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By Steve Custer, Tim Kahl, Sue Parker

"The primary objective of the Barrick Goldstrike expert system is to achieve the desired liberation size for the autoclave circuit while maximizing throughput. In addition, when downstream limitations (autoclave circuit or others) restrict the milling circuit tonnage the expert system further improves grinding product size. Since its implementation, the expert system has provided expected throughput improvements while improving or maintaining circuit performance.Barrick Goldstrike and MinnovEX Technologies Inc. teamed up to install an expert system to control Line I and I1 of the autoclave grinding circuits. The dissimilar equipments of the two grinding circuits coupled to different production objectives, skepticism among operators, and the variability of the ore types processed in each line challenged the implementation.To ensure implementation success, Barrick Goldstrike dedicated four administrators full time to the project. The system administrators included two metallurgists, a process control engineer and a mill trainer. As usual, the control room operators were the experts who provided the operational logic for the foundation of the control system. The administrators and all eleven of the control room operators signed off on acceptance of the system. Current online utilization is 95%.INTRODUCTIONThe grinding circuit for Barrick Goldstrike’s autoclave process consists of two SAG Mill Ball Mill lines. Line 1 grinding circuit is comprised of a 22 by 8 foot, 2500 horsepower Allis Chalmers (AC) variable speed SAG mill, followed by a 12.5 by 14 foot, 1250 horsepower AC ball mill, and a 13.5 by 18 foot, 1800 horsepower Dominion ball mill in parallel. SAG mill recycle from the primary discharge screen (+5/16 inch) is processed through a 1352 Nordberg Omnicone crusher (4.5 foot). A secondary SAG discharge screen (+1/8 inch) closes the SAG circuit. The ball mill circuit is closed with 6 Krebs super D20 cyclones. Line 2 grinding circuit is comprised of a 24 by 12 foot 4000 horsepower Fuller variable speed SAG mill followed by a 16.5 by 30.5 foot 5000 horsepower Fuller ball mill. SAG mill recycle from the primary discharge screen (+5/16 inch) is processed through a 1560 Nordberg Omnicone crusher (5 foot). A secondary SAG discharge screen (+1/8 inch) closes the SAG circuit. The line 2 ball mill circuit is closed with 12 Krebs super D20 cyclones. The underground Meikle ore is typically fed through Line 1. Achieving the desired product size is critical for successful processing of Meikle ore. Open pit Betze ore is fed to Line 1 when Meikle ore is unavailable. Line 2 processes Betze ore exclusively. Throughput is maximized when processing Betze ore as the product size is less critical. The products of these two circuits are combined as feed to the autoclave circuit. The ore types and the autoclave circuit demands determine the required grinding circuit product size and maximum combined mill feed tonnage."

Jan 1, 2001

By Frank G. Wickert

One key to maintaining successful mining operations in today?s global economy is in having the ability to access real-time machine operating data ([1] G. Brown, B. Ebacher, W. Koellner,2000)([2] Brochure of Siemens E&A, Order Number 141000-1). With recent and ongoing advances in mining equipment systems it is imperative that mine managers have full knowledge of the status of their equipment at any given point in time. This knowledge is critical to ensuring that the productivity of each and every machine is maximized. Knowledge of machine status is only the first step, however, in controlling and optimizing a piece of mining equipment. Computer based diagnostic systems, traditionally offered on mining equipment, have provided a link for collecting data and trouble-shooting problems as they occur. One problem existed, though, that those systems stopped short of providing full drive systems access. A maintenance technician could see the data but to make critical adjustments or make repairs the technician needed to be on the machine. In extreme cases the machine would be down until OEM assistance could reach the mine site. The key then to reducing down-time and maximizing machine productivity was creating a system that could not only monitor drive systems but also provide remote access to those systems. Essentially a link needed to be created through which a technician could gain drive access remotely then make adjustments or repairs without being on the piece of equipment. This paper will introduce AccessDirectTM, a new remote diagnostic system for Bucyrus mining shovels and draglines. AccessDirectTM combines all three important elements of remote diagnostics: ? Vital Signs and Production Monitoring (SiRAS-M) ? Automatic analysis (SiRAS-A) of faults, and tracking of trends for preventive and reliability centered maintenance , and ? Fast, direct Intervention (SiRAS ? I) for troubleshooting support, repairs, and system optimization.

