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1.
中国边缘海域及其邻区的岩石层结构与构造分析 总被引：3，自引：0，他引：3
利用中国边缘海域近年的地震层析成像结果,根据速度异常和各向异性分析东海、黄海和南海北部的岩石层结构和构造,讨论中朝块体和扬子块体在黄海内部的拼合边界(黄海东部断裂带)、东海陆架盆地上地幔异常与岩石层形成演化、南海北部地壳底部高速层的成因及地幔活动等问题。分析表明,黄海东部与朝鲜半岛之间存在一个深部构造界限(大致对应于黄海东部断裂带),分界两侧Pn波速度各向异性存在明显差异,反映不同构造应力和断裂剪切运动作用下的岩石层地幔变形特征。东海陆架下方的低速异常揭示了张裂盆地形成时期的地幔活动痕迹,表明中、新生代期间发生过地幔上涌并造成岩石层减薄,菲律宾海板块向西俯冲引发的地幔活动对东海陆架岩石层的形成、演化产生明显的影响。南海北部岩石层厚度较大并且温度相对偏低,地幔异常仅限于局部地区,估计南海北部大陆边缘的地壳底部高速层形成于张裂发生之前,或者是地壳形成时期壳幔分异时的产物。南海中央海盆的扩张不仅导致地壳拉张,软流层物质上涌,而且也造成岩石层地幔减薄甚至缺失。 相似文献
2.
Tingdong Li 《地学前缘(英文版)》2010,1(1):45-56
<正>The lithospheric structure of China and its adjacent area is very complex and is marked by several prominent characteristics.Firstly,China's continental crust is thick in the west but thins to the east,and thick in the south but thins to the north.Secondly,the continental crust of the Qinghai—Tibet Plateau has an average thickness of 60—65 km with a maximum thickness of 80 km,whereas in eastern China the average thickness is 30—35 km,with a minimum thickness of only 5 km in the center of the South China Sea.The average thickness of continental crust in China is 47.6 km,which greatly exceeds the global average thickness of 39.2 km.Thirdly,as with the crust,the lithosphere of China and its adjacent areas shows a general pattern of thicker in the west and south,and thinner in the east and north.The lithosphere of the Qinghai—Tibet Plateau and northwestern China has an average thickness of 165 km, with a maximum thickness of 180—200 km in the central and eastern parts of the Tarim Basin,Pamir, and Changdu areas.In contrast,the vast areas to the east of the Da Hinggan Ling—Taihang—Wuling Mountains,including the marginal seas,are characterized by lithospheric thicknesses of only 50—85 km.Fourthly,in western China the lithosphere and asthenosphere behave as a "layered structure", reflecting their dynamic background of plate collision and convergence.The lithosphere and asthenosphere in eastern China display a "block mosaic structure",where the lithosphere is thin and the asthenosphere is very thick,a pattern reflecting the consequences of crustal extension and an upsurge of asthenospheric materials.The latter is responsible for a huge low velocity anomaly at a depth of 85—250 km beneath East Asia and the western Pacific Ocean.Finally,in China there is an age structure of "older in the upper layers and younger in the lower layers" between both the upper and lower crusts and between the crust and the lithospheric mantle. 相似文献
3.
龙门山是我国东西构造、地貌分界线的重要组成部分。其两侧的岩石圈结构差异,是形成龙门山造山带的主要原因之一,并对龙门山的构造演化起着持续影响。为了解龙门山两侧壳幔结构差异,本文从重力角度探讨跨龙门山地区的地壳密度结构。我们使用EGM2008模型的重力异常数据,以最新的阿坝-遂宁人工源地震剖面速度模型为基础,得到了龙门山造山带中段及其邻区的精细地壳密度结构。密度结构显示松潘-甘孜地区和四川盆地分别具有软弱和坚硬的下地壳。根据本文所得到的地壳密度结构模型,我们认为龙门山的隆升主要受印度洋板块与欧亚大陆板块的陆-陆碰撞作用影响,强烈的挤压作用使青藏高原物质向东运移,东移物质在青藏高原东缘龙门山地区受到坚硬的四川盆地的阻挡转而向上运移,造成了龙门山的隆升。 相似文献
4.
