中国东部华北克拉通南缘至华夏地块深部电性结构研究

在华北克拉通南缘至华夏地块之间完成了两条大地电磁长剖面，通过二维非线性共轭梯度反演，获得了沿剖面100 km深的电性结构模型.结合研究区地质和地球物理资料，详细分析了研究区地壳及上地幔顶部电性结构特征与地质含义.研究发现：(1)江山—绍兴断裂带深部低阻异常成因可能是受南华纪裂解事件影响以及晚中生代岩石圈伸展作用、深部热物质上涌造成的；(2)华北克拉通南缘大部分地区中下地壳及上地幔顶部表现为低阻异常，可能存在大范围的软弱层或发生局部熔融.长江中下游成矿带壳内高导体可能是由含水流体引起；(3)华夏地块电阻性地壳与晚中生代构造-岩浆活动有着紧密的关系，其上地幔顶部的高阻异常可能与玄武岩浆活动有关.古太平洋板块的西向俯冲是华夏地块晚中生代构造活动的动力学背景.

Deep electrical structure from the southern margin of the North China Craton to the Cathaysia block in eastern China

Two magnetotelluric profiles have been deployed between the southern margin of the North China Craton and the Cathaysia Block. The electrical structure models along these two profiles with a depth range of 0~100 km were obtained by two-dimensional (Nonlinear Conjugate Gradient) NLCG inversion. Combining with the geological and geophysical data of the study area, we thoroughly analyzed the characteristics of the electrical resistivity structure and the geological implications for the crust and upper mantle evolution. The results revealed that: (1)The low resistivity anomaly in the Jiangshan-Shaoxing fault zone may be caused by the upwelling of deep hot mantle. (2) In the southern margin of the North China Craton, the middle and lower crust and the top of the upper mantle show low resistivity anomalies, and there may exist a large area of weak thin layer or local melts. In the Middle and Lower Reaches of the Yangtze River Metallogenic Belt, there is a high-conductivity layer that may be caused by aqueous fluids. (3)The resistive crust of the Cathaysia Block is closely related to the tectonomagmatic activity of the Late Mesozoic. And the high resistivity anomaly in the upper mantle of the Cathaysia Block may imply basaltic magmatism. The westward subduction of the paleo-Pacific plate is the dynamic background of the late Mesozoic tectonic activity of the Cathaysian block.