BASIC CHARACTERISTICS OF THE YANSHAN MOVEMENT IN NORTHEASTERN SHANXI -A SUMMARY OF REGIONAL SURVEY OF THE 1: 250000 YINGXIAN COUNTY SHEET

The Yanshanian crustal activity in northeastern Shanxi was intense and frequent and underwent a process of extension→transpression→uplift and magmatism.The early stage of the Yanshan movement generated an Early Jurassic downfaulted basin and a Middle Jurassic compressional-downwarped coal-accumulating basin.In the middle stage, the Mid-Late Jurassic witnessed the formation of a volcanic downfaulted basin bounded by NW and NE deep faults, intermediate-basic and acid volcanic eruption and hypabyssal and near-surface intermediate-acid magmatic intrusion, and the terminal Late Jurassic witnessed the formation of a number of NNE-trending folds and overthrust zones.In the late stage, in the Early Cretaceous a downfaulted basin and open gentle folds once again formed and the Yixian Formation unconformably rested on volcanic rocks; the Late Cretaceous was a stage of mountain uplift after compressional orogeny, when the Yixian Formation was unconformably overlain by the Zuoyun Formation, accompanied by intrusion of crust-derived granite, and NE-and NE-trending faults were revived, forming a graben-and horst-type fault combination and resulting in mountain uplift.