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The perception of the mining industry in the Australian community has changed considerably over the last four decades. This has been partly brought about by changing values and expectations of the Australian community as well as by global factors. The legal environment for the Australian mining industry has undergone significant changes. Among them, the High Court's Mabo decision which confirmed native title rights as part of the common law and environmental legal developments are dealt with particularly. It is suggested that the Australian legal environment is not necessarily the prime cause for Australian mining companies taking their investment off shore. This is a summary on how native title impacts on land tenements and some of the major issues that emerged since the `Mabo decision' and the Native Title Act 1993 are discussed. Environmental legal developments have resulted in liability facing directors and senior management in compliance matters .and in operating mining and other businesses because of changes in community expectations. In the next decade it is suggested there will be many drivers for more changes in the legal environment. Some of these are touched on including the changing roles of the Commonwealth and State Governments, the High Court as -law-makers and the changing relationships with indigenous people in Australia and in overseas countries. The changing legal environment for mining demands a national approach in many areas on the proposition that resource based industries are part of a national industry. The uniform law approach among the States has been taking place but this needs to further. An appropriate task force should be forward to review the entire legal structure and regulations affecting mining on a national rather than a State basis . The mining industry will need to work with expectations of a changing community which have powerful, but sometimes contradictory, interest groups.

Jan 1, 1997

With the advent of the resources boom in the late-1960s most of the larger scale resources projects in Australasia were commissioned on an æowner miningÆ basis, where the mine owners owned and operated the primary mining equipment. Then, in the 1980s with the arrival of the gold mining boom in Western Australia and elsewhere, a change occurred û most of the mining activities were carried out on a contract mining basis. Over recent years, however, there has been a marked trend amongst larger Australasian open pit mining operations back towards owner-controlled and operated mining operations. The reasons for this are many and are addressed in the paper, but centre on the concept of the owner being prepared to assume more of the mining risk in exchange for the advantage of not having to pay a contractorÆs profit margin. Where mining contracts are entered into, the older æschedule of ratesÆ format is being replaced with less adversarial and more entrepreneurial contract alternatives involving operating cost and risk sharing in a spirit of æfair dealingÆ. Leasing and maintenance issues have also been influenced in recent years by the advent of more flexible contract arrangements with equipment suppliers. Group purchasing has also had some influence for project operators. For many mine owners, the optimal risk management profile involves a practical offsetting of the assumption of mining risk on the one hand, against the removal of litigation risk and potentially reduced operating costs on the other. Potential pitfalls may arise where equipment size and type requirements vary with time or where manpower management, mining flexibility, job skills or safety exposure factors are relevant. These issues are commented on in the context of some well known examples, and an update is provided on contract mining versus owner operation in large-scale Australasian open pit mining generally.

Jan 1, 2002

By Howard G. L

The gold treatment plant of Great Western Consolidated N.L. is at Bullfinch, Western Australia, 22 miles north of Southern Cross, which is 100 miles west of Kalgoorlie. A railway to Southern Cross connects the mine with the main Perth-Kalgoorlie line.The plant, which commenced operations on the 31st October, 1952, was, designed by Messrs. Alex: Stewart & Co. in consultation with the technical staff of Western Mining Corporation Ltd. to treat 1,000 long tons a day, made up of approximately equal parts of quarry oxidized ore and underground sulphide ore, by moderately coarse grinding (2-3 per cent plus 65 mesh Tyler) and straight cyanidation without straking. The design had to allow for future treatment of all sulphide ore at the rate of 40,000 tons per 28-day periodand to make provision for the possible later inclusion of preaeration treatment.The test work on .which design was based was done on representative development samples, the mine being divided into zones for this purpose, to check possible local variations from average treatment behaviour. Proposed mill feed mixtures were made up from time to time for complete ore dressing tests, which were conducted in the Western Mining Corporation laboratory at Kalgoorlie.The chief feature of the design was that the plant had to handle the extremes of very soft, poor settling and filtering oxidized ore and very hard, good settling and filtering sulphide ore. On one hand, crushers and mills had to be large enough to handle the sulphide ore and on the other, thickeners and filters had to be large enough to handle the oxidized ores.The design is marked by simplicity, the use of large units of equipment, and flexibility to cope with a variety of ores.

