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.     

深地震探测揭示的华南地区莫霍面深度

从20世纪70年代以来,在华南地区进行了大量的深地震探测研究.本文通过对华南地区的深地震探测研究的总结和梳理,探讨了华南大陆及其邻近海域的莫霍面变化情况,结果表明:华南大陆莫霍面形态变化较大,总体变化趋势是由西部向东部呈逐渐抬升;华南大陆最深的莫霍面出现在攀西地区北缘,最浅的莫霍面出现在衢州盆地,两者差35 km;华南地区周缘断裂均存在莫霍面错断;华南加里东造山带莫霍面深度浅于台湾造山带;东海边缘海与南海北缘地壳厚度明显不同.这些特征可能指示了不同区域所经历的岩石罔及地壳演化过程不同,其中攀西地区的莫霍而较厚可能同青藏高原物质东流有关,华南造山带的地壳减薄缘于后期遭受的伸展作用,东海及南海的莫霍面深度反映了两者处于不同的陆缘位置,前者为活动大陆边缘,后者为被动大陆边缘.     

深地震探测揭示的西北地区莫霍面深度

从20世纪70年代以来,在我国西北地区进行了大量的深地震探测研究.本文通过对西北地区的深地震探测研究的总结和梳理,探讨了西北地区的莫霍面深度与变化及其地球动力学意义.结果表明:比起我国其他地区,西北地区莫霍面无论是埋深还是形态均变化最大,反映出受印度板块与欧亚板块碰撞远程效应影响,西北地区地壳整体变形强烈.莫霍面最深(约90 km)位于西昆仑与喀喇昆仑构造结合处,最浅处位于准噶尔盆地西缘的克拉玛依(约35.5 km),最深与最浅相差约55 km.在盆山结合部位及大型走滑断裂,如阿尔金断裂、中天山北缘断裂带等均存在莫霍面错断.天山造山带东西段莫霍面深度变化明显,西段深于东段.这些特征指示了中国西北部盆山之间的构造关系、天山造山带西段和东段不同的深部动力学机制以及古老断裂带的活化.     

深地震探测揭示的华北及东北地区莫霍面深度

从20世纪70年代以来,在我国华北及东北地区进行了大量的深地震探测研究.本文通过对该地区的深地震探测研究的总结和梳理,探讨了该区的莫霍面深度与变化及其地球动力学意义.结果表明:华北地区最深的莫霍面出现在内蒙褶皱带内,最浅的莫霍面出现在渤海湾盆地.东北地区最深的莫霍面出现在大兴安岭地区,最浅的莫霍面出现在依兰-伊通断裂带...     

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.      

Studies on the Velocity Structure of Crust-Upper Mantle beneath Eastern Qinghai-Tibet Plateau Using Seismic Tomography

l.IntroductionAteleseismicprofilingwasconductedjointlybytheChineseAcademyofGeologicalSciencesandtheInstitUteofGeophysicsandInnerTectonics,JosephUniversity,France,alongthemainroadfromGonghetoYushuinQinghai,withanarrayof4Othree-componentMinititanstationsandl3one-componentCEISstations,fromJunetoNovember,1998.ThestUdycoversahugearearangingfromthenofthoftheBangong-NujiangFaulttothesouthoftheMid-QilianFault,andfromtheeastoftheQaidamBasintothewestoftheLongmenShanFault,goingthroughSouthQ…     

青藏高原莫霍面的研究进展

本文首先简要回顾了莫霍面的发现，介绍其基本性质，然后对青藏高原莫霍面研究的重要进展进行了评述。在区域尺度上，被动源地震(天然地震)方法研究结果勾勒出青藏高原地壳及岩石圈底部的深部构造轮廓。然而受分辨率的限制，天然地震结果给出的地壳及上地幔结构的细节不足。近年来已经用分辨率达到几千米甚至百米级的主动源地震(包括宽角反射与折射地震和深反射地震)方法，揭示出青藏高原地壳及上地幔的精细结构。本文对近30年来深地震探测获得的青藏高原各个地块的莫霍面深度、壳幔结构和上地幔盖层速度等基本数据进行了较系统的分析，并对青藏高原莫霍面研究存在的有关问题进行了讨论。     

青藏高原地震断裂共轭角分布特征及其大陆动力学意义

青藏高原走滑型地震断裂共轭角的分布范围约为 5 0°～ 110°,总的趋势是随着与喜马拉雅驱动边界距离的增大而减小 ,并具有波状起伏的特征 ,反映多震层内应变随距离的变化。该层共轭角的波状起伏与岩石圈下层的应变起伏相互对应 ,前者滞后于后者 ,表明上层共轭角的变化主要受控于下层应变的波动传播。对于地震断裂共轭角分布特征的研究为多震层应变场的推测提供了新的途径     

