Two slightly lithified volcanic rich layers (VRL) (former tephra) SVT-2 (San Vittorino) and CAC (Castiglione a Casauria) were sampled from two distinct post-evaporitic Messinian stratigraphic ...sections (Abruzzo, Central Italy). They crop only few tens of km apart and are predominantly massive, although some specimens show sedimentary structures. Both VRLs were investigated for the first time by field, mesoscopic, X-ray powder diffraction (XRPD), transmission optical microscopy (TOM), scanning electron microscopy (SEM), bulk composition, electron-microprobe analysis (EMPA) and quantitative textural attributes by image analysis. The XRPD analysis detects the presence of a glass phase, plus few (< 2 area %) magmatic-like feldspars, clinopyroxene and biotite and stratigraphically variable sedimentary minerals such as calcite, dolomite, illite and montmorillonite (from 0 to 40 area %). The 2D image analysis performed on SEM microphotographs reveals that both sections are composed of very fine glass shards, magmatic minerals are never isolated, whilst the carbonate crystals mainly fill voids among volcanic particles. Both these VRLs have identical rhyolitic glass compositions that closely overlap with those of previously-studied coeval and stratigraphically related sections occurring in the northern Apennine region and dated as 5.5 Ma. The 2D textural features of glassy particles (length, width, aspect ratio, grain-size distribution, M
, σ
, SK
, K
and roundness) in both SVT-2 and CAC sections are very similar and also close to the northern section of Camporotondo (Marche region). The outcomes provided here indicate that SVT-2 and CAC sections represent the southernmost distal deposits of the same large eruption that occurred about 5.5 Ma (VRL-5.5). They result from distal fallout of tephra through seawater, occasionally remobilised under low energy and localised conditions, especially in the uppermost part of the CAC section. All the VRL-5.5 rocks are probably related to a very large eruption that occurred in the Carpathian-Pannonian magmatic district. The analytical protocols used in this study can be useful to investigate other ancient volcanic-rich layers, corresponding to lithified tephra.
The compositional variation of clinopyroxene and the partitioning of major elements between clinopyroxene and melt are estimated as a function of the cooling rate. Clinopyroxenes were crystallized ...under variable cooling regimes (15, 9.4, 3, 2.1, and 0.5
°C/min from 1250 down to 1000
°C) and at isothermal conditions of 1000
°C from a basaltic composition at a pressure of 500
MPa under anhydrous and hydrous (H
2O
=
1.3
wt.%) conditions. The clinopyroxene chemistry shows that, as the cooling rate increases, crystals are progressively depleted in Ca, Mg, Fe
2+ and Si and enriched in Na, Fe
3+, Al (mainly Al
IV), and Ti. Di and Hd
versus CaTs and CaFeTs form a continuous binary solid solution characterized by higher amounts of tschermakitic components with increasing cooling rate. Two parameters (DH
=
Di
+
Hd and TE
=
CaTs
+
CaFeTs
+
En) are calculated to describe the effect of cooling rate on the clinopyroxene composition. The variation of DH/TE with increasing cooling rate evidences the kinetic process induced by rapid cooling in basic rocks under hydrous and anhydrous conditions.
Dynamic crystallization conditions affect the partitioning of major elements between clinopyroxene and melt; with increasing cooling rate, the value of crystal–melt partition coefficient departs from that obtained at the isothermal condition. However, in spite of these variations, the values of
cpx–meltKd
Fe–Mg remain almost constant. Therefore, the Fe
2–Mg exchange between clinopyroxene and melt is not suitable to prove the (dis)equilibrium conditions in basaltic cooling magmas, giving rise to possible mismatches in the application of thermobarometers. The results of our study are consistent with that observed at the margin of dikes or in the exterior portions of lavas, where the cooling rate is maximized and disequilibrium compositions of clinopyroxene have been found.
