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By Mehmet F. Taner

"Abstract - "Les Mines Selbaie" is a large, generally low-grade, polymetallic (Zn, Cu, Ag, Au) "giant" volcanic-associated ore deposit in the Harricana-Turgeon belt, which is part of the northern Abitibi Subprovince of Quebec. Economically recoverable mineralization occurred in three zones: the A1 (open pit), A2, and B Zones (underground). The pre-mining resource was 54.9 Mt, including 8 Mt of sub-economic, locally silver-rich massive pyrite. In the Selbaie region, calc-alkaline andesitic volcanics form the "basement." The Brouillan Volcanic Complex formed within an islandarc setting on this regional basement. Evolution of this complex involved the formation of a felsic magma chamber and the development of a large caldera structure over the Brouillan batholith. Second- order linear and sub-parallel faults and rifts developed as a result of back-arc rifting/extension. The edges of these rifts were feeders for linear felsic volcanism (similar to fissural volcanism). During felsic volcanism, the feeder zones acted as conduits for hydrothermal fluids with associated pervasive potassic alteration. The alteration is characterized both vertically and laterally by well-defined quartz, sericite, K-feldspar and/or, locally, biotite halos, to produce a mushroom-shaped morphology. This K-feldspar alteration is not common in most other volcanic-associated ore deposits. Mafic dikes cut all of the geological units and appear to occupy earlier synvolcanic structures. Regional greenschist- assemblage metamorphism and pervasive deformation affect all units. Thrust faults moved part of the Brouillan batholith and basement units over the Mine Sequence. Although there is no relationship between the earlier mineralizing events and these late thrust faults, the thrust faults probably played an important role in location of ore lenses. Three types of mineralization are present: 1) copper-rich veins and hydraulic breccias; 2) disseminated and stringer, low-grade and high volume zinc-copper mineralization; and 3) finely laminated, massive, locally silver-rich pyrite mineralization within structural basins. At the bottom of these basins and at the contact of welded acid tuff (WAT) units, massive pyrite zones are locally enriched in zinc, and contain the possible vestiges of black smoker-like material. The ore metals were probably derived from leached basement andesitic volcanics in a hydrothermal system powered by one or more heat sources within the Brouillan Volcanic Complex. The Selbaie deposits are mainly characterized by: (1) the presence of small volcano-tectonic subsidence basins, which host chemical sediments and volcaniclastic materials; (2) pervasive potassic alteration; (3) locally high-grade silver mineralization (up to 1-2 kg/t Ag); and (4) the presence of random zones of Pb mineralization. The Selbaie deposits can be closely compared with the copper-rich Murgul deposits, which belong to the eastern Pontides metallogenetic province in Turkey. If conventional classification criteria for the volcanogenic massive sulfide deposits (e.g., Noranda, Mattabi types, and recent subsea floor deposits) are taken into account, the Selbaie deposits still exhibit many differences in terms of alteration assemblages, physical volcanology and some styles of mineralization (low-grade and large volume). Consequently, the "Selbaie" deposits belong to a new sub-type of volcanic-associated sulfide deposit, which may be used in future exploration programs."

Jan 1, 2000

By D. R. Boyle

"The Murray Brook precious metal (Au, Ag) gossan deposit is one of nine supergene mineral deposits that have developed over polymetallic massive sulfide deposits in the Bathurst Camp of New Brunswick. Reserves consist of 1.9 Mt of gossan containing 1.53 g/t Au and 65.9 g/t Ag. The supergene zone at Murray Brook consists of six distinct units: a) altered massive sulfide, b) pyrite-quartz sand, c) massive sulfide gossan, d) disseminated sulfide gossan, e) ferruginized wallrock, and f) leached bedrock. The massive sulfide gossan constitutes the main body of economic mineralization and consists of goethite, primary quartz, secondary amorphous silica, K-Fe-Pb-As- Sb-Ag hydrated sulfate and oxide minerals (beudantite, plumbojarosite, jarosite, bindheimite, scorodite), trace cinnabar, and cassiterite of primary origin. The order of stability of sulfide minerals during oxidation was pyrite _ arsenopyrite _ galena _ Bi-Sb sulfosalts _ chalcopyrite _ tetrahedrite group _ sphalerite.Two mass balance techniques (isovolumetric and conservative element) indicate elemental depletion in gossan relative to primary ore in the order: S>Cd=Zn>Cu=Mn>Na=Ca>Fe=Al=V> Mg= K=Se=Hg>Pb>Ti>Ag>Mo=P>Ba; and enrichment in the order Au>As>Sb>Si>Bi. Tin, as cassiterite, is conservative.Mineralogic and paleomagnetic data suggest that the gossan deposit formed under a warm temperate climate throughout the Pliocene. The rate of oxidation and the compositional nature of the ore was significantly influenced by: a) the position of the primary sulfide zone in a downward moving hydrological system, b) primary sulfide composition and zonation that promoted the development of a strong electrochemical oxidation system, and c) pronounced intercalation of carbonate and sphalerite mineralization in sulfide zones, which promoted rapid development of secondary porosity, permeability and downward flow of oxygenated groundwater.During progressive oxidation and physico-chemical erosion of the gossan zone, Au was transported downward in groundwaters, probably as a Auo colloid complex, to be concentrated in the lower horizons of the gossan profile. The precipitation of Au was greatly increased in the pyrite/arsenopyrite zones. Gold concentration was multi-cyclic with continual dissolution and nucleation of the metal until final concentration in the void structures of the gossan. Leaching experiments and microprobe analyses indicate that Au is present in the gossan as submicron composite sols of Au-Ag-silica."

Jan 1, 1995

By J. F. Hazzard, R. J. Chalaturnyk, C. Khazaei

"Various measurement, monitoring and verification (MMV) techniques are used to ensure the safety of operations in petroleum projects. One of these techniques is microseismic (MS) monitoring of the caprock. A challenge in MS monitoring of caprock is that unlike projects such as tunnelling in hard rocks, the number of recorded events are much smaller and also wide spread through the rock mass which makes interpretation of the physical meaning behind the events very difficult.In this paper, a numerical technique is introduced and validated for coupling a finite difference code, FLAC3D (Fast Lagrangian Analysis of Continua), with a discrete element code, PFC3D (Particle Flow Code). Then, a similar approach is adopted for modeling microseismic events in the caprock. For this purpose, the underburden, reservoir and overburden layers are modeled by FLAC3D. A rather small section of caprock above the reservoir is nulled in the FLAC3D model and substituted by a PFC3D inclusion. The reservoir pressures are then applied to the reservoir section of FLAC3D. Once the FLAC3D cycles, there will be induced pressures in the caprock due to its undrained response to the change in pressures within the reservoir. These induced pressures are transferred to PFC3D as boundary velocities. Then the PFC3D cycles and sends back the boundary forces to FLAC3D. This back and forth process continues until equilibrium is reached. During this process, there will be bond breakages within the PFC3D inclusion that can be regarded as MS events. An algorithm for recording the microseismic energies based on a change in local strains is also implemented. The results are then compared with real data. The effect of injection fluid temperature is also studied. No significant appearance of microseismic events was observed due to injection of CO2 in both cases (i.e. with or without considering temperature). However, this continuum/discontinuum approach seems promising for understanding the microseismic response of caprock in more detail and also using the MS data for validation of geomechanical models."

Jan 1, 2015

By Stanley G. Butcher

Predictions of coal cleaning plant performance from the washability data are traditionally used at the conceptual design stage of a coal preparation plant to confirm process selection. The development of computer programs which simulate the operation of a plant facilitates the optimization of product yield and quality, and ultimately proceeds. It is shown that the optimum is sensitive to changes in mine operations and market price structure. A computerized review of operations is thus recommended as an on-going activity .

Jan 1, 1979

By R. Lovat, J. A. Hunter

"The design, development, and verification of the Lovat 7.6metre diameter full-face tunnel-boring machine is reviewed. Programmatic and technical challenges are outlined with a review of the specifications and the design to meet these requirements. Subsystem designs are presented for the waste material removal, ventilation, cutter head, structural support, advance technique, water removal, and interfaces with the Donkin-Morien Mine. The techniques used to verify that the design meets the requirements is by testing in the Lovat factory and in the field. Certification of the machine for use in a methane environment is discussed.IntroductionStudies have concluded that the average annual worldwide tunnel construction is 500 kilometres at an estimated average co st of $3,400 U.S . per linear metre. The total market value of the tunnelling industry is estimated as approximately $1.7 billion U.S. per annum. Of this, the current market for tunnelboring machine excavation is approximately $270 million U.S. per annum worldwide with a further potential of $250 million if more contractors are convinced that Tunnel-Boring Machines (TBM) are more suitable than conventional techniques. The worldwide civil tunnelling market has the potential to double each year in the next 5 to 15 years. Growth has been identified in the energy and mineral resources sectors of the economies of many nations and a significant volume of machine tunnelling studies and trials are presently underway for the extraction of coal, uranium , heavy oil or oil sand fuels, metallic and non-metallic industrial minerals and base metal or rare earth ores. Further tunnel projects for regional transportation, waterpower, irrigation , high density urban transportation, storm water sewers and water supply purposes are continually being implemented with new concepts like military security facilities and underground storage schemes being considered.Lo vat Tunnel Equipment of Rexdale, Ontario, the only Canadian manufacturer of TBMs was incorporated in 1973 to manufacture so ft ground tunnel-boring machines to satisfy this growing market demand. Lovat has produced an average of 5 machines per annum during the period 1972 - 1982 and has established an international reputation for competitive costs, quality of construction, after-sales service, and reliability. As of June 1982 Lovat TBM's have been used to tunnel over 240 km in projects throughout the world."

