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岩石圈流变结构是控制大陆碰撞造山的重要因素.哈山冲断带的构造变形、地表地形与青藏高原周缘冲断带差异较大，指示需要开展地壳流变学研究.本研究采用二维数值模拟，设计了盆山上地壳强度横向差异的单因素实验，模拟结果分析表明：若上地壳强度“山弱盆强”,构造变形集中于造山带，断块垂向叠置造成造山带隆升，使地表地形的构造高点位于造山带；若上地壳强度“山强盆弱”,构造变形集中于冲断带和盆地，盆山相互作用造成地表地形的构造高点位于冲断带，而非后陆.本文基于此单因素实验，模拟了哈山冲断带构造演化，发现哈山冲断带晚二叠世发育推覆构造后，构造变形逐渐减弱，扩展方式由前展式变为后展式，基底倾向由向后陆变为向前陆.结合哈山及龙门山的多学科观测资料，本文认为哈山和龙门山冲断带的构造变形、地表地形分别符合地壳强度“山强盆弱”模式和“山弱盆强”模式.研究成果可以为中西部冲断带的地球动力学模型和实验模型的搭建提供一定启示，同时对研究区内构造控藏分析和油气勘探具有指导意义. 相似文献
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《中国科学:地球科学》2015,(6)
地壳俯冲和大陆碰撞是板块构造理论的核心,而认识大陆碰撞造山带的形成和演化,是发展板块构造理论的关键.根据俯冲地壳的性质,业已认识到不同类型的板块俯冲带.根据碰撞块体的性质及其衍生岩石的成分,已经认识到大陆碰撞形成了两种类型的造山带.弧陆碰撞造山带既含有古老地壳物质,也含有新生地壳物质,它们在碰撞后阶段的再造就能够产生不同地球化学成分的岩浆岩.而对于两个相对古老大陆之间的碰撞所形成的造山带来说,碰撞后岩浆作用只是俯冲带古老地壳的再造.碰撞造山带在岩石圈拉张作用下发生活化再造,不仅再造作用在构造体制上具有继承性,而且再造产物岩浆岩在地球化学成分上也具有继承性.因此,研究碰撞后体制下的造山带再造,认识大陆碰撞造山带深部物理化学差异、俯冲地壳性质与碰撞后岩浆岩之间的成因联系,建立碰撞后阶段大陆构造演化的基本规律,是构建大陆动力学体系、发展板块构造理论的关键. 相似文献
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《地震地质》2020,(1)
西秦岭-松潘构造结下地壳黏滞系数的定量化研究是理解青藏高原东缘及东北缘动力过程的基础。为进一步认识该区域岩石圈动力学的演化过程,建立下地壳流与不同时间尺度岩石圈变形特征的相互联系,文中以下地壳管道流模型为基础,利用地貌形态估算下地壳的黏滞系数,探讨深部岩石圈流变学过程如何作用于上地壳形变和构造地貌特征;同时结合GPS速度场分析现今的地壳形变,进一步研究区域弥散构造变形过程。结果表明:1)若尔盖-红原盆地北侧及东北侧下地壳的黏滞系数小于东侧及东南侧; 2)下地壳流具有向NE低黏滞系数区流动的趋势,较好地解释了该区域的造山运动过程、弧形等高线分布及"V"形展布断裂的发育; 3) GPS数据揭示的现今地表运动方向与黏滞系数反演的下地壳历史演化方向一致,说明下地壳与上地壳可能具有良好的耦合特征。研究结果最终为解释不同走向和性质的断裂系发育、造山带形成、宏观地貌发育特征以及深入探讨青藏高原东北缘岩石圈的流变学和隆升动力学提供了依据。 相似文献
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通过地质、地球物理和地球化学资料分析,建立了东秦岭地学断面带地壳二维深度-强度剖面,揭示了该造山带的地壳结构和流变学分层性．脆性的上地壳南薄北厚;中、下地壳包括莫霍面呈现水平流变状态,南端蠕变特征更明显;上地幔流变强度较大其地壳类型是栾川以南为H型地壳,构成中、新生代造山带的核部,具有伸展构造和走滑构造的特征,栾川以北为C型地壳,中、新生代的大陆汇聚带．东秦岭地学断面带整体上看为C-H型地壳,反映了后造山期陆内造山的构造特征．地壳物质为长英质-石英闪长质壳内软层具有低速、高热、强网状反射和低强度蠕变的地球物理特征,是后造山期经过调整的水平流变层. 相似文献
