Results 261 to 270 of about 49,686 (306)

Progressive refolding in ductile shear zones

Journal of Structural Geology, 1983
Abstract The foliation formed in a ductile shear zone can become folded by continuing shear in the zone without the foliation having to enter the shortening sector of the flow field. If the foliation lies parallel to the shear plane, infinitesimal variations in the rate of shear strain cause compensating rotations that may amplify into folds.
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Strain within ductile shear zones

Tectonophysics, 1976
Abstract The intensity of strain has been measured from the change in shape of clusters of mafic and felsic minerals within a ductile shear zone of short finite length from Botswana and a much longer planar shear zone from North Uist, Scotland. The strain measurements from North Uist have been supported by measurements of the anisotropy of magnetic ...
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Transient discontinuities in ductile shear zones

Journal of Structural Geology, 1980
Abstract Earthquake fault ruptures sometimes extend to deep crustal levels and beyond, where moderate- to high-grade metamorphic conditions must prevail in mylonitic shear zones. Evidence for such transient loss of continuity in mylonite belts tends to be obliterated by continued aseismic shearing and accompanying metamorphic processes, but in parts ...
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Shear Senses and Viscous Dissipation of Layered Ductile Simple Shear Zones

Pure and Applied Geophysics, 2015
Velocity profiles and shear heat profiles for inclined, layered Newtonian simple shear zones are considered. Reverse fault-like simple shear of the boundaries and upward net pressure gradient act together in such shear zones. As the velocity of the boundary increases, the point of highest velocity shifts from the lower layer of less viscosity into the ...
MULCHRONE, KF, MUKHERJEE, S
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Nucleation of ductile shear zones on dilatant fractures

Geology, 1986
Small shear zones in granitic rocks of the Sierra Nevada, California, and near Roses (Rosas), northeast Spain, display features which indicate that dilatant fracturing preceded the localization of ductile shear deformation. Many zones have sharp, nearly planar boundaries between their highly deformed interiors and the undeformed wall rock.
Paul Segall, Carol Simpson
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Ductile instability — Shentangyu ductile shear zone and tremolite glass in Huairou, Beijing

Physics and Chemistry of the Earth, 1990
Abstract This report discusses the phenomenon of brittle-ductile transition at the same depth owing to the changing strain rate according to the sheath folds and accompanying glassy substances found in the Shentangy ductile shear zone. Deformation stages are identified, and also mineral textures, structural forms of rocks and material compositions ...
null Shao Ji'an, null Fu Yingqi, null Zang Qijia, null Wang Yufang   +3 more
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Fabric development in brittle-to-ductile shear zones

pure and applied geophysics, 1986
Brittle-to-ductile shear zones from two separate geological settings are shown to have nucleated on zones of predominantly brittle deformation. The shear zones are not simply foliated cataclasites, since they contain abundant evidence of dynamic recrystallization of constituent minerals.
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Review on symmetric structures in ductile shear zones

International Journal of Earth Sciences, 2016
Symmetric structures in ductile shear zones range widely in shapes and geneses. Matrix rheology, its flow pattern, its competency contrast with the clast, degree of slip of the clast, shear intensity and its variation across shear zone and deformation temperature, and degree of confinement of clast in shear zones affects (independently) the degree of ...
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An apparatus to experimentally model the dynamics of ductile shear zones

Tectonophysics, 1996
Abstract We present a ring-shear apparatus designed to deform soft, ductile rock analogues to arbitraily high shear strains in simple shear, in experiments attempting to model processes that occur in natural ductile shear zones. The sintered specimen is deformed between two unsupported cylinders by two rotating grips, under a normal and shear stress ...
Paul D. Bons, Janos L. Urai
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Crustal-scale ductile shear zones in four dimensions

2021
Crustal-scale fault zones accommodate a significant portion of the relative motion between Earth?s tectonic plates, and are both a source of major earthquake hazard, and vital pathways for the mineralizing fluids that form several types of ore deposits.
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