塔西南甫沙地区被动顶板双重构造和乌泊尔地区背驮盆地的数值模拟

发布时间：2018-03-18 02:18

本文选题：塔西南　切入点：前陆褶皱冲断带　出处：《地质学报》2017年08期 　论文类型：期刊论文

【摘要】：塔里木盆地西南缘前陆褶皱冲断带发育被动顶板双重构造(甫沙地区)和背驮盆地(乌泊尔地区)两种明显不同的构造类型。为了探讨它们的不同成因,利用有限差分软件FLAC开展了一系列二维数值模拟研究。采用遵循平面应变的黏弹塑性本构模型,设置两个滑脱层和三个能干层。同时考虑基底沉降、同构造剥蚀和沉积,缩短速率为8mm/a,剥蚀速率为每年侵蚀基准面以上高程的3×10-7(相当于每1000m每年剥蚀0.3mm)。在基底水平的情况下,采用均一的沉降速率1.6mm/a并以填平补齐的方式进行沉积时,3.5 Ma后发育成与甫沙地区相似的被动顶板双重构造。而当模型采用中部小两端大的拱形沉降速度以及填平补齐的沉积时最终发育成背驮盆地,和乌泊尔地区地质原型接近。模拟结果表明,同构造沉积地层对褶皱冲断带的影响巨大,当沉积物大量堆积在褶皱冲断带前缘时有利于被动顶板双重构造的形成,而沉积物大量堆积在逆冲楔顶与斜坡时则更有利于背驮盆地的发生。模拟结果认为甫沙地区和乌泊尔地区都接受了填平补齐的沉积方式,但基底沉降差异造成了两者的构造样式明显不同。在小范围内(后陆至前陆小于80km),甫沙地区基底以水平方式发生沉降,褶皱冲断带前缘接受了大量沉积;而乌泊尔地区基底在挤压下发生弯曲,使得后陆发生了更大的沉降从而接受了更多的沉积。
[Abstract]:The Foreland fold thrust belt in the southwest margin of the Tarim Basin has two distinct structural types: passive roof double structure (Fusha area) and piggyback basin (Wubar area). A series of two-dimensional numerical simulation studies have been carried out by using finite difference software FLAC. The viscoelastic-plastic constitutive model following plane strain is used to set up two slippage layers and three energy dry layers. At the same time, the basement subsidence, the same structure denudation and deposition are taken into account. The shortening rate is 8 mm / a, and the denudation rate is 3 脳 10 ~ (-7) per year above the base level (equivalent to 0.3 mm / 1000 m / year denudation). A uniform subsidence rate of 1.6 mm / a was adopted and the sedimentation time was carried out in a uniform manner at 3.5 Ma, which developed into a passive roof dual structure similar to that in the Fusha area. However, when the model adopted the large arch settlement velocity at the middle and small ends of the model, and the filling process was adopted, the model was developed into a passive roof dual structure similar to that in the Fusha area. The deposition of Buqi eventually developed into a piggyback basin. The simulation results show that the sedimentary strata of the same structure have a great influence on the fold thrust zone, and that the accumulation of sediments in the front edge of the fold thrust belt is favorable to the formation of the passive roof double structure. The sediment accumulation on the top of the thrust wedge and on the slope is more favorable to the occurrence of the piggyback basin. However, the difference of basement subsidence resulted in obvious differences in structural styles between them. In a small range (from the back land to the Foreland is smaller than 80 kmg), the basement in the Fusha area is subsided horizontally, and the front edge of the fold thrust belt receives a large number of deposits. However, the basement of Upoer area was bent under compression, which resulted in greater subsidence of the hind land and acceptance of more deposits.
【作者单位】：中国科学院大学地球科学计算地球动力学重点实验室;中山大学地球科学与地质工程学院;
【基金】：中国石油天然气股份有限公司前陆盆地项目(编号:2016B-0501)资助的成果
【分类号】：P542

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