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By Elhachmi Es-Sadiqi

"For over 40 years, CANMET has focused its research on value-added products and energy efficiency in the metals industry. The Efficient Metal Production Program is currently managed by Dr. Elhachmi Es-Sadiqi, and the Canadian steel industry is its main client — both directly and through international organizations such as the American Iron and Steel Institute (AISI) and the International Lead and Zinc Research Organization. AISI membership includes Canadian steel companies IPSCO, Dofasco, Stelco, Algoma Steel and Sidbec Dosco.Canada’s steel industry makes important contributions to the economy. The industry comprises 14 companies and employs 33 600 people in locations such as Sydney, Nova Scotia; Tracy, Quebec; Selkirk, Manitoba; Saskatoon, Saskatchewan; and Sault Ste. Marie, Ontario. With annual production at about 16 million tonnes, sales in 1995 totalled $11 billion, $3.8 billion of which was exported.Canada’s steel industry supplies the transportation, oil and gas, appliance, packaging and construction industries. It is at the forefront of new technology use and has a substantial support network to provide raw materials, equipment and service. Three main segments of the industry include flat-rolled products (e.g., plate and sheet steels), long products (e.g., concrete reinforcing bar and structural steel), and specialty and alloy steels (e.g., stainless steel and tool steels, in both long and flat products)."

Jan 1, 1998

By Brian Flintoff

"When I was first asked to prepare this paper and presentation in late June, I thought it might be fun to ""step back and paint the bigger picture."" Having attempted to do this, fun is not the first descriptor that now comes to mind, and speaking dyslexically, I've had 'nuf.'Unlike Nostradamus, or even Orwell, I've discovered that I'm ""clairvoyantly challenged"" and not even the psychic hot-line was of much help, at least with respect to process control! I am somewhat comfortable speculating on evolutionary change, but the radical developments that will arise from revolutionary changes are well beyond my mortal capabilities. Even with evolutionary change, I'm reminded of the lessons of time series analysis which show the prediction error to grow exponentially as the horizon moves into the future. As Macluhan is reported to have said: ""Predicting the future based on the past is a little like driving your car while looking in the rearview mirror!""Having honestly presented my qualifications, allow me to try to look at process control and to offer some conjecture on where we're probably headed. In the end, it is said that: ""The plant of the future will have only two employees, a man and a dog. The dog will be there to keep the man from touching the equipment.1""IntroductionA little less than a decade ago Andy Mular and I co-edited a monograph entitled ""A Practical Guide to Process Control in the Minerals Industry."" The work was commissioned by the senior management of a consortium of Canadian mining companies, since it was widely perceived that control was an area of great economic potential, but one that had not been effectively tapped. The concern was that if the industry could not soon deliver on the ""potential"", the term may well have appeared in the epitaph of what was, to these men, a very attractive investment opportunity. I think it is fair to say that over the past few years process control has clearly established itself as an essential technology in plant operation and optimization. That isn't to say that we get it all-right, all-the-time, but, the circumstances are much different than they were. In the eyes of many, process control has attained the distinction of being considered a mature technology, even though there are still countless avenues for exploration."

Jan 1, 1998

By M. Al-Hilal, G. Rajja, A. Al-Ali, Y. Jubeli

Abstract -A radiometric survey was carried out over clastic sediments in the immediate vicinity of some phosphatic sediments of Cretaceous age in the Wadi Qasser Al-Hallabat basin of central Syria. The objective was to explore for uranium and to define its dispersion pattern. This was based on ground radiometric surveys and geological studies. All ground surveys (using radon emanometry, track etching, gamma-ray survey and geochemistry) gave similar results, outlining the locations of the radioactive phosphatic formations in the basin, and indicating the dispersion pattern of uranium in the clastic sediments in the surrounding area. The dispersal of uranium from upper Cretaceous phosphatic formation occurs by mechanical weathering and chemical leaching by oxidizing surface waters. A rough estimate is that about one-third of the original uranium content of the Cretaceous sediments has been dispersed. Mechanical erosion is responsible for the main part of this released uranium, which now occurs in Recent sediments. However, the occurrences of spotty secondary U mineralization indicates that another small part of the available uranium must have been chemically leached out by the prevailing oxidizing waters, forming minor surficial minerals.

