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By Jiuhua Xu, Yuling Xie, Fenglei Bie, Neng Jiang

"Abstract - The Xiaoqingling Mt. area is one of the most productive gold districts in China. The gold-bearing quartz veins are controlled by a series of east-west shear zones within the Archean Taihua Group, and related to the late Yanshanian (Cretaceous) granite. The major metallic minerals are native gold, electrum, pyrite, galena, chalcopyrite and sphalerite, with gangue minerals dominated by quartz, sericite, ankerite, and calcite. The host rocks are mainly amphibolite, plagioclase gneiss, and migmatites. Principal alteration is sericitization, silicification, pyritization, and carbonization.There are four generations of hydrothermal quartz in altered rocks of gold deposits. The earliest generation of quartz, (Q1), occurs in altered amphibolite gneiss and migmatite, and typically contains fluid inclusions with halite crystals (type A) and two phases, (L+V), of fluid inclusions (type B). The salinities of type A inclusions are 32 wt% to 52 wt%, with dissolution temperatures of halite crystals being from 155°C to 465°C. The second generation of quartz, (Q2), occurs as a fine-grained aggregate associated with sericite, and has small (less than 3 µm) type B inclusions. The third generation of quartz, (Q3), occurs in mylonitic, intensively altered rocks and specially beresite (a type of rock composed of quartz, sericite, and pyrite) near the veins, and contains large amounts of CO2-rich fluid inclusions (type C-fluid inclusions with liquid CO2 and type D-fluid inclusion with high density CO2). The CO2 contents of type C range from 72.6 to 87.4 mol% in gas phases, and 35.7 to 68.3 mol% in liquid phases, based on Laser Raman analysis. The homogenization temperatures of fluid inclusion type A and C are from 215°C to 380°C, and from 210°C to 325°C, respectively. The minimum trapping pressure of fluid inclusions is estimated as 80 MPa to 170 MPa for type A, and from 57 MPa to 190 MPa for type C, which approximate to those of fluid inclusions in vein quartz.The ?18O of quartz are from 10.4‰ to 11.0‰ for Q3 of altered rocks, and from 10.7‰ to 12.8‰ for stage I quartz. The calculated ?18O of fluid inclusions varies from -1.3‰ to 6.0‰. The ?D of fluid inclusions ranges from -67‰ to -59‰ and from -81‰ to -48 ‰, respectively. It is concluded that the water in the hydrothermal fluids both reacting with wallrocks and precipitating orebodies could have been mainly of magmatic and/or metamorphic nature. However, local meteoric water might have been important in late mineralization, because of a distinct oxygen-shift toward the meteoric water. The ?34S values for pyrite of the ores range from -7.1‰ to +7.1‰, with an average of +2.9‰. Those of other sulfides (chalcopyrite, galena, and sphalerite, range from -12.5‰ to 8.3‰. The ratios of lead isotopes for galena of the ores are: 17.06 to 17.31 (206Pb/204Pb), 15.43 to 15.74 (207Pb/204Pb) and 37.58 to 38.45 (208Pb/204Pb). In summary, ore-forming fluids in the Wenyu-Dongchuang gold deposits may have originated from a mantle and/or lower crust source, and ore materials were derived from the Precambrian basement, the Taihua Group."

Jan 1, 1998

By J. W. Senn

A magnesium alloy modeled after commercial alloy WE54 was thermomechanically processed and characterized to understand the mechanisms by which its texture can be randomized, as reported by Ball and Prangnell [1]. Samples were deformed in plane strain compression to prescribed strain levels at temperatures high enough to prevent cracking and then recrystallized. The deformation texture is very similar to that observed after plane strain compression (e.g., rolling) of other Mg alloys, such as common AZ31. However, the texture can radically evolve during recrystallization. Annealing above the precipitate solvus temperature results in a nearly random recrystallization texture where the initially strong basal texture is completely eliminated. Annealing below the solvus temperature produces a recrystallized texture similar to conventional Mg alloys, i.e., a weakened basal texture. If this same material is then annealed above the solvus to promote grain growth, a randomized texture evolves, which is similar that of samples simply recrystallized above the solvus. It is hypothesized that a sort of preferred growth mechanism, whereby grains with random orientation grow faster than those with the original basal texture, contributes significantly to the texture randomization observed in wrought magnesium alloys containing rare earth elements.

