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Both here and in Australia, the unique commercial and tax features of joint venture are finding favour in forestry, fishing, technology and infrastructure projects. For New Zealand mining companies, joint ventures provide a means of access to foreign know how and investment funds, while retaining their corporate independence and their hard-earned tax losses.   This paper discusses some of the practical income tax and GST considerations where a joint venture structure is contemplated. The first part of the paper considers income tax, and in particular how joint ventures enable companies to access and carry forward tax losses. It explains why a joint venture may be advantageous relative to a jointly owned company.   The second part of the paper concerns GST and the focus is on two aspects: 1.   Joint ventures may be registered for GST. In some instances they have no choice and are required to do so. Where a joint venture is registered in respect of a taxable activity, the members are not permitted to register in respect of the same activity. This may be problem where the member has incurred its own expenses and the member wishes to register in its own right to claim back the GST on those expenses. This paper explores the issue and possible solutions. 2.   It is not uncommon to see joint ventures claiming GST on the costs of production, and the production being sold (and GST is being charged) by the members. In this paper we consider whether these arrangements have a tax risk, and what can be done to make them technically sound.

Jan 1, 2005

The role of government and the community has changed significantly over the last two decades in relation to environment protection, particularly in the mining sector. Increased community expectations have moved well ahead of regulatory requirements, and there is now a much greater appreciation generally of the concepts of ecologically sustainable development and intergenerational equity, and the gap between current practice and practices which would be in harmony with these concepts. Besides providing a `safety net' through regulations to ensure that basic environmental performance standards are met, government is now working proactively with the mining industry to encourage higher levels of environmental performance. This paper describes some initiatives between the Commonwealth government and the industry designed to achieve these higher levels of environmental performance, through programs aimed at the paradigms of best practice environmental management and continual improvement.

Jan 1, 1997

By T O&apos, Sullivan

Reconciliation of metal production from a sublevel cave (SLC) mining operation is a complicated process. SLC reconciliation is unlike reconciliation for open stope operations, where a tonnage of extracted ore can be assigned to an exact volume of in situ ore, and a direct comparison made between the estimation of contained metal and actual metal production. In SLC operations the ore extracted from a particular SLC drawpoint will be composed in part from the parcel of freshly blasted in situ material, in part from varying components of ore material (from cave stocks) flowing down from other previously mined areas vertically above the current draw position and in part from external dilution. This leads to difficulties in reconciling production grades against estimated grades. The problem is that we know how much metal we have produced but we can not precisely say where it has come from. Metal production reconciliation is fundamental in assessing ore reserve estimation accuracy and performance and in determining a draw management strategy for SLC mining. In terms of contained metal, differences in extracted metal compared to in situ metal represent changes to cave stocks. To generate local estimates of the cave stocks, differences in metal for each ring are treated as additions to or subtractions from a series of vertical columns of stocks extending throughout the height of the cave. The sum of metal differences (extracted versus in situ) for each vertical column results in a residual metal map at any particular mining level. The metal maps show areas where the metal production has been greater than or less than expected. The maps also highlight areas in the cave where residual metal is located, areas where targeted overdraw can reduce cave stocks.

Jan 1, 2006

Listing on Australian Stock Exchange Limited ('ASX') is a means by which a company can prosper and grow by gaining access to a large capital market. This currently stands at over $300 billion for domestic securities listed on ASX. A company seeking listing will benefit from a higher profile and a greater spread of shareholders. These result from, among other things, improved communications with the investment community. ASX recognises that a decision to list is an important step for a company. Owing to the diverse nature and size of the companies that consider listing and the various steps involved, it is recommended that guidance of professional advisers is sought as early as possible in the listing process. A company seeking listing on ASX must meet the prerequisites for admission to the Official List which, along with the continuing obligations that must be complied with following admission, are contained in the Listing Rules of ASX. Listing on ASX requires a company to ensure that, among other things, the market is fully informed at all times so that investors can make informed investment decisions.