Jan 1, 1956

By P F. Knights

Mining companies are striving to achieve new levels of operational maturity and drive process improvement across the organisation in the face of unprecedented demand and limited supply of experienced human resources. Advanced analytics techniques can help overcome these fundamental challenges by applying data techniques not previously applied in mining. Today, decisions are usually locally optimised but do not achieve optimum capability for the value chain. Although more information is collected then ever before, it is difficult to link many sources of data together in the same place in real-time, for example plant history, maintenance, mine planning, logistics and engineering data. Consequently complex analysis of data is time consuming and requires specialist skills and knowledge, and is often neglected in the decision-making process. In the future, analytics will close the loop between analysing data and taking action. Analytics will become embedded in the business and routinely applied to improve decision making across the organisation, from senior management to operations and maintenance workers, but will not require specialist skills or be time consuming to analyse data. As analytics becomes embedded in the business process, decisions are supported by data (not on gut feel), and critically, data from many sources are integrated in real-time to improve the quality of decisions. Ultimately, predictive tools will help suggest, or even in some cases automate, courses of action. The main opportunities for analytics exist where the enterprise requires supporting technology to enable it to continue to evolve to higher level of maturity. This will be in the areas of asset management, rapid reconciliation and adaptive planning, and the inbound and outbound supply chains. Advanced analytics are also a key enabler for increasing the effectiveness and realising the true value of Remote Operations Centres to safely and efficiently support operations in remote locations with smaller workforces.

Jan 1, 2008

By Heyes GW, Orrock GI

The fine grained complex orebody at Elura contains galena, silver and sphalerite in a matrix which is mostly pyrite; sulphides account for about 90% of the orebody. A differential flotation circuit is operated to con- centrate lead and silver in the first section and zinc in the second. The metallurgical performance to date indicates the need for improvement. The lead section has been sampled in detail to comprehensively assess its overall performance and to define problems associated with lead and silver flotation. The substantial amount of pyrite in the feed dominated the perfor- mance of each stage of the separation. It was responsible for extensive dilution of all concentrates and, as a consequence, for very large circulating loads. The rougher concentrate contained 68% pyrite some of which was rejected through the three stages of cleaning to 39% in the final concen- trate. However, this was still sufficient to hold the assay of this product below 45% Pb. Size by size behaviour shows that flotation rates of the valuable minerals, as characterised by their rate coefficients, were low through- out the circuit. There was a significant deterioration in these rates between rougher and cleaner I stages which resulted in large circulating loads between these stages. There was practically no recovery of coarse valu- able minerals to the final concentrate. The dilution of the final concen- trate by non-sulphide gangue was not a major problem. If the recovery of the galena and silver in the +38¦m size range could be raised to that of the - 381Lm size range, galena recovery would rise from 78% to 86% and silver recovery would improve from 46% to 59%. The Pb grade of the final concentrate would remain the same.

Jan 1, 1988

By Z Chang, S A. Mrozek, S Windle

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. It is important to understand skarn-porphyry transitions in order to use exposed skarns to look for associated and potentially larger porphyries. For such purposes, a good start is to understand the transition between porphyry and skarn in known deposits. In this contribution, we report the transition at Antamina, Peru, where skarns occur in and around a Miocene complex comprised of more than seven porphyritic intrusions. There are three types of skarn-porphyry relationships. The earliest intrusive phase, P1A, contains both endoskarn and porphyry-style quartz veins with secondary biotite halos. The porphyry quartz veins and endoskarns formed at the same time. Locally, the intrusion contains only endoskarn without porphyry quartz veins and is surrounded by exoskarns in carbonate wall rocks. In the third scenario, later porphyry (P2) intruding into P1A porphyry and skarns related to P1A contains abundant granular quartz veins and secondary biotite alteration but does not have significant endoskarn. The granular quartz veins also extend into earlier P1A skarns. The scarcity of endoskarn associated with P2 is related to the supply of Ca. The earliest P1A intrusion intruded into carbonates that supplied abundant Ca, therefore both endoskarns and exoskarns formed. In contrast, where the wall rocks of the later P2 intrusion are P1A or skarn related to P1A, there was little free Ca, therefore only porphyry-style quartz veins formed.CITATION:Chang, Z, Mrozek, S A, Meinert, L D and Windle, S, 2015. Skarn-porphyry transition – an example from the Antamina skarn, Peru, in Proceedings PACRIM 2015 Congress, pp 409–414 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