Study on the Gravity Field and Deep-Seated Crustal Structure at the North Margin of the Qinghai-Tibet Plateau

1.I~ductionThenorthernmarginoftheQinghai-TibetplateauincludestheAltllnMis.,theQilianMis.,KunlunMis.,theQaidambasinandthesouthernTarimbasin.ThisareaistCctonicallycharacterizedbyintensiveCenozoicdeformationwithcomplicateddeformationalmechedsm(Molnaretal.,1987;Zheng,1991;Culetal.,1994;Ding,1995andXuetal.,1996).Thedeformationalmechanismsincludethrust-napping,strike-slipping,extensionandblockrotation,aswellassimultaneousupliftingandtypicalbasin-rangetectonics(CulandXu,1996).IntermsofCenozoi…     

Slope instability phenomena in permafrost regions of Qinghai-Tibet Plateau, China

Permafrost covers a significant area of the Qinghai-Tibet Plateau. Slope instability problem in the region was often neglected, though it plays important roles in engineering construction and landform processes. In this paper, the slope instability phenomena in the permafrost regions on the plateau are discussed. The slope failures often occur in the forms of thaw-induced landslides and gelifluction. Thaw-induced landslides are closely related to active layer detachment and changes of permafrost conditions. Such landslides include retrogressive flow and thaw slump and are hazardous to engineering constructions. Gelifluction includes deep-seated movement and surface movement. It is an important factor in landform planation because it may spread over a large area and remain active for a long period of time.     

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.     

青藏高原莫霍面形态的重力模拟及其对探讨高原隆升机制的意义

青藏高原是印度板块板欧亚板块碰撞形成的巨大变形带，岩石圈地幔的变形特征对高原的隆或意义重大。本文分析了远震ＰＫＰ走时残差沿高原中部剖面的变化，发现莫霍面的断错在整个高原是普遍存在的；利用人工地震资料作为约束，用重力资料对莫霍面的形态进行了反演模拟，认为岩石圈地幔的断错和叠覆可能是青藏高原隆升的重要机制；最后讨论了板块中部热和密度不均匀性以及地幔流动对青藏高原岩石圈变形的影响。     

青藏高原隆升速率对冻土层形成影响的数值模拟

青藏高原隆升速率是研究者们关注的问题。由于海拔升高引起地表温度降低,形成了现今的青藏高原冻土层。抬升速率不同,冻土层的形成历史和现今状态也会不同,因此,冻土层内可能包含了高原抬升的有关信息。本文用有限元方法计算了同一地点分别用2Ma时间和5Ma时间由1000m抬升到5000m的两种抬升速率下的情景。计算表明快速抬升和慢速抬升形成的冻土层厚度会有一定的差别,慢速抬升时有更长的热传导时间,形成的冻土层略厚,冻土层年龄较老。所以存在通过现今冻土层厚度、温度随深度变化、以及冻土年龄等资料,并在测得冻土准确参数的条件下,有助于估测青藏高原隆升的时间和过程。     

青藏高原构造演化及隆升的简要评述

根据近年古生物区系、岩相古地理、地质构造以及古地磁等的研究,特别是晚古生代－白垩纪古生物区系、分异度指数特征以及古地磁数据等,笔者认为,从晚古生代－白垩纪印度板块和青藏高原之间不存在至今还流传引用的浩瀚深邃宽达６０００－７０００ｋｍ、     

基于遥感数据的青藏高原热环境调查

本文以地球系统科学和地球力学为理论基础,以遥感(RS)、地理信息系统(GIS)、全球定位系统(GPS)为技术支撑,利用亚东-格尔木-锡铁山走廊域的地学剖面实测温度数据和青藏高原MODIS遥感影像数据,分析研究了青藏高原亚东-格尔木-锡铁山走廊域的热环境特征.通过研究表明,研究区域内热环境总体分布规律为中东部最高,东南部次之,西北部最低.     

Characteristics and Zonation of the Cenozoic Volcanic Rocks on the Qinghai-Tibet Plateau

1.IntroductionCenozoicvolcanicrockshavebeenfoundinanumberoflocationsbothintheinteriorofandatthemarginsoftheQinghai-Tibetplateau.TheyhavebeenconsideredtObegeneticallyrelatedtOtheplatCsubduchon.Forexample,cafe-alkalinevolcedcrocksoftheLingzizongFormation(60-50Ma)occultingintheGangdisebelttothenorthoftheYarlungZangbosutUrezonehavebeenregardedtoberelatedwiththenorthwardsubduchonoftheboaplateandthecloseoftheNeo--Tethysocean(Wang,1984).StUdiesalsoindicatethattheseCenozoicvolcwhcrocksaredomina…     

