Geochemistry of Rare Earth Elements in the Rivers and Groundwaters of Chistovodnoe Thermal Area (Primorye, Far East of Russia)

Abstract

The behaviour and hydrogeochemistry of rare earth elements were investigated in the surface and groundwaters of Chistovodnoe thermal area (Far East of Russia). The waters were classified according to the pH into neutral waters with pH ranging from 6.6 to 7.3 and alkaline waters with pH between 7.5 and 9.3. The REE concentrations in the river waters with pH=6.6-6.8 are markedly higher than those from the thermal groundwaters with pH=7.9-9.3. The surface water mass in the Chistovodnoe area has similar REE patterns reflected in negative Ce and Eu anomalies. The cold and thermal groundwaters are influenced by the water-rock interaction processes. Such correlations are explained by the redox changes with depth within the area. The oxidizing conditions in the shallower aquifer generate a larger Ce anomaly. The low concentrations of REE in groundwater suggest that the elements are relatively immobile during weathering and transport, being carried partly in heavy detrital minerals, especially zircon and titanite, and partly adsorbed onto clay particles. Heavy REE enrichment is explained by successive water-rock interactions supplying REE to the water in which differential scavenging of light REE by particulate matters occurs.