Abstract

SimPEG (Simulation and Parameter Estimation in Geophysics) is an open-source python package for geophysical forward modelling and inversion. We demonstrate the utility of SimPEG to improve 3D EM inversion models and advance exploration outcomes using ground electromagnetic (EM) data, collected on the Portuguese side of the Iberian Pyrite Belt. The EM dataset was collected in a mineral concession in close proximity to the giant VMS deposit complexes at Aljustrel and Neves Corvo. The processing and inversion of EM data remains practically difficult due to variable data formats, unit conventions and numerous system parameters required to accurately represent a geophysical survey.  A data processing and inversion workflow, implemented in Geoscience ANALYST software, is outlined, that documents the steps required to achieve efficient and effective inversion modelling and interpretation of this large ground EM dataset. Throughout, the inversion results are compared to a variety of approaches used on this data including, decay analysis, 1D inversion, plate models and established 3D EM inversion programs (UBC-GIF’s H3Dtdinv). The outcome of the 3D modelling has been interpreted to be a very interesting localized conductivity bright spot, in a favourable structural position, at the end of an interpreted thrust ramp. This result is a compelling exploration target made possible because of the 3D inversion. The presentation is an updated version of the talk given at the KEGS symposium in 2023. Since then, new developments have been made, both with SimPEG modelling package and for this exploration target. Drilling that was carried out in the 2023 season is presented and results from that drilling campaign are presented with interesting implications for the interpretation of 3D EM inversions in this setting.

Bio

Scott is Mira’s Global Director of Consulting who brings general expertise in geophysical modelling and inversion, along with extensive borehole, ground, marine, and airborne EM interpretation and processing experience. He has worked in Canada and internationally on oil and gas, uranium, and base metal exploration teams, with a track record of proven discovery.