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By Catharine E. G. Farrow, David H. Watkinson

Abstract-The Ni-rich Epidote Zone of the Fraser Mine at Sudbury is characterized by alteration assemblages rich in epidote, actinolite and magnetite which are roughly concentrically zoned and up to hundreds of meters in length. These zones form discrete areas within the igneous Footwall Breccia below the Sudbury Igneous Complex. The assemblages grade from epidotized Footwall Breccia matrix, through actinolite-bearing rocks with few vestiges of original Footwall Breccia textures, into the most intensely altered rock, a magnetite-rich facies. Pentlandite, pyrrhotite and pyrite are the dominant sulfide minerals; chalcopyrite is minor. The strongest geochemical differences compared to original Footwall Breccia occur where epidote and actinolite dominate the alteration assemblage (EPDZact facies). The most intense alteration facies are typified by low Cu/(Cu+Ni) values of <0.1. Strong positive correlations exist between Ni and Co, Cu and Au, and among Ir, Os, Ru and Rh. Chondrite-normalized Ni - PGE - Au - Cu plots display an overall increase in all elements from the least to the most intensely altered facies except for Au and Cu. As the proportion of actinolite increases in the EPDZact facies, the chondrite-normalized profiles flatten considerably due to low Au and Cu contents. Abundances of Ni, Ir, Ru and Rh almost ubiquitously increase with degree of alteration. In contrast, Cu, Zn, Ag and Au contents are low in almost all facies. It is suggested that saline hydrothermal fluids moved through the Epidote Zone formation and became more oxidized as they reacted with the Footwall Breccia and with footwall units, including ultramafic rocks. As this trend continued, magnetite-rich zones eventually developed. The occurrence of calcite locally in these magnetite-rich zones suggests that the pH of the fluid increased, causing Cu solubility to drop as activity in the hydrothermal system waned. Sudden changes in fluid composition such as this may have been due to an influx of fluid from bounding ultramafic rocks. Hydrothermal activity was focused along the margins of footwall ultramafic units. Individual hydrothermal cells may have formed in the Footwall Breccia along pre-existing structures or sulfide concentrations. Metals may have been scavenged from sulfide-bearing Footwall Breccia and possibly Sublayer rocks. Nickel and some PGE were deposited in the Epidote Zone, whereas Cu, Au and Ag continued outward into the footwall where they were deposited as Cu-rich footwall veins.

Jan 1, 1996

By Robin Sheremeta

What is the goal of every organization when it comes to safety? Everyone Going Home Safe and Happy Every Day Good old days: Era of Death (accidents will happen) Era of Engineering: (Eg. hand rails, limitswitches, machine guards, etc.) Era of Legislation: procedures, laws and regulations (Eg. SWP?s, Mines Act) Era of Behaviour-Based Safety: (eg. STOP program)

