Geochemical Characterisation of the Thermo-Mineral Waters of Greece

Environ Geochem Health https://doi.org/10.1007/s10653-021-01001-1 (0123456789().,-volV)( 0123456789().,-volV) ORIGINAL PAPER Geochemical characterisation of the thermo-mineral waters of Greece Lorenza Li Vigni . Kyriaki Daskalopoulou . Sergio Calabrese . Konstantinos Kyriakopoulos . Francesco Parello . Filippo Brugnone . Walter D’Alessandro Received: 24 August 2020 / Accepted: 3 June 2021 Ó The Author(s) 2021 Abstract Geothermal areas of Greece are located in thermal; (2) cold; (3) acidic (pH \ 5); and (4) regions affected by recent volcanism and in continen- hyperalkaline (pH [ 11). On statistical basis, thermal tal basins characterised by elevated heat flow. Many of waters were subdivided into subgroups according to them are found along the coast, and thus, water is often both their temperature [warm (\ 29 °C), hypothermal saline due to marine intrusion. In the current study, we (29–48 °C), thermal (48–75 °C) and hyperthermal present about 300 unpublished and literature data from ([ 75 °C)] and TDS [low salinity (\ 4 g/L), brackish thermal and cold mineral waters collected along (4–30 g/L) and saline ([ 30 g/L)]. Cold waters were Greece. Samples were analysed for major ions, Li, subdivided based on their pCO2 [low (\ 0.05 atm), SiO2 and isotopes in water. Measured temperatures medium (0.05–0.85 atm) and high ([ 0.85 atm)]. 18 range from 6.5 to 98 °C, pH from 1.96 to 11.98, while d O–H2O ranges from - 12.7 to ? 2.7% versus 2 Total Dissolved Solutes (TDS) from 0.22 to 51 g/L. SMOW, while d H–H2O from - 91 to ? 12% versus Waters were subdivided into four main groups: (1) SMOW being generally comprised between the Global Meteoric Water Line and the East Mediter- ranean Meteoric Water Line. Positive d18O shifts with Supplementary Information The online version contains respect to the former are mostly related to mixing with supplementary material available at https://doi.org/10.1007/ seawater, while only for a few samples these shifts s10653-021-01001-1. L. L. Vigni Á S. Calabrese Á F. Parello Á F. Brugnone K. Kyriakopoulos University of Palermo, DiSTeM, via Archirafi 36, Faculty of Geology and Geoenvironment, National and Palermo, Italy Kapodistrian University of Athens, Panestimioupolis, Ano Ilissia, Greece K. Daskalopoulou University of Potsdam, Institute of Geosciences, Karl- Liebknecht-Str. 24-25, Potsdam Golm, Germany K. Daskalopoulou GeoForschungs Zentrum, Physics of Earthquakes and Volcanoes, Helmholtzstraße 6/7, Potsdam, Germany S. Calabrese Á W. D’Alessandro (&) Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Di Palermo, via Ugo La Malfa 153, Palermo, Italy e-mail: [email protected] 123 Environ Geochem Health point to high-temperature water–rock interaction pro- Greece, located in a geodynamically active area of cesses. Only a few thermal waters gave reliable the Eastern Mediterranean, is characterised by wide- geothermometric estimates, suggesting reservoir tem- spread geothermal resources closely linked to the peratures between 80 and 260 °C. geology of the country (Papachristou et al., 2019). Its puzzling geodynamic regime contributes to the exis- Keywords Hydrogeochemistry Á Stable isotopes Á tence of an elevated terrestrial heat flow, which results Carbon dioxide Á Geothermometry in several geothermal fields containing both low and intermediate temperature fluids (Fytikas & Kolios, 1979). Areas of enhanced heat flow are located in regions affected by Miocene or Quaternary volcanism Introduction and in continental basins (Fytikas & Kolios, 1979). Geothermal exploration has found high-enthalpy In the 1960s, the National Tourism Organisation geothermal fields in Milos and Nisyros islands, in (NTO, 1966) estimated the number of thermo-mineral the South Active Aegean Volcanic Arc (SAAVA), and springs in Greece at more than 750, with nearly 200 of low-medium enthalpy georesources in some Aegean which found on the islands of the Aegean Sea. Even islands, i.e. Chios, Lesvos and Samothraki, and in though about a quarter of these springs is nowadays several sedimentary basins of Northern and Central used for balneotherapeutic purposes, archaeological Greece (Mendrinos et al., 2010). Besides, many of evidence supports the use of some of them since these fields are found along the coast as well as in prehistoric times (Fytikas et al., 1999). In classical islands, and thus, thermal waters are often brackish to times until the end of the Roman Empire, thermo- saline due to marine intrusion into the costal aquifer mineral waters were highly appreciated and many of (Lambrakis & Kallergis, 2005). In fact, according to them were mentioned by poets (Homer, Pindar, Minissale et al. (1997), the thermal springs located in Aristophanes), historians (Herodotus, Diodorus Sicu- the SAAVA are affected by mixing between