1,721,007 research outputs found
Studio in situ del comportamento termico di miche triottaedriche del Mt. Vulture mediante diffrazione X da cristallo singolo.
No full textMineralizations of the Sila Massif (Calabria, southern Italy): The case study of the Zn-Pb ore deposit of Longobucco
No full textAlthough the mineral deposits of the Longobucco area in the Sila Massif (Calabria, southern Italy) are historically known as metal exploitation sites since ancient times, scientific interest in their study has only recently been renewed (Fregola et al., 2023a). In particular, a detailed mineralogical characterization using modern methodologies and framed in an updated geological context, would help to decipher their genesis. We have collected samples of the mineralized bodies outcropping along a fault zone crosscutting monzodiorites at the “Torrente La Manna” site in the Longobucco area, where Vighi (1953) first observed a sphalerite-galena- pyrite-quartz-calcite mineral association. We have characterized such minerals using optical microscopy, scanning electron microscopy (SEM), electron probe microanalyses (EPMA), and micro-Raman spectroscopy. Sphalerite is the dominant polymetallic mineral, showing color and chemical zoning, and can be used as fingerprint to differentiate the evolution stages of the mineralized deposit; noteworthy its mineralogical characterization is presented in a separate contribution to this congress (Fregola et al., 2023b; session P.40). Our reconstructed paragenetic sequence comprises almost five growth stages. Early minerals include a light- colored Fe-poor sphalerite-I, followed by a darker Fe-richer sphalerite-II formed in association to euhedral quartz-I crystals. The latter show color and chemical zoning of Al, Na, K, Ca. Moreover, we have observed a Mn-rich (1.19±0.03 to 0.49±0.02 wt%) and Mg-poor (up to 0.08±0.01 wt%) calcite, partly hosting REE- fluorcarbonates. The latter minerals are reported here for the first time in the Longobucco area, and consist of synchysite, with 20 to 60 μm grain size, and total REE (Ce, La, Y, Nd, Sm, Pr, Gd, Dy) concentrations ranging between 42.64 and 2.40 wt%. Late stages minerals comprise sphalerite-III, quartz-II, pyrite, and Ag- free galena with low Sb-content (up to 0.09±0.03 wt%).
Fregola, R.A., Ciccolella, A., Festa, V., Ruggieri, G., Schingaro, E., Tursi, F., & Ventruti, G. (2023a) - Review of Polymetallic Mineralization in the Sila and Serre Massifs (Calabria, Southern Italy). Minerals, 13(3), 439. https://doi.org/10.3390/min13030439
Fregola R.A., Ciccolella A., Ruggieri G., Ventruti G., Mesto E. & Schingaro E. (2023b) – Mineralogical characterization of zoned sphalerite from polymetallic mineralization of the Sila Massif (Calabria, Southern Italy): The Longobucco case study. Congresso SGI-SIMP, “The Geoscience paradigm: Resources, Risks and future perspectives”. Potenza, 19-21 sept. 2023, Abstract Book, p. .
Vighi L. (1953) Sulla geologia e sulle mineralizzazioni metallifere della regione di Longobucco in Calabria. Mem. e Note Ist. Geol. Appl. Napoli, 5, 3–61
Mineralogical Characterization of Zoned Sphalerite from the Zn-Pb Ore Deposit of Longobucco (Sila Massif, Calabria, Southern Italy)
No full textPolymetallic ore deposits of the Sila Massif were subjected to raw metals exploitation starting from the Bronze and Iron ages. In spite of this, the scientific literature on their mineralogical characterization is not comprehensive and mostly out-of-date, as recently reported (Fregola et al., 2023). A mineral chemistry study with special focus on some phases could certainly contribute to decipher the origin of these mineral deposits. In this contribution, we present a mineralogical characterization of zoned sphalerite samples collected from the mineralized bodies outcropping along a fault zone cross-cutting monzodiorites at the “Torrente La Manna” site in the Longobucco area (Sila Massif, Calabria). In a separate contribution, we also present results on the whole mineralogical association of this mineralized site, including paragenetic considerations (Ciccolella et al., 2023; Session P.74). Sphalerite from Longobucco has been analysed by optical microscopy, micro-Raman spectroscopy, scanning electron microscopy (SEM), electron probe micro analyses (EPMA), and single crystal X-ray diffraction. Chemical micro-analyses revealed that sphalerite contains minor to trace amounts of Fe (0.803±0.021 to 9.550±0.064 wt%), Cd (up to 0.685±0.020 wt%), Hg (0.176±0.033 to 0.461±0.039 wt%), Cu (up to 0.454±0.011 wt%), and Co (up to 0.023±0.005 wt%). Sphalerite from Longobucco systematically shows colour and chemical zoning, with darker coloured growth bands due to enriched Fe-content. Sector zoning of Cd is also observed. The optical and paragenetic study allowed us to associate the different colour zones to different growth episodes. In particular, sphalerite of the first generation (sphalerite-I) is lighter coloured and Fe-poorer, with respect to the darker and Fe-richer one of the second generation (sphalerite-II). Micro-Raman spectroscopy and single crystal X-ray diffraction were performed on the different colour zones. In particular, Raman spectra show that number, position and relative intensity of the bands in the spectral range 250-400 cm-1 are related to the colour zoning and Fe-content of the sphalerite growth bands. These results are in good agreement with the previous literature (Buzatu et al., 2013). Preliminary single crystal X-ray diffraction data detected a slight difference between the lattice parameters of the lighter sphalerite-I (5.4140 ± 0.0009 Å) and of the darker sphalerite-II (5.4194 ± 0.0007 Å). Based on the relationship between Fe-content and cell parameters found in synthetic FexZn(1-x)S solid solutions (Osadchii & Gorbaty, 2010), our results would correspond to a difference from 0.06 to 0.15 mole fraction of FeS. Zoned sphalerite indicates a variation in the composition of the mineralizing fluid(s) during the geological history of the Longobucco ore deposit.
