In terms of conducting geophysical surveys, gamma spectrometry or airborne radiometric surveys can be employed as a means of detecting gamma rays or natural radioactive emanations. This detectable radiation comes from the decaying of some of the radioactive natural elements occurring in the Earth. For geological mapping, three elements are most diagnostically useful: potassium, uranium and thorium.
A radiometric survey is capable of detecting the presence of U, Th, and K at the Earth's surface level. The data attained during a geophysical survey is mainly used for the following purposes:
- Detecting the presence of uranium
- Locating other mineral deposits
- Fluctuations in concentration levels of U, Th. and K – data linked to changes in lithology
- Tool for reconnaissance geological mapping
There are several variables that can influence the measurements and data acquired during a radiometric geophysical survey. Successful data acquisition in airborne radiometric surveys depends upon the following factors:
- Influence of cosmic radiation
- Certain meteorological conditions (precipitation in the previous 24 hours period, or accumulation of snow)
- Speed of the aircraft during acquisition
- Volume of the crystal packs on board the aircraft (minimal acceptable volume is considered to be one pack, ~21 litres or 1,280 cubic inches)
- Topography of the area to be surveyed
An airborne gamma-ray spectrometer can be calibrated to selectively record "windows" corresponding to the energy levels of interest. The on-board radiometric packs are designed to acquire precise data by measuring tiny, high frequency, high energy bursts that are emitted by the isotopes of the elements in question such as uranium.
Gamma spectrometry is a method of geophysical exploration that can offer highly relevant data for mapping surface lithologes and for mineral prospecting. Along with aeromagnetic and electromagnetic surveys, gamma spectrometry is a common method used in geophysical exploration.
(Source; AGSO Journal of Australian Geology and Geophysics
Specialists in Airborne Geophysical Surveys
Terraquest was established in 1984 and since then, our dedicated team has flown over 1,500 airborne geophysical surveys using both fixed wing and helicopter platforms. Our professional crews provide significant experience having carried out airborne magnetic surveys, airborne gravity surveys, airborne radiometric surveys, and airborne electromagnetic surveys on five continents.
Our quality data sets have been utilized in the exploration for base and precious metals, kimberlite, hydrocarbons, uranium, rare earth minerals and water. The company has performed exemplary surveys for both small and large exploration groups as well as many government agencies. References can be provided upon request. Visit
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Ed. GMH