Sublimate deposition from hydrothermal fluids at the Fossa crater - Vulcano, Italy
Garavelli, Anna; Laviano, Rocco; Vurro, Filippο
European Journal of Mineralogy Volume 9 Number 2 (1997), p. 423 - 432
published: Jun 26, 1997
manuscript accepted: Oct 28, 1996
manuscript received: Jun 22, 1995
ArtNo. ESP147050902018, Price: 29.00 €
Abstract Sublimates were sampled at the Fossa crater of Vulcano Island (Sicily, Italy) in June and October 1991. Sampling was carried out by means of silica tubes inserted as deep as possible into those fumarolic vents around which lead and bismuth sulphides and sulphosalts occurred. The main mineralogical phases found within the silica tubes are native sulphur, ammonium tetrafluoroborate, lead and bismuth chlorides, oxychlorides, sulphochlorides, sulphides and sulphosalts. The lead and bismuth mineral assemblage is interpreted as the result of the transport of lead and bismuth as volatile chlorides. Microtextural and microanalytical studies (SEM + EDS) on chloro-sulphides and sulphosalts suggest that the latter were deposited from metastable chlorosulphides through reactions involving gaseous H2S. The absence of chlorosulphides on the ground confirms their metastability. The lack of sulphates in the mineralogical association sampled within the silica tubes is due to the reducing conditions of volcanic fluids.