May 1, 2002

By Keith Merriam, Jim McDonnell, Peter Radziszewski, Rob Rotzinger, Ian DeHart

"Taseko Mines Limited Gibraltar copper-molybdenum mine recommenced operation in 2004 with the initiation of a series of development projects to increase throughput capacity as well as modernize the mine.In the second staged development project, a VTM-1250-WB regrind mill was selected to replace the existing conventional ball regrind mill to achieve a target grind size of 80 % passing 45 µm. In the third staged development project, a second VTM-1250 regrind mill was selected for installation in Concentrator #2, to match the existing Concentrator #1 Vertimill. This resulted in approximately 25% spare regrind capacity in the Concentrator #2 design, complete spare parts interchangeability and potential future expansion capacity to 50,000 t/d with no circuit upgrades.In this context, a study was initiated to assess not only the performance of a Vertimill grinding circuit processing a copper concentrate to a particle size of 80% passing 17 µm but also to provide Taseko’s New Prosperity project specific design information for grinding to particle sizes below 80 % passing 25 µm.The objective of the work described in this presentation was to explore Vertimill ultrafine (sub 100 µm) grinding test methodologies at both the lab and pilot scales, compare the scale-up data with operational data from the VTM1250 at Gibraltar Mines and subsequently apply this information to particle sizes down to 80% passing 17 µm. The presentation will describe the results obtained preceded by a description of the Gibraltar regrind circuit historical operation and operational performance as well as a description of the Vertimill technology.INTRODUCTIONTaseko Mines Limited is a mining company headquartered in Vancouver, British Columbia, Canada. In addition to mining development projects for copper, copper-gold, gold, and niobium properties, Taseko Mines is seventy-five percent owner and the operator of the Gibraltar Mine near Williams Lake , British Columbia. Taseko Mines Limited’s Gibraltar copper-molybdenum mine recommenced operation in 2004 with the initiation of a series of development projects to increase throughput capacity as well as modernize the mine.Metso is a leading process performance provider, with customers in the mining, oil and gas, and aggregates industries. It has corporate headquarters in Helsinki Finland, offices in 50 countries and manufacturing facilities on five continents. Amongst other types of equipment and services, Metso designs and manufactures VERTIMILL® (VTM) Grinding Mills."

Jan 1, 2015

By G. Cordingley, A. Mwanza

Lumwana is an open pit Copper mine located in the Northwestern Province of Zambia approximately 80 km west from the provincial capital of Solwezi, approximately 300 km northwest from the Copperbelt and 700 km northwest from the national capital of Lusaka. The mine has two major Copper deposits: Malundwe and Chimiwungo. Copper mineralization includes Chalcopyrite, Bornite and Chalcocite. In addition to Copper, these deposits also contain the undesirable element Uranium contained in vein hosted and disseminated Uranite. The processing plant was designed using conventional technologies: semi-autogenous grinding (SAG) and ball mill for grinding, and mechanical cells for rougher and cleaner flotation. Soon after commissioning in early 2009, it was recognised that two stages of conventional cleaning were unable to produce plant final Copper concentrates with the desired Uranium grades. Studies have shown that a significant quantity of liberated and fine Uranium particles (up to 80-90%) is recovered with the concentrate by entrainment. Lumwana Operations sought the use of the Jameson Cell technology after observing successful implementation at other sites in rectifying similar issues. In late 2009, Jameson Cell pilot-plant test work was conducted at the site and this quickly led to the installation of a full-scale B5400/18 model into the existing cleaner circuit. Inclusion of the Jameson Cell resulted in the plant being able to effectively produce clean and saleable concentrate with Uranium contents consistently below acceptable levels. Initially designed to be used as a cleaner scalper cell at the head of the existing conventional cell circuit, subsequent operational issues with the existing recleaner cells forced reconfiguration of the cleaner circuit and reintroduced the Jameson Cell for the recleaning duty. This paper reports the Lumwana Operation from the first two years of operation where it struggled to produce a saleable concentrate with Uranium grades below 150 ppm, which is the maximum allowable limit set out in the smelting contracts, to steps taken in the subsequent years to implement a satisfactory solution. The plant can now consistently produce a clean Copper concentrate with Uranium grades well below 130 ppm and the overall improvements implemented at site have seen the overall plant recovery improve by 1.3%.

