Geochimical and mineral exploration

Equipment:

SP5640 – Backpack Detector

Purpose of the experiment:

Large area survey to evaluate the radioactivity concentration of Uranium, Thorium, and Potassium.

Fundamentals:

A geochemical exploration campaign aims at locating economic mineral deposits through the recognition of concentrations of chemical components, to be called as geochemical anomaly, in surface materials such as rocks, soils, stream sediments, glacial till, water, plants, and air. The radiological characterization of surface soil, in terms of Uranium, Thorium and Potassium, proves to be also a good tool to direct excavations for mines. The main advantages of using in situ measurements are quick feedback, a large sample size, immediate repeatability of the measurement and low management costs. The areas with an enormous geodiversity have a considerable variety of stone materials that can be used both as building materials and as ornamental elements. This enormous variety also corresponds to considerable variability in the abundance of radionuclides. The world average radioactivity content in the upper continental crust is (33 ± 7) Bq/kg for ²³⁸U, (43 ± 4) Bq/kg for ²³²Th and (727 ± 60) Bq/kg for ⁴⁰K. Igneous plutonic rocks are characterized by relatively high concentrations of natural radionuclides varying over a wide range of up to 2000 Bq/kg for ⁴⁰K, 600 Bq/kg for ²³⁸U and 900 Bq/kg for ²³² Th.

Requirements:

No other tool is needed.

Carrying out the experiment:

Power on the γstream inside the red backpack. Power on the tablet and associate the two devices via Bluetooth. Take care that the γstream internal battery is charged, otherwise use the external power system.
Start the measurement campaign in land field and place the backpack on the floor almost 1m far from the trees, manhole or other construction. Set the acquisition time to about 5 minutes and see the results. If the statistic is not enough increasing the acquisition time. Repeat the measurements along the survey area.

Results:

Exemplary of in situ survey performed by using a portable NaI(Tl) scintillation detector for the determination of the radioactivity concentration of ⁴⁰ K, ²³⁸ U and ²³² Th on intrusive granite outcrops in Corsica-Sardinia (FR-IT).

Position of extractive districts in Sardinia where in situ measurements were performed.