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High-grade granitoid gneisses (740–710 Ma) and elongate bodies of amphibolite and hornblende schist with cm-scale layers of garnet pyroxenite form an overturned fold in the Gabal Um Gunud area, South Eastern Desert of Egypt. Whole-rock geochemical data combined with zircon U-Pb-Hf isotope data suggest that the metabasites represent relics of oceanic crust with an N-MORB affinity, which has been derived from partial melting (2.0–1.4 GPa; ~65- ~ 45 km depth) of a depleted mantle source beneath an intra-oceanic, spreading forearc basin. Such increment of melting degree resulted in small basaltic melt batches with transitional tholeiitic to boninitic affinities. Progressive slab subduction and partial melting of the tholeiitic amphibolite produced high-Al and low HREE melts for trondhjemite at av. T = 854°C and low-Al and high HREE melts for tonalite at higher temperatures (av. 949°C). The low Mg# of the trondhjemite-tonalite rocks may be attributed to limited contamination of subduction components, as evidenced by the weak lanthanide tetrad effects (TE1,3~1) and near-chondritic Zr/Hf, Nb/Ta, and Y/Ho ratios, while the garnet pyroxenite was the residuum produced in equilibrium with the trondhjemite-tonalite melts. [ABSTRACT FROM AUTHOR]

Research attempts on biomass use constitute a response to the growing demand for sustainable and low-cost energy from renewable sources. Hence, the sustainable use of Posidonia oceanica (PO) waste as a material for biomass to produce green energy is being considered in many countries in the Mediterranean region. PO meadows are considered as the main type of sea flora in the Greek coasts. PO can extract biomass from nearby ecosystems of the coastal zone, either directly through the transportation of disposed non-living leaves or indirectly via benthic organisms. The aim of this study is to investigate the use of PO waste derived from Kefalonia Island (Greece) as a biomass source. PO samples were collected around the island, and they were mineralogically and microstructurally analyzed. In addition, physicochemical, chemical, and thermogenic tests were performed in order to obtain the optimum and most completed characterization of the material. Based on the results, cellulose seems to be the main structural component of PO, which also seems to determine their behavior. PO presents microscopic similarities to other lignocellulosic materials which composition is made of carbonates, lignin, extractives, and minerals. Ash and moisture content constitute the two critical parameters that are responsible for the energy differences of each biomass. The outcome of this study shows the potential use of PO wastes as an interesting source for energy production. [ABSTRACT FROM AUTHOR]

Anorogenic magmatism in the northern Arabian-Nubian Shield occurred during a long-lasting crustal extension event (<580 Ma), which succeeded the formation of the Pan-African orogenic belt in NE Africa and Arabia. Late Neoproterozoic anorogenic felsic volcanic-subvolcanic rocks, along with post-collisional granitoid suites, are exposed in the Gabal Abu Durba mountain range along the eastern flank of the Gulf of Suez in Sinai. These rocks include granite and rhyolite porphyries, metaluminous to weakly peralkaline with distinct potassic alkaline and ferroan affinities. Major and trace element characteristics such as K2O/MgO >16, total alkalis >8.5 wt.%, (K2O + Na2O)/CaO >10, agpaitic index (NK/A) >0.85 and Zr (>250 ppm), Nb (>20 ppm), Y (>80 ppm), Zn (>100 ppm) and Ce (>100 ppm), and 10,000 × Ga/Al >2.6 and [Zr + Nb + Y + Ce] >350 ppm are suggestive of an A-type granite genesis. Zircon U-Pb dating of two representative samples returned crystallization ages of 569 ± 2.6 Ma and 561.7 ± 3.2 Ma for granite and rhyolite porphyries, respectively. The melting temperatures estimated at 997–1020°C are consistent with high-temperature liquidus conditions. Fractional crystallization, coupled with less significant crustal assimilation, was likely the main mechanism of formation of these rocks from a common primitive asthenospheric mantle-derived trachytic magma in an anorogenic intra-plate setting. The A-type alkali granite and rhyolite porphyries of Gabal Abu Durba are manifestations of mantle upwelling and lower crust underplating in the late Ediacaran anorogenic stage. These felsic subvolcanic intrusions (≈ 569–562 Ma) along with their volcanic counterparts constitute a new unmatched rock unit that most probably represent the last chapter of the anorogenic magmatism in the Neoproterozoic Arabian-Nubian Shield crust before the beginning of Phanerozoic era. [ABSTRACT FROM AUTHOR]

