Mineralogical control and characteristics of rare earth elements occurrence in Carboniferous bauxites from western Henan Province, north China: A XRD, SEM-EDS and LA-ICP-MS analysis

摘要

High concentrations of rare earth elements (REE) are found in the bauxite deposits in the Songqi area of Henan Province, North China. However, no studies have been carried out on the occurrences of REE in these bauxite ores. In this study we explored the REE occurrence and their possible enrichment mechanism in the Songqi bauxite deposits using petrographic observation, X-ray diffraction (XRD), scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), and LA-ICP-MS techniques. The major aluminum-rich ore mineral in the Songqi bauxite deposits is diaspore, and other coexisting minerals include clay mineral aggregates, with minor amounts of hematite, pyrite, anatase, and zircon. The bauxite ores are rich in REE and also some other critical metals (Li, Zr, Nb, and Ga). Most of the REE are adsorbed in the form of ions on the surface of clay minerals and diaspore, and some heavy rare earth elements (HREE) exist in the form of xenotime. The SEM-EDS and LA-ICP-MS analyses show that REE is closely related to the content of P and therefore it is possible that other dispersed and minor P-bearing rare earth minerals may occur in the bauxite deposits except for the possible coadsorption of P and REE in the clays and diaspore.