| In various basins of the Bohai Bay, only the East Liaohe depression has well-developed trachyte. This phenomenon has long aroused much attention among geologists in China. Based on an integrated analysis of rock characteristics, tectonic movement and formation background, this paper holds that the original trachyte magma was derived from the deeper part of the upper mantle, the basalt and other igneous rocks were comagmatic rocks, but the trachyte experienced a longer time of crystallization differentiation. It is also considered that the formation of trachyte magma in the upwelling process did not experience any mixing action, with the external environment being part of the underwater eruption, that the tectonic movement constituted the internal cause for the development and distribution of magmatic activities and igneous rocks, and that the unique characteristics of the three middle sedimentation periods of the eastern sag created the internal and external environment background for the development of trachyte. |