Weathering and recycling controls on rare earth element behavior: A comparative study on granitic, basaltic and aeolian red soil crusts

Intense chemical weathering and sedimentary recycling have produced widespread REE-enriched red soil crusts in South China. This study compares REE fractionation and mobility across three representative regolith types: granitic (YQ), basaltic (ZJ), and aeolian lateritic (LZ). Total REE concentrations follow the order of YQ (512 ± 66 ppm) > ZJ (153 ± 38 ppm) > LZ (82 ± 35 ppm). The YQ profile is enriched in light REE (LREE), while heavy REE (HREE) are more readily leached during silicate decomposition. In contrast, the ZJ profile—rich in Fe–Mn (hydr)oxides—retains middle REE (MREE) due to redox-sensitive mineral transformations and surface complexation, but exhibits LREE depletion. The LZ profile shows the lowest total REE, but is relative enriched in HREE, reflecting the combined effects of quartz dilution and the accumulation of refractory detrital minerals such as zircon. Beyond lithology and climate, REE compositions are modulated by grain size, weathering intensity, and mineralogical variance, which jointly regulate REE adsorption and redistribution processes in regolith-hosted systems. Our results provide mechanistic insights into REE differentiation and establish a geochemical framework for REE exploration in tropical and subtropical environments.