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By S G. Hagemann, M E. Barley

The Mt Tom Price deposit is a world-class high-grade hematite deposit in the Hamersley Province of Western Australia with an original resource of 900 Mt of almost pure hematite, averaging 63.9 wt per cent Fe. Petrological and geochemical studies at both the Southern Ridge and the North deposit at Mt Tom Price have identified three hypogene alteration zones between unmineralised BIF and high-grade iron ore: distal magnetite-siderite-stilpnomelane; intermediate hematite-magnetite-ankerite-talc-chlorite; and proximal martite-microplaty hematite-magnetite-apatite alteration zones.Fluid inclusions trapped in siderite within the distal magnetite-siderite- stilpnomelane alteration zone at the North deposit revealed primary high salinity (25.5 eq wt per cent NaCl-CaCl2) inclusions that homogenised between 107¦ and 142¦C into liquid. Fluid inclusions trapped in ankerite within ankerite-microplaty hematite veins in the intermediate hematite-ankerite-magnetite-talc-chlorite alteration zone at the North deposit revealed mostly H2O-CaCl2 pseudosecondary and secondary inclusions with salinities of 22.4 - 25.4 eq wt per cent and 22.9 - 25.9 eq wt per cent CaCl2, respectively. Pseudosecondary inclusions homogenised between 153¦ and 449¦C and secondary inclusions homogenised between 103¦ and 157¦C. Fluid inclusions trapped in apatite within talc-microplaty hematite veins in the intermediate hematite-magnetite-talc-chlorite-apatite alteration zone at Southern Ridge revealed that primary, medium salinity (7.0 - 9.0 eq wt per cent NaCl) inclusions homogenised between 181¦ and 257¦C and primary high salinity (22.8 - 25.9 eq wt per cent CaCl2) fluid inclusions homogenised between 118¦ and 257¦C into liquid. Microthermometric analysis of quartz from quartz-hematite veins from the Southern Batter Fault, Southern Ridge show a complex fluid inclusion history. Primary fluid inclusions consist of: low- and high-salinity H2O-NaCI inclusions trapped at temperatures of approximately 140¦ to 230¦C; vapour-rich inclusions of unknown compositions; and æcomplexÆ salt-rich (Ca, Mg, K and Na inclusions).Secondary inclusions consist of medium-salinity fluid inclusions trapped at temperatures of about 140¦ to 280¦C.A two-stage hydrothermal model is proposed for the formation of both the Southern Ridge and North deposits. Early 1a hypogene alteration involved the release of hydrothermal NaCl-CaCl2-rich (25.5 eq wt per cent) basinal brines (110¦ - 150¦C) from the underlying Wittenoom Formation and directed upward along normal faults and focused within the silica-rich rocks of the Dales Gorge Member, by the shales of the underlying Mt McRae Shale Member and overlying Whaleback Formation. Within the Dales Gorge Member hydrothermal basinal brines migrated laterally within large-scale folds with permeability controlled by shale bands and the NW trending dolerite dyke sets. Fluid rock reactions transformed unmineralised BIF to magnetite-siderite-iron silicate BIF, with subsequent desilification of the chert bands. Stage 1b hypogene involved an increase in temperature of the hydrothermal, CaCl2-rich saline (24 eq wt per cent) basinal brines (250¦ - 300¦C) resulting in formation of hematite-ankerite-magnetite-talc-chlorite alteration and the crystallisation of microplaty hematite. Late stage 1c hypogene alteration involved the interaction of low-temperature (~120¦C) basinal brines with the hematite-ankerite-magnetite mineral assemblage. At the Southern Ridge deposit this process was very intense (ie high fluid flux), therefore resulting in the almost total removal of ankerite and resulting in the increased porosity of the ore. Stage 2 supergene enrichment in the Tertiary resulted in the removal of residual ankerite and apatite and the weathering of the shale bands to clay.

