Abstract:Experiments were carried out on more than fourty various mineral specimen with the dual-frequency IP instruments in a closed condition and a 3-D water tank to study the nonlinear effect of the dual-frequency IP spectrum.The comparison of experimental and theoretical analysis results showed that the sawtooth feature will be appeared on the dual-frequency IP spectral curves when the induced current density is increased to a certain value,and the feature is different for different minerals.Based on this feature,it is possible to develop a new geopgysical method to evaluate the IP anomalies using the dual-frequency IP method.

Key words: nonlinear effect; spectral curves; sawtooth feature; dualfrequency IP method