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Raman elastic geobarometry has increasingly been used complementary to metamorphic phase equilibria to estimate the conditions of recrystallization in metamorphic rocks. The procedure of applying Raman elastic barometry to host-inclusion mineral systems requires several steps that involve various assumptions. One of the most essential assumptions is that the mineral host-inclusion system behaves in an elastic and reversible manner. We discuss the discrepant results obtained by different authors employing different analytical solutions for elasticity and explore the assumptions lying behind each method. Furthermore, we evaluate numerically linear and non-linear elastic solutions and show their discrepancies. Both formulations are tested against recently published experiments on quartz inclusions in garnet (QuiG) at pressures up to 3 GPa, and we find a very good agreement between calculated and experimental pressure values (within 10% relative error). We subsequently apply our new elastic geobarometer to a calc-silicate gneiss from the Rhodope Metamorphic Province (N. Greece). The results of Raman elastic barometry combined with garnet-clinopyroxene geothermometry yield eclogite-facies conditions (~720 ± 40 °C, ~1.5 ± 0.2 GPa). These results are comparable to a high-temperature metamorphic overprint deduced from phase equilibria modeling in surrounding lithologies (730 ± 40 °C, ~1.2 ± 0.1 GPa). Our findings indicate that the estimated pressure from Raman elastic barometry is consistent with a significant viscous relaxation at high temperatures. We conclude that although Raman elastic barometry is a powerful tool for pressure estimation in metamorphic rocks, its pressure estimates do not necessarily correspond to entrapment conditions. Our results are consequential for the estimates of reaction overstepping in high-grade metamorphic rocks. © 2020

The Apliki mine, a Cyprus-type massive sulphide deposit in Cyprus, was exploited for copper until the mid-1970s. Abandonment of the mine left a deep pit that now hosts a lake fed by surface runoff from the surrounding mineralized zone and hydrothermally altered basalt. Oxidation of the sulphide minerals and factors such as climate and terrain relief control the water–rock interactions that generate acid mine drainage (AMD), which ultimately affects and defines the quality of the lake waters. Pyrite and chalcopyrite constitute an almost inexhaustible sulphide source that leads to the formation of a variety of secondary iron and copper mineral phases. The secondary mineral assemblages in the ore zone are mainly iron, copper, and magnesium sulphates, whereas the lakeshore assemblage is dominated by magnesium-, calcium-, sodium-, and aluminum-bearing sulphate minerals. Near the lakeshore, the highly soluble iron sulphate salts dissolve in the lake water, increasing its iron content. Other less soluble salts are more stable and persist in the lakeshore environment. The precipitation and dissolution of efflorescent salts, and, to a lesser extent, the oxidative weathering of the remaining ore minerals, produce additional AMD. Due to the perpetual cycle of mineral dissolution and precipitation, the lake has a low pH (≈3) and contains high concentrations of some contaminants. The processes that contribute to the formation of the efflorescent mineral assemblages and their environmental impact on pit lake waters, and indeed the complete geochemical system, is a typical example of secondary mineral formation in Cyprus-type Cu-pyrite massive sulphide ore deposits. © 2016, Springer-Verlag Berlin Heidelberg.

We studied the effects of water quality on the hydration of quicklimes prepared from calcitic limestone and dolomitic limestone during calcination at 1050 °C. At a low total chloride and sulfate content, reactivity is insensitive to concentration and no effect on quicklime slaking is seen. At higher concentrations, however, we observe a chromatographic effect for chlorides and sulfates. Concentrated chlorides react with the slaking water, forming products such as CaCl2 that are much more soluble than Ca(OH)2, which facilitates transformation of quicklime to slaked lime. In the range of sulfate concentrations in natural waters we observed no effect of sulfates during quicklime hydration. Consequently, in natural waters and their mixtures (conductivity < 2600 μS cm-1), only chloride concentrations are found to promote quicklime hydration. These results suggest that water treatment technologies, applied to natural light brackish water compositions, will not lead to quality improvement for lime-industry products. This journal is © The Royal Society of Chemistry 2016.

