Airborne magnetic surveys are a cost-effective and rapid technique for measuring the strength of the Earth’s magnetic field. Magnetic susceptibility is related to the amount of magnetic accessory minerals present in all rocks that contain iron such as magnetite, hematite and pyrrhotite. A magnetic survey can map out changes in the quantity of magnetic minerals as well as associated rock types.
Therefore, for mining, a magnetic map can help locate mineral deposits by identifying specific rock types and geological features. For oil and gas, magnetic maps can help accurately define depth to basement, basement property changes and the presence of basinal areas and volcanics. High resolution magnetic surveys can provide information on faulting and bedding in non-volcanic sedimentary areas, where mineralisation along subsurface boundaries can produce a subtle magnetic signature, measurable from the air.
Magnetic datasets have additional application in hazard detection (natural/UXO), windfarm infrastructure planning and geothermal heatflow mapping.
Magnetic surveys can be conducted either from the air or on the ground with a magnetometer. The interpretation of magnetic measurements concentrates on the identification of geologic units, which are identified in areas with a distinctive magnetic signature (i.e., magnitude, shape, texture, and trend). Volcanic intrusions such as sills, dykes, and lava flows carry accessory magnetite. Additionally, magnetic surveys can be successfully utilised to accurately demarcate the location of dykes in coalfields.