Chemical reactions and conditions of mineral formation at tailings storage facilities of the Russian Far East

Cassiterite-sulfide and polymetallic deposits of the Far Eastern Region (FER) were mined by both openpit and underground methods. This resulted in the emerging numerous mine workings and tailings storage facilities (TSFs) (abandoned without reclamation in latest decades) and the formation of mining technogenic mineralogical systems. Sulfide component of minerals in the mining technogenic system is subjected to hypergenic and technogenic processes (oxidation and hydrolysis reactions). As a result, highly concentrated technogenic solutions are formed, from which minerals of various classes precipitate. In this connection the purpose of this study was formulated as follows: to show the possibility of crystallization of technogenic minerals from micropore technogenic solutions. In achieving this goal the following tasks were solved: to demonstrate the possible reactions of oxidation and hydrolysis of technogenic minerals at the tailings storage facilities; to identify Eh-pH parameters of their precipitation from highly concentrated solutions; to determine their possible associations. The studies involved field observations and computations with the use of “Selector” software package. The study findings allow demonstrating possible chemical reactions and physico-chemical conditions of mineral formation for the following elements: Fe, Cu, Pb, Zn, Sb, Mg, Al, and Ca, including the following classes of minerals: oxides and hydroxides, sulfates, carbonates, arsenates and silicates. The paper presented for the first time the crystallization reactions of secondary minerals (37 ones) and their physico-chemical conditions. It was found that secondary minerals: jarosite, pitticite, siderite, tenorite, poznyakite, antlerite and ktenasite crystallize in the interval of positive temperatures, while scorodite, chalcantite, broshantite, cerussite, starkeyite, epsomite and rostite originate in cryogenic conditions (below 0 oC). All other minerals, the possibility of precipitation of which was shown in the paper, crystallized in the whole considered temperature interval, from −25 oС to +45 oС. Field studies and modeling data on formation of technogenic waters (solutions) and crystallization of secondary minerals on the surface of and inside tailings at the tailings storage facilities of the Far East showed high intensity of technogenic processes. Since the tailings storage facilities were not reclaimed, the process of environmental pollution, including the hydrosphere, would last for many decades.