造山的高原——青藏高原巨型造山拼贴体和造山类型

青藏高原是一个巨型碰撞造山拼贴体,它的形成与始特提斯、古特提斯和新特提斯洋盆的先后开启、消减、闭合以及古大陆的裂解、诸地体的移动、会聚和拼合有关。造山类型形成于不同时期海(洋)盆俯冲、地体碰撞和陆内会聚的不同阶段。多地体/多岛弧/多弧前海的构架表明,诸多的俯冲型山链可以产生在地体边界的活动陆缘一侧,古特提斯南、北两洋盆的双向俯冲构筑了双向俯冲型山链;碰撞型山链由于地体边界与块体驱动方向的几何学关系形成“正向碰撞型”和“斜向碰撞型”造山类型。“斜向碰撞型山链”与走滑断裂的形成、规模及其运动学直接相关。50~60Ma印度/亚洲碰撞不仅形成青藏高原造山拼贴体的最后成员———喜马拉雅山链,而且在拼贴体的北缘由于陆内俯冲作用使早期形成的山链在整修后又一次崛起。青藏高原的周缘山链铸成屏障与外侧的克拉通相隔。青藏高原巨型碰撞造山拼贴体的形成是亚洲大陆自北往南的增生和造山迁移的生长结果,其所反映的活动长期性、非原地性、俯冲/碰撞/陆内造山类型的多样性、碰撞造山的多期性以及造山的复合叠置性比世界上任何一个复合山链(或造山拼贴体)来得复杂、多彩。     

青藏高原各地体的地壳-上地幔结构及其东西向的变化特征

青藏高原是由多个地体拼合而成的,在印度板块向北俯冲的长期作用下,各地体被挤压,地壳缩短,高原隆升。尽管在北北东向挤压作用下发生了高原的近南北向的断裂活动,但各地体本身的结构整体上保持相对稳定,不仅地壳浅部的地层、岩石、古生物保持着各自的特征,而且深部Moho面的变化和岩石圈的特征也是相似的。青藏高原的相距500km以上的2条宽频地震探测剖面的接收函数结果证实:高喜马拉雅地体、特提斯喜马拉雅地体、冈底斯地体、羌塘地体和巴颜喀拉地体在东西方向上保持着相近的速度特征。这充分说明,印度板块向北俯冲与青藏高原碰撞,引发各地体碰撞造山与高原隆升是地壳和岩石圈的整体构造运动,高原各地体,至少高原腹地仍然保持着大致相同的深部结构,Moho面、岩石圈底界面的深度和产状变化不大。     

青藏高原大陆动力学的科学问题

在初步分析大陆动力学的基本含义及其与岩石圈动力学关系的基础上,提出了青藏高原大陆动力学8个方面的科学问题,其核心科学问题是:青藏高原的形成是印度板块与欧亚板块碰撞的滞后效应还是大陆板内构造过程;青藏高原不同构造演化阶段是否具有不同的动力学机制;解体的青藏高原岩石圈下地壳何时、何处、如何和为何流动;青藏高原怎样与周边的盆地同步强耦合作用;如何通过青藏高原大陆动力学的创新带动能源、资源、环境、灾害等应用基础理论的创新.     

由地震探测揭示的青藏高原莫霍面深度

全球最新、规模最大的青藏高原造山带是研究陆陆汇聚、板块俯冲和高原隆升等大陆动力学问题的天然实验室。自20世纪50年代至今, 已经积累大量被动源地震观测和主动源地震探测资料用于揭示青藏高原的地壳与上地幔结构, 勾勒出青藏高原的壳幔结构的基本特征。本文在汇总前人工作基础上, 通过对深地震测深、深地震反射剖面和宽频地震观测三种地震方法资料的梳理, 探讨青藏高原的莫霍面深度及其分布特征。结果表明, 青藏高原莫霍面形态复杂, 深度变化很大, 分布总体特征呈现出中间浅, 南部较深, 北部较浅, 西部较深, 东部较浅的趋势, 最深的和最浅的莫霍面可以相差40 km。这种变化趋势记录了印度板块和欧亚板块的相互作用使高原地壳增厚、减薄过程, 并驱使地壳物质由西向东流动。     

