Airborne IP driven exploration for greenfield exploration: an application in the Horizon SEMACRET project

The critical raw materials (CRMs) exploration and supply is crucial to achieve the objectives defined by the European Critical Raw Materials Act to reach the green energy transition. In order to reduce the social and environmental impact of the exploration, innovative indirect techniques have to be adopted for the mineral targeting. Among the various geophysical methods, two of the most common techniques for exploration are the Induced Polarization (DCIP) and the Electromagnetic (EM) to map, respectively, chargeable and conductive bodies in depth. Although these techniques have been considered sensitive to different physical properties for a long time, it has been recognized that the effects of a polarizable ground can be measurable by inductive EM measurements (Smith et al., 1996), both airborne and ground. It has then been shown that is possible to model the inductive IP (Viezzoli et al., 2013) to retrieve the ground chargeability distribution and how novel modelling approaches (Dauti et al., 2024) can increase the inductive chargeability sensitivity in depth with good relationships with known mineralized bodies. In this context, with this contribute we propose a case study for which the retrieved inductive chargeability models have been actively used to define the next steps of the exploration workflow for a real green-field exploration research project (the HORIZON SEMACRET European project) with chargeable targets. First, two Airborne EM surveys have been flown with different base frequencies (12.5 Hz and 25 Hz) to increase the data sensitivity to IP effects and to improve the near surface resolution. Then, a modelling approach that points to reduce the equivalencies among the parameters of the “IP-expanded” model-space has been applied to the data to define where to follow-up on the ground. In this optic, the benefits of an effective AIP mapping are many, spanning from risk reduction to logistic simplification and increasing the mineral system understanding through the large-scale mapping of the ground resistivity and chargeability. With this work we also aim to investigate the inductive IP effects from a multi-frequency range prospective: we acquired on the ground different inductive data with different instruments and base frequencies over the AIP localized anomalies and compared the data among them and with overlapping DCIP galvanic lines. With this we aim to improve the understanding of IP effects at different scales of investigation and for different instrumental spectral contents among galvanic and inductive measurements.