Distribution of rare earth elements in crystalline bedrock groundwaters: Oslo and Bergen regions, Norway

One hundred and fifty Norwegian bedrock groundwater samples, from Bergen and from Vestfold (Oslofjord), have been analysed by ICP-MS techniques at two laboratories for a large suite of trace elements including rare earth elements (REEs) and Y. The bedrock lithologies include granites (dominated by the Permian Drammen Granite) and Permian latites/rhomb porphyries from Oslofjord, and Caledonian/Precambrian granitic and gneissic lithologies in the Bergen area. The REEs show good correlation with each other, with the exception of Eu. REEs generally show a weak negative correlation with pH. REE concentrations are highest in waters in acidic lithologies and generally decrease with increasing atomic weight. Yttrium, La, Ce and Nd are the most abundant REEs in the waters, with median concentrations exceeding 0.1 μg/l. On crustal (PAAS)-normalised plots, distinct geochemical signatures are observed for the different lithologies. Most groundwaters exhibit negative Eu anomalies on such plots, except for latitic waters from the Oslo area which show a positive Eu anomaly. Aquifer host-rock-normalised plots for groundwaters from Vestfold indicate minor enrichment in heavier REEs and depletion in Ce during water–rock interaction.