May 1, 2010

By S. Nakamura, M. Takaoka, Y. Mizuno, T. Kusakabe

"Mercury is produced as a byproduct from gold mines and, historically, has been transferred to recyclers and used for various industrial processes and products. However, under the Minamata Convention on Mercury, adopted in 2013,the intentional use of mercury in processes or products will be minimized in the world. Surplus elemental mercury should be treated as a hazardous waste and consequently, should be converted to a more stable chemical form for long-term storage or permanent disposal. A stabilization method has been developed to react mercury and sulfur using a planetary ball mill. The planetary ball mill can produce high-energy conditions and enable samples to react within a short period of time. A series of tests has been conducted to confirm that mercury sulfide can be produced using a bench scale machine with 2400 mL pot. Under a suitable experimental condition with 25 mm ball diameter, 30%of ball filling rate and 1.05 of molar ratio of S/Hg, a powdered mercury sulfide product was successfully obtained in 60 minutes. The leach ability and atmospheric emission from the product was extremely low. This stabilization method would contribute to an environmentally sound mercury management strategy for the gold industry.INTRODUCTIONDue to its unique physical and chemical properties, mercury has numerous applications, including in industry and medicine. However, mercury and its compounds are highly toxic. For example, in Japan, methyl mercury in waste water caused Minamata disease in the 1950s, which affected large numbers of people (Minamata Disease Municipal Museum, 2001). In recent years, environmental pollution caused by emissions and releases of mercury into the atmosphere, waterbody and land by various emission sources such as coal fire plants, artisanal and small-scale gold mining (ASGM), non-ferrous metal industries, waste incinerations etc. has also become a significant problem. To protect human health and the environment from anthropogenic emissions and releases of mercury and its compounds, the Minamata Convention on Mercury was adopted in 2013(UNEP, 2013)Because ground gold ore typically contains mercury at 0 to 100 ppm, mercury is often produced as a byproduct from gold mines (UNEP, 2016). In gold mining operations, mercury can be released from the ore by roasting or by leaching in cyanide solutions and recovery onto activated carbon. According to Yanget al. (2016), 85.1%of mercury in a concentrate was vaporized during a roasting process. Both processes finally discharge elemental mercury as a byproduct. In the USA, more than 100 ton of mercury was discharged from large-scale and industrial gold mining (Miller, 2004)."

Jan 1, 2017

By M. B. Kime, A. T. Kaniki

"Grinding tests were conducted on an oxidized copper-cobalt ore using a pear-shaped ball mill. Twelve mono-sized ore fractions were prepared and wet ground batchwise. The mill was run for 0.5 to 30 min intervals. The shortest interval provided data more closely related to the breakage function (B) because less secondary breakage was hypothesized. Some selection function (S) and B parameters were determined. Remaining parameters were estimated using a population balance model simulator. To evaluate the kinetics model, an unsized ore sample was also milled. Predicted and measured particle size distributions (PSDs) agreed well, suggesting that S and B parameters can be used for continuous operation mass balances.RÉSUMÉ Des essais de broyage ont été menés sur un minerai oxydé de cuivre-cobalt à l’aide d’un broyeur à boulets piriforme. Douze fractions de minerai de dimension unique ont été préparés et broyés en voie humide en lots. Le broyeur était mis en route à des intervalles de 0,5 à 30 minutes. L’intervalle le plus court fournissait des données plus étroitement liées à la fonction d’abattage (B) car d’après l’hypothèse avancée, le besoin d’abattage secondaire était moindre. Certains paramètres de la fonction de sélection (S) et de B ont été déterminés ; les paramètres restants ont été estimés à l’aide d’un simulateur de modèle d’équilibre de population. Pour évaluer le modèle de cinétique, un échantillon de minerai non calibré a également été broyé. Les compositions granulométriques (PSD, de l’anglais particle size distributions) prévues et mesurées correspondaient bien, ce qui laisse penser que l’on peut se servir des paramètres S et B dans le cadre d’équilibrages massiques en fonctionnement continu. INTRODUCTIONSize reduction of solids is a very energy intensive and highly inefficient process. It consumes approximately 5% of the electricity produced worldwide (Rhodes, 1998), and more than 50% of the total energy used in mineral processing plants (Walkiewicz, Lindroth, & Clark, 1996). An increase in grinding efficiency can therefore result in significant reductions in operating costs. This often amounts to determining the optimal design configurations for milling an ore sample in a laboratory mill under standard conditions. Prior to optimizing the milling stage, the requirements for downstream processing in terms of particle size distribution (PSD) need to be understood because low liberation and overgrinding will lead to future problems. Once this is done, it is also important to clearly understand the breakage properties of the ore. The kinetics of size reduction in tumbling mills are often determined using two probabilistic functions: selection and breakage (Austin & Luckie, 1972). Knowledge of the selection and breakage functions also enables the prediction of the PSD for a given ore sample."