Jan 1, 1984

By Desmond M. Levins

"Australia has almost twenty per cent of the Western World's low-cost uranium reserves, located mostly in the Alligator Rivers region of the Northern Territory. At present, only one uranium mill is operating in Australia, but a number of new mills are planned for the early 1980s.Details are given of Australian uranium mining and milling proposals and the measures taken to minimize their environmental impact. Major factors affecting environmental impact are discussed, including treatment of liquid wastes, water management, control of radon and other airborne releases, and disposal of tailings. IntroductionAustralia is entering a new phase in uranium mining and milling activity . In the first phase of operations, between 1954 and 1971, about 10,000 tonnes of yellowcake was produced at five locations. Most of the production came from the mines at Rum Jungle in the Northern Territory and Mary Kathleen in Queensland. In the 1960s, the demand for uranium slumped, and much of the yellowcake produced at Rum Jungle was stockpiled by the Australian Atomic Energy Commission. The early uranium processing operations in Australia were typical of overseas practice at that time. Environmental problems were generally given low priority and pollution control measures were unacceptable by today's standards. There was little or no recycling of process water, acid waste streams were not neutralized and tailings dams were poorly designed. At Rum Jungle, oxidation of sulphides in waste heaps, tailings dumps and ore stockpiles subsequently led to destruction of vegetation and heavy metal pollution in a nearby river.In the early 1970s, major uranium deposits were discovered in the Alligator Rivers region of the Northern Territory. Significant orebodies were also located in the Great Artesian Basin in South Australia, in calcrete formations in Western Australia and at several locations in Northern Queensland. According to latest available estimates. Australia has about 160/0 of the Western World's uranium recoverable below $US 80 per kg U. Mining these orebodies will require pollution control measures more stringent than practised previously in Australia."

Jan 1, 1980

By D. R. Boyle

"Abstract - The Murray Brook precious metal (Au, Ag) gossan deposit is one of nine supergene mineral deposits that have developed over polymetallic massive sulfide deposits in the Bathurst Camp of New Brunswick. Reserves consist of 1.9 Mt of gossan containing 1.53 g/t Au and 65.9 g/t Ag. The supergene zone at Murray Brook consists of six distinct units: a) altered massive sulfide, b) pyrite-quartz sand, c) massive sulfide gossan, d) disseminated sulfide gossan, e) ferruginized wallrock, and f) leached bedrock. The massive sulfide gossan constitutes the main body of economic mineralization and consists of goethite, primary quartz, secondary amorphous silica, K-Fe-Pb-As- Sb-Ag hydrated sulfate and oxide minerals (beudantite, plumbojarosite, jarosite, bindheimite, scorodite), trace cinnabar, and cassiterite of primary origin. The order of stability of sulfide minerals during oxidation was pyrite > arsenopyrite > galena > Bi-Sb sulfosalts > chalcopyrite > tetrahedrite group > sphalerite.Two mass balance techniques (isovolumetric and conservative element) indicate elemental depletion in gossan relative to primary ore in the order: S>Cd=Zn>Cu=Mn>Na=Ca>Fe=Al=V> Mg= K=Se=Hg>Pb>Ti>Ag>Mo=P>Ba; and enrichment in the order Au>As>Sb>Si>Bi. Tin, as cassiterite, is conservative.Mineralogic and paleomagnetic data suggest that the gossan deposit formed under a warm temperate climate throughout the Pliocene. The rate of oxidation and the compositional nature of the ore was significantly influenced by: a) the position of the primary sulfide zone in a downward moving hydrological system, b) primary sulfide composition and zonation that promoted the development of a strong electrochemical oxidation system, and c) pronounced intercalation of carbonate and sphalerite mineralization in sulfide zones, which promoted rapid development of secondary porosity, permeability and downward flow of oxygenated groundwater.During progressive oxidation and physico-chemical erosion of the gossan zone, Au was trans- ported downward in groundwaters, probably as a Auo colloid complex, to be concentrated in the lower horizons of the gossan profile. The precipitation of Au was greatly increased in the pyrite/arsenopyrite zones. Gold concentration was multi-cyclic with continual dissolution and nucleation of the metal until final concentration in the void structures of the gossan. Leaching experiments and microprobe analyses indicate that Au is present in the gossan as submicron composite sols of Au-Ag-silica."

Jan 1, 1995

By Frank S. Palkovits

Over the past 30 years, underground paste backfill systems have been implemented across the globe in many configurations, each with a primary focus of providing high quality backfill to enhance mine operations. However, a number of key design drivers are not always well understood within design engineering firms that occasionally undertake this work, leaving opportunities on the table. Perhaps not always obvious to those newly embracing paste technology, identifying key drivers and opportunities attainable through a paste backfill system is generally not straightforward, requiring innovative approaches to securing higher productivity, availability, performance, maintainability, and operator health and safety. This paper describes a number of applications and audits of paste backfill systems for several challenging mine operations. Key challenges include iterative design aspects of availability of good backfill materials, plant location and configuration, general arrangement, and binder receiving/storage systems.

Oct 1, 2010

By K. Swedburg, M. Samuels

"The expansion of the concentrator at New Gold’s New Afton copper-gold mine in British Columbia, Canada, completed in 2015, included an increase in the required retention time of the cleaning circuit. On site pilot testing of a Woodgrove Staged Flotation Reactor (SFR) had shown that a high grade copper concentrate would be produced with excellent recovery. The SFR was selected rather than conventional tank cell technology based on the much smaller footprint (which rendered a separate and expensive building extension unnecessary), high concentrate grades demonstrated in testing, and the lower energy requirement. Three SFRs, each capable of taking a nominal feed of 700 cubic meters per hour were installed and commissioned 10 months after the receipt of order. The SFRs operate in series and all of the cells produce a final concentrate typically grading 32% Cu, while the overall SFR stage recovery averages 55%. The tailings from the SFRs are treated in the original conventional three-stage cleaner circuit where the remaining values are recovered in a concentrate grading 28% Cu. Design production was achieved within days of the initial start-up of the SFR circuit.INTRODUCTIONThe New Afton concentrator, located near Kamloops, British Columbia, Canada processes a copper-gold ore with a designed head grade of 0.96% Cu, 0.72 g/tonne Au, and 2.22 g/t Ag.The New Afton Mine is a block cave mining operation. Ore is undercut from the bottom up and removed at the extraction level from a grid of draw points. Ore is trammed to the ore passes by underground loader and dropped to a haulage level for transport by trucks to the gyratory crusher. From the crusher, the ore is conveyed to the mill via a 4.5 kilometre long conveyor system. Block caving was chosen for the New Afton deposit because the underground infrastructure could be built below the historical open pit of the Afton Mine (a previous operation of Teck Resources) and this method is favorable to large-scale low-cost mining.The New Afton deposit is a copper-gold, alkalic porphyry system. Hypogene mineralization is characterized by discontinuous copper sulphide veinlets and disseminations, principally chalcopyrite and minor bornite, along with pyrite as the second most dominant sulphide. Gold particles vary in size from 5 µm to 40 µm and occur as native gold and electrum, associated mostly with the chalcopyrite grains and never with the pyrite. In some instances, a second alteration phase has resulted in the copper sulphides being replaced by tennantite-tetrahedrite locally and along faults that transect the mineralized body. The design head grade of arsenic is 244 PPM, although the presence of tennantite is inconsistent and can vary from trace levels to 15% of the total copper. No arsenopyrite is present in the hypogene ores. Supergene mineralization, consisting of native copper with accessory chalcocite occurs in minor amounts along faults and highly oxidized near-surface portions of the deposit."

Jan 1, 2016

By Lluís Fontboté, François Lieben, Robert Moritz, Massimo Chiaradia

"Abstract - The Las Cañas stratabound Pb-Zn deposit, in northern Chile, is hosted by the Lower Cretaceous back-arc marine carbonate and subordinate andesitic volcanic and volcaniclastic rocks of the Chañarcillo Group, one hundred meters above a thick pile of magmatic arc-related basaltic to andesitic lavas of the Bandurrias Formation. The deposit is not obviously related to local intrusive rocks, which include an Upper Cretaceous granodiorite batholith and dacite dikes emplaced along normal faults. Stratabound Pb-Zn-Ba mineralization is constrained within several porous stratigraphic units, including a 50 cm thick lapilli-tuff and less well mineralized algal-laminated limestone. Veins that locally carry some Pb-Zn occur along normal faults that displace the stratabound orebodies, and this study shows that they represent a different type of mineralization.Fluid inclusion microthermometric data for ore-stage quartz and barite indicate saline fluids (6 to 30 wt% NaCleq) and a formation temperature in the range of 80°C to 160°C for the stratabound mineralization. Two types of fluid inclusions occur in the veins. The type I vein fluid inclusions indicate less saline (average 7 wt% NaCleq) and slightly higher temperature fluids, in the range of 110°C to 220°C. The type II vein fluid inclusions indicate highly saline fluids (25 to 40 wt% NaCleq) which might be related to minor copper mineralization.206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios for galenas from the stratabound mineralization, with mean values of 18.42, 15.59, and 38.25, respectively, fall within the range of stratabound polymetallic deposits of northern and central Chile, and indicate a Lower Cretaceous magmatic rock source. Galenas from veins have slightly more radiogenic 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios, with mean values of 18.47, 15.61, and 38.34, suggesting two distinct episodes of mineralization.?34S values for galena and barite range from negative values (-31.2‰ to -12.5‰ and -7.7‰ to +12‰, respectively) in the mineralized tuff to higher values in the algal-laminated limestone (-2.5‰ to +1.2‰ and +13.2‰ to +17.4‰, respectively), close to Lower Cretaceous marine sulfate values for barite, and homogeneous values for the galena from veins (-12.0‰ ±1‰). Changing redox conditions can partly account for ?34S variations in the tuff. Sulfur sources include magmatic rock sulfur (-1.5‰ to +9.7‰) as well as sedimentary sulfides and marine sulfate."

Jan 1, 1999

By Mario Giavani

"IntroductionBy the 1980s, the continuous casting process had almost replaced the ingot casting of steel in Japan, Europe and North America. While economic benefits were probably initially the prime motivator, the transition rapidly proved that continuous casting in conjunction with ladle metallurgy offered a much greater degree of process control and made possible routine steel specifications not previously available.This new technology demanded improved procedures for the quantitative addition of the required metallurgical reagents, especially as regards the more volatile or toxic elements such as calcium , boron, carbon, sulphur, lead and tellurium. The injection of a thin steel tube containing the additive into the metal bath of a ladle refining station offers the best procedure for this. In the industry this has been referred to as ""Cored Wire "".Operators using this technology find that they are faced with balancing the injection speed against the small cross section of the tube to feed the required amount of reagent within the short time span available to the operation. Large-ladle shops requiring major quantities usually resort to multiple machines and high speeds. Many machines approach a maximum feed rate of 400 m/min. Higher speeds exceed the melting rate of the system, and the ferro static buoyancy of the tube will cause it to coil up the ladle wall and possibly resurface into the slag layer, and even eject itself above the surface. Under these conditions, exact control of element recovery becomes difficult, especially with the commonest addition, calcium silicon alloy.Many experts are persuaded that the final melting position of the carrier tube has major importance in establishing consistent element yield to the bath.For instance, the vapour pressure of calcium at l500 °C is close to I bar. Reaching a melting depth sufficient to accommodate this value is considered to be critical to achieving an acceptable and reproducible yield.Many studies have elaborated semi-empirical formulae to establish the melt zone depth, connecting this value essentially to the diameter of the tube , the injection rate and the superheat of the steel. The author's experience in steelmaking could not confirm such formulae in many cases, and he set about to develop a mathematical model which would be useful in addressing this problem, taking into account the several parameters which will regulate the behaviour of a filled tube immersed in molten steel."

Jan 1, 1991

By P. Espinoza, I. Yutronic, J. Olivares

"Compañía Minera Doña Inés de Collahuasi's (CMDIC) Concentrator Plant is located at 4300 meters above sea level, approximately 2000 kms north from Santiago, Chile. The concentrator has three grinding lines. Each one, Lines 1 and 2, have one SAG mill at the primary grinding stage followed by a secondary grinding and classification stage consisting of one ball mill, two hydrocyclone batteries and a sump with two pumps. Line 3 has one SAG mill (Gearless Mill Drive), followed by a secondary grinding and classification consisting two ball mills, four hydrocyclone batteries and a sump with four pumps. Average throughput for these three lines is 150 Ktons per day. Peak values of 180 ktons per day have been achieved.Since late 2008 and throughout 2009 and 2010, Operations and Automation areas developed an optimization program for the grinding process, considering the implementation of Model Predictive Controllers (MPC) for the three SAG mills, and later, extending MPC to the secondary grinding and classification stages. The implementation of a MPC solution was based on stability considerations (high variability of the SAG process, high interaction between sump level control and classification efficiency, etc), requirements for an automated and consistent operation, the need to maximize throughput under timevarying scenarios and, in the long term, optimization of grinding process considering Specific Energy Consumption, among other parameters. MPC solutions had proven control robustness and strong optimizing capabilities in terms of helping in discovering new operational points and so achieving all of the aforementioned goals.On the first stage of the program, MPC implementation considered identification of dynamical process control models based mainly on historical data, in order to know the impact of a group of Manipulated Variables over Controlled Variables. Also, the impact of measured Disturbance Variables was modeled in order to take into account the high impact and interaction of these variables over the processes. At the end of this stage, 4 controllers were successfully operating for the 3 SAG mills and the secondary grinding and classification process. In response to challenges made by the working group, the second stage of the development of control applications in the grinding process required to achieve a design and implementation of a solution capable of governing the milling process, in addition to stabilization and optimization of both processes (SAG milling and secondary grinding), to integrate from a point of view of process control and automation. Therefore, in the second stage, MPC performance was continuously monitored and optimized through advanced tuning, inclusion of more process models (with proper step tests), redefinition of specific optimization criteria and adjustment to new process needs.Finally, successful MPC implementation at Collahuasi has proved that fast development and deployment of process control solutions is possible and allows immediate process stability, higher throughput, specific energy consumption reduction, and successful product size control, among many others."

Jan 1, 2012

By S. S. Rahman, A. Gholami, M. A. Aghighi

"This paper provides a foundation for studying the growth of fractures in presence of other discontinuities and different anisotropies of low permeable hydrocarbon formations and helps to improve the design strategies for multistage fracturing.The multistage fracturing technology has recently been used to exploit low permeable hydrocarbon reservoirs. However, the mechanism of hydraulic fractures interaction and the impact of local heterogeneities on ultimate trajectory of the growing hydraulic fractures are not yet understood in depth. A fully coupled poroelastic Finite Element based model is developed to investigate the mixed mode propagation behaviour of growing hydraulic fractures. This model takes advantage of an explicit representation of the fracture which enables us to take the effects of rock and fluid related parameters into account. Moreover, impact of fracture geometry and leak-off phenomenon is investigated. The refined mesh around the crack provides the added advantage of more detailed stress distribution, pore pressure change and back stress in the vicinity of the fracture and in particular at the fracture tip. The potential deviation propensity of the fractures is evaluated based on the fundamental rule that fractures propagate perpendicular to the direction of the minimum horizontal stress.This study shows that pressurization of transverse hydraulic fractures results in the reorientation of local principal stresses, particularly in vicinity of fracture tips. Variation of flow patterns clearly influences the evolution of shear stress around the fracture tips which will potentially lead to mixed-mode I and II fracturing and consequently, fracture deviation. The presence of local heterogeneities such as preexisting fissures and/or fractures is a main source of such pore pressure induced stress redistribution and reorientation and potential deviation of hydraulic fractures.Most existing models ignore or simplify the effect of pore pressure/stress coupling as well as the fracture geometry and fluid flow within the fracture. Also, the fluid leak-off from the hydraulic fracture into the formation, which is a controlling factor in fracture growth, is often considered using analytical models. Taking advantage of a fully coupled porelastic model along with an explicitly discretized fracture, this study provides a more realistic insight into the complex fracture propagation processes of multistage fracturing operations particularly in presence of reservoir geo-mechanical complexities."

Jan 1, 2015

Objectives ? New deposits can be found in mature Mining CampsNew Camps ? Volcanogenic Massive Sulfide (VMS) deposits ? polymetallicpolymetallicexamples are desirable exploration targets examples ? Genetic and exploration models for VMS deposits are robustrobust ? subtle but important differences exist between deposits and districts ? sometimes ??neglectedneglected??in resource modeling and exploration efforts ? ReRe-evaluation of a prominent existing camp is rewarding ? update on the exploration strategies currently being applied on a practical level The Falconbridge-Alexis approach includes GoCAD modelling

May 1, 2006

By V. S. Gischig, G. Preisig

Hydraulic stimulation of deep reservoirs is an essential procedure for developing engineered/enhanced geothermal systems (EGS), but also in other Geo-energy contexts. The goal is enhancing permeability to such a degree that fluid flow rates within the reservoir are sufficiently high for an economically productive reservoir. Two fracture stimulation mechanisms are distinguished that may occur concurrently during the hydraulic treatment: 1) During hydro-fracturing (HF) new tensile fractures are propagated from the borehole by means of a fluid pressure overcoming the minimal principle stress d3 plus the tensile strength T0 of intact rock. In case of a pre-existing fracture oriented normal to d 3 , the fracture can be opened by exceeding d 3 only. Fluid injection is performed via small packed intervals for creating a stack of hydraulic fractures. 2) During hydro-shearing (HS), over-pressure induces slip along pre-existing fractures that are favourably oriented in the stress field for reactivation in shear. Such stimulation is usually performed in a large packed interval or in an open borehole. Which mechanism occurs predominantly during stimulation depends on the rock mass structure and in-situ stress field, but also on the orientation of discontinuities intersecting the open-hole section and thus being pressurized. Both mechanisms also differ in how they affect fracture permeability. While permeability gained by HS is mostly irreversible due to rearrangement of asperity contacts accompanied with shear dilation, permeability enhanced during HF reduces nearly reversible after pressurization unless proppant is used to ensure permanent apertures. In this contribution, we critically discuss the pros and cons of both mechanisms regarding efficiency of enhancing permeability and the associated hazard of induced earthquakes based on literature review and numerical modelling. We review literature that reports on how much permeability required for productive EGS reservoirs and how much permanent permeability can be gained by stimulation. We also compile information regarding the degree of seismicity induced during HFor HS-dominated stimulation procedures, together with conceptual studies that reveal characteristics of seismicity associated with the two mechanisms. Many observations and models indicate that HF may have a higher tendency of being aseismic, while felt seismic events are usually associated with HS. Further, we present a hydro-mechanically coupled fracture flow model that investigates, if and to what degree the stimulation strategy can be designed such that one of the two mechanisms is evoked and dominates over the other. It shows that HS may dominate in presence of larger persistent fractures nearly optimallyoriented in the stress field, even if HF is attempted in short packed intervals. The model further demonstrates that stress transfer during HS promotes the development of permeability across an anisotropic layer of the stimulated rock instead of a large volume. Hence, the study sheds light onto the feasibility of creating productive EGS reservoirs in crystalline rock at several kilometres depths.

