We developed a petrologic and geodynamic model for the magma generation of volcanic forma tions in the Tolbachik Dol area. Differences have been found in the evolution of volcanic ejecta and the min eral composition of rocks on Ostryi and Ploskii Tolbachik stratovolcanoes on the one hand and in that of the regional zone of cinder cones on the other. We conclude that the basaltic and the trachybasaltic magmas were generated independently of each other and that these magmas were mixed during the time when central vol canism was giving way to fissure volcanism. The leading process that was responsible for the generation of basaltic and trachybasaltic series was crystallization differentiation, while the compositional variation in the stratovolcano and cinder rocks can be explained by the supply of an alkaline component into the basaltic magma chamber and subsequent accumulation during magma crystallization.

The ionic composition of the liquid phase has a significant influence on the selective flotation of pulps, especially when the water is recycled, and the concentration of the ions can build up to a high level.The control of the ionic composition of the recycled water, which has an important bearing on the selective flotation of Cu--Ni sulfide ores, was considered during the reorganization of the Noril'skii beneficiation plant.The principal ores were chalcopyrite, cubanite, pentlandite and pyrrhotite. Separation was affected by a simple selective flotation process, with sequential production of copper, nickel, and pyrrhotite concentrates.Butyl aerofloat frother SFK was used as the collector for the copper minerals, while butyl xanthate and frother T-80 were used to float the nickel.A recycled water treatment plant, based on a complex multistage system, was essential to deal with the conditions prevailing in the Far North, where the composition of the water varied with the time of the year.During the 7-8 months of winter, the ionic concentration was a maximum, and the pH value was high (9-10.5).Rapid thawing of the ice cover on the reservoir feeders, and the intake of flood water during the spring-summer period, resulted in dilution and an acceleration of the oxidation processes, with a consequential reduction in the salt concentration and the pH value to 7.5-8 (Table I).The main components of the recycled water from the beneficiation plant were sulfur-containing anions, particularly thiosulfate and sulfate ions.For this reason, a study of their effect on the selective flotation of complex Cu--Ni ores was undertaken.Sulfoxide compounds were used as reagent modifiers and their action on the flotation process depends primarily on the pH value.Sulfide and thiosulfate ions have the highest stability at pH values above i0 [i]. The spontaneous formation of significant amounts of the lower oxides of sulfur can be used to improve the selectivity of flotation, since the lower oxides activate the copper sulfides [2,3], but depress the iron sulfides [4].The effect of the oxidation-reduction processes, which take place on the surface of a mineral in the presence of sulfoxide ions, on the flotation of minerals in the absence of a collector at pH 9.5 has been studied potentiometrically.A study of the effect of pH on the potential of a mineral electrode* showed that in the pH range 7-12, the pentlandite electrode potential was positive, while the cubanite, chalcopyrite and pyrrhotite electrode potentials were negative.The pyrrhotite electrode had the greatest negative potential (--i00 to --130 mV) at pH 9-12, which accounted for the poor sorption of anionic collectors by pyrrhotite, in comparison with other sulfides in the ore.The value of the surface charge on pentlandite, the hexagonal form of pyrrhotite, chalcopyrite and cubanite was determined by the concentrations of SO~ 2-and $2032-ions in the pulp, and was the principal factor which determined the sorption of the collector and the flotability of the minerals (Figs. 1-3).Th...

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