NATURAL ROTATED INCLUSIONS IN NONIDEAL SHEAR

Kinematic analysis of rotated winged inclusions is often couched in terms of ideal simple shear, with reference to a specific model based upon porphyroclasts of circular section. However, many natural winged inclusions are not porphyroclasts; commonly their geometries, as well as the orientation distribution of the inclusions themselves, reflect the non-ideal nature of the shearing deformation during which they formed. "Stair-stepped" sigma-shaped geometries may reflect the immaturity of a structure developed in non-ideal shear, or a mature structure developed in ideal simple shear. "Stair-stepped" delta-shaped geometries indicate that deformation approximated to ideal simple shear. "In-plane" (delta-shaped) geometries and skewed inclusion orientation distributions are indicators of non-ideal shear. © 1990.