ON THE OCCURRENCE OF A VOLCANIC ASH LAYER IN THE XYLOKASTRO AREA, NORTH PELOPONNESUS, GREECE: MINERALOGY AND GEOCHEMISTRY

This paper reports, for the first time, the occurrence of an ash layer intercalated within the Plio-Pleistocene lacustrine deposits near Xylokastro area, North Peloponnesus, Greece. Petrographic and geochemical characteristics of the ash layer are the basis of this study. An attempt was made to correlate the present findings to the reported data from other ash deposits. The composition of the ash bed showed a dacitic to rhyolitic calc alkaline suit. The geochemistry of the volcanic ash indicates high crustal contamination of the lava and points to an origin from the northwest part of the Aegean volcanic arc

Exhumed hydrocarbon-seep authigenic carbonates from Zakynthos island (Greece): Concretions not archaeological remains

In Zakynthos Island (Greece), authigenic cementation of marine sediment has formed pipelike, disc and doughnut-shaped concretions. The concretions are mostly composed of authigenic ferroan dolomite accompanied by pyrite. Samples with >80% dolomite, have stable isotope compositions in two groups. The more indurated concretions have δ 18O around +4‰ and δ 13C values between -8 and -29‰ indicating dolomite forming from anaerobic oxidation of thermogenic methane (hydrocarbon seep), in the sulphate-methane transition zone. The outer surfaces of some concretions, and the less-cemented concretions, typically have slightly heavier isotopic compositions and may indicate that concretion growth progressed from the outer margin in the ambient microbially-modified marine pore fluids, inward toward the central conduit where the isotopic compositions were more heavily influenced by the seep fluid. Sr isotope data suggest the concretions are fossil features, possibly of Pliocene age and represent an exhumed hydrocarbon seep plumbing system. Exposure on the modern seabed in the shallow subtidal zone has caused confusion, as concretion morphology resembles archaeological stonework of the Hellenic period

The association between frailty and MRI features of cerebral small vessel disease

Frailty is a common syndrome in older individuals that is associated with poor cognitive outcome. The underlying brain correlates of frailty are unclear. The aim of this study was to investigate the association between frailty and MRI features of cerebral small vessel disease in a group of non-demented older individuals. We included 170 participants who were classified as frail (n = 30), pre-frail (n = 85) or non-frail (n = 55). The association of frailty and white matter hyperintensity volume and shape features, lacunar infarcts and cerebral perfusion was investigated by regression analyses adjusted for age and sex. Frail and pre-frail participants were older, more often female and showed higher white matter hyperintensity volume (0.69 [95%-CI 0.08 to 1.31], p = 0.03 respectively 0.43 [95%-CI: 0.04 to 0.82], p = 0.03) compared to non-frail participants. Frail participants showed a non-significant trend, and pre-frail participants showed a more complex shape of white matter hyperintensities (concavity index: 0.04 [95%-CI: 0.03 to 0.08], p = 0.03; fractal dimensions: 0.07 [95%-CI: 0.00 to 0.15], p = 0.05) compared to non-frail participants. No between group differences were found in gray matter perfusion or in the presence of lacunar infarcts. In conclusion, increased white matter hyperintensity volume and a more complex white matter hyperintensity shape may be structural brain correlates of the frailty phenotype.Ophthalmic researc

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Authigenic silicates and silica polymorphs in the Miocene saline- alkaline deposits of the Karlovassi Basin, Samos, Greece

The four successions are, from the base upward, carbonates, tuffaceous rocks, claystones, and porcelanites. The general pattern of zonation and distribution of authigenic silicates as well as their chemical characteristics indicates the presence of a saline-alkaline lake during Miocene times. -from Autho

Phosphate deposits of Neogene age in Greece. Mineralogy, geochemistry and genetic implications