the local lus, Plutarch) and geographers (Strabo, Pausanias) meteoric waters and the Aegean seawater, while a (Fytikas et al., 1999). At the same time, the first marine component, sometimes evolved due to pro- theories regarding their origin were developed (Plato, cesses seated in the deep thermal reservoirs, is found Aristotle) and their medical use was emphasised also in hot waters emerging along the coast of the (Hippocrates). It is worth mentioning that, during this continental basins (Duriez et al., 2008). period, many thermo-mineral springs were considered The complex geodynamic and geological setting of sacred and were dedicated either to the Nymphs or to the Aegean territory reflects in a great variety of Asclepius, the God of Medicine. Their religious geochemical compositions for many thermal and cold significance continued until Christian times. Then, fluid manifestations (Daskalopoulou et al., this dedication shifted either to Virgin Mary or to 2018a, 2019a; Minissale et al., 1989, 1997). The first Agioi Anargyroi, with the latter being saints known for scientific investigations regarding the chemical com- offering their medical services without reward position of the thermo-mineral waters of Greece (Ha˚land, 2009). Their balneotherapeutic use declined appeared soon after the birth of the Modern Greek under the Byzantine Empire and grew again under the State in 1830. Landerer (1843) gave the first overview Ottoman Empire, but it was not before the end of the of the whole territory and further nationwide studies twentieth century that other uses (heat and energy appeared in more recent times (Athanasoulis et al., production, industrial use of CO2, etc.) were applied 2009; Lambrakis & Kallergis, 2005; Lambrakis et al., (Fytikas, 1988). In fact, Fytikas et al. (2005) docu- 2014; Pertessis, 1937). mented that in the early 70’s the Institute of Mineral The scope of this study is to present a large dataset and Geological Exploration (IGME) used for the first on the chemical and isotopic composition of the time the thermal water for greenhouse heating. thermo-mineral waters of the whole Greek country However, the great development in geothermal field and discuss their properties in the framework of the arrived in 1981 when Greece entered the European geological context of the area. To this aim, we Union, and many research projects were funded by the discussed the results of 285 water samples collected European Commission. from October 2004 to March 2020 (Fig. 1) and 123 Environ Geochem Health analysed for their major, minor and trace constituents oriented crustal extension (Mercier, 1981); and (3) the and the isotopic composition of water. About one third westward motion of Anatolian plate along the strike- of the results were previously published (D’Alessan- slip North Anatolian Fault (NAF) (Pavlides & Caputo, dro et al., 2008, 2014, 2017, 2018, Li Vigni et al., 2004). It is worth noting that the Greek region is the 2021; Papachristou et al., 2014) and are here discussed result of the intense collision of several microplates together with the unpublished data to present a more or (Aegean, Anatolian and Apulian plate) that took place less complete picture of the whole country. Although during the Alpine orogenesis since the Upper Creta- spanning over a long time period, the same sampling ceous involving the subduction of Tethyan Ocean (van and analytical methods were applied increasing the Hinsbergen et al., 2005). The volcanism of the area is internal consistency of the dataset. located in the southern Aegean Sea, while the SAAVA comprises magma of calc-alkaline to shoshonitic suite and signs of crustal contamination (Pe-Piper & Piper, Study area 2006). Based on the aforementioned complex tectonic The complex geodynamic setting of the Hellenic setting and the prevailing geological formations, territory classifies it in the most tectonically and Mountrakis (1985, 2010) divided Greece into struc- seismically active areas of the world (e.g. Le Pichon tural isopic zones, which from west to the east are: et al., 2001; Taymaz et al., 1991; Tsokas & Hansen, (1) External Hellenides (EH): correspond to a 1997). This regime is dominated by three large-scale neritic continental sea depositional environment tectonic structures: (1) the active retreat of the and consist of the Parnassos, Gavrovo-Tripolis, northward subduction of African plate beneath the Ionian and Paxos zones. It is worth mentioning Eurasian at a rate of 4–6 mm/a (McClusky et al., 2000) that during the Middle-Upper Jurassic, the forming the back-arc Aegean area; (2) the mostly N–S Fig. 1 Geographic distribution of the sampling sites. Insets are enlarged areas with high density of sampling sites. 1—Samothraki; 2— Strimon Basin; 3—Migdonia Basin; 4—Othrys and Sperchios

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