The tectonic framework of Mongolia and contiguous regions in the context of the crustal evolution of the Central Asian Orogenic Belt

摘要

The Central Asian Orogenic Belt (CAOB), or Altaides, one of the world's largest accretionary orogens, formed largely by the subduction arid accretion of juvenile material from the Neoproterozoic to the end-Palacozoic. Mongolia occupies a central position between key regions such as Kazakhstan, Gorny Altai-Sayan of Siberia, Trans-Baikalia, Inner Mongolia of China and the Chinese Altai. The earliest parts of the CAOB are situated in Siberia where Neoproterozoic island arcs accreted as a result of the subduction of a approx 1000 Ma ocean, a remnant of which is now preserved in the 1019 Ma Dunzhugar ophiolite in Eastern Sayan. Island arcs continued to accrete in what is now Kazakhstan and the Altai-Sayan regions of Siberia from the late Neoproterozoic to the Ordovician. The collision of Precambrian microcontinents in the late Devonian to early Carboniferous deformed arid re-oriented earlier arc-dominated terrains. Terminal collision of the Siberian and Kazakhstan continents in the late Carboniferous to Permian was responsible for ophiolite obduction, oblique strike-slip deformation, and interleaving by thrusting and transpression of earlier arcs with terrains detached from the margins of the two continents.