华北地区岩石圈三维密度分布 总被引：1，自引：0，他引：1
利用华北地区的2°×2°网格S波速度三维层析成像结果和15°×15°的网格平均布格重力异常,采用约束最小二乘方法反演,得到了华北地区岩石圈内6个层面上的密度分布结果.反演结果表明:华北地区岩石圈密度极不均匀,反映了区内强烈的构造活动特征;层内密度分布与大地构造有明显的相关性,不同的构造单元存在着密度差异,断裂带表现为密度异常梯级带;壳内存在着低密度层,华北地区地震的震源深度主要发生在这一深度上,可能与之相关 相似文献
5.
广西地处华南地块、印支地块与西太平洋板块的汇合部位,因特殊的构造部位,广西区内大地构造单元归属、构造单元边界等许多基础地质问题一直存在争议.自新生代以来的板块构造运动对岩石圈的改造,广西地壳与上地幔在地震波速度及温度结构方面具有显著差异.应用卫星重、磁异常数据以及区域重力和航磁资料对广西地区岩石圈密度和磁化率结构及其与上地壳构造的关系开展了研究,结果显示广西地区地壳密度和上地壳磁性结构与现今地表构造较为契合,但下地壳密度结构与上地幔存在不连续现象;此外,岩石圈磁化率结构指示中下地壳存在不同范围和程度的解耦.对广西岩石圈密度与磁性结构的解读认为,在中生代以来岩石圈被大规模改造的背景下,幔源物质上侵至上地壳的规模和范围都有限,这可能是整个广西地区上地幔结构与地壳构造不对应的主要原因. 相似文献
6.
利用中国地震台网和ISC台站记录的P波到时数据,采用球坐标系有限差分地震层析成像方法反演了南海东北部及其邻近地区壳幔三维P波速度结构,并分析了不同地质单元的构造差异及其深部特征。结果表明:南海东北部表现出陆架地区的岩石层特性,属于华南大陆向海区的延伸,岩石层厚度较大,现今不存在大规模的地幔热流活动,推测大陆边缘张裂作用仅限于地壳内部而没有延伸进入上地幔,具有非火山型大陆边缘的深部特点。中央海盆附近上地幔P波速度明显降低,与海盆下方地幔热流活动密切相关。不同的速度异常特征表明:华南大陆暨台湾地区属于欧亚大陆的正常地壳或是与菲律宾海板块相互作用产生的增厚型地壳,冲绳海槽则是弧后扩张产生的减薄型地壳。滨海断裂带作为华南大陆高速异常和南海北部高速异常的分界,代表了一定地质时期华南地块和南海地块的拼合边界。断裂附近的上地幔低速异常揭示了闽粤沿海岩浆作用的深层动力机制。吕宋岛弧、马尼拉海沟、东吕宋海槽的速度异常与其所处的特殊构造位置有密切的关系,清晰地反映出岛弧俯冲带的地壳结构差异;台湾南部至吕宋岛弧的上地幔低速异常揭示了两个重要火山链的深部构造特征,北吕宋海脊下方100 km深度的条带状高速异常有可能代表了俯冲下沉的岩石层板片。 相似文献
7.
Accompanied with rifting and detaching of the north continental margin of the South China Sea,the ernst and the lithosphere become thinner away from the continental margin resulting from the tectonic activities,such as tensile deformation,thermal uplift,and cooling subsidence,etc..Integrated with thermal,gravimetric,and isostatic analysis techniques,based on the seismic interpretation of the deep penetration seismic soundings across the northern margin of the South China Sea,we reconstructed the lithospheric thermal structure and derived the variation of the crust boundary in the east and west parts of the seismic profde by using gravity anomaly data.We mainly studied the thermal isostasy problems using the bathymetry of the profiles and calculated the crust thinning effect due to the thermal variety in the rifting process.The results Indicate that the thermal isostasy may reach 2.5 kin,and the compositional variations in the ilthospheric density and thickness may produce a variation of 4.0 kin.Therefore,the compositional isostatic correction is very important to recover the relationship between surface heat flow and topography.Moreover,because of the high heat flow characteristic of the continental margin,building the model of lithospheric geotherm in this region is of great importan for studying the Cenozoic tectonic thermal evolution of the north passive continental margin of the South China Sea. 相似文献
8.
