Trace and Rare Earth Element Geochemistry of Croatian Thermal Waters

Concentrations of 42 trace elements, including rare earths, in Croatian thermal waters were investigated. Originating from different parts of Croatia, i.e. different types of aquifers, studied thermal waters provide insight into the range of concentrations of broad spectrum of elements in Croatian thermal waters. Covering a wide range of temperature (30 - 92 °C), studied thermal waters are generally classified as geothermal springs (Hrvatsko Zagorje and Lipik) and low-temperature geothermal reservoirs (Bizovac), differing from each other not only by temperature but also by geochemical composition. Thermal waters from Bizovac Spa, from the eastern part of Croatia, were found significantly enriched in majority of measured elements in comparison with waters from Hrvatsko zagorje and Lipik. Significant variability between studied waters was also observed regarding the rare earth elements levels and fractionation patterns, substantially different normalized REE patterns and wide range of Eu and Ce anomalies, ranging from 0.10 to 0.84 and from 3.48 to 159, respectively. Characterized by near-neutral to alkaline pH (6.8 - 8.1) and great variability with respect to the geochemical composition, studied waters were found to primarily reflect the underlying geology.