Jan 1, 2006

By Matthew A. Baumann

Tooth wear on mining shovels presents a challenge for productivity. A shovel with worn teeth suffers from increased digging forces, longer fill times, and an increased likelihood of lost or broken teeth and adapters. Efficient maintenance planning relies on knowledge of tooth decay rates and patterns. A fully automated wear monitoring system can record detailed logs of tooth wear, permitting G.E.T. personnel to optimize maintenance scheduling. Studies have demonstrated that planned tooth change-outs result in significantly reduced costs as compared to unplanned maintenance. A machine-vision-based tooth-wear monitoring method is introduced. A rugged camera is installed on the boom of cable shovels, or on the stick of hydraulic shovels. The images are processed using a photogrammetric algorithm to determine the individual tooth lengths. Tooth length data is collected at intervals during shovel operations, forming a profile of the current wear state, speed of decay, wear pattern, and expected lifespan of teeth. A case study in a South American mine on a Komatsu PC8000 hydraulic front shovel is presented. Tooth wear is tracked over a 6-day period and wear rate statistics are computed for 6 teeth. This validates the system and provides an example of how wear patterns can be recorded and analysed by an automatic system. Armed with this data, mine personnel can reduce the cost and lost time due to unplanned maintenance, and observe the effects of mine conditions and operator behaviour on tooth wear.

May 1, 2011

By J. T. Kalala

Particles for heap leaching in conventional circuits are prepared using Cone crushers. Cone crushers are used to crush the ore to the size range between 12-25 mm for heap leaching operations. Leaching from these relatively coarse particles occurs only at the surface and in subsurface regions, which are accessible from the surface by cracks and pores. Since leaching is active in accessible areas, the method of comminution that forms multiple cracks and pores would offer an advantage for heap leach. An investigation was performed in this study to assess if the HPGR forms more cracks and pores than a Cone crusher. X-ray computed tomography (CT) was used to characterize the degree of cracks and pores formed by these two comminution devices that can be used for heap leaching feed preparation. In order to compare the effect of the comminution method on crack network generation, a bulk sample of the zinc ore was crushed by the HPGR at three different pressure settings (45, 95 and 120 bar), the sample ore was also crushed with a Cone crusher for comparison purposes. Products from the Cone crusher and HPGR experiment were then screened into five size fractions ((-25 +19), (-19+16), (-16+9.5), (-9.5+5), (-5+4.75) mm), Subsamples from the ((-25 +19), (-16+9.5), (-5+4.75) mm) size fractions were analysed. The spatial distribution of the crack network of sphalerite particles was characterized using a highresolution industrial X-ray CT system. This paper describes the use of image analysis techniques including image segmentation, which uses a combination of thresholding and other methods to characterize and quantify crack and mineral dissemination in the sphalerite particles after comminution with the HPGR and Cone crusher. The results are validated with those obtained using traditional techniques such as physical gas (with N2) adsorption, mercury intrusion porosimetry, SEM and QEMSCAN.

Jan 1, 2012

By M. H. Leite, R. Corthésy, D. E. Gill

"La connaissance des contraintes naturelles qui prévalent dans les massifs rocheux est un prérequis indispensable pour la conception sécuritaire et économique des excavations comme on en retrouve dans les exploitations minières souterraines. Certains chercheurs se sont attardés à colliger les résultats de mesures de ces contraintes et les ont utilisés pour produire des modèles de prédiction basés sur leur traitement statistique. Ces modèles de prédiction sont très populaires auprès des exploitants miniers puisqu’ils permettent, du moins dans les étapes préliminaires de design, d’obtenir de façon s’apéconomique mais approximative, une partie des paramètres dont ils ont besoin. Dans le cadre d’un projet initié en 1994 avec la collaboration de l’IRSST, il a été décidé de produire un modèle de prédiction englobant une partie de la zone périphérique de la faille de Cadillac, soit une zone plus restreinte que le Bouclier Canadien utilisé jusqu’ici comme région pour l’élaboration de tels modèles. Pour produire ce modèle de nouvelles données obtenues avec une technique permettant d’exercer un excellent contrôle de qualité ont été ajoutées à celles déjà disponibles. Une telle régionalisation des données de base permet d’obtenir un modèle où les intensités et les orientations des contraintes principales sont beaucoup moins dispersées que ce que rapportent les modèles publiés jusqu’à ce jour. Enfin, il est démontré que le modèle proposé pour la région étudiée est en toute probabilité plus sécuritaire que les modèles plus généraux publiés à ce jour. Knowledge of the in situ state of stress existing in a rock mass is essential to the safe and economical design of underground mining excavations. Prediction models have been published, based on the statistical treatment of stress measurement results. Such prediction models are very popular among mine operators because they allow them, at least at a preliminary design stage, to economically obtain part of the information needed, even if this information is approximative. In 1994, a research project financed by IRSST was initiated aiming to produce a prediction model that would comprise a peripheral zone around the Cadillac fault. This region is more confined than the Canadian Shield on which the existing prediction models have been based up to now. In order to produce such a model, existing stress measurement results have been used in conjunction with new stress measurements that have been performed based on a technique which allows full control of the quality of the measurements. Restricting the data upon which the model is based to a more specific region gives a model in which the intensities and the orientations of principal stresses are far less scattered than the results published to date. Finally, it is shown that the proposed model is probably safer for the studied region than the models previously published."

