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By S van der Sluijs, M van Ende, Y Tang, A Emami

This paper presents a phenomena-based model for investigating the possibility of scrap melting in an Open Slag Bath Furnace (OSBF) for green ironmaking. The goal of this study is to enhance the circularity of the steelmaking process by utilising scrap as a green source of iron in OSBFs. The model takes into account the fundamental differences between OSBFs and traditional processes such as Electric Arc Furnaces (EAFs) and Basic Oxygen Furnaces (BOFs). The model considers three primary regions where scrap heating and melting occur: the solid feed pile, slag and hot metal. It accounts for factors such as the furnace geometry, scrap charging mechanism and specific heat and mass transfer properties of the reactor. The model was validated using literature data and was used to investigate the heating and melting behaviour of individual scrap particles under various process parameters. The study finds that the scrap melting process in OSBFs involves three stages: shell formation, shell remelting and subsequent melting of the parent scrap. The carbon content of the scrap and the liquid hot metal plays a critical role in determining the melting behaviour. Depending on the carbon concentration and temperature, the melting process can be heat transfer controlled or mass transfer controlled. The paper also examines the scrap feeding methods in OSBFs, including direct charging into the slag or charging through a feed pile. The model provides insights into the melting rate of scrap compared to Direct Reduced Iron (DRI) in OSBFs and highlights the role of carbon in this process. Overall, this phenomena-based model contributes to the understanding of scrap melting behaviour in OSBFs and provides valuable insights for optimising the circularity and efficiency of green ironmaking processes. The findings of this study can inform the design and operation of OSBFs, paving the way for increased utilisation of scrap as a sustainable feedstock in the steel industry.

Jun 19, 2024

By M J. Pejovic, S BoÜevski, I Miljanovic, M Hudej, A Milutinovic, A Petrovski

The paper deals with the problem of managing the supplies of consumables (energy resources, lubricants, explosives, explosive supplies, tires, spare parts, etc) in mines. After the introductory remarks and comments, a general stochastic model of supply, relating in general to the dynamic programming method is presented. A selection of stochastic supply model for experiments and research by the authors of this paper is not a coincidence, based on of their long experience, showing that this type of model is the most suitable to provide support for decision-making and management of supplies of consumables in mines.In order for the problem?of?consumables?supply?management to be reviewed, in whole and objectively from the aspect of risk, experimental tests of the stochastic model in real conditions were performed at the limestone open pit mine æZelenikovecÆ near Skopje, the capital of Macedonia. The scope of the experimental research enabled reliable analysis. The results obtained confirm the efficiency and reliability of the stochastic model and two separate manipulative-operational positions regarding its application, which may have an important influence on the optimisation of supplies.

Sep 26, 2011

By M A. Noppé

"Mining is an inherently risky business: from the technical, environmental, social and economic uncertainties associated with advancing an exploration concept to a viable project; to the risks associated with the operating, market, and safety risks and uncertainties attached to a developed mine; and the final mine closure process.Investors and other stakeholders assessing the risk, opportunity and relative value associated with a resource project need to appreciate the project in its correct context. Errors, omissions, biased reporting or conflicting information in reporting may result in a misinterpretation of technical and financial results, leading to biased estimates or assumptions on project value (Noppé, 2016).Simplistically, a project can be assessed on three key areas for positioning the project in its correct relative context, namely: the project development stage the confidence in the estimated quantities and qualities of the resource, reserve and/or product the level of accuracy, precision and confidence in the technical and economic studies supporting the project.In the latter case, the ‘technical and economic’ information includes assessing the necessary social, environmental and commercial/legal/governmental approvals for the project.Responsible management of a resource project through its full life cycle relies on competent and dependable control and direction being effectively provided by the technical, business and board leadership of the organisation. In turn, the project information must be effectively communicated between various disciplines, these disciplines and the company, and the company and its stakeholders.CITATION:Noppé, M A, 2016. Responsible management and transparent reporting across the project life cycle, in Proceedings Life-of-Mine 2016 Conference, pp 5–7 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 28, 2016

