Induced polarization (M-16)

1. Q: How does it work?
   A: A time-varying current is inserted into the ground. The resultant voltage, as a function of time, is recorded and analyzed for the 'induced polarization' effect. The dominant frequency of this effect occurs in a frequency band near 1-3 Hz.
   

2. Q: What is the geologic model?
   A: The model is of disseminated mineralization in which the conductive sulphides are not connected but occur in an insulative matrix. Clay minerals also show a moderate IP effect. Landfill detection, including depth to an impermeable layer, is sometime measured.
   

3. Q: What are the requirements?
   A: Specialized transmitters and voltage recorders are used to measure the IP effect. The current electrodes are dug into the ground and nonpolarizing potential electrodes are used to sense the impressed voltages. Data is usually acquired with the dipole-dipole array.
   

4. Q: What are the pitfalls?
   A: Noneconomic minerals dominate geology. Iron sulphides (pyrite) live up to their reputation as fool's gold. EM coupling is a problem in conductive areas. Experienced mining geologists are required as consultants for application of this method. The use in environmental projects is just beginning but the urban environment of many such projects makes the detection of the IP effect of clays tricky.
   

5. Q: What logistics are needed?
   A: Crew size is 2-3 persons with at least one professional to guide the work. In case of deep investigations a large (5-15 KW) motor-generator transmitter may be required.
   

6. Q: What are the deliverables?
   A: Project and station locations and acquisition parameters are incluced. Cross-sections of the data, data inversions, and contour maps vs. depth (if sufficient data is acquired) are parts of the report.
   

7. No additional detail is available about this method on this website.