Jan 1, 1998

By J. K. Gowans

The Research and Design group of the Project Development Division (PDD) of Placer Dome Inc. includes metallurgical, electrical, civil and mechanical engineers. They provide metallurgical research and conceptual flowsheet development, feasibility concepts for the processing and ancillary facilities, and manage the detailed design of the facilities once approval has been given to a mining project. This paper describes how this group works, within the Project Development Division, to help develop feasibility studies with the Evaluations Group, manage detailed design, and provide support for the Construction Group. The paper briefly reviews the history and growth of the group and describes how it is evolving. The role of outside engineering firms and how they are incorporated into the division’s objectives are also discussed. The paper highlights the differences between Placer Dome’s Project Development Division and other mining groups, and why this approach fits the way Placer Dome does business.

Jan 1, 1998

By T. A. Postolski, A. J. Sinclair

"Abstract- Two examples are used to describe how geological features impact on the development of semi-variogram models to be used for geostatistical resource/reserve estimation of porphyry-type deposits. In the Main zone of the Huckleberry porphyry copper deposit, mineralization is concentrated in fracture zones localized in volcanic rocks, along the eastern and southern margins of a granitic stock. Mineralized volcanic rocks can be subdivided into three separate domains, each with its own preferred direction of mineralization that is reflected in contoured Cu diagrams and semivariograms.The East zone at Huckleberry deposit, spatially distinct from the Main zone, is controlled by a fracture zone elongate roughly east-westerly and bounded on the south by a major fault (easterly striking and steeply dipping) across which there is a dramatic drop in grades. The eastern part of the East zone appears to be coaxial with a large intrusive body; the western part contains a small, elongate dike-like intrusion. Contoured Cu values for many levels suggest that the principal direction of geological elongation of the east and west domains of the East zone differs significantly. Independently derived semi-variogram models for each domain are different and reflect this difference in trend.In both Main and East zones of the Huckleberry deposit, block estimates by ordinary kriging are significantly different using a domain-specific semi-variogram model than using a deposit-general semi-variogram model. The domain-specific estimates are deemed better because they are based on local controls of mineralization and have less conditional bias than those generated by the depositgeneral semi-variogram model."

Jan 1, 1998

By C. Blais, G. L’Espérance

Characterization of second phase particles is important with regard to their influence on mechanical properties of materials. Analytical electron microscopy offers the possibility to achieve complete characterization of inclusions. Complete characterization of inclusions means quantitative evaluation of their chemistry and the stereological parameters. A characterization technique based on integrated microscopy and involving scanning electron microscopy, image analysis and energy dispersive X-ray spectrometry is presented. A discussion of the use of transmission electron microscopy and electron energy loss spectroscopy is also presented for the characterization of very small particles and compounds (>100 nm).

