Structural and Tectonic Correlation across the Central Asia Orogenic Collage: Implications for Continental Growth and Intracontinental Deformation

Central Asia encompasses nearly a dozen countries and consists of several orogenic complexes, one of which, the Altaids, is ~1000 km wide and ~7000 km long, stretching from the Ural Mountains in the west to the Pacific Ocean in the east. It is composed of several tectonic collages that were created by oceanic subduction and continental collision from the late Proterozoic to the end of the Paleozoic.  The last decade witnessed the establishment of two competing tectonic hypotheses for the development of these orogenic complexes.  The first views the Paleozoic-Early Mesozoic development of Central Asia as a process of continuous growth of the continental crust by duplicating arc and forearc materials via large-scale strike-slip systems during subduction.  In contrast, other workers consider that frontal collision and collapse of back-arc oceans are the main mechanism for crustal growth of Central Asia.  The two competing hypothesis have distinctive predictions with regard to (1) the basement age of metamorphic complexes in the orogenic belt, (2) the style of deformation, and (3) the paleogeographic position of major tectonic units within the orogenic belt.  Beside Paleozoic accretionary tectonics, Central Asia is also a locus of extensive Cenozoic deformation.  Debate in the past two decades has been focused on whether the deformation was induced by (1) the far-field effect of Indo-Asian collision, (2) back-arc deformation induced by interaction of the Asian and Pacific plates, and (3) flow and upwelling in the deep mantle.  Although testing these first-order problems would yield important insights on how continental crust has grown and how continental lithosphere deforms, the failure to correlate even the first-order tectonic elements and boundaries in the region has severely hindered our understanding of the region.  Because the Central Asian orogenic belts cross several international borders, to tackle the above problems requires a collaborative and systematic approach across the entire region.  Although some international collaborations have occurred or are still underway, these early studies nearly exclusively emphasize the geochemistry of igneous and metamorphic rocks and mineral resources.  Little attention has been paid to structural investigation of major tectonic boundaries in terms of their geometry, kinematics, and temporal evolution.  Consequently, tectonic implications of the geochemical and petrological studies in central Asia have been somewhat ambiguous because the structural and tectonic settings are not well defined.  To put emphasis on structural and tectonic studies and correlating major tectonic boundaries and units across international borders, we organized a new IGCP project entitled “Structural and Tectonic Correlation across the Central Asia Orogenic Collage: Implications for Continental Growth and Intracontinental Deformation”.  Its main mission is to assist international collaboration to solve the first order tectonic problems listed above.  We plan to host five workshops in four different Central Asian countries, with the aim of initiation collaborative research that will lead to the systematic correlation of tectonic, stratigraphic, igneous, and metamorphic units across Central Asia in both east-west and north-south directions.

The project is started in 2005. We had three successfull workshops in Irkutsk, Russia (2005), Ulaanbaatar (2006), and in Beijing (2007). IGCP-480 is funded by UNESCO and IUGS.