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1.
根据均衡原理制约的地热计算得到中国西部及邻区岩石圈的温度分布状态,以40、100km和莫霍面深度等温线图的形式表示,同时计算了以1 350℃等温面深度表示的中国西部及邻区的热岩石圈厚度。结果显示:中国大陆西北部地区、哈萨克斯坦东部地区以及上扬子地块、蒙古中西部地区和青藏高原中部的深部地温较低,青藏高原北部、东部以及天山褶皱带中部的深部地温高。在中国西部及邻区范围内,岩石圈厚度在180km以上的地区包括准噶尔盆地,塔里木盆地核心部位,西藏东部、中部以及祁连山地区。上扬子地块(四川盆地)岩石圈厚度为160km或更多,蒙古中西部地区以及哈萨克斯坦东部地区的岩石圈厚度为140～180km。青藏高原东部边缘和藏北地区以及天山中部吉尔吉斯伊塞克湖地区的岩石圈厚度较薄(<140km)。地热计算得到的结果与地震层析成像研究结果之间相互吻合。采用湿的上地幔流变学模型的计算结果表明,青藏高原及其东部边缘、天山褶皱带中部和蒙古中西部地区的岩石圈流变学强度模型为"奶油蛋糕(crèmebrlée)"型,其强度剖面显示强地壳而弱地幔的特点;上扬子地块(四川盆地)、准噶尔盆地、塔里木盆地和哈萨克斯坦东部地区岩石圈流变学强度模型为"果冻三明治(jelly sandwich)"型。 相似文献
2.
大陆动力学研究地球内能量和物质的运动和伴随的信息传播,上地幔中的软流圈是地球内部的物质运动的关键部位之一。由于观测的技术方法少,人类对软流圈内部的地质作用过程所知甚少。在青藏高原,过去地震波三维层析成像的分辨率不高,难以对地壳上地幔构造进行准确的定位。我们收集和整理了地方地震台的数字化观测数据,使地震体波三维层析成像的准确度大大提高,为解决软流圈的地质构造准确成像提供了新的可能性。根据地震体波三维层析的成像结果,在古特提斯洋和特提斯洋俯冲板块前沿的软流圈底部410 km间断面上方,存在反映古大洋俯冲板块的高速体,它们在青藏高原、苏鲁和伊朗都有出现。清晰和稳定的高波速异常的位置表明,特提斯洋俯冲板块现在已经拆沉在软流圈的底部,古特提斯洋俯冲板块也可能曾经拆沉在软流圈的底部。对比青藏高原和苏鲁的地壳上地幔波速结构推测,拆沉造成软流圈中的轻元素物质上涌,进入大陆岩石圈,造成岩浆活动。上涌还使碰撞造山带地壳厚度减小,而岩石圈厚度增加。大约100 Ma后,俯冲下去的大洋残块会被软流圈物质磨蚀交代,使岩石圈厚度增加, 形成大陆下方的大陆根,造成大陆克拉通化和体积增生。大洋板块俯冲后在软流圈拆沉是岩石圈—软流圈物质循环的一种重要方式,对软流圈中物质均衡和体积稳定也起重要作用。 相似文献
3.
欧亚大陆及边缘海岩石圈的结构特性 总被引：2，自引：0，他引：2
从地球层块结构的研究思路出发,运用构造解析的理论和方法,对东亚及西太平洋地区人工地震测深和天然地震面波层析成像进行构造解析,发现岩石圈中下部存在形态各异、大小不等的高速块体,结合地质学、地球化学及其他地球物理学标志的综合研究将其称为幔块构造,高速块体或幔块构造是控制东亚西太平洋岩石圈构造格局和岩石圈表层构造变形最基本条件之一。在系统研究该区岩石圈高速块体或幔块构造三维几何结构基础上,建立起东亚西太平洋岩石圈八种三维几何结构型式:克拉通陆根状结构、高原陆根状结构、造山带楔状结构、碎块状结构、香肠状结构、哑铃状结构、藕节状结构和板状结构,以及岩石圈形成与构造演化四种构造类型:克拉通型岩石圈、增厚型岩石圈、减薄型岩石圈和大洋型岩石圈。文章在详细论述岩石圈各结构构造类基本特征的基础上,认为全球最大的青藏高原具有增厚型岩石圈特性,存在大陆根,并且大陆根正在增厚过程中;地震层析成像显示,研究区存在全球最大的东亚大陆巨型裂谷体系,具有减薄型岩石圈特性,新生代晚期东亚大陆巨型裂谷体系被西太平洋沟弧盆体系叠加与改造。根据岩石圈三维结构型式,探讨了岩石圈形成机制与演化模式,东亚大陆边缘岩石圈大规模伸展拆沉减薄作用以及软流圈和地幔物质上涌加热作用与青藏高原岩石圈大规模俯冲碰撞?入增厚作用是东亚大陆及边缘海晚中生代以来地幔动力学最基本的表现型式,从而形成全球最大的青藏高原和全球最大的东亚大陆巨型裂谷体系。 相似文献
4.
