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By M. S. Moats

"The effects of commercial copper electrorefining additives (glue and thiourea) on the electrochemical removal of bismuth are of importance in copper production. It was found that Bi(III) electrodeposition occurs readily from acidic sulfate solution via a diffusion-controlled quasi-reversible reduction. The diffusion coefficient of Bi(III) was measured and found to be less than reported values of copper in similar solutions. The presence of thiourea and/or glue was found to accelerate or de-polarize Bi(III) reduction on stainless steel as compared to the inhibition or polarization of Cu(II) reduction. The additives also inhibited the dissolution of the Bi-Cu co-deposit during cyclic voltammetry. During short term deposition studies, the additives increased the concentration of Bi in co-deposited Cu-Bi products from solutions with low concentrations of Cu (<2 g/L). Bi deposition was significantly suppressed by increasing the Cu(II) concentration in the solution. The formation of a copper layer on the stainless steel electrode appeared to significantly suppress the reduction of Bi(III). This study demonstrates that glue and thiourea depolarize the deposition of bismuth on stainless steel. Therefore, the additives could be used to improve Bi impurity removal during third stage liberation.INTRODUCTIONThe production of high purity copper has been steadily increasing due to the wide application of the metal and its alloys in electrical and electronic products, infrastructure construction, industrial machinery and equipment, general products and transportation (Moskalyk et al., 2003). Most high purity copper is manufactured from copper sulfide mineral concentrates and/or scrap via a pyrometallurgical process followed by electrorefining (Navarro et al., 1999). During the electrorefining process, cast anodes of 99-99.5% purity are electrochemically dissolved into an acidified copper sulfate solution while high purity copper (>99.99%) is plated on stainless steel blanks or copper starter sheets (Davenport et al., 2002). The control of cathode deposit growth (purity and morphology) while maintaining a high current efficiency is of significant importance for copper refining (Ilkhchi et al., 2007). At typically applied current densities for industrial copper electrorefining, mass and charge transfer play important roles in the quality of cathodic products (Hiskey et al., 1998). If the real current density at some surface points is substantially higher owing to uneven current distribution, then rough spots can and will grow faster leading to nodules (Suarez et al., 1992). Nodulated deposits tend to capture solution and anode impurities (slimes) resulting in unacceptable cathode quality (Afifi et al., 1987). Furthermore, these nodules can grow until they eventually contact the anode leading to short circuits and current efficiency reduction (Ilkhchi et al. 2007)."

Jan 1, 2016

By Bruce C. Fielder

"The concentration of uranium in orebodies discovered in the Athabasca Basin of northern Saskatchewan over the last 20 years has increased by a factor of 100. These high grade uranium orebodies are associated with high concentrations of radionuclides, complex mineralogy and an elemental makeup that includes base metals, arsenic, and molybdenum. Exploiting these high grade ores has required metallurgical advances in milling, tailings disposal and effluent treatment as well as changes in the design of uranium mills.This paper describes the most significant advances, including advances in dealing with the environmental issues which have become more prevalent in recent years. The milling processes of the Cluff Lake Mill, Key Lake Mill, Rabbit Lake Mill, and McClean Lake Mill are compared to illustrate both similarities and differences necessary for milling different orebodies.BackgroundUranium mining in Saskatchewan started in 1953 when the Beaverlodge Mine, owned by Eldorado Nuclear Limited (Eldorado), came into operation at Uranium City. Development in the Athabasca basin started in 1975 when the Rabbit Lake mine came into operation. This was followed by the start-up of the Cluff Lake mine in 1980 and the Key Lake mine in 1983. The McClean Lake mine is forecast to start up in the near future. The McArthur River mine recently received construction approval and the Cigar Lake Project and the Midwest Project are currently in the environmental approval process.The Beaverlodge operation ceased production in June 1982 after nearly 30 years of operation. The Rabbit Lake mill processed Rabbit Lake ore from 1975 until 1985, Collins Bay R-Zone ore from 1985 until 1993, and is currently processing ore from the Eagle Point mine (Bharadwaj, Jarvi and Lam, 1996). The Cluff Lake mill processed ore from the D- Orebody from 1980 until 1984. Since then the Claude orebody has been processed and the OP and DS orebodies are presently being milled (SRK. Senes and Melis, 1987; and Cogema Resources Inc. 1994 ). The Key Lake mill processed ore from the Gaertner ore body from 1983 until 1989 and Deilmann ore has been processed since (Cameco Corporation, 1992b and I 994a). Processing of McArthur River ore in the Key Lake mill is scheduled for 1999. The McClean Lake mill will be processing ore from the JLR, Sue and McClcan orebodies associated with the McClean Lake mine. In future ore from the Cigar Lake and Midwest projects will be processed in the McClean Lake mill. (Minatco Limited. 1991a)."