Construction and demolition waste (CDW) from earthquake rubbles was used here as recycled aggregates (RA) in cementitious binders. The materials were sorted in six groups: concrete (CO), natural ...stone (NS), tile (TI), brick (BR), perforated brick (PF) and roof tile (RT). The abundance (wt.%) of crystalline phases in each RA type was determined by X-ray Powder Diffraction (XRPD). Each group of RAs was used alone (100 wt.% of RA) and mixed with quartz-rich virgin aggregates (VA) to prepare 13 types of mortars (12 specimens per type): one reference mortar (RM) with only VA, six recycled aggregate mortars (RAM) and six recycled-plus-virgin aggregate mortars (RVAM). The physical and mechanical properties of aggregates and mortars reflect the type and abundance of crystalline phases in each CDW group. Recycled mortars rich in concrete, natural stones and tiles have better mechanical performance than mortars prepared with recycled bricks, perforated bricks and roof tiles. For each RA, RVAMs have superior mechanical characteristics than the corresponding RAM. Since the type and amount of phases contained in recycled aggregates strongly control the mechanical performance of new construction materials, they should be routinely quantified as reported here, in addition to other physical features (water absorption, density, etc.). The separation of heterogeneous CDW into homogeneous RA groups is necessary for the production of new construction materials with stable and predictable performances to ensure CDW recycling, especially in areas hit by major adverse events, where large amounts of still valuable materials could be used for reconstruction processes.
The dynamics of deep sea explosive eruptions, the dispersion of the pyroclasts, and how submarine eruptions differ from the subaerial ones are still poorly known due to the limited access to sea ...environments. Here, we analyze two ash layers representative of the proximal and distal deposits of two submarine eruptions from a 500 to 800 m deep cones of the Marsili Seamount (Italy). Fall deposits occur at a distance of more than 1.5 km from the vent, while volcanoclastic flows are close to the flanks of the cone. Ash shows textures indicative of poor magma-water interaction and a gas-rich environment. X-ray microtomography data on ash morphology and bubbles, along with gas solubility and ash dispersion models suggest 200-400 m high eruptive columns and a sea current velocity <5 cm/s. In deep sea environments, Strombolian-like eruptions are similar to the subaerial ones provided that a gas cloud occurs around the vent.
The aim of this work was to deeply investigate the structure and properties of electrochemically synthesized silver nanoparticles (AgNPs) through high-resolution techniques such as transmission ...electron microscopy (TEM), scanning electron microscopy (SEM), Zeta Potential measurements, and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). Strong brightness, tendency to generate nanoclusters containing an odd number of atoms, and absence of the free silver ions in solution were observed. The research also highlighted that the chemical and physical properties of the AgNPs seemed to be related to their peculiar oxidative state as suggested by X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRPD) analyses. Finally, the MTT assay tested the low cytotoxicity of the investigated AgNPs.
Seven rock samples were systematically collected from innermost to the outermost portion of a dike outcropping at Mt. Etna volcano. Results show that, from dike core-to-rim, plagioclase, ...clinopyroxene and titanomagnetite show compositional variations due to increasing cooling rate. Plagioclase is progressively enriched in An from innermost to the outermost part of the dike. Similarly, clinopyroxene components En+CaTs+CaFeTs increase, whereas Di+Hd decrease. The Usp content in titanomagnetite also systematically decrease from dike core-to-rim. Partition coefficients and thermometers based on the crystal-liquid exchange reaction indicate that, due to rapid cooling rates at the dike outer portions, early-formed crystal nuclei do not re-equilibrate with the melt. The chemistry of minerals progressively deviates from that of equilibrium; consequently, from dike core-to-rim, mineral compositions resemble those of high-temperature formation. The chemical variations of clinopyroxene and plagioclase in dike samples mirror those obtained from cooling experiments carried out on alkaline basalts. Accordingly, we used an experimental equation based on clinopyroxene compositional variation as a function of cooling rate to determine the cooling conditions experienced by the crystals during dike emplacement. The estimated cooling rates are comparable to those predicted by thermal modeling based on an explicit finite-difference scheme.
► Crystal textures and compositions change as a function of cooling rate from dike core-to-rim. ► Crystals do not re-equilibrate with the melt at the dike rim. ► The composition of crystals experiencing rapid cooling rates suggests high-temperature formation.
In this paper we describe the results obtained with a novel method to prepare depositions of asbestos fibres for toxicological tests
. The technique is based on a micro-dispenser, working as an ...inkjet printer, able to deposit micro-sized droplets from a suspension of fibres in a liquid medium; we used here a highly evaporating liquid (ethanol) to reduce the experimental time, however other solvents could be used. Both the amount and spatial distribution of fibres on the substrate can be controlled by adjusting the parameters of the micro-dispenser such as deposition area, deposition time, uniformity and volume of the deposited liquid. Statistical analysis of images obtained by optical and scanning electron microscopy shows that this technique produces an extremely homogeneous distribution of fibers. Specifically, the number of deposited single fibres is maximized (up to 20 times), a feature that is essential when performing viability tests where agglomerated or untangled fibrous particles need to be avoided.
