In situ gamma ray measurements for deciphering of radioactivity level in Sarihan pluton area of northeastern Turkey

Abstract

The present work utilizes in situ gamma ray spectrometric measurement data to map the surface geology of Sarihan Granitoid and its surrounding area. The study area comprises three different lithological units, namely, Hozbirikyayla Formation (limestone and sandy limestones), Sarihan Granitoid (consist of quartz monzodiorite, granodiorite and quartz diorite) and the Ophiolitic olistostromal melange (andesite, basalt, sandstone, gravelly sandstone). When lithological units are assessed according to the radioactivity characteristics, natural radionuclide contents (K-40 and radionuclides from U-238 and Th-232 series) of Hozbirikyayla limestones and ophiolitic melange rocks are lower than the Sarihan pluton. The U, Th and K radionuclide contents were found to be 0.8-5.4 ppm, 10.1-33.6 ppm and 1.29-4.41% in the Sarihan plutonic area and 0.9-5.3 ppm, 1.1-20.3 ppm and 0.04-2.71% in Horzbirikyayla formation, respectively. The element concentrations of U-238, Th-232 and K-40 of the Ophiolitic melange are 1.1-4.5 ppm, 1.6-25.3 ppm and 0.09-3.63%, respectively. Radioelement ratio maps are created for the studied area, because the parameters of radioelement ratios, eU/eTh, eU/K and eTh/K, reflect the radioactive characters of the rock and soil. The Hozbirikyayla Formation is characterized by the highest value of eU/eTh and lowest value of eTh/K. While the lowest eU/eTh and eU/K ratios were observed in the Sarihan Granodiorite, the highest value of eU/K and eTh/K were obtained in the Ophiolitic olistostromal melange. By comparing these maps with the geology, it was found that the radioelement concentrations are in good agreement with the geological properties of the region. In addition to this, the radiation hazard parameters were evaluated to assess the radiation hazard for people living in this area. It has also been found that there is no significant radiologic hazard for humans and the environment in and around studied area.