共查询到19条相似文献，搜索用时 500 毫秒
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在美国国家科学基金会支持下，美国科学家正在制定一项新的大洋地幔动力学计划，目的是用新一代高分辨率海洋观测设备，检验板块构造和对流的地球动力学模型。板块构造革命为描述固体地球内部动力学过程提供了一个定量的运动学框架。35年来，地质、地球物理、地球化学观测和数 相似文献
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假设地幔地震层析成像数据对应的地幔横向不均匀结构是地幔热对流的结果. 将地震层析成像数据转化为地幔温度(或密度)不均匀分布，考虑热流体动力学的三个基本方程，顾及热输运方程中的非线性项，直接将地震层析成像转化的地幔温度不均匀分布作为内部荷载引入基本方程, 反演计算地幔对流. 本文在利用地震层析成像数据计算地幔对流模型的新理论和方法的基础上，用SH12WM13地震层析成像模型数据，计算了全球地幔对流格局. 结果表明，对流格局不仅依赖地震层析成像数据，而且在很大程度上受地幔动力学框架、热动力参数和边界条件的所确定的系统响应函数的影响. 显示了地幔中复杂的对流格局，特别是区域性层状对流以及多层对流环可能在地幔中存在的现象. 相似文献
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地震层析成像-地幔对流新模型的研究 总被引：4，自引：4，他引：4
利用地震层析成像数据计算地幔对流模型的方法.假设地幔地震层析成像数据对应的地幔横向不均匀结构是地幔热对流的结果,将地震层析成像数据转化为地幔温度不均匀分布.该方法考虑热流体动力学的3个基本方程,以及热输运方程中的非线性项,直接将上述地震层析成像转化的地幔温度不均匀分布作为内部荷载直接引入基本方程,进而反演计算地幔对流的基本格局.理论结果表明,对流格局不仅依赖地震层析成像数据,而且在很大程度上受地幔动力学框架和热动力参数(如Rayleigh数)以及边界条件和系统响应函数的影响. 相似文献
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正在设计新的海底地幔动力学计划以借助新一代海洋高分辨率观测设备检验板块构造和对流的地球动力学模型。革命性的板块构造学说为描述固体地球的动力学过程提供了定量的运动学框架。该革命性学说以来35年的地质学、地球物理学和地球化学观测结果，结合逐步完善的地幔动力学数字模型， 相似文献
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地幔热动力学模型 总被引：5，自引：5，他引：5
地幔,特别是下地幔,远比人们先前的设想活跃.地球物理学、地质学和地球动力学的观测和地球热动力学模拟表明:(1)地幔底部与地核交界处有一厚度为200km 左右的D″层,这是一个非常活跃的区域,它的运动和变化直接与地核的行为有关,仅仅将其看成全地幔对流的以热传导为主体的热边界层是不够的,小尺度的热对流或许主导这一层内部的物质运动,它加热地幔同时又通过热柱将其部分热量输运到地球外层;(2)地幔热柱有可能源于地球初期不均匀的残存堆积,其存储的热量不断地或穿透整个地幔形成热点或消失在软流层中与该层中的次一级对流相耦合;(3)上地幔在670km 深度范围内广泛存在次一级对流体系。其尺度为500—700km 这一对流体系决定了岩石层板块内部的构造和动力活动,其活动周期远比全球规模的板块运动活动周期小得多;(4)全球规模的大尺度全地幔对流与板块构造动力学密切相关。它以不到10亿年左右的时间完成一个周期,它不断地更新地球表层,也搅拌着地幔,同时还输运地球内部的热能向外层空间散发;(5)地幔局部地区层状相互耦合的对流结构在地震层析剖面上有明显的显示,它表明了地幔对流结构的复杂性,仅管我们对此相知甚少,但它或许是无法避免的;(6)岩石层是人类熟知的赖以生存的方舟,它的运动和构造反映了上述所有运动信息,仅仅将其视为一对流体系的热边界层是不够的,它自身作为一个独立的力学单元影响了整个地幔的热动力学过程.因此,面对如此活跃的、复杂的地幔,用一个单一的模型去描述它是不合适的.上述各种热动力学单元及其运动均有自身的力学特征及运行机制和规律,但它们又是相互作用和影响而构成地幔整体,这就是一个真实的但又模糊不清的地幔热动力学模型.为了完善这一模型,需要更多的、细致的地球物理和地球动力学的观测资料以及需要我们更深刻地理解和更认真地解释这些资料的地幔热动力学背景. 相似文献
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这篇综述讨论大空间、大时间尺度的地幔动力学近几十年的发展和现状,着重讨论了相关的观测及其动力学意义.这些观测包括现在地球的板块运动的基本特性,中、长波重力异常及大地水准面异常,地震层析成像得到的地幔结构,以及过去10亿年超级大陆Pangea和Rodinia的形成、裂解和演化,及火山岩浆活动.关于地球动力学模型的讨论是围绕着这些相关的观测而进行的.涉及到的一些主要问题包括以下.第一,地幔动力学研究显示,地震层析成像得到的下地幔的二阶结构(比如核幔边界附近的LLSVP结构),和俯冲带的快速异常体,可以解释为过去1亿年左右的板块运动和地幔对流的结果;第二,地幔三维结构作为地幔对流的驱动力,是导致中、长波重力及大地水准面异常的直接原因;结合地幔动力学模拟,观测的大地水准面异常对地幔黏性结构提供了强有力的约束,很可靠的结果之一是下地幔的黏性比上地幔要高至少一个量级,并且最近的研究确定软流圈的存在;第三,过去10亿年大陆块体经历过的Rodinia和Pangea两期超级大陆的形成和破裂是地幔动力学在地表的反映.地幔结构在Pangea形成过程中是一阶结构(即一个半球是冷的下降流,而另一个半球是热的上涌流)主导的,而现在的二阶为主导的地幔结构是Pangea形成后,破裂前或破裂过程中才形成的;地幔动力学和其他研究支持地幔结构在一阶和二阶间转换的1-2-1模型;第四,板块构造在地球上的起源和动力机制依然是充满争议和不确定的课题,但是这些问题同时也是重要的地球动力学基本问题. 相似文献
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利用地震层析成像数据计算地幔对流模型的方法。假设地幔地震层析成像数据对应的地幔横向不均匀结构是地幔热对流的结果，将地震层析成像数据转化为地幔温度不均匀分布。该方法考虑热流体动力学的3个基本方程，以及热输运方程中的非线性项，直接将上述地震层析成像转化的地幔温度不均匀分布作为内部荷载直接引入基本方程，进而反演计算地幔对流的基本格局。理论结果表明，对流格局不仅依赖地震层析成像数据，而且在很大程度上受地幔动力学框架和热动力参数（如Rayleigh数）以及边界条件和系统响应函数的影响。 相似文献
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地震各向异性能够深刻反映地球内部的动力学机制,将其与板块运动结合起来,研究包括地幔对流甚至地核发电机模式等在内的一系列地球内部动力过程,正逐渐成为地震学与地球动力学研究领域中的热点问题. 相似文献
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《中国科学:地球科学》2016,(3)