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秦岭造山带上地幔各向异性及相关的壳幔耦合型式 总被引：1，自引：0，他引：1
秦岭是具有复杂地壳结构、经历长期构造演化的复合型大陆造山带.本文通过地震资料精细反演上地幔各向异性,探索秦岭造山带构造演化及成因动力.采用最小切向能量法、最小特征值法和“叠加”分析法求得覆盖秦岭造山带及周边地区41个地震台站的SKS横波分裂结果:快波偏振方向(φ)和快、慢波的时间延迟(δt),据此绘制了秦岭造山带上地幔各向异性图.将已发表的地表GPS观测结果与上地幔各向异性相结合作上地幔变形因素分析,发现秦岭造山带自西向东的上地幔变形因素不是单一垂直连贯变形或地幔流动,而是共存的.同时,其上地幔变形的主控因素有区域性变化.研究表明秦岭造山带西、中部上地幔变形以壳幔垂直连贯变形为主,属壳幔强耦合,东部壳、幔耦合变弱,上地幔变形以简单地幔流动为主控因素.同时,SKS快波偏振方向(φ)于秦岭造山带显示出南缘略向北凸、北缘略向南凸的弧形展布,反映了造山带两侧刚性较强的扬子地块与鄂尔多斯地块旋转与秦岭造山带南北缘弧形流动有关. 相似文献
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南海北部陆缘带构造扩张的深部地球动力学特征 总被引：13，自引：0，他引：13
利用地热学和重力学方法, 计算和分析了南海北部陆缘带岩石圈热结构及流变特征. 研究表明, 南海北部陆缘带岩石圈存在分层变形的物理条件, 上地壳温度比下地壳温度低150~300℃, 而粘滞系数比下地壳高2~3个数量级, 说明上地壳脆性程度较高, 下地壳塑性程度较高. 陆缘带岩石圈之下地幔总体由西北向东南方向流动, 带动北部大陆边缘向洋扩张、离散和断裂解体. 在向洋离散过程中, 由于上地壳温度低、粘滞性大, 下地壳温度高、粘滞性小, 形成低粘滞通道, 在新生代构造扩张活动中, 岩石圈内出现分层变形, 扩张的陆缘发生差异性块断运动、形成陆缘地堑系. 相似文献
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中国大陆西北造山带及其毗邻盆地的地震层析成像 总被引：41，自引：6，他引：35
根据新疆、甘肃、青海和吉尔吉斯斯坦地震台网提供的地震数据,利用地震层析成像法重建了中国大陆西北造山带及其毗邻盆地的地壳上地幔三维速度图像．上地壳造山带大都为高速区,盆地和地陷区的低速显然与较厚的松散沉积层有关．地壳中部东、西天山之间存在低速边界,造山带及青藏高原北部的莫霍面深度较大,盆地和坳陷区的莫霍面相对较浅．上地幔软流层在青藏高原、阿尔泰山、祁连山等地较浅,在塔里木盆地和天山一带较深．地幔热物质有可能在板块碰撞中沿构造边界上升到造山带的底部,它们的动力学性质与中国大陆西北造山带的形成演化有着密切的联系。 相似文献
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岩石圈的流变学是根据岩石在脆性域与孔隙压力有关的摩擦破裂和在延性域的幂律稳态蠕变来估计的。根据几种大陆和大洋岩石圈的岩石学模型,考虑地温分布和地壳厚度的变化,我们作出了几种满足不同地球动力学条件的岩石圈流变学模型。岩石圈的流变学性质与深度的关系在不同的构造区是不同的。一般情况下,大陆岩石圈有一层(在地壳的底部)或两层(在地壳的底部和中部)软的延性层夹在脆性层之间。地球物理参数(地震活动性、地震波速度和电导率)的深度变化与流变学模型相当吻合。我们用岩石圈流变学剖面来分析加拿大东南部的科迪勒拉山的变形大陆边缘和大洋地体的构造形式。这一地区的大型构造特征与推测的流变学构造颇为一致。由于宕石圈流变学结构是明显分层的,该地区产生近水平的脱底作用就不奇怪了。 相似文献
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有限元等数值模拟方法在我国岩石圈构造研究中的应用与发展 总被引：4，自引：4，他引：0