This article presents, for the first time, the study of diabases from various ophiolite complexes from Greece and Cyprus to identify their performance as concrete aggregates. Within this scope, in the first step, diabase samples from four selected ophiolite complexes of Greece (Veria-Naousa, Edessa and Guevgueli) and Cyprus (Troodos) were collected in order to estimate their suitability as concrete aggregates by means of their petrographic and physicochemical characteristics. In the next step, concrete specimens were prepared and their mechanical strength was measured in order to investigate their mechanical performance. Additionally, their petrographic characteristics in relation to the mechanical strength of the created concretes were investigated for the first time. Concrete specimens prepared by employing diabases from the Veria-Naousa and Guevgueli complexes as aggregates were reckoned as the most durable ones in contrast to those derived from the Edesssa complex and even more so than those from Cyprus, with the latter containing the most altered diabases (rodingitised). The overall conclusion of this research is that the engineering properties of the aggregates were dependent on their petrographic characteristics and hence they influenced the final mechanical behaviour of each produced concrete. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) has reached a higher level of emissions in the last decades, and as it is widely known, CO2 is responsible for numerous environmental problems, such as climate change. Thus, there is a great need for the application of CO2 capture and storage, as well as of CO2 utilization technologies (CCUS). This review article focuses on summarizing the current CCUS state-of-the-art methods used in Europe. Special emphasis has been given to mineralization methods/technologies, especially in basalts and sandstones, which are considered to be suitable for CO2 mineralization. Furthermore, a questionnaire survey was also carried out in order to investigate how informed about CO2 issues European citizens are, as well as whether their background is relative to their positive or negative opinion about the establishment of CCUS technologies in their countries. In addition, social acceptance by the community requires contact with citizens and stakeholders, as well as ensuring mutual trust through open communication and the opportunity to participate as early as possible in the development of actions and projects related to CO2 capture and storage, at all appropriate levels of government internationally, as citizens need to understand the benefits from such new technologies, from the local to the international level. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the Aegean region (Cyclades – Greece), a large part of the Island of Anafi consists of exhumed high-grade metamorphic sequences (amphibolites, serpentinites and metasediments) that have been intruded by Late Cretaceous intermediate and felsic granitoids. These correspond to I-type arc-related rocks, displaying calc-alkaline geochemical affinities. Variability in their petrographic features, mineral composition and geochemistry is assigned to differentiation processes that mostly involved plagioclase and/or K-feldspar, and to a lesser extent amphibole and biotite. Mineral chemistry and geochemical results suggest that the Anafi granitoids are highly comparable with the Late Cretaceous granitoid intrusive rocks from East Crete and Donousa island. The amphibole and zircon saturation thermometry yields relatively moderate temperature crystallization conditions (~790°C) for the intermediate granitoids and lower for the felsic granitoids (~630°C). Geobarometric calculations based upon the chemistry of magnesiohornblende, as well as the normative (Qz), (Ab) and (Or) contents clearly point to shallow intrusion conditions (~2.0–6.5 kbar), corresponding to an estimated depth of crystallization of ~12 ± 4 km. The thrust sheets that overly the Palaeogene flysch in Anafi (metasediments with serpentinized peridotites, amphibolites and metabasites), constitute a subducted and metamorphosed oceanic sequence. These metamorphic units likely represent a part of the Pindos – Cycladic Blueschist Unit domain that was subducted at an earlier pre-Campanian stage. In the hydrated mantle wedge, incorporation of shallow level granitoids within metamorphic units was likely facilitated via corner flow intrusion mechanisms. Following the intrusion, the granitoid rocks were exhumed in a syn-convergent setting, along with the metamorphic thrust sheets, by continuous underplating of more external units, thus, escaping penetrative ductile deformation. [ABSTRACT FROM AUTHOR]

