Post-magmatic processes recorded in bimodal chromitites of the East Chalkidiki meta-ultramafic bodies, Gomati and Nea Roda, Northern Greece

The meta-ultramafic bodies of Gomati and Nea Roda are situated in the Serbomacedonian Massif. They demonstrate bimodal character in terms of chromitite chemistry with both Cr- and Al-rich chromitites outcropping in proximity, with no obvious tectonic structure intercepting those two varieties. Based on the trace element abundances in spinel grains, metamorphosis reached amphibolite facies, forming porous spinel. Chromitite-hosted chlorite and garnet chemistry correlates with greenschist facies temperatures and formation of zoned spinel grains. Despite the metamorphic overprint, some of the primary features of the chromitites have been preserved. The PGE contents demonstrate an increase in Pd/Ir ratios in some chromitites pointing to fractionation, whereas low ratios of mostly Cr-rich chromitites point to partial melting being the main mechanism that controls PGE mineralization. The normalized trace element patterns of spinel-group minerals revealed that Al-rich chromitites were generated in spreading settings in a back-arc and the Cr-rich counterparts in SSZ environment. The parental melts of Al-rich and Cr-rich chromitites demonstrate MORB and boninitic affinities, respectively. The meta-ultramafic protoliths were modified within a subduction zone, with significant input of a sedimentary source, as confirmed by the chemistry of serpentinite, diopside and Sb-mineralization. These results suggest common geotectonic processes within the Rhodope and the Serbomacedonian massif, that have affected the ultramafic bodies and chromitite occurrences

Carbon Capture, Utilisation and Storage as a Defense Tool against Climate Change: Current Developments in West Macedonia (Greece)

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

High-pressure subduction-related serpentinites and metarodingites from East Thessaly (Greece): Implications for their metamorphic, geochemical and geodynamic evolution in the Hellenic-Dinaric ophiolite context

Metaophiolites that consist mainly of serpentinites or metabasites outcrop in the East Thessaly region, Central Greece. These formations, along with some ophiolite outcrops, have been variably emplaced onto the Pelagonian tectonostratigraphic zone as dispersed and deformed thrust sheets. Based upon their estimated metamorphic degree, serpentinites from the metaophiolites and ophiolitic units of East Thessaly have been divided into three groups: Group-1 serpentinites from East Othris, include lizardite and antigorite in balanced amounts, defining greenschist fades metamorphic conditions (similar to 320-340 C-omicron, P approximate to 6-7 kbar). Group-2 serpentinites are marked by further prevalence of antigorite over lizardite, suggesting upper-greenschist to lower-blueschist fades metamorphism (similar to 340-370 C-omicron, P approximate to 8-10 kbar). Group-3 serpentinites are mainly characterized by the predominance of antigorite corresponding to blueschist facies metamorphism (similar to 360-400 C-omicron P approximate to 11-12 kbar). The chemical composition and mineral chemistry of the East Thessaly serpentinites suggest that their protoliths were highly depleted harzburgites. Group-1 serpentinites exhibit higher Mg/Si ratio values and LOI compared to serpentinite Groups-2 and -3, due to increasing metamorphic conditions of the latter groups. The prominent Cs, U, Pb, As and Sb enrichments point to subduction-related serpentinites that were subjected to fluid/rock interactions. The East Thessaly serpentinites also seem to have undergone deserpentinization retrograde metamorphism (estimated at P < 8 kbar and T < 350 C-omicron). Retrograde metamorphism also had a significant impact on the rodingite intrusions hosted within the serpentinites, forming metarodingites through late-stage derodingitization processes. (C) 2016 Elsevier B.V. All rights reserved

Special Issue “Climate Change, Carbon Capture, Storage and CO2 Mineralisation Technologies”

This Special Issue presents sixteen scientific papers that explore the application of carbon capture and storage technologies, mitigating the effects of climate change [...

Petrological and mineralogical study of the ophiolitic rocks in the region of East Othris

