PETROLOGICAL INVESTIGATION OF CARBONATE ROCKS FROM THE IONIAN ZONE (ETOLOAKARNANIA, WESTERN GREECE)

The petrographic features of the carbonate rocks from the Ionian Zone in the Etoloakarnania Prefecture are presented. They are represented by limestones with minor dolomite. The limestones include: (i) wackestones (or sparse micrites), with poor presence of allochems within a mud matrix; (ii) packstones (or packed micrites) with increasing levels of carbonate grains that are still surrounded by micrite matrix, and (iii) grainstones (or sparites) containing allochems that are cemented with sparry calcite crystals, while the mud matrix is absent. Bioclasts are the dominant carbonate components in most of the samples accompanied by infrequent pelloids, intraclasts, lithoclasts and ooids. Crystalline limestones were not identified. Quartz, apatite, barite, anhydrite, halite, clay minerals, magnetite and ilmenite have been determined as accessory phases. The results show that mineralogical and petrographic features of the analyzed carbonate rocks are related to their evolution during the development of the Ionian Zone from a shallow-marine platform to a deep water basin

Widespread abiotic methane in chromitites

Recurring discoveries of abiotic methane in gas seeps and springs in ophiolites and peridotite massifs worldwide raised the question of where, in which rocks, methane was generated. Answers will impact the theories on life origin related to serpentinization of ultramafic rocks, and the origin of methane on rocky planets. Here we document, through molecular and isotopic analyses of gas liberated by rock crushing, that among the several mafic and ultramafic rocks composing classic ophiolites in Greece, i.e., serpentinite, peridotite, chromitite, gabbro, rodingite and basalt, only chromitites, characterized by high concentrations of chromium and ruthenium, host considerable amounts of 13C-enriched methane, hydrogen and heavier hydrocarbons with inverse isotopic trend, which is typical of abiotic gas origin. Raman analyses are consistent with methane being occluded in widespread microfractures and porous serpentine- or chlorite-filled veins. Chromium and ruthenium may be key metal catalysts for methane production via Sabatier reaction. Chromitites may represent source rocks of abiotic methane on Earth and, potentially, on Mars

Characterization of a new laboratory ceramic product from industrial by-products as raw materials and caustic magnesia as additive

Στην εργασία αυτή παρουσιάζεται ένα νέο κεραμικό προϊόν που παράχθηκε από μίξη καυστικής μαγνησίας, που παρασκευάστηκε εργαστηριακά από υψηλής καθαρότητας μαγνησίτη, φυσικού πηλού καθώς και τέφρας πυθμένα και ερυθράς ιλύος, προϊόντα γνωστά για τις δυσμενείς περιβαλλοντικές επιπτώσεις τους. Έπειτα από δοκιμή ποικίλων συνταγών, συμπεράναμε ότι προσθήκη 5% καυστικής μαγνησίας στο κεραμικό προϊόν βελτιώνει τις μηχανικές επιδόσεις του. Αυτό αποδίδεται στο γεγονός ότι το περίκλαστο της καυστικής μαγνησίας σχηματίζει «λαιμούς», οι οποίοι ισχυροποιούν τους δεσμούς στη μικροδομή του κεραμικού, σε συνδυασμό με τον ταυτόχρονο σχηματισμό μικρών ποσοτήτων άμορφου υλικού και την ομοιογενή κατανομή των πόρων, που δημιουργούνται κατά την όπτηση. Με συνδυαστική μελέτη Περιθλασιμετρίας Ακτίνων Χ και Σαρωτικού Ηλεκτρονικού Μικροσκοπίου του κεραμικού υποδείχτηκε η παρουσία αναλλοίωτων φάσεων, προερχόμενων από τις πρώτες ύλες, καθώς και νεοσχηματισμένων κρυστάλλων αλβίτη και μαγνησιοφερρίτη. Τα αποτελέσματα της παρούσας μελέτης δείχνουν ότι η χρήση παραπροϊόντων μπορεί να είναι σημαντική και περιβαλλοντικά φιλική στην παραγωγή φτηνών δομικών κεραμικών.A new ceramic product is introduced by mixing caustic magnesia, produced in the laboratory from pure, high quality magnesite, and natural silt. Bottom ash and red mud, two well known environmentally hazardous industrial by-products, were also added in the mixture. After testing various recipes we concluded that addition of 5% caustic magnesia in the ceramic product greatly enhances its performance. Increase bonding of the ceramic microstructure is attributed to the formation of periclase necks, the concurrent formation of small quantities of amorphous material and the homogeneously distributed pores during the experimental firing of the mixture. Combined X-ray Diffractometry and Scanning Electron Microscopy of the ceramic product revealed the occurrence of unreactive phases, inherited by the raw materials, as well as newly-formed albite and magnesioferrite. Our results show that utilization of by-products may be important and environmental friendly materials in producing low cost ceramic building materials

Eliopoulosite, V7S8, A New Sulfide from the Podiform Chromitite of the Othrys Ophiolite, Greece

The new mineral species, eliopoulosite, V7S8, was discovered in the abandoned chromium mine of Agios Stefanos of the Othrys ophiolite, located in central Greece. The investigated samples consist of massive chromitite hosted in a strongly altered mantle tectonite, and are associated with nickelphosphide, awaruite, tsikourasite, and grammatikopoulosite. Eliopoulosite is brittle and has a metallic luster. In plane-reflected polarized light, it is grayish-brown and shows no internal reflections, bireflectance, and pleochroism. It is weakly anisotropic, with colors varying from light to dark greenish. Reflectance values of mineral in air (Ro, Re’ in %) are: 34.8–35.7 at 470 nm, 38–39 at 546 nm, 40–41.3 at 589 nm, and 42.5–44.2 at 650 nm. Electron-microprobe analyses yielded a mean composition (wt.%) of: S 41.78, V 54.11, Ni 1.71, Fe 1.1, Co 0.67, and Mo 0.66, totali 100.03. On the basis of Σatoms = 15 apfu and taking into account the structural data, the empirical formula of eliopoulosite is (V6.55Ni0.19Fe0.12Co0.07Mo0.04)Σ = 6.97S8.03. The simplified formula is (V, Ni, Fe)7S8 and the ideal formula is V7S8, which corresponds to V 58.16%, S 41.84%, total 100 wt.%. The density, based on the empirical formula and unit-cell volume refined form single-crystal structure XRD data, is 4.545 g·cm−3. The mineral is trigonal, space group P3221, with a = 6.689(3) Å, c = 17.403(6) Å, V = 674.4(5) Å3, Z = 3, and exhibits a twelve-fold superstructure (2a × 2a × 3c) of the NiAs-type subcell with V-atoms octahedrally coordinated by S atoms. The distribution of vacancies is discussed in relation to other pyrrhotite-like compounds. The mineral name is for Dr. Demetrios Eliopoulos (1947–2019), a geoscientist at the Institute of Geology and Mineral Exploration (IGME) of Greece and his widow, Prof. Maria Eliopoulos (nee Economou, 1947), University of Athens, Greece, for their contributions to the knowledge of ore deposits of Greece and to the mineralogical, petrographic, and geochemical studies of ophiolites, including the Othrys complex. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature, and Classification of the International Mineralogical Association (No. 2019-96).© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)