The scope of this study focuses on the use of two different types of industrial byproducts such as slags (FeNi and Electric Arc Furnace slag) combined with natural sand as concrete aggregates as well as the evaluation of their suitability on the final physicomechanical behavior of the produced concrete specimens. For this reason, twelve concrete specimens were prepared using variable concentrations of these slags which were compared to concrete specimens made by natural rocks as aggregates (limestones). The mineralogical, petrographic, chemical and morphological characteristics of these raw materials were related to the physicomechanical characteristics of the produced concrete specimens. Those concrete specimens containing aggregates of higher amount of Electric Arc Furnace slags seems to present better mechanical strength both in 7 and in 28 days of curing regarding the other mixtures and regarding the specimens made by natural rocks as aggregates (limestones). This is due to the mineralogical, textural and morphological characteristics of the tested slags, which lead to a better bonding between them and the cement paste making them at the same time a promising alternative in the production of green concrete for construction applications. The compact texture of slags is responsible for the stronger bonding with the aggregates in relation to the unevenly distributed porosity of the natural aggregates. Wüstite presents negative effect on the final mechanical strength of concrete specimens which is documented both by the microscope images and by the three-dimensional study of the produced concretes. [ABSTRACT FROM AUTHOR]

The rock pinnacles of the Meteora UNESCO World Heritage Site, Central Greece, are global geologic icons but are inadequately studied. Herein, we summarize decades of observations leading to a geohistory and geoenvironmental model of the unique conditions that were essential for their creation. Via this synthesis, we hope thus to encourage further specialized studies of the West Thessaly-Meteora region and to promote the value of updating geological research within World Heritage Sites. The Meteora rock spires owe their existence to ten critical geologic episodes spread over a period of nearly a billion years. Early Miocene sedimentary deposits that make up the rock spires are derived largely from the metamorphic core complex of the exhumed Pelagonian (~ Precambrian to Permian) continental complex and include fragments of “blueschist” derived from the Miocene exhumation of Mount Olympos (subducted Triassic-Eocene carbonate banks). The Miocene sediments are deposited as turbidite formations overlain by “Gilbert-style” deltaic conglomerates. The cobble-turbidite formations comprise submarine canyon fills. The rock spires themselves result from initiation of Pleistocene erosion into a peneplain estimated, very roughly, to ~ 700,000 years in age. This geoenvironment is similar to today’s active sedimentation ongoing off the Malibu coast of California in that the deposits include “Gilbert-style” deltas and turbidites originating from an exhuming metamorphic complex, simultaneously eroding and depositing within off-shore canyons. This comparative model requires a reinterpretation of the “consensus” interpretation of the Miocene oceanic margin south of the Meteora region to one hosting more active energetic deposition and a deeper basin. [ABSTRACT FROM AUTHOR]

Featured Application: Τhe smelting process can be applied for the direct recycling of the nickel ferrous dust collected in the gas cleaning systems of the rotary kilns (R/Ks) during the pre-reduction of laterite ore in the course of ferronickel production by the pyrometallurgical route. The method can also be applied for smelting of ore fines. Contained Ni is recovered in the liquid metal resulting in the production of high purity low Ni-alloyed steel grades following secondary metallurgical treatment. The composition of the produced slags by this method can be efficiently adjusted so that the slags could be used in the manufacturing of special slag type composite cements substituting clinker. Present findings indicate that there is also potentially space for improvement in conventional EAF steel slags composition to allow for their wider use in building sector. In general, the developed zero residues recycling process concept can be applied for the recycling of metallurgical wastes/byproducts (dusts, fines etc.) by "one-stage" reduction smelting in DC-arc furnaces without any pretreatment (agglomeration, briquetting, sintering) recovering the contained valuable metals in the liquid bath, while producing slags suitable for further utilization in the manufacturing of high added value environmental friendly building materials (cements) accountable for less CO2 footprint; relative to the amount of clinker being substituted. A pyrometallurgical process was developed for the recycling of Ni bearing dusts and laterite ore fines by direct reduction smelting in DC (direct current) arc furnace. In the course of the performed industrial trials, besides the Ni-recovery in the liquid bath, slag composition was deliberately adjusted in order to produce a series of metallurgical slags with different chemical and mineralogical composition. The aim of this study was to investigate their suitability as clinker substitute in cement manufacturing. Examined parameters were slag FeOx content, basicity and applied cooling media (air, water cooling). A series of composite Portland and slag cements were manufactured in laboratory scale incorporating 20% and 40% of each slag, respectively; the rest being clinker of OPC (ordinary Portland cement) and 5% gypsum. The extended mineralogical analysis and microstructural properties of the produced slags were examined and correlated with the properties of the produced cements. The physical and mechanical characteristics of all examined cement products were found to meet the requirements of the regulation set for cements. The present research revealed that the most critical parameter in the compressive strength development of the slag cements is the mineralogical composition of the slag. Even in cases where rapid cooling to obtain glassy matrix is not feasible, adjustment of slag analysis to obtain mineralogical phases similar to those met in clinker of OPC, even at higher FeO contents (up to ~21wt.%), can result in production of slag with considerable latent hydraulic properties. These results indicate that there is potentially space for adjustments in conventional EAF (electric arc furnace) steel slags composition to allow for their wider use in cement manufacturing with significant environmental and economic benefits resulting from the reduction of energy requirements, CO2 emissions and natural raw materials consumption. [ABSTRACT FROM AUTHOR]

