【作者】 程顺有；

【导师】 张国伟；

【作者基本信息】 西北大学 ， 构造地质学， 2006， 博士

【摘要】 大陆岩石圈结构与组成的非均匀性和动力学机制是国内外大陆动力学研究的主攻前沿领域之一。利用国际最新的地球重力场模型(UTCSR GRACE/GFZ EIGEN-GRACE)和GTOPO 30数字高程模型，笔者首先计算了中国大陆不同球谐阶次大地水准面异常、岩石圈均衡剩余大地水准面异常和水平应力场分布，从岩石圈内多层次均衡角度进行了解释推断；其次，结合地表地质和其它综合地球物理资料，分区段对中央造山系及邻区分析与解释了岩石圈细结构；然后，通过东亚地区地震层析、大地水准面异常和卫星岩石圈磁场、全国重力与航空磁力对比分析，建立了中国大陆及其邻区岩石圈，特别是中央造山系的初步结构框架。最后，探索中国大陆现今应力状态、变形与可能的动力学机制。取得以下新的认识与进展：1．基于岩石圈大地水准面异常、水平应力场和地震层析等地球物理资料综合分析可知，中国大陆及其毗邻地区在特提斯构造基础上，处于西太平洋板块、印度板块和古亚洲洋及其闭合之后环西伯利亚弧形等三大全球构造体系域相互作用、相互影响和相互制约的地幔动力学控制之下，总体大地构造格局是浅部地壳分别沿主要构造边界向外仰冲，深部岩石圈地幔则从西南、东南和北部向中国大陆俯冲会聚，使之整体处于地幔会聚挤压的大地构造背景。2．岩石圈大地水准面异常、水平应力场和P波地震层析等显示，中国东部岩石圈浅层次向东(南)运动，处于相对伸展状态，而深层次高、低速板片向西(北西)叠瓦式俯冲形成挤压构造背景，以部分脱耦(拆离)形式实现不同深度层次之间的调节。中国南方大陆总体上表现为印支—燕山期多岩石圈块体拼合特征。3．中国西部青藏高原及其邻区深部岩石圈地幔处于多块体叠瓦向北俯冲、物质与能量会聚，冷岩石圈下沉的区域。大地水准面异常和P/S速度层析成像显示，印度大陆岩石圈向欧亚大陆的俯冲作用，不只是引起地壳的强烈加厚、隆升和南北向缩短变形，纵向上影响到600km深度，横向上波及到了中国东部和西伯利亚南部。欧亚巨型的大地水准面低正是这一大规模构造过程在全球卫星重力场中的表现。4．扬子克拉通和鄂尔多斯克拉通厚岩石圈根构成了中国东部和西部之间的交接转换带，成为阻挡东/西部物质交换迁移的中流砥柱。现今的扬子克拉通不仅受大区域挤压应力场背景制约，同时其冷而致密的巨厚岩石圈根正在向深部地幔下拽，从而进一步加剧了四周造山带向盆地的逆冲作用，龙门山、华蓥山和八面山分别向川西盆地和川东逆冲就是例证。5．西秦岭—松潘构造结是前述三大构造动力学体系背景上，以勉略—阿尼玛卿古缝合带、龙门山构造带和甘孜—理塘缝合带为边界，华北、扬子地块与青藏高原以不同时代、不同方向、不同性质三向叠加复合与会聚并同时伴随着岩石圈拆沉的三菱柱物质下降区域。地质、地球化学与地球物理研究表明，松潘—甘孜地块具有冈瓦纳大陆的构造属性，在上、下地壳之间(18～21km)深度存在地壳规模的滑脱界面，沿这一地壳规模的拆离界面，西秦岭造山带沿地表的阿尼玛卿—勉略缝合带向南逆冲推覆在松潘—甘孜地块之上，而松潘—甘孜地块沿丹巴弧形断裂又向南逆冲推覆，剖面上构成了地壳规模的双重逆冲推覆构造系统。这一基本格架由印支—早燕山期所奠定。6．最新大地水准面异常、卫星岩石圈磁场和地震层析等显示，欧亚大陆，特别是，中国大陆地壳乃至岩石圈地幔主要被EW、NW、NE和SN向构造所交织分割，形成棋盘格式构造格局。NW、NE两组跨越地表构造单元，形成类共轭剪切构造，表明它们是中国大陆主体拼合之后的陆内变形构造，主要源于上地幔。源于印支期及其以前的南北板块碰撞拼合的EW向构造，中新生代以来持续的陆内俯冲作用继承、新生叠加、并复合(活)前期构造方向，以次级动力学体系受控于深层次的区域性三大构造体系，并逐渐从深部地幔被改造、分解以至于消失。SN向构造是在地壳或岩石圈中被保留下来的古生代构造基础上，后期可能源于深层次甚至下地幔动力学过程的表现。7．中央造山系的岩石圈结构沿走向明显分段。桐柏—大别造山带受SN和NW-SE两个正交方向挤压应力场控制，深部受NNE向构造改造比东秦岭彻底，但地壳内及其底面(Moho)仍显示印支期板块俯冲拼合及其之后陆内俯冲的EW向构造形迹。超高压变质地体的剥露与岩石圈挤压相关。东秦岭造山带受具有高速岩石圈根的扬子和鄂尔多斯两个克拉通SN向强烈会聚作用影响，因而EW向构造特征显著。西秦岭造山带尽管受NW、NE和SN不同深度层次构造的叠加与改造，地壳—岩石圈结构非常复杂，但通过地球物理资料仍能追踪到勉略古缝合带在地壳乃至岩石圈内的构造遗迹，并发现它与阿尼玛卿缝合带相连接。更多还原

【Abstract】 Anisotropism and dynamics for continental lithospheric structure and composition is one of major realms for studying continental dynamics. Based on the summary of newest progresses of global gravity field models, isostatic models and flexural theory of Hthosphere and making used of global gravity model (UTCSR GRACE/GFZ EIGEN-GRACE), First, I calculate geoidal anomalies with different degrees and orders, isostatic residual geoidal anomalies of Hthosphere and horizontal stress distribution in Chinese mainland and vicinity and make an interpretation with multi-levels isostatic equilibrium. Secondly, combination with surface geology and others geophysical data, I analyze detailed structure of lithosphere within various segments of the central orogenic system (COS), respectively. Then, On the basis of making a comparative analysis with among East-Asian tomography, anomalies of geoid and satellite magnetic field for lithosphere and gravity and aeromagnetic, I propose a the lithospheric structural framework model for the Chinese mainland and adjacent area, specially the COS. Finally, I probe its present stress regime, deformation