长江中下游及其邻区深部地球物理背景与含金夕卡岩矿床的分布 总被引：5，自引：0，他引：5
长江中下游地区是我国重要的铁铜矿产基地。近十年来,我国所发现的含金夕卡岩矿床和铜伴生金夕卡岩矿床也主要产在长江中下游地区。作者借助12条大地电磁测深剖面、5条地震剖面、层析成像速度结构资料、重磁场等区域的和深部的地球物理资料进行综合对比研究,给出长江中下游及其邻区的三维深部构造格架及其与含金夕卡岩矿床和铜伴生金夕卡岩矿床的分布关系。作者认为,上地幔隆起带(岩石圈地幔减薄带)、上地幔异常区(相对低速区)、壳内高导层隆起带、深断裂(岩石圈剪切带)、地壳上地幔不均匀性块体的边缘、重力高反映的基底隆起区、跳跃磁场反映的岩浆岩带和构造交汇处等诸多因素的共同作用控制着含金夕卡岩矿床和铜伴生金夕卡岩矿床的分布。 相似文献
5.
印藏碰撞导致了青藏高原内部及周边地区形成巨量储量的成矿带。虽然这一地区的成矿研究非常深入,但仍然需要
完善对“源-运-储”的综合研究,需要从地壳上地幔结构角度对成矿源的起源进行探索。位于哀牢山剪切带南段的大坪-
长安金矿具有幔源成因迹象,该文研究了该矿区及邻区的岩石圈结构,从深部研究成矿来源。通过接收函数方法获得的研
究区剖面,揭示壳幔边界（Moho） 深度在30~40 km,但在金矿矿区下表现为Moho转换震相强烈横向不连续,表现为东西
两侧约3~5 km的下沉。岩石圈软流圈边界（LAB） 的转换震相揭示,研究区的岩石圈厚度为60~80 km,有效约束了研究区
强烈岩石圈减薄后剩余岩石圈的厚度。金矿区西侧思茅块体的岩石圈厚度最薄,位于前人层析成像工作揭示上地幔顶部一
低速体的上方。金矿区下方的岩石圈厚度为~80 km且LAB的转换震相表现为强烈的横向不连续。金矿下Moho和LAB的横
向不连续暗示了金矿区下方存在岩石圈尺度的岩浆通道,即软流圈的地幔物质可以较快速地到达浅表。笔者认为,研究区
的岩石圈结构支持由俯冲驱动的幔源成矿模型,但大坪-长安金矿矿区下的岩石圈尺度的岩浆通道的形成与哀牢山剪切带
的剪切变形直接相关。由Burma俯冲导致的地幔物质上涌对该通道的形成贡献有限。 相似文献
6.
华南地区岩石圈三维结构类型与演化动力学 总被引：9，自引：0，他引：9
从地球层块结构研究思路出发,对华南及邻区天然地震面波层析成像进行系统地构造解析,发现岩石圈中下部存在形态各异,大小不等的高速块体,结合地质学、地球化学、其它地球物理学标志等多学科综合研究,将其称为幔块构造。研究显示高速块体或幔块构造是华南地区岩石圈构造格局和岩石圈表层构造变形最基本条件之一。首次建立起华南地区岩石圈三种三维几何结构样式:克拉通陆根状结构、造山带楔状结构和碎块状结构,以及岩石圈三类构造演化类型:克拉通型岩石圈、增厚型岩石圈和减薄型岩石圈(弱减薄型岩石圈及强减薄型岩石圈)。本文在论述华南岩石圈三维结构构造类型基本特征基础上,首次探讨了华南地区软流圈三维结构以及该区岩石圈演化动力学特征。 相似文献
7.
