大巴山前陆冲断带构造样式和演化过程的数值模拟

发布时间：2018-08-28 15:47

【摘要】：由于大巴山地区处于独特的构造背景,拥有丰富的油气资源,正吸引人们开展日益深入的研究。本文通过有限差分方法,利用平面应变的二维弹塑性本构模型,对大巴山前陆冲断带开展了系列数值模拟研究。结果表明,前陆区拥有相对软弱的滑脱层(含膏盐岩的中下三叠统),是大巴山前陆冲断带主滑脱面由后陆向前陆逐渐抬升的主控因素。该滑脱层的分布以及同构造沉积的分布限定了主前缘逆冲断裂(镇巴断裂)的位置,通过该断裂,大巴山后陆的强烈缩短应变由深滑脱层(震旦系下部)向南传递至浅滑脱层(三叠系中下统)。镇巴断裂和城口断裂一起,它们的长期活动性,可能调节了大巴山一半以上的总缩短应变。同构造沉积发生后,前陆区浅层侏罗山式褶皱往前扩展的同时,后陆的先成断裂也继续活动并发生顺时针旋转,构成无序逆冲扩展序列。主要断层的逆冲扩展和经典背驮式不同,缩短应变主要由主断层下盘向后陆深部俯冲来实现。模拟结果和大巴山地质原型的近似程度,说明了利用有限差分软件对地质构造进行模拟的可行性。
[Abstract]:Due to its unique tectonic background and abundant oil and gas resources, Daba Mountain area is attracting more and more research. A series of numerical simulations of the Daba Foreland thrust belt are carried out by using the finite difference method and the two-dimensional elastoplastic constitutive model of plane strain. The results show that the Foreland area has relatively weak detachment (middle and lower Triassic containing gypsum salt rock), which is the main controlling factor for the gradual uplift of the main slip surface of the Foreland thrust belt in the Daba Mountains from the post continental forward land. The distribution of the detachment and the distribution of the syntectonic deposits define the location of the main front thrust fault (Zhenba fault) through which, The strong shortening strain of the Dabashan afterland is transferred from the deep slip layer (lower Sinian system) to the shallow slip layer (middle and lower Triassic). Together with Chengkou fault, Zhenba fault and Chengkou fault, their long-term activity may regulate the total shortening strain of more than half of Daba mountain. After the same tectonic deposition, the shallow Jurassic fold in the Foreland region extends forward, while the pre-formed faults of the posterior continent also continue to move and rotate clockwise, forming a sequence of disordered thrust spreading. The thrust propagation of the main fault is different from that of the classical piggyback type, and the strain shortening is mainly realized by the subduction of the main fault footwall to the deep land. The similarity between the simulation results and the geological prototype of Daba Mountain shows the feasibility of using finite difference software to simulate geological structure.
【作者单位】：恒泰艾普石油天然气技术服务股份有限公司;中山大学地球科学与地质工程学院;大港油田勘探开发研究院;中国科学院广州地球化学研究所;
【分类号】：P618.13;P542

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