Investigation of natural radionuclide variations and the possible uranium migration by testing with gamma-ray spectrometer: An example from Tuğlu Tepe and Deliler Sites in Şefaatli/Yozgat, Central Anatolia Region, Turkey

The in-situ gamma-ray spectrometry measurements are performed to define and map natural radionuclide variations and the possible uranium migration on the sandstone in the Central Anatolia Region and Deliler sites in Yozgat, Turkey. The concentrations of radionuclide (eU, eTh, K%) and dose rate values were measured totally on 384 points in both areas with a duration of 5 min at each measurement point. The radionuclide ratios (eTh/K, eU/K, and eU/eTh), geochemical indicators (Ume, F parameter and eU-(eTh/3,5) rate) of uranium remobilization in the rocks, and the hazard parameters were calculated and evaluated by using measured data. The separation of uranium-rich or poor areas was made easily and associated with lithological formations by evaluating all the maps produced together. While the highest concentrations of radionuclide, and dose rate values were recorded in the sandstone units under the cover layer that are Eocene neritic limestones, the lowest concentration values and dose rate were measured on siltstone and claystone in the northern part of the Tuğlu Tepe area. At the Deliler study area, the lower anomaly zones are coincide with the soils used for the cultivation of chickpeas consists of loosely cemented sandy clay siltstone, claystone, gravel, sand, silt, and clay whereas the highest concentrations observed in the outcropped sandstone and limestones. It can be seen that the study areas have variable radioactivity levels as a result of both the weathering from the surrounding granitic rocks and the transport and accumulation of sediments through different factors. On sandstones serving as reservoir rock for uranium mineralization in both Tuğlu Tepe and Deliler sites, there is a uranium migration from the granitic rocks towards these masses and sandstones have been enriched by uranium. As a result of the evaluations, it has been seen that the areas showing uranium enrichment originated from migration can be determined very easily by radioactivity measurements, which is a fast, economical and effective method.