Jan 1, 1996

By A P. Wibowo

Indonesia holds a significant role in the utilisation of coal resources in the world. Although the number of Indonesian coal resources and reserves do not fall into the world’s top ten, according to 2009 statistics, Indonesia is the seventh largest producer of coal with a production of 256 Mt. More than 80 per cent of this amount is sold in the export market, making Indonesia the world’s second largest coal exporter. Most of the exported coal from Indonesia is used to fulfil the needs of the Pacific market, such as Japan, Taiwan, China, among others. It is also possible to reach the Atlantic market.Along with Indonesia’s development program, until 2025 the Indonesian government has adopted a National Energy Policy that aims to reduce the role of petroleum in electricity generation and replacing it with coal. As a follow-up of the policy, since 2009 PT PLN, the state electricity company has built steam power plants throughout Indonesia as an implementation of the first stage of the Electrical Acceleration Project with a capacity of 10 000 MW. Moving forward, in 2011 PT PLN will also build the second stage of the project with a capacity of 10 000 MW. As a result of the program, the domestic need for coal is expected to increase as much as 44.8 Mt.With the increase in domestic need and decrease in the number of reserves, the Indonesian government has adopted policies to secure the domestic coal supply. A policy that may potentially be adopted by the government is the limiting of coal production, seeing the high rate of increase in Indonesian coal production. The adoption of such a policy will change the distribution map of coal in the Pacific market. Thus, this paper will evaluate the change of coal distribution patterns in the Pacific market along with the increase in Indonesian domestic needs and Indonesian adoption of policies regarding the securing of coal supplies.

Nov 22, 2011

By U König, N Norberg

Traditionally, quality control of iron sinter has relied on time-consuming wet chemistry. However, the mineralogical composition that defines the physical properties, such as strength or reducibility, is not monitored.X-ray diffraction (XRD) analysis in combination with Rietveld quantification and statistical data evaluation using partial least squares regression (PLSR) has been successfully trialled to determine the mineralogical composition and process parameters such as the FeO (Fe2+) content and basicity of iron sinter within an analysis time of less than eight minutes per sample. The results were compared with wet chemistry data.PLSR does not require pure phases, crystal structures or complex modelling of peak shapes. The analysis is therefore easy to set up and ideal if only one property needs to be analysed. PLSR results show an accuracy for the FeO content of ±0.3 per cent for the samples analysed in this case study.Both the PLSR and Rietveld methods take the full XRD pattern into account and can be simultaneously applied on the same measurement. PLSR was found to be the more robust method if only FeO and basicity results are required. The Rietveld method helps to predict other parameters, such as the compression strength of the sinter, by monitoring all existing phases (eg larnite C2S or silico-ferrite of calcium and aluminium phases).CITATION:König, U and Norberg, N, 2015. Iron sinter process control using x-ray diffraction, in Proceedings Iron Ore 2015, pp 53–60 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By H Utama, hi, A Suw

PT. Indo Muro Kencana (PT.IMK) is gold and silver mine located in Central Kalimantan province, Indonesia. Mining activities in PT.IMK is conducted in Bantian pit area by applying surface mining method and using combination of excavator and hauler (articulated dump truck and rigid haul truck) as the transportation for ore to the crushing plant and waste material to the waste dump. Current blasting practice is ore-waste blasting. Ore-waste blasting is the term where the ore and waste rock are blasted in the same blasting process. Blasting is conducted by using nonel initiation system. By multiple pits operation, monthly powder factor is varied from 0.23 kg/t to 0.27 kg/t. Emulsion blend with density 1.15 g/cc is used as bulk explosive. At this stage, the concept of geoblast is proposed as an engineering tool for Drill and Blast engineering practice in PT.IMK. In addition, there is a need to maintain rock fragmentation by blasting, to maintain monthly powder factor, and to maintain excavator’s productivity. Next, the concept of scaled depth of burial (Chiappetta and Treleven, 1997) and the concept of blastability index (Lilly, 1986) are proposed as geoblast’s tools to improve blasting practice in PT.IMK. It is expected that rock fragmentation by blasting, explosive consumption and excavator’s productivity will be maintained by integration of geoblast and drill and blast engineering. Furthermore, the objective of this paper is to integrate geoblast and drill and blast engineering in order to create an engineering guideline in PT.IMK. Additionally, blasting trials with air decking application is proposed in order to support the geoblast’s improvement. It is planned that these blasting trials will be conducted in 2022. In conclusion, it can be seen that integration of geoblast and D&B engineering in PT.IMK is relevant to improve current drill and blast current practice and applicable to maintain rock fragmentation by blasting.

