A previously-defined previous termflownext term system is used to investigate REE previous termbehaviornext term at different stages along previous termgroundwater flownext term paths in previous termfracturednext term basalt and sedimentary previous termaquifers.next term Results from this study indicate that REE concentrations and patterns predominantly reflect different types and rates of reactions taking place to those controlling major ion chemistry. In areas where recharge is through sediments, REE concentrations are high (Nd: 8.62–31.61 ng/L), and localised processes, such as source heterogeneity, control REE patterns and concentrations. Increased concentrations of REEs in these previous termgroundwaters,next term where pH < 6.1, is a result of early-stage REE mobilisation in the previous termflownext term system. In contrast, where previous termgroundwaternext term recharges through basalt REE concentrations are low (Nd: 2.40–4.75 ng/L), and REE concentrations are relatively constant along previous termgroundwater flownext term paths, indicating steady state conditions. previous termGroundwaternext term from both the sediment and basalt previous termaquifernext term systems previous termflowsnext term into the local discharge area. In contrast to TDS contents and major ion ratios, previous termgroundwaternext term from the discharge area has REE concentrations (Nd: 1.84–4.18 ng/L) and patterns that reflect a larger component of previous termflownext term from the basalt previous termaquifer.next term Lower REE concentrations of previous termgroundwaternext term from the regional sedimentary previous termaquifernext term may result from progressive REE sorption or co-precipitation, as indicated by an increase in (Y/Ho)Cl–CN ratios and HREE-enrichment for previous termgroundwaternext term with pH∼7.1 due to greater abundances of HREE vs. LREE dicarbonato complexes.