Jan 1, 1998

By N. Bartie

Realising the circular economy (CE) is faced with some significant challenges. Process metallurgy and its infrastructure play key roles at the heart of making the CE work. Therefore, the enabling role of process metallurgy within the CE will be central to the discussion in this paper, touching among others on product and system design as well as the key metallurgical and other process fundamentals that need to be investigated and understood to make the CE a reality. The central role of materials and its processing will be discussed in an integrated circular cities perspective. A key focus will be a discussion on designing a resilient “Smart Materials Grid” using and innovating metallurgical process engineering tools, which will manage the flows through Sustainable Circular Cities. The discussion will be using copper as leitmotiv of the discussion i.e. from copper ore, to metal, to complex products, recycling, product design and simulation and its impact. INTRODUCTION The transformation of our economies from linear to circular models in which waste materials become resources is the focus of the Circular Economy (CE) paradigm. Its important intentions: to take control of the damage we have been doing to the planet to ensure its livability and the welfare of future generations. This can only be achieved through careful utilisation of human, natural and economic resources. The concept is derived from several others (Beaulieu et al., 2015), of which Cradle-to-Cradle, Extended Producer Responsibility (EPR), Industrial Ecology, and Life Cycle Thinking are just a few. Other relevant concepts include resource efficiency (RE), design-for-recycling (DfR), and various others discussed by Blomsma and Brennan (2017) and Homrich et al. (2018), as well as various R-hierarchies e.g. Reduce, Reuse, Recycle (3R). However, does society comprehend these concepts, the actors and actions that influence them and how they interact? Do we know the limits of CE? Does society understand the key role of Copper and other metals to rendering the CE operable? True life cycle and systems thinking, focussed on simulation-based, process and metallurgical design are required to answer these questions. Lieder and Rashid (2016) identify nine widely-varying fields that study the concept ranging from sustainability sciences and engineering to economics, business, law, and social sciences. Overlap between questions addressed highlights the need for interdisciplinary collaboration (Nanz et al., 2017) in the assessment of the current status, and further steps needed to transform to CE. This doesn’t apply just in academia, but also in industry where concrete implementation of CE needs to occur at multiple levels, thus necessitating cooperation between government, civil society and other stakeholders (Beaulieu et al., 2015).

Jan 1, 2019

By S. Avalos, J. M. Ortiz, W. Kracht

Semi-autogenous grinding mills are intensive energy consumers. Current models base their energy consumption inference on operational variables and feeding ore characterization. While they provide adequate design guidelines, they are not suitable for real-time energy forecasting dealing with gaps in operational dataset and up/downstream process bottlenecks. This work explores the capability of Gated Recurrent Units to learn the semi-autogenous grinding mill consumption behaviour. Gated Recurrent Units are trained to forecast different time-support consumptions under a time-series operational dataset. The results show high performance on small supports (30 minutes) to capture local variability and long-trends while larger time supports (8 hours) can only capture time-trends but not local variability. The proposed technique seems promising for further research and implementation on real mine cases since the input variables are low-cost and easy to obtain. INTRODUCTION Current changes in the Chilean energy matrix (Román-Collado, Ordoñez, & Mundaca, 2018), from fossil fuels to renewable energies, have impacted different industries and particularly the mining sector. Solar energy incorporation into greenfield/brownfield projects will help reducing costs and will lead to rethink foundational paradigms (production and processing strategies) (Pamparana et al., 2017). Also, integration of new space-time predicting tools together with automated real-time updating models are some of the main challenges in the geometallurgical framework (Ortiz et al., 2015; van den Boogaart & Tolosana-Delgado, 2018). Those contexts encourage and demand the development of tools capable of predicting the energy consumed by mining systems, being comminution the greatest energy consumer with an average close to 50% of the entire mine consumption (Cochilco, 2013). In comminution, the semi-autogenous grinding mill (SAG) represents the largest energy consumer (~10 nominal each SAG). Theoretical and empirical energy consumption models (Jnr & Morrell, 1995; Morrell, 2004; Silva & Casali, 2015) base their inferences mainly on feed/product size distributions, SAG sizing, bearing pressure, feed hardness, water addition and grinding charge level, and commonly assume steady-state and work isolated from up and downstream processes. While those techniques provide adequate design guidelines, they are not suitable to predict hourly, daily or even weekly energy consumptions on interconnected comminution circuits where upstream/downstream bottlenecks lead SAGs to operate below designed regimes. Forecasting energy consumption is required by short-term energy management, medium and long-term planning energy consumption, designing the nominal capacity of renewable energy sources, among other. Also, when models are input-sensitive and some of those input measurements are expensive and/or time consuming, model robustness suffers when real-time predictions are required.

