Late Precambrian subduction and collision in the Al Amar—Idsas region, Arabian Shield, Kingdom of Saudi Arabia

Recent work on outer arcs and collision belts provides for the first time a possible model for evolution of part of the Arabian Shield. The thick volcanic, volcaniclastic and sedimentary succession of the Proterozoic Halaban Group in the east of the Shield is intruded by synto late tectonic plutons and resembles Cenozoic subduction-related magmatic areas. West of the Halaban Group, and separated from it by a major east-dipping thrust with associated ultrabasic rocks and carbonates, are folded chlorite—sericite metasediments of the Abt Schists, comparable to Cenozoic outer arc successions. West of and beneath the Abt Schists calcareous and arenaceous metasediments of the Ar-Ridaniyah Formation are analogous to Mesozoic—Cenozoic continental margin shelf facies of the subducting plate. Eastward subduction with magmatism (Halaban Group) and tectonic emplacement of ocean-floor sediments (Abt Schists) was followed by continental collision and eastward underthrusting by the Ar-Ridaniyah Group and cratonized central part of the Shield. Collision-related post-tectonic granites were emplaced during and following the collision.