Abstract

To construct the standard methods for evaluation of physicochemical characteristics of tailings in Korea, specific gravity, paste pH, grain size, mineral compositions and heavy metal concentrations of total 26 tailings from 21 metallic mines were analyzed. Specific gravity of tailings ranged from 2.61 to 4.31 (avg. 3.04), and sand and silt grain were dominant in the tailings. Ranges of paste pH were 2.1-9.5 in tailings (7.1-9.2 at magmatic, skarn and hydrothermal replacement deposits and 2.1-9.5 at hydrothermal vein deposits). Additionally, hydrothermal vein deposits could be reclassified into three categories: (1) paste pH>7.0, (2) 4.0<paste pH<7.0, and (3) paste pH<4.0.
Tailings above pH 7.0 have large amounts of carbonate minerals. However, tailings under pH 7.0 have small amount of carbonates, but have sulfide minerals commonly. Especially, tailings under pH 4.0 typically contain supergene minerals. The presence and amounts of carbonates were more important than those of sulfides in determining paste pH in tailings. From the comprehensive results of total concentrations, grain size and extraction experiments, it is revealed that types of deposits were not related with the total and leaching concentrations in tailings, but the ore minerals and their amounts in deposits determined the metal content in tailings. Most mines having tailings with pH<4.0, contained large amounts of heavy metals and strong acidic characteristics, indicating that the deposits of this type have possibility of contamination and/or have contaminated surrounding environments. In this study, problematic elements, inferred from extraction experiment by Korean standard method for soils, were As and Zn. Especially, arsenic appeared to exceed the regulatory level in tailings (pH<4.0) from hydrothermal vein deposits, and in a less degree, zinc often exceeded regulatory level in most type of deposits, except of magmatic deposit.

Keywords tailings, standardization, physicochemical characterization, mineral deposit types