Discovery of hyperalkaline waters in the ophiolites of western Serbia: Environmental considerations for carbon capture and sequestration

Recently on-land ophiolites as unconventional reservoirs and hyperalkaline groundwaters have come out as a viable solution for natural atmospheric CO2 uptake/storage. However, the possibility of employing ophiolites and rare hyperalkaline waters as means or repositories of anthropogenic CO2 has not been studied and no case study for Serbia has been introduced so far. Extremely rare on a global scale, but quite frequent are hyperalkaline groundwaters from western Serbia that emanate from the wide supra-crustal Jurassic on-land ophiolites. Once discharged at Earth's surface, such groundwaters react with natural CO2 and produce carbonates. As such, the ophiolites and associated hyperalkaline groundwaters represent an important environmental factor of Serbia, allowing highly perspective development of the carbon capture and sequestration facilities across the area. The surface-exposed, ca. 20-30 km wide, mainly Jurassic massifs of ophiolite-bearing crustal units of western Serbia, occur as two belts: Inner Dinaride Ophiolite belt and Vardar Zone. The composite geologic and hydrogeological field study shows that these unconventional reservoirs have several natural hyperalkaline springs (pH > 10.5), with the possibility of promoting fracturing and in-situ mineralization. By promoting the presence of very rare hyperalkaline groundwaters across western Serbia, this study attempts (i) to quantify the natural volume of hyperalkaline groundwaters (basic regional hydrogeology), emphasizing (ii) a preliminary natural degassing/carbon capture potential.