Jan 1, 2015

By T. Negeri, M. Boisclair

"A hybrid process consisting of flotation and magnetic separation has been developed to concentrate multi-phase rare earth minerals associated with a carbonatite ore that contains a significant amount of niobium. Fine grinding to a d80 of <65 microns was required to obtain acceptable separation of 92% of the contained total rare earth oxide (TREO) and niobium in half the feed mass. Whereas it was possible to obtain 85% of TREO in 28% of the feed mass through staged cleaning, it was demonstrated that at least 87% and 85% recoveries of TREO and Nb respectively could be achieved in 16% of the feed if the rougher-scavenger concentrates were calcined, quenched, reground to <25 µm and then magnetically upgraded. The paper discusses the overall concept of the flowsheet and the experimental strategies that led to this progress. INTRODUCTIONOut of the approximately 250 minerals known to contain rare earth elements (REEs), only about 60 of them contain REEs in significant amounts. Over 95% of the world’s rare earth oxides (REOs) are believed to occur in the form of three minerals (Pradip & Fuerstenau, 1991) namely bastnaesite (Ce,La,Y)CO3F, monazite (Ce,La,Nd,Th)PO4 and xenotime Y(PO)4. An estimated 51.4% of global REO resources are hosted by carbonatite deposits with the same three minerals as major constituents (Weng et. al., 2015). Any one of the REEs or commonly all of them can be found in these minerals (Ravnaas, 2010). As the demand for critical REEs increases due to the ever increasing applications in advanced technologies, many deposits containing other forms of REE minerals will have to be developed. REE minerals are extensively dispersed and intergrown with several oxides, silicates, carbonates, and phosphate minerals. Consequently it is possible to liberate them only at fine grinding and is thus difficult to separate and produce high grade rare earth mineral concentrates. Most of these minerals contain other important elements such as tantalum (Ta), niobium (Nb), uranium (U), and thorium (Th) in varied quantities. REE minerals in the same ore may exist as carbonates, fluorocarbonates, niobates, silicates, phosphates etc. in association with gangue minerals belonging to different mineralogical groups."

Jan 1, 2016

By G. Danha, S. Wabula, D. Glasser, D. Hildebrandt, N. Hlabangana

"Impact tests on single particles or a bed of particles are used to determine the fracture characteristics of particles. Many different techniques have been adopted in comminution in order to find ways of optimizing energy consumption in the size reduction process. In this paper, we apply one such method called the Attainable Region (AR) analysis technique to optimize the impact energy on a bed of silica particles. The attainable region is a fundamental approach that is equipment-independent and can be used to analyze breakage processes. The AR is defined as a set of all possible outcomes, for the system under consideration that can be achieved using fundamental processes operating within the system.INTRODUCTIONThe energy crisis in Southern African has reached such critical levels, that most cities in countries like Zambia, Zimbabwe, Lesotho, Swaziland and even South Africa are experiencing load shedding challenges lasting sometimes up to 18 hrs a day. Southern Africa is well known for its riches in mineral resources, and the economies of most states in this region are driven by the mining & mineral processing sector. With the emergence of small scale miners due to government empowerment policies, national energy providers have had to resort to power cuts mainly to domestic users in a bid to cope up with the huge industrial electricity demands.It has been estimated that about 4% of the total energy used in the world is consumed by the mineral processing sector (Fuerstenau & Lutch, 1999). Tomanec and Milovanovic (1994) estimated that milling alone accounts for more than 50% of the total power used in mineral processing, but this can rise to as high as 70% for hard or finely dispersed and inter-grown ores. Today, the greatest challenge in mineral processing is how to optimize energy input to the size reduction process (Dey & Das, 2013; Nomura & Tanaka, 2011), where it has been observed that only a small percentage (1.5%) of the total energy input really does the breaking (Khumalo et al., 2008) while the rest is consumed by the equipment concerned and lost to contacts that do not result in breakage. The immediate benefits of focusing research on the optimization of energy in size reduction operations in the mineral processing sector lies in potential savings on industrial electricity usage that may then be directed towards domestic users."

Jan 1, 2016

By G. Girard, A. Larouche, J. Colbert, G. Doyer

"The Direct Chill (DC) casting process uses water to extract heat from molten aluminium and helps to control the solidification process. Many factors such as the water flowrate, water distribution around the mould and water impingement angle have significant impacts on the solidification process. It has been noted that the chemistry variation of the cooling water is also an important factor that has a major impact on the presence of defects on the ingot. A significant change in the water quality can produce defects on the ingots such as cracks, bleedouts, or runouts. Understanding the impact of water quality variation on ingots is therefore essential to ensure good ingot production and reduce defects. This paper aims at describing a new approach to follow the variations of process water quality over time. It is an original and innovative method, which is still under progress. A water quality and stability index (WQSI) is under development to evaluate changes in the water composition based on water physico-chemical parameters. The index is calculated by comparing each of the actual parameters with historical values previously modeled by a statistical law. It is a dimensionless number having an adjustable weight factor for each parameter. The positive or negative contribution of each parameter, with respect to the water cooling capacity, is taken into account to calculate the WQSI. The current selection of parameters is based on knowledge from the literature as well as on empirical experience. When the developed tool will be mature, it could be used to track water variations upon time and anticipate problems, enabling proactive actions to ensure good ingot production.INTRODUCTIONFor many years, the impact of water chemistry on heat transfer, during DC casting, has been of great interest in the aluminum industry. Several papers have been published to demonstrate the correlation between water chemistry and heat transfer (Yu, 1985), (Gildemeister, 2014). Although numerous studies do present the effects of water parameters (i. e. hardness, conductivity, oil, and grease…) on cooling capacity under controlled experimental conditions, they do not reflect the strong interactions between the parameters and variations present in a casting center. Wells and Cockcroft also demonstrated that laboratory based studies are not fully representative of real heat transfer in an industrial casthouse, there are too many factors involved (Wells, Li, & Cockcroft, 2001). In this context, it becomes very difficult to obtain a quantifiable relationship between the capacity of water to cool the ingot and ultimately the performance of the cast."