Objectives: The aim of this study was to evaluate the sealing ability and morphological microstructure of Biodentine in comparison to ProRoot mineral trioxide aggregate (MTA) after storage in an acidic environment. Materials and methods: Biodentine and ProRoot MTA were prepared and packed into the canal lumen of dentin disks. Twenty specimens of each material were further randomly divided into two groups according to the storage media: group A: materials with saline as storage medium; group B: materials with citric acid buffered at pH 5.4 as storage medium. The sealing ability was evaluated at 1, 3, 6, and 24 h and 1 or 3 months, using a fluid transport model for quantitative analysis of endodontic microleakage. The morphological microstructures of the materials were also evaluated using scanning electron microscopy. Results: During the first 24 h, MTA showed greater fluid transport values than Biodentine in both environments. At the 3-month measurement, when the materials were stored in saline, MTA showed greater ability to prevent fluid movement than Biodentine (p < 0.0001). However, when the materials were stored in an acidic environment, no statistical significant difference was found after 3 months. After storage in saline, both materials showed an uneven crystalline surface with similar hexagonal crystals. The microstructure of Biodentine changed after exposure to citric acid, showing a relatively smooth surface with more spheroidal crystals. Conclusions: The exposure to an acidic environment, within the limits of this study, seems to result in morphological changes of Biodentine in a different manner than MTA. MTA shows good ability to prevent fluid movement over time, in both environments. The ability of Biodentine to prevent fluid movement over time was enhanced in the acidic environment. Clinical relevance: The findings of the present study could imply that both materials are indicated for use in an acidic environment. © 2015, Springer-Verlag Berlin Heidelberg.

Spectroscopic and microscopic (particularly HRTEM) techniques were used to investigate the origin of the colour of natural blue Zn-carbonate (smithsonite). Blue smithsonite is rich in copper, but substitution of zinc cations by copper cations, as proposed in the past for the origin of the colour, is questionable considering the absence of anhydrous divalent copper carbonates in nature. In this work, optical microscopy, SEM-EDS, XRD and laser micro-Raman could not resolve distinct phases either than Zn-carbonate, while NIR spectra excluded known chromophore Cu-hydroxycarbonate minerals. HRTEM studies however could clearly resolve nano-sized (3-7 nm) Cu-rich inclusions (specifically Si/Ca/Cu/As-rich inclusions of at least one phase), which are organised in bands with no topotaxial relation to bulk smithsonite. Electron-beam sensitivity of the samples, even at low electron current densities, did not allow the exact identification of the inclusions. However, it can be safely suggested, for the first time in the literature, that they are the cause of the blue colour in smithsonite.

A ~2.0-million-year-old shallow-submarine sedimentary deposit on Milos Island, Greece, harbours an unmetamorphosed fossiliferous iron formation (IF) comparable to Precambrian banded iron formations (BIFs). This Milos IF holds the potential to provide clues to the origin of Precambrian BIFs, relative to biotic and abiotic processes. Here, we combine field stratigraphic observations, stable isotopes of C, S and Si, rock petrography and microfossil evidence from a ~5-m-thick outcrop to track potential biogeochemical processes that may have contributed to the formation of the BIF-type rocks and the abrupt transition to an overlying conglomerate-hosted IF (CIF). Bulk δ13C isotopic compositions lower than -25‰ provide evidence for biological contribution by the Calvin and reductive acetyl-CoA carbon fixation cycles to the origin of both the BIF-type and CIF strata. Low S levels of ~0.04 wt.% combined with δ34S estimates of up to ~18‰ point to a non-sulphidic depository. Positive δ30Si records of up to +0.53‰ in the finely laminated BIF-type rocks indicate chemical deposition on the seafloor during weak periods of arc magmatism. Negative δ30Si data are consistent with geological observations suggesting a sudden change to intense arc volcanism potentially terminated the deposition of the BIF-type layer. The typical Precambrian rhythmic rocks of alternating Fe- and Si-rich bands are associated with abundant and spatially distinct microbial fossil assemblages. Together with previously proposed anoxygenic photoferrotrophic iron cycling and low sedimentary N and C potentially connected to diagenetic denitrification, the Milos IF is a biogenic submarine volcano-sedimentary IF showing depositional conditions analogous to Archaean Algoma-type BIFs. © 2015 John Wiley & Sons Ltd.

The Chalkidiki block in Northern Greece represents the southwesternmost piece of the ultrahigh-pressure Rhodope and has played an important role in the evolution of the North Aegean. The eastern part of the Chalkidiki block is a basement complex (Vertiskos Unit) that is made largely of Palaeozoic granitoids and clastic sediments that metamorphosed during the Mesozoic. This basement is traditionally considered as part of the Rhodopean hanging-wall, an assignment mainly supported by the absence of high-pressure mineral indicators and the presence of a regional medium-pressure/medium-temperature amphibolite-facies Barrovian metamorphic imprint. Toward the west, the basement is juxtaposed with meta-sedimentary (Circum-Rhodope belt) and arc units (Chortiatis Magmatic Suite) that carry evidence of a Mesozoic high-pressure/low-temperature event. In this study, garnet-staurolite-mica schists from the eastern part of the basement were examined by means of micro-textures, mineral chemistry and isochemical phase-diagram sections in the system NCKFMASHMn(Ti) [Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-MnO-(TiO2)]. The schists represent former Mesozoic sedimentary sequences deposited on the Palaeozoic basement. We document the presence of a relict eclogite-facies mineral assemblage (garnet+chloritoid+phengite+rutile) in an amphibolite-facies matrix composed of garnet+staurolite+phengite±kyanite. Model results suggest the existence of a high-pressure/medium-temperature metamorphic event (1.9GPa/520°C) that preceded regional re-equilibration at medium-pressure/medium-temperature conditions (1.2GPa/620°C). Clearly, the eastern part of the Chalkidiki block (basement complex) retains memory of an as yet unidentified Mesozoic eclogitic metamorphic event that was largely erased by the later Barrovian overprint. In light of our findings, the basement complex of the Chalkidiki block shares a common tectono-metamorphic evolution with both the high-pressure units to the west, and the high-grade Rhodopean gneisses further to the northeast. Our results are consequential for the geodynamic reconstruction of the Rhodope since they require participation of the Chalkidiki block to the well-established Mesozoic subduction system. © 2015 Elsevier B.V.