Nov 29, 2022

By S Hapugoda, J R. Manuel, M J. Peterson, A Poliakov, E Donskoi

The occurrence and deportment of manganese in a number of ferromanganese and Mn-bearing iron ore samples from supergene-upgraded deposits, as well as from magnetite banded iron formation (BIF) and magnetite skarn deposits, was characterised in order to provide a basis for improved understanding of the processing characteristics of different ore types and investigate the potential for development of a robust geometallurgical classification for Mn-oxide ores. An understanding of the Mn mineralogy in mixed Fe-Mn deposits is necessary to inform any attempt to separate the Fe and Mn during beneficiation and to understand and predict the behaviour of lump and fine ore products during processing.A suite of analytical techniques was utilised, including hand sorting of lump ore particles, optical microscopy, X-ray fluorescence (XRF)/inductively-coupled plasma mass spectrometry (ICP-MS) chemistry, X-ray diffraction (XRD), scanning electron microscopy (SEM)/electron probe microanalysis (EPMA) and gas and solid phase pycnometry, in order to elucidate manganese mineralogy, mineral chemistry and mineral textures. Manganomelane group minerals (eg cryptomelane, hollandite), pyrolusite and lithiophorite were the most common manganese oxides in the samples examined. From the microprobe work, there was evidence of probable substitution of Mn, as well as Al and Si, into the structures of goethite and hematite. Manganomelane minerals were often intimately associated with goethite, in particular, and a clarification of this association and the associated Si and Al impurities is fundamental for improved understanding of beneficiation and sintering behaviour of Mn-oxide ores. Due to the poor or very fine crystallinity of some supergene manganese deposits and of some Mn oxide minerals, in particular the extent of overlapping peaks and their variable mineral chemistry, XRD was a problematic technique to equivocally determine Mn mineralogy.For lower-grade, earthy, poorly microcrystalline ores the mineralogical and textural association between mixed Mn, Fe and Al (¦ Si) phases was also critical. The deportment and potential separation of these elements in these deposits, especially Al, was complex, as they were characterised by forms of æhydrousÆ cryptomelane with higher levels of Fe-Al-Si substitution, as well as intimate intergrowths of ochreous-earthy goethite (probably aluminous in part) with cryptomelane, lithiophorite and/or kaolinite.Trace amounts of alkali elements in ferromanganese deposits were considered likely to be preferentially structurally associated with Mn oxides, while lateritic deposits with significant amounts of lithiophorite could contain elevated levels of deleterious impurities; Co and Ni in particular.A combination of solid and gas phase pycnometry proved to be a useful technique for broadly discriminating hematitic, goethitic and mixed Mn oxide-goethite lump particles based upon differences in their envelope and apparent densities. Based upon these preliminary results and ongoing Raman spectroscopy work on manganese deposits sensu stricto, Raman spectroscopy is a technique considered to have promise during targeted research to better link the optical and compositional properties of ferromanganese ore particles. CT-scan (computed tomography scan) analysis could also be combined with Raman spectroscopy and pycnometry to link mineral composition, mineral texture, ore particle textures and particle porosity/permeability to the high-temperature processing behaviour of lump and fines products.CITATION:Peterson, M J, Hapugoda, S, Manuel, J R, Donskoi, E and Poliakov, A, 2013. Textural characterisation of manganese minerals to improve the geometallurgical characterisation of ferromanganese and iron ores, in Proceedings Iron Ore 2013 , pp 281-300 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By S C. Dominy, R C. A Minnitt