Jan 1, 2019

By Arthur. H. Winckers, Stephan L. Chryssoulis

"The deportment of gold in residue samples of cyanide leach tests of David Bell ore from level 6A block 13 was established using a comprehensive quantitative mineralogical approach. In every test the feed was first pre-aerated for 4 hours, followed by 48h cyanidation. Test no. 2 was done without lead nitrate and yielded a residue assaying 3.03g Au/t. In test nos. 4 and 9 lead nitrate was added before pre-aeration at 0.03kg/t and 0.3kg/t respectively yielding residues of 1.04 and 0.81 g Au/t.The mineralogical approach employed to establish the deportment of gold involved superpanning, to preconcentrate the free gold and assaying of the tailing fraction to determine the gold associated with quartz. It was thus determined that without lead nitrate added 47.2% of the lost gold is in the form of residual free gold particles less than 20 µm in size. It is this form of gold which is under represented in the residues of leach tests with lead nitrate added.Having eliminated coarseness of gold particles as a factor for lower recovery, it was determined that the residual gold particles have extensively contaminated surfaces. Amongst the deleterious surface contaminants identified: S, As, Ag, Sb and Hg, the two most harmful are S and Hg because of their concentration on the surface and rate of accumulation.Mercury and Ag are minor constituents of native gold at David Bell (average composition Au: 78.9 wt%, Hg: 18.5 wt% and Ag: 2.6 wt%) and they become enriched on the surface of residual gold particles because of their slower rate of dissolution in cyanide. The other elements absorb onto the gold particles from solution.The beneficial effect of lead nitrate was documented by comparative surface analysis of gold from residue samples of 48 hour leach testing with and without lead nitrate added and from time dependent (0-2 hour) leach tests in the presence and absence of lead nitrate. Lead nitrate accelerates the dissolution of gold by performing the following functions: (i) catalytic effect on the cyanidation of gold by accepting electrons; (ii) reaction with surface sulphur to form PbS which is then removed by oxidation; (iii) catalytic reaction on amalgam and Ag facilitating the cyanidation of Hg and Ag thus slowing down their build up onto the dissolving gold particles and (iv) the precipitation of sulphide sulphur from solution thus minimizing its build up on the surface of dissolving gold particles which is believed to facilitate the access of cyanide ions."