This Special Issue presents sixteen scientific papers that explore the application of carbon capture and storage technologies, mitigating the effects of climate change. Carbon capture and storage (CCS) is regarded as one of the most efficient technologies that allows carbon intensive industries to continue to operate with lower CO SB 2 sb emissions. Moita et al. [[3]] examined experimentally the mineral carbonation of CO SB 2 sb in plutonic ophiolitic mafic rocks through a set of laboratory experiments on cumulate gabbro and gabbro-diorite specimens from the Sines Massif (Portugal). [Extracted from the article]

Pillow lavas, massive lava flows, and sub-volcanic dikes of tholeiitic basaltic composition are found to be members of the Vrinena, Aerino, Eretria, and Velestino dispersed Middle–Upper Jurassic ophiolitic units in East Othris. The Vrinena and Eretria ophiolitic units appear to have been emplaced onto the Pelagonian continental margin during the Upper Jurassic–Lower Cretaceous, whereas the Aerino and Velestino units seem to have been finally emplaced during post-Palaeocene times. Geochemically these are divided into two groups: Group I includes subduction-related boninites and low-Ti basalts from the Vrinena and Aerino units, and Group II high-Ti basalts show spreading-type characteristics occurring in the Eretria and Velestino units. Primary magma of the Group I volcanics appears to have been formed after high partial melting degrees (~18%) of a highly depleted harzburgitic mantle source, under relatively high temperatures (mantle potential temperature ~1372°C). Petrogenetic modelling also suggests that the primary magma of the Group II volcanics were formed after lower partial melting degrees (~7%) of a moderately depleted mantle source. The petrological and geochemical data from the East Othris dispersed and diversely emplaced ophiolitic units provide evidence of a common intra-oceanic supra-subduction zone (SSZ) origin within the Pindos oceanic strand of the Western Tethys. Specifically, Group I lavas and dikes from Vrinena seem to represent the extrusive part of an almost complete fore- to island-arc ophiolitic sequence. Dikes of Aerino most likely correspond to fore-arc magmatic material that intruded within exhumed serpentinized ultramafic rocks through a subduction channel that developed close to the slab and towards the fore-arc and the accretionary prism. The Group II volcanics either corresponded to a fore-arc magmatic expression, which extruded earlier than Group I volcanics and prior to the establishment of a mature subduction zone, or represent back-arc to island-arc magmatism that was contemporaneous to the fore-arc magmatic activity during rollback subduction. [ABSTRACT FROM AUTHOR]

