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By Purvis A. H, Greenwood-Smith R, Sowerby B. D

A nuclear technique for the determination of copper and nickel in bulk samples and drill core has been developed at Lucas Heights andfield-tested at Mount Isa. The technique, which is highly specific to the element being measured, utilises the gamma-ray resonance scallering process.A bulk mineral analyser was installed in mid-1976 for the routine assay of copper in bulk samples and drill cores, and remained in operation until late 1981. The operation of the analyser over this five-year period is reviewed with particular emphasis on reliability, accuracy and principal usage.The main application of this analyser was in stope planning and design whereby several thousand drill-core and Wall-chip samples were analysed. It was also used as an aid to underground grade control of stopes where ore dilution by supporting barren backfill was a problem.

Jan 1, 1984

The beneficiation of heavy metal oxides, such as iron ore, is usually performed with heavy medium separation in cyclones, static baths and lately with Larcodems. Atomized ferrosilicon is most suitable as a heavy medium at densities above 3600 kg/m3 whereas a mixture of milled and atomized ferrosilicon is suitable at densities below 3600 kg/m3. When operating a beneficiation plant at densities higher than 3600 kg/m3 the quality of the ferrosilicon particles is an important factor that influences the control of the beneficiation process. Therefore, it is important to know how the rheology would be affected by the ferrosilicon quality as it also influences the control of the process at these elevated densities.

Jan 1, 2002

By D Giles

We present plate tectonic reconstructions, showing that porphyry-type ore deposits are spatially and temporally linked to ridge subduction. A reconstruction of the Peruvian subduction system reveals an immediate metallogenic response to the arrival of the Nazca Ridge at the subduction trench, followed by southward migration of the zone of metallogenic activity due to the lateral migration of the zone of ridge subduction. A similar pattern is recognised in central Chile , where the spatio-temporal distribution of giant ore deposits coincides with the arrival of the Juan Fernandez hotspot chain at the subduction zone. We conclude that there is a spatial and temporal link between ridge subduction and ore deposit formation, with high metal fluxes concentrated in zones of ridge subduction. Thus, the recognition of tectonic patterns associated with ridge subduction can provide insights into predictive mineral discovery by enhancing our ability to predict the position of large mineral deposits in other modern and ancient orogens. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

Mineral resource estimation is commonly based on the accumulation of a series of local estimates. At times, the distribution of these grade estimates is not appropriate to the grade distribution of the data on which the estimates are based. Mineral resource grade estimation has an increased potential of being in error as the grade variability increases. As the mineral commodity value increases, greater grade variability within the mineral resource is tolerated. This paper directs its attention to mineral properties where the data average grade is 20 per cent or more than the data median grade at a specific cut-off grade. A mineral resource estimate is enhanced if it is supported by graphs which demonstrate that the sample data have been separated into appropriate geological domains. Each geological domain has a unique grade distribution signature, which can be graphically demonstrated simply and objectively. This signature will usually be evident well before the Indicated mineral resource estimates are available. The paper looks at the use of the log probability and MedAve plots to assess how effective domaining has been. It further outlines how the MedAve plot can be used to assess the integrity of the mineral resource grade estimate within a geological domain with the data on which it is based. The paper suggests that the overall grade of a mineral resource at any cut-off grade will be closer to the data median grade rather than the data average grade. Tips are provided to ensure that the odds reflected in the data grade distribution are not ignored and hence the risk that the project is affected by unrealistic estimates of the overall mineral resource grade is reduced.

Jan 1, 2003

By C F. Prins, C LantuTjoul

Mineralisation in alluvial diamond or vein gold deposits is often hosted in trapping mechanisms. For instance, diamonds are nested in bedrock depressions such as gullies and potholes which were carved out by the sea long before the diamond deposition took place. Similarly, gold mineralisation can precipitate in the necks of a boudinage structure. In such deposits, the spatial distribution of the mineralisation is governed by the mutual arrangement of the trapsites and by the grade variations within each trapsite. Reliable estimates can be obtained only if they rest on a proper knowledge of both degrees of variability. This creates a challenging sampling problem, as during the exploration phase it is important to have a good global mean estimate to enable decision making towards the future. A similar problem occurs for local estimates at a later stage of development. To understand and manage the sampling for global means, specific sampling procedures are required based on an appropriate choice of sample support size and spacing. Estimates from such sampling campaigns should be unbiased, and the less variability they display, the better the sampling parameters. The performance and impact of sampling parameters are tested and compared on different simulated deposits.

