青藏高原-天山大陆内部地壳变形三维数值模拟研究  

Three-dimensional mechanical modeling of intracontinental deformation around the tibetan plateau and tienshan regions

作　　者：卢双疆[1] 何建坤[1] 

机构地区：[1]中国科学院青藏高原研究所,北京100101

出　　处：《地球物理学进展》2013年第2期624-632,共9页Progress in Geophysics

基　　金：国家自然科学基金重点项目(No.41030320)资助

摘　　要：大量研究事实证明,板块相互作用除了在板块边缘产生地壳强烈变形外,其应变可以扩展到远离板块边界的大陆内部.对板块相互作用的远程效应以及大陆内部地壳变形的动力学机制目前仍然有争议.本文结合前人对大陆岩石圈流变学研究的知识和现代GPS观测结果,应用三维有限元数值模拟技术探讨了印度大陆向北推挤与青藏高原-天山地壳变形的动力学关系.模拟地壳的流变学用Maxwell黏弹性模型近似,印-藏的汇聚速度用大量GPS观测的速度边界约束,而欧亚大陆内的远程边界用弹簧约束.在重力方向上,模型考虑了重力加载和位于深部的静岩压力边界.通过大量模型的计算,在均一的地壳流变学框架下印-藏汇聚的应变使研究区内发生整体隆升;然而当考虑青藏高原,塔里木地块和天山等区域中地壳流变学可能存在的横向不一致时,可以发现印-藏汇聚的应变经青藏高原吸收后可以跃过塔里木导致天山地区的强烈变形.这暗示新生代以来发生在天山地区强烈地壳变形的动力学可能与印-藏汇聚过程中青藏高原-塔里木-天山一带岩石圈流变学存在横向不均一有关.It has been known that except the strain located along the plate boundary, plate interaction can propagate significant strain into the internal of the continent far away from the plate margin. So far, the mechanism related to intraplate deformation in the sense of plate tectonics is not fully understood. Combined with reasonable rheological structure of the continental crust and current crustal movement derived from GPS observations, here we developed a three-dimensional viscoelastic finite element model to explore possible mechanism of the intraplate deformation around the Tiebtan plateau and the Tienshan regions associating with the India-Asia collisional process. The crustal rheology is simplified as Maxwellian media. In the model, the southwest boundary is specified with GPS velocity field relative to the stable Eurasian plate, on the other sides of the model, the spring boundary conditions are used to mimic far-field effect of the modeled region. On the gravitational direction, gravity loading is considered, with the model base as a hydrostatic pressure boundary. By testing a numerous models with variable parameters, our results show that if the rheological structure from the Tibetan plateau to the Tienshan region is laterally homogeneous, the modeled uplifting would represent in a same pattern. However, if the lateral variation of crustal rheology is considered, modeling results predict that on the north and south sides of the Tarim block both the Tibetan plateau and the Tienshan can obtain obvious strain, in agreement with the tectonic pattern of the regions as many geologic observations indicated. This suggests that the strong crustal deformation of the Tienshan since the late Cenozoic time may be relevant to the lateral inhomogeneity of the theological structure. We believe that such a result could have valuable implications on understanding mechanism of the intracontinental deformation related to the far-field plate interactions.

关 键 词：印度-欧亚大陆相互作用 大陆内部地壳变形 地壳流变结构 有限元数值模拟 

分 类 号：P541[天文地球—构造地质学] P312[天文地球—地质学]