大巴山前陆冲断带构造样式和演化过程的数值模拟
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Numerical Simulation of Structural Styles and Evolution of the Daba Shan Foreland Thrust Belt
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    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:

    The Daba Shan region with its unique tectonic setting and rich petroleum resources is attracting people’s interest to conduct much in depth research. Based on the finite difference method and the elastic plastic constitutive model with two dimensional plane strain, this study carried out a series of numerical simulations for the Daba Shan foreland and thrust belt. The results show that the foreland area has the relatively weak detachment in the Lower Middle Triassic which includes gypsum and salt, which led to the main decollement surface transferring from the lower stratum in hinterland into the higher stratum in foreland. The distribution of Lower Middle Triassic detachment and syntectonic sedimentation put limitation on the position of the Zhenban Thrust, through which strong shortening strain in the hinterland was transmitted from basal detachment of lower Sinian into higher detachment of Lower Middle Triassic. Long term activity of the Zhenba thrust and Chenkou thrust might have accommodated more than half of total shortening strain of the Daba Shan foreland and thrust belt. After syntectonic sedimentation, the shallow Jura type folds in the foreland area propagated forward while those old faults in hinterland continued to thrust and rotate clockwise, thus forming an out of order thrusting sequence. Propagation of the main thrusts, which is different from classic piggyback mode, has shortening strain resulting from subduction of the footwall of main fault deeply into the backland. The simulation results are similar to the geological prototype of the Daba Shan foreland and thrust belt, illustrating that using finite difference software to simulate geological structure is feasible.

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黄光明,王岳军,赵勇刚,皇甫鹏鹏.2016.大巴山前陆冲断带构造样式和演化过程的数值模拟[J].地质学报,90(4):653-668.
HUANG Guangming, WANG Yuejun, ZHAO Yonggang, HUANGFU Pengpeng.2016. Numerical Simulation of Structural Styles and Evolution of the Daba Shan Foreland Thrust Belt[J]. Acta Geologica Sinica,90(4):653-668.

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  • 收稿日期:2014-08-07
  • 最后修改日期:2015-02-10
  • 录用日期:2016-04-26
  • 在线发布日期: 2016-04-26
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