Jan 1, 2005

By Baohm C, Barker T

There have been significant changes in the Australian mineral sands industry in recent years due to changing supply and demand conditions, new product opportunities and opportunities for rationalisation of operations. Earnings within the industry have typically been volatile and this has been reflected in the share prices of listed mineral sands companies. Apart from the effects of variations in the state of the economy on the industry, share prices have also reflected the extent to which a company's earnings volatility is due to capital structure, the relative proportion of fixed costs to total costs and the nature of th'- sales mechanism. At the time of writing, the high prevailing share prices for industry participants and the current outlook for the industry would suggest that the time is opportune for raising equity capital. The immediate outlook for the industry and its various product segments appears favourable but beyond this the usual uncertainties remain. The new tax environment will cause most companies in the industry to have to rethink their dividend and capital structure policies. Most shareholders will now be concerned to maximize dividend receipts and minimise exposure to capital gains tax. Companies in the industry that have relied fairly strongly on earnings retention to help finance growth in the past will- need to look to increased equity raisings in the Future.

Jan 1, 1986

By K Uchino, M Inoue

Self-potential anomalies are generated by fluid pressure gradient, by temperature gradient or by chemical gradient. On the basis of this principle, a new technique is proposed to locate the fire source of spontaneous combustion of coal by the self-potential method. In order to investigate whether this method can be applied to locate the spontaneous combustion of coal in practice, surveys of self-potential distributions were undertaken in a coal waste pile undergoing spontaneous combustion. The results showed that there is a negative centre of the electrical potential distribution in the measurement area. The potential in this centre is about 140 mV lower than that in the surrounding area. Moreover, the negative centre of electrical potential distribution almost overlaps with the high temperature zone. Therefore, it is concluded that it is possible to locate the heat source by the measurement of self-potential distribution.

Jan 1, 2005

There is considerable economic incentive to increase the angle of open pit walls so as to reduce the total volume of waste to be moved to gain access to an orebody. However, a number of slope failures has increased the awareness of mine operators to the potential and consequences of slope failure. Sophisticated methods for the analysis of slope stability have been developed but they rely on an understanding of the appropriate parameters to describe the structural properties of the slope materials. Unfortunately, these properties change with time.The excavation of an open pit mine removes the constraint and weight of the overlying material and allows the newly formed slope to release previously locked in stress. The release of this stress allows the opening of joints and leads to a significant reduction in bulk modulus. The rock mass is also further affected by damage from nearby blasts. Such damage is cumulative and further reduces the modulus of the near surface material and weakens the bonds between structural elements in the slope.

Jan 1, 1992

There was a time, in the memory of some here tonight, when the annual meeting of The Institute was a nostalgic occasion. Often, in the 1920s, there was comment on the decline of Australian mining and on the lack of new mineral discoveries. When some of our Presidents prayed then for a new Bendigo, and instead were given a Mount Isa, they were justifiably disappointed because of the vastly different capital requirements.In 1967 the mining picture is very different. The recent mining developments in Australia are certainly as important as several Bendigos and several Kalgoorlies. The mining industry in Australia has never been more dynamic than today (Table 1). And if we ask why it is so dynamic, the answer lies in the role which overseas capital is playing in the industry. The contribution of overseas capital should concern us not only because we are members of the mining and metallurgical profession, but also because we have a duty to make our profession contribute as much as possible to the well-being of Australians. It is not sufficient to argue that overseas capital is good for the mining industry; we must also examine whether it is good for the economy and the nation. In this context the current criticism of the inflow of overseas capital into Australian mining is useful, for it gives us an opportunity to see what has resulted from the inflow.In discussing this question I do not suggest that we emulate Captain Hancock, that legendary Moonta mine manager who, according to Oswald Pryor's cartoon, used to say to his miners: "When I say a thing is, it is, even if it isn't". The question can only be discussed on a factual basis; and I would submit that many of the important facts relating to overseas capital in our mining industry are often overlooked or ignored. I would further submit, on the basis of these facts, that Australia's present day mining industry has been largely built on overseas capital and that the overall benefits of that capital to Australia have been enormous.

