Röntgenographische Gefügeanalyse [mit dem Zählrohr-Texturgoniometer] von Quarzschiefern aus Zentral-Shikoku, Japan

Abstract

The petrofabrics of quartz in the quartz-schists of the Sambagawa metamorphic zone in central Shikoku, Japan, were analysed optically with an universal stage and by the X-ray method with a texture goniometer, for the grasp of the relation between metamorphic grade and quartz-orientation. The accumulation of quartz-c-axes increases and their positions are changed gradually in the ascending order of the metamorphic grade. In the zone of the glaucophane-schists facies, a prism-plane m (1010) of quartz lies always parallel to the fabric plane-(ac). In the zone of the epidote-amphibolite facies, the quartz-diagrams show a distinctive preferred orientation of poles of prism-planes a (1120) and m (lOlO), namely, am-girdle. At the part of the highest metamorphic grade the diagrams show almost nearly single one-crystal-fabrics through the positions of sub-planes of quartz. The mechanism of quartz-orientation was also discussed.