Abstract
Geothermal areas of Greece are located in regions affected by recent volcanism and in continental basins characterised by elevated heat flow. Many of them are found along the coast, and thus, water is often saline due to marine intrusion. In the current study, we present about 300 unpublished and literature data from thermal and cold mineral waters collected along Greece. Samples were analysed for major ions, Li, SiO2 and isotopes in water. Measured temperatures range from 6.5 to 98 °C, pH from 1.96 to 11.98, while Total Dissolved Solutes (TDS) from 0.22 to 51 g/L. Waters were subdivided into four main groups: (1) thermal; (2) cold; (3) acidic (pH < 5); and (4) hyperalkaline (pH > 11). On statistical basis, thermal waters were subdivided into subgroups according to both their temperature [warm (< 29 °C), hypothermal (29–48 °C), thermal (48–75 °C) and hyperthermal (> 75 °C)] and TDS [low salinity (< 4 g/L), brackish (4–30 g/L) and saline (> 30 g/L)]. Cold waters were subdivided based on their pCO2 [low (< 0.05 atm), medium (0.05–0.85 atm) and high (> 0.85 atm)]. δ18O–H2O ranges from − 12.7 to + 2.7‰ versus SMOW, while δ2H–H2O from − 91 to + 12‰ versus SMOW being generally comprised between the Global Meteoric Water Line and the East Mediterranean Meteoric Water Line. Positive δ18O shifts with respect to the former are mostly related to mixing with seawater, while only for a few samples these shifts point to high-temperature water–rock interaction processes. Only a few thermal waters gave reliable geothermometric estimates, suggesting reservoir temperatures between 80 and 260 °C.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10653-021-01001-1.
Highlights
In the 1960s, the National Tourism Organisation (NTO, 1966) estimated the number of thermo-mineral springs in Greece at more than 750, with nearly 200 of which found on the islands of the Aegean Sea
The scope of this study is to present a large dataset on the chemical and isotopic composition of the thermo-mineral waters of the whole Greek country and discuss their properties in the framework of the geological context of the area
Based on the aforementioned parameters, the sampled waters were divided into cold (\ 23 °C) and thermal ([ 23 °C) waters, with the former being subdivided according to their pCO2 values and the latter according to their combined temperature values and Total Dissolved Solutes (TDS) concentrations
Summary
In the 1960s, the National Tourism Organisation (NTO, 1966) estimated the number of thermo-mineral springs in Greece at more than 750, with nearly 200 of which found on the islands of the Aegean Sea. It is worth mentioning that, during this period, many thermo-mineral springs were considered sacred and were dedicated either to the Nymphs or to Asclepius, the God of Medicine Their religious significance continued until Christian times. This dedication shifted either to Virgin Mary or to Agioi Anargyroi, with the latter being saints known for offering their medical services without reward (Haland, 2009). Their balneotherapeutic use declined under the Byzantine Empire and grew again under the Ottoman Empire, but it was not before the end of the twentieth century that other uses (heat and energy production, industrial use of CO2, etc.) were applied (Fytikas, 1988).
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