Airborne magnetometry and magnetic gradiometry
The magnetic method of geophysical exploration (magnetometric or magnetic prospecting) is based on measuring the magnitude or components of the Earth’s magnetic flux density. Magnetic anomalies arise from contrasts in the magnetic properties of rocks and mineral resources.
Measurements are made using new-generation AEROMASTER multichannel quantum airborne magnetometers, equipped with high-sensitivity CS-VL or CS-3 sensors (Scintrex, Canada) or G-824A sensors (Geometrics, USA).
Principal magnetometer specifications:
- sensitivity threshold: 0.001 nT
- sampling frequency: up to 1000 Hz
- measurement range: 15,000–130,000 nT
- permissible field gradient: up to 20,000 nT/m
- operating temperature range: −40 to +50 °C
Main objectives:
- structural and tectonic mapping to establish the hierarchy, relationships and kinematics of major faults;
- delineation of mineralised and skarn-alteration zones;
- mapping of intrusive bodies of different compositions, both exposed and buried;
- identification and mapping of metasomatic zones.
Technical features:
Depending on the aircraft type, the magnetometer sensor can be housed in a towed bird suspended on a 45–70 m cable, rigidly mounted in a dedicated tail stinger, or installed in special wing-mounted pods. In the latter configuration, an additional three-component fluxgate magnetometer is used for dynamic compensation of magnetic deviation interference caused by the aircraft fuselage. Compensation can be performed in real time by a dedicated onboard software module or during post-processing.
UAVs and ultralight aircraft enable low-altitude surveys.
For high-resolution surveys, the GPS receiver antenna is installed close to the magnetometer sensor. Differential operation of the navigation system limits the position error of the actual measurement points to a few tens of centimetres.
Natural variations in the Earth’s magnetic field are accounted for using a network of automatic digital ground-based quantum magnetic variation stations capable of autonomous operation.