青藏高原区域重磁异常的东西向分区及其构造地质特征

自从大陆整合以来作为一个整体的青藏高原继续受着印度板块向北俯冲的影响,也必定不断地改造着原各地体的结构构造,形成了高原整体意义上东西向的差异。这种差异与原本各地体的组成、结构和东西向延伸不一致。这不仅表现在南北向断裂构造跨各单个地体范围的出现,而且,逐步形成了东西的分区。这种分区突出地表现在区域重力与磁场的特征上,这不仅是局部的岩石磁性与密度变化的结果,而且是由于印度板块向北俯冲过程中,在其前缘的不同部位上经受的压力不同,以及地块的隆升与扩张作用的差异造成了高原东西各区段的地壳组分与厚度的变化。青藏高原的南北向断裂构造并非地壳上层的局部断裂,它具有深层的原因。由于印度板块向北推进的过程中不是均匀地齐头并进,而是在帕米尔高原以东的青藏高原范围内存在着推进速度和俯冲深度的差异,随着高原隆升的加剧高原本身出现断裂,自中新生代以来就存在着一定差异,所以南北向的断裂构造比目前地表见到的多些,而且具有较大的深度,Moho面的深度和地壳厚度都受南北向断裂的控制,并形成了区域重磁场的变化。同时,高原的东西向拉张作用也使南北断裂带发育加剧。     

青藏高原地质研究的回顾与展望

青藏高原是世界上最高最大最年青的高原,被国际地学界公认为世界上研究大陆动力学最理想的天然实验室。特提斯的形成演化及高原的隆起是青藏高原地学研究的两大主题,包含了众多引人入胜的重要科学问题。笔者对其中8个科学问题进行了回顾与展望,它们是:青藏高原的前身——特提斯的形成演化;印度-亚洲大陆碰撞;青藏高原壳幔结构与物质组成;青藏巨厚地壳的成因;青藏高原深部物质的横向流动;地幔柱;高原隆升与生长;成矿作用。     

Lithospheric Evolution and Geodynamic Process of the Qinghai-Tibet Plateau:An Inspiration from the Yadong-Golmud-Ejin Geoscience Transect

The Tibet Geoscience Transect (Yadong-Golmud-Ejin) has revealed the basic structures, tectonic evolution and geodynamic process of the lithosphere of the Qinghai-Tibet plateau. The evidence of northward thrusting of the Indian plate beneath the Himalayans on the southern margin and to southward compression of the Alxa block on the northern margin has been found. They were the driving forces causing the plateau uplift. The plateau is a continent resulting from amalgamation of eight terranes. These tenanes are separated by sutures or large-scale faults, and different terranes have different lateral inhomogeneities and multi-layered lithospheric structures. At depths of about 20-30 km of the crust in the ulterior of the plateau there commonly exists a low-velocity layer. It is an uncoupled layer of the tectonic stress; above the layer, the upper crustal slices were thrust and overlapped each other and the rocks underwent brittle deformation, thus leading to shortening and thickening of the upper crust Belo     

Moho Depth of Qinghai-Tibet Plateau Revealed by Seismic Probing

The Qinghai (青海)-Tibet plateau is the newest and biggest orogenic belt in the world and a natural laboratory for researching continental geodynamics, such as continent-continent collision, convergence, subduction, and plateau uplift. From the 1950s to the present, there have been many active-source (deep seismic sounding and deep seismic reflection profiling) and passive-source seismic probing (broadband seismic observations) implemented to reveal the crust-mantle structure. In this article, the authors mainly summarize the three seismic probings to discuss the Moho depth of the Qinghai-Tibet plateau based on the previous summaries. The result shows that the Moho of the Qinghai-Tibet plateau is very complex and its depth is very different; the whole outline of it is that the Moho depth is deeper beneath the south than the north and deeper in the west than in the east. In the Qiangtang (羌塘) terrane, the hinterland of the Qinghai-Tibet plateau, the Moho is shallower than both the southern and the northern sides. The deepest Moho is 40 km deeper than the shallowest Moho. This trend records the crustal thickening and thinning caused by the mutual response between the India plate and the Eurasia plate, and the eastward mass flow in the Qinghai-Tibet plateau.     

