In situ measurements of radionuclide concentrations in south of Mugla city, Turkey

The paper presents distribution of radionuclide elements for different samples of igneous, metamorphic and sedimentary rocks in the south of Mugla city, Turkey. The composite image maps for each of radioelement ratios (eU, eTh and K), radiogenic heat-producing map (RHP) and absorbed dose rate of these radionuclides in air were calculated and generated anomaly maps. The obtained results were compared with geological units of the study area. It has been observed that western side of the study area (the Bodrum Peninsula) is mainly characterized volcanic rocks that display high radioactivity concentrations (for U, Th, and K, 120.2 Bq/kg, 101.60 Bq/kg, and 690.1 Bq/kg, respectively). The latite–andesite association causes higher Th concentrations (varying between 1.5 and 101.6 Bq/kg). Higher U and Th anomalies are close relation with the mineral compositions of the volcanic rocks and their silica contents. Due to K-bearing minerals such as K-feldspar (orthoclase, sanidine, biotite) higher K concentrations are determined. On the other hand, metamorphic and sedimentary rocks is dominant in the eastern side of the study area. The sedimentary units have the lowest radioactive concentrations (for U, Th, and K, 8, 0.20, and 24 Bq/kg, respectively), whereas marble and cherty marbles has higher U and K concentrations. It has been also seen that schist and calc-schists exhibit important thorium enrichment (80–100 Bq/kg).