Abstract
The Ajjaj shear zone is a part of the regional-scale Quazaz-Ajjaj-Hamadat (QAH) shear zone that controls the structure of the northwestern Arabian Shield. The finite strain, and structural and tectonic evolution of the Ajjaj shear zone are estimated by fieldwork, analyzing its deformation history, and strain analysis. The Rf/phi and Fry techniques were used to measure the shape of quartz, plagioclase, potassium-feldspar, biotite, and hornblende crystals and to demonstrate the strain analysis for the felsic and mafic minerals separately. The results of finite-strain analysis illustrate that the long axes (X) for finite strain direction exhibits clustering along a NNW-SSE trend with varying plunge. The short axes (Z) are subhorizontal and associated with subvertical foliation. All data reveal oblate strain symmetry, which indicates a flattened shape. The strain magnitude (E (sub t) ) suggests that no relationship exists between nappe contacts. There is no volume change for different mineral grains with the accumulation of finite strain in the Ajjaj area. Furthermore, the foliation is parallel to the thrusting and illustrated mainly the same attitudes of tectonic contacts with the overlying nappes. It is concluded that the Ajjaj shear zone supports NW-trending sinistral shear sense and resulted from simple-shear deformation for nappes.