Geodynamic evolution of east and southeast Asia island arcs

Category Geodynamic
Group GSI.IR
Location International Geological Congress,oslo 2008
Source www.۳۳igc.org
Holding Date 18 August 2008

 

Geodynamic evolution of east and southeast Asia island arcs

Wakita, Koji
Geological Survey of Japan, AIST, Japan

    East and Southeast Asia island arcs are located in the western Pacific region. Japan, Philippines, Indonesia and the Borneo island of Malaysia are covered by the region. Most of these countries are situated at the transition zone between the ocean and continental crust. Based on the Wilson orogenic cycle, the said areas are immature. After the breakup of the supercontinent Rodinia into the Yangtze and Laurentia at 750-700 Ma, this region had not experienced severe continental collision throughout its history. This is a typical characteristic of East Asian geological setting.
The main tectonic activities of the region are ocean plate subduction, development of island arcs, collision of island arcs and micro continents and the opening of marginal sea.
Ocean plate subduction has occurred continuously since the early Paleozoic time. It has caused accretion of oceanic materials and volcanic activities which formed the island arc system. In the consuming margins, accretionary wedges are formed as uplifted mountains providing huge volume of detrital materials to the trench. However, if the detrital materials have become lesser and the subducting plate was old enough, tectonic erosion occurred instead of accretion.
Ocean plate subduction has also produced magmas to heat the existing accretionary complex which caused the formation of magmatic and metamorphic rocks in the subsurface and volcanoes on the surface. At the same time, subduction has caused the occurrence earthquakes of varying magnitudes and the formation of active faults on the surface. The subduction occurred along the Asian continental margin initially. As old and cold ocean plate started to subduct beneath the continental margin, marginal basins with thinned continental crust and/or ocean crust started to appear in the region. Part of the continental margin was detached from the main continental bodies to form island arcs.
Island arcs were also developed by successive ocean plate subductions and gradually become mature. Based on plate tectonic configuration, island arcs sometimes collide with microcontinents and other island arcs. Such collisions have caused exhumation of metamorphic rocks because of the subduction of buoyant materials underneath.