Determination of the sampling constant and liberation diameter are of importance when applying the Fundamental Sampling Error (FSE) equation to optimise sampling protocols. The method for the direct determination of the sampling constant is based on the æGy 50-pieceÆ experiment and variants thereof, which is generally known as the heterogeneity test. In the coarse gold environment, the heterogeneity test is prone to poor repeatability and bias due to the very heterogeneity that it aims to quantify. A key issue is the large sample mass that can be required in the coarse gold environment, which may reach 1 t or more. The heterogeneity test often provides an evaluation of the background gold grade heterogeneity, but understates that of the high-grade coarse-gold component. This is because the total mass of fragments is usually too small to represent the mineralisation. Despite this relatively well-known problem, heterogeneity tests are often undertaken on deposits where the presence of coarse gold is ignored, not fully realised or vastly understated. Sampling types and protocol designs are frequently based on poor quality data that do not match the characteristics of the orebody. For this style of mineralisation, an empirical approach to define ore characteristics is recommended.CITATION:Dominy, S C and Minnitt, R C A, 2012. Application of heterogeneity testing to coarse gold ores, in Proceedings Sampling 2012 , pp 143-160 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 21, 2012

The mining industry, both here and internationally, is continually developing increasingly sophisticated software to compute mineral resource estimates, but these processes cannot compensate for a flawed geological interpretation of the geology of the economic commodity(s) concentrations. Quality assurance and quality control (QA/QC) is becoming increasingly common in association with the sampling and assaying practices within the industry. However, it is rare in the case of a geological interpretation associated with mineral resource estimation. Why? In the context of this paper, QA/QC relates to the use of statistical and graphical tools to show that the geological economic commodity concentrations have been appropriately domained. Domaining is essential to improve the chance of getting a mineral resource estimate right. Commodity value and acceptable concentration variation within a mineral resource can be ingredients that make mineral resource estimation difficult to get right. But it is possible to get it right a very high proportion of the time. It is more likely to occur when inappropriate data consolidation is minimised. In any case, inappropriate data consolidation is significantly reduced when the geological interpretation is strongly consistent with the data and it is demonstrable. To achieve quality global estimates of geological domain concentrations, it is essential that the geology of the prospect is understood sufficiently that the deposit is appropriately domained. Appropriate domaining occurs when sample populations are separated in such a way that only data in harmony with each other within the population contributes to the domainÆs concentration estimate. The paper will use four brief case studies to illustrate how QA/QC can be used to display data and validate the underpinning geological interpretation through its associated domaining to get it right when it comes to a mineral resource estimation.

Jan 1, 2007

This research is about human development and socio-economic progress of the main mining areas of Chile in the period 1990 - 2007, and especially about the positive effects that mining activity has on poverty reduction and indicators related to the Millennium Development Goals of the United Nations. The analysis is doubly interesting, if one considers that the economic and social developments in Chile, recognised and prominent among the Latin American economies and developing nations, are more evident in mining areas as Tarapacß and Antofagasta (northern Chile), which concentrated than more 70 per cent of investments and mining assets in the country. Additionally, the study concludes with methodological reflections for the evaluation of socio-economic impact in the mining industry in developing countries.

Jan 1, 2009

By E N. Sparg, O D. A Deuchar, F Needham

Decline shafts are an attractive option to both new and existing mining operations where there is a need to access an inclined orebody deposit via on-reef development so as to generate a return in the shortest possible time. There are many different technologies that are available to transport men, material and rock in incline shafts. This paper focuses on the applicability of two hoisting technologies for decline shafts, namely endless and direct rope systems. The pros and cons of each system are reviewed. A common concern with direct rope haulage systems is the possibility of generating slack rope during deceleration. This paper illustrates the issues involved in designing a system so as to avoid the possibility of slack rope. In conclusion, the key factors relevant to the selection of endless or direct rope haulages for a particular decline application are reviewed. The paper is a joint submission by FFE Minerals-Vecor and Qualter Hall UK.

