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The Youga gold mine in Burkina Faso, West Africa, is scheduled to produce first gold in the third quarter of calendar 2007. The project is expected to produce 540 000 oz of gold over 6.5 years, from a conventional open pit carbon in leach mine. The direct capital cost of the project is US$47 M. Etruscan Resources Inc, a Canadian based gold exploration and development company, holds 90 per cent of the project company Burkina Mining Company SA (BMC). The state of Burkina Faso is free-carried for the remaining ten per cent of BMC. RMB Resources Limited, of Melbourne Australia, has arranged a US$35 M project finance facility for BMC (the Borrower) as the majority of funding for the Youga project development. The loan facility was provided by RMB Australia Holdings and Macquarie Bank Ltd (the Lenders) each as to 50 per cent in the lending syndicate. The Lenders also provided a gold hedging facility to guarantee a minimum price for the projectÆs gold production. Burkina Faso is a francophone country, part of the Economic and Monetary Union of West Africa (UEMOA). The project financing is the first such facility to be arranged for a mining project in Burkina Faso, with little or no precedent available in other UEMOA countries. Therefore, while the Youga gold project is forecast to be a robust project applying conventional mining and processing methods, a number of legal, technical, commercial and social issues required identification, evaluation and resolution before the loan could be established. This paper describes that evaluation process and the resolution of these issues. In-house experience and expertise in both the LendersÆ and BorrowerÆs teams has facilitated a greater understanding and æownershipÆ of the issues and hence provided comfort with risks which might not normally be taken in conventional project developments and project financings. As a result, blanket external reviews were not required by the Lenders. A long-standing relationship between Etruscan and RMB Resources also facilitated solutions to a number of issues. Nevertheless, a degree of flexibility by the Lenders, the Borrower and Etruscan was required to successfully close the financing.

Jan 1, 2007

By D Nourry

Optimising the blast is a major issue in the blasting business. It generally means acting on the blasting pattern (drilling, charging, detonating) in order to get a given æresultÆ. This result may either be related to economic reasons, such as the fragmentation influencing productivity, or technical reasons, for example vibrations and projections. Within the frame of the EEC funded Brite-Euram project entitled æBlast-ControlÆ, involving academic research and applied expertise, a general methodology was developed to approach such a problem and currently applied to the industrial partners of the project and final end-users of the generated results. These partners are the limestone ALZO quarry of the CALCINOR group in the north of Spain and the dolomite DMD (Dolomies-de-Marche-les-Dames) quarry of the LHOIST group in the east of Belgium. A first part of the project, over 18 months, was dedicated to establishing a clear relationship between productivity of operations from drilling to primary crushing and the fragmentation resulting from the blast. Extensive monitoring of blasting, production performance and fragmentation data was carried out and automatically collected into a database on both quarries. As expected, it appeared that excessive amounts of fines or boulders were substantially reducing productivity and thus profitability of the operation. Furthermore, an æoptimalÆ fragmentation was assessed for the quarries to run at the best (high throughput, low cost). The second and last part, for the remaining 18 months, was then dedicated to adapting the blasting practice in order to orientate the fragmentation towards a æbetterÆ one. A very common problem normally addressed by any consultant. Nevertheless, the target was not limited to solving the problem for these two quarries, but also to develop a generic method to address this blasting adaptation process and to implement it into a computerised tool. At this stage, it is then obvious that portability of the method and the system are major qualities to be looked for. This paper is aimed to present how this method was developed, how the system was implemented and how it was finally used.

Jan 1, 2001

By B Cronin, M Gao, M F. Young

Fine grinding technology has become extremely important for Mount Isa Mines Limited in the last decade for flowsheet development for the McArthur River deposit and in rejuvenating the Lead-Zinc Concentrator at Mount Isa. Regrinding products with 80 per cent passing seven microns and 12 microns were required, respectively, for the McArthur River ore and the Lead-Zinc Concentrator at Mount Isa. Development of the ISAMILL, a horizontal stirred mill with a gross mill volume of 4000 litres (a net volume of 3000 litres), has been successful in delivering the required grinding product sizes with an energy consumption acceptable to a mining operation. The ISAMILL performance for processing both lead and zinc streams at Mount Isa is discussed in this paper, including the milling energy efficiency, the media wear and the size-by-size recovery data for one flotation process following the fine regrinding stage. The potential use of the ISAMILL technology at various phases of the mining cycle is also discussed.

