| Based on field survey, combining with date of seismic, logging and drilling, the study on the characteristics of extensional fault in western Shandong is carried out mainly by methods of structural analysis, with the help of apatite fission track and K-Ar dating. Incidentally, this thesis investigates the deep background, developing mechanism of the extensional fault system and reveals the evolution process of it by methods of physical modeling and magmatic petrography.Steep normal fault and Shallow décollement fault composed the fault system of the western Shandong. With large scales, long developing time and deep cutting, 60°~70°of dip angle, the NW-trending and nearly EW-trending boundary extension faults which are parallel aligning from south to north in western Shandong, control the sediment of the half-grabent that has formed since late Mesozoic. Breccia, cataclasite and fault gouge developed in the fault belt indicate that it has undergone several tectonic movement. The analysis also suggests that shallow gently dipping décollement fault mainly developed along the unconformity between the Cambrian and Archean. Although the thickness of décollement fault belt varies from each other, the attitude is consistent with the stratums'. At the décollement fault belt, there are cataclastic rocks with dynamo-metamorphic rocks and some small folds, scratches, steps, and so on. Shallow décollement fault and steep normal fault composed the structure style of the western Shandong. Horizontal extension amount and vertical activity rate of normal faults show that the steep naormal faults reversed negatively in late Mesozoic, and western Shangdong began to extention. In the Paleogene, the activity rates of the NW-trending faults reached peak, western Shangdong subjected to strong extension. Then, in the Neogene, faults hardly activated, and western Shandong approximately trended to be stable. Décollement faults slided along the strata dip. The directions are NE and NNE. Steep normal faults detached from a certain deep décollement surfaces, and become deep detachment faults in deep crust or low velocity layer in mid-crust. They slided direction is south and opposited to the strata dip.Apatite, zircon fission track, and cooling history simulation of the samples in steep faults'footwall manifest that Mengshan, Lianhuash, and Mountain Tai began to uplift in late Cretaceous. Cenozoic can be diviede into three rapid uplifting stages. They are 65~60Ma,48~42Ma and 25~20Ma. That, at the same, is reflected by the samples in depression. Combined with the uplifting velocity of these three stages in Cenozoic, sedimentary characteristics and igneous raock features, the results show that the main active periods are late Jurassic-early Cretaceous, 65~60Ma,48~42Ma. And they indicate a law that the activation of steep normal faults strengthens gradually from south to north, east to west.According to the analysis of K-Ar isotopic data of bedding intrusive rock in fault belt, the earliest regional décollement happened during 130-110Ma, with another two during 55Ma and 45Ma. The consistence in time with the developed periods of steep normal faults reflects that intense activities can promote the development of gently dipping décollement faults.The analysis of physical modeling and magmatic petrography indicates that the development of extensional faults system in western Shandong is attributed to the deep extension brought about by the delaminating and thinning of lithosphere in late Mesozoic and the shallow extension caused by the upwelling of asthenosphere mantle in Cenozoic. These two kinds of extension faults are consistent with each other in both development phase and regional tectonic stress field. In mechanism,it was caused by the subduction of the Pacific Plate in late Mesozoic, the strike-slipping of Tanlu Fault and the Indo-Asian collision in Cenozoic.
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