华南大陆东部地壳物质组成的地震学研究

中生代晚期华南大陆东部发生了大规模的火成岩活动,对地壳物质组成属性有显著影响,地壳中SiO2的平均含量是判别其属性的重要参数.基于华南大陆东部布设的宽频带地震台阵和固定台站数据,利用噪声成像获取高分辨率的面波频散,联合利用接收函数反演地壳的S波速度结构.由地壳的平均波速比和速度信息,通过与岩石物理实验数据对比,估测了华...

Crustal composition of the eastern South China Block based on the seismological study

In the late Mesozoic, extensive igneous activities occurred in the eastern South China Block (ESCB), which might change the crustal composition. The SiO2 contents of the crust is an essential feature of its properties. Based on the data from the broadband seismic array and permanent stations deployed in the ESCB, we use ambient noise tomography to obtain high-resolution surface wave dispersions, and then we apply joint inversion of surface wave dispersions and receiver functions to construct the crustal S-wave velocity structure. Finally, based on the crustal average S-wave velocity and VP/VS ratio, we further estimate the spatial distribution of crustal SiO2 contents referring to the petrophysical experiment data. The results show high lower crustal S-wave velocity (greater than 3.9 km·s-1), relatively high VP/VS ratio (greater than 1.77), and intermediate composition with SiO2 contents of 60~65 wt% in the southeast coastal region at where extensive alkaline igneous rocks emplaced. In contrast, the Wuyi orogenic belt and Jiangnan orogenic belt have relatively low S-wave velocity (lower than 3.8 km·s-1), relatively high VP/VS ratio (lower than 1.75), and contains relatively felsic composition with SiO2 contents of 65~70 wt%. The diverse crustal components across the Zhenghe-Dapu fault, as intermediate-mafic to the east while felsic to the west, indicate that the subduction of the paleo-Pacific plate has caused thermal erosion process beneath the ESCB, and the crust-mantle metasomatism is mainly limited to the east of the Zhenghe-Dapu fault.