Pasminco is actively addressing the optimal utilisation of the known orebody at the Broken Hill mine, in addition to actively exploring for economic mineralisation in the region. As part of the policy of better utilising the known mineralisation a major upgrade of geological systems at the mine was initiated. The software chosen for this change was Maptek's Vulcan, mainly because of the ease of use of this package. Rather than having numerous data sources in varying software packages the mine aimed to limit interfaces and packages. The decision to upgrade the mine's software was not taken lightly, especially in view of the inature stage of Broken Hill mining operations. However, the current mine life of Pasminco Broken Hill mine is I I years, which is longer than many new mines setting up in Australia today. Also, a more sophisticated system brings with it a better understanding of the economic mineralisation, possibly extending the mine life further. The process of moving the Broken Hill databases into Vulcan was a huge task which included, database transfer, digitising, wire framing, modelling and eventually ore resource calculation. To ensure the validity of the new ore resource accounting system, the existing system was run as a duplicate for the introductory year, providing a comparison and if necessary a safety net. The benefits of such a change, however, became apparent almost immediately. Area geologists realised the opportunity to revise geological interpretations in their areas of responsibility, enabling them to obtain a better understanding of orebody morphology. Three- diniensional analysis provides an excellent method by which review of ore targets both in the underground and mine lease exploration areas can he made. As each new find of mineralisation enters the system and hopefully extends the mine life, the opportunities for further mineral exploration in Broken Hill area by Pasminco are enhanced.

Jan 1, 1997

By B Menzel, M Wlasenko, J Phillips

Yandicoogina (Yandi) open pit mine is located in the eastern part of the Pilbara region of Western Australia. It hosts pisolitic iron-oxide mineralisation distributed within a meandering paleoriver channel. The deposit is characterised by clays occurring as lenses, accretions, desiccation joint infill and voids in the pisolite ore. The irregular shapes and highly erratic distribution of these clay pods represent a serious challenge for grade control at this mine.The current grade control approach used at the Yandi mine is based on sampling of production blastholes on a 6 m X 6 m spacing. Their good spatial coverage, tight spacing and low cost make blastholes a very convenient media for grade control and ore-waste definition. However the potential downside of this grade control approach is poor sample representivity. An alternative grade control approach is to drill and sample using reverse circulation (RC) holes distributed on a 25 m X 25 m grid. This approach has been tested in Yandi mine and compared with the blasthole sampling approach for sample representivity. The impact of increased drill spacing on mining block predictions has been studied using a conditional simulation technique. Blasthole and RC samples proved to be similarly biased, underestimating Al2O3 and SiO2 grades and overestimating Fe grades, when compared to full cone assays. These results show that using RC drilling for grade control at the Yandi open pit will not necessarily improve the representivity of the grade control samples. However, increasing the grade control spacing to 25 m X 25 m will lead to more than 12 per cent of the selective mining unit (SMU) sized blocks being misclassified. This is approximately a two-fold increase in the number of misclassified SMU blocks in comparison with 5 m X 5 m spacing.