青藏高原隆升机制新模式

作为创建大陆动力学理论体系的最佳野外实验室的青藏高原, 涉及当代固体地球科学前沿和热点的许多重大科学问题.迄今为止, 包括板块构造在内的众多模式不能合理地解释青藏高原重要的地质和地球物理现象.本文从下地壳与中上地壳、造山带与沉积盆地的耦合作用出发, 对青藏高原及邻区进行分尺度、分层块、分阶段的构造解析, 提出青藏高原隆升的下地壳层流构造模式, 认为青藏高原地壳增厚和构造隆升是晚新生代由于锡瓦利克盆地、塔里木盆地和四川盆地下地壳的热软化岩石大量流向青藏高原造成的.      

The Crustal Structure and Assembly of Terranes in the Qaidam-Qilian-Beishan Area, Western China

Through a study of the geotransect from Golmud to Ejin Qi published recently, the tectonics of the crust beneath the area from the northern Qinghai-Tibet plateau (Qaidam and the Qilian Mountains) to the border between China and Mongolia and its structure, composition and tectonic evolution have been revealed, and abundant information about the deep structures has been provided. Based on the research into the geotransect, it is suggested that the crust in this area was formed by the assembly of the terranes in different geological stages. Following the formation of the Palaeo-Asian continent, the north part of the corridor of the transect became a part of the huge unifying continent by the end of the Early Permian. In the Mesozoic and Cenozoic, as a result of the compression mainly by the push of the Qinghai-Tibet plateau on the south, the unique crustal structure and geomorphologic features on the northern Qinghai-Tibet plateau were formed. This geotransect together with the Yadong-Golmud geotransect co     

青藏高原的构造分区及其边界的变形构造特征

宏观构造特征的确立对青藏高原隆升和“动力学建模”具有重要意义。青藏高原是由来自塔里木-中朝板块的北昆仑-阿尔金-祁连地体,华南-东南亚板块的南昆仑地体、可可西里-巴颜喀拉地体和冈瓦纳古陆的羌塘地体、冈底斯地体及喜马拉雅地体等3大板块(或古陆)的6个地体经多次裂解、会聚和陆内俯冲作用拼合而成的巨型“会聚-陆内俯冲型”岩石圈块体,它以青藏高原南缘结合带、青藏高原北缘结合带和青藏高原东缘结合带依次与印度岩石圈块体、塔里木-阿拉善-鄂尔多斯岩石圈块体和扬子岩石圈块体相隔。按现今动力学特征,这一巨型岩石圈块体(一级构造单元)又可进一步划分为喜马拉雅、藏北、青南和昆仑-阿尔金-祁连等4个二级构造单元(地块),它们依次以雅鲁藏布江结合带、西金乌拉-金沙江结合带、中昆仑结合带为界。4个地块又可进一步划分为若干以断裂为界的三级构造单元(地体)。组成青藏岩石圈块体的各构造单元处于统一的地球动力学系统,它总的表现为:在印度板块向欧亚板块持续、强烈俯冲和热的、具柔性流变学特征的青藏块体整体向北北东方向移动的区域构造背景上,其南、北两侧的喜马拉雅地块、昆仑-阿尔金-祁连地块分别向冷的、刚性的印度岩石圈块体和塔里木- 阿拉善-鄂尔多斯岩石圈块体不对称逆冲叠覆。位于青藏高原腹部的藏北地块和青南地块,在深部存在大量低速体向上涌动和整体自西向东扩展的区域构造背景上,前者叠置近南北向挤压,形成以南北向断陷带及北西和北东向共轭走滑为主的构造格局,而青南地块除松潘-甘孜地体显示自北而南的逆冲叠覆外,可可西里-巴颜喀拉地体以逐一向东挤出的左行走滑作用为主,以致整个青南地块呈现向扬子岩石圈块体逆冲扩展和向三江构造带平移扩展。因此,就现今动力学而言,青藏高原在随着时间推移、隆升速度不断加快的同时,还逐渐向外缘的刚性地块扩展,即高原面积在不断增大。因此青藏高原的边界具有扩展性质,按扩展机制可区分两类扩展型动力边界:走滑型扩展边界和逆冲型扩展边界。典型的走滑型扩展边界位于青藏高原北缘的阿尔金山和青藏高原东缘的三江地区,青藏高原南缘的动力边界属典型的逆冲型扩展边界,而位于祁连山和龙门山的动力边界兼有逆冲和走滑双重扩展性质。     

