Tectonic processes in the Southern and Middle Urals: an overview

Abstract The tectonic evolution of the Uralide orogen began during the Late Palaeozoic as the continental margin of Baltica entered an east-dipping (today9s coordinates) subduction zone beneath the Magnitogorsk and Tagil island arcs. The subsequent arc-continent collision resulted in the development and emplacement of an accretionary complex over the continental margin, the development and deformation of a foreland basin, and the extrusion of high-pressure rocks along the arc-continent suture. There is mounting evidence that, at about the same time as arc-continent collision was occurring along this margin of Baltica, eastward-directed subcontinental subduction of the Uralian oceanic crust was also taking place beneath the Kazakhstan plate. This subcontinental subduction is thought to have resulted in the formation of a continental volcanic arc. The final closure of the Uralian ocean basin and the start of collision between the Baltica and Kazakhstan plates occurred during the Late Carboniferous. This continent-continent collision resulted in development of the Late Carboniferous to Early Triassic western foreland fold and thrust belt and foreland basin of the Uralides. The foreland fold and thrust belt displays a large amount of basement involvement, extensive reactivation of pre-existing faults, and a small amount of shortening. At the same time, widespread strike-slip faulting accompanied by melt generation and granitoid emplacement took place in the interior part of the Uralides, leading to the transfer of material laterally along the strike of the orogen. The final crustal structure of the Uralides that resulted from the combination of all of these tectonic events is bivergent, with a crustal root reaching c. 53 km depth.