Geophysical methods of Mineral Exploration

In a layman's term exploration can be referred as just the searching or finding of something.

However  in technical terms we can define the term Mineral exploration as the systematic process of searching for either mineral deposits, groundwater resources or hydrocarbon deposits.

Basically in most cases it involves three (3) techniques which are geology, geochemistry and geophysics. However, this post want to let you know how geophysical techniques can be applied in mineral exploration so as to achieve its primary goal of determining the depth and quality of mineral resources.

As we know that geophysical techniques are sensitive to physical contrast of physical properties of the body (mineral ores) being sought and its surrounding rocks.

Geophysical Methods for Mineral Exploration

You can adapt these methods depends on your target mineral deposits as described here down,

➔ If the mineral deposit is denser than the host rocks, you can consider Gravity Method.

➔ If the mineral deposit is conductive than the host rocks, you can consider Very Low Frequency (VLF) or Horizontal Looping Electromagnetic (HLEM) Methods.

➔ If the mineral deposit contains magnetic minerals such as Hematite (Fe2O3), Magnetite (Fe3O4) you can adapt Magnetic Method.

➔ If the mineral deposit is disseminated such as Porphyry copper, you can consider an Induced Polarization (IP) Method.

Also many sulphides produce strong IP response because their mineral grains have high electronic conductivities. This is with exception to cinnabar (PbS) and sphalerite (ZnS), as these sulphides contain mineral grains that have low electronic conductivities.

➔ If the mineral deposit is associated with radioactive minerals such as Uranium, Thorium like Placer deposits e.g Monazite (ThO2 plus rare earth phosphate), gold deposits related to hydrothermal alterations, then consider the Radiometric Method.

➔ If the mineral deposit is massive and conductive such as sulphides then it will be a good approach if you apply the Self Potential (SP) Method.

➔ If what you expect to search is associated with sedimentary basins such as in hydrocarbon reservoirs then consider the Seismic Reflection Method. It is because sedimentary basins have layers that when they differ in  bulk densities  at some depths they may cause seismic waves to be reflected due to elastic contrasts.

The figure 1, here below gives a summary for the above description.

Note: IP - Induced Polarization, TEM - Transient Electromagnetics, BIF - Banded Iron Formation, SP - Self Potential

Figure 1: Table showing physical properties with their geophysical methods

If your target deposit is showing a complex association with host rocks, you can integrate more than two (2) geophysical techniques to narrow down information about the subsurface geology.

Although the effectiveness and limitations of geophysical methods are required to be employed. You need to have good primary knowledge of the deposits such as chemical, physical, mineral associations, geologic environment so as to successfully locate  mineral deposits.

Thank you for your time!

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