Jan 1, 2005

By P M. Ashley, M T. Costelloe

The Mary Kathleen tailings storage facility (TSF) contains 7.1 Mt of uranium mill tailings. This waste repository was rehabilitated in the mid-1980s using a multibarrier dry cover. At the time of mine closure, it was predicted that acid mine drainage (AMD) generation would not eventuate and that uranium, heavy metals and radionuclides would be adsorbed within the tailings and not seep from the TSF into the environment. This study reports on the environmental status of the TSF. Gamma-ray measurements indicate an intact dry cover of the waste repository. However, seepage (~0.5 L s-1) of acid (pH 5.71), saline (0.31 per cent), high conductivity (8.8 mS cm-1), slightly oxygenated (DO 2.6 mg L-1), radioactive waters occurs from the toe of the tailings dam into the former evaporation ponds and local drainage system. Seepage waters are calcium-magnesium-sulfate rich with elevated Fe, Mn, Ni, U and Zn values. Oxygenation of tailings seepages causes the precipitation of Fe and coprecipitation and adsorption of other metals (Pb, U, Y), metalloids (As), rare earth elements (Ce, La) and radionuclides (U-235, U-238, Th-227). In contrast, Ba, Ni, Sr, Mn, P, S, Ca, Mg, Na and K as well as Ra nuclides (Ra-226 and Ra-228) remain in solution until pH neutralisation and evaporation lead to their precipitation in efflorescences and sulfate-rich evaporative sediments further downstream. Dry capping of Mary Kathleen uranium mill tailings has resulted in physical containment of the wastes. The dry cover shows no signs of erosion and radiation levels are within acceptable limits. However, the flow rate of surface seepage from the TSF occurs at a much higher rate than predicted. Also, the neutralising potential and adsorption capacity of the tailings and underlying aquifer were overestimated at the time of mine closure. AMD has developed mobilising metals, metalloids, rare earth elements, alkalis, radionuclides and sulfate from the waste repository into surface water seepages.

Jan 1, 2003

Mine pit slopes in the Pacific Rim are a geotechnical challenge because of the complex geology in which they are developed. Mines are currently being fast-tracked to meet the increase in commodity prices, often resulting in some reduction in ground studies and short-cutting of design procedures. In addition, the resources boom means that skilled personnel are in relatively short supply. At a time when mine pits are getting bigger and deeper, and the engineering is getting more demanding, there is an increased demand on managers to effectively implement the work.   Experience both in New Zealand and the Philippines, display the complex range of geological environments in which pits are being excavated. Working in these conditions has shown that successful geotechnical design requires a strong geotechnical model based on sound geology. An appropriate level of investigation and analyses results in a certain level of understanding for the mine design. There is a point where additional expenditure (on investigation and analyses) is not warranted based on the expected minimal impact on decreasing the level of perceived risk on the project. For most projects in our experience the analytical methods and complexity of geotechnical assessment changes increases as the level of knowledge grows.

Jan 1, 2006

I have headed this paper with a question and for the impatient among you ûthe answer is no we have not run out of developments but, and it is a big æbutÆ, we need to be innovative and ahead of the game or ænoÆ will be æyesÆ before we know it.Why do I believe that our future lies in innovation? Thirty years ago, knowledge doubled every 14 years. It is now doubling every seven years. In 1965, Gordon Moore, one of the founders of the chip maker Intel, made an observation that growth in memory chip performance is doubled every 18 months which became known as MooreÆs Law. Now there is fibre law, where the transmission line capacity doubles every nine months and storage capacity, under disc law, doubles every 12 months. What does this mean? Well, firstly there is a massive rise in information flow and availability with no limits in growth for at least the next ten years. Secondly, unlike our grandfathers, we are most unlikely to be employed by the same firm for our working career - we may not even have the choice to stay with the same company. In a phenomenon Richard Foster and Sarah Kaplan (2001), borrowing from Schumpeter, termed æcreative destructionÆ, companies are unable to sustain market-beating levels of performance for more than ten to 15 years. In the 1920s the turnover rate of companies in the United States was 1.5 per cent, so a company could employ almost three generations from the one family. A company had a half life of 60 years. In other words, you could well be in the same working environment as your grandparents. Today the churn rate is estimated to be eight to ten per cent. A company has a half life of five to six years. So for large companies, as an employer or employee or as a contractor, your working environment has a 50 per cent chance of changing in five years. Innovation is the driver of this rapid rate of change. Innovation is not for the faint hearted (Cutler, 2001) but it is the core for success in the global economy. The rate of change in our world is not going to decrease. We must learn, not only to manage change, but to enjoy the process of changing û to ride the tsunami of the knowledge economy.