中国东南地区地质演化复杂,中—新生代构造变形强烈,岩石圈深部热力学状态及其对构造活动的影响有待深入。文章结合最新的大地热流数据与地壳结构Crust 1.0模型,利用稳态热传导方程,以岩石捕虏体温压数据和地震学观测为约束,构建了华南地区扬子克拉通、华夏地块以及南海北缘等不同单元的岩石圈热结构。结果表明该区岩石圈热结构存在强烈的不均一性：除了上扬子地区（四川盆地）为“温壳温幔”的热结构,华南其他大部分地区都表现为“热壳热幔”的特征;同一深度下,华夏地块与南海北缘的深部温度显著高于扬子克拉通;热岩石圈厚度从克拉通内部向沿海地区（NWSE）逐渐降低,也即由四川盆地的~200 km减少到华夏地块的~110 km,再到南海的~70 km。此外,我们还发现陆内地震的分布与岩石圈温度密切相关,地震活动集中分布于600℃等温线以内。总体而言,扬子克拉通中西部岩石圈热结构具有冷而厚的特征,而华夏地块和南海北缘受古太平洋平板俯冲和新生代大陆边缘构造—岩浆作用的改造,表现为热且薄的特征,岩石圈的热弱化进而加速了华南大陆边缘的裂解及随后的南海扩张过程。 相似文献
9.
Based on two-dimensional gravity modeling, the density section of the lithosphere beneath Taiwan and the surrounding areas is constructed. According to the density parameters, the lithosphere of this region comprises both the continental and oceanic types. The continental lithosphere is lighter than the oceanic one and demonstrates insignificant density differentiation through the entire section. The oceanic lithosphere is more contrasting with respect of both the crust and mantle density. The complicated Taiwan density structure corresponding to Taiwan Island is defined to be superimposed on the transition zone between the continental and oceanic lithospheric blocks. This structure with contrasting density boundaries is characterized by the elevated and high density values of its constituting heterogeneities. The formation of the Taiwan density structure is related to geodynamic processes in the Taiwan area marking the collision zone between the Eurasian and Philippine Sea plates. 相似文献
10.
F. Cella S. de Lorenzo M. Fedi M. Loddo F. Mongelli A. Rapolla G. Zito 《Tectonophysics》2006,412(1-2):27-47
The gravity anomaly field of the Tyrrhenian basin and surrounding regions reflects the complex series of geodynamic events active in this area since the Oligocene–Miocene. They can resume in lithospheric thinning and asthenospheric rising beneath the Tyrrhenian Basin, coexisting with the roll-back subduction of the African plate margin westward sinking beneath the Calabrian Arc. The geographic closeness between these processes implies an intense perturbation of the mantle thermal regime and an interference at regional scale between the related gravity effects.A model of the litho-asthenospheric structure of this region is suggested, showing a reasonable agreement with both the evidences in terms of regional gravity anomaly pattern and the results concerning thermal state and petro-physical features of the mantle. The first phase of this study consisted of the computation of the isotherms in the crust–mantle system beneath the Tyrrhenian Basin and, afterwards, of the density distribution within the partially melted upwelling asthenosphere. The second phase consisted of a temperature/density modelling of the slab subducting beneath the Calabrian Arc. Finally, a 21 / 2 interpretation of gravity data was carried out by including as constraints the results previously obtained. Thus, the final result depicts a model matching both gravity, thermal and petrographic data. They provide (a) a better definition of the thermal regime of the passive mantle rise beneath the Tyrrhenian basin by means of the estimation of the moderate asthenospheric heating and (b) a model of lithospheric slab subducting with rates that could be smaller than generally suggested in previous works. 相似文献
11.
