Fatima suture: A new amalgamation zone in the western Arabian Shield, Saudi Arabia

Abstract

We describe a new amalgamation zone between Jiddah and Asir juvenile arc terranes in the western Arabian Shield. Ophiolitic rocks in this zone were deformed by a NE-SW oriented belt of opposite-verging overturned folds and thrust faults, whereas two granitic complexes intruded mainly through its axial uplift. Chemical characteristics of these rocks indicate that they formed in an arc suprasubduction zone setting. The amalgamation between Jiddah and Asir terranes is explained mainly in terms of two events followed by two more events related to convergence between eastern and western Arabian superterranes. NW-SE shortenings and dextral transpression of the first three events induced more structural elements and tectonic fabrics than those developed during the youngest shortening event. Tectonic fabrics differentiate between the stress orientations during the oldest deformation events. Variations in attitudes and shear senses throughout these structural and tectonic elements support strain partitioning. Deformation related to assembly of the Jiddah and Asir terranes started during ophiolite emplacement at 812Ma and ended before the deposition of the post-amalgamation Fatima basin. A northwestward shortening inverted this basin and developed NW-verging thrust faults and folds. Tectonic evolution of Fatima suture zone is correlated with the major tectonic settings of the Arabian Shield.