Jan 1, 2017

By D. W. Rogers

Several commercial polyacrylamide flocculants most widely used in Western Canadian mineral processing plants have been analyzed chemically and compared in standardized settling tests as aids to thickening and clarification. Data are included for both dry and liquid-type flocculants. Percentages of active ingredients in these commercial products varied Widely. Performances were compared on the basis of: equal additions of active ingredients, nearly equal molecular weights and nearly equal degrees of ionic character. Based on zone settling velocities and supernatant clarities of siliceous slurries coagulated by lime additions, dry flocculants proved more economical than liquid flocculants. Using these same two criteria, the most highly anionic were more effective than either weakly anionic or non ionic polyacrylamide- type flocculants.

Jan 1, 1978

By S. Lun Sin

In this study, the effect of silicon on the microstructure, mechanical properties and hot tearing susceptibility of permanent mould cast AZ91E magnesium alloy was investigated. Varying amounts of silicon (0.5, 1.0 and 1.5 wt.%) were added to AZ91E in the form of an Al-53 wt.% Si master alloy. The phase formation, grain size and solidification behavior of each alloy were characterized and related to their tensile properties and hot tearing susceptibility. The results showed that the addition of silicon resulted in the formation of Mg2Si particles. The presence of these particles led to an increase of the hardness, but was detrimental to the tensile strength and elongation of AZ91E. However, silicon significantly reduced the hot tearing susceptibility of AZ91E. This was attributed to the reduction of the grain size and the decreased freezing range of AZ91E, which contributed to improve the interdendritic feeding during the last stage of solidification.

Jan 1, 2011

To produce high quality castings, one must monitor the melt quality by evaluating such parameters as the grain refinement and silicon inoculation and modification during the production of the commercial casting. Thermal analysis is a tool one can use for both monitoring and providing input to the process control of the operation. The current technique of performing thermal analysis in commercial foundries is to pour a relatively small quantity of the molten aluminum alloy into a sampling cup and to then acquire the cooling curve. This approach is somewhat simplistic in that one has limited control of the cooling rate and hence the solidification rate of the sample. Moreover, this process requires a fair amount of user intervention and effort. In the past, studies have been conducted in an attempt to develop a system for conducting thermal analysis in-situ. In a study at McGill University, an alkali based heat pipe system was developed for conducting thermal analysis in-situ. While the concept was deemed as very desirable, the complexity of the equipment and procedure was a substantial negative component. In order to improve the technique of accomplishing real-time thermal analysis with an in-situ probe, a new method that is based on McGill heat pipe technology was developed. In the new system, a controllable and flexible water based heat pipe probe is used to solidify a small quantity of metal while residing in the melt. The solidified aluminum is remelted after completing the thermal analysis. This is a key feature of the probe. It resides permanently in the melt yet it is able to both solidify a sample of the melt and then to subsequently remelt it. Various solidification rates encountered in commercial castings are attainable by adjusting the heat extraction rate of the unit.

Jan 1, 2004

By N. Bahrani

Photogrammetry surveys were used to document a footwall slab failure that occurred at a surface coal mine located on the eastern slope of the Rocky Mountains. Photographs taken before and after the failure provided the pre- and post-failure geometry of the slope and the failed slab. A 2D finite element model was constructed using slope profiles. The model contained joint elements that represented the bedding surface upon which the slab slid and the model was used to analyze the footwall slope. The in situ stresses, rock properties and the bedding surface shear strength and stiffness properties are discussed. The process of mining out a valley and exposing a highwall was modelled. As expected, elastic valley rebound occurred in the model, but shear stress and shear displacement reversals along the slip surface were also observed. The modelling results provided new insight into shear strength degradation that occurs when the pit floor approaches and then passes a specific point in the highwall.