Jan 1, 2005

By I Ametov, S Harmer, R Alford

A process that allows selective flotation separation of low Cu/S ratio minerals (chalcopyrite and pyrite) from high Cu/S ratio minerals (bornite and chalcocite) from a mixed copper mineral concentrate under controlled oxidative-reductive potential conditions has been developed. The process has been extensively tested on samples with varying mineralogy using laboratory batch flotation tests and mini pilot plant trials.In this process, the mixed final copper mineral concentrate is purged with nitrogen, and then treated with sodium dithionite to achieve a slurry Eh in the -200 to -100 mV standard hydrogen electrode (SHE) range. Flotation was then carried out using nitrogen gas. As a result, a low Cu/S ratio concentrate (<1.3) and a high Cu/S ratio (>1.6) tailing stream were produced. QEMSCAN analysis of the flotation products showed that more than 85 per cent of the chalcopyrite and 95 per cent of the pyrite reported to the froth concentrate. Chalcocite and bornite were almost evenly distributed between the concentrate and tailing streams.Surface analysis studies, focused on the mechanism of separation, showed that at a negative redox potential xanthate and possibly dixanthogen are the dominant hydrophobic species on the surface of chalcopyrite and pyrite. As a result, the flotation of these minerals remained unaffected. In contrast, a much lower concentration of xanthate species on the surface of chalcocite and bornite particles was observed. Therefore, it is likely that at low Eh the copper xanthate complex desorbs from the chalcocite and bornite surfaces, causing a decrease in surface hydrophobicity and the diminished floatability of chalcocite and bornite.CITATION:Ametov, I, Harmer, S, Grano, S and Alford, R, 2014. Selective flotation of chalcopyrite and pyrite from a mixed copper mineral concentrate under controlled redox potential conditions, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 131–140 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By M Pernechele, U König

Most of the operating steelmaking capacity currently relies on conventional, coal-based steelmaking processes. Currently, direct reduced iron (DRI) is only produced in regions where energy is available at low cost. To align with net-zero emissions goals, steelmaking capacity must transition to loweremissions steelmaking technology. Direct reduction of iron ore will get one of the preferred methods in the future due to its high technology readiness. New reduction technologies include hydrogenbased direct reduction processes. To ensure optimal efficiency during DRI production and to cope with newly developed technologies, processes need to be monitored more frequently and accurate. Traditionally quality control of raw materials and DRI has relied on time consuming physical testing, wet chemistry or the analysis of the elemental composition. The mineralogy of DRI that defines its properties is not frequently monitored. Process monitoring and quality control of DRI is possible by using modern X-ray diffraction (XRD) methods. In addition to the metallic iron content (Femet), metallisation (Metn) and the total carbon content (Ctot), XRD analysis also identifies the overall mineralogical phase composition. This allows additional information about the reduction process and enables fast counteractions on changing raw material mixtures. The benefits of the quantitative determination of the phase composition and the calculation of process critical parameters to produce DRI will be demonstrated with a case study

Sep 18, 2023

In February 1995, Falconbridge Limited approved the construction of a nickel mining and milling facility on its Raglan property situated in the Nunavik region of northern Quebec, Canada. The construction period successfully terminated with the commissioning and start-up of the plant and concentrator in early-December 1997. The estimated life of the project is 20 years with an annual mining rate of 800 000 tonnes of ore, producing 21 000 tonnes of nickel per year. This paper discusses the subject of æRemote Mining in the Canadian ArcticÆ as it applies to the Raglan mine process and people. During the feasibility stage of the project, many assumptions were made which influenced the design and operating parameters of the facilities and the equipment. Transportation, communication, remote logistics techniques and standard industry practices required to support a æfly-in/fly-outÆ operation were reviewed and either adopted or rejected for use at Raglan. These assumptions were æmade to fitÆ the uniqueness of our planned operation. It was also acknowledged that many of them would ultimately impact on the people required to staff the operation following construction. Therefore, their suitability and applicability were examined from an economic, operational and human perspective. In a continuing effort to improve the quality of life for Raglan employees, as well as the economics of our mine operations, these assumptions are under constant review and scrutiny. There is no doubt that experiences gained, and willingly shared by other North American arctic mining operations, proved invaluable and are a big reason for RaglanÆs overall success thus far. The mining industry is being challenged technically to develop lower grade orebodies at the lowest possible cost. In addition to environmental constraints, serious social, political and moral questions are being asked and added to this list of challenges. Miners throughout the world must improve their operating standards and public image if we want to attract the best possible employees. Remote mining operations provide a unique opportunity to experiment with various human resource concepts as well as demonstrate the industryÆs commitment to environmental and community concerns.

