Characteristics of REE enrichments in the weathered granitic crust, Toboali, South Bangka: Possibility for ion adsorption‐type REE mineralization

This study investigates the characteristics and fractionation of rare earth ele-ments (REEs) in the weathered products of granite from South Bangka,Indonesia. Samples were collected from two drill holes (TBKP-30 and TBKP-38) at depths ranging from 0.5 to 18 m. Analytical methods, including X-raydiffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma massspectrometry (ICP-MS), and scanning electron microscopy (SEM-EDS), wereused to examine mineral compositions and REE distribution. The parent gran-ite is an S-type biotite granite with total REE concentrations between 1081 and1279 ppm. The dominant REE-bearing minerals are REE-fluorocarbonates(synchysite, parisite) and REE-phosphates (apatite, monazite, xenotime),accompanied by REE-silicates (allanite, thorite, zircon). Fluorocarbonates(synchysite, parisite) occur filling grain boundaries of the parental granite, sug-gesting later overprinting. Monazite, xenotime, and zircon were identified aspart of the crystal lattice of residual minerals in both weathered profiles.TBKP-30, has significantly depleted in REEs with high intensity degree ofweathering and the occurrence of gibbsite minerals. TBKP-38, has ceriumenrichment in the lower profile, caused by the fixation into cerianite and/or itis incorporation with Fe-Mn hydr(oxides) along with the occurrence of kaolin-ite minerals. This study highlights the patterns of REE enrichment as a poten-tial indicator of weathering intensity, providing insights crucial for theexploration of REE deposits and the development of sustainable extractionmethods.