Prediction of the effects of acid mine drainage on variations in the hydrogeochemical environment at sulfide-bearing ore deposits

Abstract

Modeling of interactions in the water-rock-CO 2 -O 2 systems was performed for rocks from dif ferent sites within a sulfide bearing ore deposit A. The physicochemical computer modeling showed that acid mine drainage is controlled by the rates of interaction between the components of the system. The reason for the generation of acid mine drainage is that the dissolution rate of aluminosilicate minerals present in the rocks is lower than the rate of sulfide oxidation. The transition from a low to a high water exchange regime resulted in the burst release of pollutants.A gold-kaolinite (dickite)-quartz assemblage is dominant in the upper portions of the deposit. Minor minerals are calcite, sericite, adularia, and illite. The ore minerals make up 1-3% of the ore and include pyrite, minor galena and sphalerite, and less common chalcopyrite. The oxidized zone consists (wt %) of all ore minerals (0.2), carbonates (1.3), dickite (15), feld spar (30), quartz (34), and other minerals (~20).Despite their broad similarity, these two types of assemblages differ in the concentrations of minor and trace components; e.g., the gold-chlorite-sulfidequartz assemblage is enriched in Pb (by a factor of 3-4), Zn (10-15), As (3-4), Cu (5), and Sb (2-3). The aver age concentrations of Se in ores composed of different mineral assemblages is about 30 ppm. Commercial mineralization consists of electrum, low grade native gold, native silver, and silver sulfosalts: acanthite Ag 2 S, pyrargyrite Ag 3 SbS 3 , polybasite (Ag,Cu) 16 Sb 2 S 11 , freibergite (Ag,Cu) 12 Sb 4 S 13 , naumannite Ag 2 Se, and aguilarite Ag 4 SeS. Electrum is predominant, low grade native gold is present in minor amounts, while the other minerals occur as rare and very rare grains.Accompanying ore minerals include pyrite, sphaler ite, galena, and minor chalcopyrite. These minerals are responsible for elevated sulfide contents of the goldchlorite-sulfide-quartz ores. Sulfide mineralization is distributed nonuniformly and occurs as pockets in gangue quartz or in the host rocks. Other ore minerals (magnetite, pyrrhotite, arsenopyrite, marcasite, bornite, and Ag minerals) are present in minor amounts (less than 1% of vein material).The main rock forming minerals are quartz (from 60 to 99 vol % of the ore), kaolinite group clay minerals (up to 6.0-9.0 vol %), chlorite group minerals (up to 12.0 vol %), sericite and illite (up to 6.0-25.0 vol %), and K feldspar (1.0-30 vol %). Quartz, chlorite, and kaolinite are the dominant minerals of commercial associations, while sericite, illite, and K feldspar occur mostly as relic fragments of metasomatites.Accompanying components in the ores include Se (22-170 ppm), Pb (0.09-1.66%) as galena, and Zn (0.13-2.09%) as sphalerite. Arsenic, as one of the mon itored elements, is present in minor amounts (from 0.02 to 1.61%). Higher tenors of Pb and Zn, as well as Se and Cd may be locally observed in the ores.The following mineral compositions were obtained for a bulk ore sample from this deposit (oxidized and primary ore, respectively, wt %...

Mine Drainage Generation and Control Options

“…Interactions in the water-rock-CO2-O2 systems were modeled for different sites within a sulfide-bearing ore deposit (Limantseva et al, 2015). AMD was controlled by the rates of interaction between the various components of the system.…”