The aim of this paper is to analyze and compare the mineralogy and geochemistry of copper-zinc sulfide ores from the Logachev-2 and Rainbow hydrothermal fields of the Mid-Atlantic Ridge MAR, confined to serpentinite protrusions. It was found that the ZnFe and Cu, FeZn sulfides had been deposited in black smokers pipes almost simultaneously from intermittently flowing, nonequilibrium H 2 S-low solutions of different temperatures. The Pb isotope composition confirmed that the source of lead had been the deep oceanic crust. The ores of the Rainbow Field contain 20-fold more Co than the ores restricted to the basalts and show a high ratio of Co/Ni = 46. The Rainbow ore is enriched in heavy 34S isotope d34Sav = 10 because of the constant flow of cold sea water into the subsurface zone of the hydrothermal system. The ore of the Logachev-2 field is 8 times higher in gold compared to the other MAR regions. The sulfide ores of the Rainbow and Logachev-2 fields have no analogues among the MAR ore occurrences in terms of the enrichment in useful components Zn, Cd, Co, and Au.
mineralogy, geochemistry, ocean-floor hydrothermal fields, serpentinite protrusions.
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