从高分辨率地震层析成像看青藏高原软流圈的物质运动

通过分辨率达到0.5°×0.5°×10 km的青藏高原地壳与上地幔三维成像,为研究青藏高原在新生代的动力学作用提供了新的认识.软流圈的波速扰动数据证实,特提斯大洋板块在拆沉后只俯冲到410 km的间断面之上,并不是所有的大洋板块都会俯冲到上地幔底部.这种大洋板块在软流圈拆沉后激发的热流体上涌,造成高原中部大规模的火山喷发,是青藏高原隆升的主要动力来源之一.根据上地幔三维地震层析成像结果定量计算了岩石圈-软流圈界面（LAB）的深度,揭示了软流圈地幔物质的上涌或者岩石圈地块下沉的作用布局,表明青藏高原的东部在新生代动力学作用过程中是一个相对独立的岩石圈地幔块体.      

黑濑川地体源于亚洲大陆东缘何处？

The point at issue: The Kurosegawa Terrane is composed of continental fragments transecting Mesozoic terranes of accretionary complex in Southwest Japan (Fig. 1). It is an attenuated tectonic sliver and considered to be allochthonous with respect to the main part of Southwest Japan. The problem of which continental block in the East Asian continental margin is the source of the Kurosegawa Terrane has puzzled Japanese geologists for many years. Firstly, we try to approach this issue based on the analysis of fusulinacean assemblage in accreted terranes composed of subduction complex in the Pacific Rim. Secondly, by applying the result of this analysis we try to locate the source of the continental fragments of the Kurosegawa Terrane. Thirdly, we try to prove its validity with a new paleomagnetic study.     

The Yadong-Golmud Geoscience Transect in the Qinghai-Tibet Plateau1

Abstract On the basis of abundant geological and geophysical data, 6 terranes have been distinguished on the Qinghai-Tibet Plateau. The plateau is a single integrated lithospheric unit although it is divided into blocks. With Amdo as a boundary, the crust may be divided into two parts with different crustal structures. The struc-ture in the southern part is complex, while that in the northern part is simple, The current study has revealed that 8 factors such as slab subduction, overthrust and superimposition are responsible for crustal shortening and thickening in the region. The uplift of this region is possibly due to northward compression of the Indian plate and southward compression of the Eurasian plate with the former predominating. The compression led to the asthenospheric movements which were also influenced by thermal activity caused by doming at the boundary between the core and mantle.     

青藏高原南部晚新生代板内造山与动力成矿

青藏高原晚新生代构造隆升是板块碰撞成因还是板内造山过程 ,关系到高原形成机制、演化过程以及岩石圈动力学与大陆动力学的关系等一系列重大科学问题。近年来在冈底斯发现多个以斑岩铜矿为主的大型和超大型矿床 ,其成矿时代为 2 0～ 12Ma ,与青藏高原构造隆升时代一致 ,也与笔者10年前以大陆动力学和成矿动力学为理论指导的预测结果吻合。青藏高原南部晚新生代大量的地质、地球物理、矿床等方面的证据根本不支持碰撞造山理论 ,如青藏高原内部伸展边缘逆冲、碰撞与隆升之间时差明显 ,壳内低速层和低阻层发育 ,造山与成盆关系密切 ,板内隆升环境下发生大规模构造变形、岩浆活动和动力成矿等。青藏高原南部晚新生代构造隆升作用是在新特提斯开合转换、碰撞造陆之后 ,在下地壳层流作用的驱动下 ,发生板内造山、地壳增厚、热隆伸展和改造成矿的构造成矿过程 ,大规模的板内金属成矿在 3～ 4Ma以来的均衡隆升、成山过程中进一步改造。     

