No abstract

This study investigates the capability of the Southeast Mesohellenic Trough (SE MHT) sandstone formations to serve as a potential reservoir for CO2 storage in response to the emerging climate change issues by promoting environmentally friendly mineral sequestration applications. Sandstone samples, for the first time, were evaluated for their petrographic characteristics, mineral chemistry, geochemical properties, as well as their petrophysical and gas adsorption properties through tests. The sandstones were tested and classified into distinct groups. The most promising site to be considered for pilot CO2 storage testing is the Pentalofos Formation locality since its sandstones display specific mineral phases with the proper modal composition to conceivably react with injected CO2, leading to the development of newly formed and stable secondary mineral phases. The gas adsorption results are also more encouraging for sandstones from this sedimentary formation. All the measured UCS (uniaxial compressive strength), Ei (bending stiffness), and ν (Poisson’s ratio) results are above those dictated by international standards to perform CO2 storage practices safely. Furthermore, the specified targeted locality from the Pentalofos Formation holds the geological advantage of being overlaid by an impermeable cap-rock formation, making it suitable for deploying CO2 mineralization practices. The demarcated area could permanently store a calculated amount of ~50 × 105 tons of CO2 within the geological reservoir by reacting with the specified mineral phases, as specified through the proposed petrographic PrP index (potential reactive phases).

No abstract

This study focuses on the use of petrology as a useful tool in construction applications (i.e., concrete). More specifically, this study investigates how the petrogenetic characteristics of ultramafic rocks derived from ophiolite complexes (Veria–Naousa, Gerania) can act as a key tool for the prediction of the final behaviour of ultramafic aggregates as concrete aggregates. For this reason, their petrographic, chemical and mineralogical characteristics were examined and correlated with their engineering properties for evaluating their suitability as concrete aggregates. This study had come up, for the first time, that the genesis environment of the ultramafic rocks is the determinant factor for their physico-mechanical characteristics. Their suitability is relevant to the impact of their mineralogical and structural characteristics both from the two different ophiolite complexes (Veria–Naousa and Gerania). Except serpentinization, the basic alteration process-index of ultramafic rocks, there are also other chemical indices which can be used for ultramafic rocks that may determine their properties. In this context the term ‘fertility rate’ (FR) was introduced which may characterize ultramafic rocks as fertile or not. Furthermore, the Ultramafic Rock Health Index (U.R.H.I.) as well as the Normalized U.R.H.I. (U.R.H.I.N) was also introduced and correlated with the engineering properties of the investigated aggregate rocks. The last index aims to assess and quantify the overall health conditions, encompassing the two major modifying factors that include removal of primary mineral phases, as well as the extent of serpentinization. The main conclusion of this paper is that the genesis environment of the ultramafic rocks is the critical factor that determines their mineralogical, petrographic and chemical characteristics which consequently determines the basic engineering properties of rocks that determine their suitability or not as concrete aggregates.

Listwaenitization processes have significantly altered the mantle section of the West Chalkidiki ophiolites, generating the second largest magnesite deposit in Greece. Although research studies have been conducted in the region, the post-magmatic processes, and especially the geotectonic settings under which listwaenitization took place, remain unclear. In this study, minerals and rocks were studied applying XRD, clay fraction, SEM, EMPA, ICP-MS, INAA, LA-ICP-MS, and thermodynamic modeling. The results revealed that alteration processes significantly affected the mantle wedge peridotite protoliths leading to the following chemical changes (a) SiO2 increase with decreasing MgO, (b) Cs, Pb, As, and V enrichments, (c) limited alteration of magnesiochromite hosted within listwaenitized chromitites and (d) enrichment in PPGE and Au in listwaenitized chromitites and desulfurized laurite. Alteration was induced by fluids deriving from subducted Mesozoic sediments, represented by the Prinochori Formation or chemically similar formations. The final product of completely silicified peridotite (silica listwaenite) is thermodynamically stable in Earth-surface conditions, with dolomite and phyllosilicates transforming into clay minerals. Based on detailed petrographical observations, peridotites were subjected to serpentinization, and subsequently, serpentine interacted with CO2, silica and calcium-bearing fluids, leading to its transformation into amorphous rusty-silica mass and/or tremolite.