Strain patterns of pluton emplacement in a crust undergoing non-coaxial deformation,Sierra Morena,Southern Spain

This paper investigates the problem of interference between regional and local strain fields, the latter corresponding to a pluton ballooning. Natural examples from the Sierra Morena (Southern Spain) are described. Two distinct patterns have been recognised, according to whether transcurrent motions or thrusting motions predominate in the regional deformation. The map of foliation trajectories shows typical features such as triple points and geometric continuity between pluton internal fabric and country rock cleavage even when these are oblique to the contact.A simple mathematical model of interference between ballooning and simple shear is presented. In this model, the ballooning may be circular or elliptical. The model is used to predict the position of triple points, patterns of principal trajectories and variations of finite strain. A comparison is made with plutons from the Sierra Morena.