Investigating the Geochemical Model for Molybdenum Mineralization in the JEB Tailings Management Facility at McClean Lake, Saskatchewan: An X-ray Absorption Spectroscopy Study

Abstract

The geochemical model for Mo mineralization in the JEB Tailings Management Facility (JEB TMF), operated by AREVA Resources Canada at McClean Lake, Saskatchewan, was investigated using X-ray Absorption Near-Edge Spectroscopy (XANES), an elemental-specific technique that is sensitive to low elemental concentrations. Twenty five samples collected during the 2013 sampling campaign from various locations and depths in the TMF were analyzed by XANES. Mo K-edge XANES analysis indicated that the tailings consisted primarily of Mo(6+) species: powellite (CaMoO4), ferrimolybdite (Fe2(MoO4)3·8H2O), and molybdate adsorbed on ferrihydrite (Fe(OH)3 - MoO4). A minor concentration of a Mo(4+) species in the form of molybdenite (MoS2) was also present. Changes in the Mo mineralization over time were inferred by comparing the relative amounts of the Mo species in the tailings to the independently measured aqueous Mo pore water concentration. It was found that ferrimolybdite and molybdate adsorbed on ferrihydrite initially dissolves in the TMF and precipitates as powellite.

Identifying calcium-containing mineral species in the JEB Tailings Management Facility at McClean Lake, Saskatchewan

“…Identifying calcium-containing carbonate is an essential first step to understanding how the HCO3 -(aq) concentration is controlled in the TMF. Our recent X-ray diffraction (XRD), X-ray absorption near-edge spectroscopy (XANES), and X-ray fluorescence (XRF) microprobe studies have proven useful in identifying Mo-bearing mineral species in the TMF, particularly at low concentrations (Hayes et al, 2014;Blanchard et al, 2015). In the current study, the calcium mineralization in the JEB TMF has been investigated using a combination of these techniques.…”

“…AREVA has been investigating the long-term formation of solid phases containing several elements of concern in the TMF (e.g., As, Ni, Mo) (Langmuir et al, 2006;Mahoney et al, 2007;Chen et al, 2009;Hayes et al, 2014;Blanchard et al, 2015). However, there is little known about the behaviour of U in the JEB TMF.…”

Geochemistry, Mineralogy and Microbiology of Molybdenum in Mining-Affected Environments

“…This contrasts with another northern Saskatchewan TMF (the JEB TMF) that operates at lower pH (7.3) and in which Mo (25-505 mg/kg in tailings) exists primarily as powellite, ferrimolybdenite and molybdate adsorbed on ferrihydrite [55,56]. However, rapid changes in the Mo mineralogy occurred in the first five years of the emplacement of tailings in the TFM [56]. Ferrimolybdate and molybdate-sorbed ferrihydrite were shown to dissolve (Figure 2), liberating molybdate.…”

“…Tailings samples with low Fe/Mo (<708) and high Ni/Mo (>113) molar ratios are dominated by NiMoO 4 , otherwise they are dominated by molybdate adsorbed on ferrihydrite. This contrasts with another northern Saskatchewan TMF (the JEB TMF) that operates at lower pH (7.3) and in which Mo (25-505 mg/kg in tailings) exists primarily as powellite, ferrimolybdenite and molybdate adsorbed on ferrihydrite [55,56]. However, rapid changes in the Mo mineralogy occurred in the first five years of the emplacement of tailings in the TFM [56].…”

“…Ferrimolybdate and molybdate-sorbed ferrihydrite were shown to dissolve (Figure 2), liberating molybdate. Subsequently, Mo precipitated as powellite (from 10% of the Mo species in 2008 to 25% in 2013), and this mineral was then proposed to control the long-term stability of Mo in the pore waters [56]. 4 Conlan et al [53]; Petrunic et al [58]; Petrunic [59] Batch experiments simulating conditions and chemicals expected in the Antamina waste-rock piles, Peru, including Mo, SO 4 and calcite, demonstrated that wulfenite formed almost instantaneously and more rapidly that powellite, with Pb concentrations dropping to below detection limits within 15 min.…”