Geological Sciences

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Acidic microenvironments in waste rock characterized by neutral drainage: Bacteria-mineral interactions at sulfide surfaces
(MDPI, 2014-03-21) Dockrey, John W.; Lindsay, Matthew B. J.; Mayer, K. Ulrich; Beckie, Roger D.; Norlund, Kelsey L. I.; Warren, Lesley; Southam, Gordon
Microbial populations and microbe-mineral interactions were examined in waste rock characterized by neutral rock drainage (NRD). Samples of three primary sulfide-bearing waste rock types (i.e., marble-hornfels, intrusive, exoskarn) were collected from field-scale experiments at the Antamina Cu–Zn–Mo mine, Peru. Microbial communities within all samples were dominated by neutrophilic thiosulfate oxidizing bacteria. However, acidophilic iron and sulfur oxidizers were present within intrusive waste rock characterized by bulk circumneutral pH drainage. The extensive development of microbially colonized porous Fe(III) (oxy)hydroxide and Fe(III) (oxy)hydroxysulfate precipitates was observed at sulfide-mineral surfaces during examination by field emission-scanning electron microscopy-energy dispersive X-ray spectroscopy (FE-SEM-EDS). Linear combination fitting of bulk extended X-ray absorption fine structure (EXAFS) spectra for these precipitates indicated they were composed of schwertmannite [Fe8O8(OH)6–4.5(SO4)1–1.75], lepidocrocite [γ-FeO(OH)] and K-jarosite [KFe3(OH)6(SO4)2]. The presence of schwertmannite and K-jarosite is indicative of the development of localized acidic microenvironments at sulfide-mineral surfaces. Extensive bacterial colonization of this porous layer and pitting of underlying sulfide-mineral surfaces suggests that acidic microenvironments can play an important role in sulfide-mineral oxidation under bulk circumneutral pH conditions. These findings have important implications for water quality management in NRD settings.
Adsorption of (Poly)vanadate onto Ferrihydrite and Hematite: An In Situ ATR–FTIR Study
(American Chemical Society (ACS) Publications, 2020-03-25) Vessey, Colton; Schmidt, Michael P.; Abdolahnezhad, Mojtaba; Peak, Derek; Lindsay, Matthew B. J.
Vanadium (V) has been a useful trace metal in describing Earth’s biogeochemical cycling and development of industrial processes; however, V has recently been recognized as a potential contaminant of concern. Although Fe (oxyhydr)oxides are important sinks for aqueous V in soils and sediments, our understanding of adsorption mechanisms is currently limited to mononuclear species (i.e., HxVO4(3–x)–). Here we use in situ attenuated total reflectance – Fourier transform infrared spectroscopy to examine sorption mechanisms and capacity for (poly)vanadate attenuation by ferrihydrite and hematite from pH 3 to 6. Adsorption isotherms illustrate the low affinity of polyvanadate species for ferrihydrite surfaces compared to hematite. Mononuclear V species (i.e., [HxVO4](3−x)− and VO2+) were present at all experimental conditions. At low surface loadings and pH 5 and 6, H2VO4− adsorption onto ferrihydrite and hematite surfaces results from formation of inner sphere complexes. At [V]T above 250 µM, adsorbed polynuclear V species in this study include H2V2O72− and V4O124−. Whereas, HV10O286−, H3V10O285−, and NaHV10O284− are the predominant adsorbed species at pH 3 and 4 and elevated [V]T. Surface polymers were identified on hematite at all experimental pH values, whereas polymeric adsorption onto ferrihydrite was limited to pH 3 and 4. These results suggest that hematite offers a more suitable substrate for polymer complexation compared to ferrihydrite. Our results demonstrate the pH and concentration dependant removal of (poly)vanadate species by Fe(III) (oxyhydr)oxides, which has implications for understanding V mobility, behaviour, and fate in the environment.
Alum addition triggers hypoxia in an engineered pit lake
(MDPI, 2022-02-26) Jessen, Gerdhard L.; Chen, Lin-Xing; Mori, Jiro F.; Colenbrander Nelson, Tara E.; Slater, Gregory F.; Lindsay, Matthew B. J.; Banfield, Jillian F.; Warren, Lesley A.
