As the term is used in geophysical exploration, induced polarization means the anomalous storage of electrical charge in rocks, as a result of complicated electrochemical effects which take place during current flow. These effects may be associated with the oxidation or reduction of metallic minerals, as current passes through their surfaces, or they may be associated with variations in ion mobility within the pore structure of a rock. Continuous measurement of induced polarization effects in wells has been used as a well logging method. Current in the form of D. -C. pulses is supplied to a pair of in hole electrodes, while the transient decay voltages following these pulses are detected with a second pair of electrodes and recorded. Induced polarization logs are useful in evaluating mineral prospect boreholes, but such measurements may also have some application in evaluating the permeability in sedimentary rocks.

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