THE 3D TRANSIENT ELECTROMAGNETIC FORWARD MODELING OF VOLCANOGENIC MASSIVE SULFIDE ORE DEPOSITS

The transient electromagnetic forward modeling of volcanogenic massive sulfide (VMS) ore deposits is to calculate the eddy currents electromagnetic response of a three dimensional body in the full space of deep-sea environment. We simulated the three dimensional transient electromagnetic response of the VMS deposits using full-domain vector finite element method. The ore body was discretized with brick rectangular elements. The finite element equation was deduced in frequency domain by employing Galerkin procedure, and the conversion to time domain was by inverse Fourier transform. We confirmed the validity of the full-domain vector finite element algorithm by comparing simulated results with analytical solutions of double half-space model. The results have a good agreement with each other, which indicates that the vector finite element method is capable of solving whole space problem. In order to demonstrate the ability of the numerical method in calculating the response of VMS deposits containing complex boundary conditions, we compared vector finite element solution of a three dimensional electrical model with physical experiment results according to electromagnetic physical scale modeling rules. The comparison suggests that for the complex electromagnetic boundary of seawater, ore body and country rocks, the transient electromagnetic response of VMS deposits calculated by full-domain vector finite element method has same features with the physical scale modeling result. The vector finite element method is simple and its results are precise with obvious and clear anomaly response.