Buzatu A., Buzgar N., Damian G., Vasilache V. & Apopei A.I. (2013) – The determination of the Fe content in natural sphalerites by means of Raman spectroscopy. Vibrational Spectroscopy 68, 220-224. https://doi.org/10.1016/j.vibspec.2013.08.007
Ciccolella A., Fregola R.A., Ruggieri G., Tursi F., Festa V., Ventruti G. & Schingaro E. (2023) - Polymetallic mineral deposits of the Sila Massif (Calabria, southern Italy): The case study of Longobucco. Congresso SGI-SIMP, “The Geoscience paradigm: Resources, Risks and future perspectives”. Potenza, 19-21 sept. 2023, Abstract Book, p. .
Fregola, R.A., Ciccolella, A., Festa, V., Ruggieri, G., Schingaro, E., Tursi, F., & Ventruti, G. (2023) - Review of Polymetallic Mineralization in the Sila and Serre Massifs (Calabria, Southern Italy). Minerals, 13(3), 439. https://doi.org/10.3390/min13030439
Osadchii E.G. & Gorbaty Y.E. (2010) - Raman spectra and unit cell parameters of sphalerite solid solutions (FexZn1-xS). Geochim. Cosmochim Acta, 74, 568-573. https://doi.org/10.1016/j.gca.2009.10.02
The structure of metahohmannite, Fe-2(3+)[O(SO4)(2)]center dot 4H(2)O, by in situ synchrotron powder diffraction
No full textMetahohmannite, Fe-2(3+)[O(SO4)(2)].4H(2)O, is a hydrated sulfate of ferric iron that occurs in sulfate deposits in the desert areas of Northern Chile. The compound used for this study was obtained as a dehydration product of hohmannite, Fe-2(3+)[O(SO4)(2)].(4+4)H2O. Intensities for the structure analysis were collected from a powdered sample using in situ synchrotron X-ray powder diffraction at ESRF (Grenoble, France). The structure was solved ab initio by profile deconvolution and the application of standard Patterson and difference Fourier maps. The structure was refined to R-p = 5.46% using the Rietveld method. Metahohmannite crystallizes in the triclinic system, space group P (1) over bar with unit-cell parameters a = 7.3484(5) Angstrom, b = 9.7710(6) Angstrom, c = 7.1521(5) Angstrom, alpha = 91.684(5)degrees, beta = 98.523 (5), gamma = 86.390(5)degrees, and Z = 2. The structure consists of four Fe3+ octahedra and four sulfate tetrahedra, which share vertices and edges to form a complex building block of Fe-4(3+)[O-2(SO4)(4)].8H(2)O composition. Such blocks are connected to form chains running parallel to the c axis. A complicated system of hydrogen bonds connects adjacent chains into a three-dimensional network. Finally, the crystal structures of metahohmannite, hohmannite, and amarantite are compared and the geometrical features discussed in detail
Local geometry and octahedral site distortion around Fe3+ and Ti4+ in trioctahedral micas
No full textOH-FREE FLUORO-PHLOGOPITE FROM BIANCAVILLA (SICILY, ITALY):CRYSTAL CHEMISTRY, STRUCTURE REFINEMENT AND SUBSTITUTIONAL MECHANISMS.
No full textTime evolution of Fe-oxydation/deprotonation process in Fe-rich phlogopite under isothermal conditions
No full textKinetics of Fe-oxydation/deprotonation process in Fe-rich phlogopite under isothermal conditions
No full textThe kinetics of the Fe-oxidation/deprotonation process in a natural Fe-rich phlogopite from Mt.
Vulture (Potenza, Italy) was studied under isothermal conditions by in situ high-temperature singlecrystal
X-ray diffraction. Isothermal annealing experiments were performed at five temperatures in
the range 640–750 °C on five crystals with similar chemical composition and lattice parameters. The
Fe-oxidation/deprotonation process at high temperature occurs with a reduction of unit-cell parameters
and cell volume. The changes in unit-cell parameters measured at high temperature and during cooling
show that the same degree of Fe-oxidation/deprotonation process was achieved at all temperatures.
Changes in unit-cell parameters with temperature and time show that the kinetics of Fe-oxidation/
deprotonation in phlogopite follows an exponential law, and the temperature dependence follows the
Arrhenius relation. A kinetic analysis was performed and good agreement was obtained with the onedimensional
diffusion model. An apparent activation energy of 195(4) kJ/mol was determined
Multimethodic approach to the crystal chemistry of Ti-rich phlogopites from Mt. Vulture (Potenza, Italy)
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