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Microstructure sections:

Complex growth microstructure in Bushveld aureole metapelite

Complex growth microstructure in Bushveld aureole metapelite: growing porphyroblasts pseudomorph the microstructure of the matrix they replace. allowing the detailed sequence of growth to be determined.

Microstructures and metamorphic reaction processes

The application of thermodynamic methods has revolutionised many areas of metamorphic petrology, such as the determination of pressures and temperatures of equilibration, and yet our understanding of the kinetics of metamorphic processes has lagged behind. For example, it is not known, in general, how far evolving metamorphic systems depart from chemical equilibrium, nor whether reactions proceed during brief episodes of rapid growth, or are slow, keeping pace with heat supply.

I developed an interest in these problems after working on the hornfelses associated with the Bushveld Complex in the 1980's, and developed a simple numerical model to study the interaction between nucleation and growth in metamorphic reactions and its implications for observable microstructure. In 1996 I began work again in this area with the help of graduate student Dan Lovegrove, who returned to the rocks in the field to constrain and test the modelling.

More recently, prompted by the common difficulty of reconciling the calculated equilibrium behaviour with the microstructural record in rocks, my focus has broadened to consider a wider range of processes responsible for the divergence between observation and calculation, including barriers to nucleation, sluggish dissolution of refractory phases, and evolution of the effective bulk composition by fractionation and other processes.

Here you will find (in reverse date order):

Background reading on nucleation and growth kinetics

An introduction to some of the concepts:

Yardley, B.W.D. (1989) Introduction to Metamorphic Petrology, chapter 6, Metamorphic Textures and Processes. Longman. (You can omit those parts that relate to deformation)

Barker, A. J. (1998) Introduction to Metamorphic Textures and Microstructures, Chapter 5, Crystal Nucleation and Growth. 2nd Edition, Stanley Thornes (Publishers) Ltd.

Some more advanced reading: