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By Joseph J. Mgumbwa

Pillars are any structures left between two or more underground openings. The stability of pillars is normally considered to depend on shape (defined by width to height ratio), rock mass strength, extraction ratio, in situ stresses and the gross structural features (i.e. joints, contacts, faults etc). Recent experience has shown that pillar stability is also controlled by the relative orientation of the orebody with respect to the in situ principal stress. In inclined orebodies, pillars are loaded in compression and shear, thus creating unsymmetrical stress distribution. Failure mechanisms of these pillars are little known. This paper investigates the failure mechanisms of pillars under shear loading. Two dimensional elastic numerical modeling was used to examine the behavior of pillars in different orebody inclinations relative to the major farfield stress orientation. First, the paper reviews pillar design approaches including the empirical pillar design chart and uses numerical modeling to investigate the effect of the major farfield stress orientation on pillar stability. It is concluded that the empirical pillar design chart be used with caution, and that for orebodies under shear loading mine planning and design should take this into consideration since such geometrical orebody/stress relations put mine structures at higher risk of instability.

Oct 1, 2010

By P. Walford, C. Mealin, D. Good

"The geology of the Ore Fault Ni-Cu deposit has been reinterpreted in the light of recent studies of the geology of the Neoarchean Bird River Sill Complex and the occurrence of economic Ni-Cu and Zn-Cu-Ag mineralization. The Ni-Cu sulfides are hosted by the lower of two parallel NNW-trending and moderately W-dipping mafic-ultramafic intrusions related to the Bird River Sill Complex. The bod¬ies intruded a bimodal volcanic suite consisting of weakly deformed mafic flows and felsic pyroclastic rocks. The mafic volcanic rocks are geochemically related to the MORB-type rocks of the Lamprey Falls Formation, and the felsic volcanic rocks are related to arc-type rocks of the Peterson Creek Formation. The original pyroxene- and olivine-dominated mineralogy of the sills has been replaced by variable ser¬pentine-amphibole-talc-carbonate assemblages.The Ni-Cu sulfide assemblage exhibits textures and geochemical signatures typical of orthomagmatic sulfide mineralization. The sulfide minerals are associated with cumulate layers of magnetic ferrochromite that range in thickness from a few to tens of centimeters. A later event of Zn-Cu-Ag sulfide mineralization associated with quartz veining and garnet-chlorite alteration along a fault that strikes north, dips vertically, and cuts all rock types. The mineralized fault is cut by the NE-trending Peterson Creek shear zone. Where the Ni-Cu and Zn-Cu-Ag mineralized zones intersect, remnant magmatic features such as amphibolite or cumulate ferrochromite bands occur within quartz veins or local chlorite alteration. The mixed zones contain a very unusual polymetallic assemblage of Ni, Cu, Zn, Ag, and platinum group elements (PGE)."

Jan 1, 2009

By M. Y. Levesque

The Australian Government?s Energy Efficiency Opportunities (EEO) program launched in 2006 obliges companies that use more than 0.5 PJ (petajoule) or roughly 139 GWh (gigawatt hour) per year to conduct an energy assessment in order to identify measures to improve energy efficiency. The opportunities identified by the mining sector were assembled in the Mining Significant Opportunities Register that permitted companies not yet embracing and adopting an energy management program to see what those who are, were doing and how much energy was saved, and helps disseminate best practice. The measures can be filtered by company, year, category or equipment type. The creation of a central repository of energy efficiency initiatives is valuable but this existing database could be improved; fields identifying the energy and carbon emission savings associated with a given initiative are a surprising omission. Consequently it does not permit the relative effectiveness of different measures for energy and carbon reductions to be readily assessed. A review of energy management efforts implemented in the mining industry, published in peer reviewed journals, corporate sustainability reports or industry publications during the last 40 years has revealed many examples of best practice. However, the lack of a standardized reporting framework in any of these sources has made it difficult to assess the effectiveness and compare the adopted energy management measures ? just as is the case with the Australian register. In an attempt to address these issues, an improved database structure has been created for energy management measures from the mining industry which identifies energy and financial savings arising from energy management initiatives, classifies applications to specific processes or equipment, and recognizes leaders in the mining industry with respect to energy management. The structure of the register includes the key data relevant to energy management in mining that is absent in the Australian version. The mining industry energy management database has been made available in the public domain where stakeholders can examine the best practice examples. Mining energy champions may also contribute to the register by providing case studies; a standardized entry template affords a quality assurance dimension that is absent in other reporting initiatives. Adoption of this database with its standardized reporting mechanism will enhance transparency of the mining industry in energy matters and help it maintain its social license to operate.

