Abstract:

The Jiali fault is an important part of the WNW-ESE trending Karakorum-Jiali fault system in the southern Tibetan Plateau, which is considered to be an ancient suture zone between the north Lhasa and the central Lhasa block. However, the tectonic properties and deformation ages of the Jiali fault are still controversial and need further study. Based on detailed regional geological mapping, our work focused on the Guxiang-Tongmai section of the Jiali fault, especially on investigating the geometric and kinematic characteristics, and subsequently on restoring and calculating the stress field and their direction in different periods, based on the newly identified fault planes and striations of different directions. Accordingly, we analyze the superimposing structural relations of this area, and discuss the multi-stage activity characteristics of the Jiali fault under different tectonic stress fields, and the regional tectonic evolution and background. Consequently, the influence of the Jiali fault on the proposed Sichuan-Tibet railway line was discussed. Results indicate that the Jiali fault is active from the Late Cenozoic, and show tectonic superimposed characteristics, including (from early to late) the sinistral strike-slip fault (D₁), normal fault (D₂) and dextral strike-slip fault (D₃). As an important accommodation structure of the eastern Himalayan syntaxis, the multi-stage deformation of the Jiali fault zone reflects the relative movement of adjacent blocks and the regional tectonic stress field conversion, which is of great significance for understanding the Cenozoic tectonic evolution of the southern margin of Tibetan Plateau.

Key words: Tibetan Plateau, eastern Himalayan syntaxis, Jiali fault, multi-stage deformation, stress fieldanalysis