【作者】 雷显权；

【导师】 陈运平；

【作者基本信息】 中南大学 ， 矿产普查与勘探， 2009， 硕士

【摘要】 大陆动力学是当今固体地球科学研究的前沿领域,其核心问题是大陆构造变形特征及其动力学机制。造山带是大陆变形最强烈、地表形态最明显的构造,因此成为大陆动力学研究的焦点。天山是世界上最活跃的造山带之一,被认为是研究陆内造山运动的天然实验室,开展天山造山带动力学研究有助于加深对陆内造山带形成与演化的认识。本文通过数值模拟的方法对新疆北部天山的地壳运动变形和天山新生代复活造山过程进行了研究,获得了相关结论。1、在全面分析天山地质结构、构造特征的基础上构建了研究区三维模型,以最新的地壳运动GPS观测结果作为约束条件对天山的地壳运动变形进行了数值模拟,获得了81°E以东天山地区现今地壳运动的速度场、形变场和应力场,揭示了研究区地壳的构造变形特征。天山现今地壳水平运动的总体方向为NNE向,由西向东呈现往东偏转的趋势,运动速率由南西往北、往东递减。南部和北部的运动差异导致了天山地壳近南北向的汇聚缩短,缩短速率由西向东逐渐减小,由82°E的7.71mm／year减小至88°E的2.42mm／year。地壳最大主应变为近南北向的压应变,应变率数量级为10-8／year,由西向东递减。山体内部的主压应变大于两侧盆地,表明缩短变形主要为山体所吸收。活动断裂带吸收的缩短量是有限的,在构造变形中更多地起着调节两盘运动的作用。这些特征表明天山近南北向的地壳缩短是不均匀但近似连续性的变形。天山地壳现今的构造应力场以近南北向挤压作用为主,主压应力由西向东逐渐减小。综合分析认为造成研究区即81°E以东天山具有东西差异的地壳缩短变形的直接原因是塔里木地块的顺时针旋转式挤压,准噶尔地块的逆时针旋转也被动地起着一定的促进作用,而地幔对流拖曳力的作用可能是微弱的。2、采用符合岩石在长期力持续作用下的幂律蠕变本构模型正演模拟了天山自新生代复活起始以来24Ma的造山隆升过程,给出了山体隆升的变形图式和一些基本特征。模拟实验表明,地壳内部介质属性和底部边界条件对山体隆升有重要影响。在水平向北的6.5mm／year的持续推挤作用下,天山经过24Ma、地壳缩短156km后形成现今的形态。地壳的变形以缩短和增厚为特征,厚度由初始模型的40km增加至缩短156km后的56km,这直接导致了山体的隆升。山体在造山演化过程中表现为两侧双峰式隆起、中部形成山间盆地的隆升模式。如果不考虑地表剥蚀与沉积作用,在稳定的推挤作用下天山各段将以各自恒定的速率隆升,南、北天山的隆升速率快于中天山。山体相对软弱的介质属性是其隆升的必要条件,山体内部介质的非均匀性和底边界与上边界的不一致运动共同导致了天山隆升形态的差异。更多还原

【Abstract】 Continental dynamics is the frontier field of solid earth science research currently. The kernel problem of continental dynamics is the characteristics of continental tectonic deformation and its dynamical mechanism.As the orogenic belts own the strongest tectonic deformation and the most apparent surface configurations, they had become a focus of continental dynamics research. Tianshan is one of the most active orogenic belts, considered to be the nature laboratory for researching intra-continental orogeny. Dynamics research of Tianshan orogenic belt helps to better understand the formation and evolution of intra-continental orogeny. The paper deals with the crustal movement and deformation and the process of revival orogeny of Tianshan through numerical simulation with the following conclusions.1、A 3-dimension model of research region was set up in the basis of entirely analysing the geological structural and tectonic characteristics of Tianshan and then a numerical simulation of crustal movement and deformation of Tianshan was carried out basing on the model, using the latest GPS observation results of crustal movement as the constraint condition. The paper acquired the velocity field, strain field and stress field of Tianshan east of 81°E and revealed the characteristics of crustal deformation of research region. The dominant direction of curstal horizontal movement is NNE currently, with a gauche trend toward east from west to east. The speed of crustal movement is descending from SW to north and east. The difference of crustal movement between south and north leads to the crustal convergence and shortening of Tianshan near south-north direction and the speed of shortening descends by degree from west to east, changing from 7.71 mm/year in 82°E to 2.42 mm/year in 88°E.The maximum principal strain is compressive strain near south-north direction and the magnitude fo strain rate is 10-8/year, descending from west to east. The principal compressive strain of the mountain body is larger than the bilateral basins, showing that the shortening deformation is mostly absorbed by the mountain body. The shortening deformation absorbed by active fault zones is limited, mainly playing a role of adjusting the movement of two walls of fault in the process of tectonic deformation. All of these show that the crustal shortening near south-north direction of Tianshan is asymmetric but approximately successional deformation. The crustal tectonic stress field of Tianshan mainly is compressive effect near south-north direction and the principal compressive stress descends by degree from west to east. By comprehensive analysis I think that the direct cause of crustal shortening deformation of Tianshan east of 81°E with differences between east and west is the extrusion of Tarim’s clockwise rotation and the Junggar’s anticlockwise rotation also passively takes a promotion effect in the same time, but the effect of the drag force of mantle convection may be weak.2、The process of orogenic uplift of Tianshan from the beginning of revival at Cenozoic was forward simulated by using the power-rule-creep constitutive model by true of the rock’s deformation under the effect of long and persistent force. The deformation pattern and some general characteristics of the uplift of mountain body were presented. Simulation experients show that the interior attribute of crustal medium and the condition of bottom boundary have important influence to the uplift of mountain body. The Tianshan becomes current configuration after 24Ma and 156km of crustal shortening in the persistent extrusion of 6.5mm/year toward north in horizontal direction. The crustal deformation is charactered with shortening and incrassation. The crustal thickness increases to 56km from 40km of original model after 156km of crustal shortening, which is directly responsible for the uplift of mountain body. The uplift model of the mountain body is two-peak uplifting at two sides and intermontane basin forming in middle in the process of orogenic evolution. If not considering the surficial denudation and sedimentation, each part of Tianshan would uplift in a invariable speed respectively under the steady intrusion action but the uplift speed of Southern-and Northern-Tianshan is quicker than Middle-Tianshan. The relative weak medium of mountain body is the necessary condition of uplift. Asymmetric interior mediun of mountain body and inconsistent movement of bottom and upper boundary together result in the difference of uplift configuration of Tianshan.更多还原