THE TECTONO-METALLOGENIC EVOLUTION OF THE ARABIAN SHIELD

The Arabian Shield comprises a group of diverse terranes, accreted during the Late Proterozoic. Their boundaries are suture zones characterised by tectonised ultramafic bodies aligned within distinct orogenic belts. The Asir, Hijaz and Midyan terranes consist of a series of Late Proterozoic immature island arcs and together form the western half of the Shield. In the east however, the Afif and Ar Rayn terranes have a continental affinity with the Afif terrane being much older, at least Early Proterozoic and possibly Archaean. Metallogeny within the Arabian Shield is also diverse and includes Cu-Ni and Cr mineralisation associated with Proterozoic oceanic crust or "ophiolite", arc-type volcanogenic base and precious metal deposits associated with formerly active plate margins, shear zone hosted mesothermal gold mineralisation related to accretionary and strike-slip tectonics as well as Sn-W-Ta-Mo-REE mineralisation associated with post-cratonisation alkali granite magmatism of Late Proterozic to Early Phanerozoic age. It is possible to trace a systematic evolution in metallogeny, both within each terrane and throughout the craton as a whole, as a function of crustal development and tectonics. Although the age range of rocks exposed in the Shield is from Early Proterozoic to Tertiary, all known styles of primary metallogeny are associated with its cratonisation in the Late Proterozoic.