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Article

Factors Controlling Hydrothermal Nickel and Cobalt Mineralization—Some Suggestions from Historical Ore Deposits in Italy

1
Dipartimento di Scienze della Terra, Università degli Studi di Milano, 20133 Milano, Italy
2
Dipartimento di Scienze della Terra, Università degli Studi di Torino, 10125 Torino, Italy
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Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, 09124 Cagliari, Italy
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IGG-CNR, UOS Firenze, 50121 Firenze, Italy
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Dipartimento di Scienze della Terra, Università degli Studi di Firenze, 50121 Firenze, Italy
6
Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari, 07100 Sassari, Italy
*
Authors to whom correspondence should be addressed.
Minerals 2019, 9(7), 429; https://doi.org/10.3390/min9070429
Received: 9 June 2019 / Revised: 9 July 2019 / Accepted: 10 July 2019 / Published: 12 July 2019
(This article belongs to the Special Issue High-Tech Critical Metals: Evaluation and Deposit Models)
We compare three poorly known, historical Ni–Co-bearing hydrothermal deposits in different geological settings in Italy: The Ni–Co–As–Sb–Au-bearing Arburese vein system (SW Sardinia), the Co–Ni–As-rich Usseglio vein system (Piedmont), and the small Cu–Ag–Co–Ni–Pb–Te–Se stockwork at Piazza (Liguria). These deposits share various (mineralogical, chemical, thermal, and stable isotopic) similarities to the Five Element Vein-type ores but only the first two were economic for Co–Ni. The Sardinian Ni-rich veins occur in Paleozoic basement near two Variscan plutons. Like the Co-rich Usseglio vein system, the uneconomic Piazza deposit is hosted in an ophiolite setting anomalous for Co. The Sardinian and Usseglio deposits share a polyphasic assemblage with Ni–Co–As–Sb–Bi followed by Ag-base metal sulfides, in siderite-rich gangue, whereas Piazza shows As-free, Ag–Pb–Te–Se-bearing Co–Ni–Cu sulfides, in prehnite–chlorite gangue. Fluid inclusions indicated Co–Ni arsenide precipitation at ≈170 °C for Usseglio, whereas for the Sardinian system late sulfide deposition occurred within the 52–126 °C range. Ore fluids in both systems are NaCl-CaCl2-bearing basinal brines. The chlorite geothermometer at Piazza provides the range of 200–280 °C for ore deposition from CO2-poor fluids. Enrichments in Se and negative δ13C in carbonates suggest interaction with carbonaceous shales. These deposits involve issues about source rocks, controls on Co/Ni and possible role of arsenic and carbonate components towards economic mineralization. View Full-Text
Keywords: Ni–Co arsenides; five element vein-type deposits; fluid inclusions; basinal brines; carbonates; chlorite geothermometer Ni–Co arsenides; five element vein-type deposits; fluid inclusions; basinal brines; carbonates; chlorite geothermometer
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MDPI and ACS Style

Moroni, M.; Rossetti, P.; Naitza, S.; Magnani, L.; Ruggieri, G.; Aquino, A.; Tartarotti, P.; Franklin, A.; Ferrari, E.; Castelli, D.; Oggiano, G.; Secchi, F. Factors Controlling Hydrothermal Nickel and Cobalt Mineralization—Some Suggestions from Historical Ore Deposits in Italy. Minerals 2019, 9, 429. https://doi.org/10.3390/min9070429

AMA Style

Moroni M, Rossetti P, Naitza S, Magnani L, Ruggieri G, Aquino A, Tartarotti P, Franklin A, Ferrari E, Castelli D, Oggiano G, Secchi F. Factors Controlling Hydrothermal Nickel and Cobalt Mineralization—Some Suggestions from Historical Ore Deposits in Italy. Minerals. 2019; 9(7):429. https://doi.org/10.3390/min9070429

Chicago/Turabian Style

Moroni, Marilena, Piergiorgio Rossetti, Stefano Naitza, Lorenzo Magnani, Giovanni Ruggieri, Andrea Aquino, Paola Tartarotti, Andrea Franklin, Elena Ferrari, Daniele Castelli, Giacomo Oggiano, and Francesco Secchi. 2019. "Factors Controlling Hydrothermal Nickel and Cobalt Mineralization—Some Suggestions from Historical Ore Deposits in Italy" Minerals 9, no. 7: 429. https://doi.org/10.3390/min9070429

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