By R C. Morris

Two major types of economic secondary iron ores occur in the banded iron formation (BIF)-rich Hamersley Province of the Pilbara, Western Australia:dominant BIF-hosted bedded iron deposits (BID)detrital ore deposits (DID sensu lato), which are mainly hosted in the three province-wide Cenozoic sequences that include coeval non-ore sediments and comprise:a. the major Miocene, fluvial channel iron deposits (CID)b. the lesser Eocene and Pliocene detrital iron deposits (DID sensu stricto).Striking differences exist between the massive CID resources and the much smaller underlying and overlying DID. CID are essentially riverine alluvial ooidal rocks with abundant small fossil wood fragments and variable iron peloids, but with only extremely rare recognisable lithic remnants. The original matrix is typically ramifying layered goethite. Eocene DID are mainly alluvial with minor pisoids, whereas Pliocene–Quaternary DID are dominantly coarse colluvial gravels, both derived from and largely retaining the original textures of BID, hard cap or variably ferruginised surface BIF. The colluvial DID matrix is typically ferroan-aluminous soil, resulting in canga where replaced by goethite, which may be dehydrated to hematite by exposure. The Cenozoic deposits occur in two dominant geomorphological environments: the southern Marra Mamba to Brockman Iron Formation strike valleys containing all three Cenozoic sequences and the much later northern Brockman Iron Formation plateau valleys that include only the Miocene and Pliocene sequences. The Cenozoic detritals formed in different climatic regimes, with an extended dry period forming a prominent province-wide dehydrated carapace on the Eocene DID. The Miocene ‘optimum’ followed with its thick scrub-covered deep regolith that produced the fossil wood-rich CID and was succeeded by the arid cool period of the Oakover limestone/calcrete. A major renewal of exposure and erosion in the Pliocene resulted in the extensive iron gravels of the Pliocene–Quaternary.CITATION:Morris, R C, 2015. The Cenozoic detrital iron deposits of the Hamersley Province of Western Australia – a tribute to Mal Kneeshaw, in Proceedings Iron Ore 2015, pp 319–326 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

This paper examines the complex interplay of deposit characteristics, mining plans, tailings disposal techniques and rehabilitation requirements on planning for mineral sands operations. All component parts of this mining cycle are interdependent and cannot be evaluated in isolation when optimising a mineral sands operation. This is most evident when projects are large-scale or involve resources that contain complexities such as high slimes content, consolidated hard band materials, acid forming materials and radioactive materials. Projects located in environmentally sensitive areas add further to the need for more stringent planning. This paper describes the analysis techniques adopted by Hatch to evaluate mining and tailings placement options for a dredging and floating concentrator system. The principles and methods used in the analysis are applicable to any mining system involving the complexities listed above. The focus of this paper is on the reconstitution of mined material as tailings and the impact of this process on mining schedules and tailings construction and placement options.

Jan 1, 2001

By R Hartner

Digital optical microscopy (DOM) and automated SEM-based (ASEM) mineralogy systems (MLA, QEMSCAN) have experienced significant developments within the last decade. However these developments have been independent from each other and the two mineralogical techniques have so far not yet been integrated to combine the strengths and technical benefits of both analytical platforms. This detailed comprehensive mineralogical information is critical support for geometallurgy.Major hardware and software advances in DOM in the last few years have provided important new capabilities with potential applications to automated mineralogy. These technological advances have been largely driven by sectors outside mining (eg medical pathology) and have not yet been widely adopted within the minerals industry. The advent of DOM offers significantly more automated mineralogy capabilities than traditional expert-mineralogist driven optical microscopy. This is based on advances in automated image acquisition, high resolution cameras for digital imaging, imaging of large areas through mosaic options, integration of multiple layers and application of advanced image analysis techniques.Ongoing research involves combining the outputs of DOM and ASEM-based microscopy to create new capabilities for integrated microscopy based on development of advanced cross-platform image fusion and data integration between DOM and ASEM (exploiting the benefits of both analytical platforms). This requires non-linear image registration and transfer of mineralogical identification from ASEM to DOM systems using sophisticated image manipulation and data analysis software.Examples will be given of image fusion and data registration for a range of different ore types. Image fusion techniques are demonstrated using a porphyry copper deposit sample where sulfides and precious metals are classified using the MLA and gangue mineralogy obtained from DOM images. Data integration enables creation of a library containing optical property variability information for minerals identified by the MLA; thus reducing the reliance on skilled mineral identification by supplementing human interpretation

