The use of shear zones and related structures as kinematic indicators: a review
Published:January 01, 2007
J. W. Cosgrove, 2007. "The use of shear zones and related structures as kinematic indicators: a review", Deformation of the Continental Crust: The Legacy of Mike Coward, A. C. Ries, R. W. H. Butler, R. H. Graham
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Shear zones (i.e. locally developed planar zones of ductile deformation that contain a tectonically induced fabric) are one of the most commonly used kinematic indicators (i.e. asymmetric structures that can be used to determine the sense of movement and the orientation of the stress field operating at the time of their formation). This is because of the abundant occurrence of these structures, and the assumption that there is a unique relationship between them and their causative stress field. However, there is a range of structures that, when viewed in two dimensions on an outcrop surface, display the geometry of shear zones but are formed in a variety of different ways and are oriented at various angles to the maximum principal compression. These include shear zones that form at angles between 25° and 45° to σ1 and that have the same relationship to σ1 as brittle shear fractures, shear zones linked to the deformation of anisotropic materials that form at angles between 45° and almost 90° to σ1, and structures with the geometry of a shear zone that can be inclined at angles between c. 10° and 80° to σ1 and that appear on certain sections though folded mineral fabrics. Unless the mechanisms of formation of these structures are understood, there is a strong possibility that their kinematic implications will be misinterpreted.
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Deformation of the Continental Crust: The Legacy of Mike Coward
This Special Publication, in memory and celebration of the work of Professor Mike Coward, is about the deformation of the continental lithosphere. The collected papers discuss geometry, structural principles, processes and problems in a wide range of tectonic settings and thereby reflect the breadth of Coward's interests. They encompass the evolution of Precambrian basement gneiss terrains, the geometry and evolution of thrust systems, basement involvement and structural inheritance in basins, syn-orogenic extension, salt tectonics, the implication of structural evolution on hydrocarbon prospectivity and structural controls on mineralization. Examples are drawn from the Lewisian and Moine Thrust Belt of NW Scotland, the Italian Apennines, NW Himalayas, the Cyclades, Oman, Zagros Mountains, Colombian Cordillera, Carpathians, North Sea, offshore Brazil, regional studies of the Irumide Belt (central Africa), Taurus Mountains (Turkey), greater South America, and from the Witwatersrand Basin of South Africa and the Antler Orogeny of SW USA.