Jan 1, 1998

By André Chagnon, Michel Malo, Benoît Dubé, Chantal Pelchat

"Abstract- In the southern Gaspé Appalachians, gold mineralization is spatially associated with the Acadian dextral strike-slip Grand Pabos-Restigouche fault system. Two different structurally-controlled gold prospects, the Lac Arsenault and the Saint-André-de-Ristigouche, are described to unravel the genesis of gold mineralization in this part of the Canadian Appalachians.At the Lac Arsenault gold prospect, gold mineralization consists of Au-As-Pb-Zn-Cu-(Ag) polymetallic fault-filled quartz veins with laminated textures emplaced in brittle-ductile sinistral X shear fractures. Mineralized veins are hosted by Middle Ordovician graywacke of the Arsenault Formation, belonging to the Dunnage Zone, the Early Paleozoic oceanic domain of the Appalachians. Terrigeneous rocks of the Arsenault are regionally metamorphosed at the lower greenshist facies and the mineralized veins are included in a zone of Fe-carbonate alteration.The Sb-Au-As mineralization of the Saint-André-de-Ristigouche gold prospect, in the southwestern Gaspé area, comprises extension veins in the extension direction emplaced in brittle conditions. Mineralized veins are hosted by calcilutite and laminated silty and argillaceous limestone of the Early Silurian part of the White Head Formation, which belongs to the Gaspé Belt, the Middle Paleozoic successor basin in the Gaspé Appalachians. Metamorphic grade of the White Head Formation in the southwestern Gaspé area is very low, but the gold mineralization is included in a zone of hydrothermal propylitic alteration which includes two Cu-skarn mineral occurrences. The Lac Arsenault gold prospect has many characteristics of "greenstone-hosted quartz-carbonate vein" deposits whereas the southwestern Gaspé area, which includes the Saint-André-de- Ristigouche gold prospect, shows affinities with the geological setting of sediment-hosted gold deposits (Carlin-like deposits). The two gold prospects are controlled by the Grand Pabos- Restigouche fault system but they were not emplaced at the same level in the crust. Acadian strikeslip fauting played a major role in their respective genesis in providing channelways for ore-bearing fluids. The recognition of the analogy of the geological setting of the southwestern Gaspé area with that of Carlin-like mineralization gives new ideas for exploration in the area and elsewhere in the Appalachians.Résumé - Dans le sud des Appalaches de la Gaspésie, on trouve des minéralisations aurifères spatialement associées au système de failles de coulissage dextre acadien de Grand Pabos-Restigouche. Deux indices très différents, Lac Arsenault et Saint-André-de-Ristigouche, sont décrits pour évaluer la genèse des minéralisations aurifères à contrôle structural de cette partie des Appalaches canadiennes. Au Lac Arsenault, la minéralisation aurifère comprend des veines polymétalliques à Au-As-Pb- Zn-Cu-(Ag) en remplissage de failles. Ces veines à texture laminaire se retrouvent dans des zones de cisaillement fragiles-ductiles senestres de type X. Les veines minéralisées sont encaissées dans les grauwackes d’âge Ordovicien moyen de la Formation d’Arsenault appartenant à la zone de Dunnage, le domaine océanique du Paléozoïque précoce des Appalaches canadiennes. Les roches terrigènes de l’Arsenault sont métamorphisées régionalement au faciès inférieur des schistes verts et les veines aurifères sont dans de larges zones d’altération dolomitique (Fe-carbonate).Dans le sud-ouest de la Gaspésie, la minéralisation à Sb-Au-As de Saint-André-de-Ristigouche est dans des veines d’extension comprises dans la direction d’extension et mises en place dans des conditions de déformation fragile. Les veines minéralisées sont encaissées dans les calcaires argileux et les calcilutites de la partie silurienne de la Formation de White Head qui appartient à la ceinture de Gaspé, le bassin successeur du Paléozoïque moyen des Appalaches de la Gaspésie. Le degré métamorphique des roches du White Head est très bas, mais"

Jan 1, 1998

By M. G. Rylatt, G. M. Popplewell

"Production from Canada's first diamond mine is planned for the last quarter of 1998. The climatic conditions and the variation in kimberlite types to be treated have lead to the development of a compact and flexible processing plant.High kimberlite moisture contents and winter temperatures below -40°C have dictated a process flowsheet with limited in-circuit storage to reduce materials handling difficulties. The latest developments in High Pressure Grinding Roll technology will be used to liberate the valuable diamond, reduce diamond breakage, and increase fines production to reduce the amount of material for down stream processing in the Heavy Medium Separation section.A varying heavy mineral concentrate yield has lead to the development of a final Recovery section that will incorporate Attrition Milling and Wet High Intensity Magnetic Separation for concentrate reduction. The latest developments in diamond X-ray sorting will be used to produce a final diamond concentrate for mechanical sizing, weighing and packing.Fine tailings thickening will utilise Deep Bed Compression type thickeners. This relatively new technology can produce;i) high underflow densities at low flocculant dosage rates, andii) clear overflowswith a smaller thickening area than conventional high-rate thickeners."

