SHEAR ZONES, LOZENGE STRUCTURE IN
Ductile shear zones often anastomose around lenses of less deformed country rock. These lenses may range from the microscopic scale to the scale of a map. Map-scale lenses bordered by shear zones have been reported by Coward (1976), for example, from Rhodesia and by Bell ( 1978a) from the Woodroffe thrust in Australia. In the mesoscopic scale the patterns of anastomosing shear zones are best seen where the country rock has not yet been mylonitized. Such mesoscopic scale shear zones (or shear bands), ranging in width from a few millimeters to a few centimeters have been reported by several authors from weakly deformed granite terrains (e.g. Berthe el al. 1979. Simpson 1983. Choukroune & Gapais 1983. Gapais et at. 1987). With progressive mylonitization. however. the pods of unmylonitized country rock become fewer in number. The photograph to tne left and figure underneath (from the photograph) are reproduced from Gapais(1987. To the right are undeformed lenses or lozenges from Tigoda shear zone in the Central Indian Bundelkhand batholith.