Leviathan Discovery – Porphyry Copper – Hercules Metals
Idaho, USA
Overview
The Hercules Project is located in western Idaho. A series of stacked thrust sheets emplaced rhyolitehosted silver (+/- lead-zinc) mineralization through the property. Historical drilling up to 1988 defined several zones of silver mineralization at depths generally less than 90 meters. Prior to Hercules, the project had never seen a modern, systematic exploration program. See video
The Situation
In 2022, Hercules completed soil and rock chip sampling, hyperspectral analysis, geological mapping, drone magnetics, and 3D IP surveying, followed by an initial drill program to twin historic holes. These programs were designed to further explore the existing silver vein systems and to identify potential extensions laterally and to depth.
The 2022 DIAS32 3D IP survey identified near-surface chargeability responses as expected over the known mineralized zones, but also identified a large chargeability anomaly at depth, below historical drilling, and over a continuous strike length of 1.8 kilometres.
The Phase II drill program in the summer of 2023 tested extensions of the existing silver mineralization, new silver targets, a potential near-surface porphyry target in the Hercules Rhyolite, and the large, untested chargeability anomaly at depth. Five deep drill holes extending below the Hercules Rhyolite encountered strong phyllic alteration typical of the margins of a porphyry system over approximately 450 m x 500 m. Drillhole HER-23-05, designed to test the large blind chargeability anomaly, intersected Ag-Pb-Zn-Mn mineralization in the near surface but then intersected 185 m of 0.84% Cu and 111 ppm Mo from 246 m to 431.2 m at the end of the hole. Additional step-out holes drilled to test the chargeability anomaly to the southeast of HER-23-05, intersected similar alteration, veining and copper mineralization. This drilling confirmed the presence of a large mineralized porphyry system at Hercules.
This deep drilling confirmed a thin conglomerate layer, likely a paleo-erosional surface, that separates the overlying Hercules Rhyolite from the underlying porphyry system. Molybdenum mineralization begins immediately below the conglomerate, but the copper appears to have been leached within the paleo-weathered zone. The copper is enriched below this leach zone, and then the mineralization transitions to a typical pyrite-chalcopyrite (phyllic) assemblage which extends to the bottom of the hole.
Following the discovery in 2023, a property-wide deep-seeking DIAS32 3D IP survey was designed to explore the new Leviathan Porphyry laterally and to greater depth than the original survey. The 3D resistivity and chargeability models from this survey have been integrated with the magnetic model and other geological and geochemical data sets to produce a complete model of the porphyry system. This 3D block model reveals a coherent, kilometer-scale NE-SW trending, southeast dipping, porphyry system. Strong correlation with both the chargeability and magnetic models provides confidence in drill targeting of the significant expansion potential of the deposit.
The Conclusion
The discovery of the Leviathan porphyry resulted in Barrick injecting $23M in equity into the exploration program at Hercules. An unprecedented staking rush has occurred as a direct result of the Hercules Metals’ discovery, and 1,000’s of new claims have been staked, demonstrating the potential regional implications of the discovery.