and dynamics. Some progresses are as following:1. In view of an analysis from lithospheric geoid, horizontal stress and existing seismic tomographic data and so on, they show that Chinese mainland and adjacent area is controlled by mantle dynamics of interaction, mutual influence and constraint by western Pacific ocean plate, Indian plate and circum-Siberian arc tectonics that formed after Paleo-Asian ocean closed, which consist of three tectonic areas, with on the base of the Tethyan tectonic realm. Overall tectonic framework of the Chinese mainland is outwards obduction along main tectonic borders within shallow crust and inwards subduction and convergence within deep lithospheric mantle from south-western, south-eastern and northern parts, respectively. The lithospheric mantle of the Chinese continent, as a whole, is in compressive tectonic regime.2. The lithosphere of eastern portion of the Chinese continent, being in extensional regime for level-shallow and motion eastward but westward dipping imbricated subduction that formed by high- and lower velocity slabs within lithosphere, suggests that it is in compressional regime in deep levels as a whole. Accommodations among different depth levels are accomplished by decoupling. The geoid of lithosphere, horizontal stress and P velocity tomography suggest that southern part of the Chinese mainland overall shows matching features of multi-lithospheric slabs during from Indo-Chinese to Yanshan ages.3. Deep lithospheric mantle in the Qinghai-Tibetan plateau and adjacent area, which consists of imbricated dipping-northward multi-lithospheric terrains, is in convergent-subduction regime for sinking of cold lithospheric material. Geoidal anomalies and P/S velocity tomographies show that subduction into beneath Euro-Asian continent by Indian lithosphere not only causes intensive crustal upwelling, thickening and shorting deformation along S-N, but also affects depth of～600km in the plateau and eastern part of the Chinese continent and southern margin of the Siberian block. A great geoidal low in the Euro-Asian continent is just an indication of the large-scale tectonic process in satellite global gravity field.4. The Yangtze and ORDOS cratons with thickened lithospheric roots become as a transitional zone or a firm rock in midstream between the eastern and western parts with different structural characteristics in Chinese continent and obstruct mutual material exchange and migration between the both. Not only is the present Yangtze craton constrained by regional compressional stress field but also its cold and dense lithospheric root is descended into the deep mantle by negative buoyancy, Which further strengthens inward obduction of orogenic belts surrounding it. For examples, Longmen shan mountain, Huaying shan and Bamian shan mountains override onto western margin and eastern part of Sichuan basin, respectively.5. Being on the setting of the above-mentioned three tectonic dynamic systems, the western Qinling and Songpan tectonic node takes the Mianlue-Animaqin suture, Ganzi-Litang suture and