被动陆缘洋陆转换带和岩石圈伸展破裂过程分析及其对南海陆缘深水盆地研究的启示

Ocean and continent transition in passive continental margins and analysis of lithospheric extension and breakup process:Implication for research of the deepwater basins in the continental margins of South China Sea

作为伸展陆壳和正常洋壳之间重要的过渡和衔接,洋陆转换带(ocean-continent transition,简写为OCT)蕴含有丰富的地壳岩石圈伸展破裂过程的信息。文中通过系统的资料调研,在总结OCT研究历史、现状和发展趋势的基础上,阐明了OCT的现代概念、类型及其识别标志;详细介绍了以OCT为基础而建立的被动陆缘地壳岩石圈结构构造单元划分方案、表层沉积盆地构造地层格架及重要的构造变革界面特征;分析了大型拆离断层在地壳岩石圈薄化、地幔剥露过程中的控制作用;揭示了陆缘变形集中、迁移和叠合的规律,建立了被动陆缘岩石圈伸展、薄化、剥露和裂解模式。最后,论文对比了国际非岩浆型被动大陆边缘与我国南海OCT的研究,介绍了南海OCT和陆缘深水-超深水盆地研究的新发现,提出深入研究南海OCT将为南海陆缘构造演化、洋盆扩张过程和深水-超深水盆地的成因机制研究提供新的启示。

As an important transition domain between the last identifiable extended continent crust and the first true oceanic crust,the ocean-continent transition（OCT）zone preserved a wealth of information on the processes of lithospheric extension and breakup.In this paper,considering OCT as a key to understanding the mechanism of the lithospheric extension and breakup,we try to show the geological nature of the OCT,and its geological and geophysical identification based on an integrated analysis of a rich subsurface data,including borehole data and newly released geological and geophysical data collected by marine geological survey and hydrocarbon exploration and development.We are also to elucidate the continental lithosphere configuration and its overlying sedimentary basin＇s tectono-stratigraphic framework in the different tectonic units on the continental margin.It is noteworthy that we will compare the structures,major tectonic boundaries and tectonic sequences in the sediment fillings of the basins,which will explore the information during the processes of the continental margin extension,exhumation,breakup and oceanic spreading.In addition,we will study the large-scale detachment faults and their controls on the lithospheric thinning and continental mantle exhumation.We will investigate where the lithosphere of continent margin concentrated,and how the deformtion migrated and superimposed,and further construct the model of lithospheric extension and breakup.OCT is the area where the lithospheric deformation and final breakup occurred.Therefore,Our research will better improve our understanding of the birth of the oceanic crust and symmetric conjugate structures in the South China Sea,and has a great significance for economic exploration（hydrocarbon）in the deepwater/ultradeepwater area of South China Sea.