Airborne gamma-ray spectrometry (radiometrics) is an effective geological mapping tool in many different environments and has been applied to mineral, environmental, geothermal, hydrocarbon and water investigations.
Airborne gamma ray spectroscopy (radiometrics) measures the radioactive emissions from the soil surface which results from the natural decay of isotopes in the soil.
Airborne radiometric measurements have traditionally been obtained for four energy bands. These bands are indicative of total radiometric count and uranium, thorium and potassium concentrations. The data is usually obtained at an elevation of between 40 and 150m above ground level and a measurement is recorded every 50 – 60 metres along flight lines. Final data resolution is primarily determined by survey line spacing and elevation.
Emissions of gamma radiation from the land surface vary with many factors but essentially depend on the composition of radionuclides within the top 30cm of the soil surface. The composition depends on the parent material and the degree of breakdown, loss and/or accession, and therefore generally reflects the parent material and weathering.
Potassium, uranium and thorium emit gamma-rays with specific energies during their decay sequence. The gamma-ray spectrum is measured using crystals that scintillate during a gamma-ray interaction.
Photomultipliers convert the scintillation to a voltage that is directly proportional to the energy of the gamma ray. Using calibration data and advanced processing techniques the raw gamma-ray data is converted to ground radioelement concentrations.
|Recorded Spectra:||256 channel summed spectra|
|Data Sampling:||1 second sample rate|
|Energy Spectra:||175 keV to 3 MeV|
|Cosmic:||Energies above 3 MeV are detected as cosmic rays|
|Max. count rate:||1,000,000 per second|
|Spectra Correction:||Automatic gain control on individual detectors|
|Dead time:||Less than 5 microseconds|
|Configuration(s)||16.8 litres – 4 individual detectors in 1 pack
33.6 litres – 8 individual detectors in 2 packs
Mineral exploration – Gold, mineral, sands, uranium and rare earth elements.
Geothermal exploration – Potassic alteration.
Hydrocarbon exploration – Potassic/uranium alteration.
Geological Mapping – Mineral, engineering and water exploration applications and paleodrainage systems.
Contamination mapping and detection – Military and industrial waste (eg. 137Cs and 60Co).
Emergency response – Fallout and nuclear contamination.