Mechanisms of rare earth elements dispersion from the Jiaping ion-adsorption rare earth deposit, Guangxi, China: implications for exploration

Ion-adsorption rare earth deposits (IAREDs) supply most of the world’s heavy rare earth elements (HREE), yet the downstream dispersion and phase partitioning of rare earth elements (REE) remain poorly constrained. We analyzed the operationally dissolved fraction (<0.45 μm), suspended particulate matter (SPM), and bed sediment along a 4.5-km stream draining the unmined Jiaping deposit in Guangxi, South China. The results of this study show that REE concentrations exhibit downstream attenuation across all media, with sediments (98.44–255.31 ppm) and SPM (66.28–182.56 ppm) constituting primary reservoirs over the dissolved phase (0.53–1.21 ppb). As pH increased from 5.28 to 7.04, thermodynamic modeling indicated a shift from free REE 3+ ions toward carbonate complexes. This shift promoted preferential HREE association with Fe-(oxy)hydroxides and particle aggregation, producing relative light REE enrichment in the dissolved and suspended fractions and HREE enrichment in bed sediment. SPM δCe increased from 0.89 to 1.55, consistent with oxidative Ce scavenging and aggregation of Ce-rich colloids. Bed sediment retained closer correspondence to the parent granite and regolith in (La/Sm) N and δEu. These results support two concurrent pathways: detrital transport preserves source signatures in bed sediment, whereas aqueous–colloidal transport modifies dissolved and suspended signatures. Under dry-season baseflow conditions, bed sediment was the most reliable sampling medium, providing a mechanistic basis for regional IARED exploration.