华南东部岩石圈几何结构与伸展机制研究——密集宽频带地震台阵数据接收函数分析

The lithosphere-asthenosphere boundary (LAB) is an important geodynamic boundary within the earth. Its geometric and spatial characteristics are the key for understanding the deformation behavior of the lithosphere. Though some local thin lithosphere has been detected beneath the eastern part of the South China by recent deep explorations, the overall feature and some key details of the lithosphere are still unclear due to the shortage of high-resolution spatial data. Thus, the mechanism and deep process of the lithospheric extension in the South China remain controversial. In this project, we aim to get a high-resolution LAB image based on the dense broadband seismic data, including temporary broadband seismic array in southeastern China, several profiles from SinoProbe project and data from permanent stations. Both the P- and S-wave receiver function methods are employed to pick a reliable LAB phase. The results of the proposal could reveal the basic geometrical features of the lithosphere in the southeastern China. Meanwhile, combining with previous geological and geophysical studies (including deep reflection profiles and wide-angle seismic profiles), we intent to discuss the dynamic mechanism of the lithospheric extension in the southeastern China and its surface effects on tectonics and resources. The prospective research result will enhance our understanding on the lithoshperic evolution of the southeastern margin of the East Asian continent.

岩石圈-软流圈边界（LAB）是地球内部的重要地球动力学界带，其几何特征与空间形态是理解岩石圈变形行为的关键。最近几年的深部探测与研究已在华南东部多处发现岩石圈减薄现象，但是由于缺乏较高分辨率的面状探测资料，其空间形态的整体面貌和许多关键细节仍不清楚，制约了对华南岩石圈伸展机制和深部过程的理解。本项目拟利用华南宽频地震流动观测台阵数据，结合数条SinoProbe宽频地震流动观测剖面和国家地震台网资料，通过P波与S波接收函数方法联合，提取更可靠的岩石圈-软流圈边界（LAB）震相，获得华南东部岩石圈厚度横向展布的高分辨率图像，揭示华南东部现今岩石圈基本几何特征，并结合前人的地质和地球物理（深反射地震剖面和宽角反射地震剖面）研究成果，探讨华南东部岩石圈伸展的动力学机制及其浅表构造-地貌、资源环境效应，深化对东亚大陆东南缘岩石圈演化的理解。

岩石圈厚度可为中国东部晚中生代以来的岩石圈伸展研究提供重要约束，研究表明华北克拉通东部岩石圈经历了大规模非均匀减薄，虽在华南东部发现存在薄岩石圈现象，但是由于缺乏较高分辨率的深部资料，其空间形态仍不清楚，制约了对华南岩石圈伸展机制和深部过程的理解。本项目利用华南东部固定台站和流动台站的远震波形数据，通过接收函数方法和接收函数与背景噪声联合反演方法，获得了华南东部高分辨的Moho和LAB界面起伏图像、地壳平均泊松比结构、关键构造带的接收函数偏移图像和壳幔S波速度结构、地幔过渡带结构等。在此基础上，分析了华南不同块体内部地壳和岩石圈结构与物性的差异，分析了地壳和岩石圈形态与地表构造的关系，结合研究区地质、地球化学研究结果，探讨了华南东部岩石圈伸展的动力学机制和成矿的深部背景。该项研究提升了对东亚大陆东南缘岩石圈演化的理解，可为中国东部矿产资源勘查与评估提供深部约束。