Sep 5, 2011

By M Forbes, R Jeuken

Brownfields geoscience measurement such as drilling and surface geophysics can be costly and it is often difficult to weigh the cost of data collection and processing against the value it unlocks at the time of extraction. This makes it difficult to prioritise geoscience expenditure and find the optimum intensity of geoscience activity across competing assets. There are multiple options for managing resource uncertainty and spatial variability through mine planning and resource engineering such as varying marketing strategy, adjusting stockpile or other infrastructure design and product blending. Consideration of these alongside increased data collection further complicates finding a comparable value of geoscience programs to determine the right blend of geoscience measurement and engineering controls. Concepts similar to Value of Information (VOI) analysis which is applied to strategic planning can be used to estimate the value of geoscience measurement and pit sequencing at tactical planning and operational timescales. This involves the quantification of resource uncertainty and prediction of how it will affect resource extraction. This paper outlines this process and demonstrates its use to prioritise geoscience at BHP Coal Assets. The value of infill drill programs in enabling operational stability is quantified and compared the value of engineering controls like increased stockpile capacity. This study supports that idea that the application of VOI methods to bulk mining at tactical time horizons has potential to inform geoscience planning and resource engineering not just separately, but as part of a unified strategy for managing resource uncertainty.

Mar 22, 2022

By L Nagy, K P. Juhasz

The authors were engaged to optimise a traditional rebar cage reinforced concrete segmental lining by means of finite element analysis (FEA) using macro synthetic fibres for the Shanghai metro extension. The aim of this study was to reduce or entirely replace the original steel reinforcement of the segmental lining, in order to make the precast production process faster and more economic. The outer diameter of the tunnel was 6200 mm, the thickness of the segments was 350 mm.The numerical calculations were performed by Atena Finite Element software, which is based on the combination of Menétrey-William and Rankine failure surfaces on the compression and tension sides respectively. The effect of the macro synthetic fibres was modelled as tension stiffening on the tension surface.A one-to-one full scale model of an assembled tunnel ring using the original reinforcement cages was tested at Tongji University in Shanghai, July 2013. The ring was tested to differing load levels where load and displacement were measured until failure. The author’s first step was to calculate the real displacement characteristics of the original reinforced concrete (RC) ring, then calculate the numerically modelled version, so as to compare them. The material parameters of the concrete and rebar used had been determined through basic material tests conducted at the Tongji University. (Bi, Liu and Wang, in press).The numerical modelling undertaken has shown good correlation with the full-scale physical test results. Optimisation of the lining reinforcement was achieved through the addition of fibres, resulting in a substantial reduction of the steel rebar cages. Several results have been computed with the numerical model using different dosages of macro synthetic fibres, showing that the mass of steel reinforcement could be reduced by 50 and 75 per cent respectively.CITATION:Juhasz, K P, Nagy, L and Winterberg, R, 2014. Full-round numerical modelling of a macro synthetic fibre reinforced tunnel boring machine tunnel in the Shanghai Metro extension, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 477–484 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By D J. Brake

Faced with the need to improve workplace conditions in both its development and production headings in its existing K1 orebody, as well as its new K Link and K2 orebodies, the Kencana mine in Indonesia took the novel approach of reversing the ventilation on most of its access ramp by outcasting up the ramp to the portal. Working levels were then fed with fresh air via auxiliary fans sealed into the current surface ‘egress’ intake raises (ladderways) or another small surface intake raisebore rather than from fans hung in the ramp as in the past. Outcasting the portal provided a substantial increase in the total mine exhaust capacity allowing fewer levels to be ventilated in series and significantly improving conditions, especially in the most difficult workplaces to ventilate. It also reduced the consequences if there was to be a fire on a vehicle in the ramp. The same system using the ramp as an exhaust is also intended to be used as part of the final ventilation solution for the new K2 orebody which also uses a novel single surface ventilation shaft that is vertically split into separate intake and exhaust compartments using a concrete brattice. Using the main ramp as an exhaust has potential application in many other operations in Australia using surface ramps which otherwise frequently suffer from overuse of series ventilation circuits and poor working conditions at the mine bottom.

