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FREQUENCY-DOMAIN ELECTROMAGNETICS

FDEM is a low-cost electromagnetic solution for shallow conductor mapping.

  • Multiple coil separations and frequencies available.
  • Simple operation, allowing survey in any environment (sand, gravel, outcrop, permafrost).
  • Inexpensive and straightforward to carry out.
  • Simple and accurate quantitative interpretation (location, width, depth, dip and conductance).
  • Investigation depth is generally ½ (to ¾) the coil separation in resistive environments.
  • Investigation depth is limited by frequency skin depth of conductive surface layer.
  • The In-phase component is highly sensitive to coil orientation and spacing.

Survey Parameters

  • Operating survey frequencies and coil separation are optimized to map local geology.
  • Readings are normally taken at intervals of ¼ the coil separation.
  • Both In-phase and Out-of-phase components of the secondary electromagnetic field are recorded.
  • Instruments: MaxMin I (9 frequencies) coupled to a MMC notebook from Apex. Coil separations from xx m to yy m are available.

Supplied Products

  • In-phase and out-of-phase stacked profile map for each frequency.

HLEM profiles over a weathered kimberlite pipe (loop separation = 75 m, frequency = 888 Hz).
The In-phase anomaly is reversed due to the magnetic nature of the source.
(Geophysics 44, Macnae, 1979)
 

Visit our Case Study Tool to see what FDEM has discovered over the years.