Geophysical methods in mineral exploration are non-invasive techniques used to detect and map subsurface mineral resources by measuring the physical differences between rock types. These methods help geologists identify potential ore bodies, map geological structures, and guide drilling programs without the need for extensive excavation. The most common geophysical methods used in mineral exploration include:
Magnetic surveys: Detect variations in the Earth’s magnetic field caused by magnetic minerals like magnetite and pyrrhotite. These surveys help identify iron-ore bodies, skarn deposits, and geological structures associated with mineralization.
Gravity surveys: Measure variations in the Earth’s gravitational field to detect dense ore bodies, such as massive sulfide or chromite deposits. They are especially useful for mapping large-scale structures and dense minerals.
Electromagnetic (EM) surveys: Detect differences in electrical conductivity in the subsurface, useful for finding conductive ores such as base metal sulfides, graphite, or kimberlite pipes in diamond exploration.
Seismic methods: Use the propagation of seismic waves to image subsurface geology, helping to delineate mineralized zones or structural features at greater depths. Both reflection and refraction techniques are used, with reflection being preferred for deeper, more complex targets.
Electrical and resistivity methods: Measure the ground’s resistance to electrical current flow. Induced polarization (IP) and resistivity methods are particularly effective in detecting disseminated sulphide minerals and alteration zones related to mineralization.
Radiometric surveys: Measure natural radioactivity (from uranium, thorium, and potassium) to help map certain types of mineral deposits and lithological variations.
These geophysical methods can be deployed using ground-based surveys for detailed studies or airborne techniques for regional reconnaissance. Data from several methods are often combined to create 3D models of the subsurface, improving the accuracy of exploration and reducing the risks and costs associated with drilling. While these methods are powerful and widely used, they typically provide indirect evidence of mineralization, meaning that exploratory drilling and sampling remain essential to confirm mineral deposits.
To sum up, geophysical methods are fundamental tools for modern mineral exploration, guiding efficient and sustainable resource discovery by offering a detailed look below the surface without the need for destructive or expensive excavation.
