The geology of the Arabian-Nubian shield / Геология Аравийско-Нубийского щита

The Arabian–Nubian Shield (ANS) is a vast and exceptionally well-preserved expanse of crust and underlying sub-continental lithospheric mantle that was largely produced during the Neoproterozoic, with only restricted contribution from older lithospheric components, except in the extreme north-eastern part of the shield. With an exposed area of nearly 2 million km², and an additional 1 million km² buried beneath the great Cenozoic East African Rift System and its associated volcanic rocks, the shield represents one of the best-preserved Neoproterozoic orogenic belts on the planet and the largest preserved expanse of new Neoproterozoic lithosphere in Earth’s geological history. The ANS was formed between ca. 870 and 540 Ma and forms the northern part of the vast East African Orogen (EAO). Earlier Tonian juvenile crust is also found in Sudan, Madagascar, East Africa and Antarctica, which suggests that the Tonian–Cambrian ANS is really the continuum of subduction-accretion magmatism on the periphery of the Mesoproterozoic–Neoproterozoic African continents. The first period of complex tectonic history occurred between 870 and 640 Ma, which corresponds to the initiation of oceanic arcs and back-arcs followed by their accretion on top of each other within an oceanic tectonic environment or towards the peripheral margins of continents. This resulted in the formation of a series of juvenile Neoproterozoic tectonic terranes of various ages and an array of ophiolitic assemblages. The 640–540 Ma period subsequently witnessed the final continental amalgamation, with the collision with eastern continent including Neoproterozoic India. The ultimate development of post-collisional continental scale mega-shear zones linked to tectonic escape, and later the overprint of molassic basins and voluminous magmatism in the form of dike swarms, ultimately resulting in the emergence of the present appearance of the shield. <...>