Longmen shan mountain as its boundary faults, and forms a material-sinking triangular prism area, which is surrounded, converged and superimposed by the North China block, Yangtze block and Qinghai-Tibetan plateau with different times, structural orientations and properties, also at the same time following delamination of the deep lithosphere. Studies for geology, geochemistry and geophysics indicate that Songpan-Ganzi block is attributed to a portion of the Gondwana old continent, being similar to the Yangtze block. A wholesale detachment interface had existed between its upper- and lower crust (depths from 18 to 21km). The western Qinling orogenic belt, along with the surface Mianlue-Animaqin suture and the detachment interface, had obducted southward onto the Songpan-Ganzi block, in turn, the Songpan-Ganzi block had thrusted southward along with Danba arc-shaped fault. As a whole, a crustal-scale double thrust tectonic system is formed. This structural framework had formed during Indo-Chinese and early Yanshan ages.6. Newest geoidal anomalies, satellite lithospheric magnetic field and seismic tomography indicate that lithosphere and mantle for the Euro-Asian continent, specially the Chinese mainland, is divided by EW,NW,NE and SN structures and formed type-chessboard structural framework.. NE and NW structures stride over surface tectonic units and form conjugate-like tectonics. It suggests that they are intra-plate tectonics after the Chinese mainland formation and mainly originate from the upper mantle. The EW structure, which originated from collision and match by North China and Yangtze plates during and past Indo-Chinese epoch, is further reactivated and superimposed by continuing intra-continent subduction since Mesozoic-Cenozoic. The structure, as an indicator of sub-dynamic system, is controlled and modified from the mantle by regional three dynamic systems that mentioned so that it is gradually decomposed and even vanishes. The SN structure is superimposed and compounded by Paleozoic relict structure of the lithosphere and new production from the mantle or the core-mantle interface.7. The lithospheric structure of the central orogenic system has distinct segmentation. At present the Tongbai-Dabie orogenic belt is controlled by SN and NW-SE compressive stresses and more thoroughly modified from deep mantle but the base of crust and within crust manifest EW structural traces that originated from plates subduction and match during Indo-Chinese times and/or later subduction of intra-continent. By which the high- and ultrahigh pressure metamorphic terrains (UHP) was extruded. The eastern Qinling orogenic belt, due to be affected by intensive convergence between the Yangtze and ORDOS high velocity lithospheres along SN trending, shows obviously EW structural character. Although the western Qinling orogenic belt is superposed and reformed by NE, NW and SN structures to cause complex lithospheric structures, vestige of the Mianlue paleo suture within lithosphere can be traced by geophysical data and linked to Animaqing structural belt.更多还原