【作者】 谢建华；

【导师】 林舸； 夏斌； 张晏华；

【作者基本信息】 中国科学院研究生院（广州地球化学研究所） ， 构造地质学， 2006， 博士

【摘要】 边缘海是大陆和大洋岩石圈过渡带上形成的特殊地质构造单元,有着独特的形成演化机制,是研究地球动力学的理想场所。研究边缘海的目的在于探索边缘海形成与演化及其蕴藏资源的规律性,进而推动大陆边缘裂解与增生机制、洋陆相互作用、物质交换与能量传递等重要科学问题研究的深化与发展,丰富地球动力学理论,也将对其他相关前沿领域产生巨大的推动作用。 南海海盆是西太平洋最大的边缘海盆地,面积约为300×10~4km~2,处于欧亚板块、印度-澳大利亚板块和太平洋板块三者相互作用的交汇处,在地质历史上,经历了特提斯构造域和古太平洋构造域演化的制约,经历了复杂的地质演化过程,形成了裂谷、推覆、海盆等多种地质构造现象,以及陆壳、过渡陆壳和洋壳等多种地质构造单元,并发育有多种形式的地质体和相关矿产资源,被国内外众多学者誉为“地球上最好的天然实验室”。 前人对南海的形成演化做了大量的工作,提出了弧后扩张模式、碰撞-挤出-逃逸模式和地幔柱(上涌)模式等有代表性的南海成因模式,但他们的研究都只关注了其中某一个因素对南海的影响,存在一定的片面性。本研究将南海及其邻区放入特提斯构造域和太平洋构造域的共同作用下,通过分析南海及其邻区地质构造演化及与周边板块之间相互运动关系,得出南海及其邻区的区域应力场演化阶段,在此基础上,建立合理的地质模型,将南海置入印度-澳大利亚板块、欧亚板块和太平洋板块三者共同作用的环境中,充分考虑大区域构造应力场对南海形成的影响。运用数值模拟方法进行分析,设置合理的模型边界条件和实验参数,通过数值模拟平面模型来探讨印度板块与欧亚板块之间的碰撞及随后的楔入作用能否产生足够导致南海打开的构造挤出和在南海地区产生广泛的水平拉张,以及印度-欧亚板块碰撞期间,红河断裂带的走滑运动性质等问题;通过剖面模型来探讨印度-欧亚板块碰撞情况下,地幔上涌作用对南海地区地壳和岩石圈结构影响的效应。 通过本次研究,作者认为南海及其邻区的区域应力场演化受到太平洋构造域和特提斯构造域的双重作用制约,经历五个不同的演化阶段,并提出了南海地区更多还原

【Abstract】 The marginal sea is a special geological structure unit, which developed in the transition zone between continental and oceanic lithosphere, with unique formation and evolution mechanism, and is a very perfect site to study the geodynamics. The aim to study marginal sea is to explore the rules of the formation and evolution and the resources, further to develop some important scientific issues, such as the mechanism of the continental marginal rift and accretion, the interaction between the continent and ocean, and substance exchange and energy transport, and to enrich the theories of geodynamics to push the related preceding fields.The South China Sea(SCS) is the biggest marginal basin of the West Pacific, with an area of about 300 × 104km2, located in the junction of Indo-Australia plate, Eurasian plate and Pacific plate in the Cenozoic. Underwent the restriction of the Tethyan and the Proto-Pacific structure fields and complicated evolution process in its geological history, formed multiplicate geological structures, such as rift, nappe structure, oceanic basin, et al., and multiplicate geological units, such as continental crust, transitional continental crust and oceanic crust. There were developed multiplicate geological unit and related mineral resources. It is considered to be "the best natural laboratory in the Earth" by numerous domestic and overseas geologists and geophysicists.The formers have done numerous researches on the formation and evolution of the SCS, and put forward some representative scenario models, such as, back-arc spreading model, collision-extrusion-escape model, and upwelling mantle (plume) model. But there are some limitations because their models only focus on one factor that influence on the SCS. In this study, the SCS is put into the conditions which interacted with the tethyan tectonic field and the Pacific tectonic field, we obtain the evolution stage of regional stress field of the SCS. Then the authors build some reasonable geological models on the base of analysing synthetically the previous geological studies on the SCS. The SCS is put into the conditions which interacted with the Indo-Australia plate, Eurasian plate and Pacific plate. Some reasonable boundary conditions and mechanical properties are set in these models, then these models are run using the Finite Difference Method(FDM). In this work, the plan-view models were constructed to simulate the India-Eurasia collision, its resultant intra-plate deformation and lateral motion along the Red River Fault, to address the question whether the collision can generate sufficient eastward tectonic extrusion, lateral shearing or approximately N-S directed extension, the slip movement of the Red River Fault during the collision. The authors then use 2D cross section models tosimulate the influence of deep asthenosphere upwelling on lithospheric deformation. The authors conclude the region stress field of the SCS and its peripheral regionsexperiences five different evolutive stages under the controls of the Pacific tectonic field and the tethyan tectonic field, then a temporal-spatial evolution mode of the SCS in Cenozoic is put forward.The results of plan-view models show that the India-Eurasia collision can result in extensive east-southeastward tectonic extrusion, approximately N-S directed extension in the SCS region. During the early stage of the India-Eurasian plate collision, the modelled Red River Fault first experienced huge left-lateral shearing and then changed to right-lateral shearing in the late collision stage. The style of shearing motion along the Red River Fault is a function of the distance between the fault and the India-Eurasia collision frontier, which decreases with time and controls relative extrusion movement between the South China Block and Indochina Block.The results of cross-section models further demonstrate that such horizontal extension can only generate limited thinning of the continental lithosphere in the SCS region. In contrast, asthenosphere upwelling is much more efficient in generating lithospheric upper mantle thinning but still inefficient for crust thinning. It is the combination of mechanical extension and asthenosphere upwelling that proves to be the most efficient way to thin the entire lithosphere, and that represents the most likely driving mechanism for the opening and spreading of the SCS.The authors also conclude the opening of the SCS was controlled by the India-Eurasian collision, subduction of the Pacific plate to the Eurasian plate and the mantle flow upwelling.更多还原