南海北部洋陆过渡带深水盆地结构和演化及其对南海扩张的启示

Studying the ocean-continent transition zone is key to understand the mechanism of lithospheric break up and sea-floor spreading. In this proprosal, based on newly released geological and geophysical data collected by marine geological survey and hydrocarbon exploration and development, we will unravel the structure and tectonic, stratigraphic sequences and depositional systems of the Cenozoic deep-water sedimentary basins on the ocean-continent transition zone of the northern South China Sea. We aim to build a criterion of the geophysical recognition, structural characteristics and distribution patterns of the ocean-continent transition zone in the north South China Sea. In addition, we will compare the structure and tectonics, filling patterns and evolutionary process between intra-continental basins, shelf basins and ocean-continent transition basins of northern South China Sea. Tectono-stratigraphic characteristics of deep-water basins during the processes of continental margin extension, lithospheric thinning and breakup will be revealed. Combining the geological data with geophysical imaging of the regional lithosphere, we attempt to build several typical lithosphere regional sections which crossing the northern continental margin of the South China Sea. Morover, we will apply some novel geodynamics modellings to better explore the process of lithosphere extension-thinning-breakup and coupling between subsidence of deepwater basins and uplift of South China Block. Combined the deep lithosphere data and reorganization events of the periphery plates, a better model of deep-water basins on the ocean-continent transition zone will be built up in our study. Our research will better improve our understanding of the development and evolution of ocean-continent transition zone of South China Sea, and has a great significance for geodynamics of the continental margins and its petroleum exploration in the deep-water area of South China Sea.

从岩石圈裂解和海底扩张的关键点－洋陆过渡带的研究入手，以海洋调查和油气勘探开发中积累的地质和地球物理资料为基础，对南海北部洋陆过渡带及其所控制的深水盆地结构构造、层序和沉积体系等进行详细解释和分析。确定洋陆过渡带的识别标志、结构特征和分布规律；对比和分析陆内盆地、陆架盆地、洋陆过渡带盆地结构、构造、充填样式和演化过程，揭示深水盆地构造地层中记录的陆缘伸展、薄化、破裂和海底扩张过程的信息；结合区域岩石圈综合地质和地球物理资料，建立穿越南海北部大陆边缘的岩石圈区域剖面，并使用先进的模拟软件，对这些剖面开展岩石圈伸展-薄化-破裂过程及其所控制的盆地沉降-隆升的正演和反演模拟研究，建立洋陆过渡带深水盆地发育模式；结合深部资料和周缘板块构造运动重组事件对盆地发育影响的分析，建立南海北部洋陆过渡带盆地发育的动力学模型，确定其演化过程和成因机制，并服务于研究区的深水油气勘探。

本项目于2013年1月批准执行，2016年12月完成。项目的主要目标是揭示深水盆地构造地层中记录的陆缘伸展、薄化、破裂和海底扩张过程的信息，建立南海北部陆缘深水盆地发育模式，并服务于正在快速走向深水的我国南海油气勘探。经过4年的研究，按计划完成了研究任务，并取得了显著成果。明确了洋陆转换带的概念和地质属性，建立了以伸展、薄化、剥露和裂解为特征的非瞬时岩石圈拉伸破裂模式，为阐明南海洋盆扩张的孕育过程提供了重要的信息和依据。划分了南海北部陆缘构造单元，发现并证实了南海北部深水/超深水区拆离断层及其所控制的拆离盆地，深刻改变了传统深水盆地结构样式和成盆机理的认识，为科学地评价深水或超深水盆地勘探潜力提供了重要的理论基础。本项目已发表研究论文9篇，包括3篇国际SCI论文，4篇国内SCI论文和2篇国内EI论文，研究成果已经得到了学术界和油气产业界的关注，并进行了较为广泛的国内外交流。