青藏高原东北缘岩石圈密度与磁化强度及动力学含义 总被引：4，自引：0，他引：4
利用横贯柴达木盆地南北的格尔木—花海子剖面岩石圈二维P波速度结构以及地震波速度与介质密度之间的关系,建立了该剖面岩石圈二维密度结构与二维磁化强度的初始模型。依据重磁同源原理,在柴达木盆地重、磁异常的二重约束下完成了重磁联合反演,获得了该剖面岩石圈二维密度结构与二维磁化强度分布。结果表明:柴达木盆地地壳厚度沿测线变化较大,平均厚度约60km。在柴达木盆地南缘地壳厚约50km,达布逊湖附近地壳最厚为63km左右,大柴旦附近地壳较薄,为50km左右。柴达木盆地的地壳纵向上可分为三层,即上地壳、中地壳与下地壳。位于盆地中部的中、下地壳分别发育大范围的壳内低密度体,并处于上地幔隆起的背景之上;横向上可将盆地分成南北两个部分,分界在达布逊湖附近。整个剖面结晶基底埋深变化也很大,在达布逊湖附近为12km,在昆仑山北缘基底几乎出露地表。结晶基底的展布形态与地壳底界,即莫霍面呈近似镜像对称。综合研究认为,柴达木盆地的岩石圈结构存在着明显的南北差异,其分界在达布逊湖的北面。在盆地南部,岩石圈介质横向变化较小,各层介质分布正常;在盆地的北侧,岩石圈结构特别在中、下地壳和上地幔顶部横向上发生了变化。壳内低密度体的存在意味着柴达木盆地具有较热的岩石圈和上地幔,加之基底界面与莫霍面的镜像对称分布,形成与准噶尔盆地和塔里木盆地的构造差异。多种地球物理参数所揭示的地壳上地幔结构及其横向变化特点为柴达木盆地构造演化及青藏高原北部边界的地球动力学研究提供了岩石圈尺度的地球物理证据。 相似文献
12.
中国岩石圈的基本特征 总被引：11，自引：2，他引：9
中国及邻区岩石圈结构构造十分复杂,并具有若干明显的特点:中国大陆地壳西厚东薄、南厚北薄,青藏高原地壳平均厚度为60~65 km,最厚达80 km;东部地区一般为30~35 km,南中国海中央海盆平均只有5 km;中国大陆地壳平均厚度为476 km,大大超过全球地壳392 km的平均厚度。中国大陆及邻区岩石圈亦呈西厚东薄、南厚北薄的变化趋势,青藏高原及西北地区岩石圈平均厚度为165 km,塔里木盆地中东部、帕米尔与昌都地区岩石圈厚度可达180~200 km。大兴安岭-太行山-武陵山以东,包括边缘海为岩石圈减薄区,厚度为50~85 km。西部岩石圈、软流圈“层状结构”明显,反映了板块碰撞汇聚的动力学环境;东部岩石圈、软流圈呈“块状镶嵌结构”,岩石圈薄,软流圈厚,反映了地壳拉张、软流圈物质上涌的特点,并在东亚及西太平洋地区85~250 km深处形成一巨型低速异常体。中国东部上、下地壳及地壳、岩石圈地幔之间普遍存在“上老下新”年龄结构。 相似文献
13.
斜切中亚的深部滑移构造带地球物理证据及对表层构造的制约 总被引：1，自引：0，他引：1
斜切中亚的帕米尔一阿尔泰滑移构造带向南延伸，可与恰曼转换断裂系统相接，影响其两侧表层断裂构造格局、中新生代盆山演化、现今地壳变形和地震活动．地球卫星重力异常带在滑移构造带两侧表现出显著的不连续性和系统位移特征，其深部滑移幅度达600km以上．从卫星资料反演计算出的地壳厚度图上可看出，新疆地区地壳厚度比中亚邻区厚4～8hn，岩石圈厚度比中亚邻区厚10-20km，新疆及邻区地震波速层析成像结果提供了不同深度速度结构，在平行于中国西部国界处的10km、30km、50km深处均有NE向速度结构不连续面的反映． 相似文献
14.
