Assessment of mineralogical composition of the natural radionuclide rich beach sands in Geyikli, Çanakkale (Western Anatolia)

This study investigates the mineralogical composition of radionuclide-rich beach sands along the coast of the Miocene Ezine-Ayvacık magmatic complex including Kestanbol pluton, in Western Anatolia. The distribution of the radionuclides shows variations along the coast with the highest recorded radioactivity at Hantepe Beach, where specific activities of the²³⁸U-, and²³²Th-series are significantly high, while⁴⁰K concentrations are moderate. In contrast, the southern beaches, dominated by material from the Kestanbol pluton, have higher⁴⁰K concentrations but lower²³⁸U-, and²³²Th-series specific activities than Hantepe beach. Using gamma spectrometry, bulk geochemical, and in-situ analyses, we provide a detailed assessment of the mineralogical composition of the sand samples and the primordial radionuclide concentrations of the different lithologies within the Kestanbol pluton, such as felsic veins, nepheline monzogabbro and tephriphonolitic dykes. We suggest that thorite group minerals control the high radioactivity at Hantepe beach, and pegmatitic veins of the Kestanbol pluton are the main source rock for thorite minerals. However, all the products of Miocene magmatism in the region exhibit elevated radioelement and radionuclide contents suggesting that other accessory and rock-forming minerals are the potential contributors to the high natural background radiation in the area.