Case studies and updates about Abitibi Geophysics
What Is Induced Polarization?
Induced Polarization (IP) is used to measure the chargeability of the subsurface. The electrochemical effect, or IP Effect, can be influenced by many factors; grain size, surface area, types of minerals present (metallics vs. silicates vs. clays), type and mobility of ions within the pore fluid.
Disseminated mineral grains, for example, have a larger overall surface area providing a more effective Induced Polarization response. Understanding Induced Polarization survey data requires a knowledge of the physical rock properties and the geology, as well as the rock and mineral types present in the survey area.
Who Needs an Induced Polarization Survey?
This type of survey is useful for mining and exploration companies and in many environmental and engineering applications.
How Does an Induced Polarization Survey Work?
To perform an Induced Polarization survey, technicians place two current and two or more potential electrodes into the ground. A current is injected into the transmitting electrodes and the potential is measured at the receiving electrodes. When collecting chargeability data in an Induced Polarization survey, Resistivity data is also collected, providing two complimentary datasets in just one survey pass.
The survey grid is typically composed of lines 100 m apart and normally perpendicular to the geological strike of the survey area. The data are then processed to produce profiles, pseudosections, maps and models that are interpreted by geophysicists.
What Induced Polarization Survey Types are Available?
There are several different types of Induced Polarization geophysical surveys available: 2D surface, 3D surface and Borehole. Conventional 2D IP arrays have a limited depth of investigation (up to 250 m) but can still be useful depending on the goals of the survey. The OreVision survey is a 2D Deep IP survey that can reach depths up to 600 m while still maintaining resolution. IPower3D is surveyed on 5-line setups, with readings being taken in a variety of configurations along and between lines providing 3D coverage of the survey area.
The IPower3D survey is useful in cases where geologic strike is variable or unknown and helps to resolve complex structural problems, as well a providing a superior investigation through conductive cover. The Induced Polarization survey can also be conducted inside a borehole and provide useful information about the in-situ physical properties and signature of the mineralization and host rock.
To gain information between boreholes, farther from boreholes and beneath boreholes, a Hole-To-Hole IP survey can be conducted. Performing a BHIP survey will maximize the value of any borehole. Also, call us to learn more about our new surface and borehole approach, which uses a network of receivers on the surface, taking advantage of receivers on the surface and transmitters in the drill holes.
There are many configurations available for the various Induced Polarization survey types discussed above and a geophysicist can help to make the decision on what is best suited for your mineralization type, survey area and program goals.
What Kind of Deposits Can be Found by an Induced Polarization Survey?
Induced Polarization is an excellent and well-known tool for mapping disseminated style mineralization and sulphide mineralization associated with gold. It is also useful in detecting mineralization associated with VMS, porphyry copper, kimberlite, Ni-Cu-PGE, lead-zinc and uranium deposits.
IP can help discriminate between non-mineralized conductors, such as shear zones and faults, detect low or non-conductive sulphides, and map alteration zones. IP can also be useful for mapping clay or gravel, bedrock depth, groundwater and contamination, or for leak detection.
If you would like more information or an Induced Polarization geophysical survey, contact our specialist.