Ground GeophysicsCSAMT
The Controlled Source Audio-Frequency Magneto Tellurics (CSAMT) technique is used to map the apparent resistivity of the ground. It has much greater lateral resolution and depth penetration than ground EM but is only suited to areas where there is either a resistive overburden or a thin conductive overburden.
CSAMT can map the resistivity from 20m up to 2000m below the Earth's surface. The depth of penetration is dependant on the survey configuration, local geology, electrical noise and the resistivity contrasts.
APPLICATIONS
CSAMT has been successfully used in the following applications:
- Mineral exploration
- Petroleum exploration
- Geothermal resource mapping
- Groundwater exploration
- Mapping geological structure and lithology
- Mapping of old mine sites
- Mapping of industrial contaminants
- Engineering projects
TECHNIQUE
The technique uses a grounded electrical dipole transmitter to produce frequencies between 0.125 and 8000 Hz. The magnitude and phase of the electrical and magnetic fields that result are measured between 500m to 15km away from the transmitter.
The apparent or Cargniard resistivity is calculated from the magnitude of the electrical and magnetic fields and the transmitted frequency.
The Cagniard Resistivity and frequency is used to calculate depth. Geological structures are modelled from the phase difference between the electrical and magnetic field.
Shallow information is contained in the high frequency transmissions whereas lower structures are determined from low frequency transmissions.
EQUIPMENT SPECIFICATIONS
GPX Surveys uses Zonge Engineering equipment for CSAMT surveys. Click on the links for equipment specifications.
Transmitters
Zonge Engineering GGT-3, GGT-10 & GGT-30
Receiver
Zonge Engineering GDP-32