HR: 14:10h
AN: GP13B-03 INVITED     [Abstracts]
TI: Tectonics of the Altaids and Its Global Implication
AU: * Sengor, A
EM: sengor@itu.edu.tr
AF: Istanbul Technical University, ITU Maden Fakultesi, Jeoloji Bolumu, Ayazaga, Istanbul, 34469 Turkey
AU: Natal'in, B A
EM: natalin@itu.edu.tr
AF: Istanbul Technical University, ITU Maden Fakultesi, Jeoloji Bolumu, Ayazaga, Istanbul, 34469 Turkey
AB: The Altaids are the orogenic system located in the large triangular area enclosed by the Uralides in the west, the East Siberian Craton in the East and the Asian Intermediate Units in the South. They commenced their evolution in the Vendian as a continental margin arc extending from the South Caspian area in Europe to the southern leg of the Tuva-Mongol continental fragment. This continental margin arc was largely detached from the Russian and the East Siberian Platforms in the early Cambrian in consequence of back-arc extension. In the present-day north Kazakhstan a large oceanic transform fault initially guided this separation, but it localised an ensimatic arc system beginning in the late Cambrian. This arc system, called the Kipchak Arc, remained attached to its parent continent in the Tuva-Mongol fragment and its free end collided with the Russian Craton in the late Ordovician. Following this collision the Kipchak Arc began to be horizontally stacked along large arc-slicing strike-slip faults, which, by late Devonian formed a considerable continental entity now forming eastern Kazakhstan. This entity collided with the eastern Urals in the early Carboniferous and its present southern part formed an orocline that progressively tightened until the Permian. In the entire Palaeozoic the Altay Mountain System grew by coastwise transfer of forearc units from Mongolia to the eastern margin of the East Siberian Craton, while within the Tuva-Mongol fragment the Khangai-Khantey subduction-accretion system grew. Between the early Carboniferous and the early Permian Eastern Siberia and Russia sheared right laterally and that shearing then reversed to left lateral. This shearing events not only further shuffled the internal structure of the entire Altaid orogeninc system, but also led to the extensional events in the West Siberian Basin, Junggar and Turfan and beyond into Southern Mongolia and China. The evolution outlined here is entirely compatible with the existing palaeomagnetic and palaeobiogeographic data. About half the orogenic collage thus assembled is of juvenile origin and indicates considerable continental growth (about half of the entire Palaeozoic growth). In and around the Tuva-Mongol fragment, contribution from older continental crust was more considerable than in the more westerly parts. Altaids and similar Turkic-type orogens (e.g. the Gondwanides) have led to sea-level rise during their subduction-accretion controlledgrowth phase and sea-level drop in their collisional phase. The areas they collectivley first submerged and then exposed seem to have had a strong influence on world climate by changing the terrestrial albedo and shifting the Urey reaction first one way then the other. The evolution of the Turkic-type systems also strongly controlled the 87Sr/86Sr ratio in sea water.
DE: 8110 Continental tectonics: general (0905)
DE: 8177 Tectonics and climatic interactions
DE: 8185 Volcanic arcs
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005