Aug 1, 2013

By K. K. Murray, D. G. Gelderland

"The pressure oxidation autoclave at the Goldcorp’s Red Lake Gold Mines (RLGM) was commissioned in 1991. Since commissioning, the circuit has been well maintained and its capacity increased to mechanical and gaseous oxygen limitations. With advances in available technology, opportunities to produce more sulphide concentrate and a changing business environment, an optimization project has been initiated at RLGM. A multi-phase approach has been developed to optimize both the operations and economics of the circuit. This paper describes the history and future of the autoclave circuit at RLGM.AcknowledmentsWe would like to thank the operations and maintenance staff at Red Lake Gold Mines for their support and openness of mind to enact changes to enhance the operation. We would also like to acknowledge the members of the integrated team from Red Lake maintence, metallurgy, operations and corporate technical services that did the hard work to push past the status quo in order to advance productivity.OpportunityThe Red Lake Gold Mines (RLGM) pressure oxidation (POx) circuit has been in operation for over 25 years processing the high sulphide content gold bearing minerals. Increased sulphide concentrate production from improved flotation recovery and increasing gold sulphide association at depth has led to the POx circuit becoming a throughput bottleneck. The opportunity exists to process increased tonnages of sulphide concentrates and increase gold production. In order to realize this value, it will be necessary to increase the throughput capacity of the POx circuit.BackgroundThe POx autoclave at the RLGM, commissioned in 1991, was Canada’s first gold autoclave. It was installed to replace the two-stage fluid bed roaster that was built when the Campbell mine and mill were constructed in the late Forties. The circuit was originally designed to process 12.5 t/d sulphide sulphur in about 50 t/d of Campbell flotation concentrate. Following the merger of the Campbell and Red Lake Mines in 2006, the POx circuit started processing flotation concentrate from both Campbell and Red Lake Mills. In recent years, the circuit has been processing about 18 t/d sulphide sulphur in 75-85 t/d flotation concentrate."

Jan 1, 2017

By G. Azimi, K. K. Varanasi1, A. T. Paxson, R. Dhiman, H. -M. Kwon

Hydrophobic materials that are robust to harsh environments are needed in a broad range of applications. Although durable materials such as metals and ceramics, which are generally hydrophilic, can be rendered hydrophobic by polymeric modifiers, these materials deteriorate in harsh environments. Here it is shown that a class of ceramics comprising the entire lanthanide oxide series, ranging from ceria to lutecia, is intrinsically hydrophobic. Their hydrophobicity is attributed to their unique electronic structure, which inhibits hydrogen bonding with interfacial water molecules. In addition, this work demonstrates that these ceramics sustain hydrophobicity even after exposure to high-temperature environment (1000 °C for 2 h in air). It is envisioned that this class of robust hydrophobic materials will have far-reaching technological potential in various industrial applications, where water repellency and dropwise condensation are desirable.