Jan 1, 2014

By Bruce Conard

For many years, Bruce Conard has been engaged in reading about and discussing the desired sustainability of the mining and metals resource industry. He has, however, become concerned that there is a greater issue that requires our urgent attention: what challenges do we face as a global society? His Distinguished Lecturer presentation traces the idea of environmentally sustainable economic development but concludes that a business’ interest in its sustainability is predicated on the sustainability of our global society. Conard reviews some of the most serious challenges, including population growth, clean energy supplies, freshwater availability and climate change, and calls on scientists and engineers not only to apply their skills in helping solve these challenges, but most urgently, to speak with intelligence and passion about the need to act now.

Jan 1, 2014

By B. H. Kim

It is hypothesized that the standard approach adopted to characterize the ground and to determine the rock strength properties at depth are flawed and generally tend to underestimate the rock strength and possibly the stiffness, particularly when the rock mass is characterized as massive to moderately jointed or blocky to very blocky. It is therefore necessary to conclusively established that the hypothesis, that the rock strength in highly confined rocks is greater than generally anticipated, is actually valid and generally applicable, and then to develop new procedures to establish rock parameters that can be reliably used for the design of deep excavation.

May 1, 2009

By Pierre Beaudoin

"This paper deals with the repairs made on two damaged mills. It investigates briefly the causes of the damage, explain its nature and the design of the repair. It explains the detrimental effect on operation and the solutions implemented to reduce them. Finally, to review the follow-up required for such repairs. LOCATIONThe Holt McDermott Mine is located 75 kilometers Northeast of Kirkland Lake and 30 kilometres west of the Quebec border in Northeastern Ontario. The town of Kirkland Lake is located approximately 500 kilometres north of Toronto. HISTORYThe discovery of gold in Holloway Township dates back to early 1920. In 1984 Barrick Resources, which amalgamated with Camflo Mines, acquired more claims on the property and initiated an extensive drilling program. By 1985, the drills indicated reserve increased to 2,500,000 tonnes grading 6.8 g/mt. In 1986 a production decision was made and in 1988 the mine was officially opened.As of December 31, 1998, 4,691,507 tonnes grading 5,66 g/tonnes have been milled from 4 ore-bodies. The mill started up in June 1988."

Jan 1, 2001

"The measurement of error in assays collected as part of a mineral exploration program or mining operation historically has been undertaken in a variety of ways. Different parameters have been used to describe the magnitude of relative error, and each of these parameters is related to the standard measure of relative error, the coefficient of variation. Calculation of the coefficient of variation can be undertaken in a variety of ways; however, only one produces unbiased estimates of measurement error: the root mean square coefficient of variation calculated from the individual coefficients of variation.Thompson and Howarth’s error analysis approach has also been used to describe measurement error. However, because this approach utilizes a regression line to describe error, it provides a substantially different measure of error than the root mean square coefficient of variation. Furthermore, because regression is used, Thompson and Howarth’s results should only be used for estimating error in individual samples, and not for describing the average error in a data set. As a result, Thompson and Howarth’s results should not be used to determine the magnitudes of component errors introduced during geochemical sampling, preparation, and analysis.Finally, the standard error on the coefficient of variation is derived, and it is shown that very poor estimates of relative error are obtained from duplicate data. As a result, geoscientists seeking to determine the average relative error in a data set should use a very large number of duplicate samples to make this estimate, particularly if the average relative error is large."

