Geochemical Characterization and Presence of Rare Earth Elements in the Recent Depositions at the Islands of the Eastern Bay of Bengal, Bangladesh

Abstract

This study presents geochemical characterization, as well as, quantification of rare earth elements in the recent beach deposition at the two major islands of the eastern Bay of Bengal-Kutubdia and Moheshkhali. Placer sand samples from near surface depositions were analyzed by heavy mineral separation, mineralogical identification, chemical composition and elemental mapping. X-ray diffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) were used to obtain these results. The heavy mineral concentration in different raw sand samples resulted by heavy liquid separation technique revealed that the average abundance of heavy minerals is 69.67% in Kutubdia island and 9.32% in Moheshkhali island, respectively. The X-ray patterns of Kutubdia and Moheshkhali sand samples show the presence of zircon, quartz, hematite, magnetite, ilmenite, chromite, kyanite, anatase, rutile and garnet. Chemical composition of heavy mineral sands from Kutubdia and Moheshkhali islands were analyzed using X-ray fluorescence method (XRF) for major oxides and trace elements. The concentration is of Na2O, MgO, Al2O3, SiO2, P, K2O, CaO, TiO2, V2O5, Cr2O3, MnO, Fe2O3, CoO, ZnO, SrO, Y2O3 ZrO2, Nb2O5, MoO3, HfO2, WO3, ThO2, U3O8, CeO2, Nd2O and Er2O3 were determined. A significant amount of various rare earth elements (REEs) in the elemental composition of few samples was also identified. The study is expected to be useful in the baseline and environmental aspects of both the islands.