Mesozoic Tectonic Framework And Evolution In The Lingyuan-Jianping Area, Western Liaoning Province

The research area is located in the Lingyuan-Jianping region, western Liaoning Province,which is considered as the eastern part of the Yanshan intraplate orogenic belt.The research area dominated by NNE oriented structures differs significantly from western and central part of the Yanshan intraplate orogenic belt characterized mainly by W-E striking structures. This research focus on several questions such as follows.Are there developed W-E strike structure in the research area? How many kinds structures form the tectonic framework of the research area? What is the spatial and temporal relationships among the different structural elements? After detailed mapping in the research area, main findings and conclusuions are reached as follows:Through detailed field geological survey,we identified NNE-NE tectonic framework of the different properties in research area. Western thrust fault brought W-E striking structures to the hanging wall, which formed the typical fault-related folds with complicated hanging wall anticline and lying wall syncline.In the central of research area,it showed enormous scale of fault-bended fold and high-angle thrust which breaked the crest of anticline.To the east,it developped main thrust and secondary reverse thrust.Along the thrust, deformation was gradually developping to weak,resulting that the end of thrust fault was disappeared in the weak rock and tail plunging anticline was developed.Thrusting and related folding deformation caused 43% -54% of contraction rate.In addition,we found out the W-E striking structures which contained reversal anticline with the same dip of fold limbs and axial surface dipping to north, thrust fault with fault surface dipping to north and thrust fault with tear structure style. In addition,we also found out the NNW strike structure.According to comparison of the regional tectonic and isotope chronological evidence, W-E striking structures may be formed between the late Triassic and early Jurassic, between the NW striking structures formed between the W-E striking structures and NE-WE striking structures may be 174-168Ma. NNE striking structures was formed about 174.2 Ma and a further shrinkage occurred in the 156.9-137.2 Ma. NNW striking structures superimposed on the W-E striking structures, but also cutted by NE-NNE striking structures. NE-NNE striking structures constructed on the WE striking structures.not indicating the rotation characteristics of W-E striking structures.Above all,W-E striking structures may be the response of the development of Paleoasian Ocean tectonic system, NE-NNE striking structures may be the response of the development of Paleopacific tectonic system.