0000000000171110
AUTHOR
R. A. J. Trouw
showing 2 related works from this author
Flow and Deformation
1998
A hunter who investigates tracks in muddy ground near a waterhole may be able to reconstruct which animals arrived last, but older tracks will be partly erased or modified. A geologist faces similar problems to reconstruct the changes in shape that a volume of rock underwent in the course of geological time, since the end products, the rocks that are visible in outcrop, are the only direct data source. In many cases it is nevertheless possible to reconstruct at least part of the tectonic history of a rock from this final fabric. This chapter treats the change in shape of rocks and the methods that can be used to investigate and describe this change in shape. This is the field of kinematics,…
Dilatation Sites: Fibrous Veins, Strain Shadows, Strain Fringes and Boudins
1998
Many deformed rocks contain sites with a deviant mineralogy and fabric, interpreted as an effect of rearrangement of material by local dilatation and precipitation during deformation. Such ‘dilatation sites’ can be isolated and elongate (veins), flanking rigid objects (strain shadows) or occur in the neck of boudinaged layers or elongate crystals (Fig. 6.1). Strain shadows are also referred to in the literature as pressure shadows. Most veins and many strain shadows and boudin necks have sharp contacts with the wall rock and may form by precipitation of material from an aqueous solution in a fracture, as outlined below. Such sites are usually filled with polycrystalline material which may b…