Jan 1, 2014

By D. W. Zandee

"IntroductionHaving mined an economic mineral bearing rock which is of insufficient grade to warrant direct smelting, upgrading or beneficiation is required to make it an economically viable ore. The first step in effecting the concentration process is comminution or sequential breaking of the rock to allow liberation and subsequent recovery of the desired mineral particles. Desirably the ore could be broken down to the point where the valuable mineral is completely liberated to maximize the chance of recovering as much of it and in as pure a form as possible. The number of energy intensive stages of breakage required to attain this goal depends on many physical characteristics of the ore such as hardness, friability, toughness, grain size, existing fracture planes and particle shapes.Commonly the distinct stages are primary, secondary and often tertiary crushing and finally grinding. To increase the efficiency of each stage of size reduction, pre-treatment sizing is common.Crusher feed is commonly scalped of large pieces or screened for reduction crushers and classified for secondary grindingcircuits.Although crushing and screening is employed for many different products, this chapter reviews current practice in larger tonnage metalliferous ore treatment plants.Current practice is to use large gyratory or jaw crushers for primary crushing and some sort of gyrating or cone crushers for additional stages of reduction. For autogenous or semiautogenous grinding circuits only the primary crushing stage is necessary, the balance of the work being performed in the grinding stage. For conventional grinding circuits using ball mills or combinations of rod and ball mills, secondary, tertiary and even quaternary crushing stages are normally required.Older type crushers such as stamp mills, double rolls, sledging mills and hammermills are no longer common but are used for small tonnage special processes.Important to efficient crushing are a variety of sizing devices such as grizzlies and vibrating screens. Products at different stages must be stored to give surge capacity and allow controlled feeding rates through mechanical and gravity feeders. These storage piles, bins and feeders as well as crushers and screens are commonly integrated into a total facility by means of conveyor systems. Most often these are endless rubber belts driven by simple or multiple drive mechanisms usually consisting of electric motors and speed reducers."

Jan 1, 1989

By John D. Galloway

Mining is one of the important primary industries of Canada, with a gross production in 1927 estimated at $241,773,000- the highest in the history of the country-and an impressive dividend record. It is quite apparent, therefore, that mining is a business worthy of the careful attention of the people of Canada. Furthermore, with a vast undeveloped territory more or less mineralized, it is highly probable that our mining industry will continue to expand indefinitely, with a consequent increase in production and in the amounts of the yearly profits distributed. In recent years, the public has taken a larger interest than formerly in mining-an interest, moreover, that is not academic, but primarily from the viewpoint of profits. It is quite evident that mining is a profitable business, at least to some, and the average man on the street, hearing of these profits, is attracted thereto. I have no doubt that many of you have .read in promotion prospectuses, with figures to prove it, that mining is the most conservative, the safest, and the highest-yielding business in the world. Now, a lot of this information is best judged by the old saying that "While figures don't lie, liars figure". At the same time, mining, properly conducted, is a profitable business, even though speculative, and undoubtedly much profit will come from Canadian mines in the future. In this paper my conclusions regarding mining investments are based largely on British Columbia experience, together with some slight knowledge of mining conditions in the other Provinces. It is considered, however, that the inferences drawn are applicable to mining throughout Canada.

Jan 1, 1928

By John A. Herbst, Alexander Potapov, Xiangjun Qiu

"High Fidelity Simulation is a name applied to the use of first principles modeling tools including Discrete Element Modeling (DEM), Computational Fluid Dynamics (CFD) and Discrete Grain Breakage (DGB) to mathematically describe and study processing systems. Over the past few years, significant advances have been made in High Fidelity Simulation applications, particularly as many mineral processors have been drawn to the study and use of DEM of grinding mills for optimization purposes. This presentation provides an introduction to High Fidelity Simulation, with an emphasis on DEM. It will include insights into current applications of these tools including the optimal design (wear and throughput) of mill lining systems and media selection, the analysis and design (flow and efficiency) of the back-end of grate discharge mills. Advantages of full mill simulations versus individual sub-process simulations will be demonstrated for a SAG mill with different discharge system designs.INTRODUCTIONHigh Fidelity Simulation is providing mineral processors with the opportunity to analyze the behavior of mineral processing equipment from a fundamental or microscale point of view. In the past complex phenomena such as tumbling mill grinding had to be analyzed using black box tools such as residence time distributions for transport and classification functions for passage of particles through grates; while breakage had to be analyzed using PBM models who derived their form from theory but required direct measurement of kinetics. Today with the help of DEM, CFD and DGB these can be analyzed at a very fundamental level.The key element of DEM simulation is the application of Newton’s laws of motion to individual objects or discrete elements. Using this simulation method one can describe the position, velocity (both translational and rotational) of all objects and the transfer of momentum to other objects (Mishra and Rajamani, 1992; Cleary, 1998; Nordell et al, 2001)."

