Soigas investigations over sulphide ore-bearing fractures -the Fontalc1naldo case study and Niccioleta mining district - southern Tuscany, Italy)

The application of soil-gas analysis to sulphide expl oration has been eval uated at Fntlcinald ? .(southern Tuscany, Boccheggiano­ Niccioleta mmmg district). Samples were collected for He, Rn and C02 analysis and compared with deep sulphide-bearing fractures identified using borehole and geophysical data. The selected gases were chosen because they are proven fault tracers. In addition C02 has the added benefit that it can also give indirect information on the presence of buried sulphide depos its, as sulphide mineral oxidation produces sulphuric acid which in turn reacts with host-rock carbonate mineral ; to for � carbon dixide. Elevated He, 222 Rn and C02 concentratiOns have been found over fault and fracture systems defined on the basis of geological a.nd g.eophysical mapping; further N-S trending lmetwns have also been highlighted, including a possible northward extension of the Boccheggiano Fault. The surveys also indicated systematic soil­ gas anomalies related to mineral occurrences, with the most consistent patterns (i.e. elevated C02 values) occurring over the main sulphide orebodies present in the area. The present research