Jan 1, 2007

By Moorrees C

Tests show how that temperature and rate of sparging to remove carbon dioxide determine the rate of precipitation and the chemical and physical properties of hydrated magnesium carbonates precipitated from clarified magnesium bicarbonate liquors derived from crude magnesia. At temperatures above 55°C the product is largely in the form ofhydromagnesite, Mg5(C03)4(OH)2.4H2O Between I5°C and 55°C the major product is nesquehonite, MgCO3·3H2O, although partial hydromagnesite precipitation can be induced by a high rate of aeration.As a result of the reduced time required to bring about greater than 95 per cent magnesium precipitation, the higher MgO content of the product, the ease of product recovery from the precipitation vessel, and the lower energy requirement for thermal decomposition of the precipitate to magnesia, it is preferable to precipitate hydromagnesite rather than nesquehonite. Moreover, the magnesia produced from hydromagnesite is somewhat more reactive than that formed from nesquehonite.Using precipitate calcination temperatures less than 1000°C, the chemical reactivities of the magnesias formed from both precipitates are greater than those of the crude magnesias derived from Savage River magnesite itself. The magnesias would be suitable for most uses developed for caustic-calcined magnesia. However, for refractory brick manufacture, it would be necessary to briquelle the caustic-calcined magnesia. adjust the CaO and SiO2 contents and sinter at temperatures in excess of 1600°C. This would bring about an increase in the bulk density and induce the appropriate chemical bonding reactions.Dead-burned magnesia produced from Savage River magnesite by the calcination/carbon dioxide route would have very low B2O3 contents, typically less than 0.0001 per cent.

Jan 1, 1985

By U Rehm

The biggest hard rock double-shield tunnel boring machine (TBM) in the world, with a diameter of 12.4 m, is currently excavating the North-South Bypass, which includes a crossing under the Brisbane River, Brisbane, Australia, to relieve the often congested road traffic in the city centre. Ten years ago a 10.7 m Mixshield giant helped to handle the Olympic Games in Sydney linking the airport with the city centre for an improved transportation of fascinated visitors. In Shanghai, currently the biggest TBM in the world with 15.43 m diameter presents excellent performance rates; and in Paris a convertible Mixshield could be quickly changed from earth pressure balanced (EPB) to slurry type in order to handle the very heterogeneous ground conditions. In Madrid a 15.2 m EPB giant finished its tunnel job four months ahead of schedule. Large-scale TBMs have proved their economic and innovative potential to create the current and future underground architecture of mega-cities. TBM technology has made further large innovative steps in the last decade. State-of-the-art is a TBM for very heterogeneous ground conditions comprising hard and soft rock with additional high groundwater pressure. The machine concept is adapted to the various ground conditions and allows for a quick and flexible application. Ground treatment by means of additives developed to a helpful tool in this connection. To meet the special challenges of urban tunnel projects of nowadays it is of very high importance, beside applying highest developed technology of TBM, to have a comprehensive technical support during the project phase and to develop positive relationships between all participants of the project which last longer than only for one project.

Jan 1, 2008

In 1948, it became clear that the ventilation system of The Zinc Corporation Limited and New Broken Hill Consolidated Limited mines, would be inadequate for future operations. The,paper describes in detail the process of designing an entirely new ventilation system for a large underground mining operation. The system was based on a single new upcast airway to be located on the boundary of the two properties, which were to be ventilated in parallel as two separate ventilating districts.From calculations of resistance, and assessments of future air requirements, the duties of a new exhaust fan to be located on the collar of the upcast airway were specified as 700,000 cubic feet per minute at 2·6 in. w.g. total pressure for initial operation in 1953 increasing to a maximum of 900,000 c.f.m. at 3·6 in. w:g. total pressure ten years later. The economic size of the new airway was calculated from a consideration of the first thirty years operation of the system, and it was decided to provide a 20 ft. diameter concrete-lined shaft.The new system went into operation five years after the initial planning, and the effect of the difference between actual and predicted rates and distribution or production are discussed. The final result was entirely satisfactory.INTRODUCTIONThe first proposal for an investigation of The Zinc Corporation Limited-New Broken Hill Consolidated Limited ventilation system with a view to putting it on a proper technical basis was made in 1938. A new Main Shaft was then being sunk, and it was decided to postpone the enquiry until this had been completed to No. 14 Level, when operations would be temporarily suspended and the shaft commence to operate as a major airway. The investigation was completed early in 1940, when Z.C. Ltd. upcast fan was...