Mar 21, 2011

It is very rare in the underground hard rock environment to find a deposit that is ideally suited to a specific mining method. Usually the irregular shape of the orebody will allow the deposit to be extracted by more than one mining method. During the prefeasibility stage, a number of conceptual mine designs are generally evaluated to see which offers the best method of extraction for the deposit. The selected method is usually based on key decision criteria such as the overall extraction of the orebody, the amount of metal produced annually and the unit cost of production. Often the prefeasibility study document will state that the project has an NPV of æxÆ million dollars. This statement can be made without any quantitative consideration of the likely risks of the mining methods reviewed or the level of confidence in the estimation of the NPV. By assigning a probability of failure to each component of the mining cycle a measure of the risk for each method can be determined. One mining method may provide the highest NPV when it is performing well, however, there may be a higher risk of a major failure impacting on the performance of that method, eg the failure of a mass blast of a crown or rib pillar. This paper will present a flowsheet approach to the use of risk analysis for determining the likely production rates of different mining methods. This framework allows the annual metal output to be estimated and from this the NPV for each method. A level of confidence can be applied to the estimated NPV for each option. An example will be presented on how this technique has been used within the Normandy Group.

Jan 1, 1998

By D Chalmers, C C. Harb

The detection and control of gas levels in mining is a continuing challenge for the industry. Standard detectors have many problems that could be overcome with laser based spectroscopic instruments, but to date these systems have not been suitable for mining conditions. This paper reports the development of a new digital data extraction scheme to modernise traditional cavity ring down spectroscopy (CRDS). CRDS is a direct cavity enhanced laser based absorption technique, which is used to allow the identification of an unknown substance by their molecular fingerprint; this unknown substance is identified by analysing the ring downtime of the light exiting the optical cavity. Traditional CRDS has many issues when analysing substances in hostile environments, or when multiple species may be present. This presents an alternative approach, called real-time CRDS (rtCRDS) that has the potential to overcome many of these issues and produces systems that could be used in the mining industry. The system utilises newly developed widely tuning quantum cascade lasers combined with improved optical cavities and novel digital data extraction to produce spectra over a 1500 nm range in a few seconds. The ring downtime measurements produced are accurate and have high sensitivity and maximum signal to noise ratio. This paper discusses the technique, illustrating the advantages compared to traditional systems and show real-time spectra for a set of molecules of interest to the mining industry. This paper also provided an analogy between this approach and that used in digital communications systems, and shows that this scheme is ideally suited to provide a network of sensors in hostile environments.CITATION:Harb, C C and Chalmers, D, 2015. Real-time methane detection – modern digital laser spectroscopy for hostile environments, in Proceedings The Australian Mine Ventilation Conference, pp 161–166 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By I Gray

This paper examines the effects of the changes in stress that a coal may undergo as part of the drainage process. As a consequence of this, some coal seams will come to the situation that they have zero horizontal stress existing within them at the time of mining. The hypothesis of this paper is that this lack of horizontal confining stress means that on mining, the vertical stresses may be easily raised to a level where failure occurs. This failure may be accompanied by significant energy release from energy stored within the coal as well as that coming from the roof and floor. To determine the state of stress within the coal seam, the concept of the effective stress path that the coal passes through is examined and is found to be very dependent on the shrinkage of the coal with degassing, the Young’s modulus of the coal and its Poisson’s ratio. The Young’s modulus of the coal is important and has been found to be highly dependent on the state of stress within the coal. It may change by more than an order of magnitude.CITATION:Gray, I, 2014. The consequences for pillar stability of zero confining stress brought about by forced or natural drainage, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 331–336 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By D Trembath