Jan 1, 2003

By J. Lovering, M. Allan

"INTRODUCTIONThe Afton Mines property is located 180 air miles east-northeast of Vancouver and nine miles west of Kamloops, a city of 60,000 people in south central British Columbia. The deposit is located adjacent to the Trans-Canada Highway at an elevation of 2,231 feet above sea level.Interest in the property dates back to 1898, when a 330 foot shaft was sunk on the Pothook claim immediately south of the existing operations. Since that time many companies and individuals have investigated the possibilities of the area but it was not until 1972 that Afton Mines Ltd. located a significant zone of copper mineralization. The feasibility study was completed in the period 1974-1975, by Teck Corporation Ltd., who control Afton through 50% direct ownership and 65% ownership of Isa Mines, who own a further 23%. Construction began in March, 1976. Ore production started in August, 1977, and the first ore was fed to the mill on December 8. This was the third mine to be brought into operation by Teck since 1975, the others being Newfoundland Zinc and Niobec.The orebody is a porphyry copper deposit which has undergone supergene alteration. It is 1,700 feet long in a west-northwest by east-southeast direction, 300 feet wide and dips at 55° to the south. The mineralization in the supergene zone, which accounts for two-thirds of the known deposit, is rather unusual in that the copper is present primarily as native copper and chalcocite. The grade is one percent with the distribution: 70% native, 25% chalcocite, and 5% chalcopyrite with bornite, covellite, and cuprite."

Jan 1, 1979

By K. V. Phani Prabhakar, G. Padmanabham1, L. Subashini

Laser-arc Hybrid Welding (LAHW) is a relatively recent concept which effectively combines the advantages of laser welding such as the high depth of penetration, low heat input, high welding speed and the positive aspects of arc welding such as better edge bridging and possibility to add filler. For example, steel sections upto 12 mm thickness have been successfully welded in a single pass at a welding speed of 1 m/minute using a 3.5 kW CO2 laser in combination with a MIG arc. Maraging steel of grade M250 is widely used in the aerospace industry in thicknesses upto 10 mm. Conventionally, it is possible to MIG weld such thicknesses in 3-5 passes employing V-Groove joint preparation. However, this multi-pass welding results in formation of reverted austenite in the weld zone after post weld aging; and the high heat input widens the reverted austenite containing heat affected zone which is popularly known as the dark zone/eyebrow zone. Both these zones are detrimental to strength of the welded joint, specifically the fracture toughness. The width of the dark band is an important factor because, thinner the band, it is supported more effectively by the surrounding material. Therefore, in order to avoid multi-pass welding and reduce the overall heat input, single-pass laser-MIG hybrid welding was attempted on 10 mm thick maraging steel M 250 plates using a hybrid laser arc welding system comprising a 3.5 kW CO2 slab laser and a MIG welding system. Simultaneously, multi-pass MIG welds also are produced. Both the laser-MIG hybrid and MIG welds are characterized microstructurally and subjected to mechanical tests such as tensile and fracture toughness in as-welded and post weld aged condition. The amount and distribution of reverted austenite in the fusion zone and width of the dark band was found to be different. Hybrid welds showed a narrow dark band zone and improved mechanical properties. Laser-hybrid and MIG welding investigations carried out on thick section maraging steel M 250 will be presented in detail, including microstructure, tensile properties and fracture toughness of the welds. To the best of the knowledge of the authors there are no reports on laser-MIG hybrid welding of maraging steels.

Jan 1, 2014

By J. C. Escobedo, J. M. Almanza, A. Flores, Cortés. D. A.

