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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of Local Chemistry and Disorder in Synthetic and Natural α-Al2O3 Materials by X-ray Absorption Near-Edge Structure Spectroscopy (1998)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 31 (1998), S. 890-898 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: X-ray absorption fine spectra at the Al K edge were measured experimentally and calculated theoretically via the multiple-scattering formalism for chemically pure and physically perfect synthetic α-Al2O3 (α-alumina), natural ruby/sapphire (corundum) and a series of artificial corundums produced for technical purposes and used as geochemical standards. The Al K-edge spectra differ, despite the identical coordination (short-range arrangement) assumed by O around Al, and vary slightly in relation to the slightly different chemistries of the materials (substitutional defects) as well as on account of the location taken by foreign atoms in the structural lattices (positional defects). A quantitative treatment of the observed changes is made in terms of short-range distortion of the coordination polyhedron and of medium- to long-range modifications in the overall structure, both induced by substitutions. In some technical corundums, the impurities of admixed β-alumina, where Al is both in fourfold and sixfold coordination, produce another small but detectable effect on Al K edges. Therefore, XAFS spectroscopy proves its potential for both measuring a light element such as Al and detecting minor coordination changes and dilute substitutions (∼1–3 wt% as oxide) of the absorber by other atoms, at least under the favourable conditions occurring in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889898007778
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    Paper (German National Licenses)
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  • 2
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    Mineralogy and textures of riebeckitic asbestos (crocidolite): The role of single versus agglomerated fibres in toxicological experiments (2018)
    Details
    Publication Date: 2021-05-12
    Description: Asbestos may cause adverse effects, but relationship between mineralogy and texture of fibres versus toxicity is still lacking. Toxicological studies can be interpreted and compared only if quantitative features of fibres are determined. Here, riebeckitic ("crocidolite") amphibole fibres were analysed by XRPD, FTIR, SEM-EDS and EMP-WDS; only crystals with stochiometryA□BNa2C(Fe2+2.5Mg0.5)CFe3+2TSi8O22W(OH)2are present in the starting material used for the experiments. Fibres deposited from solutions of 0.1, 1, 10, 25, 50, 75 and 100mg/L were counted by image analysis using SEM images. At 0.1 and 1mg/L the fibres are well separated, whereas between 1 and 10mg/L they start to agglomerate. In-vitro tests performed on fibres deposited at the same mg/L concentrations show that the toxic potential follows a curvilinear increasing trend with a decreasing rate. Since the range of sizes of single fibres and their mineralogy are constant, this decreasing rate can be only attributed to the increasing amount of agglomerated fibres. Hence, single versus agglomerated fibre population is a factor that cannot be neglected in defining the final adverse effects of asbestos. The analytical protocol proposed here is valuable for any aero-dispersed dust, in polluted environments, as well as in the interpretation of experimental studies.
    Description: Published
    Description: 472-485
    Description: 7A. Geofisica per il monitoraggio ambientale e geologia medica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    TH, U, REE MINERALS IN THE GARA ADJEMAMAYE PERALKALINE GRANITE (CENTRAL HOGGAR, ALGERIA) (2012)
    Details
    Publication Date: 2017-04-04
    Description: The Gara Adjemamaye peralkaline granite outcrops in the Egere-Aleksod terrane (central Hoggar). The main facies is a grey to cream heterogranular rock composed of quartz, mesoperthite, sodi-calcic amphibole, sodic pyroxene, annitic biotite, opaques, Fe-Ti oxides, zircon and abundant (Th, U, REE) bearing minerals. The latter are often finely dispersed in veins crossing the rock, suggesting crystallization due to extensive late-stage remobilization. This work represents a contribution to the crystal-chemistry of these rare minerals and the metasomatic mobility of incompatible elements such as Ti, Zr and REE in igneous environments.
