In Albania, the presence of high mountain chains and active fault systems favors the ascent of deep waters producing several thermo-mineral springs. The most important springs are located in the Kruja Province and rise from deep karst aquifers. The Kruja tectonic zone (central Albania) consists of elongated anticline structures of Cretaceous–Eocene limestones and dolomites covered by Oligocene flysch deposits. It is affected by longitudinal NW-SE faults intersected by some transversal faults. The carbonate rocks have been buried up to ca. 10 km depth, and are underlain by Triassic-Permian evaporites. In the Kruja Zone, the geothermal gradient ranges from 7 to 11 mK/m. Five deep wells are present in the area (depth range 2000-3000 m) tapping thermal waters of carbonate aquifer. Three of these wells, namely Ishmi-1b, Kozan-8 and Galigat-2, are the most important as concerns water quality, temperature and curative values. Thermal waters in the central area of the Kruja province are of the Cl–SO –Na–Ca type, with temperatures up to 56 °C for springs and 65 °C for wells, and high H S concentrations (Eftimi & Frashëri, 2016). Recent scientific activities carried out at the Kruja Province focused on Kozan-8 well (1837 m depth) at Elbasan locality, including water and deposited minerals sampling. Thermal waters discharge exhibits EC = 6400 microS/cm, temperature of 55.4 °C, pH = 6.73, and reducing Eh. Water composition shows similar high Na and Ca contents among cations, and high Cl and SO4 among anions. According to previous studies (Eftimi, 1998; Reimann & Birke, 2010), this water composition can be related to the presence of deep fluids with long/deep circulation in the local anticline structures, involving Mesozoic carbonates (which contain also pyrite) and the underlying Triassic evaporites. Together with H S (Eftimi & Frashëri, 2016), enrichment in CO2, CH4 and He has been also detected. At the emergence, the water results oversaturated with respect to Ca-Mg carbonates, and slightly undersaturated with respect to sulphates. Around the water discharge abundant mineral deposits are present, consisting of banded encrustations of different colours (white, grey, black, pale yellow, orangeyellow) formed from the outgoing hot fluids. Such mineralization was never analysed before. Combined optical microscopy and X-ray powder diffraction analyses evidenced that the studied encrustations mainly consist of micrometric-sized crystals of Ca- and Mg-sulphates (gypsum, CaSO4·2H2O; bassanite, CaSO4·0.5H2O; anhydrite, CaSO4; epsomite, MgSO4·7H2O), calcium carbonates (aragonite and calcite CaCO3), and sulphur (S8). Furthermore, Na-, K-, and Fe-sulphates (metavoltine, K2Na6Fe2+Fe6 3+O2(SO4)12·18H2O; sideronatrite, Na2Fe3+(SO4)2(OH)·3H2O) were sporadically found. Eftimi R. (1998) - Some data about the hydrochemistry of Kruja–Dajt mountain chain (in Albanian). Studime Gjeografike, 11, 60-69. Eftimi R. & Frashëri A. (2016) - Thermal Waters of Albania. In: Papic, P. (ed), Mineral and Thermal Waters of Southeastern Europe, Environmental Earth Sciences Series, Springer International Publishing Switzerland, 115-130, https://doi.org/10.1007/978-3-319-25379-4_7. Reimann C. & Birke M. (2010) - Geochemistry of European bottled water. Borntraeger Science Publishers, Stuttgart. ISBN:978-3-4430-1067-6. Silo V., Nishani P. & Silo E. (2010) - Hydrocarbon exploration under Kruja zone in Tirana-Rodon area, Albania. Journal of the Balkan Geophysical Society, 13(1), 9-16.
Mineralization of the Kozan-8 thermal well (Kruja Province, central Albania): a mineralogical and water geochemical study
Fregola R. A.
;Liso I. S.;Parise M.;Lacalamita M.;
2024-01-01
Abstract
In Albania, the presence of high mountain chains and active fault systems favors the ascent of deep waters producing several thermo-mineral springs. The most important springs are located in the Kruja Province and rise from deep karst aquifers. The Kruja tectonic zone (central Albania) consists of elongated anticline structures of Cretaceous–Eocene limestones and dolomites covered by Oligocene flysch deposits. It is affected by longitudinal NW-SE faults intersected by some transversal faults. The carbonate rocks have been buried up to ca. 10 km depth, and are underlain by Triassic-Permian evaporites. In the Kruja Zone, the geothermal gradient ranges from 7 to 11 mK/m. Five deep wells are present in the area (depth range 2000-3000 m) tapping thermal waters of carbonate aquifer. Three of these wells, namely Ishmi-1b, Kozan-8 and Galigat-2, are the most important as concerns water quality, temperature and curative values. Thermal waters in the central area of the Kruja province are of the Cl–SO –Na–Ca type, with temperatures up to 56 °C for springs and 65 °C for wells, and high H S concentrations (Eftimi & Frashëri, 2016). Recent scientific activities carried out at the Kruja Province focused on Kozan-8 well (1837 m depth) at Elbasan locality, including water and deposited minerals sampling. Thermal waters discharge exhibits EC = 6400 microS/cm, temperature of 55.4 °C, pH = 6.73, and reducing Eh. Water composition shows similar high Na and Ca contents among cations, and high Cl and SO4 among anions. According to previous studies (Eftimi, 1998; Reimann & Birke, 2010), this water composition can be related to the presence of deep fluids with long/deep circulation in the local anticline structures, involving Mesozoic carbonates (which contain also pyrite) and the underlying Triassic evaporites. Together with H S (Eftimi & Frashëri, 2016), enrichment in CO2, CH4 and He has been also detected. At the emergence, the water results oversaturated with respect to Ca-Mg carbonates, and slightly undersaturated with respect to sulphates. Around the water discharge abundant mineral deposits are present, consisting of banded encrustations of different colours (white, grey, black, pale yellow, orangeyellow) formed from the outgoing hot fluids. Such mineralization was never analysed before. Combined optical microscopy and X-ray powder diffraction analyses evidenced that the studied encrustations mainly consist of micrometric-sized crystals of Ca- and Mg-sulphates (gypsum, CaSO4·2H2O; bassanite, CaSO4·0.5H2O; anhydrite, CaSO4; epsomite, MgSO4·7H2O), calcium carbonates (aragonite and calcite CaCO3), and sulphur (S8). Furthermore, Na-, K-, and Fe-sulphates (metavoltine, K2Na6Fe2+Fe6 3+O2(SO4)12·18H2O; sideronatrite, Na2Fe3+(SO4)2(OH)·3H2O) were sporadically found. Eftimi R. (1998) - Some data about the hydrochemistry of Kruja–Dajt mountain chain (in Albanian). Studime Gjeografike, 11, 60-69. Eftimi R. & Frashëri A. (2016) - Thermal Waters of Albania. In: Papic, P. (ed), Mineral and Thermal Waters of Southeastern Europe, Environmental Earth Sciences Series, Springer International Publishing Switzerland, 115-130, https://doi.org/10.1007/978-3-319-25379-4_7. Reimann C. & Birke M. (2010) - Geochemistry of European bottled water. Borntraeger Science Publishers, Stuttgart. ISBN:978-3-4430-1067-6. Silo V., Nishani P. & Silo E. (2010) - Hydrocarbon exploration under Kruja zone in Tirana-Rodon area, Albania. Journal of the Balkan Geophysical Society, 13(1), 9-16.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
