The lithospheric structure differences between the western and eastern Qilian in the northeastern Tibetan Plateau

作者：Li HuiLin; Huang XingFu; Gao Rui^*; Ye Zhao

来源：CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION, 2022, 65(5): 1581-1594.

DOI：10.6038/cjg2022P0735

• The northeastern Tibetan Plateau
• Qilian Orogen
• Lithospheric structure
• Crustal deformation
• Joint inversion

As the northeastern margin of the Tibetan Plateau, the Qilian Orogen has significant differences in geomorphology and Cenozoic surface deformation patterns between the eastern and western segments. Under the common tectonic background of the Tibetan Plateau extending to the northeast in the Cenozoic, the causes of these differences between the eastern Qilian and western Qilian are still unclear. Based on the observation data from a broadband dense station array, the intracrustal and uppermost mantle structures in the eastern Qilian are derived by using the joint inversion of receiver functions and surface wave dispersions with P-wave velocity constraints. Combined with the previous research results in the northeastern Tibetan Plateau, this paper compares the lithospheric structures of the eastern Qilian and western Qilian, and discusses the differences in the crustal deformations of the eastern Qilian and western Qilian, thus revealing the possible causes of these differences. The crustal structure differences in the eastern Qilian and western Qilian are mainly as follows: (1) Differences in the crustal low-velocity zone: At a depth of 20-40 km, there is a low-velocity zone (3. 2 similar to 3. 4 km.s(-1)) in the middle crust of the western Qilian (profile BB'), while the middle crust of the eastern Qilian (profile AA') does not exist the low-velocity material. (2) Differences in the lithospheric mantle: The lithospheric mantle in the western Qilian is characterized by blocky low-velocity anomalies, while the lithospheric mantle in the eastern Qilian is characterized by relatively uniform high velocity material. The crustal shortening and deformation of the western Qilian are greater and the crustal strength is relatively weaker, which is manifested as high-altitude mountains and relatively thicker crust, while the crustal shortening and deformation of the eastern Qilian are weaker, showing the relatively flat Linxia and Longzhong basins and thinner crust thickness. The differences in crustal strength and deformation between the eastern and western Qilian may be related to the structure of the deep lithospheric mantle.

• 单位
  中山大学; 桂林理工大学