Jan 1, 1998

By M I. Pownceby, S Hapugoda, H Han, E Donskoi, L Lu

Iron ore sinter mineralogy and its associated macro-/micro – structure has a strong impact on sinter quality. At a macroscopic scale, sinter ideally consists of a strong, porous matrix which bonds relict ore nuclei together. Microscopically, the sinter matrix (solidified from the melt part of the initial sinter mix) generally consists of complex calcium ferrites known as SFCA, secondary magnetite and hematite grains (precipitated from the primary sinter melt), glass and silicates. Depending on the conditions under which the sinter structure is formed, two major forms of SFCA with different morphologies are generally recognised, ie fine micro-platy SFCA (usually termed SFCA-I) and coarse columnar/prismatic SFCA. Detailed optical microscope observations of several pot grate and compact sinter samples revealed the presence of a variety of fine, coarse and dense forms of both types of SFCA. The controlled cooling tests revealed that cooling rate has an impact on the form and size of SFCA crystals. In this work, EPMA analysis of SFCA compositions from a variety of pot grate and compact sinter samples are presented. Results show that the SFCA types exhibit a broad range of complex compositions within the system Fe2O3/CaO/SiO2/Al2O3/MgO/TiO2/MnO2. Although SFCA-I and SFCA are known to be crystallographically distinct and with different, well-defined ranges in composition, there was considerable overlap in compositions of the experimental sinter samples. The development of SFCA textures depend on several parameters including the local chemistry and conditions including the maximum temperature attained and the cooling rate, within the sinter bed, thereby suggesting that SFCA identification based on morphology alone may be erroneous.

Nov 8, 2021

By K McSweeney, A Marton

This paper discusses the development of a strategy for ensuring long-term geotechnical stability of final pit walls at AngloGold AustraliaÆs Sunrise Dam Gold Mine. The strategy makes use of improved blasting techniques, changes to the mining sequence and other geotechnical techniques. Only the blasting techniques will be discussed in this paper. These were developed from numerous trials over a period of several months from May 2003 through to November 2003. The focus was to reduce crest loss damage and thereby improve final wall integrity, maintain designed safe berm widths, and ensure long-term stability. Crest loss mechanisms are now understood and are explained in this paper. The preferred solution is outlined; which is a combination of improved blasting and changes in the mining sequence to cater for pre-existing ground conditions. These ground conditions include dynamic hyper saline water with sometimes intersecting steeply dipping discrete structures. Project requirements were defined as mitigating or eliminating crest loss using 127 mm diameter pre-splitting and targeting minimal production blasting vibration levels against the walls. Blast results were measured by post blast visual inspections and video. Blast design input utilised the predictive algorithms built into simulation software when attempting to minimise vibration levels against the walls. Protection of the already fired pre-split line is now achieved using small charges against the wall and timing sequences which form a mask for the later firing main charges. The pre-split spacing is now modified to suit the geology. There eight blast domains identified around the perimeter of the pit, each having varying joint orientation. In addition, blasting the bench adjacent to the berm crest has particular considerations not required by the middle and lower benches. The preferred solution was to purposefully translate this damaged top section of the pre-split bench into a planned subsequent dig zone. The design of this top æweightÆ is a direct response to the nature of the crest loss mechanism.

Jan 1, 2004

By I D. Gregson, A Gandhe, A S. Garcia, K M. MacAndrew

"Falls of ground still cause around one-third of all underground mining fatalities. The recent introduction of mechanised room and pillar working into Indian coalmines is an example of the application of new design by measurement and safety monitoring strategies, which can be used to reduce falls of ground risks in mines.Rock Mechanics Technology, now part of Golder Associates UK Ltd (Golder), is providing rock bolt support and pillar design services to the mines using a design by measurement approach. This involves in situ monitoring to confirm support and pillar designs and pillar extraction sequences.Site examples are given of the support designs determined and the monitoring programs undertaken for both design and safety.Routine safety monitoring of roof movement using telltales is also described. A new auto warning telltale has been developed specifically to warn of imminent caving as pillars are extracted.The approach used by Golder has played a major role in ensuring the success of these projects. As a consequence, mechanised room and pillar working is now firmly established in India, and wider application is planned to help meet future demand for coal.The experience confirms that the design by measurement method for this application has important advantages over conventional design approaches using analytical or empirical methods. Firstly, it measures the design performance or outcome rather than trying to calculate or predict it. Secondly, it provides the opportunity for the design to be adjusted to obtain the optimum outcome. Thirdly, it can do this at a local level, so that the support design can be matched to changing conditions to give the most cost-effective design. Finally, it incorporates long-term monitoring of support performance, again at a local level, so that subsequent change can be identified to enable corrective measures to be implemented in a timely manner and to ensure that ground control safety is maintained.CITATION:MacAndrew, K M, Garcia, A S, Gregson, I D and Gandhe, A, 2014. Application of design by measurement for support and pillar design in mechanised room and pillar coal mining in India, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference, pp 65–76 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 5, 2014