    Description: Unpublished
    Description: Tlemcen (Algeria)
    Description: restricted
    Keywords: Th, U, REE ; peralkaline granite ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 4
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    Naturally Occurring Asbestos (NOA) in Granitoid Rocks, A Case Study from Sardinia (Italy) (2019)
    Details
    Publication Date: 2019-12-05
    Description: All six minerals defined as “asbestos” by the existing regulation on asbestos hazard, i.e., actinolite, tremolite, anthophyllite, crocidolite and amosite amphiboles, and the serpentine-group mineral chrysotile are typical constituents of mafic and ultramafic magmatic rocks of ophiolitic sequences. However, little is known about the presence and distribution of naturally occurring asbestos (NOA) in plutonic felsic rocks. The Isadalu magmatic complex outcropping in central Sardinia and belonging to the post-variscan Permian volcanic cycle, is described here as an interesting occurrence of fibrous amphiboles in granitoid rocks. Field work and collected mineralogical/petrological data show that NOA fibers from the Isadalu complex belong compositionally to the actinolite-tremolite series. They were generated by metasomatic growth on pristine magmatic hornblende, at ca. 470 °C at 1 kbar, during sodic-calcic hydrothermal alteration. In terms of environmental hazard, the Isadalu complex represents a high-value case study, since the actinolite-bearing felsic rocks outcrop in a strongly anthropized area. Here, towns with local and regional strategic infrastructures (dams, pipes, hydroelectric power plants, water supply, roads) have been developed since the last century, also using the granitoid asbestos-rich stones. The aim of this study is to demonstrate that NOA and relative hazard are not univocally connected to a restricted typology of rocks. This result should be taken into account in any future work, procedure or regulation defining asbestos occurrences in natural environments
    Description: Published
    Description: id 442
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Synthesis and solid solution in “rubidium richterite”, Rb(NaCa)Mg5 Si8 O22 (OH,F)2 (2020)
    Details
    Publication Date: 2020-03-10
    Description: The OH–F substitution in “synthetic Rb-richterite” has been investigated along the join Rb(NaCa)Mg5Si8O22(OH)2–Rb(NaCa) Mg5Si8O22(F)2. Syntheses were done by conventional hydrothermal techniques (Tuttle-type vessels) at 800 °C, 1 kbar P( H2O). SEM microscopy showed very high yields of acicular to prismatic amphibole crystals up to XF = F/(F + OH) = 0.6. Beyond this value, a micaceous phase and a very fine-grained granular phase were present. Powder X-ray diffraction patterns show a single amphibole phase below XF = 0.6; above XF = 0.6, a distinct peak at d = 12.18 Å indicates the presence of a mica and there is a broad hump starting at ~ 20o 2θ and ~ 15o wide, both features increasing in intensity with increasing XF. Cell dimensions at XF = 0 are compatible with an ideal amphibole composition Rb(NaCa)Mg5Si8O22(OH)2 and evolve with increasing XF up to XF = 0.6, where there is a sharp discontinuity in a, β and V. The infrared OH-stretching spectrum of the OH end-member shows a main band at 3732 cm−1 which is assigned to the local MgMgMg–OH→ Rb arrangement, and a minor band at 3670 cm−1 assigned to the local MgMgMg–OH→ □ arrangement. This latter band indicates a slight departure toward tremolite. Intermediate OH–F compositions show the appearance of a second band at 3718 cm−1, whose intensity is proportional to the F content in the system, in accord with OH−OH and OH–F arrangements across the filled A-site. For XF 〉 0.6, the OH-stretching spectra are complicated by the appearance of two more peaks at 3705 and 3685 cm−1. Additional bands at lower wavenumbers, centered around 3595, 3540 and 3475 cm−1, respectively, are better resolved by collecting the spectra on disks heated at 250 °C to remove the adsorbed moisture in the pellet. Combining the behavior of unit-cell dimensions and the infrared spectra with mass-balance arguments indicates that at high XF values, Na replaces part of the Rb at the A-site in the amphibole and the tremolite component of the amphibole increases, while “Rb tetrasilicic magnesium mica” crystallizes, along with semi-amorphous nanophases. The variation in band intensities as a function of XF indicates that OH and F randomly occupy local pairs of O(3) sites across a (filled) A-site, and that there is no short-range order of OH and F.
