Dear all
what an interesting and educating discussion! 
A short addition regarding diffusion of major and REE over time, and confirming what said by many in this discussion.  
Here a relevant example of a granulite that underwent HT >700°C (and with a peak at ~850°C) for at least 20 My, and where the garnet shows major element  homogenization (flat profile) even in cm-large crystals, whereas the REE, including Lu, still preserve growth profiles, at least at the microscale that LA-ICPMS can measure. 
Hermann, J. and Rubatto, D., Relating zircon and monazite domains to garnet growth zones: age and duration of granulite facies metamorphism in the Val Malenco lower crust. J. Metamorphic Geol. 21, 833 (2003).
kind regards
Daniela 



On 06/08/2010, at 1:18 PM, Alexander Schmidt wrote:

Dear all,

I am looking for a, let´s say list, with "closure temperature" estimates of Mg, Fe, Mn and Ca in high-grade garnets. I know that the term closure temperature might be inappropriate in this case, yet there has to be some estimate at which point during cooling these elements stop to diffuse.

regards,
Alexander

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Dr. Alexander Schmidt
Institut für Erd- und Umweltwissenschaften
Universität Potsdam
Karl-Liebknecht-Strasse 24/25
14476 Potsdam
Tel: +49(0)331-9775786

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Dr Daniela Rubatto
Associate Professor
Research School of Earth Sciences
The Australian National University 
Mills Road, Bld. 61
Canberra 0200 ACT
AUSTRALIA
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NOTE: August-December 2010, visiting professor at 
University of Lausanne
Institute for Mineralogy and Geochemistry 
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