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Hi Dave-
I'm sure you know this, but this question would appear to be relevant in a strict sense only for the first bit of garnet to form.  After that, the bulk composition is altered by the sequestration of material inside existing garnet.  So, "garnet cores" isn't sufficient, it seems to me; you'd need to specify "garnet cores of the largest garnet in a hand specimen" (presuming, of course, that a hand specimen is equivalent to the volume of major-element equilibration during crystallization, which is probably only roughly correct).

(cf, for example: Evans, T.P., 2004a, A method for calculating effective bulk composition modification due to crystal fractionation in garnet-bearing schist; implications for isopleth thermobarometry: Journal of Metamorphic Geology, v. 22, p. 547-557)
-Dave

On Aug 3, 2012, at 9:33 AM, Dave Pattison wrote:

Hi all. There have been a number of studies published in which garnet compositional isopleths, for garnet cores, give P-T intersections that plot above the temperature of the calculated garnet-in line for the rock composition in which the garnet isopleths were measured. Sadly, I never tabulated these, so I am appealing to the community to send me references to papers in which this phenomenon has been documented. Many thanks, Dave
 
David RM Pattison, Department of Geoscience,
University of Calgary, Calgary, Alberta, Canada, T2N 1N4.
Phone: Canada 403 220 3263
 


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Western Washington University
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