Structural Characteristics of the Basement beneath Qiangtang Basin in Qinghai-Tibet Plateau: Results of Interaction Interpretation from Seismic Reflection/Refraction Data

The studies on configuration, character/property of the basement of Qiangtang basin is helpful for evaluating petroleum and nature gas resources as well as understanding the basin evolvement. Recently a moderate to high-grade metamorphic gneiss rock was found underlying beneath very low metamorphic Ordovician strata in Mayer Kangri to the north of the central uplift. That fact actually proved existence of the crystalline basement just the distribution and structures of pre-Paleozoic crystalline basement still remain puzzle. In recent years a number of active sources deep seismic profiling, to aim at lithospheric structure of northern Tibet and petroleum resources of the Qiangtang basin, had been conducted that make it possible to image the structure of the basement of the Qiangtang. Near vertical reflection profiles, included those acquired previously and those during 2004 to 2008, have been utilized in this study. By through the interaction process and interpretation between the reflection profiles and the wide-angle profile, a model with the detailed structure and velocity distribution from surface to the depth of 20 km of Qiangtang basin has been imaged.Based on the results and discussions of this study, the preliminary conclusions are as follows: (1) The velocity structure section (~20 km) that is interactively constrained by the refraction and reflection seismic data reveals that the sedimentary stratum gently lie until 10 km in the south Qiangtang basin. (2) The basement consists of fold basement (the upper) and crystalline basement (the lower).The fold basement buried at the average depth of 6 km with a velocity of 5.2–5.8 km/s. The shallowest appear at range of the central uplift. The crystalline basement is underlying beneath the fold basement at the average depth of 10 km with a velocity of 5.9–6.0 km/s except near Bangong-Nujiang suture. (3) The high-velocity body at the depth range of 3–6 km of the central uplift is considered as a fragment of the crystalline basement that perhaps was raised by Thermal or deformation. (4) The lower-consolidated fold basement show more affinity of Yangtze block but the crystalline basement seems more approximate to Lhasa terrene in geophysical nature. We have attempted to improve the resolution and reliability by interaction of the active seismic data and prove it effective to image complex basement structure. It will be a potential to process the piggy-back acquisition data and has wide prospects.     

Time Sequence of Himalayan Endogenetic Mineralization on the East Side of the Qinghai-Tibet Plateau

Among the endogenetic deposits in the Sanjiang area and at the west margin of the Yangtze platform, Himalayan deposits are the most important and contribute a large proportion of the resources of superlarge deposits. Among the controlled resources of this region, 84% of copper resources, 67% of Pb-Zn, 31% of Ag, 77% of gold and 24% of tin come from Himalayan deposits on the east side of the Qinghai-Tibet plateau. Himalayan endogenetic mineralization shows a relatively complete sequence evolution in the Sanjiang area and on the west margin of the Yangtze platform. Mineralization is manifested by gold deposits related to K-rich lamprophyre, REE deposits related to alkalic complexes and Cu-Au-polymetallic deposits related to alkaline porphyry. Six sequences of mineralization evolution since 65 Ma B.P. in the Sanjiang area and on the west side of the Yangtze platform can be recognized. Himalayan endogenetic mineralization on the east side of the Qinghai-Tibet plateau reached its peak before the Oligo-cene,     

青藏高原造山带的某些特征

以昆仑中央断裂为界，青藏高原可分为南、北两部分。北部的造山带是在刚性基底地壳上发育起来的。造山前期是裂陷槽发展阶段，并以简间的碰合褶皱成山。造山期后构造变形也简单，以逆冲、叠覆构造为主。南部的造山带是在柔性基底地壳上发育起来的。它的特点是活动性强，经我旋回开、合造山前期出现有连贯性较好的洋盆及两侧广阔的陆缘沉积，造山期后变形复杂，除逆冲、叠覆构造外，出现大量平移断层。这一部的构造格局形成了青藏高原造山带一系列独有的特征。     

A Mechanism for the Building of the Qinghai-Tibet Plateau

l.IntroductionSinceArgand's(l924)recognitionthattheCenozoictectonicsoftheHighAsiaareprincipallytheresultoftheconvergenceofGondwanancontinentalfragmentswithLaurisic,therehasbeenageneralacceptanceoftheviewthattheHimalayasandQinghai-TibetPlateauhavebeenformedbyacollisionbetweentheIndianandTibetcontinentsalongtheIndus-Zangbosuture(MolnarandTapponnief,l975,Sengor,l979;ChenBingwei,l982;DengWanming,l978,HuangJiqing,l954;LoZhongshu,l982;PanGuitangetal.,l984,WangQianshenetal.,l982,Besseetal.…