No abstract available.

We have analyzed gallstones from four patients of Europe and particularly from England (including samples from a mother and a daughter) and Greece. According to the XRD, FTIR, NMR and laser micro-Raman results the studied materials correspond to typical cholesterol monohydrate (ChM). The micro-morphology of cholesterol microcrystals was investigated by means of SEM-EDS. The XRF results revealed that Ca is the dominant non-organic metal in all gallstones (up to ~1.95wt.%) together with Fe, Cu, Pb and Ni (up to ~19ppm for each metal). Gallstones from England contain additional Mn (up to ~87ppm) and Zn (up to ~6ppm) while the sample of the mother contains negligible Zn and Mn, compared to that of her daughter, but significant As (~4.5ppm). All cholesterol gallstones examined are well enriched in potentially toxic metals (Pb, as well as Ni in one case) and metalloids (As also in one case) as compared to the global average. The position of Zn, which is a characteristic biometal, in the structure of cholesterol, was investigated by molecular simulation using the Accelrys Materials Studio® software. On the basis of IRMS results, all gallstones examined exhibit a very light δ13C signature (average δ13C ~-24‰ PDB). Gamma-ray spectrometry measurements indicate the presence of 214Pb and 214Bi natural radionuclides due to the 238U series as well as an additional amount of 40K. © 2012 Elsevier GmbH.

Pure metallic Pb foils were exposed to the atmosphere of Athens for different periods of time (up to 150 non-rainy days) in the summer of 2005. The interacted Pb surfaces were probed using the 12C(d,p)13C reaction (Ed: 1100 keV) at the Tandem accelerator of the NCSR "DEMOKRITOS". Laser-μRaman and SEM-EDS were also complementary applied. Using the above methodology we recorded surface carbon profiles and concentrations as a function of the exposure time, corresponding to the evolution of the carbonate layer formed onto Pb foils due to the interaction with atmospheric H2O and CO2. The C-containing surface layer was found to be stabilized after ∼120 days. Further investigation by means of laser-μRaman and SEM-EDS indicated that the patina initially consists of Pb-hydroxycarbonates (hydrocerussite) overgrowing Pb-oxides, whereas Pb-sulfates (anglesite) and possibly basic Pb-sulfates are formed at the end of the patination process. The crystal growth of Pb-sulfates, or most likely the transformation of hydroxycarbonates to sulfates, is attributed to the pollution of Athens atmosphere by SO2. © 2011 Elsevier B.V. All rights reserved.

In the present study the preparation of glass-ceramic composite materials containing lime-free clay and industrial waste: steel cooling refuse from metallurgical plant, waste glass from waste fibre production, aluminium scrap metal processing waste were investigated. Taking into account the thermal properties and chemical composition of raw materials, various waste containing glass-ceramics composites were prepared by powder technology. Dense glass-ceramic composite materials (bulk density 2.52 – 3.24 g/cm3; water uptake 0.95 - 5.5 %) were produced in sintering temperature range from 1140oC to 1180oC. Considering the low water uptake and values of mechanical properties determined (the modulus of elasticity E = (1150 – 1300) ± 200 МРа and the compressive strength σ* = (50,6 – 89,9) ± 15,0 МРа), the produced composite materials could be regarded as corresponding to the group BI of the standard LVS EN 176:1991 „Pressed ceramic tiles with the low water uptake” (E

The surface of a typical Greek (Thassian) dolomitic marble was studied after interaction with U- and Th-containing aqueous solutions (1000 mg/L, free-drift experiments for 1 week at atmospheric PCO2), using 12C-RBS and Laser μ-Raman spectroscopy. Powder-XRD and SEM-EDS were also applied to investigate the phases deposited on the surface of the interacted samples. The obtained results indicated a considerable removal of U from the aqueous medium mainly due to massive surface precipitation of amorphous UO2-hydroxide phases forming a relatively thick (μm-sized) coating on the carbonate substrate. The interaction of Th with dolomitic marble surface is also intense leading to a formation of an amorphous Th-hydroxide layer of similar thickness but of significantly lower elemental atomic proportion. © 2008 Elsevier B.V. All rights reserved.