Secondary aluminum dross, which has been exposed for several years to atmospheric conditions, was characterized using chemical analysis, X-ray diffraction, optical and scanning electronic microscopy, and energy-dispersive spectroscopy. Based on the characterization, a method to purify the solids is presented. This method starts with the washing of the dross in boiling water to eliminate the soluble compounds like Na and K, followed by the physical separation of the metallic aluminum by milling and screening. Finally, an acid lixiviation process is applied using three different acid solutions, HCl, HNO3, and H2SO4. The best results were obtained using HCl. The main insoluble components of the dross after lixiviation were Al, SiO2, and Al2O3. MgAl2O4, AlN, Si, and Na2Al22O3·2H20 species were also found. Based on the alumina content, the solid product could be suitable as a raw material in the manufacture of castable refractories or metal matrix composites.

Jan 1, 2005

By Keila Gonçalves, Aline Tavares, Danielly Couto

"The sulphide copper deposits from the Carajás area (North region of Brazil) were generated by the percolation of hydrothermal fluids in volcanic and granitic rock and are denominated as IOCG deposits (iron oxide copper-gold deposits). During these hydrothermal events a wide variety of gangue minerals such as amphiboles, biotite and fluorite were formed. These gangue minerals are enriched in fluorine and chlorine which are deleterious elements in the copper concentrate. Chalcopyrite and bornite are the main copper-bearing minerals and they can occur in veins, in brecchia or disseminated in gangue.The study, which included bench scale flotation tests and minipilot plant tests was aimed at improving the fluorine rejection in the flotation process during the flowsheet design for one of these Carajás sulphide copper deposit. All of the study was supported by quantitative mineralogical techniques such as QEMSCAN and the use of a scanning electron microscope (SEM).This paper describes and discusses the results obtained in the metallurgical tests and emphasizes the importance of the quantitative mineralogical characterization during the process conditions optimization and flowsheet design.INTRODUCTIONIron oxide copper-gold (IOCG) deposits encompass a wide spectrum of sulphide-deficient low-Ti magnetite and/or hematite ore bodies of hydrothermal origin and normally have important copper sulphide reserves. In the Carajás mineral province, located at the southeast part of the Amazon Craton in Pará State (Brazil), there is a variety of world-class (>200 million tonnes) Fe-oxide Cu-Au deposits (e.g. Salobo, Cristalino and Sossego), whose genesis has been assigned to hydrothermal fluid percolation in volcanic and granitic rocks. Figure 1 displays the location of the Carajás area.The hydrothermal thermal fluid composition was extremely variable. It may have contained gases, salts (brine) and metals. The metals were carried as various complexes and it is thought to have involved sulphur, chlorine and fluorine containing species. This resulted in some minerals formed during the hydrothermal alteration having high fluorine and chlorine contents. These elements result in smelter penalties in a copper concentrate because they cause the smelter off-gases to be more corrosive."

