Study of Crust and Lithosphere Velocity Structure Character of Chinese North‐South Tectonic Belt and Its Adjacent Regions

Abstract

AbstractIn this paper, we based on gravity data and used the inversion method of Parker‐Oldenburg to calculate the crustal thickness in Chinese North‐South tectonic belt and its adjacent regions, while we also used the inversion method of seismic tomography to research the three‐dimensional velocity structure of the crust and mantle in the study area. According to the results of calculation we discussed the crust and lithosphere structures of the study area. We tried to reveal the deformation characteristics of crust and lithosphere of Chinese North‐South tectonic belt and its adjacent regions, and then discussed the deep causes of the crust‐mantle tectonic evolution in the Tibetan Plateau active zone, the upper mantle rheological property in the study area and its dynamics significance. The studies show that the crustal thickness of the North‐South tectonic belt changes rapidly, the west area has a thickening crust, the east area of Ordos Basin and Sichuan Basin has a stable crust, while further eastward the crust is thinning. The boundary between thinning and thickening lithosphere is limited in the Da Hinggan Ling Mountains‐Taihang Mountains‐Qinling Mountains‐Daba Mountains‐Wuling Mountains area. It is also the deep tectonic boundary of eastern continental margin zone and central Yangtze‐Ordos Craton regions. Not only are the shallow geological structures different on its two sides, but the physical property state and the thermal activities in the deep upper mantle are also distinctly different, which indicates that, in the study area, the structure of lithosphere and asthenosphere, and the distribution of deep material are laterally heterogeneous. Deep tectonic boundary of the central region and Tibetan Plateau is located at about 100°E–102°E longitude.