Here, we examine the geobiological response to a whole-lake alum (aluminum sulfate) treatment (2016) of Base Mine Lake (BML), the first pilot-scale pit lake established in the Alberta oil sands region. The rationale for trialing this management amendment was based on its successful use to reduce internal phosphorus loading to eutrophying lakes. Modest increases in water cap epilimnetic oxygen concentrations, associated with increased Secchi depths and chlorophyll-a concentrations, were co-incident with anoxic waters immediately above the fluid fine tailings (FFT) layer post alum. Decreased water cap nitrate and detectable sulfide concentrations, as well as increased hypolimnetic phospholipid fatty acid abundances, signaled greater anaerobic heterotrophic activity. Shifts in microbial community to groups associated with greater organic carbon degradation (i.e., SAR11-LD12 subclade) and the SRB group Desulfuromonodales emerged post alum and the loss of specialist groups associated with carbon-limited, ammonia-rich restricted niches (i.e., MBAE14) also occurred. Alum treatment resulted in additional oxygen consumption associated with increased autochthonous carbon production, watercap anoxia and sulfide generation, which further exacerbate oxygen consumption associated with on-going FFT mobilized reductants. The results illustrate the importance of understanding the broader biogeochemical implications of adaptive management interventions to avoid unanticipated outcomes that pose greater risks and improve tailings reclamation for oil sands operations and, more broadly, the global mining sector.
Analytical formulas for geometrical factor and sensitivity for long electrodes
(Wiley, 2024-11-22) Butler, S.L.
In the electrical resistivity method, electrodes are usually modelled as point current sources and point voltage measurements. If the burial depth of the electrode is significant compared with the spacing between electrodes, this point approximation may not be accurate. Common situations employing long electrodes include the use of metal-cased boreholes as electrodes and small-scale, high-resolution environmental, engineering and archaeological surveys where electrode spacings may be very small. In this contribution, I present analytical expressions for the mutual resistance between long electrodes modelled as line current sources. Mutual resistances are then used to calculate geometrical factors. Additionally, I present an expression for the current density and use it to derive an analytical expression for the sensitivity of electrode arrays with long electrodes. The sensitivity is, in turn, used to calculate the mean depth and position which can be used as estimates of depth and position of investigation and as pseudosection plot points. Example calculations using the geometrical factor, sensitivity and mean depth are shown, and comparisons are made with simulations and lab-scale experiments.
Aqueous vanadate removal by iron(II)-bearing phases under anoxic conditions
(American Chemical Society (ACS) Publications, 2020-03-06) Vessey, Colton; Lindsay, Matthew B. J.
Vanadium contamination is a growing environmental hazard worldwide. Aqueous vanadate (HxVVO4(3−x)− (aq)) concentrations are often controlled by surface complexation with metal (oxyhydr)oxides in oxic environments. However, the geochemical behaviour of this toxic redox sensitive oxyanion in anoxic environments is poorly constrained. Here we describe results of batch experiments to determine kinetics and mechanisms of aqueous H2VVO4− (100 μM) removal under anoxic conditions in suspensions (2.0 g L−1) of magnetite, siderite, pyrite, and mackinawite. We present results of parallel experiments using ferrihydrite (2.0 g L−1) and Fe2+(aq) (200 μM) for comparison. Siderite and mackinawite reached near complete removal (46 µmol g−1) of aqueous vanadate after 3 h and kinetic rates were generally consistent with ferrihydrite. Whereas magnetite removed 18 µmol g−1 of aqueous vanadate after 48 h and uptake by pyrite was limited. Uptake by Fe2+(aq) was observed after 8 h, concomitant with precipitation of secondary Fe phases. X ray absorption spectroscopy revealed V(V) reduction to V(IV) and formation of bidentate corner-sharing surface complexes on magnetite and siderite, and with Fe2+(aq) reaction products. These data also suggest that V(IV) is incorporated into the mackinawite structure. Overall, we demonstrate that Fe(II)-bearing phases can promote aqueous vanadate attenuation and, therefore, limit dissolved V concentrations in anoxic environments.
