南海西北部盆地构造沉积特征对青藏高原隆升的响应

The Tibetan Plateau - Yinggehai and Qiongdongnan Basin at the northwestern South China Sea is the world’s most mountain-basin coupling system. The research subjects of this project are to figure out the tectonic sedimentary deformation in the northwestern part of the South China Sea caused by the uplifting of the Tibetan Plateau, and to reveal the basin formation mechanics and evolution model of the Ying-Qiong Basin. With the Red River Fault Zone serving as a bridge between the Tibetan Plateau in the north and the Ying-Qiong Basin of the South China Sea, we are to look at the Tibetan Plateau, the old Red River road and the Ying-Qiong Basin as a united system. We will focus on tracking the spatial and temporal differences of the Red River Fault Zone's deformation and its control over the framework of the Ying-Qiong Basin in the northwestern part of the South China Sea, sorting out major tectonic episodes of the basin and active stages and duration of significant sedimentary events controlled by the tectonic evolution, establishing the migration pattern of the basin sedimentary-subsidence center, extracting the sedimentary record from the uplifting of the Tibetan Plateau, figuring out the response relationship between the Ying-Qiong Basin's source-sink effects pattern and the Red River system, building up the coupled model for the rheological structure of the basin lithosphere and the brittle deformation in shallow layers-ductile deformation in deep layers, numerically modeling the response relationship between the evolution process of the Ying-Qiong Basin and the uplifting extrusion of the Tibetan Plateau. Ultimately, we would like to reveal the Southeast escape mechanism of the Tibetan Plateau, and to find out the main controlling factors responsible for the Ying-Qiong Basin and its evolution mechanism, and to provide theoretical support for oil and gas exploration in deep water.

青藏高原与南海西北部莺歌海-琼东南盆地是全球最显著的盆-山耦合体系。本项目的研究目标是搞清青藏高原隆升挤出在南海西北部盆地引起的构造沉积活动，揭示莺-琼盆地成盆动力机制和演化模式。拟以红河断裂带为纽带，北连青藏高原、南接南海莺-琼盆地，将青藏高原-红河古道-莺琼盆地作为统一体系，以追踪红河断裂带形变的时空差异特征及其对南海西北部莺-琼盆地形态格局的控制为主线，厘定莺-琼盆地重大构造幕次和构造控制的重大沉积事件的活动期次及时限，建立莺-琼盆地沉降沉积中心迁移模式，提取青藏高原隆升的在盆地的沉积记录，揭示莺-琼盆地源-汇效应模式及其与红河体系的响应关系，建立莺-琼盆地岩石圈流变结构及其浅层脆性形变与深层韧性形变的耦合模式，数值模拟莺-琼盆地演化过程与青藏高原隆升挤出之间的响应关系。最终揭示青藏高原东南逃逸机制、确立莺-琼盆地形成的主控因素和成因演化机理，为深水区油气勘探提供理论支撑。

本项目以盆-山耦合的视角讨论了青藏高原构造变形向其东北缘传递的时空过程，认为柴达木盆地周缘造山带隆升过程主要存在侏罗纪-白垩纪、~40Ma、~20Ma以及<~5Ma四个关键构造演化期次，并尝试建立了柴达木盆地与祁连山、阿尔金山以及东昆仑山的耦合演化模型，测年、地震资料分析显示青藏高原东北缘在新生代之前应为有着一定高程、厚地壳的“古高原”。据年代学、岩石学分析，可知伴随着印支地块的旋转挤出，红河断裂带自渐新世时期（~32Ma）表现出差异性的左旋活动特征，而晚中新世（11-4.6Ma）以来，伴随着青藏高原强烈挤压收缩，在高原东南缘，挤出逃逸物质由早期的印支块体逐渐变为东侧的川滇块体，而逃逸边界则由红河断裂带向东迁移至鲜水河-小江断裂带，这也由此导致红河断裂带晚中新世时期发生旋向切换。在挤出逃逸过程中，高原东南缘深部地幔、地壳运动受控于不同的动力过程，地幔运动主要由西侧印度板块沿缅甸-巽他海沟俯冲活动主导，而高原则更多以走滑断裂系调节浅部地壳运动形式向周缘传递其缩短变形。据盆地地震、测井等资料，分析南海西北部莺-琼盆地构造沉积结构，理清新生代时期莺-琼盆地沉积沉降迁移规律及与青藏高原隆升剥蚀的耦合关系。特别是，上新世以来，受青藏高原多幕次、整体快速隆升与剥蚀事件的根本控制，由红河水系搬运的大量来自藏东-滇西的碎屑物质被输送进入南海西北部莺歌海与琼东南盆地的结合部，并借助红河断裂带右行走滑的启动触发了海底浊流活动，从而开启了琼东南盆地中央峡谷体系的形成和发育演化的历史进程。综合青藏高原时空形变及莺-琼盆地构造沉积演化分析，本项目认为南海西北部陆缘岩石圈伸展裂解过程与青藏高原隆升、物质挤出逃逸更多体现在地壳尺度上的联系，至于南海西北部盆地区域深部地幔活动纵然会经受断裂切割、均衡调节作用，但主要还是受控于西侧印度板块的东向俯冲作用，而青藏高原深部地幔SE向逃逸可能仅展布于26ºN以北地带，其影响范围甚至都没有贯穿川滇、印支、华南块体。