Vale Inc.

Toronto, Canada

Vale Inc.

Toronto, Canada
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Keays R.R.,Monash University | Keays R.R.,Laurentian University | Lightfoot P.C.,Vale Inc.
Mineralium Deposita | Year: 2010

Process models for ore formation in magmatic Ni-Cu-platinum group element (PGE) sulfide systems require that S saturation is achieved in a mafic-ultramafic magma. Traditional models explain the achievement of S saturation or sulfide saturation either by the addition of crustal S, by the felsification of the magma by crustal contamination, or by mixing between primitive and evolved magmas. Which process matters most is important to industry-oriented exploration models where crustal S sources are believed to be encouraging features of a metallotect. Studies of the Siberian Trap flood basalts at Noril'sk have demonstrated that chalcophile element depletion is linked to assimilation of silica-rich crust, but it is less clear whether this contaminant contained an appreciable amount of S. At Noril'sk, the Ni-Cu-PGE sulfide deposits are associated with subvolcanic intrusions that were emplaced into Permian and Carboniferous sedimentary sequences rich in shales, marlstones, and evaporites. Similar to the Siberian Trap basalts, the Deccan Trap contains a volumetrically important suite of crustally contaminated tholeiitic basalts. We present new PGE data for samples from a stratigraphic sequence of basalts from the southern Deccan province. Two of the formations in this sequence (the Bushe and Poladpur Formations) have geochemical signatures indicative of a wide degree of crustal contamination of a magma type that gave rise to the stratigraphically higher Ambenali Formation (a product of transitional midocean ridge basalt magmatism). There are no known deposits or occurrences of Ni-Cu-PGE sulfides associated with subvolcanic intrusions in the Deccan province. Despite the fact that the Bushe Formation exhibits a stronger crustal contamination signature than the most contaminated Siberian Trap basalt formations, and the Poladpur lavas are also strongly crustally contaminated, the Bushe and Poladpur basalts are undepleted in Ni, Cu, or PGE. This indicates that the contaminated Deccan Trap lavas did not achieve S saturation. This, in turn, places constraints on the potential of the Deccan Trap in southern India to host significant magmatic sulfide deposits. Conversely, this observation also indicates that an S-rich crustal contaminant is required for the genesis of magmatic Ni-Cu-PGE sulfide deposits. © 2009 Springer-Verlag.

Perozzi L.,Center Eau Terre Environnement | Gloaguen E.,Center Eau Terre Environnement | Rondenay S.,Massachusetts Institute of Technology | McDowell G.,Vale Inc.
Journal of Applied Geophysics | Year: 2012

Modeling of grades is a key step and the major source of error in appraisal stage of mining projects. We used a geostatistical approach to explicitly integrate seismic travel time data, as well as acoustic and core logging data into the estimation of nickel grades in the Voisey's Bay deposit. Firstly, the crosshole seismic travel times are inverted using a stochastic tomographic algorithm. This algorithm allows for the inclusion of acoustic log data and seismic covariance into the inverse problem, leading to high-resolution velocity tomographic images of the orebody. Secondly, grade realizations are generated using a Bayesian sequential Gaussian simulation algorithm, which integrates the ore grades measured on the core logs and the previously inverted tomographic data. The application of the presented method to the Voisey's Bay deposit yields an improved knowledge of the geology setting and generates grade models with realistic spatial variability compared to conventional methods. © 2011 Elsevier B.V.

Abdellah W.,McGill University | Mitri H.S.,McGill University | Thibodeau D.,Vale Inc. | Moreau-Verlaan L.,Vale Inc.
Canadian Geotechnical Journal | Year: 2014

Mine developments, such as haulage drifts, cross-cuts, and intersections, are the only way to access valuable ore from mining zones; they link mine developments with the nearest ore access points. Thus, they must remain stable throughout their service life or production plan. Mine development instability can cause production delay, loss of reserves, as well as damage to equipment and injury to miners. This paper presents a stepwise methodology to assess the stability of mine development intersections with respect to the mine production plan. A case study, the #1 Shear East orebody at Vale Garson Mine in Sudbury, Ontario, is presented. A three-dimensional, elastoplastic, finite difference model (FLAC 3D) is created to simulate the development of an intersection situated 1.5 km below ground surface. The unsatisfactory performance of the intersection is evaluated in terms of strengthto- stress ratio with respect to mining sequence. A failure criterion is defined by a minimum strength-to-stress ratio of 1.4, and is used for mine developments (temporary openings). The intersection stability is evaluated at various mining stages and the modified "point-estimate method" (PEM) of (2n2 + 1) is then invoked to study the probability of drift instability at the intersection. The results are presented and categorized with respect to probability, instability, and mining stage.