通过研究在青藏高原及其部分邻区由三分量宽频地震资料获得的剪切波各向异性的特征，得出了上地幔构造的若干认识，在本区200km以上的上地幔范围内各向异性的方向性变化主要是上地幔物质运移方向的影响，各地体的岩石圈与地壳在相当长时间内是连贯的运移，各向异性的主要方向决定于上地幔承受的主应力剪切作用方向常常与地表的山系和构造方向不一致，最强的各向异性特征出现在高速体地体边缘，与深部热的地幔物质有关，在各地体边缘的走滑断裂附近各向异性与断裂带走向一致。 相似文献
8.
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. 相似文献
9.
重力异常小波多分辨分析分解阶次的确定 总被引：5，自引：0，他引：5
分解阶次的确定是重力异常小波多分辨分析中的基本问题之一.以塔里木及天山地区布格重力异常数据为例, 通过讨论信号长度、小波母函数的支撑长度与分解阶次的关系, 以及对比分解结果与大地水准面异常的特征, 提出了分解阶次的确定方法.发现对于该重力异常数据, 使用bior3.5小波, 5阶小波分解细节可以避免小波母函数特征过多的干扰, 其结果与相应大地水准面异常特征比较吻合, 而6阶小波分解细节结果却与相应大地水准面异常特征存在较大差异.从信号处理和重力异常的地球物理意义两方面表明, 恰当的小波分解阶次为5阶, 更高阶次的分解结果并不合理.所使用的方法对重力异常小波分解阶次的确定是有效和易行的, 为小波分析在重力场数据处理中的应用, 进行了新的有益探索. 相似文献
10.
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
11.
M.J.N. Remkes 《地学学报》1990,2(6):563-568
Tornographic images of the Mediterranean upper mantle P-wave velocity structure have been used to analyse the gravity potential in the vicinity of the Hellenic subduction zone. The velocity anomalies are assumed to be proportional to density variations according to Birch's law. The effect of the topography on the geoid in the region is also calculated. The results indicate that the upper mantle geoid signal probably has significant amplitudes of several metres, but it correlates poorly with the observed geoid. The geoid calculated from topography correlates well, but has an amplitude that is too large in comparison with the observed geoid. The results show that an improved understanding of the Hellenic subduction zone geoid requires refinement of the Moho topography, so that the effect of this topography can be separated from the upper mantle signature. 相似文献
12.
Lithospheric geoid anomalies record changes in elevation and potential energy experienced by continental lithosphere. Estimates of local isostatic equilibration and potential energy, in tandem with lithosphere-related geoid anomalies, can be used to estimate paleolithospheric thickness, providing a clearer understanding of how and why continental topography is developed. We employ several simplifying assumptions about the crustal and mantle lithosphere density and structure (and readily acknowledge that our results are therefore first-order approximations) to predict the pre-orogenic structure of the lithosphere. At the outset we emphasize that while this approach does not provide an exhaustive evaluation of the deformation mechanism, it does serve to quantify the relative role played by the variations in the crustal and upper mantle components of the lithosphere. In this way we are able to use independent measurement of lithospheric geoid anomalies, current (post-orogenic) elevation and lithospheric structure, and paleoelevation information to estimate topographic development and structural support over time. Application of this technique to the southwestern United States indicates that the uplift of the Colorado Plateau is the result of processes in both the crust and mantle lithosphere and that the lithosphere of the pre-orogenic Southern Basin and Range was thinned relative to the Northern Basin and Range and Colorado Plateau. Although we use the southwestern U.S. as an example, this method can help constrain uplift mechanisms for any region for which the structure and geoid anomaly of the modern lithosphere is well understood. 相似文献
13.