Large ultramafic bodies of the East Othris ophiolite in Central Greece consist of serpentinites, of harzburgite precursors, as well as serpentinized lherzolites, which have been intruded by thin dykes of olivine-rich and olivine-poor pyroxenites. They represent parts of partially altered upper mantle wedge rocks in a Mid-Late Jurassic intraoceanic subduction setting of the Pindos microocean, a western strand of the Tethyan oceanic realm. Serpentinization and rodingitization occurred during their exhumation toward the fore-arc oceanic region and accretionary prism through a subduction channel. Petrography and geochemistry show that protoliths of most serpentinites and serpentinized peridotites are harzburgites, while few are more fertile lherzolites. Petrogenetic modeling reveals that the former harzburgites correspond to highly depleted residual mantle peridotites, which formed after moderate degrees (~13-20 %) of hydrous partial melting, whereas lherzolites, being closely related to the ophiolitic mantle peridotites of West Othris, resulted after lower partial melting degrees (~7-10 %). Mineral chemistry and geochemical data from pyroxenites imply that they have been derived after crystallization of a subduction-related IAT hydrous magma that formed after moderate partial melting degrees (~14-19 %), quite similar to those that produced the harzburgites. Melting processes for the East Othris mantle peridotites occurred in the spinel-stability field, at estimated equilibrium temperatures ranging between 900 and 1,050 °C and pressures between 1.4 and 1.7 GPa, in a rather highly oxidized environment. It is estimated that the primary IAT magma, formed under relatively high temperatures with liquidus temperature at ~1,260 °C and mantle potential temperature at ~1,372 °C. Cooling rates of the shallow mantle beneath the Pindos oceanic basin, from its Mid-Triassic rift/drift phase and the subsequently developed Mid-Late Triassic short-lived intraoceanic subduction, to the Mid-Late Jurassic main subduction phase, are estimated at ~0.7 and ~1.6 °C/Ma, respectively, with the latter being considered as unusually high. [ABSTRACT FROM AUTHOR]

East Othris area consists of scattered ophiolitic units, as well as ophiolitic mélange occurrences, which encompass gabbroic rocks. These rocks have been affected by low-grade ocean floor metamorphism ( T < 350°C and P < 8 kbar). Based on their petrography, mineral chemistry and geochemistry gabbroic rocks have been distinguished into gabbros and diorites, with the latter being divided into two groups. Gabbros seem to have been formed from moderate to high partial melting degrees (~8-25%) of a highly depleted mantle source, while group (1) diorites have been differentiated after variable fractionation processes (up to 30%). Group (2) diorites seem to have been derived from low partial melting degrees (~3%) of a fertile or moderately depleted mantle source and with extensive fractionation processes (~50%). Geochemical results suggest that partial melting processes occurred at relatively shallow depths, in the plagioclase-spinel stability field, while amphibole chemistry data indicate shallow level crystallization. Chondrite and PM-normalized patterns, Th/Yb, and Nb/Th ratios as well as mineral chemistry analyses show that gabbros and group (1) diorites (with relatively low PM-normalized Nb and Ta values and negative Ti anomalies) suggest subduction processes, while group (2) diorites are MORB or BAB related. Some gabbros have been characterised as high-Mg, being compositionally similar to picrites or boninites. Variability in extent of partial melting of the mantle source and the different geotectonic environment affinities are consistent with a supra-subduction zone (SSZ) origin of the east Othris ophiolites. The fact that IAT related rocks are more abundant in east rather than in west Othris may possibly be explained by a slab rollback model retreating to the east within the Pindos oceanic basin. [ABSTRACT FROM AUTHOR]

Μining waste, processing by-products and mine water discharges pose a serious threat to the environment as in many cases they contain high concentrations of toxic substances. However, they may also be valuable resources. The main target of the current review is the comparative study of the occurrence of rare earth elements (REE) in mining waste and mine water discharges produced from the exploitation of coal, bauxite, phosphate rock and other ore deposits. Coal combustion ashes, bauxite residue and phosphogypsum present high percentages of critical REEs (up to 41% of the total REE content) with ΣREY content ranging from 77 to 1957.7 ppm. The total REE concentrations in mine discharges from different coal and ore mining areas around the globe are also characterised by a high range of concentrations from 0.25 to 9.8 ppm and from 1.6 to 24.8 ppm, respectively. Acid mine discharges and their associated natural and treatment precipitates seem to be also promising sources of REE if their extraction is coupled with the simultaneous removal of toxic pollutants. [ABSTRACT FROM AUTHOR]

