(2) episode of fast thinning (e. g., delamination) of the lithosphere, in company with extension and collapse of the orogenic belt and magma underplating in the lower crust during later Yanshanian;

• (2)燕山晚期岩石圈快速减薄（如拆沉作用），造山带拉伸塌陷，地壳深处并发生广泛的底侵作用；