Jan 1, 1998

By M. A. Power

The diamondiferous Drybones Bay kimberlite pipe is the largest pipe (900 m by 400 m) discovered to date in the Northwest Territories. The pipe intrudes granodiorite of the Archean age Defeat Pluton and contains crater, reworked crater (epiclastic) and diatreme facies kimberlite. In-situ measurements of seismic p-wave velocity were recorded with in-line refraction arrays over representative areas. Refractions from fresh kimberlite were recorded over epiclastic facies kimberlite in the eastern portion of the pipe and returned an average velocity of 4300 m/s. Refractions from weathered kimberlite were recorded on all lines and returned velocities ranging from 1900 m/s to 2200 m/s. Granite surrounding the pipe returned an average velocity of 5400 m/s. The results indicate that there is a definite contrast in seismic velocities between kimberlite and country rocks at Drybones Bay and suggest that seismic refraction surveys may be an effective means of screening kimberlite targets in glaciated areas underlain by igneous or metamorphic rocks.

Jan 1, 1998

By E. De Souza

The instrumentation and monitoring of rock behaviour have played an important and necessary role in the practice of potash, rocksalt, gypsum, trona and coal mining. The art of rock instrumentation applied to soft rock and coal mining has progressively evolved over the past years and will surely continue to advance at a faster pace in the future as a result of the technological revolution we experience today. The development of sophisticated mine-wide data communications systems is being used for instrumentation and sensor automation, and laser, sonar and geophysics technology are being continuously adapted for rock monitoring purposes. In this paper, the author provides an overview of typical rock instrumentation used today and offers some views of the progressive evolution in rock mechanics instrumentation sophistication and design.

Jan 1, 1998

By A. Vien, B. C. Flintoff, R. P. Edwards

"A major thrust in industrial automation over the past few years has been the exploration and incorporation of higher level (supervisory and optimizing) control strategies aimed at more fully exploiting the existing control system infrastructure. There is little doubt that this is worthwhile pursuit, however, one must not lose sight of the maintenance and development requirements of the basic control system. Statistics on loop performance indicate that this too is an area of considerable potential. In this paper the authors look at some of the less elegant, but arguably equally important issues in mineral processing plant control. The focus is on controller structures, loop tuning, sampling, filtering, and some of the other principal components of the regulatory control foundations. In many cases significant improvements in control performance can be achieved by getting back to the basics.IntroductionEvery modem concentrator has a state-of-the-art computer control system in place. Several of these are contemplating installing, or have installed, advanced control systems, such as expert systems, but the foundation of their control system remains the PI controller. Although the authors are not aware of any survey or published information for the mineral processing industry, it is reasonable to assume that it would be similar to the pulp and paper industry. ""The average [pulp] mill has some 2000 control loops of which 97% use PI control. This means that PID, dead time compensation, adaptive controllers, specialized algorithms, ... , constitute only 3% of the installed base."" (Bialkowski [1992]).Bialkowski [1992] also stated that ""If you have been keeping score, only 20% of the loops surveyed actually decrease variability in automatic over manual mode of operation, in the short term."" He attributed the problems to: poor tuning (30% of all loops), control valve problems (30% of all loops) and process problems (20% of all loops). There appear to be a serious need to go back to basics and review the existing control system."