Aqueous- and solid-phase molybdenum geochemistry of oil sands fluid petroleum coke deposits, Alberta, Canada
(Elsevier, 2018-11-12) Robertson, Jared M.; Nesbitt, Jake A.; Lindsay, Matthew B. J.
Fluid petroleum coke generated at oil sands operations in the Athabasca Oil Sands Region of northern Alberta, Canada, contains elevated concentrations of molybdenum (Mo) and other metals including nickel (Ni) and vanadium (V). Solid-phase Mo concentrations in fluid petroleum coke are typically 10 to 100 times lower than V and Ni, yet dissolved Mo concentrations in associated pore waters are often comparable with these metals. We collected pore water and solids from fluid petroleum coke deposits in the AOSR to examine geochemical controls on Mo mobility. Dissolved Mo concentrations increased with depth below the water table, reaching maxima of 1.4 to 2.2 mg L-1, within a mixing zone between slightly acidic and oxic meteoric water and mildly alkaline and anoxic oil sands process-affected water (OSPW). Dissolved Mo concentrations decreased slightly with depth below the mixing zone. X-ray absorption spectroscopy revealed that Mo(VI) and Mo(IV) species were present in coke solids. The Mo(VI) occurred as tetrahedrally coordinated MoO42- adsorbed via inner- and outer-sphere complexation, and was coordinated in an environment similar to Fe-(hydr)oxide surface complexes. The OSPW likely promoted desorption of outer-sphere Mo(VI) complexes, resulting in higher dissolved Mo concentrations in the mixing zone. The principal Mo(IV) species was MoS2, which originated as a catalyst added upstream of the fluid coking process. Although MoS2 is likely stable under anoxic conditions below the mixing zone, oxidative weathering in the presence of meteoric water may promote long-term Mo release.
Bellerophontid molluscs in the Grimsby Formation (Llandovery, lower Silurian), Hamilton, Ontario, Canada and their paleoecological and taphonomic implications
(Canadian Science Publishing, 2024-08-01) Pratt, Brian R.; Hopkins, Graeme J.; Hopkins, Richard J.
Specimens of a small bellerophontid mollusc, considered conspecific with Planorbis bilobatus Conrad 1839 from coeval strata in New York State, were recovered from the Grimsby Formation (lower Llandovery, lower Silurian), exposed in the Niagara Escarpment of western Hamilton, Ontario. Because Conrad’s species name is pre-occupied and is a secondary homonym, the new material is assigned to Tritonophon grimsbyensis n. sp. As Conrad’s original specimens are lost and where he collected them is unknown, a neotype from the Grimsby Formation is designated. These bellerophonts are preserved as casts on the soles of thin, fine-grained, sandstone beds interbedded with shale. These beds are probably tempestites Most are juvenile forms oriented on their sides, but in some beds adults with a widely expanded aperture are oriented aperture-down. Some specimens exhibit a V-shaped sinus on the median lobe, which is rarely preserved in Silurian examples. The aperture-down orientation suggests that this was the stable position during gentle wave action as well as probably their life position. Beds containing only juveniles may be evidence that the bellerophonts occasionally experienced a population boom but then were killed off during the storm event. Fine-grained sandstone fills the shell interiors, likely emplaced during wave-induced agitation. However, the shell walls are cast in mudstone, indicating that they dissolved during shallow burial and mud was pumped into the moulds. This may have been aided by episodic ground motion due to earthquakes that mobilized the adjacent sediment.
Benchmarking multiphysics software for mantle convection
(Elsevier, 2021-09) Trim, Sean; Butler, Samuel; Spiteri, Raymond
Numerical simulations are a highly valuable tool for improving our understanding of mantle dynamics. COMSOL Multiphysics® is a commercial software suite designed to numerically model experiments featuring multiple branches of physics. This modeling approach applies to mantle convection, which can be viewed as a combination of fluid dynamics and thermodynamics. COMSOL® is of interest to the geoscience community due to its ease of use compared to other available codes, and it has been used in previous mantle convection studies. However, COMSOL® has not been extensively benchmarked for mantle convection. In this study, we confirm the accuracy of COMSOL® against several established benchmarks pertaining to a variety mantle convection features and geometries. Overall, we find reasonable agreement between the results from COMSOL® and reported benchmark data. This study may also serve the geoscience community as a guide for using COMSOL® to model mantle convection.
