| The Longmenshan thrust belt locates in the west side of Sichuan basin, the boundary of Yangzi metaplatform and Songpan-Ganzi bow area. It is a huge structure belt extending from NE—SW and composed of several faults with NE, NW and little SW aligement. The tectonic character is complicated, and different part with different tectonic control factor. The text analyze the tectonic pattern assemblage, distribution character and its effect on oil and gas distribution. The main goal is the tectonic difference. Meanwhile at the base of basin and range couple mechanism and tectonic evolution's influence on oil and gas accumulation, the text finally have evaluated the potential available area for exploration.It can be concluded from today's tectonic pattern, the later overlapping of tectonic movement and reforming are common. And because of different part with different pattern of reforming, the structure is rather complex today. The Longmen mountain thrust's movement in each episode were from the thrust of deep basement and block and cause the tectonic emplacement to the basin with considerable scale. There are consumering zone and propagation which are marked with imbricated passage in the front range. And also there are recoil faults and recoil bow area. The tectonic features today are overlapped with early deformation. As for early deformation, the main phenomenon are represented as the deformation of new layer, which are different with old layers. The tectonic emplacement in plane and the deformation before the cutting ,or made the early deformation become more close.The mainly character of Longmen mountain thrust belt is divergence. From south to north, different tectonic section has their own tectonic character; From west to east, several main fault control the different tectonic deformation belt; In vertical, each tectonic layer represents the deformation of different episode. As for tectonic pattern, the imbricate thrust and fault reversing fold of late Indosinian distribute mainly in north section of Longmenshan mountain, and the Gulf-Coast-type fault transition fold are preserved in Dayi of south section. The tectonic subduction fold belt of Yanshan-Himalayan movement developed in the downdip block of thrust belt, each fault are commonly below Jurassic system, and the tectonic movement happened during Yanshan-Himalayan episode, but little later than thrust-decken structure.To decrease the stress to the foreland basin, the main tectonic pattern are fault propagating fold and local recoil fault. Still there are some branched faults thrusting to the surface and became secondary thrust fold. Imbricate deckenbau belt is at foremost fault belt in joint of Longmen mountain and Sichuan basin. It occurs during Himalayan episode and formed with two major thrust belt: Baishuihe thrust fault belt and South Baoxing-Pengguan-Anxian thrust fault belt, which lays overlapping. Regarding the source and the expressing pattern of tectonic sfault tress, the back belt of Beichuan-Yingxiu big fault is the source. The tectonic character shows the fault thrusts from deep to shallow layer; The front range is the main belt to release the stress. From Yanshan episode, at the control of the bench fault, the thrust developed form deep to shallow and was overlapped by later tectonic deformation. All those above form the complex tectonic framework of Longmen mountain.The tectonic evolution developed gradually from south to north and the main episode for formation is delayed. The huge thrust of indosinian first occurred in north section, while the bench thrust emplacing to basin with large scale of Yanshan episode occurred in middle and south part. The intense uplift of Himalayan caused large emplacement in south part. Longmen mountain thrust belt has great potential for exploration of oil and gas. Up to now, there are some desirable progress from some part of it. Finally the text find three available belt for exploration, which show bright prospect.
|
PDF Full Text Request