Jan 1, 1998

By I. Farr, P. Quinn, H. Mani

"Difficulties in the flotation of Inca's ultramafic ores at the Thompson Mill are related to the presence of serpentine slimes and some floatable rock minerals. Serpentine slime coatings depress pentlandite recovery while rock flotation decreases concentrate grade. Carboxy methyl cellulose (CMG) has been shown to promote sulphide flotation and to reject floatable rock.To improve ultramafic ore flotation, CMC addition in the rougher stage was studied in a laboratory scale column. Batch tests were conducted in the lab and followed up with continuous testwork at the Thompson mill. At 0.5-1.0 g CMG per kg ore, pentlandite recovery is increased by 5-10% in rougher flotation, pentlandite/rock selectivity is improved and pentlandite/pyrrhotite selectivity is unaffected.IntroductionAt Inca's Manitoba Division, two distinctly different sulphide ores are processed at the Thompson Mill, primarily by froth flotation. The sulfide ores are contained within the Thompson Nickel Belt and currently there are two operating mines, Thompson and Birchtree. Sulphide mineralization in both mines is simple, consisting of pyrrhotite (both monoclinic and hexagonal), pentlandite, and minor chalcopyrite. Both deposits are hosted by metasedimentary and metavolcanic rocks with variable ultramafic rock associations. Ultramafic rocks are mostly serpentinites: magnesium rich rocks composed predominately of serpentine. There is little serpentinite at the Thompson mine, while mineralization at Birchtree is closely associated with significant ultramafic rocks.Excellent recoveries of pentlandite (Pn) and chalcopyrite (Cp) are achieved at the Thompson Mill when processing ore from the Thompson mine. In treating the ultramafic associated Birchtree ore, nickel recoveries are some 6 to 8% below that achieved with Thompson ore. Furthermore, a typical concentrate from Birchtree ore contains more rock and is higher in MgO content. The presence of rock in the concentrate is related to free floatable rock species as well as rock locked with sulfides. The reason for the difference in flotation responses of these two ores has been the subject of on-going re-search."

Jan 1, 1998

A newly developed damage model was used in the study of rock fragmentation mechanisms involved in crater blasting. Simulations show that at the detonation of the explosive charge, a crushed zone around the explosive charge is formed due to compressive failure and then a strong pressure wave is sent out forming a pressurized ring that propagates at the dilatation wave velocity. As the pressurized ring leaves the crushed zone, two tensile stress components perpendicular to the radial stress are developed in response to the action of the radial pressure, causing tensile failure and forming a damage zone around the charge. The formation of this damage zone is quite independent of the depth of the explosive charge provided there is no interference by the reflection from the free face. When the pressurized ring reaches the free face, it is reflected there and causes rock failure on the ground surface that forms another damage zone. Under the simulation conditions, it is revealed that the depth of charge is a factor controlling the relationship between the two damage zones. At a depth smaller than the optimum, the two damage zones coalesce into one and there is excessive rock breakage; otherwise, the two damage zones tend to isolate from each other with the increase in the depth of charge. Calculations of fragmentation indicate that the average fragment size increases and the uniformity of fragments decreases when the depth of charge increases as observed in practical blasting.

Jan 1, 1998

By Laxman M. Amaratunga, Nuri Hrnidi

"Reactive pyrrhotite tailings were agglomerated using the Cold Bond Tailings Agglomeration (CBTA) process with low cost binders; Portland Cement and fly ash. Various chemical additives, were used to retard acid mine drainage (AMD), including acid neutralizers, surfactants, sealants, and bactericides, which were encapsulated into the agglomerates. The choice of these additives was based on their low cost, low toxicity, and environmental friendliness. The main objective of the study was to examine the long term stability of these reactive tailings agglomerates towards AMD when used as aggregates for disposal in underground paste backfill.A carefully controlled kinetic stability test was carried out using specially designed humidity cells suitable for testing pellets. Using the humidity cell test method a 20-30 year AMD test may be accelerated to 50 weeks. During this period the following parameters were monitored: pH, redox potential, conductivity, sulphate, acidity, and dissolved metals.Results indicated that most of the encapsulated additives were successful in retarding AMD, while the control samples produced significant amounts of acid generation. The water soluble surfactant Enviroseal, and the sodium silicate sealant were very effective as a long term retardant for acid generation reactions in the sulphidic tailings when exposed to oxygen, water and iron-oxidizing bacteria.IntroductionThe sulphidic material discharged from concentrators becomes reactive upon exposure to air and/or water. Pyrrhotite (Fe0 S0_1) and pyrite tailings in particular which are discharged from the beneficiation process in the mining and mineral processing activities consist of finely ground particles. Upon exposure to oxygen and moisture, the tailings become reactive due to the instability of the metal sulphide minerals present which undergo spontaneous oxidation, thereby producing a weak sulphuric acid. Therefore, the long-term behaviour of the tailings can have a significant impact on the environment, due to acid mine drainage (AMD). AMD is created during natural atmospheric weathering when leaching action (natural and bacterial) conditions are present in the process wastes discarded during the mining and milling of sulphur bearing ores, and consequently it plays a major role in surface water chemistry."