We present a method based on the combination of elevation and geoid anomaly data together with thermal field to map crustal and lithospheric thickness. The main assumptions are local isostasy and a four-layered model composed of crust, lithospheric mantle, sea water and the asthenosphere. We consider a linear density gradient for the crust and a temperature dependent density for the lithospheric mantle. We perform sensitivity tests to evaluate the effect of the variation of the model parameters and the influence of RMS error of elevation and geoid anomaly databases. The application of this method to the Gibraltar Arc System, Atlas Mountains and adjacent zones reveals the presence of a lithospheric thinning zone, SW–NE oriented. This zone affects the High and Middle Atlas and extends from the Canary Islands to the eastern Alboran Basin and is probably linked with a similarly trending zone of thick lithosphere constituting the western Betics, eastern Rif, Rharb Basin, and Gulf of Cadiz. A number of different, even mutually opposite, geodynamic models have been proposed to explain the origin and evolution of the study area. Our results suggest that a plausible slab-retreating model should incorporate tear and asymmetric roll-back of the subducting slab to fit the present-day observed lithosphere geometry. In this context, the lithospheric thinning would be caused by lateral asthenospheric flow. An alternative mechanism responsible for lithospheric thinning is the presence of a hot magmatic reservoir derived from a deep ancient plume centred in the Canary Island, and extending as far as Central Europe. 相似文献
14.
This paper looks at the relation between the time-averaged level of the sea surface and a gravimertic geoid, as determined in coastal areas. Measurements in local regions can now be accurate enough to demonstrate that the geoid and mean sea level are not even parallel to each other, let alone identical. The accuracy and pattern structure of surface gravity data in some shelf seas is comparable with those on land, so that a marine geoid can be derived from surface data without using satellite altimetry. The geodetic objective is then to combine the two to determine sea surface topography. In principle, gravimetric studies provide the absolute datum so that local oceanographic models on the shelf can be combined with sea surface topography models related to the global ocean circulation. In contrast, sea surface topography information near deep ocean coasts must come from external sources and satellite altimetry used to give the gravity data needed to offset the less good coverage by ship-borne gravimetry.Marine Bouguer anomalies enable two specific problems of gravity anomaly patterns near the continent ocean transition to be overcome. The necessary extension of Stokes' condensation reduction is developed and illustrated along a north-south profile from the Mediterranean across the Cote d'Azur. The effect on gravity of deep ocean water introduces a geoid correction in the form of a dipolar ridge whose amplitude at the shore is about 11 cm. In addition to geostrophic currents, a semi-quantitative model for the thermohaline effects on sea surface topography is discussed in relation to sea level differences between the Atlantic and Mediterranean.In considering appropriate algorithms for local geoid computation, Kirby's Iterative Fourier Combination routine for combining altimetry and surface gravity is extended to account for global sea surface topography. The impact of very fast spherical harmonic analysis algorithms is discussed and a simple physical model is given which explains the short coherence lengths found for the global gravity field. This necessary assumption for any local geoid computation was hitherto purely empirical.Finally, the use of land data such as tide gauges, ellipsoidal heights from GPS, and orthometric heights from first order levelling are reviewed as ways of corroborating geodetic estimates of sea surface topography and its relation to levelling datums. Successful examples are given from southern England. 相似文献
15.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》2000,25(4):343-353
Details of the Earth's geoid and gravity fields are summarized and examined. A set of 9274 centerpoints of 5 ° cubes (referred to as bloblets) represents subducted slab locations. This set, developed from reconstructed plate history, was provided by the first author of Lithgow-Berttelloni et. al. [1998] and is the best available estimate of locations of subduction material in the Earth's mantle. Two global mass solutions offered here utilize 1) only those bloblets in the outer 800 km, and 2) only those bloblets in the outer 1400 km. Since each bloblet location represents the center of a 5-degree cube [a larger volume than appropriate for a fragment of subducted lithosphere] it was necessary in the 800 km depth limit model to reduce their density to 0.004 grams/cc, and by increasing bloblet density six times at 797.5 km depth to simulate the piling up of slab material beneath the 670 km boundary. The 1400 km depth limit model [commensurate with evidence of slab penetration into the lower mantle from seismic tomography] required estimating densities for the bloblets at nine different mantle depths. An additional four point-masses at 3000 km depth (to simulate CMB topography, unrelated to dynamic topography) completes the mass models. Both these models show reasonable agreement to patterns and magnitudes for degrees 2–10, 3–10, 4–10, 2–3, 3, and 2 geoid fields with both geometric and hydrostatic flattening. These models support an assessment that topography at the core mantle boundary (CMB) may be produced by processes within the core rather than from within the mantle. Possible causes for the CMB topography are discussed. 相似文献
16.