"One of the key risks to the success of a mining operation is the accuracy of the estimates of both the economic mineral and any accompanying contaminants contained within the ore reserve. Misrepresenting the mineralogical characteristics of the ore reserve can result in considerable financial investment in an operation that is in fact uneconomic and/or carries a significant environmental risk. This in turn can result in an unplanned closure of the operation with associated financial, environmental and social legacy. One way to minimise this risk is to undertake high density resource sampling to gain a better understanding of the resource characteristics. However, such an approach is expensive, time-consuming and often impractical. The risk of not having an accurate model is typically assessed during a feasibility study utilising a Monte Carlo simulation method or some form of sensitivity analysis. Importantly, the error margins used in these types of analyses are often based on subjective or very general criteria such as ‘professional judgement’ or an ‘industry standard’. This presentation introduces a conditional simulation method for developing a range of mineralogical distribution models. Based broadly on the method outlined in Journel and Kyriakidis (2004) the proposed approach develops this work further. It combines a geostatistical analysis of the available data with automated mine design software to provide a rigorous method for assessing the confidence in the mineralogical characterisation of the ore reserve. The process is based on simulating possible mine plans based on the statistical characteristics of the available resource sample data. These plans are then assessed against high resolution resource models generated using a Sequential Gaussian Simulation method. The outcome is confidence intervals for important characteristics of the ore reserve estimate relative to the actual resource. These confidence intervals are an objective and transparent measure important for assessing closure risks and represent an improvement over common practice.CITATION:Trembath, D, 2016. A simulation approach for improving the assessment of closure risks, in Proceedings Life-of-Mine 2016 Conference , pp 36–38 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 28, 2016

By M C. Schodlok

Banded iron-formation (BIF) and iron ores were measured using the CSIRO developed TIRHyLogger ™ to assess its ability to map quartz, carbonates and riebeckite. The TIR-HyLogger™ measures continuously spectral refl ectance data from diamond drill core or drill chips with a high spatial and spectral resolution. Samples from twelve BIF, bedded iron deposits (BID) and channel iron deposits (CID) have been analysed. The spectral data were processed with two different approaches. The first approach, focused on the identifi cation of the major minerals, was performed using principal component analysis (PCA). It identified four minerals (quartz, ankerite, riebeckite and goethite) and provided pure spectra called end-members. The second approach included a mineral diagnostic spectral feature extraction involving wavelength position, relative peak heights and relative depths of absorptions. Quartz has a diagnostic absorption at 8.625 µm and ankerite shows a refl ectance peak at 11.275 µm. In addition to the identified end-members, two carbonate populations (calcite and siderite) and two silica species (quartz and amorphous silica) were identified.

Jul 11, 2011

By J Jackson, K Nguyen, A Nguyen, E Manlapig

"With the recent advancement in drill core imaging systems, a large volume of high resolution drill core images can now be rapidly collected and mineralogically classified. This paper introduces a novel semi-automated method for rapid prediction of process engineering parameters from this type of image. The aim is to allow for a rapid and low-cost assessment of the ore processing variability within a mineral deposit with a reduced amount of metallurgical test work. This method will see its application primarily in the project evaluation phase, where proper evaluation of the processing variability of the orebody normally requires a prolonged and costly metallurgical test work program. Applying this image-based texture analysis method on the mineralogical classified drill core images, the ores are classified according to their textures. For each engineering parameter, a small number of physical test work is required to produce a data set for training and testing of the predictive model. The paper also presents a case study in which this method has been applied to predict the A*b parameter used in mineral process plant design.CITATION:Nguyen, A, Jackson, J, Nguyen. K and Manlapig, E, 2016. A New Semi-automated Method to Rapidly Evaluate the Processing Variability of the Orebody, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 145–152 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By A S. Derrington

This paper describes a hybrid ventilation system, which uses secondary fans that also act as de-facto primary fans to extract fresh airflow from the mine intake raise system. Also discussed are the associated problems such as uncontrolled recirculation, inadequate decline airflow, fire safety issues, prolonged blast fume clearance times, high air temperatures in main access routes, neutralisation of mine air cooling by heat from secondary distribution fans, increased ventilation system complexity, reduced flexibility and high pressure differentials (which cause safety issues with personnel access and reduce secondary ventilation system performance).Practical suggestions are provided on options to avoid these problems listed.CITATION:Derrington, A S, 2013. A critique of the push-pull hybrid ventilation system, in Proceedings The Australian Mine Ventilation Conference , pp 73-78 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By M Tayebi-Khorami