Bioturbators as ecosystem engineers in space and time
(Palaeontology, 2024) Mangano, Maria Gabriela; Buatois, Luis; Minter, Nicholas John; Gougeon, Romain
Biogenic sedimentary structures offer a unique perspective for understanding the role of the biosphere in the interaction with other Earth subsystems and the building up of our planet. The record of their ancient equivalents provides a wealth of information for reconstructing the role of bioturbators as ecosystem engineers using multiple ichnological proxies and methods. In this study, we present an overview of how bioturbation has worked across a broad range of spatial and temporal scales from the perspective of ecosystem engineering. Comprehensive and systematic datasets allow analyses at regional and global spatial extents, and especially over long temporal scales where sampling intensity and rock record biases can be considered. Our results underscore the significance of the Cambrian Explosion in the establishment of modern-style shallow marine ecosystems and of the Ordovician Radiation for their deep marine counterparts, as well as the continuous ecosystem impact of bioturbation during Palaeozoic terrestrialization. Comparable datasets for the rest of the Phanerozoic have not yet been compiled. However, preliminary information indicates that colonization of ultra-deep tiers, the rise to prominence of regenerators, increased burrowing efficiency, and increased compartmentalization of the endobenthic ecospace, were products of the Mesozoic Marine Revolution. The trace-fossil record offers hard data to evaluate bioturbation as a driving force in ecosystem re-structuring and as a key factor in geobiological cycles. Models assessing these fundamental issues should be rooted empirically at different scales, from both autoecological and synecological to macroecological, making the best possible use of the rich and rapidly developing ichnological toolbox.
Chemical mass transport between fluid fine tailings and the overlying water cover of an oil sands end pit lake
(American Geophysical Union, 2017-05-17) Dompierre, Kathryn A.; Barbour, S. Lee; North, Rebecca L.; Carey, Sean K.; Lindsay, Matthew B. J.
Fluid fine tailings (FFT) are a principal by-product of the bitumen extraction process at oil sands mines. Base Mine Lake (BML)—the first full-scale demonstration oil sands end pit lake (EPL)—contains approximately 1.9 3 108 m^3 of FFT stored under a water cover within a decommissioned mine pit. Chemical mass transfer from the FFT to the water cover can occur via two key processes: (1) advection-dispersion driven by tailings settlement; and (2) FFT disturbance due to fluid movement in the water cover. Dissolved chloride (Cl) was used to evaluate the water cover mass balance and to track mass transport within the underlying FFT based on field sampling and numerical modeling. Results indicated that FFT was the dominant Cl source to the water cover and that the FFT is exhibiting a transient advection-dispersion mass transport regime with intermittent disturbance near the FFT-water interface. The advective pore water flux was estimated by the mass balance to be 0.002 m^3 m^-2 d^-1, which represents 0.73 m of FFT settlement per year. However, the FFT pore water Cl concentrations and corresponding mass transport simulations indicated that advection rates and disturbance depths vary between sample locations. The disturbance depth was estimated to vary with location between 0.75 and 0.95 m. This investigation provides valuable insight for assessing the geochemical evolution of the water cover and performance of EPLs as an oil sands reclamation strategy.
