Geochemical features of the massive sulfide (Cu) metamorphosed deposit of Arinteiro (Galicia, Spain) and genetic implications

Major and trace element contents in sulfide ores, gangue minerals and rock samples from the Arinteiro deposits hosted in metaophiolites of western Galicia were determined. S isotope ratios of selected sulfides were also analysed. Polymetallic orebodies, represented by abundant pyrrhotite, subordinate chalcopyrite and sphalerite, and rare pyrite, underwent metamorphic recrystallization, probably during the last stage of the Hercynian orogenesis as suggested by the K/Ar radiometric ages ascertained on host rocks (261 275 ± 20 Ma). Recrystallization took place at about 400°C and 5.5 kbar, log aS2 was generally -7 atm or lower, log am was about -30 atm, and pH ranged mainly from 4.4 to 4.9. The Co/Ni values and Se contents of the sulfides are consistent with the inferred volcano-sedimentary origin of the deposit, and 834S (about 0 %0) indicates that the source of S was magmatic. Comparisons of the Arinteiro deposit with similar deposits of corresponding origin and metamorphic rank shows the typical characteristic of the former dominant pyrrhotite and rare pyrite - indicating the greatly reduced conditions of hydrothermal fluids, due to interaction with organic matter.