A Messinian and lithified horizon enriched in volcanic particles with thicknesses of 170–180 cm crops in the Camporotondo (CR) section (Marche, Italy). This volcanic-rich layer (VRL) was investigated ...by field plus mesoscopic observations, X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), bulk composition methods and electron-microprobe analysis (EMPA). The quantitative textural features of volcanic and sedimentary components were determined by 2D image analysis. The lowermost massive 70–80 cm portion is free of sedimentary structure or characterised only by plane-parallel ones, whereas the uppermost one is undulated and cross-laminated. The XRPD and SEM outcomes unveil that the VRL of CR is mainly composed of glassy shards (≥80 area%), a variable amount of sedimentary minerals (<20 area%) and a very low content of magmatic minerals (few area%). The bulk and micro-chemical attributes of volcanic and glassy materials are rhyolitic and almost identical to previous VRLs dated at 5.5 Ma (VRL-5.5). The signatures of immobile elements and the high amount of H2O present in the glass fraction suggest a provenance from a convergent geodynamic setting. The 2D image analysis on SEM observations show that the VRL-5.5 of CR is composed of very fine and sorted (averages of MZ of 5,72 and σi of 0,70), scarcely vesicular, glass shards, with similar long and short size dimensions, shape and roundness. The VRL-5.5 of CR is free of large minerals and fossils. The coupling of mesoscopic and microscopic determinations indicates that the lowermost interval was deposited such as a primary tephra, i.e., fallout pyroclasts sinking in seawater. Instead, the uppermost interval derives from local, low-energy and sin-depositional remobilisation of the same VRL-5.5. The textural attributes of the volcanic fractions, the sedimentological features and the thickness of the VRL at CR correspond to the westward deposit of a still unknown eruption likely occurred at 5.5 Ma.
Vibrational spectroscopies (Fourier Transform Infra Red, FTIR, and Raman) are exceptionally valuable tools for the identification and crystal-chemical study of fibrous minerals, and asbestos ...amphiboles in particular. Raman spectroscopy has been widely applied in toxicological studies and thus a large corpus of reference data on regulated species is found in the literature. However, FTIR spectroscopy has been mostly used in crystal-chemical studies and very few data are found on asbestos amphiboles. This paper is intended to fill this gap. We report new FTIR data collected on a suite of well-characterized samples of the five regulated amphibole species: anthophyllite, amosite, and crocidolite, provided by the Union for International Cancer Control (UICC) Organization, and tremolite and actinolite, from two well-known occurrences. The data from these reference samples have been augmented by results from additional specimens to clarify some aspects of their spectroscopic features. We show that the FTIR spectra in both the OH-stretching region and in the lattice modes region can be effective for rapid identification of the asbestos type.
Radon (
222
Rn) and thoron (
220
Rn) are two isotopes belonging to the noble gas radon (
sensu lato
) that is frequently employed for the geochemical surveillance of active volcanoes. Temperature ...gradients operating at subvolcanic conditions may induce chemical and structural modifications in rock-forming minerals and their related
222
Rn–
220
Rn emissions. Additionally, CO
2
fluxes may also contribute enormously to the transport of radionuclides through the microcracks and pores of subvolcanic rocks. In view of these articulated phenomena, we have experimentally quantified the changes of
220
Rn signal caused by dehydration of a zeolitized tuff exposed to variable CO
2
fluxes. Results indicate that, at low CO
2
fluxes, water molecules and hydroxyl groups adsorbed on the glassy surface of macro- and micropores are physically removed by an intermolecular proton transfer mechanism, leading to an increase of the
220
Rn signal. By contrast, at high CO
2
fluxes,
220
Rn emissions dramatically decrease because of the strong dilution capacity of CO
2
that overprints the advective effect of carrier fluids. We conclude that the sign and magnitude of radon (
sensu lato
) changes observed in volcanic settings depend on the flux rate of carrier fluids and the rival effects between advective transport and radionuclide dilution.
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