本文综述了二十年来数值模拟方法在我国岩石圈构造研究中的应用与发展状况,主要涉及造山带数值模拟、俯冲带数值模拟、盆地数值模拟、上地幔小尺度对流数值模拟等几方面内容．为了研究中国大陆及其相邻地区的岩石圈三维结构．已经取得许多区域性地质调查和地球物理、地球化学等探测资料．同时以这些探测资料为基础,国内外科学家做了许多以该地区岩石圈构造与演化为研究目的数值模拟工作．可以看出,数值模拟是岩石圈构造与演化研究的有力工具．并已经取得了卓著的成就．这些成果为继续进行岩石圈构造的研究奠定了基础． 相似文献
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岩石圈流变学结构是控制不同构造环境下岩石圈形变的关键因素之一. 随着空间大地测量观测技术的发展, 基于空间大地测量数据的震后形变研究对揭示断裂带内的力学性质和区域性岩石圈流变学结构已成为可能. 该文首先基于岩石力学的摩擦和流变学实验, 对余滑和分布式韧性流的构造物理背景进行了分别阐述, 并介绍了震后形变数值模拟中本构关系和数值模型的发展. 数值模型主要有解析、 半解析和纯数值3类, 涉及的本构关系包括基于速率-状态摩擦准则的余滑以及分布式韧性流中常用的线性流变学模型(麦克斯韦尔体和标准线性固体)和瞬态流变学模型(宏观经验性的伯格斯(Burgers)体和微观幂律流变律). 然后以美国南加州1992年Landers MW7.3地震和1999年Hector Mine MW7.1地震震后形变研究为例, 介绍了震后形变的研究进展. 最后回顾了大陆岩石圈流变学结构的研究进展, 并以震后形变研究中的流变学结构(“三明治模型”和“焦糖布丁模型”)存在的争议为例, 说明了岩石圈流变学结构研究所具有的挑战性. 相似文献
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依据地震波速得到的上地幔温度和气象台站记录的地表温度为约束,结合地表热流和热导率观测数据,利用有限元方法计算了中国大陆及邻区岩石圈三维热结构.基于此温度结果和GPS观测得到的应变率数据,以滑动摩擦、脆性破裂和蠕变三种强度机制为约束,计算得到了中国大陆及邻区岩石圈三维流变结构.结果显示:弱强度和低等效黏滞性系数的下地壳在中国大陆及邻区普遍存在,并且下地壳的流变强度和等效黏滞性系数比上地壳和岩石圈地幔一般要低1~2个数量级;中国大陆范围内青藏高原存在着厚度最大、强度最低的下地壳;青藏高原的岩石圈强度和等效黏滞性系数比华北、华南和印度板块的都要低;岩石圈流变结构的横向分布特征与重力梯度带和地形过渡带比较一致. 相似文献
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LIU Shaowen WANG Liangshu GONG Yuling LI Cheng LI Hua & HAN Yongbing . Department of Urban Resources Nanjing University Nanjing China . Department of Earth Sciences Nanjing University Nanjing China 《中国科学D辑(英文版)》2005,48(10)
Thermal regime of the lithosphere is the scenario of the lithospheric thermal evolution, and the thermo-mechanical state of lithosphere definitively controls its deformation style and mechanism. Better understanding of the lithospheric deep thermal-rheo- logical structure of sedimentary basin will shed light on the formation and evolution dynamic process of the basin. Surface tectonics is the response of the deep structure, and is controlled by the lithospheric ther-mal-rheological properties.… 相似文献
14.
