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Although the effects of sea level changes on ore concentration processes are to some extent obvious with certain deposits, e.g. beach placer deposits, they have been largely overlooked with others such as Mississippi Valley type lead-zinc deposits. It is contended that sea level variations may have more profound effects on a wide range of deposits than has previously been appreciated. These deposits include not only placer'and residual deposits but also stratiform copper deposits, Mississippi Valley type deposits, stratiform manganese deposits and Minette type iron deposits. Sea levels in paralic basins profoundly affect the influx of 'detrital sediment, and this has to be suppressed to allow for the accumulation of thick rich deposits of coal evaporites, phosphate or metalliferous sediment. Emergence can be associated with oxidized waters, erosion, and,solution of soluble rocks. Submergence can reverse the Eh trend and can lead to preservation of ores. Both realms of surficial sedimentary environments and subsurface diagenetic environments can be affected by changes in water pressure, gas pressure (pC02), Eh, pH, and temperature as sea levels fluctuate. Even relatively small sea level changes may have profound effects. For example, there is some evidence to suggest that when the level dropped below 100 metres about 10,000 years ago, the Red Sea became isolated by the sill at Bab el Mandeb in the south, and evaporated away to leave a series of shallow lakes. The Red Sea is 1 to 2 km deep. It was at times such as this that the well-known copper-zinc mineralization developed in the Red Sea trough. Changes in sea level also affect the stability field of gas hydrates which can yield large volumes of gas leading to mass movements on the sea floor (Warnke, 1986).

Jan 1, 1987

By Carlson BL, Overton DD

This paper compares the designs of heap leach facilities for four precious metal mining projects in the southwestern United States. These four proposed projects are of small-to medium-size relative to other operating mines in the United States, and are either permitted or in the final stages of permitting. The differences and similarities in the heap leach facility designs are compared with respect to site conditions, operating conditions and regulatory requirements. This comparison provides a summary of the state-of-practice for heap leach facility design in the southwestern United States and identifies current issues in project development and process material containment.

Jan 1, 1997

By J B. Farrow

The AJ Parker Cooperative Research Centre for Hydrometallurgy carries out research on behalf of, and in collaboration with, the Australian mining industry. As might be expected, much of its research is directed towards improving the efficiency of alumina and gold processing plants. However, the Centre also carries out research of relevance to base and other metal producers. A key element in its work is the successful transfer of its technology to the companies with which it is working. In general, this is achieved in the following five steps:definition of the problem through discussions with the company commissioning the research; execution of the research; assessment of the research findings; testing of the research findings by pilot plant or on-site trials; and implementation of the results on the full-scale. This pattern is exemplified by the work carried out by the Centre to improve the performance of gravity thickeners which are used throughout the minerals industry for solid-liquid separation. The research has focussed mainly on ways to optimise the use of flocculants (long chain polymers) to enhance thickener performance. It has been shown that the way the flocculant is mixed with the slurry is of profound importance. Computational fluid dynamics modelling of the feedwell region of thickeners and laboratory and plant flocculation studies have been used to determine better ways to contact the flocculant with the feed slurry. Implementation of these and other findings on the full-scale confirmed that improvements in thickener performance were indeed possible. As a result of this AMIRA funded thickener technology work, there have been considerable savings to a number of Australian mineral processing companies, through improved operation, higher throughputs and flocculant savings.

Jan 1, 2000

This paper explains why the valuation of mining assets is often a very different exercise from the valuation of the shares in the mining company which owns those assets. The fundamental reason for this is that mining assets, and the shares of the company which owns those assets have different risks. In order to properly value mining securities it is essential to: ò ensure all the different risks and other factors which impact on the value of the mining assets and the value of the shares are taken into account; and determine the extent to which the different risks and other factors are addressed in the value of the mining assets and the value of the shares so as to avoid double counting or not counting at all. If the alternative, but far from consensus, view is accepted that the correct valuation methodology to apply to shares in mining companies should be based on option pricing theory then conventional valuation practice of both mining assets and shares in mining companies will need to be fundamentally reassessed.

