Stress-strain analysis and its tectonic implications for the Fatima suture zone, western Arabian Shield, Saudi Arabia

Abstract

The Fatima suture zone (FSZ) consists of highly thrusted and folded mafic, ultramafic and volcanic-sedimentary rocks and is bounded by granitic rocks. This study addresses the kinematics and deformation types of the FSZ using brittle and ductile tectonic fabrics for paleostress and paleostrain constructions, modes of fault initiation and reactivation and establishment of the Neoproterozoic tectonic sequence. The results show that the study area is characterized by five tectonic events that differ in time, location, and regime. The first tectonic event (D1) preceded FSZ development and was followed by two tectonic events (D2 and D3) that significantly affected rock deformations and were related mainly to FSZ formation. Progressive changes from transpressional to transtensional regimes are attributed to the divergent movements that occurred between the subducted Asir and Jiddah tectonic terranes on either side of the FSZ. Post-FSZ tectonic events (D4 and DT) occurred during the late development stage of the Arabian Shield and were not strong enough to develop prominent deformations. During tectonic deformation in the FSZ and its environs, faults initially developed with orientations and slip types compatible with the prevailing stress parameters. The superposed tectonic regimes inherited new faults and reactivated pre-existing faults. The formation of new slips on the reactivated fault planes depended on the stress parameters and fault strikes without changing their initial orientations. The slip types and orientations of the new faults reflected the stress regime. The rotation of fault planes during ductile deformation inside the FSZ has been proven, whereas brittle deformation at its shoulders has occurred without fault rotation.