Jan 1, 2007

By Benoit Bissonnette, David Gelderland

"The Campbell Mine Constructed Wetlands has been in full operation, processing effluent from the water treatment plant of the mill circuit for the last two years.The overall results are extremely positive with dramatic improvements for the originally targeted parameters – Ammonia, Copper and toxicity.• Ammonia concentrations were reduced from an average of 5 mg/L to an average of 0.43 mg/L which translates to an average reduction of 91%.• Copper concentrations were reduced from an average concentration of 0.054 mg/L to an average of 0.019 mg/L, which translates to an average reduction of 65%.• LC50 Acute toxicity testing revealed no impact.• IC25 Chronic toxicity tests revealed no impairment to growth or reproduction.As a result of the improvements in discharge water quality from the wetland, 100 percent compliance with respect to all Certificate of Approval, MISA and MMER regulations for effluent will be consistently achieved.The system has proven to be very easy to operate and maintain, with a minimum of care. Given some basic rules are followed, the construction of the wetlands was straightforward and relatively inexpensive compared to other treatment methods.The ecological benefits of the operation of the wetland are also quite substantial, as is the positive image of the corporation in environmental stewardship.INTRODUCTIONOver the last four years, Campbell Mine has adopted an aggressive schedule for the development of wetlands for use as the final stage of effluent treatment within the tailings management facility. The focus of this work has been to utilize natural biological systems to provide Campbell Mine with a 100 percent compliant water quality with respect to all MISA, MMER and COA discharge criteria at all times throughout the effluent discharge period."

Jan 1, 2003

By E. Sharifi

Advanced Process Control (APC) has been one of the most beneficial tools in the past decades available to minerals processing industry. Low capital cost together with significant improvements in process optimization have made APC an attractive investment option for nearly all mineral processing units. During economic downturns, importance of process optimization becomes even more relevant as metal producers tend to target de-bottlenecking and process efficiency improvements rather than large-scale capacity upgrades. APC project clearly has a lot of potential to improve process performance but there are also some pitfalls to be identified and avoided in order to achieve a desired outcome. Above all, APC project implementation is collaboration between the system vendor and user. Targets for the optimization must be agreed together with the customer and process performance must be defined before and after the optimization project. Most importantly, performance of the process must be monitored on a continuous basis during and after the project and potentially improved further. This paper discusses Outotec’s experiences from various concentrator optimization projects. Some examples are discussed in more details; however, the main target is to present general guidelines enabling a successful APC project implementation.

Jan 1, 2014

By E. Gallestey, D. Groenveld, F. Kolb, M. Rozou

"Recent copper price evolution pushes modern mining industry even harder to achieve highest production with maximum efficiency. Operations are bound by numerous contractual and environmental conditions that bring a high degree of complexity to both the operators controlling the process and the plant managers assessing the circuit’s potential and setting the production goals.Advanced process control (APC) for grinding is one important tool to operate this most energy intense area in an optimal way, finding the optimal trade-offs between highest throughput, energy efficiency and product quality based on variable ore properties, production targets and management priorities.ABB’s state of the art control and optimization software platform enables user to design a controller based on model predictive control (MPC). The paper and the presentation show the technology used and the results achieved through an APC controller installed in a pilot project in Aitik (Boliden SA), Sweden. Furthermore, possibilities to interconnect grinding with other areas as stockpile management and flotation with various interconnected APC controllers will be shown. Finally, an example of the return on investment and the payback times based on the increased throughput and better product quality will be presented.INTRODUCTIONDepending on the ore characteristics and the targeted plant capacity, the design of the grinding circuit may vary significantly. Typically, the circuit consists of several mills (rod, ball, SAG, AG) in series and/or parallel with a number of classifiers and sumps at appropriate locations (see Figure 1).The main goal of the grinding section is to reduce the ore particle size to a level that enables efficient separation between gangue and precious metals in the subsiding processing step. The trade-off between quality and quantity has to be made. At the same time, it is also crucial to execute this process at the lowest possible energy and grinding media consumption."

Jan 1, 2015

The rock mass classification systems were developed for different functions, including support selection, excavation method selection and the determination of rock mass engineering properties for excavation design, among others. This explains in part why we have several rock mass classification systems. It is often cautioned that the rock mass classifications are to be used for preliminary excavation support design, but this caution is now often overlooked and detail/final support design based on the rock mass classification systems. This paper advocates differentiating between rock mass classification for pre-excavation support planning and rock mass classification for at-face excavation performance assessment. It is concluded that most at-face excavation performance problems are attributable to confusing the virgin rock mass rating with the rock mass rating on exposure during excavation, and that this observation is independent of the method of excavation. Procedures are then presented for virgin rock mass rating and for at-face rock mass rating/assessment during excavation.

