Structrural Character Research In The Northern Sichuan Basin

The northern section of the Longmen Mountain, the Micang mountain tectonic belt and Daba mountain tectonic belt in the northern Sichuan Basin have long been receiving geologists' attention, but the researchs were mostly focused on the Sedimentary characteristics of foreland basin and tectonic deformation features. Researchs on orogenic belt were limited to one region or one domain, and is still weak in integrative research of tectonic characteristics and evolution of the northern Sichuan Basin, especially in integrative structural characteristic of the northern sections of the Longmen Mountain, the Micang Mountain tectonic belt and Daba mountain tectonic belt.With the improving of exploration techniques and the more and more noticeable contradiction between energy supply and demand, increasing attentions are drawn to the Petroleum Resources and exploration potential along foreland basin in the northern Sichuan Basin. To understand the tectonic characteristics and the mutual tectonic relationships among the three mountains that have guiding functions to the structure analysis and the oil and gas exploration in the northern Sichuan Basin and even the whole Sichuan Basin.According to the above reasons, I take regional structural deformations and tectonic evolution as starting point, then consulted and summarized the previous results, combined the results and explanations of geologic investigation and regional seismic sections, make use of relatively geological theory, Researched the structural deformation, tectonic evolution and the mutual tectonic relationship of the northern sections of the Longmen Mountain, the Micang mountain tectonic belt and Daba mountain tectonic belt.Study results revealed that Micang Mountain tectonic belt is a approximate autochthonous system that have small napping distance from north to south . The exercise Modes of the thrust-nappe in the northern section of the Longmen Mountain and Daba mountain tectonic belt are former extend modes from back to front,then the deformation strength also gradually weak from back to front. The diachronism close of Mianlue Sea from east to west in indosinian period leading to the difference of tectonic evolvement and tectonic deformation in the northern Yangzi Block. The northern sections of the Longmen Mountain was formed by events which were the closing of Mianlue sea , SN compression of Qinling tectonic belt, extrusion of left-lateral strike-slip by Qinling tectonic belt in yanshan period, and the more stronger tectonic deformation in himalayan movement. Daba Moutain tectonic belt suffered discontinuous SN compression in Caledonian period, intensively SN compression in indosinian Period and yanshan period leading to south-directed thrusting. The himalayan movement strengthened the south-directed thrusting and tectonic deformation intensity of Daba Mountain tectonic belt. In the process, Daba Mountain tectonic belt got the holding up by Michang Mountain and Huangling block ,then format the SW curvy extrusive structural features. Micang Mountain tectonic belt is a approximate autochthonous system that have small napping distance from north to south, suffered SN compression from Qinling leading to EW linear structure in himalayan. But it suffered SW compression from the northern sections of the Longmen Mountain at a later stage ,forming NE thrust faults that incised and changed the former structure. Micang Mountain tectonic belt held up the west Daba Mountain's extend to SW.