硅酸盐地幔中的水是影响地球的气候、宜居性、地球化学演化、地球物理学性质和地球动力学过程等的重要因素之一,也是近20年来国际地球科学研究中的热点和前沿方向.高温高压实验是了解硅酸盐地幔中水的种类、分布、储量和效应等的强有力手段.近年来通过高温高压实验,人们对硅酸盐地幔中水的多种物理、化学和动力学性质及其影响取得了一系列显赫进展,极大地丰富了人们对时间和空间尺度上地球水循环(尤其是深部地球水循环)的认识.本文就硅酸盐地幔中水的研究现状和一些主要认识进行简要评述(偏重于高温高压实验相关的成果),主要包括硅酸盐地幔中水的起源、含量和分布以及水对硅酸盐地幔一些物理-化学性质的影响等方面. 相似文献
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In the kinematic theory of lithospheric plate tectonics, the position and parameters of the plates are predetermined in the initial and boundary conditions. However, in the self-consistent dynamical theory, the properties of the oceanic plates (just as the structure of the mantle convection) should automatically result from the solution of differential equations for energy, mass, and momentum transfer in viscous fluid. Here, the viscosity of the mantle material as a function of temperature, pressure, shear stress, and chemical composition should be taken from the data of laboratory experiments. The aim of this study is to reproduce the generation of the ensemble of the lithospheric plates and to trace their behavior inside the mantle by numerically solving the convection equations with minimum a priori data. The models demonstrate how the rigid lithosphere can break up into the separate plates that dive into the mantle, how the sizes and the number of the plates change during the evolution of the convection, and how the ridges and subduction zones may migrate in this case. The models also demonstrate how the plates may bend and break up when passing the depth boundary of 660 km and how the plates and plumes may affect the structure of the convection. In contrast to the models of convection without lithospheric plates or regional models, the structure of the mantle flows is for the first time calculated in the entire mantle with quite a few plates. This model shows that the mantle material is transported to the mid-oceanic ridges by asthenospheric flows induced by the subducting plates rather than by the main vertical ascending flows rising from the lower mantle. 相似文献
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A wide class of equations is defined for a high pressure and subcritical temperature range of a fluid state whose thermodynamic properties enable the construction of a polytropic model of the mantle. A variant of deep convection equations of the Ogura and Phillips type is substantiated in terms of the polytropic mantle model. The proposed system of the deep convection equations includes fluctuation of the generalized potential temperature, has a quasi-incompressible form, and is transformed into Mihaljan’s system of shallow convection equations with a decrease in the layer depth. This circumstance is of great importance because it validates the use of the same dimensionless parameters as in the shallow convection model. The advantage of the proposed variant of the deep convection equations is its complete conservatism, which allows one to gain constraints on the efficiency of energy conversion in deep mantle processes and the thermal energy power expended on the generation rate of the convection kinetic energy and associated processes. This power is shown to be of the order of half the geothermal flux measured on the Earth’s surface. 相似文献