The sustainable use of agricultural, industrial and human waste products as raw materials in the construction industry has been extensively investigated. This study aimed to conceive an innovative concrete composition mainly using recycled materials, which, as a result as waste from human activities and natural organic growth, such as animal bones and human hair, will be used in different mixtures in order to prepare concrete specimens. More specifically, the effect of these materials upon the final concrete strength was investigated, as well as how their petrographic characteristics may influence the durability of concrete specimens. Special emphasis was placed on the effect of the artificial increase in bone and hair microroughness and how these can improve the mechanical strength of the final product. The research results point towards the fact that the percentage of the replacement of natural aggregate rocks by animal bones tends to be enhanced by the increase in their microroughness using quartz primer. In addition, the use of bones with increased artificial microroughness and a certain percentage of human hair with increased microtopography seems to be the ideal mixture for the replacement of natural aggregates for the production of normal concrete. [ABSTRACT FROM AUTHOR]

In West Macedonia (Greece), CO2 accounts as one of the largest contributors of greenhouse gas emissions related to the activity of the regional coal power plants located in Ptolemaida. The necessity to mitigate CO2 emissions to prevent climate change under the Paris Agreement's framework remains an ongoing and demanding challenge. It requires implementing crucial environmentally sustainable technologies to provide balanced solutions between the short-term needs for dependency on fossil fuels and the requirements to move towards the energy transition era. The challenge to utilise and store CO2 emissions will require actions aiming to contribute to a Europe-wide CCUS infrastructure. The Horizon 2020 European Project "STRATEGY CCUS "examines the potential for CO2 storage in the Mesohellenic Trough from past available data deploying the USDOE methodology. Research results show that CO2 storage capacities for the Pentalofos and Eptachori geological formations of the Mesohellenic Trough are estimated at 1.02 and 0.13 Gt, respectively, thus providing the potential for the implementation of a promising method for reducing CO2 emissions in Greece. A certain storage potential also applies to the Grevena sub-basin, offering the opportunity to store any captured CO2 in the area, including other remote regions. [ABSTRACT FROM AUTHOR]

Underground geological energy and CO2 storage contribute to mitigation of anthropogenic greenhouse-gas emissions and climate change effects. The present study aims to present specific underground energy and CO2 storage sites in Greece. Thermal capacity calculations from twenty-two studied aquifers (4 × 10−4–25 × 10−3 MJ) indicate that those of Mesohellenic Trough (Northwest Greece), Western Thessaloniki basin and Botsara flysch (Northwestern Greece) exhibit the best performance. Heat capacity was investigated in fourteen aquifers (throughout North and South Greece) and three abandoned mines of Central Greece. Results indicate that aquifers present higher average total heat energy values (up to ~6.05 × 106 MWh(th)), whereas abandoned mines present significantly higher average area heat energy contents (up to ~5.44 × 106 MWh(th)). Estimations indicate that the Sappes, Serres and Komotini aquifers could cover the space heating energy consumption of East Macedonia-Thrace region. Underground gas storage was investigated in eight aquifers, four gas fields and three evaporite sites. Results indicate that Prinos and South Kavala gas fields (North Greece) could cover the electricity needs of households in East Macedonia and Thrace regions. Hydrogen storage capacity of Corfu and Kefalonia islands is 53,200 MWh(e). These values could cover the electricity needs of 6770 households in the Ionian islands. Petrographical and mineralogical studies of sandstone samples from the Mesohellenic Trough and Volos basalts (Central Greece) indicate that they could serve as potential sites for CO2 storage. [ABSTRACT FROM AUTHOR]

Greece is considered amongst the world's top marble producers in the global carbonate ornamental stone market. Selected Greek carbonate ornamental stones considered in our study suite are characterized by their distinctive and in some cases unique appearance, having a significant impact on their commercial value. Their wide range of colour varieties and their physico-mechanical properties are closely related to their mineral assemblage, chemical constitution, petrographic properties, structural defects, which in turn depend highly upon their metamorphic/diagenetic grade and in some cases hydrothermal processes that affected them. This study endeavors to feature the petrographic, mineralogical and geochemical properties of the main Greek carbonate ornamental stones from selected localities and their by-product waste material used as aggregates. The documented data aims to serve a better understanding of the dynamic Greek marble industry by relating their mineral and chemical properties with their physico-mechanical and aesthetic characteristics. [ABSTRACT FROM AUTHOR]

