东海西湖凹陷中新世末反转背斜构造成因机制:来自基底结构差异的新认识

东海西湖凹陷广泛发育中新世末形成的大型反转背斜，关于背斜成因前人多认为与外力作用有关，忽视了凹陷内部结构的影响.以重磁震资料综合解释分析为基础，系统梳理中新世末反转背斜分布及其与凹陷基底结构的关系，并结合构造物理模拟实验方法探讨基底结构差异对反转背斜发育的影响.结果表明，中新世末反转背斜与高磁性火成岩基底分布呈现出明显的相关性，且均具有南北分段差异.凹陷北段火成岩基底分布在中央洼陷-反转带内，反转背斜主要在火成岩基底东缘区发育；凹陷南段火成岩基底分布在东、西两侧边缘，反转背斜主要在边缘火成岩基底内侧发育.构造物理模拟实验结果显示，在挤压背景下，压应力通过相对刚性硅胶边缘释放，控制挤压背斜褶皱的形成；表明不同岩性基底所产生的抗压强度差异能显著影响反转背斜分布.最终提出在挤压背景下，高磁性、高抗压强度的火成岩基底所引起的局部构造应力场改变是决定中新世末反转背斜强弱分布的关键因素. 

Genetic Mechanism of Inversion Anticline Structure at the End of Miocene in Xihu Sag,East China Sea: A New Understanding of Basement Structure Difference

Large inversion anticlines formed at the end of the Miocene are widely developed in Xihu Sag in the East China Sea,which have generally attributed to external forces,ignoring the influence of the internal structure of the sag. Based on the comprehensive interpretation and analysis of gravity and magnetic seismic data,this paper systematically sorts out the relationship between the distribution of inversion anticlines at the end of Miocene and the basement structure,and discusses the influence of basement structure difference on the development of inversion anticlines in Xihu Sag by combining with structural physical simulation experimental methods. The research results show that there is a clear correlation between the inversion anticline at the end of Miocene and the distribution of high magnetic igneous rock basement,and it shows South-North segments. The igneous rock basement in the northern part of the sag is distributed in the central sag-inversion zone,and the inversion anticline is mainly developed on the eastern edge of the igneous rock basement. The igneous rock basement in the southern part of the sag is distributed on the eastern and western edges,and the inversion anticline is mainly developed on the inner side of the distribution area of the igneous rock basement on the edge. Structural physical simulation results show that under the compression background,the compressive stress is released through the edge of rigid silica gel to control the formation of compression anticline folds. The results reflect the difference in compressive strength caused by different lithological basement and can significantly affect the strength distribution of inversion anticlines. Finally,this paper proposes that the change of regional tectonic stress caused by igneous rock basement with high magnetic and high compressive strength is the key to control the strength distribution of the inversion anticline at the end of Miocene.