May 1, 2009

By Michel Ruel

"This paper describes how to make advanced control choices when difficult processes need improvement. The decision-making process involves choosing between a rules-based approach and a model-based approach as well as weighing benefits and drawbacks, complexity and simplicity, investment and results. This paper will present briefly each solution: basic control, advanced regulatory control, model predictive control, and expert systems such as fuzzy logic controllers and neural networks. The article then proposes a decision tree for selecting the most appropriate approach. A table will compare usage, development, commissioning, maintenance and lifecycle costs for each approach. Finally, conclusions and suggestions will summarize the methodology.INTRODUCTION Advanced process control (APC) is a popular topic. How can one decide whether advanced control should be added to an existing system? Advanced control is used to improve performance, stabilize production, handle constraints, protect equipment and manage grade changes. Most plants use feedback controllers, usually PID (proportional, integral, derivative) controllers. It is common to develop special control schemes to handle more complex processes. In classic PID process control, a controller brings a single value close to a set point using a single manipulated variable. On the other hand, APC brings several values close to optimal targets simultaneously using several manipulated variables. APC's four main strategies are advanced regulatory control, model predictive control (MPC), fuzzy logic and neural networks. Simple solutions are always preferred. Complexity will be increased if performances (production, quality, etc.) are below par. Profitability analyses should be conducted to validate project viability. Needs—not trends—should dictate choices! Before increasing complexity, it is important to define needs, goals, technical support, budget, etc. All these approaches entail strengths and weaknesses. Building a project based on technology rather than needs spells trouble."

Jan 1, 2014

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 Joseph N. Bakambu

It is currently recognized by mining society that autonomously guided underground mining vehicles may greatly increase the efficiency of mining production and improve human safety. Recent results in mobile robotics, data fusion and sensor development provide a solid basis for solving the problems related to autonomous underground navigation. Recently developed commercial systems mostly rely on the infrastructure that is expensive and difficult to maintain. Guideless navigation in unstructured and harsh environment of underground mines is still a challenging task. In this paper, we describe an autonomous navigation system for an underground mining vehicle equipped with on-board dead reckoning, inertial and optical sensors. This system does not require any artificial infrastructure and is capable to guide the vehicle along the complex environment of interconnected underground drifts; it also ensures the detection of obstacles on the vehicle path. The user interface for monitoring and control is described and the results of laboratory tests and on-site experiments are presented. Work in progress addresses the system integration for real equipment, and the system upgrade, adding map-building and selflocalization capabilities .

May 1, 2002

By S. K. Schwartz

"This paper describes the general layout of the environmental monitoring scheme at Devco 's No. 26 Colliery, including wall face ventilation, fan performance and methane drainage, and then goes on to discuss the sensors, the outstation layout, the surf ace control room and the protection of the system.IntroductionCape Breton coal mines have been pioneers in the use of the latest technology in mining coal on this continent. To mention just one example, continuous methane monitoring at the coal face was started in 1976 and the idea of automatically stopping the face conveyor during high gas levels using the face signalling system was conceived and developed by CBDC engineers.With the introduction of remote environmental monitoring, No. 26 Colliery will be the first underground coal mine in Canada and possibly in North America to have computer-based comprehensive environmental monitoring.Traditionally, surveillance of the mine environment has been based mainly on periodic checks by portable or hand-held monitors. Although this method proved adequate, it has some limitations, namely:1) restricted 'number of observations and samples;2) relatively long time between taking measurements and availability of results for assessment.With remote monitoring, the above limitations are overcome because (a) monitoring is continuous and (b) monitored data are updated quickly (typically 5-7 sec.). Remote monitoring also provides a centralized 'information center' at the surface from where the entire mine environment can be monitored. Details of modes in which data can be displayed and features available at the location will be discussed later in the paper."

