论文部分内容阅读
上地幔顶部是地壳和岩石圈地幔能量传递和物质交换的关键区域,华北克拉通破坏与岩石圈减薄在空间分布和破坏机制上的差异势必会造成克拉通不同区域在岩石圈地幔顶部地震波速度的不同.使用华北及周边地区固定地震台站记录的Pn波到时数据,采用台站间Pn波到时差成像方法,反演得到了华北克拉通及周边地区上地幔顶部Pn波速度结构.结果显示:华北克拉通东部、中部和西部块体上地幔顶部表现出明显不同的速度异常结构,暗示着克拉通不同块体岩石圈在古生代以来可能经历了不同的构造演化和深部动力学过程,并在现今上地幔顶部留下作用的痕迹.华北克拉通东部块体渤海湾盆地地区上地幔顶部的明显高速异常可能代表了太古代岩石圈地幔的残留;郯庐断裂带和渤海海域上地幔顶部的低速异常可能归因于岩石圈的强烈减薄和软流圈热物质的上涌;而燕山地区下地壳和岩石圈地幔拆沉后形成的新生岩石圈地幔可能是这里上地幔顶部低速异常的原因.华北克拉通中部块体的太行山一带上地幔顶部显示为显著的低速异常,这一低速异常特征一直延伸到鄂尔多斯地块北缘的银川-河套裂陷和阴山造山带,可能与软流圈热物质沿克拉通西部块体周缘岩石圈构造薄弱带上涌有关,上涌形成的岩浆底侵或热侵蚀作用造成了岩石圈的减薄,并显著降低了上地幔顶部的速度.华北克拉通西部块体上地幔顶部为明显的高速异常,反映出尚未破坏的太古代克拉通古老岩石圈的性质.
The top of the upper mantle is the key area for energy transfer and material exchange in the crust and lithosphere mantle. The differences in the spatial distribution and damage mechanisms of the North China craton and the lithosphere thinning will inevitably result in different areas of the craton in the top of the lithospheric mantle The Pn wave arrival time data recorded by fixed seismic stations in North China and the surrounding areas were used to inversely derive the Pn wave velocities at the top of the upper mantle in North China Craton and the surrounding areas using Pn wave-to-time difference imaging method.Results The results show that the top of the upper mantle in the eastern, central and western blocks of North China craton show distinctly different velocity anomalies suggesting that different blocks of lithosphere in the craton may have undergone different tectonic evolution and deep dynamic processes since the Paleozoic. Which left traces on the top of the present upper mantle.The obvious high-velocity anomaly at the top of the upper mantle in the eastern block of the North China Craton may represent the remnants of the Archean lithospheric mantle; the Tan-Lu fault zone and the top of the upper mantle in the Bohai Sea Low-velocity anomalies may be attributed to the intense thinning of the lithosphere and the upwelling of asthenospheric thermo-chemicals; whereas the Yanshan The new lithospheric mantle formed after the subsidence of the lower crust and the lithospheric mantle may be the reason for the low-velocity anomaly at the top of the upper mantle in this region.The top of the upper mantle in the central part of the North China craton shows a marked low-velocity anomaly, The characteristics of the Yinchuan-Hetao rift and the Yinshan orogenic belt extending to the northern margin of the Ordos block may be related to the influx of asthenospheric thermotactic materials along the weak lithospheric tectonics along the periphery of the block in the western part of the craton. The magmatic underplating formed by the upwelling Or thermal erosion led to the thinning of the lithosphere and significantly reduced the velocity of the top of the upper mantle.The apparent velocity anomaly at the top of the upper mantle in the western part of the North China Craton indicates that the unspoiled Archean cratonic ancient lithosphere nature.