Jan 1, 1998

By Misra A

The development of roadways in underground mines in Autralia is by conventional continuous miner technology. The rate of development achieved using this technology is improved by modifications to this technology using additional equipment such as surge cars or decreasing roof bolting time.Development rates achieved with this technology compare with developing technologies such as high capacity continuous miners, continuous transportation and simultaneous cutting and bolting systems such as the Kemcol Beaver. Pillar dimensions have an effect on the rate of development.'

Jan 1, 1991

ABSTRACT' Mainland Papua New Guinea is formed of a microcontinental / island arc system (?Eocene - latest Oligocene Sepic arc) which in Middle to Late Miocene times was obducted over the northward- moving Australian plate. The sedimentary and volcanic units of this system form part of the Wogamush Group (Aure beds, Mena beds, Omaura Formation, Movi beds, Wogamush beds, Wogamush Formation. Nansananka Conglomerate and other correlates in- eluding cale-alkaline volcanics and carbonate beds). This Sepic event was followed in Pliocene-Present times by the obduction of the Finisterre-Adelbert-Oenake fore-arc or possibly oceanic plateau. Obduction of the Sepic arc produced crustal thickening

Jan 1, 1997

By Brasnett TC

A wide variety of problems are encountered on a day to day operating basis in the Isa Mine Concentrators. These vary from complex textural problems in the lead-zinc concentrator and their subsequent effect on grinding and flotation to scheduling of converter slag treatment in a chalcopyrite concentrator. With the advent of process control, metallurgists need to specialise and keep up to date with technology improvements. This paper will attempt to describe the significant problems'faced by a Metallurgist û Control.

Jan 1, 1978

By Gemuts I, Hudson D. R

Massive sulphide mineralisation at the Miriam prospect, near Coolgardie, Western Australia, is fracture-controlled and associated with disseminated sulphides near the basal contact of an ultramafic lens. The lens is peridotitic in composition with a pyroxenitic zone at its base, and lies within a sequence of altered high-Mg basalts and pillowed tholeiitic basalts. Recrystallisation of the ultramafic rock has resulted in the development of secondary olivine. The average composition of the sulphide fraction of massive ore is Cu = 4.4%, Co = 0.3%, Ni = 23.0%, Fe = 31.8%, S = 40.6%, consisting of the supergene assemblage violarite-pyrite to a depth of 210 m.

Jan 1, 1973

By J Rapkoch, M Cerna

As long as the tendency of Chilean copper ores continues to feature high levels of impurities, the smelters will tend to produce high-impurity mattes. The most notable impurities include As, Sb, Pb and Zn. Producing high-quality copper with such materials is a major challenge to metallurgical engineers and operators. More investigations into process optimisations and/or alternatives are needed, using both theoretical knowledge and operational skill. Converting of matte in Chile depends on the matte grade using established technologies. Mattes up to 66 per cent Cu, such as those from Outokumpu Flash furnaces, are converted in two stages, while typical Teniente Converter mattes, ranging from 70 - 74 per cent Cu are converted in one blow, directly to copper. In this paper thermodynamic data are used to evaluate possible variations in the use of traditional technologies applied to smelt copper concentrates with high impurity levels. The results of this analysis help to predict the impurity distributions between matte-slag-gas during the slag blow, and between copper-slag-gas during the copper blow. For converting high-impurity white metal, the effectiveness of volatilisation in the slag blow is analysed. In the copper blow, the type and the amount of flux (SiO2, CaO and others) are altered with the aim of optimising impurity distribution to the slag and gas.