Jan 1, 2011

By André Pomerleau, Michel Grégoire, René del Villar

"The operation of industrial flotation columns requires the control of at least two variables, the interface position and the bias rate, by manipulation of some appropriate operating variables. Problems arise due to the reliability of existing methods of measuring the bias (i.e bias = tailings water - feed water), a situation which has often forced the industry to disregard this control loop. Moreover, when using such a measuring approach, the identification of the process dynamics is impossible. A second problem arises from the possible interaction between both control loops that might call for the use of a more complex multivariable control strategy.Recent work done at Lava1 University has demonstrated the feasibility of an independent sensor for bias, which models the relation between the conductivity profile across the interface and the bias value using a neural network algorithm. A 250 cm height, 5.25 cm diameter Plexiglas laboratory column was equipped with a series of conductivity electrodes in its uppermost part (across the interface) to measure both interface position and bias rate. Using such equipment, the flotation column dynamics were identified. The results thus obtained permitted the design and implementation of a distributed PI control strategy, where bias was associated to wash water rate and froth depth to tails rate. Both PI controllers were tuned using a frequency-response tuning method. Results of both identification and process control are presented and discussed.INTRODUCTIONFlotation columns are used for the separation of valuable minerals from a carrier gangue. Typically, this device is a tall (9 to 14 m height) cylinder (1 to 3 m in diameter) although other cross sectional shapes are also used. Finely ground ore is fed as a pulp at about 2 m from the top of the column, and pressurized air is introduced through a sparger at the bottom. If the pulp has been properly conditioned with adequate chemical reagents (collectors and modifiers), the valuable mineral particles falling by gravity will attach themselves to the rising air bubbles, and the air-particle aggregates will rise to the top of the column where they overflow as a stream called the concentrate. The gangue particles,, that do not attach to the air bubbles, fall down the column being withdrawn at its bottom in a stream called the tails.A particular characteristic of flotation columns is the addition of a fine spray of water at the top. As the water flows down through the froth zone, it washes out the entrained gangue particles from the mineralized bubbles, thus improving the quality of the concentrate recovered at the top. As a result of its cleaning action, this water stream is called the wash water and the upper zone, the cleaning zone. In order to ensure a downward flow of wash water, a proper water balance must be kept in the froth zone, otherwise the water added at the top might shortcircuit to the concentrate without performing any cleaning action. This net downward flow of water inside the froth zone is called the bias and represents an important operating variable of a flotation column."

Jan 1, 1999

By B. Dubé, R. Friedman, J. Oliver, R. Aubertin, M. Burson, G. Panneton, M. Hamilton, J. Ayer

"The Detour Lake gold deposit is located within the northwestern limit of the Archean Abitibi Subprovince of the Superior Province. Mineralized zones are hosted by a sequence of pillowed and massive flows, hyaloclastite units, and altered ultramafic rocks, and are commonly oriented parallel to a series of high-strain zones that are co-planar to the regional-scale Sunday Lake Deformation Zone. Early in its kinematic history, the Sunday Lake Deformation Zone placed older (2.72 Ga) volcanic rocks of the Detour Lake Formation over younger (2.70 Ga) sedimentary rocks of the Caopatina assemblage. Gold mineralization is also parallel to the position of a laterally persistent siliceous rock unit, the 2.725 Ga ‘Chert Marker Horizon.’ The Chert Marker Horizon coincides with the boundary between the mafic-dominated upper Detour Lake Formation and the ultramafic-dominated lower Detour Lake Formation. Stratigraphic and geochronological data suggest that the Chert Marker Horizon is a deformed felsic volcaniclastic unit. At a cut-off of 0.6 g/t Au, the Detour Lake deposit contains 17.26 million ounces of Au within 445.9 million tonnes of rock grading 1.20 g/t Au. Gold occurs in shear-hosted and extensional vein arrays within rocks of the upper and lower Detour Lake Formation and within the Chert Marker Horizon. The Detour Lake deposit has many of the characteristics of a greenstone-hosted, quartz-carbonate vein deposit; its very large size may be attributed to large-scale rheological controls resulting in the formation of dilatant sites in permissive rock units."

Jan 1, 2012

By Peter Radziszewski

"Typical mining operating costs can be divided between extraction (30 % to 70 %), comminution (30 % to 50 %) and separation (5% to 20% ). Cornminition process costs, representing an important contribution to mining operating costs, can themselves be divided roughly between energy (50 %) and linerkharge wear (50 %). Developing the ability of predicting mill wear will allow a more accurate estimation of wear costs. However, total media wear in a given ball mill grinding process is a product of three recognized wear mechanisms those being abrasion, corrosion and impact. Further, the contribution to total media wear of each of these wear mechanisms has not been well established. In this paper, a overview of abrasive, corrosive and impact wear mechanisms is made from which an empirical wear prediction procedure is proposed. Further, future directions in wear prediction research is outlined. INTRODUCTIONTypical mining operating costs can be divided between extraction (30 % to 70 %), comminution (30 % to 50 %) and separation (5 % to 20 %). Comminition process costs, representing an important contribution to mining operating costs, can themselves be divided roughly between energy (50 %) and lined-charge wear (50 %). With respect to wear, world wide steel consumption as grinding media is estimated at over 600 000 tomes per annum (Malghan, 1982). As such, developing the ability of predicting mill wear will allow a more accurate estimation of wear costs.Charge media wear prediction is actually estimated using the Bond abrasion test. From Bond abrasion index tests, it is possible to determine a wear rate using the following function:"