Jan 1, 1994

By I P. W Chau

Construction of twin stacked railway tunnels through mixed ground conditions in the heavily populated urban environment of Hong Kong, including tunnelling in poor ground conditions, with low cover and under or adjacent to sensitive structures with minimal impact was the challenge presented by the tunnelling section of the Kowloon Southern Link project. This paper details how twin 1.1 km tunnels of 7.0 m internal diameter were driven by Mixshield tunnel boring machine (TBM) in mixed ground through one of the exclusive shopping and hotel districts in Kowloon. The paper addresses the challenges required to be considered and managed for the success of the project, including ground conditions, TBM selection, Mixshield TBM operation, settlement monitoring and control, ground- borne noise and vibration, proximity to utilities, buildings, roads and operating railways.

Jan 1, 2008

By McIlveen GR

The water pollution hazard posed by the derelict Conrad mine site, to the water and associated stream sediment of Borah and Maids Creeks and the nearby Copeton Dam storage, has been assessed. Mine water, tailings and tailings dump leachate have polluted water and stream sediments in Borah Creek downstream of the mine site. Acidity, arsenic, copper, lead, iron, silver and zinc are the principal pollutants. Under dry and low flow conditions, mine water was found to be the dominant polluting source, however, leachate and run-off from tailings dumps were also significant under and following wet conditions. Soluble arsenic, lead, iron and silver species in mine water and leachate were found to be rapidly incorporated into sediments, but acidity, copper, and zinc persisted in the creek water. Under low flow conditions, the water of Maids Creek is polluted with copper and zinc (up to 4.4 and 34 mg/l for copper and zinc respectively) and the pH is decreased (from pH 5 - 7 to pH 3 - 6) by entry of Borah Creek water. Values found in Maids Creek were variable and related to flow regime and distance downstream from Borah Creek confluence. Water in Copeton Dam storage, having a much larger volume of water with a higher bicarbonate buffering capacity (50mg/l versus 15mg/1), is not affected by entry of Maids Creek water. Polluted sediment from Borah Creek has contaminated Maids Creek for 2km downstream to Copeton Dam storage. Stream sediment downstream of the Borah Creek confluence, contains up to 1.0% As and 1.4% Pb in the less than 200 micron size fraction. Under high flow conditions, arsenic was found to be moved out from the mine site as insoluble species, associated with suspended sediment in Run-off.

Jan 1, 1988

Western Mining Corporation (W.M.C.) operates a nickel refinery at Kwinana, 30 km south of Perth. The refinery commenced pro- duction in May 1970, with a rated capacity of 15 000 tpa of nickel metal. A hydrometallurgical route was chosen as the most expedient way to produce nickel metal at a time when world demand for nickel was outstripping the supply. Later events dictated that an increase in production from the refinery be achieved. To this end, matte produced from Kalgoorlie Nickel Smelter, which was commissioned in 1972, was used in varying proportions as a complement to the concentrate initially utilised as input to the refinery. The effect of matte addition was to increase the capacity to 30 000 tonnes of nickel per annum. This was accompanied by other benefits which were 1. reduction in energy consumption per unit of nickel produced, 2. improved metal extraction, 3. improved precious metal recovery, 4. reduced production of ammonium sulphate by-product. Refinery operating results for the years 1970 to 1983 show how matte feed has improved refinery performance in these areas.

Jan 1, 1984

By Rieniets S, Somerville J. L

In Morwell Open Cut brown coal mine, the overburden 'firehole' materials which have resulted from ancient coal fires vary-from hard baked clays to firm laminated lacustrine clays. The need to pre-strip designated areas to reduce the slope height and attain safe digging conditions for the bucket wheel excavator operation is now accepted practice at the open cut mine. In this study, the inherent spatial variability of undrained shear strength of the clay materials has been incorporated in a visco plastic, finite element based, probabilistic slope stability analysis. Data on the costs of initial pre-stripping, excavation and slope failure are collected to provide an economic basis for the optimisation of the design of the overburden batters in Morwell Open Cut. This improved stability modelling is enabling costly pre-stripping to be minimised while ensuring acceptable slope stability conditions and minimising the risk to personnel and plant.

