Three-dimensional inversion of the frequency domain airborne CSEM data over the kimberlite complex for the conductive and susceptible heterogeneities

Abstract

The electromagnetic survey data has been used to interpret the susceptibility structure as well as conductivity structure. The frequency domain EM responses related to the conductive anomaly and the susceptible anomaly have different characteristics such as frequency dependance and phase information which make different contribution of each anomalous response the in-phase and out-of-phase components. Based on these characteristics, we set iterative inversion framework that separately uses out-of-phase component for conductivity inversion and low frequency inphase component for susceptibility inversion. We then applied this inverion framework to the frequency domain EM data set acquired over kimberlite complex. We set two zones of interest that are kimberlite zone and dyke zone and respectively inverted the data sets of two zones. With kimberlite zone data set, conductivity inversion succesfully imaged two isolated conductive anomalies, which are already known as kimberlite pipes, embedded in resistive background. In this kimberlite zone, susceptibility inversion was not possible due to relatively weak susceptibility of anomalies compared to background noise. With dyke zone data set, the same inversion framework was applied and succesfully reconstructed conductivity structure and susceptibility structure of the dyke.