Faro Waste Rock Project: Characterizing geochemical heterogeneity in sulfide- and carbonate-rich waste rock

Mobility of Heavy Metals in Aquatic Environments Impacted by Ancient Mining-Waste

“…Furthermore, oxygen can also enter lateral parts of reservoir upward and into basal regions. Nevertheless, in the rainy season, tailings deposits can become saturated with water, so diffusion is the main oxygen transport mechanism [14].…”

“…During oxidation process, one mole of pyrite and pyrrhotite with atmospheric oxygen, is the main electron acceptor, and water form Fe 2+ , 4 and 2 moles of acid, respectively [9]. However, sphalerite, chalcopyrite, galena and arsenopyrite also contribute to the generation of acid drainage [4,14]. Relative resistances of sulfide minerals and magnetite in oxidized tailings taken from [9].…”

“…The heat generated by that exothermic reaction of pyrite, as long as there is high permeability in the tailings cover, it transports oxygen by convection, increasing oxidation rate of sulfides. However, when a reservoir is saturated with water, advective transport is reduced and the main oxygen transport mechanism is diffusion [14,16]. In addition, oxygen can be supplied by wind in lateral parts of deposit, where oxygen can migrate upward or reach basal regions by advection, convection and diffusion, [17].…”

Investigating Mineral Weathering and Metal Transport through Century-Old Ore Chimney Waste Rock

“…However, there is less emphasis in the literature on evaluating these processes in aerobic waste-rock systems (Lefebvre et al, 2001;Sracek et al, 2004;Smith et al, 2013b;Langman et al, 2014). Delineating waste-rock weathering mechanisms, which change over time and govern in situ geochemical signatures is typically accomplished by applying an array of analytical techniques that may include optical microscopy, SEM-EDX, electron microprobe analysis (EMPA), total C/S, XRD, ICP-AES/MS, and X-ray absorption spectroscopy (XAS) (Smith et al, 2013a;Langman et al, 2014;Elghali et al, 2018;Langman and Moberly, 2018;Bao et al, 2020, Bao et al, 2021.…”

“…The oxidation of sulfide minerals is thermodynamically favourable in ambient aerobic settings and predicts the release of metals and acidity into proximate porewaters, which has long been recognized and described as "acid mine drainage" (AMD) (Nordstrom, 1982;Akcil and Koldas, 2006). However, waste rock piles are multi-component systems that often host carbonate minerals with an affinity to counteract the release of acidity through neutralization reactions that maintain near-neutral pH, with the most common examples being calcite and dolomite (Parbhakar-Fox and Lottermoser, 2017;Bao et al, 2020). As such, carbonate-rich waste-rock piles have been observed to maintain near-neutral pH throughflow waters, which is appropriately described as "neutral mine drainage"…”