Jan 1, 1998

By Ainul Akhtar, Steve Cockcroft, Daan Maijer, Carl Reilly, Lu Yao, Jun Ou

A coupled thermal-fluid flow-multicomponent model has been developed to aid in understanding the melting/dissolution behavior of solid Al-rich Material (TiAl) in a liquid titanium pool produced by an electron beam. The model is capable of accounting for the significant phenomena present affecting heat, mass and momentum transport including thermal and compositional buoyancy and Marangoni forces, Darcy attenuation, evaporation, melting and solidification, and the associated release or absorption of latent heat. The modeling results have indicated the compositional fluid flow driving forces (compositional buoyancy and Marangoni forces) contribute significantly to the melting/dissolution process. The model is waiting for validation against empirical data.

Jan 1, 2014

By Stephen C. Tadolini

"The use of a torque wrench to establish the amount of actual load developed on an expansion anchor bofting system dates back to work completed in the early 1950s. The advent of ultrasonic measurement systems and hydraulic torque wrenches has made it possible for the U.S. Bureau of Mines to perform torque-tension measurements in the laboratory and the field much more accurately. The results indicate that the amount of initial boft preload may be overestimated by amounts in excess of 45% of the expected load using torque wrenches. This inaccuracy is primarily due to the friction that occurs between the bearing plate and the head of the boft. These parameters become extremely important when the support system is being used to prevent joint members from slipping relative to each other or when the boft acts as a heavy spring to clamp two or more sections together. Methods to overcome the frictional losses are presented in conjunction with a laboratory method to determine the actual torque-tension ratios for expansion anchor and combination bolting systems.IntroductionMechanically anchored roof bolts have been widely used in the mining industry since their introduction in 1947. Estimates made in 1989 indicate that out of 85 million fixtures, approximately 49 million bolting fixtures still use applied tension to complete the reinforcement necessary to maintain stable openings. Nearly 85 million bolts are used yearly. The most widely used bolt is the resin-anchored headed rebar, followed by standard mechanical roof bolts, specialty bolts (mechanically anchored, resin enhanced fixtures) , and combination bolts . Po st-tensioned resin rebars, combination systems, and friction stabilizers make up the remaining 10% of the units used (Fig. I).For mechanical, combination, and tension rebar bolts, the bolt tension is the primary means of reinforcing the roof, but in many cases, because of poor installation procedures, the bolts are ineffective. Mine operators recognize the importance of proper installation procedures. Long-term bolt tension measurements are required in the Code of Federal Regulations (CFR)In each bolting cycle, the actual torque or tension of the first tensioned bolt installed with each drill head shall be measured immediately after it is installed. Thereafter, for each drill head used, at least one roof bolt out of every four installed shall be measured for actual torque or tension. If the actual torque or tension of any roof bolts measured is not within the range specified in the roof control plan, corrective action shall be taken."

Jan 1, 1991

By Rob Assabgui

Presentation Overview ? Stobie Mine Sublevel Cave Background ? Elevated Silica Levels ? Silica Control ? Challenges and Issues ? Conclusions

Oct 1, 2010

By Peter Cunningham

Teck Facts and Figures ? Employ more than 14,000 around the world, includes: ? Over 8,600 in Canada (close to 7,800 in British Columbia) ? Close to 2,000 in Chile ? Over 2,700 in Peru ? Approximately 600 in U.S. ? Hundreds more in exploration around the world ? Total capital expenditures ? $1.8 billion for 2012