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The thermochemical model of the authors is shown to be naturally related to the general theory of V.P. Myasnikov. A heterogeneous modification of this homogeneous theory is described in light of the present ideas on the differentiation of the mantle substance at the boundary with the core and its eclogitization during submersion from the outer boundary and at the endothermic phase transition at a depth of 670 km. The Earth’ls evolution from an initial hot state is numerically modeled. The evolution is shown to start with an abrupt mantle overturn followed by a long period of steady evolution. Global mantle overturns recur a few times, gradually weaken, and are transformed into regional avalanches. The spatial configuration of overturns is represented by a predominant funnel-shaped sink and a few (three to five) ascending superplumes, which convincingly explains the causes of the formation of supercontinents, the opening of oceans, and the observed asymmetry of the planet. The times of overturns remarkably correlate with geological data on the existence of supercontinents. The processes of core growth, mantle cooling, and crust formation exhibit a clearly expressed stepwise behavior. The supplementation of the endothermic phase transition by chemical transformations favors the overcoming of the phase barrier between the upper and lower mantle, enhances the nonlinearity of mantle convection, and imparts a heterocyclic pattern to the process of evolution. It is shown that the lower mantle plume of chemical origin is fragmented by the phase transition into parts that, interacting with the thermal convection, generate a system of upper mantle plumes. This modeling provides an explanation of the coeval systems of oceanic plateaus and continental traps observed on the surface. 相似文献
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V. P. Trubitsyn 《Izvestiya Physics of the Solid Earth》2008,44(12):1018-1026
A system of equations for the calculation of thermal convection in a compressible mantle with variable parameters and phase transitions is derived from the general laws of mass, momentum, and energy conservation and thermodynamic relations. Mantle convection is successively calculated in the anelastic liquid, truncated anelastic liquid, mean density, expanded Boussinesq, and Boussinesq approximations. Phase transitions are automatically taken into account with the help of effective thermodynamic parameters determined from general thermodynamic relations. 相似文献
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In this study, from the travel time data recorded in the Tianshan passive seismic array experiment, we present the P-wave velocity structure of the upper mantle down to 660 km along the Kuqa-Kuitun pro-file in terms of seismic tomography technique. Based on the P-wave velocity model, we derive the corresponding 2D upper mantle density model. The 2D small-scale convection of the upper mantle underneath the Tianshan Mountains in China driven by the density anomalies is simulated using the hybrid finite element method combining with the marker-in-cell technique. The main features of the upper mantle convection and the reciprocation between the convection and mountain building are in-vestigated. The results manifest that (1) in the upper mantle underneath the Junggar basin and North Tianshan exists a counterclockwise convection, which scale is ~ 500 km; (2) underneath the Tarim ba-sin and South Tianshan exists a clockwise