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.