南海东北部新生代岩浆活动的时空分布及岩浆运移过程研究

It has been suggested that magmatism plays an important role in terms of material circulation and dynamical mechanisms. The northeastern South China Sea (SCS) margin evolved from being convergent to being divergent during the late Mesozoic to Cenozoic, which provides rich evidence for overall understanding the evolution of the northern SCS margin. The occurrence of significant volcanism was identified and remains largely unknown, bringing the uncertainty for the nature of the crust in the northern SCS. It is suggested that magmatism can yield important insights into continental rifting and seafloor spreading of the SCS. Based on previous studies, we present the first comprehensive analysis of Cenozoic magmatism in the northeastern SCS: (1) the morphology and distribution of Cenozoic volcanism in the northeastern SCS; (2) the timing of such volcanism, which allowed the volcanism to be placed into a geodynamic framework of the northern SCS; (3) the relationship between the magmatism and the underlying crustal structures, as well as the geodynamic drivers for magmatism and their implications for tectonic evolution of the SCS.

岩浆活动是研究地球深浅物质循环及全球动力学的重要纽带。南海东北部作为一个拉张型大陆边缘，其构造特征极为独特，既展现出了典型张裂陆缘的构造模式，又发育有裂后期强烈的岩浆活动，引发了南海北部陆缘构造属性的极大争议。因此，研究南海东北部新生代岩浆活动的时空特征和运移系统是深入理解南海张裂扩张演化的重要基础。本项目拟在前人工作的基础上，对南海东北部陆缘发育的岩浆活动进行精细研究，重点解决（1）南海东北部新生代岩浆活动的侵位方式、空间展布以及浅部岩浆运移通道；（2）南海东北部新生代岩浆活动的发育时间和期次；（3）浅部岩浆活动与深部构造的耦合关系。以此揭示岩浆活动从深部到浅部的动力学过程及在南海陆缘构造演化过程中扮演的角色。

为了揭示南海东北部新生代岩浆活动的时空发育特征，我们以项目申请书提出的技术路线为指引，从地球物理数据处理与解释以及地质构造解释等方面，由浅及深综合系统研究南海东北部浅部岩浆活动的时空分布和岩浆运移过程，获得了岩浆活动的侵位方式、空间展布以及浅部岩浆运移通道，定量估算了研究区岩浆喷出的体积，获得了研究区内岩浆活动的发育时间和期次，揭示了浅部岩浆发育与深部构造的耦合关系，提出了南海东北部陆缘成层式的岩浆运移模式，刻画了岩浆活动在南海北部陆缘构造演化过程中扮演的角色，阐述了南海东北部陆缘是一个受控于中生代先存构造且被新生代岩浆活动强烈改造的被动陆缘。本项目有关南海北部岩浆活动的研究成果被科学网、中科院和南海所等官网报道。综上所述，我们很好地完成了项目计划书所提出的各项任务和目标，基本实现了各项成果指标。