Abstract: This paper gives an idea that the basement of Santanghu basin has a dual structure by combining the regional structures with the gravity, magnetic and electrical property data in the basin. The deeper basement formed as the Pre Cambrian crytallized basement segmented with the another land mass in the west or continental marginal residual plates and fragments of ocean crust, and then was superimposed with the shallower folded basement dominated by Hercynian igneous rocks. Such dual. nature significantly affected the characteristic of seal structure. In the east the later structural deformation of the seal is inbibited due to the presence of deeper rigid basement, which resulted in the formation of extensive wide and gently dipping traps in the caprock; while in the west the linear folds, fault trace and blocks formed in the caprock due to the absence of the rigid basement. The present tectonic framework is almost controlled by the shallower (Lower Carboniferous) basement.

Key words: Xinjiang, Santanghu basin, Basement structure, Caprock