Aug 1, 2013

By Lawrence Devon Smith

"The concept of risk is well established in the mining industry. It is acknowledged when estimates of reserves are expressed as proven or probable, when mining and metallurgical recoveries are applied to the ore, and when contingencies are added to costs. However, it is difficult to provide a quantitative assessment of risk. The significant sources of risk in a mineral project and how these are addressed in project evaluations are discussed.The discount rate is examined as a fundamental means of reflecting risk in discounted cash flow evaluations. Current industry practice is discussed, and a methodology for the analysis of risk levels is proposed that assesses the constituent components of the discount rate: real interest, mineral project risks, and country risk.IntroductionThis paper examines the components of the discounted cash flow discount rate and proposes a method of estimating project-specific discount rates. The motivation for this work comes from experience of project evaluations in which owners and purchasers had agreed on virtually every aspect of the evaluation except how much the project was worth. Agreement was reached on reserves, grade, recovery, capital costs, operating costs, taxes, and, by combining these components, even on the final cash flow values. The only difference in opinion concerned the discount rate to be used in the calculation of the net present value. Depending on the life of the project, such differences of opinion can cause a variation of more than 50% in the value placed on a project! This is illustrated in Figure I."

Jan 1, 1995

By Leon C. Botham

?? Review of Requirements ?? Components of Modeling ?? Water Management ?? Tailings Management ?? Primarily a water management problem ?? Solids relatively easily contained ?? Process flows and runoff a continuous stream over life of mine ?? Need to allow this to safely happen over wide range of conditions

May 1, 2008

By C. C. Li

The D bolt is a new type of energy-absorbing rock support element recently developed in Nor-way. The D bolt is not only able to accommodate large rock deformations, but can also provide a load-bearing capacity as high as that of rebar bolts. Furthermore, the anchoring quality of the D bolt is similar to rebar bolts because of its multi-point anchoring design.

May 1, 2009

By M. Silver, R. H. McCorkell

The effects of covering materials on radon emanations from uranium mine mill tailings were investigated. Granular materials with air in the spaces allow radon to pass freely. Moist covers of compost or soil decrease radon emanation from tailings. Water-saturated covers were more effective, and freezing the tailings with these covers further decreased radon escape. Water itself is a poor radon barrier probably due to circulation. Plants had no effect on radon emanation through soil. Although radon diffusion through water-saturated powders appears to be very slow and inefficient, about 25% of the radon escaping from the grains in water-saturated tailings diffuse to the surface and emanate when no cover is present. The radon escaping from tailings through covers of water-saturated compost or soil is no more than could be accounted for by radon produced in the covers themselves.

Jan 1, 1987

By R. A. Sproule

Abitibi Greenstone Belt ? ~2.745 to 2.680 Ga (U-Pb zircon ages) ? Several lithologically-distinct and structurally repeated(?) assemblages ? Represents: ? Allochthonous terranes? ? Single autochthonous terrane? ? Combination of the above Volcanology of Komatiites in the Abitibi greenstone belt ? Tisdale and Kidd-Munro assemblages have channelized flows ? Pacaud and Stoughton-Roquemaure assemblages DO NOT have channelized flows ? Only Tisdale and Kidd-Munro assemblages are mineralized

May 1, 2003

By D. Beneteau

Plotting sets of data collected over time using a frequency-magnitude distribution is common with both earthquake and mining seismology. A Time-Between-Events (TBE) analysis technique simply makes use of the inter-event times and b-values (slopes of the best fit lines on the frequency-magnitude charts) from the same set of data. Four distinct patterns in TBE versus Event Magnitude have been found which suggest whether there are constant seismic sources causing populations of data, or if the smaller and larger events, within the population represent varying seismic sources. Different rates of events, identified as TBE-rates in this study, may suggest whether the events are blast induced, or not. This study was done using actual seismic datasets from hardrock mines in Canada and Australia. This was to verify the applicability of the method to multiple mining environments and to determine the practicality and implications of this methodology to enhance the interpretation of seismic source mechanisms The results of the TBE technique and other proven techniques are combined into a Seismic Mechanism Assessment Worksheet. This is a tool that allows operators to compare trends within seismic datasets with assessments of in-situ rock conditions. The goal is to enhance the understanding of rockmass failure mechanisms.

Nov 1, 2011

By C. Rocha R.

Petioles is a mining group with integrated operations in the smelting and refining of non-ferrous metals, and is also a chemicals producer. Peñoles is the world's foremost producer of refined silver, metallic bismuth and sodium sulphate and is the leading Latin American producer of refined gold, lead and zinc. The Met-Mex Petioles Zinc Plant commenced operations in 1973 with an annual production capacity of 105,000 t/y. Year after year the production has been increased, and at present, the production capacity is 240,000 t/y. In this paper, the leaching process, particularly the operation of the jarosite circuit and its effective removal of impurities such as arsenic, antimony, indium, selenium and tellurium, is reviewed.

