Indosinian-Yanshan crustal activation stage

At the end of Permian, North China Plate and Siberia Plate were combined, and in Middle and Late Triassic, Yangtze Plate and North China Plate were combined, and the Paleo-Tethys Ocean was completely closed. Jiaonan Uplift Area and Ludong Uplift Area have been integrated with Yangtze Plate and North China Plate, and entered a period of synchronous development. In the early days, the compressive stress in the north-south direction still played a major role. Due to the subduction of Kula-Pacific plate, the strong compressive stress in the southeast direction gradually dominates. The long-term movement of the NNE-trending Tanlu fault zone is dominated by sinistral strike-slip, which leads to the formation and development of normal faults in all directions under the tensile system, and the magmatic activity is also quite intense.

Indosinian period (Triassic) is the transition period of tectonic stress field. Before Indosinian period, the principal compressive stress field was nearly north-south and nearly east-west fault activity, and some nearly vertical north-south faults were formed in Luxi area. At that time, there may be mantle flowing from north to south, so the east-west faults generally tilt south. In the late Indosinian period, the principal compressive stress changed to NNW and NNW. The NE-trending fault represented by Changyi Dadian fault strongly moves to the left, which is related to it. The original or later NW-trending, NE-trending and nearly EW-trending faults also have different degrees of activity. At that time, the terrain was different from Paleozoic, with high in the south and low in the north. Finally, almost the whole Shandong Province has suffered from different degrees of erosion.

During the Yanshan period (J-K), due to the subduction of the Kula-Pacific plate to Eurasia, the principal compressive stress came from the southeast. In the first act of the movement (J 1 -2), the main faults of the Tanlu fault zone have appeared and experienced longitudinal extension activities. In the Fangzi area in the northern part of the fault zone and the northern part of the Luzhong uplift, Fangzi Formation deposits have developed along the nearly east-west fault depression zone from Zhangqiu to Zibo. In the second act of the movement (J3), the Tan-Lu fault zone is still twisting to the left, and the two groups of NNW-trending and NNE-trending torsional fracture surfaces induced by it are developed to varying degrees by using the existing faults, especially the NW-trending fault activity is obvious. All areas in the province are mainly uplifted, while Jiaolai and southwestern Shandong are relatively declining, and they are deposited by Mengyinshan Formation (Laiyang Formation). Finally, there is magma intrusion along NE and NE faults in eastern Shandong. In the third act of the movement (K 1), the Tan-Lu fault zone is deep in the mantle, which may be caused by the lateral extension of mantle material, which changed from compression activity to extension activity and entered the stage of rift development. Under the extension, a large number of volcanic eruptions were triggered, and thick volcanic rocks of Qingshan Formation were formed. Qingshan Formation was also deposited in Jiaolai sag in eastern Shandong and some NW-trending fault basins in western Shandong. In western Shandong and Jiaonan Jiaobei, Ai Shan magmatic intrusion occurred. In the fourth act (K2) of the movement, the Tan-Lu fault zone continued to develop in the form of a rift, still twisting to the left, and a very thick Wang Formation was deposited in the fault zone and Jiaolai Depression. At the end of the period, all groups of faults were strongly active, resulting in slight folds, accompanied by magma intrusion in Laoshan period, and the crust rose in an all-round way, and all areas were eroded.