A cross scale investigation of galena oxidation and controls on mobilization of lead in mine waste rock

Pb Mineral Precipitation in Solutions of Sulfate, Carbonate and Phosphate: Measured and Modeled Pb Solubility and Pb2+ Activity

“…Dissolved Pb measured in aqueous solutions containing only carbonate was somewhat greater than predicted by Visual MINTEQ in the alkaline pH range (Figure 1B). With PO 4 present in addition to CO 3 , Pb solubility was decreased markedly but was still greater than predicted by Visual MINTEQ over the entire pH range (6)(7)(8)(9). Possible explanations for these discrepancies could be the slow kinetics of bicarbonate-carbonic acid equilibrium with atmospheric CO 2 leading to greater formation of Pb-carbonate ion pairs [41], or greater soluble ion-pair formation of PO 4 and CO 3 with Pb than predicted based on stability constants in the Visual MINTEQ thermodynamic database.…”

“…Whether Pb carbonates (cerussite, hydrocerussite), Pb oxides, Pb sulfates (anglesite, lanarkite) or Pb phosphates (such as pyromorphite) are ultimately the weathering products from the Pb ore mineral, galena, is dependent on the initial ore rock composition. Thus, oxidative dissolution of galena (PbS) during weathering of waste rock releases aqueous Pb 2+ and SO 4 2− , causing anglesite to be a prevalent mineral in acid environments associated with rocks containing high pyrite levels [1,[5][6][7][8].…”

“…In the alkaline environment of carbonate-rich rocks, cerussite [PbCO 3 ], hydrocerussite [Pb 3 (CO 3 ) 2 (OH) 2 ] and occasionally shannonite [Pb 2 OCO 3 ] have been identified [8,9]. In addition to these minerals, lanarkite [Pb 2 OSO 4 ], leadhillite [Pb 4 SO 4 (CO 3 ) 2 (OH) 2 ] and plumbojarosite [PbFe 6 (SO 4 ) 4 (OH) 2 ] have been identified in soils contaminated by Pb mine wastes [6,10].…”

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 precise formulas of Fe-oxyhydroxide phases identified as the alteration product of weathered chalcopyrite, pyrite, and Fe-bearing sphalerite could not be accurately determined due to a lower chemical sensitivity and spatial resolution of SEM-EDX than other non-destructive X-ray techniques such as electron microprobe analysis (EMPA) (Bao et al, 2021). However, the relative abundances of Fe and O in the alteration zones measured by SEM closely resembled goethite, which is consistent with observations from other studies of mine-waste Fe-sulfide oxidation (Jeong and Lee, 2003;Moncur et al, 2005;Moncur et al, 2009).…”