The Analysis Of Tectonic Stress Field Of The Mesozoic In Lower Yangtze Region

The lower Yangtze region is an important volcanic rock ore concentration area of our country, with frequent tectonic and magmatic activity and complicated geological condition. Many academics conducted a detailed study on this, but there are still many phenomena not very well explained. This article following studies the brittle deformation of the lower Yangtze region, based on field survey, the joints and faults in the study area were systematically studied, with regional structural analysis, the sequence of4issues of the meso-Cenozoic tectonic stress field was acquired and regional characteristics of tectonic stress field evolution and dynamic mechanism was analyzed. Sequence of tectonic stress field, in turn, from early to late, is Indosinian Stage NE-SW to tectonic extrusion, the early Yanshan nearly S-N to tectonic extrusion, late Yanshan about E-W to extend, and about E-W to early Himalayan tectonic compression.By use of GIS technology, geological database of the lower Yangtze region was established, and a geological database software for field data collection and fee based data processing was developed, with software tools developed based on GIS and Ansys such as the automatic establishment of the geological model and mathematical model.The author try to conduct a numerical simulation and analysis on tectonic stress field of lower Yangzi plate in early Yanshan through studing on geometric and kinematic and tectonic evolution of Yangzi,Then to discuss about the structual shape and distribution in Yangzi region according to the comparison between simulation and practical structural phenomenons. The analytical result indicates that the high value area of the maximum principal stress distributes in the top of Dabie Mountains outstanding body and TanLu fault zone in Hefei-Tancheng paragraph, and the secondary maximum principal stress distributes mostly in both sides of fault and shows the intensity and regularity, which is nearly parallel with the fold axis in this region. The spread of volcanic downfaulted basins in the middle and lower reaches of the Yangtze river is in accordance with the distribution of isoline nephogram of the maximum principal stress. The high value area of shear stress is concentrated along the faults belts and where the occurrence of the fault was changed, such as Tanlu fault zone, Guishan-Meishan fault zone,Wulian fault zone and the sections where the occurrences were changed in Jiangshao fault zone and Jiangnan fault zone. The displacement field shows that the lower Yangtze plate in Yanshannian had a tendency moving towards east and west by virtue of north-south oriented compression, the maximum displacement velocity was40.75mm/a, the minimum was2.49mm/a.