There is an increasing trend in the extraction and development of copper resources from complex deposits. The complex deposits pose mineral processing challenges, as they often contain low grade copper ore, relatively large quantity of clay minerals, complex texture, very fine disseminated ore, high amount of pyrite, and high level of impurity elements such as arsenic. With the amount of arsenic in concentrates increasing and with environment, occupational health and safety regulations becoming more restrict, there is a need for a processing method that results in no arsenic emissions and captures all arsenic while immobilizing it in a compound that is stable under a wide range of conditions, so it is suitable for long-term disposal. Some development work has been undertaken to examine the most effective arsenic treatment option for complex orebodies that contain arsenic, but a technically robust and economically viable option has not yet been developed. Previous research has demonstrated the possibility of separating arsenic-copper sulphides from other copper minerals by controlling the potential of the flotation pulp in the single mineral systems. The selective flotation of enargite from copper sulphides in a real complex ore system was studied by Tayebi-Khorami (2016), which is summarised in this paper. CITATION: Tayebi-Khorami, M, 2018. Arsenic in complex orebodies, in Proceedings Complex Orebodies Conference 2018, pp 132–134 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

By B Rusk, L Corriveau, P Emsbo, R P. Xavier

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Porphyry-Cu (Mo-Au) deposits and iron oxide-copper-gold (IOCG) deposits are both characterised by the presence of abundant halite-saturated fluid inclusions that reflect the circulation of hyper-saline hydrothermal brines. While it is widely accepted that brines involved in the formation of porphyry copper deposits derive from unmixing of moderate-salinity, intermediate-density fluids that exsolve from crystallising magmas, the source of brines that form IOCG deposits remains enigmatic and intensely debated. In this extended abstract, we summarise the fluid inclusion characteristics of both deposit types and present trace element compositional data for halite-saturated fluid inclusions from both porphyry copper deposits and IOCG deposits from around the world.While both deposit types typically contain halite-saturated fluid inclusions, vapour-rich fluid inclusions in IOCG deposits are less common than in porphyry deposits and evidence for fluid immiscibility is rare. IOCG deposits also typically lack intermediate-density fluid inclusions that characterise the deeper quartz-rich veins in many porphyry deposits. Many IOCG deposits contain CO2-only fluid inclusions, a type of fluid not observed in porphyry Cu deposits.Our fluid inclusion compositional data show that most porphyry Cu (Mo-Au)-related brines are dominated by Na, K and Fe and contain elevated concentrations of Ca, Cu, Pb, Zn and Mn up to around the one per cent level. On the other hand, IOCG brines are Na-Ca-Fe-dominated and typically contain far less Cu, Mn and Zn than porphyry brines. In addition to Ca, these fluids are also strongly enriched in Ba and Sr relative to porphyry-related brines. Such compositions are consistent with extensive fluid-rock interaction and/or an evolved sea water contribution to IOCG brines.A sea water or basinal brine source for IOCG brines is further supported by bromine concentrations that are much higher than is characteristic for porphyry-related brines. Porphyry brines have Cl/Br molar ratios of between 800 and 3000, which is characteristic of primary magmatic brines, whereas the Cl/Br composition of IOCG brines is more variable. For example, Na/Cl/Br ratios of most IOCG deposits in the world-class Carajás district fall on or near the sea water evaporation curve (most Cl/Br molar ratios are between 200 and 1000) and are diagnostic of sedimentary bittern brines. A few of the deposits in this district also show evidence of the input of subordinate amounts of magmatic brine. At Ernest Henry, in the Cloncurry district of Australia, most Cl/Br ratios plot close to the sea water evaporation curve, but Cl/Br ratios of up to ~5000 in several samples suggest the input of lesser amounts of magmatic fluids, and possibly evaporite-dissolution-derived fluids. Taken together with geologic constraints, these data strongly suggest that porphyry-type deposits form from the circulation of dominantly magmatic fluids, while IOCG deposits form from large-scale circulation of high-salinity fluids sourced dominantly from sedimentary basins with variable input of magmatic volatiles.CITATION:Rusk, B, Emsbo, P, Xavier, R P, Corriveau, L, Oliver, N and Zhang, D, 2015. A comparison of fluid origins and compositions in iron oxide-copper-gold and porphyry-Cu (Mo-Au) deposits , in Proceedings PACRIM 2015 Congress, pp 271–280 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