Dissolved selenium(VI) removal by zero-valent iron under oxic conditions: Influence of sulfate and nitrate
(American Chemical Society, 2017-04-17) Das, Soumya; Lindsay, Matthew B. J.; Essilfie-Dughan, Joseph; Hendry, M. James
Dissolved Se(VI) removal by three commercially-available zero-valent irons (ZVIs) was examined in oxic batch experiments under circumneutral pH conditions in the presence and absence of NO3- and SO42-. Environmentally relevant Se(VI) (1 mg/L), NO3- ([NO3-N] = 15 mg/L) and SO42- (1800 mg/L) were employed to simulate mining-impacted waters. Ninety percent Se(VI) removal was achieved within 4 to 8 h in the absence of SO42- and NO3-. Similar Se(VI) removal was observed after 10 to 32 h in the presence of NO3-. Dissolved Se(VI) removal rates exhibited the greatest decrease in the presence of SO42-; 90% Se(VI) removal was measured after 50 to 191 h for SO42- and after 150 to 194 h for SO42- plus NO3- depending on the ZVI tested. Despite differences in removal rates among batches and ZVI materials, Se(VI) removal consistently followed first-order reaction kinetics. Scanning electron microscopy, Raman spectroscopy, and X-ray diffraction analyses of reacted solids showed that Fe(0) present in ZVI undergoes oxidation to magnetite [Fe3O4], wüstite [FeO], lepidocrocite [γ-FeOOH], and goethite [α-FeOOH] over time. X-ray absorption near edge structure spectroscopy indicated that Se(VI) was reduced to Se(IV) and Se(0) during removal. These results demonstrate that ZVI can be effectively used control Se(VI) concentrations in mining impacted waters.
Ebullition enhances chemical mass transport across the tailings-water interface of oil sands pit lakes
(Elsevier, 2021-12-09) Francis, Daniel; Barbour, S. Lee; Lindsay, Matthew B. J.
Base Mine Lake (BML) was the first commercial-scale demonstration oil sands pit lake established in northern Alberta, Canada. Recent studies indicate that ebullition enhances internal mass loading of dissolved constituents during settlement and dewatering of methanogenic fine fluid tailings (FFT) below the overlying water cap. Here, we describe results of integrated field measurements and numerical modelling to (i) determine potential for ebullition and enhanced mixing within BML, and (ii) assess impacts on chemical mass transport across the tailings-water interface. We observed sharp increases in [CH4(aq)] with depth from < 0.1 mg L−1 immediately above the interface to > 60 mg L−1 over the upper 1.5 to 3.0 m of FTT. Thermodynamic modelling revealed that maximum [CH4(aq)] values represent 60 to 80 % of theoretical saturation, and corresponding total dissolved gas pressures approach or exceed fluid pressures. These findings supported integration of enhanced mixing into one-dimensional (1-D) advective-dispersive transport models, which substantially improved upon previous simulations of conservative tracer (i.e., Cl−) profiles and chemical mass fluxes. The models revealed a positive relationship between CH4(aq) saturation and enhanced mixing, showing that ebullition enhance internal mass loading. This information has potential to inform ongoing assessments of pit lake performance and support improved closure and reclamation planning at oil sands mines.
Equilibrium shapes of two and three dimensional two-phase rotating fluid drops with surface tension: effects of inner drop displacement
(American Institute of Physics, 2022-11-01) Butler, Samuel
The shapes of rotating fluid drops held together by surface tension is an important field of study in fluid mechanics. Recently, experiments with micron-scale droplets of liquid helium have been undertaken and it has proven useful to compare the shapes of the resultant superfluid droplets with classical analogs. If the helium is a mixture of He3 and He4, two phases are present. In a recent paper, the shapes of rotating two phase fluid droplets were calculated where the inner drop was constrained to stay at the drop center. The outer shapes and dimensionless rotation rate-angular momentum relationships were shown to be similar to single phase drops provided that the density and surface tension scales were chosen appropriately. In the current paper, I investigate models in which the inner drop can displace from the centre. In order to simplify the analyses, two dimensional drops are first investigated. I show that the inner drop is unstable in the centre position if its density is greater than the outer density and that the inner drop will move towards the outer boundary of the drop in these cases. When the inner drop has a higher density than the outer drop, the moment of inertia of displaced inner drops is increased relative to centered drops and hence the kinetic energy is decreased. Shapes of two and three dimensional drops, rotation rate-angular momentum and kinetic and surface energy relationships are investigated for off-axis inner drops with parameters relevant to recent liquid He experiments.