Jan 1, 2009

By N. R. Thote, J. L. Porathur, C. P. Verma

Highwall mining is a highly mechanized coal mining method associated with several advantages, such as a very high production rate (approximately 3,000 t/d) and low production costs. There is no requirement for underground support, ventilation, or blasting. Production leads to added recovery, which is otherwise lost in the ultimate pit. The use of highwall mining can bridge the gap that exists between supply and demand in the energy sector. This paper presents a brief review of highwall mining technology, including current status, analysis tools, and design techniques. In addition, it identifies important parameters from the analysis of failure case studies.

Jan 1, 2014

By J. R. Rodda

Stainless steels are widely used to handle concentrated sulphuric acid (H2SO4) solutions produced in the manufacturing process, The majority of corrosion rate data published for stainless steel in product acid conditions is typically complied in tables or in iso-corrosion diagrams (iso-corrosion rates plotted as a function of temperature and H2SO4 concentration), without any reported consideration as to the accuracy and relevance of the method used to obtain the data, Given the characteristic potential cycling associated with the active-passive corrosion behaviour exhibited by stainless steel in hot, concentrated H2SO4, weight loss is considered to be a more reliable method than electrochemical measurements to measure corrosion rates, Consequently, an effort is made herein to demonstrate the accuracy and relevance of weight loss to determine laboratory corrosion rates in product acid conditions.

Jan 1, 2010

By D. M. Hausen

"Refractoriness in Carlin-type gold ores results mostly from fine locking of gold in pyrite, locking in various gangue phases, notably quartz, and a ""preg robbing"" condition attributed to organic carbon. All three conditions may occur in any given deposit, including Newmont &apos;s Carlin and Gold Quarry deposits in Nevada, where types of ref ractoriness occur locally in minor amounts.Measurements of specific gravity, water absorption and screen size distributions of gold in alteration rock types from Gold Quarry show transitional changes from siliceous cherts through decreasingly silicified and increasingly argillized siltstones.Low permeability of siliceous ores contributes to ""size dependent"" refractoriness in cyanidation test work. Colligative physical and chemical measurements demonstrate that silicified cherty ores are difficult to grind, poorly permeable, and less amenable to cyanidation. Refractoriness in pad or column leaching of coarsely crushed siliceous siltstones and cherts is shown to correlate with interrelated measurable mineralogic and physical parameters.IntroductionMetallurgical treatment of variably amenable and refractory types of gold ore may be guided by both analytical and mineralogic data on the interlocking of gold (microscopic an d sub- microscopic) in assorted gangue/sulphide phases. Most oxidized ores from the Carlin gold mine, north of Carlin, Nevada, are amenable to direct cyanidation. The permeability of most oxidized ores from Carlin coupled with the fine size of the gold < 1.5 um) yields rapid extractions and high recovery without fine grinding.Small portions of the Carlin ore body, and also the nearby Maggie Creek and Gold Quarry orebodies, are less amenable to cyanidation, and are classified as refractory. Refractory conditions may be attributed mostly to the association or interlocking of gold with pyrite and /or microcrystalline quartz or chert, and also by the adsorption of leached gold by deleterious forms of carbon, termed ""preg-robbing"" carbon. Each of these conditions are described and defined, with emphasis on a form of silica-locking, which has been referred to as "" size dependent"" refractoriness."

