Induced Polarization (IP) is a commonly used geophysical survey for measuring the electrical properties of the subsurface rock.
Both IP and resistivity measurements are made by injecting an electrical current into the ground using two current electrodes which energizes the ground. Induced polarization represents the ability of rocks to briefly hold an electrical charge after the transmitted voltage is turned off. By measuring the electrical gradient between receiver electrodes, the apparent resistivity of the ground can be calculated. The survey depth and resolution can be adjusted with an increase or decrease in the spacing of the electrodes.
Depending on the targeting parameters, many different IP survey configurations can be deployed. The most common conventional deployments are Pole-Dipole, Dipole-Dipole and Gradient. These represent 2 dimensional deployments; this means the data point collected lies below a cut grid line. Anomalies are generally related back to the cut grid coordinate and are represented in 2D space.
Determining the electrical properties of the rock can provide clues in the determination of the subsurface potential. The measured electrical properties reveal valuable information about geology, geological structures and mineralization. The increase in the induced polarization effect indicates the increase in polarizable material such as disseminated sulphides. Variations within the apparent resistivity indicate variations in the geological unit, such as a siliceous alteration.