International Geologiical Congress - Oslo 2008

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ASI-02 Geology and mineral resources of Northern and Central Eurasia

 

Principal characteristics of the lithosphere of China and Adjacent areas

 

Tingdong Li, Chinese Academy of Geological Sciences (China)
 

 

China is situated in the conjunct sector of Eurasia, India-Australia and Pacific plates, where the structures of the lithosphere are very complex and show some obvious characteristics.
The crust of the Chinese continent is rather thick; the relief of Moho basically presents mirror image of surface topography. The crust of the Qinghai-Tibet plateau is the thickest in China and even in the globe. The thickness of the margin is 44-60km. In hinterland of the plateau, the thickness is 60-70 km; it may amount to 80 km, constituting a huge "mantle basin" roughly in E-W direction. Eastern China and adjacent sea areas are regions where the crust thickness becomes thinning; The Songliao and North China plains are two "mantle uplifts" with the crust thickness ranging from 30 to 34 km. The crust thickness of the sea areas sharply decreases to 30-20 km. The contours of the crust thickness strike approximately E-W in the west, while NNW in the east.
The lithosphere of China and adjacent areas presents a tendency: thicker in the west and thinner in the east, at the same time, thicker in the south and thinner in the north. The Central Asia, Qinghai-Tibet plateau and Sichuan basin are the regions where the lithosphere is thickened with a thickness of the lithosphere ranging from 170 to 190 km; in the northeastern Tarim basin and Changdu area of eastern Tibet, the thickness amounts to 200 km. To the east of the Great Hingganling-Taihang Mountains-Xuefeng Mountains, including marginal seas, it is a region where the lithosphere is thinning with thickness of the lithosphere ranging from 50 to 85 km. The lithosphere of the area between the two regions mentioned above is gently thinning, or it is a stable area, with thickness of the lithosphere ranging from 85 to 170 km. Researches show that great difference of structures of the lithosphere and asthenosphere exists between the east and the west of China. In the west, the lithosphere and asthenosphere show obvious "layered structure" with very thick lithosphere (130-200 km) and thin asthenosphere (40-100 km), reflecting an environment of collision and convergence of plates; In the east, the lithosphere and asthenosphere show "mosaic block structure" with very thin lithosphere (50-85 km) and very thick asthenosphere (200-300 km), reflecting characteristics of upsurge of asthenospheric materials and extensional thinning of the lithosphere.
Inverse tomographic images of seismic surface waves show a huge anomalous zone of low velocity in the depths from 70 to 250 km in eastern Asia and northwestern Pacific regions. This zone is 12 000 km long from north to south, and 2 500-4 000 km wide from west to east, the lithosphere is thin in thickness (50-80 km) with low Vs (4.20-4.35 km/s); the asthenosphere is very thick(c. 300 km)with very low Vs(4.15-4.28 km/s).
The lithosphere of the Chinese continent and adjacent sea areas may be divided into 5 types: cratonic, orogenic rift, island arc and oceanic crust.

 

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