    Description: Published
    Description: 759–770
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    A 3D imaging textural characterization of pyroclastic products from the 1538 AD Monte Nuovo eruption (Campi Flegrei, Italy) (2019)
    Details
    Publication Date: 2021-09-08
    Description: The explosive volcanic event of the 1538 AD Monte Nuovo eruption (Volcanic Explosivity Index, VEI = 2) in the Campi Flegrei high-risk caldera (Italy) has a strategic significance in the framework of volcanology and volcanic hazard of caldera-forming magmatic systems. In fact, it represents the last and unique historical eruption of the highly populated Phlegraean restless-caldera, and its precursory and eruptive phenomena are well-known because they were described in detail by contemporaneous eyewitnesses. In this study, a set of samples representative of the complete stratigraphic sequence of the Monte Nuovo eruption was characterized using phase-contrast synchrotron radiation computed microtomography and quantitatively investigated through the development of a new protocol for 3D textural analysis of highly-vesiculated volcanic rocks. Previous studies of products from this eruption are available in the literature, mostly based on 2D imaging techniques, and thus provide a useful data set for comparison. The 3D textural measurements allow us to investigate the subvolcanic processes (mechanisms and timing of magma degassing) that occurred during magma ascent in the conduit for each stage of the eruption and their relationship with the variations in the eruptive style described in the contemporaneous accounts of the eruption. This information is fundamental for the definition of a volcanic eruption scenario for such low-VEI events, often recurrent in the history of the caldera, and is useful both for hazard assessment and emergency planning.
    Description: Published
    Description: 316-331
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
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    Neutron and XRD Single-Crystal Diffraction Study and Vibrational Properties of Whitlockite, the Natural Counterpart of Synthetic Tricalcium Phosphate (2022)
    MDPI
    Details
    Publication Date: 2022-02-28
    Description: A crystal chemical investigation of a natural specimen of whitlockite, ideally Ca9Mg(PO4)6[PO3(OH)], from Palermo Mine (USA), was achieved by means of a combination of electron microprobe analysis (EMPA) in WDS mode, single‐crystal neutron diffraction probe (NDP) and single‐crystal X‐ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The crystal‐chemical characterization resulted in the empirical formula (Ca8.682Na0.274Sr0.045)Σ9.000(Ca0.034□0.996)Σ1.000(Mg0.533Fe2+0.342Mn2+0.062Al0.046)Σ0.983(P1.006O4)6[PO3(OH0.968F0.032)Σ1.000]. Crystal‐structure refinement, in the space group R3c, converged to R1 = 7.12% using 3273 unique reflections from NDP data and to R1 = 2.43% using 2687 unique reflections from XRD data. Unit cell parameters from NDP are a = 10.357(3) Å, c = 37.095(15) Å and V = 3446(2) Å3, and from XRD, the parameters are a = 10.3685(4) Å, c = 37.1444(13) Å and V = 3458.2(3) Å3. NDP results allowed a deeper definition of the hydrogen‐bond system and its relation with the structural unit [PO3(OH)]. The FTIR spectrum is very similar to that of synthetic tricalcium phosphate Ca3(PO4)2 and displays minor band shifts due to slightly different P‐O bond lengths and to the presence of additional elements in the structure. A comparison between whitlockite, isotypic phases from the largest merrillite group, and its synthetic counterpart Ca3(PO4)2 is provided, based on the XRD/NDP and FTIR results.
