REE contents in solid sample media and stream water from different geological contexts: Comparison between Italy and Sweden

Rare earth elements (REEs) are quickly gaining more and more relevance as important chemical resources due to the large number of technical applications, and as a consequence, scientific interest on REE-bearing minerals is increasing. In this work, REE data from the FOREGS Geochemical Atlas of Europe database on solid sample media (topsoil, subsoil, stream sediment, and floodplain) and stream water for Italy and Sweden are used to plot distribution maps, and Principal Component Analysis to identify patterns within the data set. The careful investigation of the spatial distribution of REEs in all sample media for both countries allowed us to identify the prominent role played by the geogenic component. Despite a similar REE content of bedrocks (alkaline igneous products, both intrusive and effusive in Italy, alkali granites and pegmatites in Sweden), several distinct differences emerged between the two countries. We identified factors like climate, geomorphology, age of deposits, presence of mineralisation, types of soil and presence of till, as responsible for the different REE enrichments in solid and aqueous sample media in the two countries. Italian palaeosols, developed in volcanic areas, were identified as a possible future source for REE extraction using low pollutant extraction techniques.