Evaluating Trace Fossils, Fluvial Architecture, and Colonization Patterns in Channel and Overbank Deposits from the Miocene Vinchina Formation, Vinchina Basin, Western Argentina
(Society for Sedimentary Geology (SEPM), 2024-10-24) Valencia, Gustavo L.; Buatois, Luis; Mangano, Maria Gabriela; Farina, Martin; Krapovickas, Verónica
Trace-fossil distribution within the framework of three-dimensional fluvial architecture has been commonly overlooked. The Miocene Vinchina Formation in western Argentina preserves extensive outcrops of fluvial deposits, including architectural elements of both anastomosing and braided systems identified along the Quebrada de La Troya. Multistorey sandy channels, amalgamated sandy channels, heterolithic multistorey channels, channels with gravel bars, abandoned channels, muddy floodplains, crevasse splays, and crevasse channels have been identified. Of these, only the deposits of three elements were bioturbated, namely crevasse splays, anastomosing abandoned channels, and braided abandoned channels. Vertical simple burrows (Skolithos isp.), large-sized J burrows (Capayanichnus vinchinensis), and simple horizontal burrows (Palaeophycus tubularis) are the most common trace fossils in the Vinchina Formation. Other elements include the horizontal meniscate trace Taenidium barretti and the vertebrate footprints Tacheria troyana, Macrauchenichnus troyana, and Ardeipeda isp. The trace-fossil assemblages identified in the Vinchina Formation collectively illustrate the Scoyenia Ichnofacies. In addition, five ichnofabrics are characterized. The position of the water table, substrate consistency, flow energy, and time between depositional events under arid to semi-arid climate conditions were the main parameters controlling bioturbation. Based on detailed observation of the cross-cutting relationship among ichnotaxa, the ichnofabric distribution and the preservation features of the trace fossils studied, a colonization sequence for each of the subenvironments of the Vinchina Formation is proposed in this study. In addition to integration with conventional facies analysis, articulating ichnologic data and fluvial architecture provides further insights into the application of trace fossils to unravel the sedimentary dynamics of alluvial systems.
Forward modeling of magnetotellurics using Comsol Multiphysics
(2021-12) Li, Ang; Butler, Samuel
Magnetotellurics is an electromagnetic geophysical method that has been widely used to study structures in Earth's subsurface. Numerical modeling of magnetotellurics is important for survey design, inversion, geological interpretation and many other aspects of geophysical studies. For example, modeling a subsurface conductive body in terms of its conductivity, geometry and dipping angle would yield substantial information on the phase response and sensitivity in an MT survey. While there are many different modeling techniques, the finite element method is most commonly used. In this effort, we present magnetotelluric models of layered Earth, uplift structures, auroral electrojets, and geomagnetically induced currents in power-line skywires using the commercial finite-element package Comsol Multiphysics. The AC/DC module in Comsol can be used to solve Maxwell's equations in the quasi-static limit for modeling the magnetotelluric response. One of the advantages of Comsol modeling is its Graphical User Interface (GUI), which allows users to solve complex single or multi-physics problems in a meshed domain. The use of Comsol also reduces the need for sophisticated computer coding when solving partial differential equations such as Maxwell's equations. In the effort presented here, we first discuss model validation for layered Earth geometries. We then present two examples of magnetotellurics modeling in impact crater and geomagnetically induced current studies. Numerical results were compared with analytical solutions or benchmark results whenever possible.
Geochemical and mineralogical aspects of sulfide mine tailings
(Elsevier, 2015-01-30) Lindsay, Matthew B. J.
Tailings generated during processing of sulfide ores represent a substantial risk to water resources. The oxidation of sulfide minerals within tailings deposits can generate low-quality water containing elevated concentrations of SO4, Fe, and associated metal(loid)s. Acid generated during the oxidation of pyrite [FeS2], pyrrhotite [Fe(1-x)S] and other sulfide minerals is neutralized to varying degrees by the dissolution of carbonate, (oxy)hydroxide, and silicate minerals. The extent of acid neutralization and, therefore, pore-water pH is a principal control on the mobility of sulfide-oxidation products within tailings deposits. Metals including Fe(III), Cu, Zn, and Ni often occur at high concentrations and exhibit greater mobility at low pH characteristic of acid mine drainage (AMD). In contrast, (hydr)oxyanion-forming elements including As, Sb, Se, and Mo commonly exhibit greater mobility at circumneutral pH associated with neutral mine drainage (NMD). These differences in mobility largely result from the pH-dependence of mineral precipitation-dissolution and sorption-desorption reactions. Cemented layers of secondary (oxy)hydroxide and (hydroxy)sulfate minerals, referred to as hardpans, may promote attenuation of sulfide-mineral oxidation products within and below the oxidation zone. Hardpans may also limit oxygen ingress and pore-water migration within sulfide tailings deposits. Reduction-oxidation (redox) processes are another important control on metal(loid) mobility within sulfide tailings deposits. Reductive dissolution or transformation of secondary (oxy)hydroxide phases can enhance Fe, Mn, and As mobility within sulfide tailings. Production of H2S via microbial sulfate reduction may promote attenuation of sulfide-oxidation products, including Fe, Zn, Ni, and Tl, via metal-sulfide precipitation. Understanding the dynamics of these interrelated geochemical and mineralogical processes is critical for anticipating and managing water quality associated with sulfide mine tailings.