Jan 1, 1982

On the 26th of June 2000 a hydraulic fill retaining barricade failed at the Bronzewing mine in Western Australia. The barricade failure resulted in the release of 19,000 m3 of saturated hydraulic fill into the mine and caused the deaths of three miners. Following this tragic accident, the practices and procedures of mines using hydraulic fills came under intense scrutiny by regulatory bodies and mining companies. At this time, the use of hydraulic fill at Normandy?s zinc/copper Scuddles mine was suspended and waste rock became the sole backfill material in use underground. By 2003, development of the adjacent Gossan Hill mine had progressed to a point where a self supporting fill material was required to enable full recovery of high grade ore. Cemented hydraulic fill (CHF) was identified as the optimal fill type and work began on designing appropriate management procedures and controls to ensure the safe implementation. This work included definition of the fill properties, plant design and construction, reticulation system design, design of stope barricades and drainage systems and fill placement control and monitoring practices. CHF placement began on 16th July 2004 and has continued to date. Significant operational experience has since been gained in areas including plant performance, fill product quality assurance, barricade construction, stope drainage and in-situ performance.

May 1, 2007

By D. Rahal, I. Shah, B. Hines, S. Reddick

"The development of stirred milling technology has proven to be an enabling technology in fine grained metallic deposits. The increased grinding efficiency allows for the economic size reduction required to produce saleable concentrates. This improvement has opened the door to retreatment projects such as reprocessing of historic gold mine tailings. Recently a VXP2500 stirred mill was installed at Casmyn Mining Zimbabwe Turk mine to allow the reprocessing of historic mine tailings. After commissioning, an extensive joint research project between Casmyn and FLSmidth Minerals was conducted to optimize the performance of the mill. This paper outlines the challenges encountered in the optimization program and the outcomes from the joint research project.INTRODUCTION The development of stirred mills has opened up many new opportunities to recover valuable minerals from refractory ores. Stirred mills have already been reported as an enabling technology for the processing of fine grained ores in lead/zinc applications (Pease, Young and Curry, 2005). Historically, conventional ball mills were unable to economically grind material fine enough to produce the required recovery or concentrate grade. This often resulted in the loss of valuable materials to the final plant tailings. The advent of stirred milling has now provided an opportunity which has both economic and environmental benefits, the reprocessing of historic mine tailings. Many tailings stockpiles now contain economic concentrations of gold because of the ability of stirred mills to efficiently and economically grind the tailings to liberation sizes. The primary advantage of reprocessing historic tailings is very low cost processing. Recovering the tailings is usually as simple as pumping the material into the reprocessing circuit. The disadvantage of reprocessing tailings is the low feed grade and greater difficulty in recovery valuable minerals at the same size distribution. The material has already been previously processed so fresh surface area or an increase in metal exposure is required. These are both provided by regrinding the tailings material."

Jan 1, 2014

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 Jerry Ran

Stope back caving in a mine using open stope mining interrupts the planned mining sequence and causes oversize muck and dilution with adverse economic implications. As many underground mines are mining or have plans to mine at depth, stope back caving could have significant impact on the mine sustainability. Therefore understanding the caving mechanism is important in preventing future occurrence and improving the mine economic performance. Falconbridge Ltd Kidd Mine is an underground mine using open stope method producing more than 2 million tonnes per year. Its current lowest mining level is approximately 2070m below surface and the lower portion of the orebody is being developed. In years of 2002 and 2003 the back of three stopes of approximately 1900m and 2040m below surface caved and caused substantial mining difficulties at the mine. As these caved stopes are subject to stress concentration, seismic activities and near major geological structures, the caving mechanism is much more complex than that of stopes near surface. In addition to the recorded caving history by site observations, the mine carried out cavity surveys and test drilling to define the caved profiles. The mine seismic monitoring database provided information at these stopes. Stress modeling work conducted by an external consultant provided the stress patterns at the caved stopes. Based on the field collected data and stress and seismic information, this paper presents details of the stope caving process and cavity surveyed profiles, reviews the predictability of the stability graph approach for these cases, discusses the caving mechanism and proposes preventive measures to stabilize the stope back.

May 1, 2004