Shear and rotation behaviour on different scales

At the end of the first transient stage, strain compatibility within the mylonite is maintained by a combination of microshearing, dynamic recrystallization, and inter- and intracrystalline gliding. The symmetry of the c-axis cross girdle suggests that the basal glide planes are in a conjugate orientation with respect to the instantaneous stretching direction. The Sb- and Sc-oriented microshears are also symmetrically oriented with respect to this direction. Thus, both intergranular microshearing and intragranular gliding on the basal planes accommodate strain by allowing the material to elongate in the direction of greatest instantaneous stretching.

The consumption of grains less favorably oriented for intracrystalline gliding leads to an increase in the volume of grains whose basal planes are oriented subparallel to the SZB. Therefore, a  domainal microfabric develops during the second transient stage consisting of yellow and magenta domains. At this stage, grain boundaries and domain boundaries coincide, respectively,  with Sb and Sa microshears. Thus, sample elongation results from a close interaction of Sb-oriented microshears and basal gliding, whereas the Sa-oriented microshears accommodate the differences in the rate and amount of shear strain between the different domains.

At steady state, most of of the grains´ basal planes are oriented subparallel to the SZB. Closer examination of individual grains reveals that the c-axes of subgrains continuously rotate, and so accommodate different amounts of shear strain with different local strain rates. Consequently, microshears are required to maintain strain compatibility between the different subgrains and grain aggregates. As in the second transient stage, a combination of basal gliding subparallel to the SZB and shearing along the Sb-oriented microshears maintain compatibility in the direction of greatest instantaneous stretching, whereas the Sa-oriented microshears accommodate strain between the different domains.