    Description: Published
    Description: 225
    Description: 1TR. Georisorse
    Description: JCR Journal
    Keywords: whitlockite ; calcium phosphates ; Mineralogy ; crystal chemistry ; spectroscopy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Real-time quantitative detection of styrene in atmosphere in presence of other volatile-organic compounds using a portable device (2022)
    Elsevier
    Details
    Publication Date: 2022-02-14
    Description: Exposure to styrene is a major safety concern in the fibreglass processing industry. This compound is classified by the International Agency for Research on Cancer as a possible human carcinogen. Several types of analytical equipment exist for detecting volatile organic compounds (VOCs) in the atmosphere; however, most of them operate ex-situ or do not provide easy discrimination between different molecules. This work introduces an improved and portable method based on FTIR spectroscopy to analyse toxic gaseous substances in working sites down to a concentration of less than 4 ppm. Styrene and a combination of VOCs typically associated with it in industrial processes, such as acetone, ethanol, xylene and isopropanol, have been used to calibrate and test the methodology. The results demonstrate that the technique offers the possibility to discriminate between different gaseous compounds in the atmosphere with a high degree of confidence and obtain very accurate quantitative information on their concentration, down to the ppm level, even when different VOCs are present in a mixture.
    Description: Published
    Description: 122510
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: Environmental sensors; Infrared spectroscopy; Volatile organic compounds
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
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    Terahertz continuous wave spectroscopy: a portable advanced method for atmospheric gas sensing (2023)
    Optica pg
    Details
    Publication Date: 2023-03-17
    Description: Motivated by the increasing demand to monitor the air-quality, our study proved the feasibility of a new compact and portable experimental approach based on Terahertz (THz) continuous wave high resolution spectroscopy, to detect the presence of the air's contaminants as greenhouse gases (GHG) and volatile organic compounds (VOCs). In this specific work, we first characterized, determining their molar absorption coefficient in the spectral region (0.06-1.2) THz, the pure optical response of the vapor of five VOCs: methanol, ethanol, isopropanol, 1-butanol and 2-butanol. In particular, 1-butanol and 2-butanol are characterized for the first time in literature at THz frequencies. Then we studied the optical response of their mixtures achieved with ambient air and ethanol. The results show that it is possible for a differentiation of single components by describing their spectral absorption in terms of the linear combination of pure compounds absorption. This proof of concept for this apparatus study and set-up paves the way to the use of THz Continuous wave high resolution spectroscopy for the environmental tracking of air pollutants.
    Description: Published
    Description: 19005-19016
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    Hydrothermal genesis and growth of the banded agates from the Allumiere-Tolfa volcanic district (Latium, Italy) (2023)
    Springer
    Details
    Publication Date: 2023-03-13
    Description: In this work, we studied the hydrothermal agates from the Neogene–Quaternary volcanic district of Allumiere-Tolfa, northwest of Rome (Latium, Italy) using a combination of micro-textural, spectroscopic, and geochemical data. The examined sample consists of (1) an outer cristobalite layer deposited during the early stages of growth, (2) a sequence of chalcedonic bands (including i.e., length-fast, zebraic, and minor length-slow chalcedony) with variable moganite content (up to ca. 48 wt%), (3) an inner layer of terminated hyaline quartz crystals. The textures of the various SiO2 phases and their trace element content (Al, Li, B, Ti, Ga, Ge, As), as well as the presence of mineral inclusions (i.e., Fe-oxides and sulfates), is the result of physicochemical fuctuations of SiO2-bearing fuids. Positive correlation between Al and Li, low Al/Li ratio, and low Ti in hyaline quartz points to low-temperature hydrothermal environment. Local enrichment of B and As in chalcedony-rich layers are attributed to pH fuctuations. Analysis of the FT-IR spectra in the principal OH-stretching region (2750–3750 cm−1) shows that the silanol and molecular water signals are directly proportional. Strikingly, combined Raman and FT-IR spectroscopy on the chalcedonic bands reveals an anticorrelation between the moganite content and total water (SiOH+ molH2O) signal. The moganite content is compatible with magmatic-hydrothermal sulfate/alkaline fuids at a temperature of 100–200 °C, whereas the boron-rich chalcedony can be favored by neutral/acidic conditions. The fnal Bambauer quartz growth lamellae testifes diluted SiO 2-bearing solutions at lower temperature. These fndings suggest a genetic scenario dominated by pH fuctuations in the circulating hydrothermal fuid
    Description: Published
    Description: 39
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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