alan Rubin]

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: aerubin at ucla.edu
website: http://cosmochemists.igpp.ucla.edu/Rubin.html