Abstract
The mining industry is a fundamental industry involved in the development of modern society, but is also the world’s largest waste producer. This role will be enhanced in the future, because ore grades are generally decreasing, thus leading to increases in the waste/metal production ratio. Mine wastes deposited on-land in so-called tailings dams, impoundments or waste-dumps have several associated environmental issues that need to be addressed (e.g., acid mine drainage formation due to sulphide oxidation, geotechnical stability, among others), and social concerns due to land use during mining. The mining industry recognizes these concerns and is searching for waste management alternatives for the future. One option used in the past was the marine shore or shallow submarine deposition of this waste material in some parts of the world. After the occurrence of some severe environmental pollution, today the deposition in the deep sea (under constant reducing conditions) is seen as a new, more secure option, due to the general thought that sulphide minerals are geochemically stable under the reduced conditions prevailing in the deep marine environment. This review highlights the mineralogical and geochemical issues (e.g., solubility of sulphides in seawater; reductive dissolution of oxide minerals under reducing conditions), which have to be considered when evaluating whether submarine tailings disposal is a suitable alternative for mine waste.
Highlights
Mining was, is, and will in the future be a fundamental industry involved in the development of human society
To better understand why the submarine tailings disposal (STD) option is again being considered as an option for tailings disposal by the mining industry, we review some key aspects about the formation of acid mine drainage
In STD, this implies that detailed oceanographic studies, including baseline studies of the mineralogy and geochemistry of the sediments, their pore water geochemistry, microbiology and macro fauna, organic matter composition, studies of the complete water column, and long-term studies to predict El Niño-Southern Oscillation (ENSO)
Summary
Mining was, is, and will in the future be a fundamental industry involved in the development of human society. Base metal mining mainly exploits sulphide mineral ores (i.e., minerals which form in the earth’s crust under reducing conditions, for example porphyry deposits; Cu, Mo, Au). This is mainly true for the exploitation of metals like Cu, Zn, Pb, Ni, Mo, Au, Ag, while Al, Fe, and Rare Earth Elements (REE) are extracted mainly from oxide ores (Table 1). Submarine tailings disposal seems to be an attractive option for preventing AMD because sulphide minerals in the mine waste should be geochemically stable in the long-term due to reduced redox conditions in this environment.
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