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Silius vein system, South Sardinia Province, Sardinia, Italyi

Regional Level Types
Silius vein system	Vein
South Sardinia Province	Province
Sardinia	Autonomous Region
Italy	Country

Fluorite-baryte vein system (with Pb-Zn sulphides) which comprises the following occurrences (shafts): Genna Tres Montis, Pozzo Centrale, and Muscadroxiu (Silius municipal territory), and Acqua Frida (San Basilio municipal territory).

The Silius vein system crops out discontinuously for 2-3 km along a NE-SW strike, between the Acqua Frida area (39°30’46’’N; 9°15’05’’E), the Muscadroxiu shaft (39°31’00’’N-9°15’18’’E) and the Genna Tres Montis shaft (39°31’3’’N-9°16’00’’E), at an elevation ranging between 600 and 700 m a.s.l. At the 400 m level, the veins reach a maximum length of 4 km. The Silius veins have been mined from the surface (around 600 m a.s.l.) down to 200 m a.s.l., and explored to 100 m a.s.l. The system consists of two main veins, called "San Giorgio" and "San Giuseppe", which have an almost vertical dip (about 75°), and a strike of N-045-E along the main sector Acqua Frida - Genna Tres Montis, and N-065-E northeastward from Genna Tres Montis. These two veins are almost parallel in the topmost levels, with a spacing of 70 m on average, but coalesce at a depth of 350 m a.s.l. in the NE sector, and at a depth of 450 m a.s.l. in the SW sector of the mineralized area. The San Giorgio vein was the first to be formed, and was displaced and brecciated by the San Giuseppe vein. The San Giorgio vein contains bands of chalcedony, pink fluorite, baryte, and calcite. The San Giuseppe vein is also banded and shows several generations of fluorite, carbonate minerals (mainly sparry calcite), galena, and quartz. The width of the veins ranges between 7-8 m in outcrop and 15-20 m in depth, where they are interconnected. The upper part of the vein system contains fluorite, baryte, and galena with grades of 35%, 10% and 3%, respectively, whereas in the lower zones the amount of baryte decreases dramatically and the fluorite and galena grades can reach 50% and 6%, respectively (Natale, 1969; Mondillo et al., 2016; Mondillo et al., 2017).

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