Jan 1, 2005

Interpreted geologic domains provide the geologic architecture of many current models used to estimate the potential economic resources in mineral deposits. The spatial extent of each domain is usually defined by a three-dimensional wireframe or triangulated surface.The set of geologic wireframes forming part of a resource model might generally be called a spatial interpretation of some set of geologic features coincident with the mineralisation, based primarily on logged and mapped properties of the samples and other exposures of the mineralisation. The interpreted spatial distribution of rock type, alteration and grade of drill hole samples above a particular grade threshold are commonly used criteria in constructing the geologic domain wireframes. Frequently, the grade threshold is closely related to the anticipated economic cut-off grade. The boundaries or spatial limits of different domains are most commonly defined as æhardÆ or æsoftÆ. A æhardÆ boundary usually means no dependent relationship of any kind is defined between the properties of samples inside a particular domain wireframe and those samples outside the wireframe. A æsoftÆ boundary commonly implies that some kind of dependent relationship does prevail between the properties of samples inside and outside the particular wireframe. Many ways are used to describe those relationships, few of which are based on spatial analysis of the continuity of sample attributes across the domain boundaries. In local estimation procedures such as ordinary block kriging, æhardÆ boundaries act as a total barrier to the influence of samples on either side of the boundary depending on the location of the block being estimated. In some instances, æsemi-permeableÆ boundaries are used in which the samples inside a domain wireframe are allowed to influence the estimates outside but not the reverse. This can lead to many undesirable effects in estimates of block grades.This paper discusses the value of this approach to geologic domaining from a viewpoint of model complexity, as well as in relation to the implications for both linear and non-linear estimation methods and contrasts it with alternatives. It also explores some important consequences of using æhardÆ and æsoftÆ geological boundaries with the commonly used modelling methods: excessive smoothing of estimates near domain boundaries and conditionally biased estimates of grade at the global and local scale.

Sep 26, 2011

By Young D. R, Webb I. D

The hydro-chlorination of Fe2O3 and Fe304 has been investigated in the range 850-950¦C in order to elucidate the role of iron in the segregation process for nickeliferous laterites. The kinetics of Fe203 chlorination using 20% HC1 - 80% N2 gas mixtures is consistent with a single-stage structure control model, whereas Fe3O 4 exhibits a two-stage reaction mechanism. Oxygen potential measurements using a CSZ probe located above the bed and X-ray powder diffraction results confirm the proposed reaction scheme. When a serpentine nickeliferous laterite (1.03% Ni - 11.7% Fe) was chlorinated at 900¦C with a 20% HCl - 80% N2 gas mixture it was found that the iron oxide in the ore was extracted in a similar manner to the synthetic iron oxides. Also, it was found that the nickel extraction from the ore paralleled that of the iron and the tests indicated that for the major part of the extraction, the solid nickel species were in equilibrium with the gas phase. The recovery of nickel from laterite ores by the segregation process has been investigated by a number of workers and several extensive reviews of the literature associated with this field have been published (Iwasaki, 1972; Canterford, 1975; Wright, 1973).

Jan 1, 1987

This paper describes preliminary research on the application of Markov Decision Processes (MDP) to Real Option Valuation (ROV) and the optimisation of mine scheduling. The MDP framework is a novel approach to option valuation and scheduling in mining operations. A learning agent is introduced into the valuation process of an open pit, where prices and block ore grades have probabilistic values. The prices are modelled using a mean reverting diffusion process and the block grades using sequential Gaussian simulation. The agent is asked to learn which production parameters should be used in order to maximise the overall value of the project. The introduction of the agent permits a real option approach to mine valuation, such that the value associated with the robustness of a design to uncertainty can be measured. A simulated example is used in which there are ten blocks to be extracted under conditions of grade and price uncertainty. Using policy iteration, an optimal policy is generated and the value of production options is found. The potential financial gains from applying MDPs to mine valuation and optimisation are substantial and warrant further investigation.

Jan 1, 2007

By Phillips H. R

The action of free rolling disc cutters is well understood, relationships between disc geometry and performance having been established both in the laboratory and under field conditions. However, under severe operational conditions a malfunction of the disc bearing assembly is likely to produce a definite change of cutting action. Collapsed or siezed bearings can even prevent the disc from rolling and thereby create what is equivalent to a drag pick. This paper describes a programme of laboratory experiments using deliberately stalled discs. Their performance under such conditions is contrasted with that for a free rolling disc and also with a drag pick having a ridged front developing into a negative radiused back clearance angle. In conclusion an assessment is made of the influence stalled discs can have on the torque and thrust requirements for a tunnel boring machine.