Jan 1, 1996

By Gabriel Zarate

"Los Bronces had two ROM dump leach operations designated Leach I and Leach II. Leach I was commissioned in 1998 and stopped in 2014 due to the mine requirements. Leach II plant, commissioned in early 2002, was built to treat around 700 million tons of marginal ROM ore averaging 0.45 % total copper. The mineralogy of this material was estimated to be 70% chalcopyrite, 20% chalcocite/covellite and the balance oxides.The original electrowinning plant design capacity for copper production was nominal 19,500 tonnes per year at a current density of 276 A/m2 and a current efficiency of 92%. Presently, Los Bronces San Francisco plant typically operates at current densities between 390 and 440 A/m2, much higher than the average in the industry, with current efficiencies around 93% and a maximum copper cathodes production of 37,200 tonnes per year.In order to accomplish these achievements, a number of modifications in the process conditions, in the cell hardware and in the operational procedures have been implemented. In the first case, the specific flowrate, copper concentration and temperature of the electrolyte were modified to accommodate the operational requirements facilitating the increased current density. Associated with the cell hardware, a six cells expansion was added, upgraded equipotential inner cell busbars were installed and the cross section of the cathode hanger bars was enlarged for increased current carrying capacity. Documented operational procedures like short circuit detection and cathode weight control were improved.The modifications implemented and the results obtained are discussed in this paper.INTRODUCTIONLos Bronces Division of Anglo American Chile is located up in the Andes Mountains, northeast of Santiago. It had two cathode plants, Los Bronces at an altitude of 3500 meters above sea level (m.a.s.l.) commissioned in 1998 and closed in 2014 and San Francisco at an altitude of 2800 m.a.s.l. and in operation since 2002.The process is leaching run off mine (ROM) low grade copper sulphide ore in dumps. The mineralogy of this material was estimated to be 70% chalcopyrite, 20% chalcocite/covellite and the balance oxides. The average grade is 0.45% total copper (Cut).At Los Bronces dump, Leach I plant, the pregnant leach solution (PLS) was collected and stored in an underground reservoir. From there, it was fed to a solvent extraction plant with a series-parallel configuration in two extraction stages and one stripping stage. The electrolyte produced was fed to the electrowinning plant having 30 cells and 60 cathodes per cell. Maximum capacity of this plant was 12,000 tonnes per year (tpy)."

Jan 1, 2016

By K. E. Haque

"Radium is selectively leachable from uranium ores with various types of lixiviants. Among a number of lixiviants tried on Midwest Lake uranium ore, KCl provided the highest per cent of radium extraction (60%-65%). Leach results further confirmed that a certain portion of Ra is not amenable to KCl leaching. More than 99% of the dissolved radium could be removed by treating the KCl leach liquor with barite or with radium selective complex resin (XFS-43230 resin of Dow Chemical Inc.) or by precipitating as RaBaSO4. Uranium leachings from the Ra-preleached uranium ores indicate that radium leaching prior to uranium may be applied as an extension to the conventional or alternative (i.e. acid chloride) leaching process of uranium ores in order to yield environmentally acceptable tailings (in terms of radium in the solids).IntroductionAt present, radium is considered as an environmental issue, particularly for uranium ore mine mill operations, rather than a commercial commodity. Radium was once a highly priced commodity ($180/mg during the first great war) but now it hardly has any commercial value. Its principal applications were in the field of cancer treatment and in the manufacturing of lwninous dials for watches. Nowadays readily-available synthetic radioisotopes are finding applications in place of radium.Because of scarcity and high toxicity, further commercial applications have never been explored.Radium was first discovered and extracted from uranium ore by P. Curie, M. Curie and G. Bement in 1898. Radium is widely distributed in nature but in exceedingly minute quantities. It is one of the daughter products of uranium or thorium and its maximum concentration is 3.3 x 10-7 part/part of U(21). Because of its short half-life (approximately 1620 years) in a geological time scale, its occurrence in nature as a distinct mineral is most unlikely.The details of the original radium leaching process developed by the Curies and Bernont are in the literature. This process essentially involved the roasting of uranium ore with caustic. carbonate followed by sulphuric acid leaching. The precipitated RaSO4 and BaS04 were treated with boiling Na2CO3 to convert them into the corresponding carbonates which later were dissolved in HCI. RaCI2 and Ba02 were separated and concentrated from the chloride liquor by fractional crystallization. But, in the course of time several modifications were made or proposed to the original process. Regardless of the process employed 226Ra extraction from the uranium ore was seldom better than 90%, and further as much as 20% 2URa loss took place during the concentration and purification process."