Jan 1, 1994

By G C. Kiel, G J. Nicholson

Corporate governance has never been more topical. A glance at any major newspaper or business publication will reveal a litany of corporate failures based upon the governance of the organisations involved (eg Byrne, 2002; Hayes, 2002; The Economist, 2002). The increased compliance requirements and speculative nature of our industry means that corporate governance systems are, if anything, more important than in the general business community (Arthur, 2001). Rather than focus exclusively on the contribution of governance to corporate failure within the mining industry, however, our objective in this paper is to examine how boards can add value to the corporations that they govern. In order to highlight how a board can add value to a company, we commence by outlining the role of the board in the modern corporation in general and the mining industry in particular. We then introduce the concept of shareholder value and identify the steps on which a board needs to focus to enhance shareholder value through value tracking processes. Our discussion pays particular attention to the importance of organisational culture to the companyÆs activities and utilises three case studies from the mining industry. We conclude with an overview of what mining boards can do to enhance their culture and drive performance changes for the benefit of the companies they govern.

Jan 1, 2002

By G Mulder, M Adams

Since the introduction of raiseboring 30 years ago there have been many operational and mechanical design improvements in the raiseboring machine, its reamers and associated cutters. These have now made the technology of raiseboring a routine and practical operation within the underground mining world. Over the last decade these advances have been aided by the introduction of robust automation packages which have allowed unattended drilling and reaming, real time performance monitoring and enhancement and the rapid diagnostic investigation of mechanical and electrical abnormalities. The constraint to higher raiseboring performance is now the drill string. However when it comes to a cost-effective solution of applying the high drill string torque and tension necessary for the next step change in performance, designers have æhit the wallÆ. Whilst carbon fiber reinforced plastic composites with abrasive resistant sheaths may offer a solution, the limit of conventional steel, drill string technology has been reached. This limit to advancement is however based on the drill string being in tension and alternative solutions may exist by literally turning the raiseboring paradigm on its head. This paper describes the story of a small Australian company engaged in the design and manufacture of mechanical excavation machines, two Australian raiseboring contractors and three Australian mines going against tradition and pushing down rather than pulling up.

Jan 1, 1998

Mining of the silver-lead-zinc orebodies at the George Fisher Mine officially started in 2000. A review of mining performance to date shows that many of the extracted primary stopes have experienced some degree of hangingwall dilution. The degree of hangingwall failure in the stopes became progressively more extensive throughout mining of the orebodies in 2001 and 2002, culminating in the unplanned catastrophic failure of the 744D stope in which the ore between 13C (2683RL) and 12L (2714RL) sublevels caved into the previously mined cavity between 13L (2654RL) and 13C sublevels. This was followed several months later by another unplanned caving event in a nearby stope, 740D. As a direct result of these unplanned failures it was decided to mine the stopes with a smaller span than had been previously planned and in a primary-secondary pyramidal stoping sequence. To limit the exposure of the stope hangingwall, a hangingwall drive is no longer developed and therefore geologists no longer have access to the detailed geological information that this provided. Geologists at George Fisher Mine have had to be adaptable and flexible in response to these proposed changes and rely more on data from drilling than mapping for their geological interpretation. The result is that the drilling cycle has become much more critical in the planning process.

Jan 1, 2003

In-pit crushing systems have been known in the mining industry for many decades. The question whether in-pit crushing is a viable option has often been asked. More than 200 mobile and semi mobile crushing systems have been installed worldwide at various locations and applications. Economic pressures have forced mine operators to reconsider the use of a conventional truck-shovel operation and have contributed enormously to the development of in-pit crushing and conveying systems. The in-pit crushing concepts have varying mobility capabilities. These range from fixed, stationary crushing plants to semi-mobile and fully mobile crushing plants. All these systems are operated in connection with a conveying system. In general in-pit crushing systems have technical and economical cost advantages over truck-shovel operation, particularly as mine capacities increase and mines become deeper. The integration of an in-pit crushing system represents a significant up-front capital investment and the mine is only able to depreciate the capital investment over a sufficient mine life including plant capacity to realise the benefit of the much lower operating cost.

Jan 1, 2003

By Kane, M O&apos

The mineralised members of the Brockman Iron Formation mined at Mt Whaleback are overlain and underlain by shale horizons. To maximise resource recovery, waste movement within the life of mine plan will total approximately 3.3 billion tonnes. Approximately 15 per cent of waste materials contain zones with varying amounts of sulfides and carbon and are referred to as æreactive shaleÆ. Reactive shale has the potential to self-heat and can react with some explosives, resulting in spontaneous explosion. Sulfide rich zones also have the potential to generate acid rock drainage (ARD). Successful mining of reactive shale requires constant co-ordination between the geology, mine planning, mining and environment departments. Safe storage of reactive shale is the focus of ongoing research. Since the mid-1990s, a number of trials have been undertaken at Mt Whaleback in order to further the understanding of the physical and chemical properties of reactive shale. This paper summarises some of these trials, and discusses key learnings arising from interpretation of results. Ultimately, the learnings from this research will provide the guidelines for successful storage of reactive shale.

