Crack-seal patterns: records of uncorrelated stress release variations in crustal rocks
Published:January 01, 2005
François Renard, Muriel Andréani, Anne-Marie Boullier, Pierre Labaume, 2005. "Crack-seal patterns: records of uncorrelated stress release variations in crustal rocks", Deformation Mechanisms, Rheology and Tectonics: from Minerals to the Lithosphere, D. Gapais, J. P. Brun, P. R. Cobbold
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Statistical properties of crack-seal veins are investigated with a view to assessing stress release fluctuations in crustal rocks. Crack-seal patterns correspond to sets of successive parallel fractures that are assumed to have propagated by a subcritical crack mechanism in the presence of a reactive fluid. They represent a time-sequence record of an aseismic and anelastic process of rock deformation. The statistical characteristics of several crack-seal patterns containing several hundreds of successive cracks have been studied. Samples were collected in three different areas, gold-bearing quartz veins from Abitibi in Canada, serpentine veins from the San Andreas system in California and calcite veins from the Apennine Mountains in Italy. Digitized pictures acquired from thin sections allow accurate measurement of crack-seal growth increments. All the samples show the same statistical behaviour regardless of their geological origin. The crack-seal statistical properties are described by an exponential distribution with a characteristic length scale and do not show any spatial correlation. They differ from other fracture patterns, such as earthquake data, which exhibit power-law correlations (Gutenberg-Richter relationship). Crack-seal series represent a natural fossil record of stress release variations (less than 50 bars) in the crust that show a characteristic length scale, associated with the resistance of rock to effective tension, and no correlation in time.
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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.