Abstract
This study presents an evaluation of arsenic and other trace metals in the Hrazdan Iron-Ore project in Armenia using a methodology typically associated with Geometallurgical characterization. The principal host of the trace elements is pyrite and oxidized equivalents. Pyrite is a mineral of elemental concern as it has the potential to generate acidic pH in water that it contacts and thus mobilize metals of concern. In the Hrazdan deposit, there is a general excess of neutralizing carbonate minerals that result in adequate buffering of generated acid and limiting the mobility of metal cations in solution. However, metalloids that form oxyanions species such as those of arsenic or chromium tend to be more mobile in neutral to alkaline mine drainage. From the geometallurgical assessment of the mine waste, the results of the geochemical testwork can be explained and the information used to assess potential issues with mine waste storage, timing of metal release and provide a baseline for mitigation strategies.
Highlights
For acid rock drainage and metal leaching (ARDML), one of the principle problematic minerals of interest is the sulfide pyrite
Contaminated-neutral drainage is generated at the Hrazdan project from depositing mine waste and its exposure to chemical weathering with metal(loids) released into waters courses at concentrations that exceed regulation criteria despite a lack of acid-generation
This was shown to be a potential problem during the Hrazdan Iron-Ore deposit where arsenic concentrations in humidity cell tests exceeded applicable water quality guidelines
Summary
For acid rock drainage and metal leaching (ARDML), one of the principle problematic minerals of interest is the sulfide pyrite. Pyrite may be environmentally problematic even when abundant neutralising minerals are present This is because it may contain trace elements that are geochemically mobile in circum-neutral pH, such as arsenic. The weathering and gradual oxidation of sulfides, and in particular pyrite, has the potential to result in acidrock drainage and metal(loid) leaching (ARDML) [4,5,6]. This process is accelerated during mining due to the increased likelihood of sulfide exposure, effectively accelerating the natural weathering process. For ARDML the main deleterious minerals are the sulfides, and of these, due to its greater natural abundance the main contributor to ARDML is pyrite [5]
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