Crustal Poisson’s ratio anomalies in the eastern part of North China and their origins 总被引：1，自引：0，他引：1
Seismic tomography can provide both fine P-wave and S-wave velocity structures of the crust and upper mantle.In addition,with proper computation,Poisson’s ratio images from the seismic velocities can be determined.However,it is unknown whether Poisson’s ratio images have any advantages when compared with the P-wave and S-wave velocity images.For the purposes of this study,high-resolution seismic tomography under the eastern part of North China region was used to determine detailed 3-D crustal P- and S-wave seismic velocities structure,as well as Poisson’s ratio images.Results of Poisson’s ratio imaging show high Poisson’s ratio(high-PR) anomalies located in the Hengshan-North Taihang-Zhangjiakou(H-NT-Z) region,demonstrating that Poisson’s ratio imaging can provide new geophysical constraints for regional tectonic evolution.The H-NT-Z region shows a prominent and continuous high-PR anomaly in the upper crust.Based on Poisson’s ratio images at different depths, we find that this high-PR anomaly is extending down to the middle crust with thickness up to about 26 km.According to rock physical property measurements and other geological data,this crustal Poisson’s ratio anomaly can be explained by Mesozoic partial melting of the upper mantle and basaltic magma underplating related to the lithospheric thinning of the North China craton. 相似文献
15.
林舸 《大地构造与成矿学》1990,14(4):305-313
本文综合分析了新疆北部重力场、磁场及地震等资料和邻区地质-地球物理资料,研究了新疆北部地质作用特征。依据岩石圈厚度,上地幔纵波速度和地壳结构等特征,将研究区分为阿尔泰、准噶尔、天山3个岩石圈块体,其间为深断裂带所分割;它们分别与不同发展期的地洼区(阿尔泰地洼区、准噶尔地洼区和天山地洼区)相对应。表明大地构造演化与深部地质作用过程密切相关。 相似文献
16.
《Gondwana Research》2013,24(4):1455-1483
The crust and upper mantle in mainland China were relatively densely probed with wide-angle seismic profiling since 1958, and the data have provided constraints on the amalgamation and lithosphere deformation of the continent. Based on the collection and digitization of crustal P-wave velocity models along related wide-angle seismic profiles, we construct several crustal transects across major tectonic units in mainland China. In our study, we analyzed the seismic activity, and seismic energy releases during 1970 and 2010 along them. We present seismogenic layer distribution and calculate the yield stress envelopes of the lithosphere along the transects, yielding a better understanding of the lithosphere rheology strength beneath mainland China. Our results demonstrate that the crustal thicknesses of different tectonic provinces are distinctively different in mainland China. The average crustal thickness is greater than 65 km beneath the Tibetan Plateau, about 35 km beneath South China, and about 36–38 km beneath North China and Northeastern China. For the basins, the thickness is ~ 55 km beneath Qaidam, ~ 50 km beneath Tarim, ~ 40 km beneath Sichuan and ~ 35 km beneath Songliao. Our study also shows that the average seismic P-wave velocity is usually slower than the global average, equivalent with a more felsic composition of crust beneath the four tectonic blocks of mainland China resulting from the complex process of lithospheric evolution during Triassic and Cenozoic continent–continent and Mesozoic ocean–continent collisions. We identify characteristically different patterns of seismic activity distribution in different tectonic blocks, with bi-, or even tri-peak distribution of seismic concentration in South Tibet, which may suggest that crustal architecture and composition exert important control role in lithosphere deformation. The calculated yield stress envelopes of lithosphere in mainland China can be divided into three groups. The results indicate that the lithosphere rheology structure can be described by jelly sandwich model in eastern China, and crème brulee models with weak and strong lower crust corresponding to lithosphere beneath the western China and Kunlun orogenic belts, respectively. The spatial distribution of lithospheric rheology structure may provide important constraints on understanding of intra- or inter-plate deformation mechanism, and more studies are needed to further understand the tectonic process(es) accompanying different lithosphere rheology structures. 相似文献
17.