对凤凰─茶陵地学断面重力异常,根据爆炸地震测深资料,确定密度分层,用变密度水平梯形体构制剖面密度模型,计算理论重力异常和实测布格重力异常吻合较好。根据剖面密度模型,可以合理地解释布格重力异常。并将地壳划分为沉积盖层、变质岩层、麻粒岩层三层结构,分别计算三层的重力效应曲线及上地幔低密度体重力效应曲线。还计算了莫霍面起伏引起的重力异常曲线,分析了引起地壳重力异常的各种因素及特点。 相似文献
17.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》2000,25(1):101-106
The topographic surface is a measure of static equilibrium from the actual density distribution within the outmost Earth's lithosphere. The natural height reference of this surface, known as geoid, reflects the mixed mass-density effects, caused by the same sources, without the contribution of topographic mass. Geoid undulation and topography are output signals, which carry in common a large part of the contribution from the causal “sources”. This contribution appears in both types of signal. Comparisons between the signals depict the geographical location and an estimation of the depth occurrence of areas with geophysical and tectonic formations depending on their correlation rate. We present results from the Greek region, known for its complex diversity in topography, tectonics and dynamics. The tests are in point and “surface” concept, from local and global signals of geoid and topography. Local geoid is represented at 91 GPS points and EGM 96 coefficients compute its global representation. The topography is point values within the area, and the ETOPO5 5′X5′ data within the geographical frame. 相似文献
18.
对凤凰─茶陵地学断面重力异常，根据爆炸地震测深资料，确定密度分层，用变密度水平梯形体构制剖面密度模型，计算理论重力异常和实测布格重力异常吻合较好。根据剖面密度模型，可以合理地解释布格重力异常。并将地壳划分为沉积盖层、变质岩层、麻粒岩层三层结构，分别计算三层的重力效应曲线及上地幔低密度体重力效应曲线。还计算了莫霍面起伏引起的重力异常曲线，分析了引起地壳重力异常的各种因素及特点。 相似文献
19.
月球重力探测一直是国际深空探测的重要目标之一。计算月球重力发现,月球表面存在重力异常区域——质量瘤。通过对质量瘤的特征、成因以及研究方法进行概述总结,认为质量瘤是月幔隆升、高密度物质聚集所致,后期的玄武岩充填可能会增加重力异常,但作用微弱。尽管可以利用月震波分析和月球内部三维密度分布反演新技术,但是基于重力数据和地形资料的研究方法更能高效地对月球的重力场及其特征进行详细研究,高精度的重力场模型可以揭示月球深部构造及层圈形态,进而探索早期月球起源、内部物质演化与运动过程等。该研究方法可为月球和其他类地行星的重力研究提供参考。 相似文献
20.
当人们使用长波长的地震层析数据利用地震波速和密度的实验关系外推而直接计算地球大地水准面异常时惊奇地发现，计算大地水准面异常和观测大地水准面异常无论在异常型态或者异常幅度上均相差甚远。因而不能将地幔看做“刚性”地幔，而真实的地幔应当是一“动力”的地幔，它的内部，甚至被看做固体地幔内部也存在物质流动，否则无法解释上述两种水准面的差异。地幔，特别是下地幔远比人们设想的要活跃得多。地幔内部存在一个复杂的热动力系统。全球规模的大尺度对流、上地幔范围的二级对流、层状对流、核－幔边界上部Ｄ″层内很小尺度对流以及地幔热柱形式的对流可能同时存在于地幔之中，它们相互独立又相互影响，而形成多层次、多形态的运动格局。为了进一步完善、丰富人类对其赖以生存的地球的认识，除了需要建立更为合理的非线性的地幔热动力学模型之外，更加精细的、更加精确的大地测量、地球物理和地球动力学观测资料是必需的。 相似文献