The Study Of Magnetic Structure Over Longmen Mountains Tectonic Belt And Its Adjacent Areas

Longmen Mountain Tectonic Zone is located in the west of sichuan basin, and east of Songpan-Ganzi Block. And it is situated in midpiece of the North and South Tectonic Belt. Its tectonic activity not only affects the formation of oil-gas reservoirs of Western Sichuan Basin, and has meaning to Interpretation of seismic activity of North and South Tectonic Belt and east dynamics of Qinghai-Tibet Plateau.Using the satellite magnetic surveying data and aeromagnetic data,we research the basement of North and South Tectonic Belt and Longmen Mountains and its adjacent area.Because its scope is too vast,and the lack of data,we research the basement magnetic structure of the North and South Tectonic Belt in the way of satellite magnetic. At the same time, with the same method we do Longmen Mountains and its adjacent area.Then,we do data processing and interpretation of it:First of all,to reduce the influence of inclined magnetization,the reduction-to-the-pole is necessarry. Secondly, to understand base of different depth levels, we upward continuat aeromagnetic data to different height,and do the residual processing of them. Finally,the author estimates depth of basal top and bottom interface in the way of Tilt-depth method and Bureau inside inversion method respectively, and make the euler deconvolution of inversion to three profile.Through the above all sorts of ways the conclusions are as follows:(1) As compared to the two boundarys of the tectonic trends which change from NE to NW between surface tectonic units and basement’s,the boundary has trend of westward movement,by analizing satellite magnetic surveying data of North and South Tectonic Belt and its adjacent area.(2)The shallow basement of SongPan-GanZi Plot has the structure properties of the YangZi Plot,that show its shallow base is consistent with Yang Zi Plot’s.(3) Base of Sichuan Basin put down to the basement of Longmen Mountain Tectonic Zone Westward.And the most level distance is50km,that show the NW tremendous power.4) Top interface depth of west area’ base of Longmen mountains is not suddenly become lighter.The size is also not suddenly become smaller.There is a line,from SongPan-north to Blackwater.The west area basement’s top interface depth of the line is about5km;the one of east is similar to the one of Sichuan Basin (7km～18km),and the change is not big,the most is to14km or so.It ia from a few kilometers to ten kilometers Vertically.(5) A north-south MinShan Tectonic Belt are showed clearly in the second order derivative figure, the0-30km residual vertical second order derivative diagram and Tilt-depth method figure.