Radiometric surveys may be conducted on the ground or from an aircraft. They detect the concentration of potassium, uranium and thorium in rocks and soils, which are naturally radioactive. Their different chemical properties provide useful characterization of chemical or mechanical (transport) processes. For this reason, for geological mapping and exploration purposes, the technique should be considered and interpreted in geochemical terms. Whereas magnetic, electromagnetic, gravimetric or seismic sensors may detect features to depths of tens or hundreds of meters, often buried far below the near-surface geology, radiometric data are interpretable in terms of surface chemistry. Because they provide geochemical information, radiometric surveys can be useful for mapping certain rock types. Granites, for example, which are potassium-rich, produce a strong potassium signature. Potassium may also be associated with alteration zones related to certain mineral deposits, and can be a useful fingerprint for the presence of ore. Potassium signatures and/or Thorium/Potassium ratio signatures have been documented in association with gold, copper porphyry and sulphide deposits.

The map presented below depicts shaded relief, radiometric data in the form of equivalent thorium (inclination of simulated light is 45°, declination of source is 45°). Data in the eastern part of the Slave were collected along flight-lines spaced >25 km apart, whereas most data in the western part were collected along lines spaced 5 km apart.

For radiometrics, potassium is measured as a percent (%), thorium and uranium are measured in parts per million (ppm), and are referred to as eThorium and eUranium, which means equivalent thorium.