Fabric stability in oblique convergence and divergence |
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| Institution: | 1. Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA;2. Department of Geology and Geophysics, Rice University, Houston, TX 77005, USA;1. Dipartimento di Matematica e Geoscienze, Università di Trieste, Italy;2. Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy;1. Department of Geological Sciences and Engineering, University of Nevada-Reno, NV, USA;2. School of Earth and Planetary Sciences, John de Laeter Centre, Curtin University, Western Australia, Australia;3. Department of Earth & Environmental Sciences, University of Minnesota-Twin Cities, MN, USA;1. Department of Applied Geology, The Institute for Geoscience Research (TIGeR), Curtin University, GPO Box U1987, Perth, WA 6845, Australia;2. School of the Earth Sciences and Resources, China University of Geosciences (Beijing), 29 Xueyuan Road, Beijing 100083, China;3. Tectonics, Resources and Exploration (TRaX), Department of Earth Sciences, University of Adelaide, SA 5005, Australia;1. School of Chemical and Physical Sciences, Victoria University of Wellington, Box 600, Wellington 6140, New Zealand;2. Department of Chemistry, University of Canterbury, Christchurch, New Zealand |
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| Abstract: | Forward modeling of transpression–transtension, assuming homogeneous strain and a direct relationship between finite strain axes and foliation–lineation in tectonites, investigates fields of stability of foliation and lineation orientations in oblique convergence and divergence. Vertical foliation–horizontal lineation (VF–HL) develop for angles of convergence–divergence between 0 and 20°. With increasing finite strain, this narrow window of stability is further reduced; lineation switches to vertical in transpression and foliation switches to horizontal in transtension. If a shear zone contains VF–HL, it either developed as a zone very close to pure wrenching, or recorded low finite strain. The stability of VF–HL at high strain and higher angles of convergence is enhanced by lateral extrusion of material along transpression zones. VF–HL may be stabilized in magmatic bodies that progressively intrude transtension zones, if the wrench component of deformation partitions within them. Alternatively, if these bodies are dike-like, cool fast, and do not record large deformation, they take up the extension component of transtension through anisotropic volume addition, leaving a larger component of wrench deformation in the country rocks; this effect stabilizes VF–HL effectively at low strain, but only marginally so at high strain. |
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