Serpentinized ultramafic rocks of Evia Island (Greece) as potential reservoirs for CO2 mineralization based on a petrological research

In the island of Evia (Aegean, Greece), big peridotitic masses crop out in the central and north parts displaying different extents of serpentinization. These rocks were frequently subjected to CO2-metasomatism [1,2] forming magnesite deposits that have been exploited for several years for industrial purposes (currently by Grecian Magnesite and TERNA Mag companies). The non-carbonated ultramafic rock types mostly appear in the broader areas of Pagondas, Dafni, Psachna, Makrimalli, Artaki and Vatondas. These are predominantly divided into serpentinized harzburgites/lherzolites and serpentinites, whereas scarce occurrences of garnet-bearing serpentinites are rarely evident close to the Pagondas locality in spatial association with rodingites [3]. The mineralogy [mostly serpentine ± (clino- and ortho-) pyroxenes ± olivine ± garnet] and geochemistry (i.e. high MgO, FeO and occasionally CaO contents) of representative rock samples from the Pagondas and Psachna-Makrimalli regions indicate that they can react with carbonated water in order to crystallize carbonate mineral phases. This is also shown by thermodynamic calculations with PERPLE_X software [4], which simulate the natural carbonation of Central Evia ultramafic rocks, revealing that they have the physicochemical potential to form specific carbonate minerals (siderite, magnesite and calcite) at T ≤ ~390oC. Thus, it is concluded that in Central Evia the petrological properties and relatively high quantities of serpentinized peridotites, offer a potentially viable option for their exploitation as reservoir rocks during in-situ CO2-storage. These non-carbonated ultramafic outcrops are located proximal to: (a) the Western and Eastern coastline of Evia Island (i.e. ~6 km far from the Evoikos Gulf and ~20 km far from the Aegean Sea), (b) the Central Evia groundwaters [5],  (c) the Edipsos hot-springs in Northern Evia [6] and (d) areas with industrial activities close to the city of Chalkida. Hence, their geographical distribution could contribute to the financial viability of such storage scenarios lowering the logistic costs and contributing to sustainable development through actions for the mitigation of climate change. References: [1] Karkalis, C. 2022: PhD-Thesis National and Kapodistrian University of Athens, Department of Mineralogy and Petrology, 371p; [2] Grieco et al., 2023: Minerals, 13(2), 159; [3] Karkalis et al., 2022: Lithosphere, 2022 (1): 9507697; [4] Connolly, J.A.D., 2009: Geochem Geophys 10, Q10014; [5] Voutsis et al., 2015: J. Geochem. Explor., 159, 79-92; [6] Kanellopoulos et al., 2016:  Proc. 14th Intern. Congress Geol. Soc. Greece, Thessaloniki, May 2016, 50(2), 720-729