PengPeng Huangfu YueJun Wang WeiMing Fan ZhongHai Li YongZhi Zhou 《中国科学:地球科学(英文版)》2017,60(2):218-234
Numerical experiments are used in this study to systematically investigate the effects of convergence rate, crustal rheological strength, and lithospheric thermal structure on the dynamics of continental collision. The study focuses on the types, conditions and processes of unstable continental subduction. Modelling results suggest that the development of unstable continental subduction can be promoted by conditions that tend to decrease rheological strength of the lithosphere, such as low crustal rheological strength, “hot” thermal structure of the lithosphere, or low convergence rate. Unstable subduction mode can be further categorized into three types: (1) multi-stage slab breakoff, (2) continuously “flowing” of fluid-like slab into the upper mantle, and (3) large-scale detachment of the thickened orogenic root. These three types of unstable continental subduction are respectively associated with (1) a low convergence rate, (2) “hot” thermal structure of the lithosphere with a high convergence rate, and (3) moderate-high crustal rheological strength with a low convergence rate. It is also revealed that the evolution of crustal melting is dominated by the deformation pattern of continental collision, which is mainly controlled by crustal rheological strength. The modelling results have important implications for understanding of continental subduction mode selection under specific geodynamic conditions. 相似文献
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Softening of the subcontinental lithospheric mantle by asthenosphere melts and the continental extension/oceanic spreading transition 总被引：1，自引：0，他引：1
The majority of ophiolitic peridotites in the Alpine–Apennine system show evidence of extensive interaction between subcontinental lithospheric mantle and fractional melts of asthenospheric origin. This interaction led to petrological, structural, and geochemical changes in the lithospheric mantle, and was accompanied by a temperature increase to near-asthenospheric values, resulting in the thermomechanical erosion of the lithosphere. We term the parts of mantle lithosphere thus affected the asthenospherized lithospheric mantle or ALM.The thermal and rheological consequences of thermomechanical erosion are explored by modelling the temperature and rheological properties of the thinned lithosphere as a function of thickness of ALM and time since asthenospherization (i.e., since the beginning of thermal relaxation). Results are given both in terms of rheological profiles (strength envelopes) and total lithospheric strength (TLS) for different lower crustal rheologies. The TLS decreases as a consequence of thermomechanical erosion. This decrease is a non-linear function of the thickness of the ALM. While practically negligible if less than 50% of lithospheric mantle is affected, it becomes significant (up to almost one order of magnitude) if thermomechanical erosion approaches the Moho. The maximum decrease in TLS is achieved within a short time span (1–2 Ma) after the end of the heating episode.As a working hypothesis, we propose that thermomechanical erosion of the lithospheric mantle, related to lithosphere/asthenospheric melts interaction, can be an important factor in a geologically rapid decrease in TLS. This softening could lead to whole lithospheric failure and consequently to a transition from continental extension to oceanic spreading. 相似文献
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根据大地电磁测深结果,东秦岭河南叶县-湖北南漳地区的岩石层由4个电性单元组成,其中华北地块南缘为相对高温的低阻区;秦岭北部为低温的高阻异常区;南秦岭为高温的低阻区,岩石层平均厚度仅80km,南秦岭的南部推覆到扬子地块之上达40-50km;扬子地块为相对低温的中等电阻率区,岩石层厚度150-200km．利用秦岭地区地壳上地幔岩石样品高温高压条件下电阻率的测定结果推断了各单元岩石层内电性层可能的岩石组成类型,并建立了剖面通过地区岩石层的地电模型． 相似文献
17.
岩石圈有效弹性厚度表征了岩石圈抵抗变形的能力,代表了岩石圈的综合强度,通过岩石圈有效弹性厚度的研究能揭示岩石圈丰富的热力学信息.本文收集分布在首都圈地区张家口-塘沽测线附近的16个大地热流数据,且结合该测线下的地壳结构,计算得到测线下方岩石圈的现今温度场剖面,并根据温度场计算得到其流变结构和有效弹性厚度.通过将有效弹性厚度与前人有关该测线下方震源深度的研究成果做对比,结果表明在有热流约束的地方有效弹性厚度大致对应约400~600℃的等温面,所有地震都发生在有效弹性厚度之上. 相似文献
18.