Jan 1, 1987

By E. A. Rychkun

"For the last 700years of recorded economic history, man has been subjected to alternating inflationary and deflationary patterns. Through this period of time, a severe deflationary pattern has developed approximately every 55 years, creating 12recordable occurrences. Through the last two centuries, this severe deflationary phenomenon has come to be known as a depression. As these depressions have repeated themselves regularly, they are cyclic. This in turn leads to the question of whether the 13th cycle will also repeat itself in the form of a depression. As this cycle is now 51 years old, we must consider the possibility at about 1984.In analyzing a 700-year record of consumer prices in Southern England, the 55-year cycle appears to vary in shape and intensity. This varying phenomenon is due to the effect of longer cycles upon which each one ""rides "". Because each cycle effectively rides on the next largest, which in turn rides on the next largest and so on, the combined measured effect of all cycles together at any point in time is always unique. This means that anyone cycle can never repeat itself in an exact identical manner. The combined effect therefore is what we observe in the form of prices and, as cycles interact, variations in deflation are produced . The ""science"" of economics attempts to quantify and develop theory on situations which are never identical and hence can be conservatively classified as a useless predictive tool.This means that more unconventional approaches may be required to predict our economic future. In looking at previous depression cycles, it is possible to recognize similarities in human behaviour patterns and hence the resulting economic movements. These behaviour patterns create major events or influencing factors which set the scene for a major deflationary condition. The way in which these factors occur, however, is not predictable. As more and more of these similar events are identified in each cycle, we can increase our confidence on the probability of the last event occurring (a depression). By also unravelling the set of larger cycles, we can determine the potential combined effect at any point in the future.This paper presents a system of cycles ranging from 800 years to 3 years which appear to operate in our economic system. By so doing, a long-term projection into the next century can be made. Finally, the paper deals with the main controlling similarities within the depression cycle, to show that a comparison with our current cycle implies that a major deflationary collapse in the mid 1980&apos;s is virtualy inevitable."

Jan 1, 1980

By N. Golchinfar

Tunnels in deep mines are subjected to high stresses. Fracture and failure of the rock mass around an opening can occur when mining-induced stresses are high. In burst-prone grounds, mining-induced seismicity can cause additional dynamic loading which can further increase the stress around the tunnels. When the dynamic stress reaches the rock mass strength, fracturing can occur and rockburst may happen (depending on loading stiffness around the failed rock mass). Rock support installed in the tunnel must be capable of dissipating dynamic energy and holding the failed rocks. Hence, it is important to estimate the depth of failure for rock support design. This paper focuses on how to model depth of failure under dynamic loading. In the modeling, two scenarios of rock failure are considered. In the first scenario, rock failure occurs under static loading and subsequent dynamic loading further increases the depth of failure. In the second scenario, no failure occurs under static loading but in the subsequent dynamic loading, failure around the tunnel is created.

Aug 1, 2013

By Saba Gharedash

In this study the results of a series of numerical simulations which are conducted for one of the tunnels of the Mashhad metro line 2 project are presented to evaluate the role of tunnel face support pressure and soil strength parameters on deformation of tunnel lining and face deformation. To achieve this goal, comparative numerical simulations of a mechanized tunnel advance in soft non- homogeneous soil on top of the ground water table and beneath the building are conducted and sensitivity analysis is performed. Development of a step by step tunnel construction process is modeled using a three dimensional finite difference model (FLAC3D) taking into account all the relevant components of shield tunneling. In order to understand the mechanism of the effects of a variety of support pressures on face deformation and lining stresses, numerical simulations are conducted. It is found that the use of different face supports causes a considerable influence on the forces of tunnel lining. In addition, it is revealed that building weight help to change the stress paths and the stress distributions in the tunnel lining.

Aug 1, 2013

By Y. Wang

Phosphates and fluorides are used as regulators for the removal of silicates from diasporic-bauxite both in direct and reverse flotation. While using dodecylamine chloride as a collector, micro-flotation studies showed that sodium hexametaphosphate has stronger depressing power on diaspore than on silicate minerals with increasing sodium hexametaphosphate concentration at pH 6.5, but sodium fluorosilicate shows poor depression on diaspore with increasing sodium fluorosilicate concentration at the same pH. Zeta potentials of diaspore and silicate minerals become more negative both in the presence of sodium hexametaphosphate and sodium fluorosilicate. Adsorption density studies indicated that the adsorption density of sodium hexametaphosphate on diaspore is much higher than that on silicate minerals at the concentration of 75 mg/L. FTIR spectroscopy studies show that sodium hexametaphosphate interacted with the Al atoms exposed on the diaspore and silicate minerals surfaces to form P?O?Al bonds through the P02 groups. It is possible that sodium fluorosilicate interacted through F- or [SiF6]2- with silicate minerals surfaces based on the analysis by AES.