Jan 1, 2003

Structure is the most important control on the location of hematite deposits in the Hamersley Province in the Pilbara region of Western Australia. Unravelling the structural history of mineralised areas, however, is complex because the Province underwent three orogenic events, and three regional extension events followed the main episodes of compression. Steeply E to ENE dipping normal faults immediately predated deposition of the Beasley Quartzite of the lower Wyloo Group after the Ophthalmian Orogeny. Steeply NE and SW-S dipping normal faults predated deposition of the McGrath formation of the middle Wyloo Group, following the Panhandle Orogeny. The resulting interpreted rift was subsequently reactivated and tilted during the Capricorn Orogeny. Late NE trending normal faults are confined to the eastern half of the Province. High-grade hematite deposits occur in rocks that range from intensely folded (Mt Whaleback, Giles Mini) to rocks with less, or only little deformation (Paraburdoo, Channar), suggesting that folding had at best limited influence on ore genesis. In contrast, extensional normal faults are always associated with high-grade hematite deposits, and in particular faults that link the underlying dolomites of the Wittenoom Formation with the overlying iron formation, thus providing a pathway for mineralising alkaline fluids.

Jan 1, 2005

By R Balusu, P Humphries

In combination with detailed field studies and goaf gas characterisation, computational fluid dynamics (CFD) models have been used to develop optimum and effective strategies for inertisation during longwall sealing operations to achieve goaf inertisation within a few hours of panel seal-off operation. This study has combined detailed analysis of the performance of various inertisation field trials together with CFD modelling results of different inertisation operations in order to develop the optimum inertisation strategies. A number of parametric studies were conducted on the base case CFD models that had been calibrated and validated based on the information obtained from previous inertisation studies and goaf gas monitoring. These studies included changes in inert gas injection locations, inert gas flow rates, seam gradients, and different inertisation strategies to investigate their effect on goaf inertisation. Studies indicate that the strategy of inert gas injection through the MG seal was not as effective as the alternative strategy of inert gas injection at 200 m behind the face. Innovative inertisation strategies have been developed and subsequently implemented at an underground coal mine in Australia. Further investigations have been carried out in the development and demonstration of proactive inertisation strategies with the objective to suppress the occurrence of spontaneous heatings in active longwall faces, in particular under unexpected scenarios such as during slow retreat/face stoppage due to difficult geological conditions. Initial trials at two Australian longwall panels have demonstrated the great potential of this practice to contain the onset of heatings in the goaf.

Jan 1, 2005

By J du Plessis, W Marx

The FutureMine Collaborative Research Initiative has been successfully completed after three years of activity. The main objective of this initiative was to provide applications of research previously undertaken in the DeepMine initiative in terms of realistic solutions to problems facing gold mining operations as they reach for depths beyond 3500 m below surface. The FutureMine initiative was subdivided into four broad streams of technological expertise: rock engineering and seismicity; mining engineering and orebody management; software and communications and ventilation, cooling and refrigeration. This paper presents a summary of research output in this last area of expertise. Broadly, research in mine ventilation, cooling and refrigeration was directed in areas related to the recirculation of air, cyclical use of ventilation and cooling systems, air scrubbing technology, optimisation of chilled water reticulation, obtaining direct cooling at the workface, improving underground refrigeration systems through dry air-cooling and water heat rejection systems and a number of software simulation programs to be used in specific applications and as a tool assisting real-time monitoring of underground environmental conditions.This paper describes in broad terms the outcomes from this section of the research program and proposes ways in which some of these technologies may be combined synergistically in novel systems aimed at maintaining acceptable environmental conditions while reducing the impact on the profitability of operations.