Jan 1, 2016

By J. A. E. Bell

"Inco has shifted part of its traditional extractive research effort at its J..Roy Gordon Research Laboratory in Mississauga toward new, value-added products. Most of the effort is being expended on new Ni powders for batteries and new Ni-coated products which will be produced in Inco&apos;s carbonyl nickel refineries. New products under development are Ni-coated powders, Ni-coated fibres and ultra-fine Ni powders. Other new products for advanced material applications include controlled expansion composites, NiGOLD strip, Thermal barrier coatings on Inco alloys, and plasma coatings.Research and Corporate Strategic ThrustsThe newest strategic thru st of the company is to increase the value of the primary metal products. These new products are to be in addition to any new alloys or downstream alloy fabrication.Historically Inco has had the highest research expenditures in the extractive metallurgy field in North America. This has resulted in many new processes including flash smelting , matte separation, fluid bed roasting, pressure carbonyl refining and cobalt electrowinning which have contributed to establishing Inco as the lowest cost nickel producer. The recession of the 1980s caused a restructuring of Inco research and corporate goals .As shown in Figure I, from 1975-1982, i.e. pre-recession, Inco spent around 33 million dollars per year on research. Some 48070 of that sum was spent in Corporate Laboratories in Sterling Forest in the United States and in the United Kingdom , mostly on alloy associated research. A further 10% was spent on alloy research at the alloy production facilities in Hunting- ton, West Virginia, and Birmingham and Hereford in the United Kingdom. On extractive research, 13% was spent by process technology groups at the plant s, 20% at the pilot plants in Port Colborne and 9% at the J. Roy Gordon Research laboratory.The relative research expenditures (Fig. 2) have decreased so that today they are at the same level as 1975-80. The research as a per cent of sales has been cut from 2.2% to 1.2% of normalized sales. A normalized sale price of $4.00/lb Ni was used in the 1988 figures. This was partly achieved by closing Corporate Laboratories. Most of the essential alloy research was moved to producing plants and total alloy research is now 27%.A new thrust initiated in the 80s was mining research which now accounts for 20% of research expenditures. Over a period of the past five years this research has doubled the mining productivity in Inco. The pilot plant expenditures have been cut in half. One entire research station at Port Colborne was converted into a platinum group metals intermediate refinery. The decrease in pilot plant expenditures has been compensated by full scale plant trials devoted to the S02 abatement program at Sudbury."

Jan 1, 1990

By A. Diaz, Minera Los Pelambres, C. G. Salinas, G. Leinenweber, F. Diaz, D. Rojas, R. Bernal, O. Jimenez

"Los Pelambres Mine (MLP) is located in the IV Region of Chile, a semi-arid region where water plays a key role in operations as a scarce resource and is vital for the sustainability of human life, animals and ecosystem. The conventional flow meters installed on pipes at MLP can fail to provide an accurate measurement due to corrosion and/or fouling on the inner wall or presence of elements in the water such as acids, salts and suspended solids. Conventional flow measurement methods require the inner diameter to be known, however it is not always possible to assess its real value due to scaling, fouling, corrosion, etc. Here we present a novel methodology to solve these problems, which consists of the measurement of flow by a method that does not require the internal area of the pipes: the fluorescent tracer dilution method. In addition, the fluid velocity can be determined by the transit time of a radioactive tracer method. With the flow rate and velocity, the equivalent area is determined and thus the equivalent internal pipe diameter as well. This methodology was applied in a recirculation pump station, for mineral processing from the El Mauro tailings dam.This work demonstrated adequate correlation between measurements from fluorescent tracers and velocity measurements from radioactive tracers, both of which lead to the assessment of the internal diameter of pipes with scaling. The results of both methods disagree with the data provided by the flowmeter installed on the line due to its miscalibration. This information is useful in validating and correcting the information provided by online flowmeters of all water and solutions transport processes in filled pipes.INTRODUCTIONPresently, the need to optimize water resources is increasingly ever important, due to various reasons such as water scarcity, community empowerment, an increased use of water for mining processes and environmental considerations. Taking into account those main considerations, Los Pelambres Mine decided to focus on water conservation to avoid losses of this vital element. They decided to demonstrate that all of the systems that used water (flow meters, pipes, pumping stations, lagoons, etc) were in good condition and that no evitable loses of this important resource occurred. A plan was proposed to conduct a “hydraulic assessment” of fluid flux and water speed at different points and courses at the mine, with the purpose of obtaining hard data to support, verify and correct the information provided online from specific instrumentation dedicated to those purposes. The final goal was to manage the water resource basin in a sustainable way, based on cross-checked information. The chosen points are representative of the processes present in the mine, such as recirculating water stations at different operating conditions and surface water courses, where the fresh water capture systems operate."

Jan 1, 2016