Jan 1, 1981

By M Pizey, P Lindsay

Coal mining has been occurring on the Stockton Plateau for over 100 years. As a result of both natural conditions and mining activities, surface water on the plateau is known to have low pH and elevated metals concentrations, a condition known as acid rock drainage (ARD). Solid Energy New Zealand Ltd (SENZ), as owners of the current mining operations at Stockton desire to understand the nature and causes of ARD at Stockton to determine whether commercially viable options can be developed to improve the water quality to levels acceptable to the local community and regulators. A series of integrated water quality investigations have been performed towards developing a characterisation of the water quality on the Stockton Plateau and receiving waters. The investigations performed include: design and implementation of a water quality monitoring program to collect a satisfactory base of water quality data from which to develop an understanding of the water quality and its variability, and to collect data regarding the range of flow rates that occur in the principal streams; development of a hydrological model for the Plateau with the ability to predict flow rates at key locations on the plateau and on the Ngakawau River; field investigations of the bio-diversity of the plateau and surrounding areas, to develop a snapshot of the health of aquatic communities and whether streams draining mine workings are æadversely impactedÆ; eco-toxicology; waste dump seepage water quality monitoring at selected basal springs, drilling, investigations and permeability and geochemical testing; data processing of a range of historical data and the newly acquired data for the development of empirical relationships that describe the water chemistry system and its relationship in turn to flow rates in the streams; simulation of the long term water quality record for the measured parameters (pH, acidity and metals concentrations), based on the hydrological model and the empirical relationships developed from the new database; and preliminary development and examination of mitigation options for the ARD issues at the mine. The study has progressed towards design of pilot studies of options for mitigation of the generation of the ARD as well as treatment of the discharges. It is the integrated approach adopted by SENZ from an early time in the investigations, that has enabled fast-tracking of the pilot engineering trials. This paper presents the results of the field investigations and eco-toxicology studies and demonstrates the value of predictive modelling of water quality in the study area, even at a very early stage in the remedial engineering design process.

Jan 1, 2003

By Seedsman RW, Duncan Fama ME

Mine design procedures will be revolu- tionised by technological developments in computers, software, database construction and management, and numerical modelling programs. Developments in geotechnical databases will be required which utilize geological and geomechanical tests to supply appropriate input for numerical models. Techniques utilizing sedimentological and structural modelling are described. The capacity of current numerical models in mine design is outlined and a program for developing a fully integrated mine design package proposed.

Jan 1, 1987

By Ogilvie M

South Bulli is the oldest and largest underground coal mine in Australia. Two longwall units are in operation and current production is 2.5 to 3 million tonnes of run of mine product per year with a workforce of 600. Prior to 1984 a workforce of around 1,200 produced 1.5 million tonnes. Advances in technology can. of course, account for some of this gain, but the changes made in the human resources area are also seen as playing a major role in South Bulli emerging as a reasonably stable operation.The human resources strategy adopted recognises the value of the workforce and is aimed at not only fostering cooperation as all levels, but also making employees aware of the direct contribution they can make to the success of the enterprise.

Jan 1, 1991

By C F. Nichol, L Smith, R D. Beckie

A better understanding of the hydrogeology within mine waste rock and cover systems is essential for the quantification, prediction and prevention of metals loading to the environment surrounding waste rock piles. The effect of surface condition on the internal flow mechanisms within an intermediate-scale constructed waste rock pile is being investigated at the Cluff Lake Mine, Saskatchewan. Changes in the water balance, the outflow distribution and water residence time have been observed in the waste rock pile following successive modifications of the surface condition. The three year old, run of mine, free-dumped surface was ripped to a depth of 30 cm to 40 cm, and levelled in October of 2001. In August 2002, a 10 cm to 15 cm cover of compacted waste rock was placed on the pile. Outflow, precipitation and run-off data collected during natural and artificial rainfall events have been used to quantify the maximum infiltration rate, and the spatial pattern of discharge and cumulative volume of water that infiltrated into the waste rock under each surface condition. Infiltration data together with the outflow data provide a basis to address the residence time of water within waste rock and the dominant flow mechanisms for different surface conditions. With a free dump surface spatially distinct wetting fronts are observed at the base of the pile that vary in flow rate by an order of magnitude (measured at a 2 m by 2 m scale) and in time by up to a week. Following ripping and levelling, similar cumulative outflows were observed, but the magnitude and arrival time of wetting fronts changed across the pile. A decrease in outflow volume, a decrease in infiltration volume, a two-fold increase in the response time of wetting fronts and a more spatially uniform distribution was observed following placement of the compacted surface layer. Based on preliminary data, the internal structure appears to be the dominant factor controlling outflow variability.