Jan 1, 1956

By A Cheatle

GoldcorpÆs Musselwhite mine in north-western Ontario, Canada has in recent years become a world-class deposit. Initially discovered in the early 1960s by Alan and Harold Musselwhite, the then marginal mine eventually started production in 1997 and has to date produced 2.6 Moz of gold. Two million ounces of gold are currently classified as Mineral Reserve and a further 1.2 Moz of gold are classified in the Mineral Resource category for a total gold inventory approaching 6 Moz. Growth of the mineral inventory has been achieved through the successful implementation of strategic planning that sought to extend the mine life through discovery of additional economic zones and increased mined tonnages. Accelerated exploration activity commenced in 2001, at a time when gold price was at its lowest in decades. Focus was placed on building, developing and retaining a highly skilled geological team, maintaining purpose, conducting external reviews and developing a new geological model through research partnerships. Ongoing collaborative research between Lakehead University and Musselwhite mine has seen the development of new structural and geological models through post-graduate and academic studies. Research has included lithogeochemical, stable isotope and structural and metamorphic studies and has led to the evolution of a new mineralisation model (for the mine) and the recognition of brittle and ductile deformation regimes within the mineralised horizons. Exploration drilling continues to provide support for the new geologic model. Gold discoveries have extended known mineralisation 2.3 km along strike from mineral reserves and laterally into parallel zones. The exploration potential to further increase production rates, Mineral Reserves and Resources remains very positive and increases in overall gold inventory are likely. Musselwhite mine has significantly exceeded initial projections for a ten year life-of-mine and a marginal existence.

Jan 1, 2009

By H Arvidson, D Guibal

This paper presents updated interpretations of controls on mineralisation in C Deposit and highlights structural features that influence the geometry of mineralisation domains used in resource estimation. The Area C mining lease is located in the central Hamersley Province, ~100 km WNW of Newman, Western Australia, and contains resources of approximately 1100 Mt of Marra Mamba and Brockman iron mineralisation. C Deposit is located within Area C, on the northern limb of the Weeli Wolli anticline, and mineralisation is hosted predominantly in the Mt Newman Member of the Marra Mamba Formation. Production from C Deposit began in August 2003, following mining of a 950 000 tonne bulk sample in 2002. Recent mapping in the bulk-sample pit and updated interpretations by BHP Billiton geologists have highlighted the significance of structural controls on mineralisation in C Deposit and their influence on the thickness of mineralisation, which ranges from 20 to 80 metres. Structural controls on the geometry and continuity of mineralised domains include south-dipping thrust faults that developed along the Mount Newman/West Angela contact, folds associated with thrust fault development, steeply dipping stratigraphic contacts in the hanging wall of the thrust faults, and gently north-dipping stratigraphic contacts. Thrust faults and folds in C Deposit are significant for two main reasons: their formation resulted in the thickening of the main ore-hosting units in the Mount Newman Member; and faults and folded stratigraphic contacts provided conduits for supergene metasomatic-enrichment processes that produce high-grade iron mineralisation.The implications of this interpretation for the definition of the resource estimation domains are discussed, and suggestions are made for a better integration of geology into the data acquisition and estimation process.

Jan 1, 2005

BHP is the world's largest copper concentrate producer with production from mines at Escondida (Chile), Ok Tedi (Papua New Guinea), and Island Copper (Canada). The entire concentrate production is further processed into refined copper by third-party smelters around the world. In anticipation of an expansion in the global copper concentrate production capacity and a corresponding increase in treatment and refining charges by copper smelters, BHP has continuously evaluated various opportunities for downstream copper processing. An expansion in the Escondida mine production, combined with BHP's interest in processing some of its concentrate production on-shore in Chile, ultimately resulted in the development of the Escondida Leach Process. This process was specifically developed for higher grade concentrates, such as from Escondida. An ammoniacal lixiviant and air are used under ambient conditions to leach less than one-half of the contained copper values. After solid-liquid separation, the solution is subjected to solvent extraction regenerating the ammoniacal lixiviant and the copper loaded organic phase is stripped in spent electrolyte returned from the electrowinning plant where ultra-high quality SX-EW copper is produced. The solid leach residue can, if required, be upgraded by flotation to produce a high-grade copper concentrate with improved fuel values and a pyrite tail for disposal. After an 18-month bench and pilot plant scale program and an engineering feasibility study, Minera Escondida Limitada decided to build an 80 000 tonnes of copper per year facility near Antofagasta, Chile. The installed investment cost amounted to around $160 million. The plant went into commercial production in November 1994 and better than 99.9995 per cent Cu cathodes were produced right from the start. BHP believes that the process and the commercial plant are an excellent example of a novel approach advancing the science of copper metallurgy in harmony with present demands for environmentally sound processes and high quality products.