Yanghui Zhao Shaoru Yin Jiabiao Li Jie Zhang Hanghang Ding 《International Geology Review》2020,62(7-8):955-969
ABSTRACT The volume of seamounts is an essential indicator of the intensity of mantle convection during the evolution of the oceanic lithosphere. Drilling and dredging samples suggest volcanic seamounts are widely distributed in the oceanic basin of the South China Sea, and most of them were formed after cessation of seafloor spreading. By using an SRTM15_PLUS Digital Elevation Model with a 15-arc-second grid, we developed a spatial filtering method based on the Top Hat Transform to extract seamounts. With a combined analysis of basalt dating results from previous studies and gravity anomaly data, an accurate estimation of seamount volume and its spatiotemporal distribution have been obtained. In addition to an asymmetric distribution of the seamounts with a larger volume in the northern flank, clusters of seamounts can be observed at certain locations in the abyssal plain. Due to the consistency between the distribution of the seamount volume and the seafloor spreading features in the South China Sea basin, we propose the ridge jump may induce additional partial melting zones which account for the larger number of seamounts developed in the northern flank while the re-orientation of the extension during seafloor spreading dominated the distribution of post-spreading magmatism. Similar to other marginal basins, magmas formed by spontaneous partial melting would migrate through weak lithosphere where the extension direction changed, resulting in post-spreading magmatism in those lithospheric weak zones. 相似文献
18.
Regional three-dimensional inversions of teleseismic P-wave travel time residuals recorded by high-frequency regional and local seismic networks operating along the Western Alps and surrounding regions were carried out and lithosphere and upper mantle P-wave velocity models down to 300 km were obtained.
Residuals of more than 500 teleseismic events, recorded by 98 fixed and temporary seismic stations, have been inverted.
The comparison between real residuals and the ones obtained from tomographic model indicates that the method is able to solve the feature of the regional heterogeneities.
Where the resolution is good, coherent lithospheric and upper mantle structures are imaged. In the shallower layers, high- and low-velocity anomalies follow the structural behaviour of the Alpine-Apenninic chains showing the existence of very strong velocity contrasts. In the deepest layers, velocity contrast decreases however two deep-seated high-velocity structures are observed. The most extended in depth and approximately trending NE-SW has been interpreted as a wreck of the oldest subduction responsible of the Alpine orogenesis. The second one, connected to the northwestern sector of the Apenninic chain, appears to vanish at depths greater than 180 km and is probably due to still active Apenninic roots.
Cross-sections depict the spatial trend of perturbations and in particular outline the sub-vertical character of the Alpine and Apenninic anomalies. Under the Ligurian Sea, the 3-D inversion confirms the uplift of the asthenosphere in agreement with the tectonic evolution of the basin. 相似文献
19.
青藏高原及邻区大地水准面异常场源结构 总被引：1，自引：0，他引：1
以青藏高原及邻区地形、地震层析成像、沉积层底面、Moho面及岩石层底面资料为基础 ,讨论了由地形起伏、地球内部各界面以及物质密度不均匀引起的大地水准面异常的计算方法 ,正演计算出青藏高原及邻区岩石圈内部物质不均匀产生的大地水准面异常 ,并把从全阶大地水准面异常中扣除正演模拟得到的岩石圈大地水准面异常与不同阶次波段的大地水准面进行比较 ,以寻求表示青藏高原及邻区地幔物质不均匀的大地水准面异常球谐函数的最佳阶次。结合地震层析成像资料分析结果得出 ,表示青藏高原及邻区下地幔、上地幔及岩石圈物质不均匀的大地水准面异常球谐函数的阶次范围分别为 2 6阶 ,7 60阶和 61 3 60阶。 相似文献
20.
华北地区三类岩石圈的壳幔岩石学结构与化学结构及其大陆动力学意义 总被引：6，自引：0，他引：6
根据地质和地球物理特征表现出的岩石圈不连续，华北地区可区分出鄂尔多斯克拉通型、燕山-太行造山带型和华北平原裂谷型三类岩石圈。依据岩石学方法、壳幔演化模型、造山带形成过程以及地震波速与岩石化学成分之间的关系，建立了华北地区三类型岩石圈的壳幔岩石学结构和化学结构，讨论了不同岩石圈类型的壳幔物质结构、地壳和岩石圈地幔厚度的地质含义、岩石圈不连续在划分岩石圈单元中的作用及不同类型岩石圈形成的大陆动力学意义。 相似文献