Jan 1, 2003

Renison Goldfields Consolidated Limited (RGC) and Consolidated Gold Fields Plc (CGF) purchased New Guinea Goldfields Limited (NGG) in 1982 as an exploration venture. Following an intensive drilling programme in the Upper Ridges area sufficient ore reserves were outlined to justify the installation of a new 700 tonnes of ore per day gravity gold extraction plant. Major considerations in the design of the new plant were to minimise production inter- ruptions in the existing plant and to include simple, but technically efficient, equipment that could be operated and maintained by a workforce with limited experience in modern technology. These goals were achieved over a six month period, commissioning being carried out in April, 1983. Mining the epithermal gold deposit is by open cut benching and truck haulage. The gravity concentrator includes a scrubber, wet hammer mill and rod mill, to crush, grind and prepare the ore for sizing and desliming. Gold recovery units consist of a jig, spirals, shaking tables and amalgam barrels. Although the majority of the gold is in the minus 100 plus 20 microns size fraction a recovery of 63 percent, from a head grade of 2.0g/tonne, is Achieved.

Jan 1, 1984

By Wright J

Large scale cut and fill mining in narrow silver-lead-zinc orebodies began at Mount Isa in 1964. Initially each orebody was one stope and access was via raises from the level above. Upholing was the principal mining method, although flatbacking was employed where ground conditions were more difficult. Developments since have included access via footwall inclines and connection of all stopes with major crosscuts. Flatbacking is the principal method. The most recent cut and fill operation is now fully mechanised using drilling jumbos, rockbolting jumbos and load-haul-dump units. Improved ground support and drilling and blasting practices have enhanced safety, recovery and productivity in all cut and fill operations.

Jan 1, 1988

By Duke J. H

Advanced computer aided geological modelling techniques are now available to the geologist to allow the rapid evaluation of a gold orebody at various stages of its development. The types of grade estimation techniques used change during the various stages as the density of drilling and knowledge of the deposit increases. At the prospect evaluation stage drillhole intercept selection techniques are coupled with preliminary 2D (vein or layer) modelling or 3D block modelling techniques to arrive at a geological resource estimate. At the prefeasibility and feasibility stages more sophisticated 2D and 3D modelling techniques, such as domain controlled grade interpolation with anisotropy, are used along with interactive open pit and underground mine design, to calculate recoverable reserves. At the production stage closely spaced blasthole sample data is modelled quickly and coupled with interactive grade control facilities. Shot volumes, tonnages and grade estimates can be databased to provide reconciliation figures. These modelling techniques are embodied in MINEX-3D, an Australian software system which, with the emergence of the 386-based PC and high resolution (VGA or better) graphics, makes a whole range of advanced geological modelling techniques available to most exploration and mine geologists.

Jan 1, 1989

Authorisation No.66 (to Prospect) was allocated to R.W. Miller & Co. Pty. Ltd. on 1st November, 1976. Exploration has brought coal reserves to measured status in the Jerry's Plains sub-group which are about 550m. thick. The immediately lower Vane Sub-group, about 200m. thick, includes about 20 seams. The total measured and indicated reserves of the two sub-groups based on the criteria adopted by the company amount to 1362 million tonnes in situ. This very large resource is subject to very many mining constraints both physical and economic which limit the saleable reserves under present conditions to about 120 million tonnes. The results of the calculation of reserves after exploration is complete in a deep multiple seam situation is dependent upon the criteria used to include or exclude seams in the reserves. These criteria are state- ments of the miner's expectations of the market, mining and coal preparation technology, local and national politics and the law as it may be applied in the future.

Jan 1, 1979