Abstract

Means recently introduced the concept of strain-insensitive foliation. For strain-insensitive foliation to form in mono-mineralic aggregates, foliation-forming processes must be balanced by foliation-destroying processes, e.g., grain rotation and dynamic recrystallization. In polyphase aggregates a further process is required to disperse monomineralic polycrystalline aggregates of the rock-forming phases in order to eliminate the strain sensitivity of the resultant foliation.Dispersal of silicate phases in amphibolite and granulite facies mylonitic bands suggests that destruction of monomineralic polycrystalline aggregates may be a diffusion process, driven by a reduction of grain boundary energy of the aggregate where diffusion coefficients are high and kinetic barriers to diffusion are low. Such conditions may pertain in high-temperature shear zones and can result in steady-state foliations.

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