Geochemical characteristics of oil sands fluid petroleum coke
(Elsevier, 2016-11-30) Nesbitt, Jake A.; Lindsay, Matthew B. J.; chen, ning
The geochemical characteristics of fluid petroleum coke from an oil sands mine in the Athabasca Oil Sands Region (AOSR) of northern Alberta, Canada were investigated. Continuous core samples were collected to 8 m below surface at several locations (n = 12) from three coke deposits at an active oil sands mine. Bulk elemental analyses revealed the coke composition was dominated by C (84.2 ± 2.3 wt. %) and S (6.99 ± 0.26 wt. %). Silicon (9210 ± 3000 mg kg−1), Al (5980 ± 1200 mg kg−1), Fe (4760 ± 1200 mg kg−1), and Ti (1380 ± 430 mg kg−1) were present in lesser amounts. Vanadium (1280 ± 120 mg kg−1) and Ni (230 ± 80 mg kg−1) occurred at the highest concentrations among potentially-hazardous minor and trace elements. Sequential extractions revealed potential for release of these elements under field-relevant conditions. Synchrotron powder X-ray diffraction revealed the presence of Si and Ti oxides, organically-complexed V and hydrated Ni sulfate, and provided information about the aromatic carbon matrix. X-ray absorption near edge structure (XANES) spectroscopy at the V and Ni K-edges revealed that these metals were largely hosted in porphyrins and similar organic complexes throughout coke grains. Slight variations among V and Ni K-edge spectra were largely attributed to slight variations in local coordination of V(IV) and Ni(II) within these organic compounds. However, linear combination fits were improved by including reference spectra for phases with octahedrally-coordinated V(III) and Ni(II). Sulfur and Fe K-edge XANES confirmed that thiophenic coordination and pyritic-ilmenitic coordination are predominant, respectively. These results provide new information on the geochemical and mineralogical composition of oil sands fluid petroleum coke and improve understanding of potential controls on associated water chemistry.
Geochemical conditions influence vanadium, nickel, and molybdenum release from oil sands fluid petroleum coke
(Elsevier, 2022-01-07) Abdolahnezhad, Mojtaba; Lindsay, Matthew B. J.
Petroleum coke is a potential source of vanadium (V), nickel (Ni), and molybdenum (Mo) to water resources in Athabasca Oil Sands Region (AOSR) of northern Alberta, Canada. Large stockpiles of this bitumen upgrading byproduct will be incorporated into mine closure landscapes and understanding the processes and conditions controlling the release and transport of these transition metals is critical for effective reclamation. We performed a series of laboratory column experiments to quantify V, Ni, and Mo release from fluid petroleum coke receiving meteoric water (MW), oil sands process-affected water (OSPW), and acid rock drainage (ARD) influents. We found that influent water chemistry strongly influences metal release, with variations among metals largely attributed to pH-dependent aqueous speciation and surface reactions. Cumulative V, Ni, and Mo mass release was greatest for columns receiving the low-pH ARD influent. Additionally, cumulative V and Mo mass release were greater in columns receiving OSPW compared to MW influent, whereas cumulative Ni mass release was greater in columns receiving MW compared to OSPW influent. Nevertheless, only a small proportion of total V, Ni, and Mo was released during the experiments, with the majority occurring during the first 10 pore volumes (PVs). This study offers insight into geochemical controls on V, Ni, and Mo release from fluid petroleum coke that supports ongoing development of oil sands mine reclamation strategies for landscapes that contain petroleum coke.