Jan 1, 2002

By P Davidson

For many years, in numerous settings, the need for a language-fair and culture-fair assessment test has been identified as a significant issue for employment and selection for training of remote indigenous community members. Pivotal to the successful implementation and application of such a test is for it to gain the acceptance and trust of the local indigenous communities as a fair assessment and for it to provide organisations with an accurate predictive tool. However, when western tests have been used with indigenous groups, inherent language and cultural bias have had a significant negative impact in terms of community acceptance. These have also affected the accuracy of performance predictability. The Queensland Test was developed to overcome these problems. Originally developed for use in Papua New Guinea, it reduced training failures by 20 per cent. Later refinements were made and it was used with Aboriginal Australians. Since 2002, assessment tests have been used by the Freeport mine in West Papua to support their recruitment, selection and training processes for the local indigenous community, the Seven Suku Tribes. The initial process included the application of standard æwesternÆ assessment tests, which did not provide valid selection predictions, with community members and elders describing these tests as unfair and the organisation being concerned that the results were not accurate. A trial of the Queensland Test was conducted and a high correlation was established between the performance of FreeportÆs current Seven Suku employees as assessed by their managers and their Queensland Test results. Based on the results of this pilot the Queensland Test was successfully implemented as the primary selection tool for potential employees from these local indigenous groups. The testing materials and method gained community trust and support, with tribal elders describing the Queensland Test as a fair and suitable selection tool for their community members. Such results have sparked an interest within the Australian Mining industry, with similar results being reported from a recent trial. The Queensland Test has been implemented at a major site in Queensland and is being investigated for use elsewhere.

Jan 1, 2006

By Fradd WP

South Australia pioneered metal mining in Australia and was the main source of copper for several decades. Gold discoveries and mining also contributed significantly to the development of the Colony. Across the State can be seen the holes, the mullock heaps and, in some instances, the remnants of machinery of the past era. In this, the centenary year of the discovery of the Teetulpa goldfield, considered by some to he the most significant discovery of gold in the State, it is appropriate that we should present a paper on the history of gold mining in South Australia. South Australia has not been a major producer of gold with recorded production a little in excess of 15 million grams (15 t). This represents about 0.25 per cent of the Australian total and ranks last of the States of the Commonwealth. The outstand- ing feature of gold production in South Australia has been the succession of short periods of rela- tively high production immediately following a discovery, with payable dirt being quickly exhausted, a fact clearly illustrated by the graph of South Australian gold production (Figure 1).

Jan 1, 1987

Hydraulic mining shovels can be successively used at open-pit mining operation in severe climatic zone with air temperature interval from -700C to +450C typical for some northern region of the world particularly of Russia, Canada and Sweden, if they would be equipped by special preheating facilities for their diesel engine, water, hydraulic oil and lubrication systems. All shovels manufactured by the Komatsu Mining Germany GmbH for operation at ambient air temperatures down to -50¦C have cast and forged structural design elements, bolted connections made of special steel grades, electric cables with special insulation, flexible high-pressure hoses manufactured by ICE-Champion with connectors made of special steel grades.Generally at the temperatures below -25¦C the ordinary machine has to be stopped, the attachment should be placed in the parking position, the generator should be switched on, or the external electrical power supply connected, for the preheating equipment. For rapid start-up in winter after a long shutdown of a hydraulic shovel, there is a procedure for preheating of the main systems. It is applied for the following systems: engine cooling system, engine oil, hydraulic oil, pumps and drive motors of the propel gears, electric cabinets, machinery house, especially near the ventilation inlets and outlets.Start-up of the main drive engine is permitted at a hydraulic oil temperature of -20¦C, when it has a viscosity of 1000 cSt. In this case the rotation speed of the diesel engine crankshaft is lower by two times than the nominal value and this is the most favourable condition of start-up of the engine and hydraulic pumps and motors, which work with half of their rated rotation speed until the hydraulic oil reaches a viscosity from 100 to 10 cSt. After that the hydraulic system and the entire shovel begin to operate under normal conditions.

