The Origin of Crossed-Girdle Orientations of Optic Axes in Deformed Quartzites

Abstract

In the narrow metamorphic aureole of the Papoose Flat granitic pluton, Inyo Mountains, California, progressive flattening of stratified sedimentary rocks is observed; it is accompanied by recrystallization and development of foliation, lineation, and preferred orientation of minerals. The field and petrographic evidence indicate that these phenomena occurred concomitantly during a single episode of deformation and metamorphism associated with the emplacement of the pluton into previously unmetamorphosed rocks. The type of strain in the rocks is reflected in distortion of fossils and well-developed boudins. Preferred orientation in recrystallized quartzites is shown to be related to this episode, and the purpose of the paper is to correlate the preferred orientations with the strain and stress insofar as they are specified by the structures noted. The quartz axes are typically oriented in two nearly perpendicular planes that are symmetrically inclined to the foliation and intersect in the foliation perpend...