Geometrical features of shear bands in foliated rocks

• Enrique Gómez Rivas ^[1] ; Elena Druguet ^[1] ; Jordi Carreras ^[1]
  1. [1] Universitat Autònoma de Barcelona

     Universitat Autònoma de Barcelona

     Barcelona, España

     
• Localización: Geotemas (Madrid), ISSN 1576-5172, Nº. 6, 3, 2004 (Ejemplar dedicado a: IV Congreso Geológico de España (Zaragoza, 12-15 julio, 2004)), págs. 57-60
• Idioma: inglés
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• Resumen

  • In anisotropic rocks, shear bands form when layering or foliation is subjected to extension.

    Although shear bands are frequently used as kinematic indicators, some aspects regarding their origin and development are still poorly understood. Moreover, there is not yet a unified terminology for these structures. There are different geometries of shear bands in foliated or multilayered rocks depending on rheology and kinematics, ranging from brittle fractures to ductile shears, and they may be arranged in one or two sets. Shear bands are related to other structures, like folds or shearfracture boudins. To understand how these structures develop it is essential to perform a exhaustive geometrical study. Frequency, size and sharpness of shear bands and angular relationship between shear bands and foliation planes are mainly controlled by rheology (mechanical anisotropy, ductility and competence contrast). The development of one or two sets of shear bands depends on the relative orientation o f ISA regarding to the anisotropy planes.