Jan 1, 1995

Aspiring to be excellent makes you a good leader as it shows a capability for strategic thought, defining and implementing a vision, making a job easier, more efficient and effective. Every great business leader can generate additional revenue or cost savings for their company. Becoming excellent requires the desire and action to follow it through. There are many established methods of excellence: benchmarking, target setting, supply chain and market analysis, employee suggestions and knowledge sharing forums. In BHP Billiton, practices benchmarking is a key tool in generating improvements for functional areas such as processing, mine operations and mine planning. Practices Benchmarking involves organisational and technical questions that allow the site to self-assess their maturity and generate a prioritised improvement path. Not only does it benchmark and identify gaps, but the approach also facilitates networking, education and team building. For new leaders it is important to remember that you are not alone. Chances are your problem has been solved before. Networks û internal, external, formal and informal can get you started and often save you time and effort. Any leader can achieve success in excellence through a proper process of problem formulation, data and analysis. Again, using key players can make the process more effective. It is important to remember that the people side of the solution is the key to success and that monitoring will ensure the solution will work. In the words of BHP BillitionÆs CEO, Chip Goodyear: Excellence is a mind set. ItÆs something that comes when people get rewarded forthinking outside the box and applying their skill and knowledge. It happens, not in$50 million chunks, but in hundred thousand and million and $2 million chunks.When you get 35 000 people thinking that way, then youÆve really got somethinggoing.

Jan 1, 2005

Energy is central to respond to critical stakes on human and industrial development requirements as well as on climate change. The increase of the share of carbon-free energy sources in the global supply mix will help to reduce significantly greenhouse gas emissions (GHG) as power generation accounts currently for 41 per cent of these emissions from the energy sector. In this energetic mix, nuclear and renewable energies are complementary, the first more focused in the baseload power generation whilst the second is well suited for decentralised power generation. In this context, AREVA's goal is to enable everyone to have access to a cleaner, safer and more economical energy. Regarding nuclear energy, AREVA's strategy is to capitalise on its integrated operation model, which groups together fuel cycle and nuclear power plant construction, aiming at building one third of the new nuclear capacities and securing the fuel cycle supply chain for its existing and future customers. Therefore, the front end of the uranium fuel cycle, from mining to the fabrication of fuel assemblies, has a key role in the sustainability of the nuclear industry. The replacement of the current capacity and the entrance of new countries on the nuclear power generation might lead to a significant rise of uranium demand by 2020. In order to be prepared in time, AREVA defined an ambitious industrial program to expand mineral reserves, increase the production of uranium concentrates, replace the conversion capacity, build two new uranium enrichment plants, one in France and one in the United States and upgrade its fuel manufacturing plants. To support the front-end industrial activities in the short and long term, AREVA invests on a portfolio of R&D projects to find out solutions to meet customers' needs, to improve its competitiveness and to develop new concepts and solutions to anticipate future market evolutions. In particular, some important technological challenges in mining must be surmounted to develop cost-effective methods to explore and exploit low grade deposits while creating sustainable solutions for reducing reagent, water and energy consumptions. In this lecture, an overview of the industrial investments of AREVA in the front end of the uranium fuel cycle and some highlights on its R&D major axis will be presented. This is an abstract only. No full paper was prepared for this abstract.  

