Three-component Response Analysis of Multi-Effect in Grounded-wire Source Time-domain Electromagnetic Surveys

The multi-effect fields in the grounded-wire source time-domain electromagnetic (TDEM) will be generated by complex physical characteristics and parameter information of polymetallic ore. The studies show that the induced polarization (IP) and magnetic viscosity (MV) effects are significant signs of polymetallic ore and have been proved to exist simultaneously. Therefore, the accurate observation and resolution of IP and MV characteristics are of great significance to improve the interpretation accuracy of polymetallic ores. In this study, a three-dimensional (3-D) modeling method of IP and MV effects in grounded-wire source TDEM method is proposed, and the three-component response characteristics of multi-effect fields in an electrical source are studied. Fractional Cole-Cole conductivity and magnetic susceptibility models are introduced to characterize the IP and MV effects, and the double-curl IP-MV electric field diffusion equation is derived. And the 3-D modeling of multi-effect three-component response of grounded-wire source is realized based on the recursive convolution technique and vector finite element method (FEM). The effectiveness of the 3-D modeling method is verified by comparing with the analytical solutions of the grounded-wire source, and 3-D models are established to analyze the three-component response characteristics of IP and MV effects. The results show that more obvious multi-effect characteristics can be obtained by observing the magnetic field component parallel to the grounded-wire source, and multi-effect responses with larger amplitude can be obtained by observing the vertical component. The three-component observation of multi-effect field is helpful to improve the detection accuracy of polymetallic ore.

本数据集涉及基于接地导线源时域电磁法（TDEM）产生的多效场，其生成源于多金属矿石的复杂物理特性及参数信息。研究表明，激化极化（IP）和磁性粘滞（MV）效应是多金属矿石的重要标志，并已被证实可同时存在。因此，对IP和MV特性的精确观测和解析对于提高多金属矿石的解释精度具有重要意义。在本研究中，提出了接地导线源TDEM方法中IP和MV效应的三维（3-D）建模方法，并研究了电气源多效场的三分量响应特性。引入了分数Cole-Cole电导率和磁化率模型以表征IP和MV效应，并推导出双旋度IP-MV电场扩散方程。基于递归卷积技术和矢量有限元法（FEM），实现了接地导线源多效三维三分量响应的三维建模。通过将该方法与接地导线源的解析解进行比较，验证了三维建模方法的有效性，并建立了三维模型以分析IP和MV效应的三分量响应特性。结果表明，通过观测与接地导线源平行的磁场分量，可获得更明显的多效特性；通过观测垂直分量，可获得幅度较大的多效响应。对多效场的三分量观测有助于提高多金属矿石的检测精度。