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On the origin of shear-band network patterns in ductile shear zones
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2022Ductile yielding of rocks and similar solids localize shear zones, which often show complex internal structures due to the networking of their secondary shear bands. Combining observations from naturally deformed rocks and numerical modelling, this study addresses the following crucial question: What dictates the internal shear bands to network during ...
Nandan Roy +3 more
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What controls the width of ductile shear zones?
Tectonophysics, 2021Abstract It is widely recognized that major brittle faults in the upper crust transition downwards into ductile shear zones that then widen with depth. However, the controls on shear zone width at any specific depth, and the mechanisms that may cause the width to change over time, are less well understood.
T.K. Cawood, J.P. Platt
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On mylonites in ductile shear zones
Journal of Structural Geology, 1980Abstract 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.
S.H. White +4 more
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Tectonophysics, 1991
Abstract The geometric character of conjugate ductile shear zones has been defined from the structures developed in a undeformed granitoid corresponding to an homogeneous and isotropic material. In the plane perpendicular to the intersection line of conjugate zones (plane σ 1 σ 3 ) one notes that: (1) the principal direction of finite shortening ...
C. Lamouroux, J. Ingles, P. Debat
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Abstract The geometric character of conjugate ductile shear zones has been defined from the structures developed in a undeformed granitoid corresponding to an homogeneous and isotropic material. In the plane perpendicular to the intersection line of conjugate zones (plane σ 1 σ 3 ) one notes that: (1) the principal direction of finite shortening ...
C. Lamouroux, J. Ingles, P. Debat
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Porosity network of a ductile shear zone
Journal of Structural Geology, 1995Abstract The permeability of ductile shear zones is assumed to be significantly higher than that of surrounding undeformed rocks, although lower than that of fracture systems. This assumption, which results indirectly from geochemical mass balance calculations, is checked in this paper by the tomography of the porosity network in a metre-wide ...
Géraud, Yves +2 more
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How ductile are ductile shear zones?
Geology, 2006Three premises of ductile deformation in the middle and lower crust are widely accepted: (1) rocks flow with power-law viscous rheology, (2) localization in ductile shear zones involves strain softening, and (3) fluid flows into and is channelized within ductile shear zones.
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Terminations of ductile shear zones
Tectonophysics, 1986Abstract We propose a plane strain model for ductile shear zone terminations in rocks that otherwise record no visible shear strain. This model may explain the strain distribution patterns in naturally occurring terminations of shear zone which show, in the XZ plane of finite strain, (1) a decrease in the area of finite strain and in strain ...
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Progressive development of structures in a ductile shear zone
Journal of Structural Geology, 1987Abstract In the Singhbhum Shear Zone of eastern India successive generations of folds grew in response to a progressive ductile shearing. During this deformation a mylonitic foliation was initiated and was repeatedly transposed. The majority of fold hinges were formed in an arcuate manner at low angles to the Y-axis in an E-W trending subhorizontal ...
S.K Ghosh, null Sudipta Sengupta
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Secondary cleavages in ductile shear zones
Journal of Structural Geology, 1984Abstract Secondary cleavages developed at late stages in ductile shear zones show several features that are inconsistent with progressive simple shear in the zone. These are: the orientation of a single secondary cleavage oblique to the shear zone boundaries; conjugate sets with opposite senses of shear, and multiple sets with the same sense of shear.
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A dynamic model for aseismic ductile shear zones
Earth and Planetary Science Letters, 1979Abstract A model for the dynamics of aseismic strike-slip shear zones is proposed under conditions of constant rate out-side the zone and with an almost perfectly rigid plastic rheology for the rock. It is shown that a necessary condition for the activation of the shear zone is the existence of an initial strength defect.
J.P. Poirier, J.L. Bouchez, J.J. Jonas
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