Sep 13, 2010

By M Thomas, M Caccetta, C Laukamp, A Hacket, M Jones, A Rodger, M Verrall, R Hewson

A mineral systems approach was used to interpret precompetitive airborne mineral mapping geoscience data for iron oxide copper gold (IOCG) exploration in the Starra area, Eastern Succession, Mount Isa Inlier. Selected minerals were chosen to map possible source rocks/fluids as well as intersecting structural/fluid pathways that could have transported mineralising fluids into domains of contrasting rocks/fluids where there was potential for physicochemical gradients to precipitate metals. Ferric and ferrous iron contents and white mica abundance were useful mineral criteria to identify theMount Dore Granite of theWilliams-Naraku Batholith as a potential source of æoxidisedÆ fluids rich in Fe, K and potentially Cu-Au. The Mount Dore Shear Zone (MDSZ) intersects the western margin of this granite with the highest contents and changes in composition of the white mica are peripheral to this contact within the granite. This together, with the fact that the entire N-S length of the MDSZ in the study area (~16 km) is abundant in white mica are evidence of K-rich fluids had preferentially moved along this pathway. To the south, the MDSZ intersects a domain comprising massive ironstone bodies as well as numerous graphitic horizons. This interpreted æreducedÆ domain is well mapped using the æopaqueÆ mineral products, as well as by white mica, which is pervasively developed and extends 2 km either side of the MDSZ fault into the meta-sedimentary sequences. The chemistry of this white mica also changes progressively away from the MDSZ, becoming more Si-rich (longer wavelength) towards the contact with massive ironstone bodies in the west and the graphitic units in the east, both of which represent sites of known Cu-Au mineralisation. Beyond these contact zones of interpreted æoxidised fluidsÆ with reduced rocks/fluids, there is either a rapid change to Si-poor white mica and/or no white mica developed, ie major æchemicalÆ gradient change. These mineral mapping results provide evidence for a direct link between possible source rocks and sites of IOCG metal deposition as well as extending the associated alteration zonation which had previously been mapped/published at the metre-scale to the kilometre-scale. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Derham DW, Newcombe LA

The operations of the Mount Morgan gold tailings retreatment plant were significantly improved in 1984 by the desliming of the CIP plant feed, which reduced cyanide consumption and increased percent gold dissolution. Subsequently, the development of slimes treatment, incorporating gold leaching from slimes solids by copper cyanide complexes in the process water, and gold adsorption on to carbon in an environment lacking free cyanide was successfully implemented. Mount Morgan was initially mined for gold commencing in 1882 on the auriferous ironstone cap to the sulphide ore body. During the history of mining and processing at Mount Morgan the operations have developed through numerous phases of gold and copper production, operating almost continuously through until the final closure in late 1990. The final phase of processing was the retreatment of tailings, predominantly flotation tailings accumulated since the 1930s, for the recovery of gold and minor silver. Tailings retreatment commenced in 1982 with the commissioning of a 10 000 tonnes per day CIP plant to treat some 40 million tonnes of tailings at an average grade of 1.08 g/t Au. The initial operations were hampered by high cyanide consumption and poor gold dissolution on the mixed siliceous/pyritic tailings. The successful development and implementation of the desliming of the CIP plant feed in 1984 (as described by Parsons and Hampshire, 1986) reduced cyanide consumption by 40 per cent, and raised gold extraction by 13 per cent points by virtue of significantly higher dissolved oxygen levels. The finer portion of the reclaimed tailings were deslimed by eighty 100 mm diameter AKW cyclones, with the desliming cyclone overflow thickened in a Warman 30 in diameter thickener for water recovery and slimes disposal. Operation of the desliming plant involved the discarding of a slime fraction representing about 15 per cent of the reclaimed feed. Although gold-bearing, the high content of cyanicides and oxygen consumers within the slime negated any conventional treatment of this stream with free cyanide for gold recovery. The natural lixiviant behaviour of the soluble copper cyanide complexes for gold, which was extremely evident at Mount Morgan, directed efforts in this area. Enhancement of gold leaching with a deficiency or near absence of detectable free cyanide, but with significant levels of copper cyanide complex from recycled process water were examined. Adsorption of this solubilised gold onto carbon in a similarly difficult environment required close examination.