Jan 1, 1985

By Yongquan Zhu, Zhengguo Zhu, Zhichun Liu, Chao Kong, Xinqiang Gao

"The aim of the study is to have a good understanding of the change in the seepage field during and after the tunnel excavation in weathering alteration rock. Field tests are used to monitor the changes of the water table and the numerical model is used to analysis the influence of the seepage filed with different operation conditions during and after the tunnel excavation. Results indicate that the depth, diameter and pumpage of precipitation well are the main factors that have a great influence on the drainage effect. Results also indicate that different operation conditions had various effects on the decrease in water yield during tunnel construction and the recovery in groundwater level after construction.INTRODUCTIONAs a potential disease during tunnel construction, Gushing water not only affected construction schedule, increased construction cost, as well as affected tunnel stability and safety during operation, but also decreased ground-water level. What’s more, the fall of water table caused by gushing water in tunnel would have influenced surrounding residents’ living water, agricultural water and ecological environment around tunnel. In recent years, enough emphasis has been paid to the influence on environment due to the construction of tunnel as a result of the reinforcement of people’s environmental protection awareness.As a result of water collection and drainage after excavation, groundwater was discharged into the tunnel, which caused a loss of water resources in the adjacent mountain mass. Furthermore, during tunnel operation, it was difficult for groundwater level to resume its original condition, which caused a bad ecological environment, because drainage system during tunnel construction destroyed its original hydrologic dynamic balance.In order to study whether decreased groundwater level resulting from tunnel construction could be restored during operation to its original condition, this paper gave a field monitoring on tunnel displacement during construction and simultaneously, generalized model of regional hydrogeology was created according to field hydrogeology to carry out a calculation of stable seepage flow and draw comparisons between recovery conditions of various water levels."

Jan 1, 2015

By P. A. Mascaró, N. Chacon, A. A. Cecchi

"This document shows the development of a system called the “On-line charge level determination in SAG mills” (abbreviated as Jc). The Jc variable has certainly been difficult to measure due to the relevant number of factors and variables that affect the grinding phenomena inside semi autogenous (SAG) mills. To assess the feasibility stage of the proposed system, it was necessary to carry out two tests in different sized SAG mills, 38´ × 22´ and 36´ × 15´, respectively. In each test, the system was configured with a battery of sensors of the following types: (1) strain gauge, (2) accelerometer, and (3) gyroscope. The first step involved for charge level determinations was to determine kidney foot and shoulder by means of a study of the energy-impacts on shell structures. The second step consisted of correlating the measured grinding operational variables with the actual charge levels obtained from SAG mill crash stops. This system development is extremely useful and relevant for providing approximations about mass balances inside SAG mills. It will be a suitable tool for explaining “tonnes per hour” variations and determining optimal points under various operating conditions.INTRODUCTIONThere has been a growing necessity for technologies capable of obtaining “on-line data” of the main comminution variables in order to increase throughput. Computer systems have taken an important role in providing important solutions by means of processing on-line device signals (commonly referred to as monitoring). In semi autogenous (SAG) milling, there are many examples of monitoring devices that allow the operational staff to obtain detailed information both mechanically and electronically inside a grinding circuit. In this context, a new technology has been developed to obtain “Jc total charge (%) online” in two different SAG mills called Vibro-Energy® System.As part of the analysis performed by JKsimMet® the Jb/Jc was estimated because it has an important impact on SAG mill throughput. Different scenarios were simulated and contrasted at various theoretical Jb/Jc values in a baseline circuit (Figure 1)."

