| 鄂尔多斯盆地西缘马家滩地区的构造样式与圈闭分布规律 |
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| 关键词:intra-continental deformation multi-level detachment fault-related folding structural style oil and gas trap Majiatan area western margin of Ordos basin |
| 基金项目:国家自然科学基金重点项目(编号: 41430316; 40739906);国家科技重大专项(编号: 2017ZX05001-001) |
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| Structural Style and Trap Distribution in Majiatan Area on the Western Margin of Ordos Basin |
| The thrust belt on the western margin of Ordos basin is an important element of the North-Southward Tectonic Zone in China, resulting from the intra-continental structural deformation between the Alax continental block and the Ordos continental block. The study of the geological architecture and structural style is not only a basis for exploring the mechanism for intra-continental deformation but also the key reference for addressing the earthquakes and the petroleum exploration. Based on the new boreholes, high-resolution 2-D and 3-D seismic data around this area, the authors investigated the structural deformation style and the oil and gas trap distribution by utilizing the method of structural analysis. It is shown that the Majiatan area is located in the middle segment of the thrust belt on the western margin of Ordos basin. Being a part of the Helanshan–Liupanshan intra-continental orogenic belt, it underwent a prolonged evolution from extension to compression. The geological architecture in this area is characterized by zonation, multi-level stratification, and segmentation. It has developed in the hinterland the extensional zone (i.e. the Yingchuan graben), the thrust and nappe structural zone (including the Weizhou–Xianmawan thrust sheet and the Shigouyi syncline), the foreland transitional zone, and the Tianhuan depression. The foreland transitional zone can be subdivided into the lower and the upper structural deformation systems by the regional detachment level of the Carboniferous to Permian coal or mudstone intervals. Dipping shallowly to the west, the lower one developed low-relief anticlines, while the upper one developed three belts of fault-related folding anticline, narrowing southward. The upper one is characterized by the south-northward segmentation due to the differentiation in detachment layers with the oblique transferring or transition. The Majiatan region and its adjacent areas are dominated typically by the three kinds of deformation, i.e., the inverted structural system controlled by the extensional-compressive cycle, the propagation deformation in the foreland system controlled by the intra-continental orogenic deformation, and the post-orogenic extensional system in the hinterland. The upper structural system in the foreland transitional zone underwent three periods of deformation, i.e., the late Indo-sinian, the Yanshanian, and the Himalayan tectonic movements, and gave rise to the superimposed structures of different periods in the varied direction. It has many types of structural styles such as the fault-propagation fold, the duplex, the imbricate, the tectonic wedge, and the backthrust composition (i.e. pop-up structure), with the faulted-anticline, the faulted-nose, and the fault blocks as the main oil and gas traps. The oil and gas traps are distributed in zonation owing to the fault array. The structural traps are especially well developed in Majiatan area, which is therefore the favorable prospective area for hydrocarbon exploration on the western margin of Ordos basin. |
| HE Deng-fa,SHAO Dong-bo,KAI Bai-ze,BAO Hong-ping,FU Ding-wu,ZHU Hao,MA Jing-hui.2019.Structural Style and Trap Distribution in Majiatan Area on the Western Margin of Ordos Basin[J].Acta Geoscientica Sinica,40(1):219-235. |
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