Jan 1, 1998

By James A. Finch

"I offer a personal view of what the next 30 years holds for mineral processing. Re-stating that mineral processing will remain a vibrant industry in raw material production, growth opportunities in waste management are identified. The processing sequence familiar now (mining -mineral processing -extraction) will become more interwoven. In situ processing (i.e., milling underground) will evolve from concept to demonstration. Opportunities to exploit physical properties altered in chemical (pyro-and hydro-) processing will present themselves. In primary grinding, the path to AG/SAG milling will progress with little deviation but opportunities in regrinding are wide open. Flotation will see the trend to designing bubble/particle reactors accelerate simultaneously with a vigorous response from mechanical cell suppliers. Gravity separation remains a bastion of the lone inventor but I anticipate that the new lines will come from the waste management business. I finish by examining the ""research cycle"", identifying growth in small ""high tech"" companies and university research centres.IntroductionI have been asked to offer a personal view of""where we are going in mineral processing?"". Gazing into crystal balls is quite a cottage industry as we approach the end of the millennium. Academics are often asked to assume the role of visionary, I presume because it is considered in their mandate, to reflect and philosophize (or, less charitably, because they are considered to have the time). Since this is the 30th Annual Canadian Mineral Processors Operators Conference, I am tempted to suggest the next 30 years as my frame of reference. This is about equivalent to one engineer's career or, given it takes typically 15 years to go from concept to realization in mineral process engineering (Napier-Munn, l 997a), about 2 ""invention cycles"". With this length of cycle, much that is familiar now will remain so over the 30 years.Research and development (R&D) is in response to need. The overarching need in mining is to find new ore bodies. Process developments cannot compensate for a depleting deposit or a declining commodity price. Mineral processing R&D is characterized by incremental gains, aimed at pushing the mine down the cost per tonne league table. Breakthroughs are the exception (flotation at the turn of the century was one). This must be kept in mind when trying to predict the future in our business."

Jan 1, 1998

By A. J. Sinclair

"Abstract-Geology contributes essential information toward obtaining high-quality resource/reserve estimates. In this context, geology can be considered under the following overlapping topics: regional geology, detailed (deposit) geology, mineralogy, ore deposit models and continuity, with geological mapping being fundamental to all. Each of these topics is considered here in terms of potential contributions to "improved" mineral inventory estimation. Some of the principal conclusions are:1. Regional geological relations must be consistent with deposit geology. It is common that important geological relations are more clearly evident in various regional locales than in highly altered and/or highly deformed mineralized areas containing mineral deposit.2. Detailed geology provides information for a geometric model of a deposit, a model that serves as a basis for mine planning. It is important to distinguish fact from interpretation in such models. Substantial effort is required to characterize the geometric margins of a deposit and the relation of these margins to the simplistic geometric form that normally emerges as an interpretation.3. Mineralogical studies relate to many aspects of deposit evaluation including abundance of ore and deleterious minerals, spatial distribution of ore and deleterious minerals, grain size characteristics of important minerals, mill design, etc.4. Ore deposit models contribute substantially to confidence in developing a three-dimensional geometric model of a deposit for mine planning. Specifically, they are a basis on which to develop rules for interpolation and extrapolation of ore, and they contribute to recognition of domains, each with its own characteristic continuity and margin character.5. Continuity is dependent on mineralization style and may be controlled structurally and/or chemically. It is important to distinguish geological continuity and value continuity. A wide range of classical geological methods are useful in examining geological continuity; value continuity is best viewed as a statistical characteristic that is quantified by any of several measures of autocorrelation."

