Hi folks,
This message reminds that next month is the 25th anniversary of Frank Spear's paper on - you guessed it! - the effect of garnet fractional crystallization on (reactive) bulk compositions and mineral assemblages.
This approach first fully quantified chemical impacts in a fundamentally predictable fashion and became the cornerstone of all subsequent Gibbs method - type models.
His paper also addresses the effects of diffusional relaxation of garnet growth zoning as rocks heat.
Here's the reference: Spear, FS (1988) Metamorphic fractional crystallization and internal metasomatism by diffusional homogenization of zoned garnets. Contributions to Mineralogy and Petrology, v. 99, 507-517.
It's founded on Duhem's theorem, which constrains P-T-X-M in rocks, and also published 25 years ago: Spear, FS (1988) The Gibbs method and Duhem's theorem - the quantitative relationships among P, T, chemical potential, phase composition and reaction progress in igneous and metamorphic systems. Contributions to Mineralogy and Petrology, v. 99, 249-256.
Best,
Matt
On Jul 20, 2013, at 1:24 AM, Jean-Luc Régnier wrote:
> Dear All,
>
> I got the opportunity to do a small application (.exe only for windows unfortunately, but source code for Python27) calculating the effective bulk composition after garnet fractionation. The program is based on the work of Evans* (2004) with some modifications and might be useful for people building pseudosections/P-T path from bulk rock analyses and garnet analyses.
> I would be happy to discuss with people working on this subject if any ?
> Best regards,
> Jean-Luc
>
> * Evans, T. P. (2004). A method for calculating effective bulk composition modification due to crystal fractionation in garnet bearing schist: implications for isopleth thermobarometry. Journal of Metamorphic Geology 22, 547–557.
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Dr. Matthew J. Kohn, University Distinguished Professor
Department of Geosciences, Boise State University
1910 University Dr.; MS1535
Boise, ID 83725-1535
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http://earth.boisestate.edu/mattkohn/
phone: (208)-426-2757 fax: (208)-426-4061
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