Airborne GeophysicsRadiometrics
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.
Please click here for a flyer about airborne magnetic surveys.
APPLICATIONS
Mineral exploration
Gold, mineral sands, uranium and rare earth elements. Please
click here for a flyer with information about our
uranium exploration techniques.
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.
TECHNIQUE
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.
The peaks associated with potassium, uranium and thorium are shown in the following gamma-ray spectrum:
EQUIPMENT SPECIFICATIONS
Pico Envirotec GRS-10+ Spectrometer
Pico Envirotec GRS-10+ Radiometric Data Acquisition System is an
advanced spectrometer utilising NaI detectors. It is a
hardware-software design system, with advanced individual detector
signal processing that reduced the potential hazards (or complex
circuitry) of "zero base shift" and practically eliminates "dead
time".
The GRS-10+ records real time calibrated summed 256 channel
spectra. In addition, a raw 512-channel spectrum from each
individual crystal is also recorded. This allows the data from
individual crystals to be post-processed to achieve better energy
calibration and as a result a high-resolution 512 channel summed
spectra.
| Recorded Spectra: | 256 or 512 channels |
|---|---|
| Data Sampling: | 1 second sample rate |
| Energy Spectra: | 50 keV (adjustable) to 3 MeV |
| Cosmic: | Energies above 3MeV are detected as cosmic rays |
| Max. count rate: | 1,000,000 per second (65,535 per channel) |
| Spectra Correction: | Automatic gain control on individual detectors |
| Dead time: | Negligible for normal detection rates |
| Configuration(s) | 16.8 litres - 4 individual detectors in 1 pack 33.6 litres - 8 individual detectors in 2 packs |
Exploranium GR-820
The Exploranium GR-820 is a modern spectrometer system that records 256 channels of summed data from either one or two crystal packs. The spectrometer employs automatic gain control to ensure stable peak positioning and therefore eliminate spectral drift.
The spectrometer system can be flown with either one or two crystal packs depending on the aircraft configuration.
| 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 |