Jan 1, 1998

By K. D. Card, K. Howard Poulsen

Abstract - The Archean Superior Province craton and the Paleoproterozoic Penokean Orogen are major geological sub-divisions of the southern Canadian Shield and account for much of the metallic mineral production of North America. The Superior Province experienced a mainly Archean history involving several cycles of volcanism, plutonism, and tectonism, primarily in the Neo-archean but also including Meso-archean and Paleo-archean cycles as well. Superior Province consists of northern and southern high-grade gneiss sub-provinces and a broad central region of alternating greenstone-granite and metasedimentary belts. The sub-provinces may represent tectonic terranes assembled in the Archean by accretion processes similar to those of some Phanerozoic orogens. Most of the mineral deposits, including VMS, intrusion-related, and lode gold deposits occur in the greenstone- granite sub-provinces where they were formed in an interval of 100 million years or less around 2.7 Ga. The Paleoproterozoic Penokean Orogen comprises supracrustal sequences deposited in fault-controlled epicratonic and rifted margin settings developed on and about the Superior craton. Deposition of the ~2.4 Ga Huronian Supergroup and its paleoplacer uranium deposits in the eastern Penokean Orogen, and their pre-2.2 Ga deformation, were probably unrelated to the deposition of the ~2.1 Ga Marquette Range and Animikie groups and their major taconite iron formations in the west. However, these sequences were deformed together during the ~1.85 Ga Penokean Orogeny which resulted when an assembly of island arcs containing VMS deposits, the Wisconsin magmatic terrane, collided with the Superior block and its Paleoproterozoic cover. The Sudbury structure with its world class Ni-Cu-PGE ores was also formed at this time, possibly triggered by meteorite impact. Metallogenic patterns in the Paleoproterozoic rocks were controlled by a complex interplay of factors including tectonically controlled variations in deposition and deformation, distribution of mineralization in the Archean basement, and oxyatmoversion, the transition from anoxic to oxygenic atmospheric conditions that occurred during the deposition of these sequences.

Jan 1, 1998

By Marcel Vallée

"Abstract-In recent years, several unsavory events in international mineral exploration, as well as several widely publicized project difficulties and failures have occurred. The report Setting New Standards has "raised the bar" and proclaimed a "commitment to continuous improvement... and change." We need to evolve from our "generally accepted" practices to more effective quality assurance policies, guidelines and standards. Several steps will be required to support the work of the "qualified persons" now wholly entrusted with technical and professional matters:• adopt a mineral development model and objectives appropriate to orient the selection of workmethods and verification procedures suitable to increase the profitability of these activities;• review the definitions and implications of the terms practice, guideline and standard;• review three quality assurance systems with emphasis on commitment of company management and complementary emphasis on systematic quality policies, plans and manuals (ISO 9000), continuous improvement through "profound knowledge" (Deming, 1986), and self-appraisal of continuous improvement and client satisfaction using the Qualimeter Guide (Québec Society for Quality);• determine, from the objectives of the mineral development model proposed and the problems often encountered, the requirements of resource/reserve estimation and the production feasibility study. To regain investors’ confidence and improve the returns from mineral development activities, an explicit commitment to quality by the board of directors and the management of every company is required.A number of mining companies have gained ISO 9002 certification for their operations but exploration companies should start by developing and implementing quality assurance guidelines and standards based on the ISO 9001 pattern, without achieving actual ISO certification in the short term. Both professional associations and industry organizations must be involved in the process of developing the required quality and continuous improvement guidelines and standards."

