IPEx-3D: Optimization of 3D RES/IP/MT surveys to efficiently follow-up 'Recon-Type' RES/IP anomalies

This paper presents a continuation of the technique, derived from the full MIMDAS RES/IP/MT survey, called IPEx presented at the AEGC in 2019 (Boucher, 2019). It was originally presented as a more cost-effective, enhanced 2D reconnaissance IP investigation in areas of post-mineral cover, ensuring that a minimum-sized predefined chargeable body would not be missed. The criterion above is relevant to many mining companies. In the present case, a one-kilometre diameter represents the minimum chargeable size that should not be missed, which could correspond to the limits of the pyrite halo of a marginal porphyry hydrothermal alteration system. Two examples of modified IPEx arrays for 3D prospecting are presented: 1) two perpendicular lines with respective offset transmitters (offset-Tx) that serve as the precursor to the IPEx-3D; 2) full IPEx-3D array used for reconnaissance and immediate follow-up. Data were inverted to resolve discrete chargeable bodies, and 3D models were also confirmed by drilling. Additional forward modelling has been done to simulate the hypothetical chargeability response of a body that would have been missed by the IPEx-3D survey.