Rare Earth Elements Geochemistry and ²³⁴U/²³⁸U, ²³⁵U/²³⁸U Isotope Ratios of the Kanyakumari Beach Placer Deposits: Occurrence and Provenance

Geochemical studies of rare earth elements (REEs) as well as major and trace elements were conducted on the beach placer sands from the Kanyakumari coastal region, a well-known high background natural radiation area (HBNRA). For the first time, uranium isotope ratios (U-234/U-238 and U-235/U-238) were determined in the study area to investigate the provenance and leaching of U from the beach sands. Inductively coupled plasma mass spectrometry was used for the measurement of REEs and trace elements whereas thermal ionization mass spectrometry (TIMS) was used for the measurement of U isotope ratios. Sigma REEs were found to be in the range of 778.93 to 15,007. 54 mu g/g, whereas Sigma Light REEs were in the range of 770.58 to 14,860.80 mu g/g and Sigma Heavy REEs varied from 8.35 to 146.74 mu g/g. The enrichment factor showed the LREEs Th and U were extremely enriched in the Kanyakumari beach placer sands. The U-235/U-238 isotope ratios were similar to the natural terrestrial ratio value. The U-234/U-238 activity ratio varied from 0.995 to 1.071, and showed the prevailing secular equilibrium among them. The delta U-238 results could, to some extent, explain the U fractionation and source.