Origin of fluids associated to gangue minerals in fluorite deposits of Asturias (N Spain)

Barite, carbonates, quartz and sulphides are present as gangue minerals in fluorite deposits from Berbes, La Collada and Villabona (Asturias, N Spain). Calculated 8180 of fluids ranged from -1.1 to +6.7 parts per thousand during barite precipitation, from +2 to +6 parts per thousand during quartz formation and around +3 parts per thousand during carbonate deposition. delta(34)S of barite (+17 to +56 parts per thousand) is explained from sulphate reduction processes (either TSR or BSR) in systems closed to sulphate. delta(34)S of sulphides (+0.6 to -32 parts per thousand) are compatible with these processes. Isotopically light pyrite and marcasite (-7.6 to -32 parts per thousand) would be related to late stage cooling and oxidation of the hydrothermal system. Organic matter derived carbon was an important source of C in the fluids especially in Villabona (delta(13)C = -14.8 to 3.2 parts per thousand in calcites and from -7.9 to -2.2 parts per thousand in dolomites).