Abstract: In this contribution, shear zones are treated as zones of inhomogeneous deformation in which strain softening has occurred. The mylonites which form in ductile shear zones are the softened medium. The development of mylonite microstructures and fabrics are discussed from this point of view. Seven possible softening processes are discussed. They are the advent of superplasticity, geometrical softening, continual recrystallization, reaction softening, chemical softening, pore fluid effects and shear heating. Attention is also given to the brittle deformation of hard minerals in a soft ductile matrix. It is concluded that these fracture because of localized stress concentrations and that their microstructures give no information on deformation in the matrix. An oblique shear band foliation may develop in mylonites as shear strains continue to increase and may destroy the earlier-formed mylonite foliation. It is thought that the foliation may indicate hardening of the soft mylonite.
Publication Year: 1980
Publication Date: 1980-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 692
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