中国大陆密度和地震波速扰动异常的年龄属性研究

大陆动力学研究需要物质随空间和时间的变化的信息。三维密度和地震波速度扰动图像反映岩石圈物质的空间分布,要和大地构造学中的时间尺度信息综合起来,才能恢复动力学作用的过程。本文通过对比不同构造期的构造图和地壳不同深度的地球物理性质图像,研究中国大陆密度以及地震波速度扰动和构造事件的相关度。研究表明,岩石圈地幔的密度和波速扰动和现今板块构造的相关度是高的,说明岩石圈地幔的密度大黏度高,不仅地震波速快得多,物质蠕动的速度也比下地壳慢得多,板块运动产生的变形保存时间比较久。中国大陆中地壳的密度扰动和白垩纪以来的构造事件的相关度是高的,说明中地壳的密度扰动主要反映了白垩纪以来的构造事件。中国大陆上地壳结晶基底的密度扰动和侏罗纪以来的构造事件的相关度是高的,说明上地壳的密度扰动可以反映燕山期的构造事件。对于中国大陆而言,下地壳的波速变化和板块构造没有明显的相关性;不过下地壳深层的密度扰动也反映新构造期的构造事件。其原因可能是因为下地壳的物质黏度比较低,物质蠕动的速度比岩石圈地幔快得多,板块运动产生的变形不容易保存。总之,应用不同深度的密度扰动图像分别推测不同地质时期的地壳构造运动发生的地点和范围是可...

Correlation of density and seismic velocity anomalies with different tectonic events in the Chinese continent

The study of continental dynamics requires matter movement information that includes both the spatial and temporal parameters.The three-dimensional density and seismic velocity disturbance images reflect the spatial movements of lithosphere material,but lack the time-scale information of lithosphere matter movements.It is possible to integrate the temporal and spatial data to break the bottleneck in dynamic research by combining recent progress inboth tectonics and in comprehensive geophysical surveys.In this paper,the correlation between density and velocity disturbance images and tectonic event calibrationis studied by comparing the tectonic event graphs of different tectonic periods with the geophysical anomalies at different depths of the Chinese crust.The results show that the density and velocity disturbances of the lithospheric mantle in China are highly correlated with plate tectonic events after Jurassic period,and because the matter viscosity are high and creeping velocity are low,deformation anomalies could be preserved long afterthe tectonic events.The density disturbances of the middle crust in China are also correlated with tectonic events since the Cretaceous period,indicating that the density anomalies of the middle crust mainly reflect the tectonic events since the Cretaceous.The density disturbances at 12km depth correlates to tectonic events since Jurassic are later,indicating that the density anomalies of the continental crystallized basement can reflect the tectonic events of Yanshanian Period.However, the density disturbancesat the top of the upper crustwere affected by many factors,and the density disturbance images can only reflect the tectonic events of the Quaternary.Therefore,the density and velocity disturbances in the lower crust in China are not correlated with plate tectonic events after Jurassic period, and because the matter viscosity was lower and creeping velocity was JP higher,the deformation results could not be preserved long after the causaltectonic events.In summary,it is feasible to use the density and velocity disturbance images of different depths to estimate the location and extent of crustal structuresrelated with different geologic periods,and to study of continental dynamics events in Chinese continent since 180Ma.