Jan 1, 2016

By H. Huang, H. M. Chen, W. B. Xie

Cu-0.8Cr-0.1Zr alloy were prepared by atmospheric melting. the microstructure and properties of the CuCrZr alloy after first cold rolled, solid solution, second cold rolled and aging treatment were analyzed by using optical microscope, electrical conductivity analysis and Vickers hardness tester. The results show that with the increase of the first cold rolled deformation, the grain breakage becomes more serious, and the cold hardening becomes more obvious and the hardness increases. The conductivity and peak hardness of the first cold rolled (reduction of 30% and 60%) alloys after solution, secondary cold rolled and aging treatment reaches 81 %IACS and 187 HV, respectively. However, the conductivity in the CuCrZr alloy with a higher rolling degree (reduction of 90%) after solution, secondary cold rolling and aging treatment is significantly higher, and the conductivity and peak hardness is 85.8 %IACS and 178 HV, respectively. INTRODUCTION CuCrZr alloy has been widely used in domestic industry for its excellent comprehensive properties such as high strength and high conductivity, especially in the contact wire and lead frame of high-speed railway (Sun, Tao, & Lu, 2015; Mishnev, Shakhova, Belyakov, & Kaibyshev, 2015; Zhang et al., 2016; Fu et al., 2017). In recent years, a lot of research has been done on how to improve the strength and conductivity of CuCrZr alloy. However, the high strength and high conductivity of copper alloys are contradictory characteristics. On the one hand, the addition of alloying elements is conducive to solution strengthening and aging strengthening; on the other hand, too much alloying elements in copper alloys cause defects in the lattice of copper matrix, resulting in a serious decline in the conductivity of copper alloys (Martienssen & Walirmont, 2005). How to obtain high strength and high conductivity at the same time is the main problem. At present, the main research methods are adding microalloying elements, thermomechanical treatment and severe plastic deformation to study the electrical conductivity and mechanical properties of CuCrZr alloys. For example, Xie et al. (2011) added trace Ag to the Cu-0.26 wt%Cr-0.08 wt%Zr alloy, and the size of precipitated phase Cr and Cu4Zr became smaller and the mechanical properties of the alloy were improved. Su, Dong, Liu, Li, & Kang (2004) found that the addition of trace Mg in CuCrZr alloy inhibits the growth of precipitated phase and reduces the internal stress around the precipitated phase. At the same time, the size of precipitated phase becomes smaller and the peak aging strength of the alloy is improved. Pang et al. (2013) found that adding trace Ni and Si to the CuCrZr alloy could improve the peak hardness, softening resistance and precipitation morphology of the alloy. Experiments shows that the grain size was significantly refined by equal channel angular extrusion combined with aging treatment, while the strength of the alloy was increased, and the electrical conductivity of the alloy did not decrease (Vinogradov, Patlan, Suzuki, Kitagawa, & Kopylov, 2002; Saray, 2016); Kermajani, Raygan, Hanayi, & Ghaffari (2013) showed that the strength of CuCrZr alloy can be improved by rolling at 500 °C. After 150 minutes of aging treatment, the strength and conductivity of the material increased to 431 MPa and 81 %IACS, respectively. Takata, Ohtake, Kita, Kitagawa, and Tsuji (2009) noted that the strain hardening, uniform elongation and tensile strength of the nano-precipitates produced by the mechanical heat treatment process can be notable enhanced. The mechanical and electrical properties of CuCrZr alloy can be improved by combining large plastic deformation with aging treatment in the test process (Gao, Huttunen-Saarivirta, Tiainen, & Hemmila, 2003; Huang et al., 2003; Xia et al., 2012; Zel’dovich et al., 2014).

Jan 1, 2019

By O. Bouaziz, O. Magnea, P. Cugy, E. F. Rauch

The experimental difficulty to perform Equal Channel Angular Extrusion (ECAE) of a bulk sample of hard material such as steel was overcome. The original method proposed in this paper consists in replacing the bulk sample by a stack of alternated hard metal (steel) and soft metal (aluminium) sheets. By applying this procedure to an Interstitial Free steel (IF steel), 2.7µm grain sized material was obtained after recrystallisation. Its mechanical properties (hardness, formability in shear, hardenability and faigue limit) were investigated and compared with the properties of the same IF steel with conventional grain sizes (12m and 25µm).

Jan 1, 2004

By G. Zeng

Although the solubility of oxygen in zinc electrolyte is less than 9 mg/L, the effect on deposit stability and zinc-dust consumption can be significant. Sodium sulfite is used to deoxygenate the electrolyte. The effect of the sodium-sulfite concentration on cobalt removal is investigated. The results show the reduction of sulfite to elemental sulfur that adhered to the zinc dust surface forming a passivating layer, and small amounts of sodium sulfite have no effect on cobalt removal. The optimum amount of sodium sulfite is 100 mg/L. It is an important consideration in purification circuits to use sodium sulfite as an additive to cobalt cementation.