In Greece, several occurrences of phosphates have been located in Mesozoic and Cenozoic sedimentary rocks. The aim of the present paper is to describe the mineralogy, geochemistry and the origin of the phosphates deposited in marine and lacustrine basins of Neogene age in Greece. Phosphates of marine origin formed in an outer shelf-upper slope environment (Palliki Peninsula, Kefalonia Island) as well as in a hemipelagic environment (Heraklion, Crete Island). In both the deposits, the phosphate minerals belong to the apatite group. In Kefalonia Island, phosphatic material accumulations occur in the field as scattered or accumulated vertebrate bones, fish teeth and other biogenic components, hosted in a sandy limestone of Upper Tortonian age. On a microscopic scale, in the groundmass of the limestone, phosphate minerals are present as fillings and secondarily as replacements of foraminiferal and other calcareous microfossil tests. In Crete Island, burrowed cobbles and phosphatic concretions up to 10 cm in diameter have been detected east of Heraklion town. The phosphatic material is hosted in a sandy marlstone that is interbedded with diatomaceous rocks of Middle Pliocene age. Phosphates of lacustrine origin have been formed in the NW-SE-oriented Upper Miocene basins of Florina-Ptolemais and Elassona-Sarantaporo, located, respectively, in western Macedonia and Thessaly, Greece. The phosphate minerals are mainly represented by Ca/Fe phosphates such as anapaite and mitridatite and secondarily by Ca phosphates of the apatite group that are hosted in a thick succession of clayey diatomite rock. They usually form lenticular layers, asymmetric lenses, nodular and botryoidal aggregates, and faecal pellet replacements. The major and trace element content of a representative set of rocks was studied. Their geochemistry was found to be controlled by the presence of detrital minerals, the host rock mineralogies, and the types of phosphate minerals present. The relatively high amounts of uranium, arsenic and barium detected in some of the phosphate rocks studied are mainly related with organic matter and are comparable to those detected in other phosphate deposits worldwide. In the deposits studied, phosphogenesis was mainly promoted by the decay of organic substances derived from diatoms, fishes and other vertebrates, leaves and trunks, and faecal pellets in a highly reducing environment on or just below the sea or lake bottom, and secondarily by the feeding of the basin with phosphate-bearing nutrients that originated in the land. © 2003 Elsevier GmbH. All rights reserved

Use of zeolite and biogenic silica rich rocks as olive oil mill waste absorbents

Microporous materials have been tested as absorbent of olive oil mill waste (OOMW) from a three-phase mill. The aim of the present study is to characterise and test the OOMW absorption capacity of fine-grained rocks. The materials tested were zeolite-rich tuff, clay and zeolite-rich tuff, opal-A-rich clayey rock and opal-CT and zeolite-rich clays. The samples were characterised and physico-chemically analysed. The samples exhibit significant differences of their physicochemical properties. Correlations indicated that the OOMW absorption capacity depended mainly on the cumulative volume of pores. Very small pores did not affect considerably the OOMW uptake in contrast to the bigger pores. The opal-CT and zeolite-rich clayey rock was the most efficient absorbent. It is concluded that the synergistic action of three structurally diverse, randomly ordered microporous components which rarely coexist in rocks naturally, results in high cumulative volume of pores and an increased absorption capacity. © 2019 Inderscience Enterprises Ltd

Origin of barite in Tertiary marine sedimentary rocks from Lefkas Island, Greece

Siliceous and calcareous biogenic rocks host pervasive, although volumetrically minor, authigenic barite on Lefkas Island. The barite composes up to 10% of the carbonate-free fraction of samples. In decreasing order of abundance, authigenic barite occurs as infilled foraminifera and radiolarian tests, disseminated grains and aggregates in porcelanite and siliceous limestone, replaced siliceous and calcareous biogenic tests, and thin laminae and lenses. The source of the barium was probably from the decomposition of organic matter derived from plankton and bacteria and from the diagenesis of silica and carbonate tests. The source of the sulfate ion was seawater; possibly additional sulfate was produced and utilized in microenvironments from degradation of organic matter. -from Author

Hydrotalcite and an amorphous clay mineral in high-magnesium mudstones from the Kozani Basin, Greece

The paper describes two unusual lithologies that occur in a sequence of Mg-rich lacustrine sediments in northern Greece. The first is a laminated mudstone in which layers composed of magnesian smectite alternate with layers composed of an amorphous clay of similar chemical composition. The second lithology is a thin bed of mudstone in which the only crystalline constituent is hydrotalcite (a magnesium aluminum hydroxide), accompanied by amorphous high-magnesium clay. Hydrotalcite has not previously been recorded from sedimentary rocks except as a product of industrial pollution. The high-magnesium clay is considered to have formed by precipitation from Mg-rich lake water onto volcanic ash particles, whilst the hydrotalcite has filled the molds left by dissolution of volcanic glass within the clay-coated particles