Al Hajar Mountains
Eclogite-facies HP to UHP metamorphic rocks are produced by subduction of crustal rocks to the lower crust to mantle depths for extreme metamorphism at the low thermal gradients of less than 10°C/km. All of these rocks occur at convergent plate margins, and UHP rocks only occur in collisional orogens. There is general agreement that most well-exposed and well-studied UHP terrains were produced by the burial of crustal rocks to mantle depths of &gt;80 km during subduction. Continental margin subduction is well documented in a number of collisional orogens, such as the Dabie orogen where South China Block passive-margin sedimentary and volcanic sequences are preserved, in the Arabian continental margin beneath the Samail ophiolite (in the Al Hajar Mountains, Oman), and in the Australian margin presently subducting beneath the Banda Arc. Sediment subduction occurs beneath volcanoplutonic arcs around the world and is recognized in the compositions of arc lavas. Continental subduction may be underway beneath the Pamir. Subduction erosion also occurs beneath volcanoplutonic arcs around the world, carrying continental rocks to mantle depths at least locally.