By J Andrina, D Richar, R Smart, A Neale

The Grasberg is a large copper and gold open pit mine operated by PT Freeport Indonesia and located in the high equatorial mountains of Papua Province, Indonesia. The climate is alpine/sub-alpine with little seasonal variation in temperature and rainfall. The annual precipitation varies from about 3000 to 5000 mm over short distances around the Grasberg, but in general, an average daily precipitation of 10 mm per day applies and leaching of the overburden is continuous throughout the year. Mining commenced in 1988, and almost all of the overburden mined up to 2003 was potentially acid forming. From 2003 to the end of the Grasberg pit operation in 2014, approximately 70 per cent of the overburden will be potentially acid forming and 30 per cent limestone. A major focus of the investigations is developing strategies to maximise the beneficial use of the limestone that will be mined. Laboratory columns and field test pad investigations have been ongoing for six years examining limestone blends. Trial dumps utilising truck placement and conveyor/stacker placement and blending of limestone and acid generating rock have recently been constructed. In addition, based on initial results, investigations aimed at further evaluating the performance of limestone covers in this high rainfall environment have commenced. A significant finding has been the identification of strong armouring layers on sulfide surfaces within well-blended material and under limestone covers. These layers effectively isolate sulfides and thus progressively slow the oxidation rate to a level where the alkalinity load from the limestone exceeds the rate of acid generating. ARD is controlled and neutral low metal drainage results. The results have demonstrated that although limestone blending is effective, it is necessary to ensure that all size fractions within the blend receive adequate acid neutralising capacity to buffer the potential acidity. Because the sulfur content generally increases and the acid neutralising capacity decreases with decreasing particle size in limestone blends, the amount of limestone required greatly exceeds the stoichiometric requirement. This paper describes the development of limestone blending specifications for potentially acid forming overburden and presents the results of the ongoing limestone cover trials at the Grasberg mine.

Jan 1, 2003

By D Craw, P V. Angus

Gold mineralisation at Macraes occurs as late quartz-carbonate veins within a body of sheared and hydrothermally altered Otago Schist, the Intrashear Schist. The alteration is characterised by the presence of rutile and the absence of epidote and titanite, indicative of an alteration fluid containing >10 mol per cent CO2. In areas of high strain, a fabric of black microshears develops, gradational to mylonitic cataclasite in the high strain zone adjacent to the hanging wall of the duplex shear zone. The microshears contain hydrothermal graphite, inferred to have been deposited from a methane-rich fluid. The mylonitic cataclasite is characterised by abundant pyrite, the absence of albite and extreme grain size reduction. Gold recovery in the CIL processing plant at Macraes can drop to 50 per cent or lower for some unfavourable ore types. Preg-robbing by a component in the ore, possibly graphite, was suspected as the cause. Mylonitic cataclasite was identified as the lithology responsible for the poor recoveries, with the capacity to bind about 30 ppm of gold in the leach tanks. A program of detailed geochemistry and quantitative grain-size measurement using Coulter analysis was undertaken to identify specific mineralogical factors associated with preg-robbing. The results indicate that pyrite, graphite, and extreme grain-size reduction are the factors associated with highly preg-robbing ores at Macraes. The evolution of the mylonitic cataclasite is accompanied by strong potassium enrichment, as muscovite, and depletion in sodium as albite is removed. This suggests that a simple powder XRD ratio of the albite to illite peaks would suffice to distinguish the preg-robbing ore for grade-control purposes.

Jan 1, 1999