Opening histories of fractures in sandstone
Published:January 01, 2004
S. E. Laubach, R. H. Lander, L. M. Bonnell, J. E. Olson, R. M. Reed, 2004. "Opening histories of fractures in sandstone", The Initiation, Propagation, and Arrest of Joints and Other Fractures, J. W. Cosgrove, T. Engelder
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High-resolution scanning electron microscope (SEM)-based cathodoluminescence images were used to reconstruct incremental fracture opening in regional opening-mode fractures in sandstone. Opening is recorded by crack–seal texture in isolated mineral bridges that span opening-mode fractures formed in sandstone at moderate-great depth (c. 1000–6000 m). We restored opening histories of nine representative fractures with apertures of millimetres in five sandstones from five sedimentary basins. Gaps created by fracture widening in 11 bridges range from less than 1 μm to more than 1 mm, but nearly all are less than 20 μm and most are less than 5 μm. These are the opening amounts that could be spanned by cement growth in these diagenetic environments. Our observations are the first evidence of opening amounts from mostly porous, opening-mode (joint-like) fractures formed in diagenetic environments. Patterns are consistent with a new structural diagenetic model of bridge growth that can use opening patterns to indicate rate of fracture opening as a function of time.
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The Initiation, Propagation, and Arrest of Joints and Other Fractures
This volume is a state of the art look at our understanding of joint development in the crust. Answers are provided for such questions as the mechanisms by which joints are initiated, the factors controlling the path they follow during the propagation process, and the processes responsible for the arrest of joints. Many of the answers to these questions can be inferred from the geometry of joint surface morphology and joint patterns. Joints are a record of the orientation of stress at the time of propagation and as such they are also useful records of ancient stress fields, regional and local. Because outcrop and subsurface views of joints are limited, statistical techniques are required to characterize joints and joint sets. Finally, joints are subject to post-propagation stresses that further localize deformation and are the focus for the development of new structures.