Jan 1, 1993

The decision to contract or owner mine should be independent of, and should be made before, definitive estimated cost comparisons could be available. There is substantial potential risk of estimated cost comparisons being flawed due to difficulties in compiling comparable estimates for differing business objectives, errors and omissions or because of significant bias. In the current economic environment, escalating cost pressures potentially lead to increased incidence of disputes in mining contracts. The apparent cost of contractorÆs profit and overheads has tended to become more significant to owners. Economy-driven trends towards higher levels of performance and commercial risk for contractors, and the potential for more adversarial, difficult management; with attendant disputation between contractors and owners, have encouraged development of so-called ærelationship contractsÆ û partnering or project alliance contracts. The paper discusses the issues, circumstances when owner mining or contract mining is favoured and perceived advantages and disadvantages of contract mining. The implications of owner-perceived core business and core skills and outsourcing are also discussed. Techniques of introducing objectivity into the decision to owner or contract mine using matrix analysis or benefit comparisons are described. A disciplined procurement process should deliver a decision to owner or contract mine independent of, and prior to, any definitive comparison of estimated costs. A generic procurement process model is provided as a basis for discussion. Risk is discussed generally and as a significant factor in comparison of estimated operating costs. Consideration of risk and any prudent cost treatment are promoted as necessary pre-requisites to any comparison of estimated costs. The paper develops the concept that the decision to owner or contract mine should be based on real benefits that become obvious in the early stages of the development, particularly the procurement process; and before definitive estimated cost comparison can be available. In the context of this concept estimated cost comparisons tend to be confirmatory. Problems with comparing estimated ownerÆs operating costs with tendered contract prices are also discussed, particularly recovery of capital cost of equipment; and the owner minerÆs trade-off of operating risks for the residual contractorÆs margin attributed to overheads and profit. The paper concludes that sole reliance on a comparison of estimated ownerÆs operating costs with tendered contract prices in deciding to owner or contract mine is questionable and likely driven by a need to satisfy specific in-house customers.

Jan 1, 2003

The purpose of the Lower Lea Valley Cable Tunnel project is to relocate the overhead power lines circuits, which currently cross the proposed site for the 2012 London Olympics in East London. This was the first contract to be awarded as an Olympic project and is on the critical path for the proposed Olympic Park as the construction of the Olympic village, stadium and other venues cannot begin until the tunnels are complete, the cables installed and the overhead power lines removed. The tunnelling works for the scheme include two parallel tunnels between Hackney and West Ham. Each tunnel is approximately 6 km in length. One tunnel is 4.15 m ID and connects the National Grid substations. The other is 2.82 m ID and connects the EDF Energy substations. The tunnels were constructed through mixed ground using four earth pressure balance tunnel boring machines. These were driven simultaneously from two drive shafts within a single site. The 12 km of main tunnels were constructed within a year from start to finish, with completion in June 2007. The shafts range between 6 m and 15 m ID. These were constructed using a combination of caisson sinking and underpinning techniques. Dewatering was adopted to suit the groundwater conditions.Other works include the design and construction of the head house buildings, cable and ventilation culverts, mechanical and electrical (M&E) installations and all associated works. In addition to the above, a further 1 km of tunnel and two shafts were added to the project scope connecting the EDF Energy tunnel to the substation at Bow. These additional works provided further challenges to the project to ensure that these works were constructed within the program constraints for the 2012 London Olympics. This involved refurbishing one of the tunnel boring machines from the main EDF Energy tunnel drives and relaunching the machine to construct the Bow tunnel. The Bow tunnel was constructed within two and a half months, with the tunnel boring machine breaking through in August, ahead of schedule. The main challenge presented by this project is the program constraints. This project outlines the requirement for team work between the client, stakeholders, contractor and designer in order to provide program certainty. A close working relationship between the contractor and the designer is required to provide value engineered, time-saving solutions to mitigate the risks associated with the design and construction program.

Jan 1, 2008