Jan 1, 1998

By Guocheng Pan

"Although many factors play roles in the estimation of recoverable reserves, smoothing effect and conditional bias are considered major geostatistical issues in the estimation. This paper introduces measures for smoothing effect and conditional bias, and provides insights into their relation to the estimation of recoverable reserves. Both smoothing effect and conditional bias are intrinsic to the information effect and kriging estimators. For a given level of drilling information, however, it is possible to identify the optimal search radius that minimizes conditional bias. Furthermore, it is also feasible to define variance correction factor for reduction of the smoothing effect from exploration block models. Both of these components are key to the accurate estimation of recoverable reserves. IntroductionThe accurate estimation of recoverable reserves is critical to decision making in different phases of feasibility study and mine planning. Much attention for improving the methodology of estimation has been focussed on the effect of the change-of-support (Parker, 1980; Dagdelen, 1996). For example, it is essential to make a volume- variance correction to the estimate of multiple indicator kriging (Hoerger, 1992). When the size of block, b, in the geostatistical model differs from that of selective mining unit (SMU), v, a volume-variance correction is warranted for the prediction of recoverable reserves.Most mining plans and decisions are made prior to the availability of high density blast-hole samples. In most mining operations, the true SMU grade Zv is unknown at the time of selection. Instead, the selection is based on the estimate Z v**derived from high density blast-hole samples within the deposit G. Nevertheless, the estimate Z v * of recoverable reserves in the stage of mine planning is derived from exploration data. At the end, the production result must be reconciled to the estimate Z v * . In other words, the selection is based on Z v** from blast-hole samples, while the final production figures are reconciled to Z v * from exploration drilling. For a given preselected cutoff grade z0, the actual mining panels will consist of the units having the estimated grade Z v** =z0 rather than the true grade Zv =z0. The difference between Z v** and Zv is usually of less concern."

Jan 1, 1998

By R. J. C. MacDonald

"The first recorded discovery of placer gold in Canada was on the Chaudiere River in Quebec's eastern townships in 1832 and the first major production came from placer deposits in British Columbia in 1858 (Verity 1974). Placer deposits were the major source of gold until the late 1890's, although lode deposits were found in Nova Scotia in 1862. In 1896 the Klondike Gold Rush commenced with the discovery of gold by Henderson and Carmack in the Yukon. The peak was reached in 1900 when over one million ounces of gold valued at approximately $22.3 million were recovered. With the exhaustion of the easily accessible deposits, more capital intensive operations were necessary such as those initiated in 1906 by the Yukon Gold Corporation. This giant dredging operation continued to produce until 1966. Today only a few small operations remain.The development of Canadian lode gold mining began in earnest around 1900 when the railroads were opening up the interior and western part of the country. At this time many discoveries occurred, particularly where mineral outcroppings were near surface. Tremendous impetus for exploration and the reopening of former producers followed the elimination of the gold standard by Great Britain around 1931, and more importantly the United States in 1933, with subsequent stabilization of the price of gold at $35 per ounce in 1934. Prior to this the price of gold was basically unchanged since 1717, approximately, $20 per ounce (Verity, 1974; Green, 1973).The depression of the 1930s adversely affected most industries, however for the gold producers it was a very profitable time. Prices of materials and equipment declined and labour was cheap and plentiful. Interest in gold mining was further stimulated in 1936 when a three year tax exemption was declared for all new metal mines. In 1938 a decline in the value of the Canadian dollar relative to the U.S. dollar benefitted the industry. The second world war provided yet again further incentive for gold production and in 1941 Canadian gold production reached a high of approximately 5.4 million ounces. This figure was not surpassed until 1991 when approximately 5.6 million ounces were produced (Natural Resources Canada, 1996 )."

Jan 1, 1998