Chemical and mineralogical data of the metalliferous mineralization from S. Carlo mine (Peloritani mts, Ne Sicily, Italy)

Abstract

The mineralization processes in the Peloritani Belt (Southern Sector of the Calabria- Peloritani Arc) prevalently developed during the Variscan orogenesis producing Pb, Zn, Fe, As, Sb, Cu, Ag, W, etc. polymetalliferous ore-bearing horizons. This paper focuses on the polymetalliferous mineralization recognised in the ancient S. Carlo Mine, which has already been subject of some studies and is part of an important discordant vein deposits system that are widespread in the Mandanici Unit (MaU). This Unit is characterized by a Variscan low-P, polyphasic and plurifacial metamorphic basement, exhibiting a prograde zoning, from chlorite zone of greenschist facies to oligoclase-almandine zone of amphibolite facies. The Variscan main foliation (Fv2) is irregularly cut by mineralized veins of decimetric to metric width. They are also perpendicular to the Alpine mylonitic shear zones of metric thickness developing along the sub-horizontal tectonic contacts between the tectono-stratigraphic units. These vein deposits formed along late-Alpine systems of fractures and faults, after Peloritani nappe emplacement. Minerographic study reveals a metalliferous mineral association mainly composed of tetrahedrite associated with, in order of decreasing abundance, chalcopyrite, bournonite, pentlandite, stromeyerite, arsenopyrite, scheelite, galena, sphalerite, pyrite, bismuthinite, boulangerite, jamesonite, covellite, bornite and argentite. Quartz, siderite and ankerite among non-metalliferous minerals are predominant. This work has been supported by mineralogical studies and chemical analyses carried out by Atomic Absorption and Inductively Coupled Plasma-Mass Spectrometry on powdered and separated samples of minerals. Geochemical data (major and trace elements) have allowed a detailed characterization of the minerals. They have revealed that the most significant minerals with Au contents around 1 ppm are tetrahedrite, sphalerite, chalcopyrite and bournonite. The presence of this noble metal in all minerals is important and shows that the mineralizing event is late and widespread. The Ag content is generally about 2000 ppm in all metalliferous minerals, and is higher than those found in the same minerals of other Peloritani deposits in which this content is around 1000 ppm. Sphalerite and carbonates show very low Ag content. Chalcopyrite, sphalerite, bournonite and tetrahedrite show high contents of Ni, As, Bi. Cd and Mn are concentrated in sphalerite. Fe content in sphalerite is on average > 6%, in agreement with pressure-temperature conditions (pressure from 2 to 3 kbar and temperature from 420 to 550 C).