Jan 1, 2006

By Robert S. G. Chapman, Kieran M. J. Downes

The Sulphide-Preview Lakes area is located 45 km northeast of La Ronge in northern Saskatchewan. It lies within the southern portion of the Proterozoic La Ronge Volcanic-Sedimentary Belt. Two styles of gold mineralization are present in the Sulphide Lake area , stratabound gold mineralization is intimately associated with a pyrite-pyrrhotite-arsenopyrite-bearing graphitic argillite unit within a sequence of intermediate to felsic volcaniclastics. Past operators established three mineralized zones along this horizon with combined reserves for two of the zones, of about 175,000 tons at 0.22 oz/ton Au. In the Preview Lake area , gold mineralization occurs in variably sheared gabbro/quartz diorite sills within a mixed sedimentary-felsic volcaniclastic sequence. Gold occurs with arsenopyrite, pyrite and minor chalcopyrite associated with quartz veins and stringers. A sulphidebearing graphitic argillite unit occurs in close proximity to the mineralized shears. Past operators delineated seven mineralized shear zones, two of which were drilltested. Average gold grades reported are in the 0.1 to 0.2 oz/ton range with erratic values up to 5.0 oz/ton.

Jan 1, 1986

In recent years, China and India have emerged as major players in the copper sector. Over the last decade, around 50% of additional global refined copper usage growth can be attributed to them. The paper provides an overview of the current and future copper supply and demand situation in both countries. Results from two market studies commissioned by the International Copper Study Group (ICSG) are complemented with recent copper statistics on North-East and South-East Asia, as well as further sectoral analysis. Developments and trends in copper mining and metal production, semis production, and major end use areas are highlighted. While providing insights into sectoral patterns and growth trends, the paper provides the basis for comparing structure and output of the copper sectors in some of the major copper-using countries in Asia. Afterwards, the current copper reservoir in use associated with infrastructure, buildings, industrial equipment, transportation systems and households is assessed using the ICSG Copper Flow Model. Finally, the identified copper flows are analyzed regarding the potential impact on the future world supply and demand situation.

Jan 1, 2007

By N. Schmitt, E. Blond, F. Hild

Working linings of steel ladles progressively damage during the steel manufacturing process due to both severe thermomechanical and chemical stresses. In the framework of the coupling scheme proposed by Blond et al. (1), this study examines the effects of the thermomechanical loading on the onset of microcracking by considering that the complex microstructure of the slag-impregnated brick is fixed during the steelmaking process. The behaviour of the refractory is identified by using thermoelastic-(asymmetric)viscoplastic constitutive equations. Numerical simulations of a simplified geometry of the lining subjected to cyclic thermal loadings at the inner side are shown. Two cases are analysed, namely, i) the material is a homogeneous continuum with a thermoelastic-(asymmetric)viscoplastic behaviour, ii) the material is porous and saturated by liquid slag, and the skeleton has the previous non-linear behaviour. The stress and strain fields are shown, and for the porous medium the interstitial pressure of slag as well. Comparisons between these assumptions are made to assess the role of slag on the degradation of the working lining.

Jan 1, 2004

By K. G. Eriksson

"The first tentative test made to try rubber lining in grinding mills was made in the early twenties. However, because of poor rubber compounds and design the results did not prove to be promising.In the early sixties successful trials of rubber linings were carried out as a result of a cooperation between boliden AB and Skega AB.One of the reasons rubber was not used earlier for linings was the difference in wear characteristics between rubber and steel. The ability to successfully develop rubber mill liners depends on three factors:l. Design2. Material (rubber compounding)3. Experience (knowledge)DESIGNThe main difference between steel and rubber, in material aspect, is the elasticity and the low tensile and shearing strength of rubber. It is necessary to take maximum advantage of the elasticity and to reduce tensile and shearing forces by minimizing the sliding of the mill charge. This is accomplished by using the Lorrain type of liners, i.e., lifter bars and plates. It is, however, necessary to keep a certain balance between lifter bars to optimize liner life and grinding performance."

Jan 1, 1983

By J. Lu

The impact of acid treatment in agglomeration/acid curing on copper extraction and acid consumption was investigated with respect to acid dosage and moisture. Without the addition of water, no agglomeration occurred. At an acid dosage above 15 kg/t, the acid was not completely consumed during acid curing. With the addition of 6.2% water, the particles agglomerated together. Copper, iron, magnesium and manganese were dissolved as sulfates and enriched in the fine fraction of the ore. The copper extraction and net acid consumption increased with increasing acid dosage. The copper extraction for acid curing with the addition of 6.2% water was higher than that without the addition of water due to the improved permeability and the increase in the contact with acid-soluble copper. During acid curing, the reaction of sulfuric acid with muscovite, abite and nacrite mainly took place on the surface of the particles while the reaction of sulfuric acid with clinochlore occurred not only on the surface but also inside the particles.

