The reconstruction of preliminary three-dimensional earth's model and its implications in China and adjacent regions

Jie Shou Zhu, Jia Min Cao, Xian Gui Li, Bin Zhou

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40 Scopus citations

Abstract

The continent of China and its adjacent regions formed by a series of plates and blocks convergence rapidly in the late Paleozoic (about 200- 300 Ma). The Indian subcontinent collided with Eurasian continent causing the crust shorted and uplifted in the late Mesozoic to Paleocene epoch forming the highest plateau of Qinghai- Tibet and Pamir, and orogens of Himalayan and Hindu Kush. Based on the Global Geosciences Transects(GGT) and the results of tomographic inversion by seismic body wave and surface wave data, the three dimensional velocity structure from upper crust to Core-Mantle Boundary (CMB) have been reconstructed in China and its adjacent regions. It shows the great lateral various for each spherical layers in lithosphere / asthenosphere system (depth from 0 to about 400 km). Alpine- Himalayan belt throughout the Northern Pakistan (Hindu Kush and Pamir), Qinghai-Tibet plateau including Tarim basin and Tian-Shan mountain chain characterized by the continent-continent collision zone with thick crust and lithosphere. The eastern part is influenced by the motion of Pacific plate and with the thin crust and lithosphere. The average thickness of lithosphere in the region is about 100 km, several paleonuclei and paleolands, such as Tarim, Yangtze, Ordos and Indian shield are represented by great thickness of lithosphere. The fold belts, such as Altai, Qinlin belt, North-South tectonic belt, southeast continental margin, South China sea, East China sea, Ryukyu trench represented by thin lithosphere. In the lower mantle (depth in 700-1200 km) the velocity distribution shows the northsouth trend. The high velocity regions are presented in the Japan sea and East China sea, and also appear in the N-S tectonic belt through out central China. In the depth 2200- 2800 km close the CMB region a huge high velocity anomaly is distributed from east to west, this could be explained as a super cold downwelling plume in the east and central Asia. The super downwelling plume underneath Asia is the dominant pattern of vertical mantle flow in the modem Earth. This huge cold plume is formed by the multi-subduction of oceanic plates of paleo Tethys and Pacific, the cold slabs was supplied by plates at trench and down to lower part of upper mantle (670 km in depth), where they were accumulated, and after a geologically significant time the stagnant mass of cold slabs gravitationally collapsed onto the CMB. Once it is formed in lower mantle, the mantle convection patterns in the upper mantle tends to be strongly controlled by a sole downwelling superplume in the lower mantle. Thus all continents tend to be swallowed into the cold superplume until they are collision and amalgamation to form a super-continent. The central Asia, from Indian subcontinent to Tibet, Xijiang, Mongolia and Baikal regions are the present largest convergence place in the world, there are thicken crust and lithosphere, showing high compressional stress in the crust, low heat flow and broad distributed earthquakes, and negative gravity anomaly, lowest geoid, all of these characteristics indicate the mantle materials fall down to the CMB and continents converged in this region.

Original languageBritish English
Pages (from-to)X5-648
JournalActa Geophysica Sinica
Volume40
Issue number5
StatePublished - 1997

Keywords

  • Blocks dividing in lithospheres
  • China
  • Downwelling superplume of lower mantle
  • Three-dimensional structure of earth

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