ABSTRACT
Cu-Zn massive sulphide deposit of a new serpentinite-related type of black smokers has been studied at the Mid Atlantic near Azores - Rainbow hydrothermal field (36 °14′N MAR). Ores enriched in Cu, Zn, Co and Ni were deposited by submarine moderately saline hydrothermal fluids at 315-370°C. Large hydrothermal mounds are composed of abundant sphalerite, pyrrhotite and minerals of Cu-Fe-S system (chalcopyrite, isocubanite, bornite, digenite, chalcocite, covellite). Rare ore minerals such as magnetite, Copentlandite, millerite, troilite, wurtzite, stannite, gallite were found in active and inactive sulphide chimneys. Results of a fluid inclusion and He isotope study are discussed.