Dec 6, 2010

By J Fraser, M Scoble

Within the past decade, incidents of mining–community conflicts have grown dramatically and represent one aspect of a phenomenon known as social risk. Research published in 2014 indicates that a lack of social acceptance is now a leading and costly cause of delays for mining projects.The rise of social risk, complemented by the need to earn the trust of an increasing number of stakeholders so that mining projects can be developed effectively, is problematic for the industry. Conflicts are occurring in situations where companies are fully compliant with regulatory and legal requirements, despite initiatives by mining companies to earn social acceptance and despite the proliferation of tools to support corporate social responsibility. Intensifying the impact of social risk is the fact that it has increased during a time in the global mining sector when companies have had to grapple with declining commodity prices, increasing capital costs and debt levels and the challenges of mining lower-grade deposits.This paper will explore a hypothesis that in today’s interconnected society, social risk in the mining sector constitutes a legitimate business risk that must be managed strategically. The reality facing mining companies is that information, once considered confidential, now travels quickly on social networks and via a growing number of groups and individuals that have earned a legitimate right to be classified as stakeholders in projects that affect their communities. To be successful, it is suggested that companies will benefit from increasing internal collaboration and providing training to equip teams to mitigate social risk to mining projects and protect reputation capital. The paper is based upon PhD research being undertaken to assess the points of intersection between social risk and social responsibility during the construction stage of greenfield mining projects.CITATION:Fraser, J and Scoble, M, 2015. Mining–community conflicts – can the future mining sector transform social responsibility?, in Proceedings Third International Future Mining Conference, pp 159–168 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

The first record of coal discovery in Australia dates back to 1791 when escaping convicts found coal in the banks of a creek just south of Newcastle. Development in the Newcastle Coalfield was the sole source of supply for the colony and for export until the 1850s when mines were established in the Southern & Western Coalfields. The important Hunter Coalfield was not discovered until 1873 when coal was found at Rixs Creek near Singleton: The first exploration drillholes were commenced in 1799 using drilling equipment obtained by Sir Joseph Banks. From 1820 to 1850 several famous geologists (naturalists), including the Rev W. B. Clarke, J. D. Dana and Strzelecki, wrote reports on the coal measures in New South Wales. The first Government Geo- logist, Samuel Stutchbury, was appointed in 1850. The major coal deposits of the State are contained in Permian Coal Measures in the Sydney-Gunnedah and Oaklands Basins. Coal quality ranges from high volatile, high moisture thermal coal at Oaklands to low volatile hard coking coal in the Southern Coalfield. Most coalfields can provide a range of steaming and coking coals.

Jan 1, 1988

By Woodhouse M, Andrews D, Drew G

The nickel deposits within the Honeymoon Well project area (26¦ 40'S, 120¦ 25'E), located 45 km south of Wiluna, occur in the northern part of the Agnew-Wiluna belt (Figure 1; Hill et at, 1990). The project area is covered by up to 50 m of transported material which greatly hampers both exploration and an understanding of the bedrock geology. Since 1990 intensive exploration has increased the resource from 10 Mt at one per cent Ni to 134 Mt at 0.76 per cent Ni in five deposits (0.4 per cent Ni cut-off, resources above 300 m depth, December 1994). This includes a massive sulphide resource of 2.5 Mt at 3.4 per cent Ni.

