A new model for the dynamic evolution of Chinese lithosphere: 'continental roots-plume tectonics'

Chinese continental lithosphere comprises three tectonic domains: (1) eastern China, a region characterized by rifting, extensional basins, and voluminous basaltic volcanism; (2) central China, a plexus of cratonic terrains with low-heat flow (4050 mw/m(2)), including the Tarim, Erdos, and Yangtze blocks welded by pre-Cenozoic orogenic belts; and (3) western China, a region comprising the Qinghai-Tibet-Himalaya orogen. The relatively thin crust (similar to35 km) and lithosphere (similar to70 km) of eastern China is believed to reflect mantle upwelling, while near-normal crust (similar to45 km) and thickened lithosphere (>200 km) in central China suggest a mantle lithosphere root resembling those inferred for the Kaapvaal and Siberian cratons. Thickened crust (similar to70 km) and lithosphere (>150 km) in western China reflect the advanced development of an orogen root. The lower density and relative buoyancy of central cratonic mantle roots appear to have contributed to the long-term tectonic stability of the central Chinese lithospheric blocks. In contrast, gravitational instability produced by thickening of the denser western Chinese lithosphere and the resulting subsidence and eventual delamination of orogenic roots are believed to have led to postorogenic extensional collapse. Although the geological relationships suggest compressional forces caused both mountain building and orogen root development, extensional stress resulting from gravitational collapse is believed to have induced lithospheric and crustal thinning with concomitant reduction of topography. The term 'continental roots-plume tectonics' has been adopted to describe the configuration and dynamic condition of subcontinental lithosphere and upper mantle beneath China. Accordingly, it is proposed that supracrustal tectonic forms represent the surface expressions of, and responses to, deep 'continental roots-plume tectonics'. While the prevailing view is that the western orogenic belt is not genetically related to eastern continental rifting, such a relationship is inherent to the continental roots-plume tectonics model. It is further proposed that the formation of orogenic lithosphere roots triggered eastward extrusion of the asthenosphere along the 400-km depth mantle interface, and, in response to subduction at the eastern margin, produces plume-like upwelling beneath eastern China. We suggest that processes involved in continental roots-plume tectonics are directly responsible for the formation and evolution of the Eurasian supercontinent. (C) 2004 Elsevier B.V. All rights reserved.