玉龙—哈巴雪山断块差异隆升的基本特征及其地质灾害效应

青藏高原新生代以来的持续性、阶段性隆升是地球演化过程中重要的地质和环境事件。尤其是晚新生代以来的加速隆升,使青藏高原主体及其周缘地区成为中国大陆地貌的最高一级阶梯。笔者主要从新构造运动条件下青藏高原东南缘玉龙—哈巴雪山断块这样一个典型的第四纪以来断块快速差异隆升的地区出发,通过详细研究该断块的组成以及几何学运动学特征来探讨其隆升机制,并在此基础上进一步研究该快速隆起的地质灾害效应(如地震、崩塌、滑坡和泥石流等)及其对本区地质灾害发育和发展的控制作用,进而得到地球内动力地质作用与重大地质灾害(外动力地质作用)之间存在必然的耦合关系的结论。     

Gondwanaland origin, dispersion, and accretion of East and Southeast Asian continental terranes

East and Southeast Asia is a complex assembly of allochthonous continental terranes, island arcs, accretionary complexes and small ocean basins. The boundaries between continental terranes are marked by major fault zones or by sutures recognized by the presence of ophiolites, mélanges and accretionary complexes. Stratigraphical, sedimentological, paleobiogeographical and paleomagnetic data suggest that all of the East and Southeast Asian continental terranes were derived directly or indirectly from the Iran-Himalaya-Australia margin of Gondwanaland. The evolution of the terranes is one of rifting from Gondwanaland, northwards drift and amalgamation/accretion to form present day East Asia. Three continental silvers were rifted from the northeast margin of Gondwanaland in the Silurian-Early Devonian (North China, South China, Indochina/East Malaya, Qamdo-Simao and Tarim terranes), Early-Middle Permian (Sibumasu, Lhasa and Qiangtang terranes) and Late Jurassic (West Burma terrane, Woyla terranes). The northwards drift of these terranes was effected by the opening and closing of three successive Tethys oceans, the Paleo-Tethys, Meso-Tethys and Ceno-Tethys. Terrane assembly took place between the Late Paleozoic and Cenozoic, but the precise timings of amalgamation and accretion are still contentious. Amalgamation of South China and Indochina/East Malaya occurred during the Early Carboniferous along the Song Ma Suture to form “Cathaysialand”. Cathaysialand, together with North China, formed a large continental region within the Paleotethys during the Late Carboniferous and Permian. Paleomagnetic data indicate that this continental region was in equatorial to low northern paleolatitudes which is consistent with the tropical Cathaysian flora developed on these terranes. The Tarim terrane (together with the Kunlun, Qaidam and Ala Shan terranes) accreted to Kazakhstan/Siberia in the Permian. This was followed by the suturing of Sibumasu and Qiangtang to Cathaysialand in the Late Permian-Early Triassic, largely closing the Paleo-Tethys. North and South China were amalgamated in the Late Triassic-Early Jurassic and finally welded to Laurasia around the same time. The Lhasa terrane accreted to the Sibumasu-Qiangtang terrane in the Late Jurassic and the Kurosegawa terrane of Japan, interpreted to be derived from Australian Gondwanaland, accreted to Japanese Eurasia, also in the Late Jurassic. The West Burma and Woyla terranes drifted northwards during the Late Jurassic and Early Cretaceous as the Ceno-Tethys opened and the Meso-Tethys was destroyed by subduction beneath Eurasia and were accreted to proto-Southeast Asia in the Early to Late Cretaceous. The Southwest Borneo and Semitau terranes amalgamated to each other and accreted to Indochina/East Malaya in the Late Cretaceous and the Hainanese terranes probably accreted to South China sometime in the Cretaceous.     

