The Structural Evolution of an Orthogneiss-fold Within the Reitzenhainer Rotgneisstruktur (Erzgebirge Mts., GDR)

The crystallographic preferred orientations of quartz in gneiss taken from different spots of a recumbent fold structure in the Erzgebirge Mts. (southern GDR) are studied by means of neutron time-of-flight diffraction. A single component texture has been found for all specimens, with quartz c-axes parallel to the tectonic a-direction. The variations in texture sharpness are related to different deformation conditions of the samples. A fabric rotation of 30° has been found from the limb to the crest of the fold on the basis of ($$) and ($$) pole figures. The basal pole figures of quartz derived from an ODF analysis compared well with optical U-stage measurements. The determined fabrics are discussed taking into account model calculations of experimentally deformed quartzites and geological informations.