Shnorhokian S.,McGill University | Mitri H.S.,McGill University | Moreau-Verlaan L.,Vale Inc.
International Journal of Rock Mechanics and Mining Sciences | Year: 2015

Numerical modelling is a vital tool in the mining industry and is widely used for planning purposes as well as for examining phenomena on a mine-wide scale. In this paper, a comprehensive rock mechanics study is conducted for the planned mining sequence within an orebody that leads to the formation of a diminishing ore pillar at the Vale Garson Mine in Sudbury, Ontario. A mine-wide numerical model is first constructed in FLAC3D with input parameters derived from laboratory tests and borehole log data, and is then calibrated based on in-situ stress measurements. The planned mining sequence scenario, comprising mining fronts advancing from the eastern and western sides of the orebody, is examined based on a combined numerical-volumetric analysis. A qualitative assessment of "ore at risk" is first made based on two instability indicators; the brittle shear ratio (BSR) and major principal stress (σ1). In addition, two other sequence scenarios are examined in which mining is accelerated in the east. A quantitative comparison of the results is then made for the three options using the same instability indicators. Based on the optimum sequence scenario, an assessment is conducted of effects emanating from variations in constitutive models and the presence of a shear zone. In the final phase, the BSR and the presence of tensile conditions are used as instability indicators to study the volume of "ore at risk" in stopes adjacent to an opening during a mining stage. It is shown that the proposed methodology, while simple, can nevertheless be a powerful tool for the planning and validation of stope extraction sequence scenarios, and can be used in conjunction with multiple stability indicators. © 2015 Elsevier Ltd.

Marin T.,Vale Inc. | Utigard T.,University of Toronto
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2010

The rate of deoxidation of molten copper during top blowing with various reducing gases has been investigated using thermogravimetry. It was observed that the rate of deoxidation increases with an increasing flow rate of H 2 or CO and that H2 is a more effective reducing reagent than CO. The rate of deoxidation using methane was measured for O 2/CH4 ratios from 1.5 to 2.0. As expected, the deoxidation rate decreased with an increasing O2/CH4 feed ratio because the flame became less reducing. For all tests, initially there is a linear decrease in mass as oxygen is removed. However, for some experiments, after some time, a sudden acceleration in the rate of mass loss occurs. Using video and X-ray imaging, it was found that this pattern corresponded to gas evolution from within the molten copper. This finding can be explained by the sudden water vapor evolution because the hydrogen dissolved in the copper reacts with the remaining oxygen, and 'boiling' takes place, leading to an enhanced stirring of the copper. © The Minerals, Metals & Materials Society and ASM International 2010.

Wang Y.,McMaster University | Min Yang Q.,Vale Inc. | Zhitomirsky I.,McMaster University
Materials and Manufacturing Processes | Year: 2011

Chemical and electrochemical impregnation methods have been developed for the fabrication of manganese dioxide electrodes for electrochemical supercapacitors using Ni plaques as current collectors. The methods enabled the synthesis of manganese dioxide in-situ in pores of Ni plaques. The chemical method was based on the reduction of KMnO4 solutions with isopropanol. Cathodic galvanostatic method and reverse pulse electrosynthesis method were investigated for electrochemical impregnation. The material loading was varied by the variation of the number of the dipping-reduction procedures in the chemical precipitation method or by variation of charge passed in the electrochemical methods. The microstructures of the electrodes prepared using different methods were studied by scanning electron microscopy (SEM). The electrochemical behavior of the electrodes was studied using cyclic voltammetry and impedance spectroscopy. The electrodes exhibited capacitive behavior in the 0.5M Na 2SO4 lectrolyte in a voltage window of 0-0.9V. The results obtained by different methods were compared. The chemical precipitation method offered the advantage of higher specific capacitance, whereas electrochemical methods allowed higher material synthesis rate. The highest specific capacitance of 236F g-1 was obtained at a scan rate of 2mV s-1. The specific capacitance decreased with increasing scan rate. Testing results showed that the electrodes prepared by chemical and electrochemical in-situ precipitation methods can be used for application in electrochemical supercapacitors. Copyright © Taylor & Francis Group, LLC.

Li J.,McMaster University | Yang Q.M.,Vale Inc. | Zhitomirsky I.,McMaster University
Nanoscale Research Letters | Year: 2010

Manganese dioxide nanofibers with length ranged from 0. 1 to 1 μm and a diameter of about 4-6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT) into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7-15 mg cm -2, showed a capacitive behavior in 0. 5-M Na 2SO 4 solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC). The highest SC of 185 F g -1 was obtained at a scan rate of 2 mV s -1 for mass loading of 7 mg cm -2. The SC decreased with increasing scan rate and increasing electrode mass. © The Author(s) 2010.

Vasiluk L.,University of Guelph | Dutton M.D.,Vale Inc. | Hale B.,University of Guelph
Science of the Total Environment | Year: 2011

This study determined nickel (Ni) bioaccessibility in weathered smelter-contaminated soils, separately for particle-sized fractions using two in vitro methods: simulated gastrointestinal digestion (PBET) and PBET followed by absorption by Caco-2 cells. Relative bioavailability of Ni in soils was determined in vivo using rats, validating in vitro estimates; a mineralogical basis of variation in bioavailability/bioaccessibility among soils was explored. In vitro assays identified the same difference in bioaccessibility for Ni among particle size fractions. PBET estimates were more precise, thus likely to be more useful in discerning differences among soils. In vivo bioavailability for Ni was below limit of detection for the small soil particles, and 31% and 56% for the larger particles. The relative bioavailability calculated from this work suggests that risk from ingesting Ni-contaminated soils could be overestimated by between 2- and 50-fold if the estimates of exposure are not adjusted for the lower bioavailability of weathered Ni originating from smelter emissions. The overestimation that would occur by using total Ni is greatest for the particle size that is most likely to adhere to the hands of children, demonstrating the importance of particle-size separation of soils for bioavailability determination and risk assessment. © 2011 Elsevier B.V.

Vale Inc. | Date: 2010-07-19

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