Jan 1, 1996

Computation is believed to be a powerful tool in scaling-up chemical processes and in designing materials, however, is being challenged by low predictability and limited scalability. This presentation will discuss the promising future of multi-scale computation in solving these two problems to realise the real-time simulation of industrial processes. Multi-scale structures are a common nature of most chemical systems and the meso-scale phenomena are believed to be the road blocks not only in improving the predictability of physical modeling but also in extending the scalability of computation. Focusing on the meso-scale phenomena, a series of research has been carried out at the Institute of Process Engineering, Chinese Academy of Sciences, for the past three decades. Starting with a simple idea of modeling the meso-scale clusters in gas-solid two phase flows, the so-called EMMS (Energy-Minimisation Multi-Scale) model was established. In verifying the stability condition of the model, the pseudo-particle approach was proposed to explore the micro-mechanisms in particle-fluid systems, and the strategy of the EMMS model was extended to other six different multi-phase systems, resulting in a unified conceptual formulation of multi-phase complex systems expressed by a multi-objective variational problem. In applying this model to different multi-phase systems and to industrial problems, it was recognised that the EMMS model defined a new paradigm of multi-scale computation by realising the structural similarity between software, hardware and the problems to be computed. This paradigm of computation was implemented on a multi-scale supercomputer with a capacity of 1.0 petaflops by integrating CPUs and GPUs (Graphic Processing Units), showing high efficiency and low cost. Running the EMMS model on this computer, the simulation of hydrodynamics of multi-phase systems can be speeded up very much, indicating a promising future of virtual reality of process engineering. The presentation will review this series of work, introduce successful applications in industries, and will be concluded by emphasising the critical importance of the meso-scale phenomena as the bridge between macro-dominants and micro-mechanisms. This is an ABSTRACT ONLY. No full paper was prepared for this presentation.

Sep 13, 2010

The modern resource extraction enterprise is a complex capital intensive business operating in a world of constantly evolving social, environmental and economic scrutiny. Investors, government, media and special interest groups expect to see business environmental and social performance respond and deliver increasing corporate responsibility and sustainability.   Thorough interrogation of business performance using a multi-disciplinary due diligence approach presents a more sophisticated review and benefits beyond the traditional compliance/conformance 'audit' style assessment.   Using a due diligence approach allows assessment through a comprehensive lens which examines potential short- and long-term risks including sometimes less tangible environmental and social liabilities, and informs management, investors and regulators of broader business performance. This approach provides information in a form that business can measure performance in a repeatable and enterprise wide sense.   This paper provides an outline of the due diligence process applied in this way, drawing from lessons learnt and industry based experiences in the due diligence process and the benefits and tools that can  be applied in an environmental and social due diligence business performance assessment

Jun 1, 2010

By M Foster

The new environmental legislation of 1986 was left incomplete and to date remains so. The 'missing' process by which environmental consideration should be applied was never embodied in law and has predisposition to a wide interpretation. The Resource Statutes which govern land use and development place demands on the environmental process without that definition. The Resource Statutes are themselves under review by Government. There is a new Government Department of Conservation. It is still in its early days and facing a challenge to compose its role as a steward over large tracts of land holding significant marketable resources, animal, vegetable, mineral, and abstract. It has also taken over numerous consent and advocacy roles in legislation beyond its own empowering Act. Enter the mining company, anxious if not able to get an easy passage for consents to prospect and mine, then at least to have a clear path to tread to get there, within a fixed time period. Whichever options appear available to process environmental approvals, public participation is that being favoured most by the regulatory bodies. Where a public notification of consent applications is mandatory, public participation should lead to the fastest track available.

Jan 1, 1988

The Kwademen Au deposit was discovered in 1977- 1978 following a regional geochemical survey carried out as part of a UNDP (United Nations Development Programme) and BUMIGEB (Bureau des Mines et de la Geologie du Burkina) mineral exploration programme. The climate in Burkina Faso is rather dry, with markedly seasonal rainfall averaging 800 mm pa in the Kwademen project area. The relief is low and the drainage poorly developed, so that soil sampling was preferred to stream sediment sampling. Rocks have been subjected to deep lateritic weathering, so that they are transformed into a mixture of Fe-oxides and kaolinite over depths varying between 30 and 40 m. At the regional stage, soil samples (30-40 cm depth) were collected a a 300 x 500 m grid. The Kwademen deposit was indicated by Cu, Zn, Mo and Au anomalies. Subsequently, an area of 9.2 km2 was covered by a detailed geochemical survey by soil (100 x 50 m) and auger sampling. The regional anomaly was fully confirmed, and subsequent drilling intersected mineralized ore shoots, justifying the establishment of an evaluation project led by the U.N.R.F. (United Nations Revolving Fund) in 1983- 1985.

