Case study: TomaGold Corp’s - Obalski Project, Quebec, Canada 

The Obalski Project is a former mine site located in the heart of the Chibougamau mining camp, which hosts several gold and copper mineralized zones. Obalski is known to host gold and copper and is comprised of 6 known mineralized zones. Its mineralization occurs as sulphide-rich quartz-carbonate veins within highly chloritized, carbonated and pyritized shear zones. The mineralization varies from massive to disseminated and the quartz veining is injected within fractures/shears. The project had a vast amount of historical, but shallow, exploration data. The conventional 2D IP limited the depth of investigation and raised directional bias, therefore a 3D survey was needed to maximize the quality of new targets. 

Our solution – DasVision 3D IP 

Abitibi Geophysics was contracted to carry out a campaign of geophysical surveys in two phases in 2021 and 2022 in the field and through drilling. After promising results from the initial phase of the program a second extension block was added to the south. The final survey is comprised of two DasVision blocks covering an area of 0.7 km2, using a receiver mesh of 150 m by 100 m, with current injections spaced at 50 m. This detailed survey provided a 3D inversion model with a depth of investigation of 400 m. 

Our DasVision survey has outlined the known zones and identified several unexplored distinctive polarizable anomalies within the Obalski Project. DasVision is a 3D resistivity and induced polarization surveys method that uses independent receivers to enhance the exploration effectiveness by avoiding the installation of kilometers of cable. Minimizing physical links between receivers not only makes surveying cost effective, but it also makes it easier in highly vegetated, urbanized, or rough topography areas. Its advanced processing renders detailed sampling and high-density datasets that can be used to create 3D inversion models, helping guide exploration and mining activities with greater accuracy and efficiency. It allows the user to record and store transmitter current and received voltage in full waveform measurements. Designed for the exploration at depth, it can also successfully model smaller scale and near surface sources. 

Results 

The known mineralized zones were well mapped by the chargeability, along with new unexplored anomalies observed southwest in the extension of the deposit. The survey was extended and completed in another phase to fully resolve these anomalies. Drillholes were proposed on the most prospective anomalies. Abitibi Geophysics was therefore able to identify several resistivity and chargeability anomalies and make drilling recommendations. 

Following these recommendations, a program of six holes totalling 2,958 metres was drilled on high chargeability anomalies. Hole OBS-22-020 tested a chargeable and resistive anomaly while holes OBS-22-021 to OBS-22-025 tested two low-resistivity/high-chargeability anomalies. Additional surveys (InfiniTEM XL and a H2H 3D IP) were completed in another phase to fully resolve these anomalies.

The known mineralized zones were well mapped by the chargeability, along with new unexplored anomalies were observed southwest in the extension of the Obalski deposit. The survey was extended and completed in another phase to fully resolved the anomalies. Drillholes were proposed on the most prospective anomalies.