Jan 1, 2000

By J. S. Fox

"Besshi-type Cu-Zn (-Ag-A u ± Co) deposits are tabular, stratiform volcanogenic sulphide bodies which are usually associated with mafic volcanic rocks of oceanic or intra-plate geochemistry, but which can also be found locally with ultramafic volcanics or subvolcanic mafic intrusions. A thick sequence of continentally-derived clastic sediment usually encloses both the mafic volcanics and the ore. Besshi-type deposits form subaqueously, in epicratonic rifting environments, more-or-less proximally, and as a result of hydrothermal convection in their subjacent mafic volcanic - clastic sedimentary piles. They belong to a rift -related metallogenic spectrum that includes sediment-hosted and Cyprus-type base metal deposits, and may diller genetically from these mainly with respect to rate and degree of crustal extension. Modern analogues to these deposits are f ound in the submarine volcanogenic sinters of the Gulf of California rift system.The associated lithologies and tectonic selling of Besshi-type deposits clearly distinguish them from Kuroko-type ores. This difference also seems to be reflected in their lead isotopic character. For example, leads from Besshi-type deposits in the Sanbagawa belt of Japan and from the Blue Ridge belt of southeastern U.S.A. lie on extended anomalous lead lines and have lowslopes in 207Pb/204 Pb - 206Pb/ 204 Pbspace (Sato and Sasaki, 1980; Leriuray, 1982), wheras those from most Kurokotype mining districts exhibit only narrow isotopic ranges and lie near or on the orogene growth curve (e.g. , Franklin et a I., 1981). More over, where Besshi- and Kuroko-type deposits are found in the same orogene, the former often occur earlier in the tectonic cycle than the tatter (e.g., Japan, the Norwegian Caledonides, the southern Appalachians and south-central Finland).Besshi-type deposits are not confined to any particular part of the world, or to any geological epoch. Moreover, in many mineralized belts, Besshi-type deposits are the predominant volcanogenic ore type. On a world-wide scale, deposits of this type therefore constitute an important base metal resource."

Jan 1, 1984

By Dale Dean, Bill Hancock, Raul Mondragon, Carlos Aguilar, Chris Martin

"In 1942, commercial mining operations began in what is now the Lucky Friday Ag/Pb/Zn mine in Idaho’s Silver Valley. Wholly owned since 1962 by Hecla Mining Company, the mine has produced more than 145 million ounces of silver and has been a mainstay producer in Idaho’s Silver Valley for over 70 years.However, by the early 21st century, the mill had fallen, technologically, seriously behind the rest of the industry. Accordingly, starting in 2005, the current mill management team set to revitalizing the milling operation. This paper will describe how the mill was systematically evaluated and the aging infrastructure replaced with more current technology. Driven by internal mill review studies supported by QEMSCAN mineralogical balancing, the mill has in recent years been through waves of upgrading – from the installation of new mechanical and column flotation equipment to the introduction of on-stream analysis, a technology well-accepted around most of the industry but alien to this technologically conservative mining district.The experience at Lucky Friday is a testament to the need for ongoing structured mill optimisation and technology upgrading in established mining operations. This paper will describe engineering experiences associated with upgrading equipment in an operating mill, contained in a confined building. Experiences in teaching the team new ways of operating a mill, and finally the metallurgical rewards that have been reaped will be described.INTRODUCTIONMining in Idaho’s Silver ValleyIdaho’s Silver Valley is a 64-km long valley flanked by the US Northern Rocky mountains, seldom more the 3-km wide, and stretching across much of Idaho’s northern panhandle, roughly 150 km south of the Canadian border. Mining has been continuously active in the area for more than 140 years, during which time, the Silver Valley has become one of the richest silver producing districts in the world, and as of 1985 had out-produced the 500 years of production from the famed Potosi district in Bolivia. Since 1885, almost 100 deposits have been discovered and worked in the district (Chapman, 2000)."