Jan 1, 1988

By S Lloyd, J Chow, S Fitzpatrick, D Greenup

The Tropicana deposit was discovered in 2005 after AngloGold Ashanti followed up an unexplained gold-in-soil anomaly. Discovered in a remote, barely-explored area of Western Australia not previously thought prospective for gold, Tropicana is the most significant gold find in Australia for more than a decade. The new, large scale open pit gold mining operation will produce an annual production of around 330 000 to 400 000 oz over a ten year mine life mining around 60 Mt/a.Process plant construction started in early 2012 and is due to finish in the December 2013 quarter. The mining contract was awarded to Macmahon Holdings (Macmahon) and mining commenced in July 2012 using conventional drill and blast, truck and excavator open cut methods.As a construction and start-up project in a greenfields location, the establishment of mining activities at Tropicana Gold Mine (TGM) involves the implementation of technical and operational systems, including the mining contract. Some of these systems and likely challenges were identified during earlier studies, while others were not foreseen until they were encountered. Alternatively, the time frames around implementation change depending on the changing knowledge of the project and industry environment. These systems include those common to the industry and those specific to the operation and location.This paper examines the implementation and development of a number of the systems specific to the establishment of mining operations, including the history, process and some outcomes. Although expected to be discrete systems to implement, they become interdependent. This linkage between systems further offers challenges and opportunities for the continuous progress of each system and for TGM as a whole.CITATION:Chow, J, Fitzpatrick, S, Greenup, D and Lloyd, S, 2013. Tropicana Gold Mine - mitigating the challenges of a mining start-up, in Proceedings World Gold 2013 , pp 51-60 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By J Allen, B Oats, S Palaniandy, M Lollback

The Julius Kruttschnitt Mineral Research Centre has conducted an intensive VertiMill® (VTM) survey program at the Cannington mine concentrator as part of the ‘collaborative research in stirred milling technology’ program funded by Metso Minerals. Since 2003, Cannington has progressively added grinding capacity into the circuit through VTMs operating in secondary and regrinding duties. Cannington was one of the first mines to adopt this technology in secondary duty by installing two VTM-1500-WBs as part of a capacity expansion to produce sub-100 µm rougher feed. Subsequently, an additional VTM-800-WB was installed in the lead regrind circuit to prepare sub-20 µm cleaner stage feed.Several surveys were carried out to evaluate the VTM performance over a range of changed conditions. Among the key changes in operating variables were circuit power draw, feed rate and water addition to the bottom of the mill. The average specific energy for secondary duty was 3.7?kWh/t. The lead and zinc regrind mills consume 8.1 and 15.3 kWh/t respectively. Generally, the VTM installations have successfully prepared feed for rougher and cleaner circuits by reducing the top size into the floatable regime with steeper particle size distribution, which has led to enhanced recovery. The survey results show the success of VTM installations in secondary (receiving feed from autogenous circuit) and regrind duties.CITATION:Palaniandy, S, Powell, M S, Hilden, M, Allen, J, Kermanshahi, K, Oats, B and Lollback, M, 2014. VertiMill® performance updates in secondary and regrind duties at Cannington mine, BHP Billiton, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 263–272 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By I M. Howard

With the bell-less top (BLT) charging system replacing the centuries old double bell charging method, the furnace efficiency has been greatly improved together with considerable reduction in the furnace down time and operational problems. But still there are many draw-backs which need further attention to achieve better efficiency and operational effectiveness. The performance and operational problems of the BLTs have been highlighted and possible solutions to overcome some of the major problems are discussed.