Jan 1, 1967

By Glaessner M. F

The island chains of the Western Pacific (Fig. 1), on account of their related origin, and the similarity of the rocks that compose them, constitute in the main a most homogeneous mineral province. They lie in a complex "mobile" zone of the earth's crust, that formed a geosynclinal area separating the continental margins of Australia and South-Eastern Asia (the so-called Sundaland) from each other, and from the margin of the Pacific Ocean proper (FIg. 2). The whole region was drowned at the close of the Ice Age, as a result of the rise of sea-level that accompanied the melting of the great ice caps in the polar regions, leaving only the higher portions as islands and peninsulas, many of them separated only by shallow seas or "shelves."The geosyncline was infilled with Mesozoic and Tertiary sediments that have undergone varying intensities of folding and metamorphism, and has been subject to intermittent periods of volcanic activity, continuing into the present. Midway between the two continental margins there is a narrow belt of pronounced negative gravity anomalies, with an extraordinary S-shaped convolution in the vicinity of the Banda Sea and Celebes, that marks the core of this unstable region. The folding within the "mobile" zonetrends parallel to it, so that the islands in its vicinity, which are regions elevated by folding, are all elongated in the strike direction of the folds. This explains not only the linear shape of Sumatra and Java, but the arc of islands enclosing the Banda Sea, and the peculiar shape of Celebes.Parallel to the belt of negative anomalies, at a close remove from it, is the line of Recent, or active volcanoes, that extends along the whole length of Sumatra and Java...

Jan 1, 1947

The provision of electrical power is an important consideration in project development. The first step to be taken in this area is to assess the power requirements of the project. The alternatives of laking a supply from a power authority or providing local generation can then be considered. This requires additional defmition of the probable characteristics of the supply.The availability of authority power in Australia is limited by the extent of the state power grids. Recent developments now allow these grids to be extended and their load capacity increased to meet major load increases at less cost than was previously possible.The options for local generation include diesel, gas turbine, steam, hydro, solar and wind, each having its particular performance characteristics and costs. The choice of fuel for diesel, gas turbine, and steam plant likewise involves consideration of a range of factors. The arrangements adopted for five recent Australian remote development projects indicate how some of these aspects influence the decision on power supply.

Jan 1, 1990

Spatial continuity as described by a variogram is a reflection of the underlying mineralisation/geology. Modelling of the spatial continuity (variogram) must account for both the quantitative data (ie sample grades), on which the variogram calculations are based, and the qualitative information as provided by the geological interpretation. An understanding of the geology and the variogram interpretation tie together the sample values and allow us to go beyond the actual data (Journel, 1995). Variography makes geology transportable and allows the geological interpolations to be channelled downstream into mine planning, ultimately affecting the economic decisions surrounding a deposit. As such the process of variography and resource modelling is critical. Thus consistent expert decisions need to be made which force geologists to have a closer look at the available information and the geological interpretations. The aim of this paper is to provide an overview of the latest developments in visualising variography and to demonstrate their usefulness in decisions regarding the spatial continuity of mineralisation. New ideas concerning potential future developments in visualising and modelling spatial continuity through variography are introduced.

Jan 1, 1996

By Wilson AC

Permian coal from Western Australia's only producing coalfield at Collie is the dominant fuel used in generating electricity for the State's interconnected grid. Collie coal is sub-bituminous, non-coking and has a low ash, medium volatiles and high moisture content. The seams were laid down in a fluvial basin which extended beyond the Collie Basin and included the Wilga and Boyup Brook Basins at least. Adjacent parts of the southwest Yilgarn Block are prospective for Collie-type basins. In the past few years significant deposits have been delineated within the Perth Basin, specifically on the Vasse Shelf and in the Hill River area. In the former area high quality steaming coals are correlated with the lowest coal bearing member at Collie. The seams are amenable to underground mining and because of their high quality, the coal may have export potential. Sub-bituminous coal deposits of Jurassic age are present in the Hill River area. Exploration has down-graded the prospectivity of the Carnarvon and Canning Basins for sub-bituminous near-surface coal deposits. Tertiary lignite deposits are present in palaeo-drainage systems in the southern part of the State and their potential for development is being evaluated.

Jan 1, 1986

By L C. Thompson

A new understanding of the formation of black organic shales in the Illinois Basin has contributed to insights on how to produce methane from these complex reservoirs. These shales are far from simple shallow derived sediments but are in fact the result of a complex series of events which include the intermixing of volcanic detritus and the marine organic material, onlap successions and low energy turbiditic intraformational activity. This has led to a review of the commercial significance of the mid Devonian shales in the sedimentary basins of the eastern half of the USA. These shale sequences are also characterised by very little contribution from the underlying Lower Palaeozoic carbonate formations. The later diagenetic influences and the interaction of sea floor bacteria especially since the mid Devonian have lead to the creation of a major source of energy in the form of methane. Vast areas measured in 1000s of square kilometres are known to contain biogenically derived natural gas as methane. However, this vast resource produces very little gas due to abundance of illite which acts as a major adsorption mineral and creates a refractory situation where though there is abundant gas present the rate of release is clearly subeconomic. This paper will present the results of recent laboratory trials which have indicated that it is possible to create microfracturing using bacteria within the gas bearing shale sequence and also restart the methanogenesis process. As most coal bed methane environments have similar organically derived shales in direct relationship to the coal beds themselves then this paper has ramifications for this industry as well.