青藏高原板内地震震源深度分布规律及其成因

青藏高原板内地震以浅源地震为主, 下地壳基本上没有地震, 地震震源多集中在15~40 km的深度范围, 主要在中地壳内, 呈似层状弥散分布.其中30~33 km深度是一个优势层, 与壳内分层有关.总体上青藏高原南、北部的震源面略呈相向倾斜特征.70~100 km深度区间出现了比较集中的震级较小的地震, 可能与壳幔过渡带的拆离作用有关.高原内部的正断层系与板内地震密切相关, 是板内浅源地震的主控构造.总之, 青藏高原地震震源沿着活动的上地壳脆性层与软弱层之间的脆-韧性过渡带分布.这些板内地震活动属于大陆动力学过程, 与板块碰撞和板块俯冲无关.初步认为青藏高原浅层到深层多震层的成因分别是韧性基底与脆性盖层、韧性下地壳与脆性上地壳、韧性下地壳与脆性上地幔的韧-脆性转换、拆离和解耦的产物.      

The Kostomuksha greenstone belt,NW Baltic Shield: remnant of a late Archaean oceanic plateau?

The Kostomuksha greenstone belt consists of two lithotectonic terranes, one mafic igneous and the other sedimentary, separated by a major shear zone. The former contains submarine 2.8 Gyr old komatiite-basalt lavas and volcaniclastic lithologies with trace element and isotopic compositions resembling those of recent oceanic flood basalts [?Nd(T) =+ 2,8, μ.₁= 8.73 (Nb/Th)N= 1.5–2.1 (Nb/La)N= 1.0–1.5]. We suggest that the mafic terrane is a remnant of the upper crustal part of an Archaean oceanic plateau derived from partial melting of a mantle plume head. When the plateau reached the continental margin, it collided with the sedimentary terrane but was too buoyant to subduct. As a result, the volcanic section of the plateau was imbricated and obducted thus becoming a new piece of continental crust. The deeper zones were subducted and disappeared from the geological record.     

http://www.sciencedirect.com/science/article/pii/S167498711400108X

We present three 3D numerical models of deep subduction where buoyant material from an oceanic plateau and a plume interact with the overriding plate to assess the influence on subduction dynamics,trench geometry,and mechanisms for plateau accretion and continental growth.Transient instabilities of the convergent margin are produced,resulting in:contorted trench geometry;trench migration parallel with the plate margin;folding of the subducting slab and orocline development at the convergent margin;and transfer of the plateau to the overriding plate.The presence of plume material beneath the oceanic plateau causes flat subduction above the plume,resulting in a "bowed" shaped subducting slab.In plateau-only models,plateau accretion at the edge of the overriding plate results in trench migration around the edge of the plateau before subduction is re-established directly behind the trailing edge of the plateau.The plateau shortens and some plateau material subducts.The presence of buoyant plume material beneath the oceanic plateau has a profound influence on the behaviour of the convergent margin.In the plateau + plume model,plateau accretion causes rapid trench advance.Plate convergence is accommodated by shearing at the base of the plateau and shortening in the overriding plate.The trench migrates around the edge of the plateau and subduction is re-established well behind the trailing edge of the plateau,effectively embedding the plateau into the overriding plate.A slab window forms beneath the accreted plateau and plume material is transferred from the subducting plate to the overriding plate through the window.In all of the models,the subduction zone maintains a relatively stable configuration away from the buoyancy anomalies within the downgoing plate.The models provide a dynamic context for plateau and plume accretion in Phanerozoic accretionary orogenic systems such as the East China Orogen and the Central Asian Orogen(Altiads),which are characterised by accreted ophiolite complexes with diverse geochemical affinities,and a protracted evolution of accretion of exotic terranes including oceanic plateau and terranes with plume origins.