Polymetallic 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 In spite of this, the scientific literature on their mineralogical characterization is not comprehensive and mostly out-of-date, as recently reported (Fregola et al., 2023).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.2009.10.022
Mineralogical Characterization of Zoned Sphalerite from the Zn-Pb Ore Deposit of Longobucco (Sila Massif, Calabria, Southern Italy)
Fregola R. A.;Ciccolella A.;Ventruti G.;Mesto E.;Schingaro E.
2023-01-01
Abstract
Polymetallic 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.2009.10.022I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