《中国科学:地球科学(英文版)》2017,(3)
The Qinling-Dabie orogen is an important tectonic belt that trends east-west and divides continental China into northern and southern parts.Due to its strong deformation,complicated structure,multiphase structural superposition and the massive exposed high and ultrahigh metamorphic rocks,its tectonic formation and geodynamical evolution are hot research topics worldwide.Previous studies mainly focused on the regional geological or geochemical aspects,whereas the geophysical constraints are few and isolated,in particular on the orogenic scale.Here,we integrate the available P- and S-wave seismic and seismicity data,and construct the rheological structures along the Qinling-Dabie orogen.The results demonstrate that:(1)there are strong lateral variations in the crustal velocity between the western and eastern sections of the Qinling-Dabie orogen,indicating the different origin and tectonic evolution between these two parts;(2) the lateral variations are also manifested in the rheological structure.The rigid blocks,such as South China and Ordos basin(North China Craton),resist deformation and show low seismicity.The weak regions,such as the margin of Tibet and western Qinling-Dabie experience strong deformation and accumulated stress,thus show active seismicity;(3) in the lower crust of most of the HP/UHP terranes the values of P-wave velocity are higher than the global average ones;finally(4) low P- and S-wave velocities and low strength in the lower crust and lithospheric mantle beneath Dabie indicate lithospheric delamination,and/or high temperature,and partial melting condition. 相似文献
19.
Removal or delamination of the lithospheric mantle in a late stage of mountain building is a process often invoked to explain syn orogenic extension, high temperature metamorphism, magmatism and uplift. One mechanism that could explain the lithospheric root detachment is the development of convective instabilities within the peridotitic lithosphere due to its high density. This mechanism is studied by two-dimensional convective numerical simulations in the simple case of a strongly temperature dependent viscous rheology appropriate for upper mantle rocks. We neglect here the weakening effect of a brittle rheology and of a crustal layer, and therefore we did not model tectonic deformations. Depending on the upper mantle viscosity and activation energy, a 300 km thick root can be inferred to be either indefinitely stable or to thicken with time or to thin with time. When the lithosphere is initially thicker than its equilibrium thickness, the convective flow at the base and on the sides of the lithospheric root is strong enough to cancel downwards heat conduction and to progressively remove the root. This flow is due to the finite density perturbations induced by the topography of the isotherms on the base and at the sides of the root. We derive two general parameterizations of the convective removal duration as a function of the equilibrium thickness, the thickening factor, the root width, and the rheological temperature scale. Using these relationships, and assuming that the lithospheric equilibrium thickness is about 100 km, the removal duration of a 250 km thick root ranges from 55 to 750 Myr depending on the root width. It is too small to explain the long term stability of cratonic lithospheric root, but too long to explain any sudden change in the stress and strain states in mountain belts development. 相似文献
20.
Transient creep of the lithosphere and its role in geodynamics 总被引：1，自引：0，他引：1
B. I. Birger 《Izvestiya Physics of the Solid Earth》2012,48(6):496-503
Laboratory experiments with samples of rocks show that at small strains there is transient creep, at which the strain grows with time, and the strain rate decreases. Plate tectonics allows only small strains in the lithospheric plates, so that the lithosphere creep is transient. In geodynamics, the lithosphere is regarded as a cold boundary layer formed by mantle convection. If we assume that the lithosphere has a steady-state creep, which is described by power-law non-Newtonian rheological model, the low effective viscosity of the lower layers of the lithosphere, obtained by data on small-scale postglacial flows, is possible only at high strain rates in these layers. However, the high strain rates in the lithosphere induce large strains that contradict plate tectonics. Transient creep of the lithosphere leads to its mobility at small strains, removing the discrepancy between thermal convection in the mantle and plate tectonics, which holds in the case of power-law rheological model of the lithosphere. 相似文献