Enrichment of massive sulfdes from the Semenov hydrothermal cluster (Mid-Atlantic ridge) in barite: a result of E-MORB involvement and magmatic contribution

The paper reviews and compares the barite fndings in hydrothermal felds of the mid-oceanic ridges. The genetic signifcance of barite is considered for the Semenov hydrothermal sulfde cluster associated with an oceanic core complex (OCC) at 13°30? N of the Mid-Atlantic Ridge. Massive sulfdes of the Semenov-1, -3, and -4 felds are enriched in barite (up to 20 vol. %) and therefore Ba (up to 4.12 wt. %). The presence of a signifcant amount of barite and a high Ba content of massive sulfdes of the OCC-related felds link their formation with E-MORBs. Magmartic contribution for the formation of massive sulfdes from some Semenov felds is supported by negative values of S isotopic composition of sulfdes associated with barite, the presence of magmatic gases (CO2 and SO2) in Raman spectra of fuid inclusions in barite and the results of physicochemical modeling, which indicate the formation of barite-sulfde assemblage upon the interaction of E-MORBs, seawater, and magmatic gas. The results of modeling of the system with felsic rocks show that oceanic plagiogranites from OCC structure could be an additional supplier of Ba.