Petrology and kinematic vorticity constraints of the Al Amar region, Northern Ar-Rayn terrane, Eastern Arabian shield, Saudi Arabia

Abstract

The Neoproterozoic basement rocks in Ar Rayn terrane set as parts in the Eastern Arabian Shield. It focus the petrological and kinematic vorticity for high deformed volcanic and granitoids rocks in the Al-Amar locality. The volcanic rocks divide into two main series, the eastern sequence cycle represents dacite, rhyodacite, rhyolite and ignimbrites, and the western sequence cycle characterizes andesite and pyroclastics. Furthermore, the granitoids rocks content monzodiorite, tonalite, granodiorite and alkali-feldspar granite. For assessing the proportions of pure and simple shear contributions in penetrative deformed rocks, the kinematic vorticity number (Wm) to the mean appreciation by applying porphyroclast, rotating in a flowing matrix is crucial. In the Ar Rayn terrane of Arabian shield, kinematic vorticity numbers for high deformed metavolcanics and granitoids gneisses vary from 0.4 to 0.6. The deformation in the studied area varied from simple shear, according to vorticity and strain studies. Nappe stacking getting ready during the thrusting activity only through the Al Amar –Idsas fault, according to the results, most likely due to brittle imbrication. A penetrative sub-horizontal foliation formed sub-parallel to the nappe contacts with the beneath laying nappes, showing that the ductile strain was superimposed on the construction of the nappe under high pressure. The Ar Rayn terranewas created sub-horizontal foliation by the buildup of ductile strain during under plating, which was induced by a vertical shortening component. This foliation was formed in the majority of cases during the thrusting nappes upon each other, implying that nappe stacking was related to vertical shortening due to a massive scale by the active Al Amar –Ideas fault.