Field gamma-ray spectrometry on the Vulcano island (Aeolian Arc, Italy)

In situ NaI(Tl) gamma-ray spectrometric measurements on the Vulcano island show that the magmatic evolution of the main structural units is reflected by the uranium, thorium and potassium concentrations. The results allowed u s to delineate two temporal and radiometric districts. The older district c omprises lava flows and pyroclastics of mafic composition forming the whole southern part of the island, with an equivalent uranium concentration and an eTh/eU ratio ranging, on average, from 2.9 to 3.4 ppm and from 2.4 to 4. 1, respectively. Rocks of the younger district, ranging from leucitic tephr itic and trachytic to rhyolitic composition, show higher K contents (about 6%) and more variable eTh/eU ratios (2.4-6.1). (C) 1999 Elsevier Science Lt d. All rights reserved.