northward convection, which is relatively weak; (3) the convective velocity at the top of the upper mantle underneath the Tianshan Mountains in China should not be less than 20 mm/a, while considering the dependent of convective velocity on the viscosity; (4) the northward extrusion of the Tarim block plays a key role in the Cenozoic Tianshan mountain building and the present-day tectonic deformation of the Tianshan range is related closely to the upper mantle convection; and (5) the northward subduction of the Tarim block does not influence obviously the up-per mantle convection. 相似文献
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上地幔小尺度对流是控制区域地球动力学过程的主要机制之一,蒙古-贝加尔地区的一些区域动力学过程被认为与上地幔小尺度对流相关.本文目的在于利用重力资料研究蒙古-贝加尔地区的上地幔小尺度对流,并探讨其与构造动力学的关系.基于区域均衡重力异常与上地幔小尺度对流的相关方程,本文利用区域均衡重力异常资料反演了蒙古-贝加尔地区上地幔小尺度对流流场及作用于岩石层底部的应力场.结果显示,蒙古-贝加尔地区地幔流场及对流应力场呈现非常复杂的图像,流场及应力场分布与地表构造具有很好的相关性.西伯利亚地台和蒙古褶皱带下地幔流场和对流应力场均较弱,这与这些地区现今较弱的构造活动性是一致的.贝加尔裂谷区下存在地幔上升流,对流应力场呈拉张状态,但应力场的幅值较小(约8 MPa),表明地幔对流不是贝加尔裂谷开裂的主要控制因素.Hangay高原、阿尔泰和戈壁-阿尔泰下存在地幔上升流,对流应力场为拉张状态,这一方面可能构成Hangay高原隆升的深部动力机制,另一方面,也为Amurian板块西边界划分提供了动力背景. 相似文献
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V. P. Trubitsyn 《Izvestiya Physics of the Solid Earth》2010,46(10):807-816
In the existing kinematic theory of the tectonics of lithospheric plates, the position and the parameters of plates are assigned a priori in the initial and boundary conditions. However, in the self-consistent dynamic theory, the properties of oceanic plates (as well as the structure of the mantle’s convection) should appear automatically as the solution of the differential equations of energy, mass, and momentum transfer for a viscous fluid. In this case, the viscosity of the mantle’s substance as a function of temperature, pressure, shear stress, and chemical composition must be taken from the data of laboratory measurements. In the present work, the results of the numerical solution of the equations of convection are presented in the problem formulation mentioned above on a simple model of heated viscous fluid with properties that correspond to the mantle’s substance. In this case, to reveal the main reason for the generation of plates and their influence on the convection, a number of simplifications are introduced; in particular, temperature variations in the viscosity in the mantle are disregarded. In spite of the undertaken simplifications, the models show how the rigid lithosphere can be split into separate plates immersed in the mantle, how in the course of evolution the sizes of plates and their number can change, and how in this case the ridges and subduction zones can be displaced. 相似文献
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Evolution of the deformation and stress patterns of the East Asia continent under multi-driving force 总被引：1，自引：0，他引：1
Introduction Seismological observation and all kinds of ways of geodesy measurement imply that there is significant correlation between crustal movement and seismic activity (MEI, 1993). Therefore, it is very important to get the materials of the continental crust deformation and the patterns of stress field for the studying of the mechanism and prediction of the continental strong earthquake. Data of the continental deformation and patterns of stress field can be mainly obtained by the follo… 相似文献