Jan 1, 2005

By M. C. Bétournay, J. E. Udd

"The Mining Laboratories of CANMET are the principal federal government vehicle for the delivery of mining research in Canada. With research being performed at five locations, which are mostly mining communities, the laboratories are in close proximity to the industry which they serve.The Mining Laboratories have three principal roles: (1) to support government in its development of policy; (2) to aid industry in the enhancement of productivity; and (3) to improve the health and safety of Canadians,both in the workplace in mines and around abandoned mine sites.From 1994 to 1996, CANMET’s mining research was re-focused into four programs. These are: (1) Underground Mine Environments; (2) Mine Mechanization and Automation; (3) Ground Control, and; (4) Coal Mining Health and Safety.In this paper, the authors outline the work of the Mining Laboratories and also identify the areas considered to be primary targets for future mining health and safety research in Canada."

Jan 1, 1997

By J. M. Toye

The Canadian nuclear fuel business relates primarily to supplying fuel for Candu reactors. The product development, manufacturing and marketing activities of our nuclear fuel industry will therefore be determined by the rate of growth of the Candu nuclear reactor business. The nature of this relationship between the Canadian nuclear fuel industry and the Canadian Heavy Water Reactor program will be considered, with particular reference to the factors influencing future economic growth.

Jan 1, 1969

By A. Warczok

Metal losses in discard slag are the main factor determining overall recovery. The metals are present both in dissolved form and as matte or metallic inclusions, varying in size from 2 to 1000 µm. Pyrometallurgical slag cleaning usually consists of heating the slag, reduction of oxides and settling of matte/metal droplets. Heating the slag decreases viscosity and accelerates reactions. Reduction of magnetite liberates inclusions and facilitates co-reduction of dissolved metal oxides. A significant amount of the matte and metal is present as very fine metallic inclusions, too small for settling. The coalescence of these matte or metal inclusions is required to remove them from the slag. The developed new concept of slag cleaning combines DC furnace technology with an extra magnetic field for vigorous slag stirring, enhancing mass transfer to the reductant surface, accelerating the rate of reduction, and destabilizing the emulsion of matte or metal inclusions. Intensive slag stirring increases the probability of collision of inclusions, will accelerate their growth and will therefore improve settling. The process is carried out in a patented DC channel furnace, where the liquid metal or matte layer acts as a cathode and the floating coke bed on the slag surface is the anode. In the first part of the furnace, a superimposed magnetic field induces a Lorentz&apos;s force causing the slag to start an intensive circular motion. The next furnace zone does not experience any stirring and is dedicated for quiet sedimentation of the inclusions. A mathematical model of gravitational coalescence combined with forced slag motion showed the possibilities of effective removal of copper matte inclusions. The results of laboratory pilot scale tests of continuous slag cleaning showed fast slag reduction and confirmed the improved matte removal from the slag. Conceptual analysis shows the potential use of the technology in various other non-ferrous industries, like for example nickel plants. It is also possible to use this technique batch wise.

Jan 1, 2007

By Samuel B. Rombeger

The behavior of gold in hydrothermal systems is evaluated as a function of pH and oxygen and sulphur activities at temperatures to 250°C. Under conditions of stability of pyrite and argillic alteration as emblages, gold will be transported as bisulphide complexes. In systems containing significant amounts of arsenic, thioarsenide complexes may be important. Oxidation, dilution and reduction in sulphur activity would cause gold deposition from saturated solutions under these conditions. Gold chloride complexes will predominate under oxidized conditions where hematite or other oxides are stable and depo ition would result from increase in pH and/or reduction . Absorption and coprecipitation are po sible mechanisms of deposition for gold in certain low grade depo it . Low concentrations of gold in the transporting solution combined with the ignificant solubility of gold as bisulphide complexes, sugge t hydrothermal solutions rarely may be saturated with gold and coprecipitation with sulphides may be an important initial depositional process. Recrystallization of the sulphides in the presence of the hydrothermal solution would be re ponsible for release of gold to more table ite . Thi mechani m i supported by the close association of gold with pyrite in many hydrothermal gold deposits.

Jan 1, 1986