When a current is passed through earth materials not containing metallic minerals, the amount of current is related to the driving potential only by the ohmic resistance of the formations involved. When the formations contain metallic minerals, the currents give rise to an exchange of ions at the surface of contact between the minerals and the electrolytes dissolved in the fluid filling the inter-granular pore spaces.
This electrochemical exchange creates a voltage which opposes the current flow though the material, and an added voltage is necessary to overcome the barrier thus created. The extra voltage necessary to drive current though the barrier is sometimes referred to as the over voltage.
When the externally applied current is turned off, the electrochemical voltages at the metallic grain surfaces are dissipated, but not instantaneously. The decaying voltages can be measured for a time after the current is switched off. The voltage is observed to vary with time.
Induced Polarization method involves using special measuring electrodes – non-polarize electrodes. The technique requires careful handling on behalf of the operator and it can be influenced very easy by free running electric currents.
It is the best method of investigating the disseminated mineralization, but it is also used for characterizing the hydro-geological conditions (the clay in the aquifer layer has a manifestation of the induced polarization).
Applications of induced polarization method:
- Detection and mapping layers of clay;
- Bedrock depth;
- Identification of fractures and fissures;
- The thickness of the layers;
- Mapping of sand and gravel deposits;
- Sol / Layers unconsolidated;
- Properties of soil and rock;
- Mineral Exploration;
- Geological mapping;
- Mapping groundwater depth;
- Leak Detection inorganic pollutants;
- Leaking landfill;
- Intrusion of salt water;
- Characterization of buried waste;
- Delimitation disposition pits / trenches;
- The size and limits of buried deposits;
- Maps of groundwater contamination;