Термодинамическая модель окисления сульфидных руд месторождения Новоширокинское (Восточное Забайкалье)

The thermodynamic model of the oxidation of sulfide ores from the Novo-Shirokinsky gold-polymetallic deposit in Eastern Transbaikalia was performed. Sulfide ores are composed of sulfides and sulfosalts. The main ore minerals are galena, sphalerite, pyrite; secondary - chalcopyrite, hematite, covellite, malachite, smithsonite, rare antimony sulfosalts (burnonite, polibazite, boulangerite), freybergite, gold, bornite, chal-cocite, anglesite, aikinite, tetrahedrite. The peculiarity of sulfides and sulfosalts is their antimony. The task of calculating thermodynamic equilibrium for the system "solid phases - water solution - gas phase" at T = 25°С, P = 1 atm was formed in the "Selector" PC. The solid phase is represented by 100 g of ore-bearing rock with the chemical composition: (wt. %) -S (30), Si (14), Al (1.5), Pb (3), Zn (0.7), Fe (25 ), Cu (6), Cd (0.01), As (0.5), Sb (3), Bi (0.1), Ag (0.1), Mg (0.4), Ca (0.2), K (0.7), Na (0.04), Mn (0.1) and with impurity elements (ppm) -Au (20), In (14), U (0.1). The liquid phase was determined in the amount of 1 kg H2O. The system was considered open to the gas phase with the composition of the modern earth atmosphere. The simulation results showed that the oxidation of sulfide ores in the presence of water leads to the formation of a strongly acidic sulfate solution, in which silicate anions, phosphoric acid, compounds of potassium, sodium, iron, manganese, copper, cadmium, lead, silver, gold and indium. The bulk of the equilibrium with a solution of minerals is represented by hydroxosulfates of iron and aluminum; in a smaller amount, zinc and calcium sulfates are formed. The class of phosphate minerals is represented by strengite, zairite and ra-nunculite. The only mineral of the class of oxides present at equilibrium is tripuhyite. The transformation of alumosilicate minerals leads to the formation of aluminite, a part of aluminum is transferred to the composition of uranyl hydroxophosphate - ranunculite. Arsenic, which is part of the primary minerals, is completely oxidized to form arsenate Mg 3 (AsO 4 ) 2 -8H 2 O. Silver and indium are present in the solution in sulfate forms, gold in the form of a hydroxo complex. Carbon dioxide from the atmosphere forms soluble carbonate complexes of copper, cadmium and lead. The exclusion of carbon from the model system leads to the appearance at equilibrium of Pb-jarosite (Pb 05 Fe 3 (SO 4 ) 2 (OH) 6 ), biverite (Pb 094 Fe 176 Cu 112 (SO 4 ) 2 (OH) 6 ), and chalcanthite. The conducted modeling of the formation of mineral associations as a whole showed the correspondence of the model and natural mineral composition of sulfide oxidation products. Nevertheless, to improve the thermodynamic calculations, additional data are needed for standard Gibbs potentials of hypergene antimony and arsenic minerals.