Bacterial leaching of sulfide minerals are fairly well established in heap, dump and in situ leaching and the primary bacterial treatment of refractory gold concentrate using CSTR have gained industrial prominence in recent years. Three cultures, a mesophile T ferrooxidans (DSM583), a moderate thermophile Sulfobacillus acidophilus (strain YTF1) and a extreme thermophile (Sulfolobus strain BC65) were used for the biooxidation (pre-treatment) of the Porgera gold-bearing pyrite concentrate under optimum O2 and CO2 enriched air (30 per cent O2 and ten per cent CO2) based on volume ratios. The positive effect of using oxygen and carbon dioxide enriched air for the biooxidation of gold-bearing pyrite mineral was clearly demonstrated where an increase in Fe release rate by a factor of 2.8, 1.8 and 1.5 for DSM583, YTF1 and Sulfolobus respectively were observed compared with the shake flask tests. The lag phase observed with the other test conditions such as in shake flask or with air decreased by about 80 per cent for all three cultures. The average observed dissolved oxygen concentrations in the pulp for these tests were 8.7, 5.8 and 5.0 mg/L for DSM583, YTF1 and Sulfolobus respectively, indicating that O2 was not limiting in these tests. The pulp redox potential was observed to increase with time for all tests coincident with the leaching rate and reaching a maximum of 663 mV, however the maximum value differs for each strain, with DSM583 exhibiting the highest followed by YTF1 and Sulfolobus. Biooxidation of pyrite under optimum gas enrichment at different pulp densities showed near total Iron extraction occurred for pulp densities of three, ten and 20 per cent (w/v). At high pulp densities, more so at 40 per cent than 30 per cent (w/v), the leaching rate decreased rapidly for tests with YTF1 and Sulfolobus. Monitoring of dissolved O2 shows that O2 demand increased with increasing pulp density and the average dissolved O2 concentration observed for YTF1 and Sulfolobus at 40 per cent solids concentration was 1.0 mg/L and below, suggesting limiting oxygen and carbon dioxide conditions for these two cultures. The decrease in leaching rate observed at high pulp densities (30 and 40 per cent) under optimum gas enrichment was accompanied by low metal dissolution and low redox potential values which was attributed to shear stress due to attrition of cells by high solids concentration, toxicity of metal ions especially Ag and Fe and the formation of precipitates and jarosites as confirmed from XRD analysis of leach residues hence impeding the leaching process. Limiting conditions due to high pulp density and viscosity were only observed for YTF1 and Sulfolobus. The subsequent cyanide leaching for precious metals from the pre-treated pyrite concentrate in all cases shows the extent of gold and silver recovery increased with the degree of pyrite oxidation and Au and Ag recoveries in excess of 80 per cent were achieved compared with only 18.1 per cent and 35.9 per cent for gold and silver respectively when treated by direct cyanide leaching on the original, untreated concentrate.

Jan 1, 2004

By J P. van Dyk

A new crude ilmenite beneficiation process was recently proposed that allowed for the preparation of a smelter grade ilmenite from ilmenite with elevated chromium content. Magnetising roasting was not utilised in the process. As part of this circuit an ilmenite low susceptible reject stream was produced that had a low magnetic susceptibility. In this article a magnetising roasting process was investigated to beneficiate this material. Tests were conducted on material produced by pilot scale simulations on a typical South African East Coast heavy mineral reserve. The results obtained were compared to those published in literature for crude ilmenite. The small-scale experiments were used to define approximate operational limits for the oxidising roasting of a low susceptible ilmenite low susceptible reject stream, although industrial roasting conditions may differ significantly from those obtained in laboratory units. In a next phase these results will be confirmed on pilot plant scale.

Jan 1, 2001