Jan 1, 2011

The extractive industry has the potential to impact the health and well-being of workers, families and surrounding communities. In the current environment of social performance, project planning considers that activities should be conducted in the best environmentally, socially and economically acceptable way across the development cycle (i.e. from exploration ? post-closure). In this context, health impacts of mining can be mapped and extend over the Life of the Community and can encompass worker injury and disease, exposure to communicable and non-communicable diseases, and health outcomes specific to family and community health and well-being outside the fence. To contribute to an emerging field focused on Health and the Extractive Industry, this paper reviews and compares health activities extracted from social and environmental reports published by selected major mining, oil and gas companies with operations in Australia and Canada. The objective of this review is to map corporate approaches to public health management across our previously developed Life-of-Mine within Life-of-Community (LOMLOC) framework in order to identify and compare trends and behaviour in corporate health investments across the project cycle, as well as identify the level of prevention targeted by this investment activity (i.e. primary, secondary and tertiary prevention of detrimental health impact). With the extractive industry facing ongoing rapid growth worldwide, this paper provides preliminary comparative information about corporate health spending by some companies in Australia and Canada. This information serves as a resource for minerals industry managers, civil society and regulators regarding current health management approaches in this sector.

Aug 1, 2013

By J. R. Hart, V. C. Smith, V. P. Babarovich-Hansen, J. H. Schubert

"An introduction and case study of Mintek's latest generation of Milling Circuit controller, the MillStarTM with IES (Interpreting Expert System) is presented. This paper also describes as a case study its installation on a Southern African base metals concentrator plant which has demonstrated improved operation, greatly reduced variation in product quality, as well as increased capacity and availability of the circuit.In this case study, the MillStarTMw as installed along with several other enhancements, including hydrocyclone underflow monitoring, product particle size estimation and flotation circuit stabilisation. MillStarTM utilised the particle size measurement to control grind to within 2% of setpoint, all the while ensuring sump level control, density control as well as mill power optimisation. Mintek' s expertise in the modelling of tumbling mills allowed the development of a specialised optimising controller that ensured the mill was kept in the most efficient operating region.MillStarTM augments the automatic control with useful user interface features, such as on-line trends of any logged variables, historic data warehousing and retrieval and production summary reports.A novel feature that distinguishes the MillStarTMi s the IES (Interpreting Expert System). This is a feature of the software that works with the automatic control code to generate explanations for control actions made by the controller. Often complex control systems are mysterious in nature, reducing trust and eventually resulting in them being switched off. The IES method of exposing the heart of the controller has proved popular and is seen to have potential as a training tool. 314"

Jan 1, 2000

By Chris Larsen, Ian Orford, Mike Cooper

"An autogenous grinding circuit was commissioned at the Brunswick concentrator in October 1998. The autogenous grinding circuit replaced existing surface crushing plants, fine ore storage, rod and primary ball mills. The 8.54m diameter x 4.27m long (EGL) AN1 mill is driven by a bidirectional variable speed 6.3MW ABB wound rotor motor with Slip Energy Recovery (SER) drive. The AG mill was subsequently converted to SAG operation in May 1999 for a number of reasons. The mill is operated in closed circuit with horizontally inclined 660mm diameter cyclones to produce a circuit product P80 of 85 microns. Extensive test work and JKSimMet design modeling resulted in a production circuit operating closely within design expectations.The circuit is highly instrumented and controlled via a hybrid Programmable Logic Controller (PLC-5) and Fisher PROVOX Distributed Control System (DCS) that is in communication with the property information highway. An expert control system (Gensym G2) is used for control of the SAG mill load.Engineering and construction were completed in 28 months from the time of management approval for the project. The Brunswick AG/SAG mill circuit was commissioned on schedule at the $M 23.5 forecast budget."

Jan 1, 2001