BEHAVIOR OF MACROCOMPONENTS DURING FORMATION OF ZONAL SULFIDE ORE BASED ON EXPERIMENT ON DIRECTIONAL CRYSTALLIZATION OF Cu-Fe-Ni-S MELT
E.F. Sinyakova1, D.A. Ulybin1,2,3, K.A. Kokh1, I.A. Kuzmin1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
3Novosibirsk State University, Novosibirsk, Russia
Keywords: Cu-Fe-Ni-S system, phase equilibrium, zonality, fractional crystallization
Abstract
The quasi-equilibrium directional crystallization method to model a new type of zoning in the Cu-Fe-Ni-S system was applied. A melt is crystallized with the following composition (in at.%): 14.00 Cu, 30.00 Fe, 4.00 Ni, 51.00 S, and 0.1 each of Pt, Pd, Ag, Au, As, Te, Bi, Pb, Se, and Sn. We use optical and electron microscopy, micro-X-ray spectral analysis, differential thermal analysis, and powder diffraction to study the composition and structure of the ingot. Based on the results of measuring the average solid phase composition, the distribution curves of macrocomponents in the ingot have been constructed in the range of g from 0 to 0.81 ( g is the fraction of crystallized melt). The variations in the melt composition and distribution coefficients between solid phases and the melt in directional crystallization have also been calculated. The obtained sample consists of three primary zones: monosulfide solid solution with the composition ranging from (Fe0.75Ni0.10Cu0.06)0.91S to (Fe0.69Ni0.15Cu0.09)0.93S (Mss) in Zone I and two intermediate solid solutions: ~ (Fe0.57Ni0.03Cu0.45)1.05S (Iss1) in Zone II and (Fe0.46Ni0.06Cu0.52)1.05S (Iss2) in Zone III. The peritectic character of the crystallization of Iss1 and Iss2 from the melt has been established. The trajectories of the melt and solid phase compositions and series of conodes have been plotted for Mss and Iss1 on the phase diagram of the Cu-Fe-Ni-S system. Secondary zonality is described by the following sequence of phases: Pyh 1C + Pyh 3C + Icb + Ccp/Ccp + Iss + Fe-Pn, Sgk/Ccp + Ni-Pn + NiS + Bn (Pyh - hexagonal pyrrhotite, Icb - isocubanite, Ccp - chalcopyrite, Pn - pentlandite, Sgk - sugakiite, Bn - bornite) and belongs to the high-sulfur pyrrhotite + cubanite-chalcopyrite type of ore body zonation.
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