Jan 1, 2004

A formalised approach to risk management has been regulated in the United Kingdom (UK) since the Construction (Design and Management) Regulations 1994 (CDM) came into force in 1995. These regulations have recently been revised in 2007. In response to a series of significant claims around the world the UK insurance industry published a code of practice for risk management of tunnels in 2003, and that was followed by an international version in 2006. Probably one of the main contributions of this new approach is the recognition that health and safety risks can best be addressed early in the process, initially by the owner and then by the designers. One of the aims is to achieve elimination of risks by good design. The advantage of a risk-based approach to tunnel design is that all risks are considered explicitly, and any residual risks in the design are communicated clearly to the construction team. This paper looks at the implementation of this formalised approach to risk management with reference to the A3 Hindhead Project. The design has been undertaken in accordance with the requirements of the CDM regulations, and also in compliance with the Joint Code of Practice for Risk Management of Tunnel Works in the UK. An outline of the risk-based design process used is provided, including examples.

Jan 1, 2008

Western Deep Levels, a seismically active deep level gold mine, started placing backfill in their narrow tabular workings as part of the regional support strategy in 1986. Over the years the percentage of working places being backfilled has been gradually increasing. At the end of 1995 the support efficiency and the labour productiveness relating to support installation were scrutinised to determine if resources were being optimised. Owing to financial, safety and productivity constraints it was decided to redesign stope support to be less labour intensive, safer and provide an integrated stope support system. This new integrated system will thus combine the previously used temporary, permanent and back area support consisting of mechanical props, hydraulic props and backfill respectively. Backfill previously formed an integral part of the regional support in conjunction with strike stabilising pillars. To design the integrated support system the backfill placement quality has to be exceptionally good and placement must be done as close as possible to the working face. The backfill to face distance was reduced by 30 per cent and in some areas by more than 50 per cent with an increase of square metres filled to increase the effect of the backfill even more. This paper addresses the design and successful implementation of an integrated stope support system based on the optimisation of backfill to the extent where installation of mechanical and hydraulic jacks could be eliminated.

Jan 1, 1998

of the multitude of physiographic problems of immediate interest in volcanic terranes, it is the origin of the magma forming the magnificent volcanoes that is perhaps the most mysterious. Unlike anywhere else on earth, the possible locations of magma production beneath the convergent margins are strongly limited in depth and areal extent. Yet the exact process by which magma is produced still stands elusive, even in light of tremendous gains in analytical and physical insight. The principal aim here is to discuss some of what has been revealed about the physics and chemistry of the origin and evolution of island are magmas.

Jan 1, 1987

This paper describes the programing and specification requirements which affected the choice of excavation methods on the Melbourne Underground Rail Loop (M.U.R.L.). The various methods that were chosen are briefly described, and the three most used are compared in more detail. Excavation rates, cycle times and other statistics are compared for full face tunnel boring, full face drill and blast, and heading and bench using a road header excava- ting machine. The length of tunnel excavated is sufficient to enable meaningful statistics to be presented and the significant specifi- cation and geological factors are described to weight the statistics where necessary for purposes of comparison. Average tender prices are given for excavation and primary support to indicate the reimbursement sought by contractors to carry out this type of tunnelling.

Jan 1, 1981

By M Ewart

The securing of a reliable water supply for a prospective mine in the North West Queensland Mineral Province is usually one of the most influential factors in determining the mine's feasibility. The Ernest Henry Mine required a reliable water supply to serve a demand estimated at feasibility stage to be up to 20 ML/day. Numerous options were considered before a decision was made to construct a 113 km long pipeline from Lake Julius as this was the most cost effective, reliable source of supply. The North West Queensland Water Pipeline is a multi-user, Queensland government funded project initially supplying up to 7000 ML/year of water from Lake Julius to Ernest Henry Mine, with provision made for expansion to serve future users in the region. This paper discusses the history of the pipelineÆs development, together with a summary of the scheme's design features. Environmental and licensing requirements, construction and operational issues are also discussed.

Jan 1, 1998

The Bureau of Mines, with a history of mining research since 1910, still seeks improvement in safety and health along with improvement and competitiveness in the mining industry. Much promise of such improvements lies in new technology, and this is particularly the case in the still growing coal mine sector, although much Bureau research is long term, high risk, aimed at new concepts.The miner's environment is a primary concern, involving technologies of contaminant monitoring and control in high production scenarios. Contaminants arising from diesel use, alternatives to high speed rotary cutting and more efficient dust removal are being addressed, and drilling efficiencies, better monitoring through unitising operations and insitu rock dust monitoring are particular features.

Jan 1, 1991