Jan 1, 2007

By Christopher W. N. Anderson

Induced hyperaccumulation of gold by plants was first reported in 1998 by researchers from Massey University in New Zealand who proposed the idea of mining gold using plants (phytomining). Since that time research has been conducted to understand the conditions under which plants can be made to take up economic amounts of the metal. One key focus has been on the geochemistry of gold-rich soils, leading to a diagnostic test that can predict how suitable a particular soil might be to gold phytomining. Field trials have been conducted at several locations around the world in collaboration with industry partners. A Decision Support System has been developed to assist in the design and management of phytomining operations, and economic modeling has been carried out to set targets levels for phytomining technology. Novel studies are now examining the form of gold in plants. Research suggests that plants may store gold as discrete metallic nanoparticles in leaf and stem tissues, an observation that may lead to new ways to recover the metal from harvested biomass.

Oct 1, 2003

By Rodney S. Read

This paper outlines a reasoned argument why no large-scale fracturing or faulting will be induced in the host rock by a deep geological repository (DGR) for nuclear fuel waste. Four DGR designs in three possible host rocks, including crystalline and sedimentary rock types, are considered. The reasoned argument draws from results of previously conducted thermal- mechanical analyses and new scoping calculations, along with evidence from experiments conducted in Canada and elsewhere. It is concluded that large-scale fracturing in the far-field is implausible given the expected in situ stress conditions in relation to rock strength. Near-field damage development and fracturing are expected in DGR scenarios in the different rock types, but these near-field effects are not expected to lead to large-scale fracturing that could compromise the integrity of the DGR and surrounding rock mass. Additional analysis and characterization activities are recommended to further validate the reasoned argument. Thermo-poroelastic loading of the rock mass is identified as one possible driving mechanism that should be studied further.

May 1, 2009

By Art Hamilton

The Zn-Pb-Cu-Ag ore deposits of the Boundary and N-5 zones near Bathurst, New Brunswick, occur in a polydeforrned volcano-sedimentary sequence that is part of the Ordovician Tetagouche Group. Massive and disseminated sulfides are hosted by an argillaceous to cherty sedimentary sequence that is stratigraphically Wlderlain by a siliceous fragmental unit and is overlain by a feldspar-rich crystal tuff and related tuffaceous rocks. The deposits have a low iron sulfide content relative to that of most stratabound sulfide deposits of the Bathurst-Newcastle mining district. The ore is commonly associated with chlorite- and talc-rich sediments. The N-5 deposit is considered to be the fault-displaced extension of the Boundary deposit. The Boundary deposit is estimated to contain 891 000 t grading 3.31% Pb, 7.96% Zn, 0.32% Cu and 44 g/t Ag; the estimate for the N-5 zone is 330 000 t grading 3.24% Pb, 7.15% Zn, 0.33% Cu, and 37 g/t Ag. The ore is processed at 1000 tpd at the Heath Steele mill.

Jan 1, 1992

By Emilie Williams

The Mouska Mine uses primarily shrinkage mining to extract the narrow veins that contain its mineralization. Mining is currently occurring on levels 12 to 14, reaching depths of 800 m below surface. Although the mine is not considered ?deep?, no backfill is available to fill empty stopes and certain areas remain open for over 500 m in height. As only narrow sill pillars remain to separate the levels, a highstress environment is created. Seismic activity was first observed when mining reached Level 11 (600 m deep) and has steadily increased since then. Seismic activity is associated with the highly-stressed sill and rib pillars; no geological structures have demonstrated significant seismic potential to date. In response to this increase in activity, pillar dimensions have been increased with depth and dynamic ground support has been installed. Seismic and pressure monitoring have been implemented, among other types of instrumentation. The following paper further describes the challenges associated with using conventional methods in the high-stress environment typical of the Canadian Shield, as well as several solutions implemented to mitigate these risks.

Feb 1, 2008