We investigate with this study the effectiveness of mechanically activated serpentinite in capturing Cu (II) from the multi-constituent acidic wastewater of the pit lakes of the Agios Philippos mine (Greece), proposing specific areas with serpentinites suitable for such environmental applications. For this purpose ultramafic rock samples that are characterized by variable degrees of serpentinization from ophiolitic outcrops exposed in the regions of Veria-Naousa and Edessa have been examined regarding their capacity to remove the toxic load of Cu (II) from wastewater after having been mechanically activated through a Los Angeles (LA) machine (500, 1000 and 1500 revolutions). The more serpentinized and mechanically activated samples, as they have been characterized after a combination of various mineralogical, petrographic, geochemical analyses as well as after different stresses of abrasion and attrition, seem to be more effective in Cu removal than the less serpentinized ones. Selective removal of Cu (II) in the wroewolfeite phase was obtained by using the mechanically activated highly serpentinized ultramafic rocks. Furthermore, areas with highly serpentinized ultramafic rocks defined after petrographic mapping, using GIS method, which can potentially be used as filters for the effective Cu (II) removal from industrial wastewater are suggested. [ABSTRACT FROM AUTHOR]

This study investigates how the petrographic features of Klepa Nafpaktias sandstones affect their behavior in construction applications such as concrete, in environmental applications such as energy storage as well as whether they are suitable for the above uses. For achieving this goal, sandstones (ten samples) were collected in order to study their petrographic characteristics using petrographic microscope and GIS software, as well as their basic physical, mechanical and physicochemical properties were also examined. Concrete specimens (C25/30) were made according to international standards including the investigated aggregate rocks in various grain sizes. Various sandstones were tested and classified in three district groups according to their physicomechanical features as well as to their petrographic and microtopographic characteristics. Concrete strength's results determined the samples into three groups which are in accordance with their initial classification which was relative to their grain size (coarse to fine-grained). As the grain size decreases their physicomechanical and physicochemical properties get better resulting in higher concrete strength values (25 to 32 MPa). Furthermore, the proposed ratio C/A (crystals/mm2) seems to influence the aggregate properties which constitute critical factors for the final concrete strength, presenting the more fine-grained sandstones as the most suitable for concrete aggregates. Concerning the use of Klepa Nafpaktias sandstones as potential energy reservoirs, the studied sandstones presented as suitable for CO2 storage according to their physicomechanical characteristics. [ABSTRACT FROM AUTHOR]

The presence or the absence of swelling clay minerals in rocks, which are used in various construction applications, constitutes a determinant factor for their strength, and consequently, in their general behavior in various construction applications, as they have the ability to swell up to 400 times of their usual volume, causing failures to any application in which they participate. The aim of this study is to respond to the question of whether the empirical method of methylene blue yields equally safe and correct results in different types of igneous rocks and if not, which is the determining factor affecting the results. The answer to this complex question is feasible by investigating the microscopic structure and the mineralogy of the studied rocks, and particularly, using the content of specific phyllosilicate minerals which may be related or not with the methylene blue values. According to the results, the methylene blue test seems to work correctly for the intermediate (Group I) and mafic (Group II) examined rocks, but it seems to be wrong for the highly serpentinized ultramafic rocks (up to 70% of serpentine) (Group III). [ABSTRACT FROM AUTHOR]

Pleistocene alkaline basaltic lavas crop out in the region of Volos at the localities of Microthives and Porphyrio. Results from detailed petrographic study show porphyritic textures with varying porosity between 15% and 23%. Data from deep and shallow water samples were analysed and belong to the Ca-Mg-Na-HCO3-Cl and the Ca-Mg-HCO3 hydrochemical types. Irrigation wells have provided groundwater temperatures reaching up to ~30 °C. Water samples obtained from depths ranging between 170 and 250 m. The enhanced temperature of the groundwater is provided by a recent-inactive magmatic heating source. Comparable temperatures are also recorded in adjacent regions in which basalts of similar composition and age crop out. Estimations based on our findings indicate that basaltic rocks from the region of Volos have the appropriate physicochemical properties for the implementation of a financially feasible CO2 capture and storage scenario. Their silica-undersaturated alkaline composition, the abundance of Ca-bearing minerals, low alteration grade, and high porosity provide significant advantages for CO2 mineral carbonation. Preliminary calculations suggest that potential pilot projects at the Microthives and Porphyrio basaltic formations can store 64,800 and 21,600 tons of CO2, respectively. [ABSTRACT FROM AUTHOR]