East Othris geologically consists of zones characterized as internal, which include the Sub-Pelagonian (or Maliac), the Pelagonian and the Eastern Greece zone. The first two zones include igneous rocks which are distinguished based on stratigraphic data in those that belong in the Triassic igneous and sedimentary sequence, in the melange formations, in the Jurassic ophiolitic rocks and in the ophiolitic rocks of the post-uppercretaceous nappe. The Triassic igneous rocks consist mainly of pillow lavas with relatively small occurrences of serpentinized ultramafic rocks, accompanied by dyke formed and pyroclastic rocks, ranging compositionally from basic to felsic. Pillow lavas often interchange with sedimentary rocks (pelites, radiolarites and limestones). These igneous rocks appear in the regions of Loggitsi, Agia Marina, Paleoneraida, Spartia and Mili. The Jurassic ophiolitic rocks in eastern Othris usually appear as scattered parts of a dismembered ophiolitic complex, except in Vrinena where the ophiolites form an almost complete ophiolitic sequence in a relatively small area. The Jurassic ophiolitic formations appear in the regions of Karavomilos, Pelasgia and Vrinena, whereas the ophiolitic rocks of the post-uppercretaceous nappe appear in the regions of Eretria, Velestino and Aerino. In the ophiolitic rocks the petrological types recognized are: peridotites, pyroxenites, serpentinites, gabbros, diorites, plagiogranites-rhyodakites, rondigites, volcanic and dyke formed rocks compositionally ranging from basic to intermediate as well as ‘Skarn’ type rocks. The melange formations consist of igneous and sedimentary rocks in chaotic forms. Igneous rocks are mainly volcanic, with clear indications that at least some of them are linked to the Triassic volcanic activity. In these formations the following lithotypes are recognized: Serpentinites, calc-alkaline pillow lavas, rondigites, diorites, plagiogranites, metamorphic soles (amphibolites, greenschists), listwanites, sandstones, limestones and cherts-radiolarites. Serpentinites were formed from metamorphic processes upon ultramafic rocks (harzburgites, lherzolites and wehrlites), while rondigites were formed from metasomatic processes upon gabbroic rocks and dolerites. Rodingitization processes have also affected the Triassic wehlites. Skarn occurrences are only sited in the ophiolitic complex of Vrinena, between marbles, dolerites and rhyodakites. The metamorphic soles have been found in the melange formation of Paleokerasia, formed from metamorphic processes upon basaltic rocks with N-MORB characters but also calc-alkaline. Listwanites resulted from further metasomatism of serpentinites with Si, Ca rich fluids. ..........................................................................................................................Η ανατολική Όθρυ γεωλογικά αποτελείται από ζώνες οι οποίες χαρακτηρίζονται ως εσωτερικές στις οποίες περιλαμβάνονται η Yποπελαγονική (ή Μαλιακή), η Πελαγονική και η ζώνη της Ανατολικής Ελλάδας. Οι δύο πρώτες ζώνες περιλαμβάνουν μαγματικά πετρώματα τα οποία βάση στρωματογραφικών δεδομένων διακρίνονται σε εκείνα που ανήκουν στην Τριαδική μαγματική και ιζηματογενή ακολουθία, στους σχηματισμούς melange, στα οφιολιθικά πετρώματα Ιουρασικής ηλικίας και στους οφιόλιθους του μετα-ανωκρητιδικού καλύμματος. Τα Τριαδικά μαγματικά πετρώματα αποτελούνται κυρίως από pillow λάβες μέσα στις οποίες εμφανίζονται σχετικά μικρής έκτασης σερπεντινιωμένα υπερβασικά πετρώματα, συνοδευόμενα από φλεβικά και πυροκλαστικά πετρώματα βασικής έως όξινης σύστασης. Οι pillow λάβες συχνά εναλλάσσονται με ιζηματογενή πετρώματα (πηλίτες, ραδιολαρίτες και ασβεστόλιθους). Τα μαγματικά αυτά πετρώματα εμφανίζονται στις περιοχές Λογγίτσι, Αγία Μαρίανα, Παλαιονεράιδα, Σπαρτιά και Μύλοι. Τα οφιολιθικά πετρώματα στην ανατολική Όθρυ εμφανίζονται συνήθως ως διάσπαρτα τμήματα διαμελισμένου οφιολιθικού συμπλέγματος, εκτός από την εμφάνιση τους στα Βρύναινα όπου τα οφιολιθικά πετρώματα συνιστούν μία σχεδόν πλήρη οφιολιθική ακολουθία ανεπτυγμένη σε μικρή περιοχή. Οι Ιουρασικοί οφιολιθικοί σχηματισμοί βρίσκονται στις περιοχές Καραβόλυλος, Πελασγία και Βρύναινα, ενώ οι οφιολιθικοί σχηματισμοί του μετα-ανωκρητιδικού καλύμματος βρίσκονται στις περιοχές Ερέτρια, Βελεστίνο και Αερινό. Στα οφιολιθικά πετρώματα οι πετρολογικοί τύποι που αναγνωρίστηκαν είναι: περιδοτίτες, πυροξενίτες, σερπεντινίτες, γάββροι, διορίτες, πλαγιογρανίτες-ρυοδακίτες, ροδιγκίτες, ηφαιστειακά και φλεβικά πετρώματα βασικής έως ενδιάμεσης σύστασης και πετρώματα τύπου ‘Skarn’. Οι σχηματισμοί melange αποτελούνται από μαγματικά, μεταμορφωμένα και ιζηματογενή πετρώματα σε χαοτικές μορφές. Τα μαγματικά πετρώματα είναι κυρίως ηφαιστειακά, με σαφείς ενδείξεις ότι τουλάχιστον μέρος από αυτά συνδέονται στην Τριαδική ηφαιστειακή δραστηριότητα. Αναγνωρίστηκαν οι εξής λιθότυποι: Σερπεντινίτες, ασβεσταλκαλικές pillow λάβες, ροδιγκίτες, διορίτες, πλαγιογρανίτες, μεταμορφικές σόλες (αμφιβολίτες, πρασινοσχιστόλιθοι), λιστβανίτες, ψαμμίτες, ασβεστόλιθοι και κερατόλιθοι-ραδιολαρίτες. Οι σερπεντινίτες προήλθαν από μεταμόρφωση υπερβασικών πετρωμάτων (χαρτζβουργιτών, λερζόλιθων και βερλιτών), ενώ οι ροδιγκίτες από μετασωματικές διεργασίες σε γαββρικά πετρώματα και δολερίτες. Η ροδιγκιτίωση έχει επηρεάσει και Τριαδικούς βερλίτες. Εμφανίσεις skarn παρατηρήθηκαν στο οφιολιθικό σύμπλεγμα στα Βρύναινα, ανάμεσα σε μάρμαρα, δολερίτες και ρυοδακίτες. Τα μεταμορφικά πέλματα που βρέθηκαν συμμετέχουν στο σχηματισμό melange της Παλαιοκερασιάς και προήλθαν από μεταμόρφωση βασαλτικών πετρωμάτων με χαρακτήρες N-MORB αλλά και ασβεσταλκαλικούς. Οι λιστβανίτες προέρχονται από την περαιτέρω μετασωμάτωση σερπεντινιτών με ρευστά πλούσια σε Si και Ca. ..................................................................

Boninitic and tholeiitic basaltic lavas and dikes from dispersed Jurassic East Othris ophiolitic units, Greece: petrogenesis and geodynamic implications

<p>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.</p

Geochemical Occurrence of Rare Earth Elements in Mining Waste and Mine Water: A Review

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