Fracture and vein patterns as indicators of deformation history: a numerical study
Published:January 01, 2005
Daniel Koehn, Jochen Arnold, Cees W. Passchier, 2005. "Fracture and vein patterns as indicators of deformation history: a numerical study", Deformation Mechanisms, Rheology and Tectonics: from Minerals to the Lithosphere, D. Gapais, J. P. Brun, P. R. Cobbold
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Fracture and vein patterns in the brittle crust of the Earth contain information on the stress and strain field during deformation. Natural examples of fracture and vein patterns can have complex geometries including combinations of extension and conjugate shear fractures. Examples are conjugate joint systems that are oriented with a small angle to the principal stress axis and veins that show an oblique opening direction. We developed a discrete numerical model within the modelling environment ‘Elle’ to study the progressive development of fractures in two dimensions. Results show that pure shear deformation alone can produce complex patterns with combinations of extension and shear fractures. These patterns change in geometry and spacing depending on the Young's modulus of the deforming aggregate and the initial noise in the system. A complex deformation history, including primary uniaxial loading of the aggregate that is followed by tectonic strain, leads to conjugate shear fractures. During progressive deformation these conjugate shear fractures may accommodate extensional strain or may be followed by a secondary set of extension fractures. The numerical patterns are consistent with joint, fault and vein geometries found in natural examples. The study suggests that fracture patterns can record complex deformation histories that include primary uniaxial loading due to an overlying rock sequence followed by tectonic strain.
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Deformation Mechanisms, Rheology and Tectonics: from Minerals to the Lithosphere
This book consists of 18 papers on deformation mechanisms, theology and tectonics. The main approaches include experimental rock deformation, microstructural analysis, field structural studies, analogue and numerical modelling. New results on various topics are presented, ranging from brittle to ductile deformation and grain-scale to lithosphere-scale mechanisms.
The volume will be of interest to academic and industrial researchers in the fields of structural geology, interactions between metamorphism, fluids and deformation, and large-scale tectonic processes.