Geochronology (zircon U-Pb, Hf, O isotopes), provenance analysis, and tectonic setting of the Paleoproterozoic Karrat Group and supracrustal rocks of the Rinkian fold belt, West Greenland
(Elsevier, 2024-10) Partin, Camille A.; McDonald, Brayden S.; McConnell, Michael; Thrane, Kristine; Pearson, D. Graham; Sarkar, Chiranjeeb; Luo, Yan; Stern, Richard A.
We use zircon U-Pb, Hf and O isotopes to constrain the depositional ages and provenance of metasedimentary rocks of the Paleoproterozoic Karrat Group of West Greenland and to understand the tectonic processes leading to basin development on the eastern Rae craton. An older supracrustal assemblage (Qeqertarssuaq complex) deposited after ca. 2.6 Ga is separated by an unconformity with a younger supracrustal assemblage (the Karrat Group). The Qaarsukassak Formation at the base of the Karrat Group was deposited after ca. 2.0 Ga, with dominantly Archean age modes. The youngest siliciclastic rocks (Nûkavsak and Mârmorilik formations) in the Karrat Group have maximum depositional ages ranging from ca. 1980 to 1950 to 1900 Ma and contain dominant detrital zircon age modes between ca. 2.50 and 1.93 Ga. A ca. 1.92 Ga supracrustal assemblage referred to as the northern domain (Karrat Group, sensu lato) is geographically separated from the Karrat Group (sensu stricto) by the Prøven igneous complex. The stratigraphy and detrital zircon profiles are compared to broadly coeval sedimentary units on the Rae craton and a unifying model of their deposition is presented. The Rae craton is the dominant detritus source; initially these sources were mostly local, changing to a mix of local and distal sources including the western Rae craton. The tectonic setting of the Karrat basin transitioned from extensional to convergent to collisional during its basin evolution, reflecting Wilson cycle phases within an epeiric sea. Accordingly, zircon Hf isotopes in our dataset track the evolution of the opening and closing of the Manikewan Ocean. Detrital zircon Hf isotopes in our dataset reveal a greater proportion of juvenile detritus (especially ca. 2.15–1.95 Ga) than is known from the currently exposed crustal record, pointing to the importance of the detrital zircon record for understanding Paleoproterozoic crustal and tectonic evolution.
Influence of As(V) on precipitation and transformation of schwertmannite in acid mine drainage-impacted waters
(Schweizerbart science publishers, 2018-12-07) Cruz-Hernandez, Pablo; Carrero, Sergio; Pérez-Lópeza, Rafael; Fernandez-Martinez, Alejandro; Lindsay, Matthew B. J.; Dejoie, Catherine; Nieto, José M.
Iron-rich sediments commonly cover riverbeds affected by acid mine drainage (AMD). Initial precipitates are often dominated by schwertmannite, which has an exceptionally high capacity to sequester As and other toxic elements. This poorly crystalline Fe oxyhydroxysulfate rapidly recrystallizes to goethite; however, the influence of trace elements on ageing rates and products is poorly understood. This study examined the influence of As(V) concentrations on the kinetics of schwertmannite precipitation and transformation. Schwertmannite was synthesized in the presence of various initial dissolved As concentrations (i.e., 0–2 mM) and subsequently aged at 40, 60 or 85 °C for 1 h to 300 d. The initial As concentration had a profound impact on schwertmannite precipitation and transformation. Schwertmannite precipitation was inhibited at higher initial As concentrations in favor of pseudo-amorphous Fe-hydroxyarsenate formation. Schwertmannite transformation to goethite was accompanied by sulfate release and, over longer time, As release. Pair distribution function (PDF) analysis of high-energy X-ray diffraction (HEXD) patterns revealed that increasing initial As concentration produced structural defects in associated precipitates. Schwertmannite precipitation exerts an important control on As mobility in AMD-impacted waters; however, this study has demonstrated that the long-term stability of schwertmannite and associated precipitates should be considered when designing AMD remediation strategies and AMD treatment systems.

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