Jan 1, 2005

By Wilson PH

A research programme sponsored through the Australian Mineral Industries Research Association investigated two aspects of mine aerodynamics on model scale. These were aero- dynamic losses in (a) shaft/airway intersections and (b) losses created by mine cages moving in a combined haulage/ventilation shaft. The shaft/airway intersections studied included base and intermediate levels for both upcast and downcast. shafts, with one to four rectangular airways intersecting a circular shaft. Changes in intersection geometry were limited to the installation of 45¦ conical brow cutoffs of varying size and the addition of simple flow control devices. The relative air- flows between the airways and the downstream shaft were varied over a range employed in Australian mining practice. In general, experiments revealed that a small brow cutoff was significantly better than none at all, and a simple device such as a cone can reduce losses and improve flow stability at an intersection. The mine cage studies determined the effect on aerodynamic loss of cage area blockage, height/length ratio, openings in cage walls and surface roughness due to external structural members. The results show that in a combined haul- age/ventilation shaft, when the relative air

Jan 1, 1978

By Northcote GG

There are many underground mines with shaft or decline access with limited production capacity or where the mine may become uneconomical as trucking costs escalate with increasing depth of the decline. In such cases a need may exist for a shaft hoisting system which can be constructed more quickly and more economically than a shaft sunk by conventional methods. Relatively cheap small diameter shafts can be constructed by raise boring. This paper describes a simple hoisting system which has been designed to take advantage of the benefits of raise boring. The system uses twin bored raises with a double drum winder hoisting a skip in each hole. The design concept is based on 1. accepting that the raises cannot be truly straight or vertical, 2. using the raise to guide the conveyance, and 3. minimising operating, maintenance, and capital costs. The hoisting system requires a certain degree of accuracy in the alignment of the twin raises. A survey of raise boring practice showed that the required accuracy could probably be achieved with conventional techniques. However it was thought it would be necessary to survey the pilot hole during drilling and to be able to correct the hole if deviation became

Jan 1, 1978

By D Schwab, R M. Tosdal

The Quesnell-Stikine arcs, in the Canadian Cordillera, are host to Triassic and Early Jurassic alkalic porphyry Cu-Au and calc-alkalic porphyry Cu-(Mo-Au) deposits formed outboard of ancestralNorth America in island-arc tectonic settings (McMillan, 1991). The majority of the alkalic porphyry Cu-Au deposits are products of a discrete magmatic event at the end of the Triassic, with a second and smaller event in the Early Jurassic (Mortensen, Ghosh and Ferri, 1995). Of the Triassic complexes, the Galore Creek alkalic intrusive suite is one of the largest and most silica-undersaturated intrusive complexes, and host to the most significant undeveloped alkalic porphyry Cu-Au resource in North America (Lang, Stanley and Thompson, 1995). Because of the common presence of feldspathoidal-bearing rocks in the complex (Enns et al, 1995), Galore Creek likely represents an end member example of the alkalic porphyry Cu-Au class. The Galore Creek alkalic Cu-Au-Ag porphyry district, located in NW British Columbia (Canada), contains 12 mineralised prospects (Enns et al, 1995; Micko et al, 2007; Schwab et al, in press) with a total measured and indicated resources of 785.7 Mt at 0.52 per cent Cu, 0.29 g/t Au and 4.87 g/t Ag (NovaGold Resources Inc, February, 2008). The Central Zone is the largest and best delineated. Other economically important mineralised centres include the South-West, Bountiful, West Fork and Junction deposits. The South-West Zone, the focus of this contribution, is a Cu-Au-Ag breccia-centred deposit with a measured and indicated resource of 69 Mt grading 0.42 per cent Cu, 0.69 g/t Au, 2.67 g/t Ag. Hosted in brecciated intrusive rocks, the South-West Zone is distinctly younger than the Central Zone and most of the other mineralised centres (Enns et al, 1995; Schwab et al, in press). The South-West Zone therefore preserves the late stages of hydrothermal evolution at Galore Creek. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Daziel M, Corke P

Unit cycles in mining have not changed for many years. Productivity increases over the past three decades have mainly been achieved by using larger and heavier machines. This investment in size has probably reached the point of diminishing returns and increased productivity in the future will have to be generated by other means. One way of achieving this is through automation of selected unit operations, eg dragline overburden removal, truck haulage, ground support installation and secondary breakage. Although, in the past few years, there has been significant progress in this direction, we are still a long way away from even partial automation - especially in hard rock mines. This paper addresses the technical obstacles facing mining automation; suggests ways by which these obstacles may be overcome and identifies the role of industry groups and research providers in this process.

Jan 1, 1997