Exploration under cover is the new frontier of discovery in maturing mining districts as outcropping deposits dwindle. Success in these challenging environments depends on integrating geological, geochemical, hydrogeochemical, and geophysical techniques, with approaches tailored to deposit style, host rocks, and cover type.
A robust understanding of the fundamental geology and deposit mineral systems is key to discovery in any terrain. Building geological models under cover is particularly challenging. At SRK, geophysical data (principally magnetics and gravity) are interpreted within a geological framework, assisted by machine learning (ML) classifications. ML models are trained on mapped outcrop areas and then applied under cover.
The mineral systems approach provides a conceptual framework that translates ore-forming processes into practical exploration criteria, emphasising indirect proxies at regional scales and direct detection methods at prospect scales. At depth or under cover, indirect proxies are often more evident; however, surface geochemistry and geophysical parameters such as chargeability and conductivity can directly detect mineralisation.
Exploration, including in areas under cover, is most effective when conducted through a phased, risk-managed approach, each phase narrows the search area and increases the intensity and cost of investigation. Recent approaches to regional scale/initial phases combine mineral systems models, structural geology, and broad geophysical and hydrogeochemical surveys. For example, regional airborne magnetics and gravity are used to map major structures and lithological domains, while hydrogeochemical assays of ground and surface waters help detect dispersion halos from concealed mineralisation.
As target areas are refined, exploration shifts to local scale where direct detection methods are prevalent. Here, detailed drone or ground geophysics (magnetic, electromagnetic, induced polarisation) are combined with high-resolution geochemical sampling—such as partial-leach soils (ionic) and, more rarely, vegetation geochemistry— to define drill targets. The exact combination of methods is adapted to the target deposit type, depth of cover, and weathering environment.
It is important that exploration remains an iterative process. Geological models inferred from geophysics, and mineralisation targets defined by direct detection methods, are ultimately validated by drilling. Updating models is key to ultimate success, and an ongoing cycle of mapping, modelling, predicting, and validating ensures that interpretations remain grounded in reality—even as exploration pushes into deeper terranes.
Mineral exploration under cover is a multidisciplinary, phased endeavour. Exploration programs build an understanding of the fundamental geology through field mapping, remote sensing, and geophysics—inferring continuity beneath cover through geological experience supported by machine learning and modelling—and validating predictions with drilling. By integrating mineral systems thinking, structural geology, geophysics, and geochemistry at every stage, and by adapting methods to the specific geological and weathering context, explorers can reduce risk, focus resources, and achieve real discovery success in challenging terrains.
