板块俯冲变形过程二维离散元模拟—对东海陆架盆地成因启示

Two-dimensional discrete element simulation of plate subduction deformation process: An insight into the genesis of East China Sea Shelf Basin

  • 摘要: 俯冲变形作用是板块汇聚过程中存在的构造地质现象,是当前构造地质研究的热点。目前对板块俯冲变形的研究尚不完善,俯冲角度变化对变形过程造成的影响还需进一步研究。位于欧亚板块东南部的中国东海大陆架盆地的构造演化特征及动力学机制与菲律宾板块向欧亚板块的俯冲作用有关。利用构造地质领域中新兴的离散元模拟方法,通过构建离散元模型模拟研究板块俯冲变形演化过程,并将实验结果与菲律宾板块向中国东海俯冲部位地层相比较,结果表明:① 板块俯冲变形特征与俯冲角度有关,俯冲角度不同,其最终形成的变形样式也不同;② 断层数目随着俯冲角度的减缓而增加,断层所扩展的水平距离随俯冲角度的减缓而增大,且不同俯冲角度下相同位置所形成的断距不同;③ 俯冲楔高度随着俯冲角度的减缓而增大,地壳变形幅度越大,且最终形成俯冲楔形态类型不同;④ 反冲断层形成时间随着俯冲角度的减缓而越来越晚;⑤ 实验模拟结果与实例具有相似的构造特征。研究结果解析了不同俯冲角度下板块俯冲变形的演化过程,有助于对板块汇聚过程中俯冲变形作用的进一步认识。

     

    Abstract: Subduction deformation is a tectonic phenomenon in the process of plates convergence, which remains a hot topic. The East China Sea Shelf Basin is located in the south-eastern border of the Eurasian plate, whose tectonic evolution and dynamic mechanism are related to the subduction of the Philippine plate and the Pacific plate beneath the Eurasian plate. At present, the research on the subduction deformation is still not so perfect, and the influence of subduction angle changes on the deformation process needs further study. The authors, in this paper, tried to use the method of discrete element simulation, a kind of emerging method in the field of tectonics, to simulate the evolution process of plate subduction deformation. By constructing discrete element models and comparing the experimental results with the strata in the subduction zone between the Philippine plate and the East China Sea, the research shows that (1) The subduction deformation characteristics are related to the subduction angle. Different subduction angles result in different deformation patterns. (2) The number of faults and the horizontal offsets of faults increase as the subduction angle decreases. Fault displacement at the same position under different subduction angles is different. (3) The height of the subduction wedge and deformation degree increases as the subduction angle decreases. And the shape of subduction wedge is different. (4) Back-thrusts form later as the subduction angle decreases. (5) Experimental simulation results have similar structural characteristics with instance. The experimental simulation results may explain the evolution process of plate subduction deformation under different subduction angles, which is helpful to further understand the subduction deformation during plates convergence process.

     

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