DELTA STRUCTURE OF TRAILS
The development of the delta-type of Porphyroclast tails can be explained by their rotations. The development of the delta-type of tail is favoured when the porphyroclast is equant or has a small aspect ratio. When the finite strain is large and when the rate of dynamic recrystallization at the periphery of the porphyroclast is small in comparison with the rate of rotation. as mentioned earlier the material of the porphyroclast tail is derived from the porphyroclast itself. With progressive deformation the size of the porphyroclast is reduced while the fine-grained recrystallized material from the periphery is drawn out in the direction of stretching in the matrix.