Jan 1, 2006

By M. Gimpel, R. Galler, T. Antretter, H. Kargl, R. Tichy, W. Ecker, M. J. Mikl-Resch, G. Pittino

"A computational method based on a continuum-mechanical approach to simulate rock cutting is developed and evaluated. The aim is to obtain the local loading acting at the cutting pick during operation. The explicit FEM is chosen to model the pick-rock interaction. The presented method takes advantage of (i) an advanced material model (ii) a robust contact algorithm and (iii) fast calculations due to parallelization. A damage-plasticity law is chosen and modified with user-subroutines. A user integrated element deletion routine evades critical mesh distortions. Infinite elements at the model boundaries avoid unrealistic deformation wave reflection.INTRODUCTIONExcavation in mining and tunneling is a costly and complex process. Special equipment such as the roadheader (Figure 1) is employed to cut the rock in the excavation process but high material strengths limit their usability (Tockner 1999). Nowadays a challenge is to extend their field of application to harder and more abrasive rock materials. The forces on the pick (Figure 2) are of great importance and determine wear and especially the efficiency of the machine. Figure 2 shows the principle of cutting and the predominant forces. The variation of pick geometry, cutting depth or attack angle will result in an alteration of these forces and determine the efficiency of the process (Tockner 1999). The mechanisms of rock cutting follow the principle of indentation (Kou et al. 1999). Directly under the indenter a hydrostatic stress state evolves causing the material to fail only due to crushing and fragmentation mechanisms. In the close surroundings large strains emerge and tensile cracks are formed but in a further distance the material behaves elastically."

Jan 1, 2015

By M. Gimpel, R. Galler, T. Antretter, H. Kargl, M. Mikl-Resch, R. Tichy, W. Ecker, G. Pittino

"A computational method based on a continuum-mechanical approach to simulate rock cutting is developed and evaluated. The aim is to obtain the local loading acting at the cutting pick during operation. The explicit FEM is chosen to model the pick-rock interaction. The presented method takes advantage of (i) an advanced material model (ii) a robust contact algorithm and (iii) fast calculations due to parallelization. A damage-plasticity law is chosen and modified with user-subroutines. A user integrated element deletion routine evades critical mesh distortions. Infinite elements at the model boundaries avoid unrealistic deformation wave reflection.INTRODUCTIONExcavation in mining and tunneling is a costly and complex process. Special equipment such as the roadheader (fig. 1) is employed to cut the rock in the excavation process but high material strengths limit their usability (Tockner 1999). Nowadays a challenge is to extend their field of application to harder and more abrasive rock materials. The forces on the pick (fig. 2) are of great importance and determine wear and especially the efficiency of the machine. Figure 2 shows the principle of cutting and the predominant forces. The variation of pick geometry, cutting depth or attack angle will result in an alteration of these forces and determine the efficiency of the process (Tockner 1999). The mechanisms of rock cutting follow the principle of indentation (Kou et al. 1999). Directly under the indenter a hydrostatic stress state evolves causing the material to fail only due to crushing and fragmentation mechanisms. In the close surroundings large strains emerge and tensile cracks are formed but in a further distance the material behaves elastically."

Jan 1, 2015

By Robert B. Parsons

"This article addresses the relationship between mine evaluation, the tax system, and economic risk. It is based on a paper presented by the author at recent seminars in Moscow and Tashkent on the subject of mine evaluation.IntroductionTaxation can have a strong influence on the feasibility of a mining project. For the most part, because metal prices are determined on a global basis, the mining concern is not able to pass on to its customers any portion of taxes which the concern has to pay. Taxes are a direct charge against the project. The purpose of the article is to highlight the various ways whereby different taxes can affect the financial viability of a mining operation.The first part of the paper identifies different forms of taxation, and the second part of the paper addresses the different forms of taxation in terms of risk analysis and impacts on the mining project. Finally, the third part of the paper makes brief mention of using the taxation system to provide incentives with respect to investment in mining activities."

Jan 1, 1993

By N. Dobrin, R. Sheinman, Y. V. Kokotov, L. N. Braginsky

Increasing the production of a Mixer-Settler unit requires either increasing flow rates or increasing extractant concentration. The mixers still have to ensure complete emulsification and to maintain high values of specific interface surface area in order to provide a high rate of mass transfer. Theoretically, an increase in mixing intensity can support increased flow rates without reducing extraction efficiency. Unfortunately, conventional pump mixers and mixing systems create small droplets that do not separate easily. As pumping action and mixing intensities are increased, the quantity of small droplets increases. We describe the development and industrial application of a novel mixing system for efficient mass transfer without forming significant quantities of small droplets, targeting both high mass transfer rate and low entrainment values.

Jan 1, 2014