Abstract

A model is developed to account for mineral recrystallization under directed stress resulting in a minimum Gibbs and a maximum Helmholtz free energy for equilibrium orientation. Correlations between calculated orientations, and observed preferred orientations are established for hornblende, mica, quartz, tourmaline, olivine and perhaps dolomite. Shear strain parallel to tectonic A is responsible for determining rock fabric but is a relatively unimportant strain in determining final mineral crystallization. It is suggested that uniform strain in a crystal is a requirement for equilibrium and grain size and orientation are influenced by uniform strain requirement; also indicated is the possibility that strain energy and thermodynamic equilibrium throughout a stressed system be used quantitatively to describe relative strain differences in different parts of the deformed system.

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