Jan 1, 1999

By R E. McIvor, K M. Bartholomew

Classification system efficiency (CSE) is a simple, powerful metric that provides a comprehensive measure of classification system performance. CSE directly quantifies the amount of coarse solids in the mill, and as a result, also directly quantifies the percentage of mill power being used effectively. In this manner, it is an effective, practical grinding energy efficiency metric.Three independent variables drive CSE: circulating load ratio, sharpness of classification, and classifier bypass. Due to practical downstream constrains on per cent solids, improvements realised by increasing circulating load reach diminishing returns as sharpness of classification and bypass deteriorate in the most commonly used classification device, the hydrocyclone. This combination of effects leads to the use of CSE, and its relationship to operational economics, as an objective circuit optimisation criterion.Its simplicity in measurement makes CSE a useful tool for the plant metallurgist, and it is not subject to a great amount of experimental error. CSE provides the plant operator a fast, simple, and effective means to evaluate the performance of the plant classification system. Improvements in CSE relate directly to circuit throughput and energy efficiency. This paper, through description and plant case studies demonstrates the power and utility of this emerging grinding system optimisation metric.CITATION:Bartholomew, K M and McIvor, R E, 2013. Classification system efficiency - a comprehensive closed-circuit grinding optimisation metric, in Proceedings World Gold 2013 , pp 389-394 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By G Kirk

Definition and delineation of in-pit ore and waste material are the most significant tasks for an open pit production geologist; adding or destroying value in the mining value chain. Anglo American’s Mogalakwena Platinum mine, an open pit operation in South Africa moving 100 Mt/a, has recognised the value of improved material definition and is in the process of changing from blasthole to reverse circulation (RC) sampling for in-pit grade control. This is aimed at obtaining more representative samples, which are required to maximise ore recovery, minimise waste dilution and to increase the accuracy and confidence of production forecasts. Early in the project, it was realised that the key risks for implementing RC grade control were related to change management processes, rather than failure of technology. Recognising the importance of this issue, Mogalakwena chose an integrated implementation approach that incorporates all stakeholders of the mining cycle in order to develop a process that delivers maximum value and is sustainable within an active mining environment. The following core goals were addressed over five phases of project implementation: extensive definition and design of integrated project implementation, comprising: project buy-in and ownership from all key stakeholders, including survey, geology, mine planning, drill and blast, load and haul, maintenance, supply chain and finance; and detailed analysis of all potential issues and possible solutions, allocated to stakeholders as part of the scoping process; optimising hole patterns and drilling procedures, focusing on delivering maximum value for minimum cost using multiple scenario analysis from borehole data and operational sequencing requirements; and evaluation of lessons learnt during project implementation in order to optimise the technical solution and operational efficiencies. Although this project is not yet finalised, Mogalakwena Platinum Mine is already providing a blueprint for the effective development, implementation and optimisation of sustainable in-pit grade control RC drilling for other open pit mines within Anglo American plc.

Aug 22, 2011

By R J. Goldfarb, A B. Christie, D I. Groves

Small orogenic gold deposits have the same deposit-scale geological and geochemical features as those that characterise giant orogenic gold systems (>16 Moz Au). Therefore, a broader-scale approach is needed to identify the critical controls on giant deposits and their disproportionate distribution throughout time and space. Ages of giant gold systems cluster around well-defined periods of lithospheric growth at continental margins, and it is orogen-scale processes during these Late Archaean, Early Proterozoic and Phanerozoic times that determine gold endowment of a province.   A critical factor for giant orogenic gold provinces appears to be asthenospheric upwelling at the time of gold mineralisation to most effectively transfer the thermal energy required to initiate and sustain high hydrothermal fluid flux. The extent of this fluid flux should be related to thickness of the lithosphere beneath a province at the time of gold mineralisation, such that giant gold deposits are much more likely to develop in orogens with oceanic or thinned continental lithosphere. A proxy for the latter is likely to be a short premineralisation crustal history such that thick subcontinental lithospheric mantle was not developed. Conversely, orogens with protracted premineralisation crustal histories are more likely to have a thick subcontinental lithospheric mantle, which is difficult to delaminate and, hence, such provinces will normally be poorly endowed. The nature of the lithosphere also influences the intrinsic gold concentrations of potential source rocks, with back-arc basalts, transitional basalts and basanites enriched in gold relative to other rock sequences. Thus, segments of orogens with thin lithosphere may be defined by conjunction of giant-scale fluid flux through gold-enriched sequences.   Although the nature of the lithosphere plays the crucial role in dictating which orogenic gold provinces will contain one or more giant deposits, the precise siting of those giants depends on the critical conjunction of a number of province-scale factors that control fluid conduits, traps, and seals in tectonically and lithospherically suitable terranes within accretionary orogens.

Jan 1, 2005