Large loop time-domain EM has been a staple in mineral exploration and groundwater investigations for decades. Like all TDEM systems, it relies on a transmitter generating a primary magnetic field inducing eddy current in the ground. As the transmitter is shut off, these eddy currency decay and produce a secondary magnetic field that is recorded by the receiver. The decay process is modified by conditions in the ground and geology.
These surveys involve laying out large loops of wire, often a few hundred metres in any direction, to image deep into the ground. AXIOM Group maintained a variety of instruments that allow investigation depths of 500 to 1000 metres.
Large loop surveys are adaptable and can be deployed for target tracking and refinement (moving loop) as well as to collect information on depth of anomalies or in areas with limited information (conventional single loop).
AXIOM Group maintains transmitters and receivers from EMIT, Geonics, and Pheonix Geophysics. B-field and dB/dt sensors are available.
Common Applications:
- Ore body targeting and geometry
- Athabasca uranium and volcanogenic massive sulphide exploration
- Follow-up on airborne EM anomalies
- Buried object or infrastructure detection
- Aquifer mapping
- Saltwater intrusion or brackish water mapping
- Bedrock topography
- Water table depth
- Karst or fracture detection
- Paleochannel mapping
- Permafrost mapping
- Aggregate exploration