What factors control the growth and development of C-bands in ductile shear zones.

What is it about?

Ductile materials undergoing shear deformation are characterized by the presence of variedly oriented shear bands, which are narrow zones of significant shear strain localization. Shear band development is a universal geodynamic phenomenon, which influences a wide range of natural processes like earthquakes, landslides, subduction zone dynamics. Studies on shear band formation provide the requisite clues on the failure mechanisms of ductile materials, a topic of great importance for predicting the behaviour of earth materials under extreme conditions. This paper is concerned with the factors determining the orientation of shear bands in natural ductile shear zones. The bands occur in two significant orientations, one at low-angle and the other parallel to the direction of applied shear. We address the long-standing question: Under what conditions do shear bands localize parallel to the bulk shear direction in shear deformations? We combine field observations, analogue experiments and numerical simulations to constrain the geometrical and rheological conditions of two principal modes of shear band growth. Our results suggest that ductile shear zones will preferentially enhance the development of shear-parallel bands over low-angle shear bands. A mathematical model is developed to predict the shear band orientation with respect to the direction of applied shear.

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Photo by Dan Meyers on Unsplash

Photo by Dan Meyers on Unsplash

Why is it important?

Although natural ductle shear zones exhibit proliferous growth of shear parallel C-bands, laboratory experiments intersetingly fail to produce such C-bands. This article tries to shed some light on this paradoxical nature of C-bands and tries to address the conditions for the development of such bands in natural ductile shear zones.

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