云南及邻区板块的运动学研究     

周真恒  阚荣举 《地震研究》1993,16(4):410-418

本文以古地磁资料为基础，编制了古地磁纬度变化图，结合地质、生物古地理等资料。重点探讨了扬子板块、滇缅泰板块的漂移、碰撞拼合过程，同时，也探讨了印度板块与欧亚板块碰撞拼合以来云南及其邻区的构造演化。  相似文献   

PS版表面砂目的定量表示及理想值的确定     

魏斌 《测绘学院学报》1993,(2)

本文从定量角度讨论了PS版表面砂目的定量表示方法,并从理论和实际两方面推断、论证了PS版表面砂目的理想值范围。  相似文献   

斜俯冲板块边界变形分配的力学分析   总被引：4，自引：1，他引：4       下载免费PDF全文

石耀霖  王其允 《地球物理学报》1994,37(5):606-612

本文研究斜俯冲板块边界由俯冲的逆掩断层和平行于火山弧的走滑断层所切割出的岩石层窄条的宏观力学状态．分析计算表明，当断层强度小而构造压应力大时，海沟处板块俯冲形成的逆掩断层地震滑动方向与斜收敛板块运动方向将不一致，震源机制反映的主压应力和断层错动方向变得近乎垂直于海沟；板块间的强耦合和大陆板块边缘软弱带的存在为窄条滑动提供了有利条件．给定俯冲倾角和震源机制滑动角的观测值，可以计算逆掩和走滑断层上的有效摩擦系数．计算结果表明，两种断层上的有效摩擦系数一般都不大于０．２，反映或存在着高孔隙水压，或存在断层泥之类弱物质，或两者兼而有之．  相似文献   

华北板内深部构造与区域成矿   总被引：1，自引：0，他引：1  

孙继源  邢集善 《华北地质矿产杂志》1994,9(1):74-86

本文应用深部地球物理资料，认为华北板块的形成经历了早前寒武纪、燕山期及喜马拉雅期。由于华北板块自身及周围板块的相对运动，上地幔岩石圈的不均一性等特点，造成了许多板内构造单元，如阴山板缘带、鄂尔多斯稳定硬块，河－淮活动软块、燕山活动硬块、山西过渡地块、鲁皖相对硬块及秦岭板缘带。笔者还划出了６个金及多金属成矿带，郯庐金刚石成矿带及华北西部金刚石远景带。此外，华北地区的地热田皆为新生代大陆裂谷型，计有河淮大型裂隙地热带及汾渭线状裂谷地热带。  相似文献   

Cenozoic tectonics in the Urumgi-Korla region of the Chinese Tien Shan     

M. B. Allen  B. F. Windley  Chi Zhang 《International Journal of Earth Sciences》1994,83(2):406-416

Cenozoic deformation within the Tien Shan of central Asia has accommodated part of the post-collisional indentation of the Indian plate into Asia. Within the Urumgi—Korla region of the Chinese Tien Shan this occurred dominantly on thrusts, with secondary strike-slip faulting. The gross pattern of deformation is of moderate to steeply dipping thrusts that have overthrust foreland basins to the north and south of the range, the Junggar and Tarim basins, respectively. Smaller foreland basins lie within the margins of the range itself (Turfan, Chai Wo Pu, Korla and Qumishi basins); these lie in the footwalls of local thrust systems. Both the Turfan and the Korla basins contain major thrusts within them; they are complex foreland basins. Deformation has progressively affected regions further into the interior of the Junggar Basin, and propagated into the interiors of the intermontane basins. No unidirectional deformation front has passed across the Tien Shan in the Neogene and Quaternary. An Oligocene unconformity may indicate the time of the onset of the Cenozoic deformation, but most of the Cenozoic molasse has been deposited after the Palaeogene. The rate of deposition in basins next to the uplifted ranges has increased since the onset of deformation. There has been at least about 80 km of Cenozoic shortening across this part of the Tien Shan. Cenozoic shortening is greater in sections of the range further west; these are nearer to the northern margin of the Indian indenter. Cenozoic compression has reactivated structures created by the two late Palaeozoic collisions that created the ancestral Tien Shan. These Palaeozoic structures have exerted a strong control over the style and location of the Cenozoic deformation.  相似文献   

一种反演地幔横向密度差异的方法          下载免费PDF全文

叶正仁 《地球物理学报》1988,31(1):65-72

重力位球谐系数及板块运动速度是两种独立的地球物理观测资料,但二者同时又是地幔内横向密度差异及与之相联系的地幔流动的结果,从而,中长波重力异常与板块运动的观测提供了探索地幔横向非均匀的一条途径。本文根据适合于低雷诺流动的最小粘滞损耗原理,利用张量场及矢量场的标量分解与传播子解的数学方法,将观测的重力位球谐系数和板块运动速度作为约束条件,发展了一种反演地幔横向密度差异的方法。  相似文献   

Forced vibrations of rectangular plates subjected to harmonic loading distributed over a rectangular subdomain     

