Structure and development of an anastomosing network of ductile shear zones

Carreras, Jordi; Czeck, Dyanna M.; Druguet, Elena; Hudleston, Peter J.

doi:10.1016/j.jsg.2010.03.013

Cited by 75 publications

(41 citation statements)

References 50 publications

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“…The critical creep case could occur on a network of mesoscale (cm to m) fractures connected through the BDT (Figure b). This type of structure is well described in ductile shear zone that experienced large amounts of strain and at the BDT [e.g., Mitra , ; Gapais et al ., ; Carreras et al ., ]. Initially the creep rate increases to 6 cm yr −1 and over 250 years decreases back to zero (jammed state).…”

Section: Timescales Of Slow Eventsmentioning

confidence: 99%

Creep events at the brittle ductile transition

Lavier

Bennett

Duddu

2013

Geochem Geophys Geosyst

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[1] We present an analytic formulation to model creep events at the transition between brittle behavior in the crust and viscous behavior in ductile shear zones. We assume that creep events at the brittle ductile transition (BDT) are triggered by slip on optimally oriented fractures or network of fractures filled with weak ductile material. These events are expressed as transient flow in ductile shear zones likely aided by the release of crustal fluids. We show that the creep in the shear zone can be modeled as the motion of a forced damped oscillator composed of a brittle viscoelastic crust, a ductile shear zone and a creeping zone of fractures at the BDT. The time scale of the events varies between seconds to thousands of years depending on the viscous, elastic and brittle-plastic properties of the fractured BDT, the shear zone and the crust. The nature of the events depends on the aspect ratio, of the shear zone thickness, H w to the length of the fractured zone, w. We find that thick shear zones with small fractures at the BDT are stiff and generate creep oscillations. Thin shear zones with well-connected fractures over a large width have very small stiffness and are well lubricated. They generate slow creep events or steady creep event. The former are similar to transient slip events and the latter to creep at the far field tectonic rates. The viscosity of the shear zone, w enhances lubrication if it is small and stiffness if it is large.

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Section: Timescales Of Slow Eventsmentioning

confidence: 99%

Creep events at the brittle ductile transition

Lavier

Bennett

Duddu

2013

Geochem Geophys Geosyst

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“…Detailed and quantitative studies have usually been limited to simple, straight planar shear zone segments [Passchier, 1990a[Passchier, , 1990b[Passchier, , 1998Grujic and Mancktelow, 1998;Piazolo et al, 2001;Schrank et al, 2008], whereas field work shows that in most cases the straight segments form part of a complex systems of kilometers-wide anastomosing and branching (The term ''branch'' is used for an active shear zone, which is connected through joining or splitting with an additional localized shear zone.) shear zones [Passchier et al, 1997;Faure et al, 2005;Archanjo, 2008;Carreras et al, 2010;Culshaw et al, 2011;Passchier and Platt, 2016]. Such anastomosing shear zone patterns can develop in different ways.…”

Section: Introductionmentioning

confidence: 99%

Development of branching brittle and ductile shear zones: A numerical study

Meyer

Kaus

Passchier

2017

Geochem Geophys Geosyst

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Continental collision zones are usually associated with large‐scale strike‐slip shear zones. In most cases, these shear zones are complex and consist of multiple strands, varying in width, length, and total displacement. Here we present 2‐D numerical models to simulate the formation of such shear zones at different depth levels within the crust, under either brittle (frictional/plastic) or ductile conditions. Localization of shear zones is initiated by a material contrast (heterogeneity) of the material parameters. We systematically test the rate of strain weakening in brittle and in ductile regimes to understand its influence on the development of shear zone networks. Our simulations suggest that the development of antithetic faults in a brittle shear zone system is closely linked to a decrease in the angle of friction during deformation. In general, variation of the strain weakening also has a significant influence on ductile shear zones. Numerical results show that the geometry and thickness of the localized high strain zone are especially affected by weakening mechanisms during deformation. Furthermore, the interconnection and interaction of the shear strands lead to a more complex kinematic pattern, which lead to a local change in the maximum principal stress axis. These interaction of shear strands may explain the occurrence of shear‐related structures (e.g., folds) or differing characteristics of shear zones, such as the thickness of shear zones or the orientation of the faults to the stress field, which are consistent with field observations.

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“…It is notable that when seen in planview the transpressional features are characteristic of an anastomosing pattern ( Fig. 3a; Ramsay, 1980;Mitra, 1998;Carreras et al, 2010). …”

Section: Central Asiamentioning

confidence: 96%

A challenge to the concept of slip-lines in extrusion tectonics

Zheng

Wang

Zhang

et al. 2011

Geoscience Frontiers

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Wide-open V-shaped conjugate strike-slip faults in Asia are typically related to extrusion tectonics. However, the tectonic model based on the slip-line theory of plasticity has some critical problems associated with it. The conjugate sets of slip-lines in plane deformation, according to the theory of plasticity should be normal to each another but, in reality, the angles between the conjugate strike-slip faults, which are regarded as slip-lines in extrusion tectonics in the eastern Mediterranean, Tibet-middle Asia, China and the Indochina Peninsular regions, are always more than 90 (on average w110 ) in the direction of contraction. Another problem is that the slip-line theory fails to explain how, in some cases, e.g., in the Anatolian area in the eastern Mediterranean, the extrusion rate is much higher than the indent rate. The two major problems are easy to solve in terms of the Maximum-Effective-Moment (MEM) Criterion that predicts that orientations of the shear zones are theoretically at an angle of 54.7 and practically at angles of 55 AE10 with the s 1 -or contractional direction. The orientations of the strike-slip faults that accommodate extrusion tectonics are, therefore, fundamentally controlled by the MEM Criterion. When extrusion is along the MEM-orientations, the extruding rate is normally higher than the indenting rate. ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

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Structure and development of an anastomosing network of ductile shear zones

Cited by 75 publications

References 50 publications

Creep events at the brittle ductile transition

Creep events at the brittle ductile transition

Development of branching brittle and ductile shear zones: A numerical study

A challenge to the concept of slip-lines in extrusion tectonics

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