Geochemical and mineralogical features of the polymetallic deposit from Alì (NE Sicily, Italy)

Carmelo Saccà, Domenica Saccà, Preziosa Nucera, Anna De Fazio, Daniele D'Urso


The mineralization processes in the Peloritani Belt (Southern Sector of the Calabria- Peloritani Arc), related to Pre-Variscan intracontinental rifting, produced sedextype Pb, Zn, F (Ag), Cu, W (As, Sb) ores. This paper focuses on the metalliferous stratabound mineralization outcropping in the Al`? area (Tripi locality). It is part of sulphide ores, concordant with the regional foliation of the hosting unit (Fv2), very widespread in the Mandanici Unit (MaU). This unit is characterized by a Variscan low-P, polyphasic and plurifacial metamorphic overprint involving the basement. This metamorphic overprint exhibits a prograde zoning, from a chlorite zone of greenschist facies to an oligoclasealmandine zone of amphibolite facies. The metalliferous mineral association is formed by galena, sphalerite, pyrite, chalcopyrite, arsenopyrite and covellite. Quartz and fluorite among non-metalliferous minerals are predominant. Some minerals like quartz, fluorite, galena, sphalerite and pyrite are present in two generations, the second of which can be related to intense hydrothermal activity involving the whole Peloritani Belt. Trace-element contents of sulphide ores detected by Atomic Absorption and Inductively Coupled Plasma-Mass Spectrometry on powdered and selected samples of minerals have been determined. Major elements have been analyzed by Scanning Electron Microscopy. The Ag content is quite high in galena, relative to the same mineral of other Peloritani deposits in which this content is around 1000 ppm. Galena shows a high content of Sb (¯x= 621) and lower values of Cd (¯x=132) and Cu (¯x=108) whereas in sphalerite the Sb content (¯x= 134) is lower than Cd (¯x= 1118) and Cu (¯x= 1127). Mn is scarcely present in sphalerite, while galena shows higher contents. Fe content in sphalerite is about 6%, in agreement with Pressure-Temperature conditions of the Unit.

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