R. E. Rossi  R. H. Gutirrez  P. A. A. Laura 《Ocean Engineering》2001,28(12)

Quite frequently naval and ocean structural designers confront the problem of a plate or slab which supports a motor or engine which excites, dynamically, the structural element. Very often the excitation is treated as a concentrated force but, obviously, it acts over a finite area. The present study deals with the title problem for several combinations of boundary conditions by means of a variational approach and also using the finite element method. Dynamic displacement and bending moment amplitudes are determined.  相似文献   

Relating rapid plate-motion variations to plate-boundary forces in global coupled models of the mantle/lithosphere system: Effects of topography and friction     

Giampiero Iaffaldano  Hans-Peter Bunge 《Tectonophysics》2009,474(1-2):393

Recent high-resolution models of past plate motions and their comparison with plate motion models inferred from space geodetic techniques reveal a number of short-term variations in global plate velocities over the past 10 Myrs. Such variations serve as powerful probe into the nature and magnitude of plate boundary forces, because they are unlikely to originate from changes in mantle buoyancy forces, which evolve on longer time scales. Here we explore the constraints of the velocity record using a novel coupled modeling-approach of global neo-tectonic simulations combined with realistic plate driving forces obtained from mantle circulation models (MCMs) to arrive at simple global budgets of mantle, lithosphere and plate boundary forces. We focus on three plate boundary systems along the Nazca/South America plate margin, the Aleutian trench and the India/Australia plate boundary to show that gravitational spreading from high topography in the Andes and Tibet contributes substantially to the global plate tectonic force balance and that this contribution is sufficient to explain some 35% of recent velocity changes over the Earth's surface, including among others the observed 30% convergence reduction between the Nazca/South America plates. Our models make a number of specific predictions such as significant lateral variations in plate coupling forces along a given margin revealed by trench-parallel gravity and bathymetry anomalies and the occurrence of large earthquakes, as well as differences by as much as a factor of five from margin to margin. They also support the notion of a relatively young plate boundary separating the India and Australia plates, which has been previously suggested based on independent observations. Importantly, we find that the modeled Nazca/South America convergence reduction explains recent spreading-rate variations in the South Atlantic and South Pacific, which points to the importance of far field effects on the adjacent continents in explaining the spreading record of oceanic basins. Our numerical results demonstrate (a) that detailed budgets of forces acting upon plates can be obtained and (b) support the notion of strong forcing along weak plate boundaries.  相似文献   

Metallogeny of accretionary orogens — The connection between lithospheric processes and metal endowment     

Frank P. Bierlein  David I. Groves  Peter A. Cawood 《Ore Geology Reviews》2009,36(4):282-292

Accretionary orogens throughout space and time represent extremely fertile settings for the formation and preservation of a wide variety of mineral deposit types. These range from those within active magmatic arcs, either in continental margin or intra-oceanic settings, to those that develop in a variety of arc-flanking environments, such as fore-arcs and back-arcs during deformation and exhumation of the continental margin. Deposit types also include those that form in more distal, far back-arc and foreland basin settings. The metallogenic signature and endowment of individual accretionary orogens are, at a fundamental level, controlled by the nature, composition and age of the sub-continental lithosphere, and a complex interplay between formational processes and preservational forces in an evolving Earth. Some deposit types, such as orogenic gold and volcanic massive sulfide (VMS) deposits, have temporal patterns that mimic the major accretionary and crustal growth events in Earth history, whereas others, such as porphyry Cu–Au–Mo and epithermal Au–Ag deposits, have largely preservational patterns. The presence at c. 3.4 Ga of (rare) orogenic gold deposits, whose formation necessitates some form of subduction–accretion, provides strong evidence that accretionary processes operated then at the margins of continental nuclei, while the widespread distribution of orogenic gold and VMS deposits at c. 2.7–2.6 Ga reflects the global distribution of accretionary orogens by this time.  相似文献   

鲁西古生代碳酸盐岩中的垂直缝合线及其在华北板块构造演化中的意义   总被引：2，自引：0，他引：2  

吕洪波 《地质论评》2009,55(4):473-483

笔者在山东省淄博市博山区中奥陶统马家沟群白云岩和上石炭统本溪组石灰岩中识别出垂直缝合线。垂直缝合线都借助于平面X剪节理发育,缝合面上的“牙齿”与缝合面本身多呈斜交状态,其延伸方向代表着变形期最大主压应力轴（σ1）方向。根据垂直缝合面“牙齿”的突出方向判别：以山东博山地区为代表的华北东部地区在古生代中期和末期先后两次受到NNE—SSW方向的水平挤压作用。其中第一次挤压事件与遍布华北东部的中奥陶统—上石炭统（C2—O2）平行不整合抬升相关,而第二次则与华北东部古生代末期的褶皱隆起相联系。本文的研究为垂直缝合线在盆地构造演化研究中的应用提供了良好的研究实例。  相似文献