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By A Grace, C Sennersten, A Davie, R Lyu, C A. Lindley, O Goldstein, T Thomas, L De Macedo Camargo

Block modelling is a well-established method for modelling ore reserves as a basis for strategic mine planning and mine development. Off-Earth mining, particularly of asteroids, can benefit from block models; however, the significantly different characteristics of asteroids and their methods of mining require reconsideration of the geometry and annotations of block models. Terrestrial block models consist of rectangular prisms within Euclidean coordinate systems. Their labels and parameters typically include location within a mine-specific coordinate system, x, y and z dimensions, specific gravity, hardness, grades of metals of interest and so on.These data provide an input to mine design and strategic mine planning. Mining asteroids may require different coordinate systems (eg spherical, elliptical or cylindrical, rather that Euclidean) and attributes that vary from Earth-based block models. These include: variable gravitational vectors throughout the block modelrotational moment or accelerationrotation rates. Materials within asteroids may show different isotopic compositions. Asteroid mining has the unique characteristic of a mine being identical with an asteroid. The position of the asteroid/mine in space and its full orbital elements provide critical inputs to mission design and costing. Hence, the block model concept needs to be extended with this metadata. The orbital position and behaviour of the Earth must be included for active mine planning, and increasing automation of mine planning and operations needs to consider terrestrial weather and telecommunications infrastructure. Financial planning requires analysis of the net present value of extraterrestrial mining compared with terrestrial alternatives, so a fully automated mining enterprise should integrate terrestrial and extraterrestrial block models at different scales and resolutions. Blocks can be indexed via octrees, allowing for hierarchical scales that support analytics for deriving new knowledge and correlating features across different scales.CITATION:Lindley, C A, Sennersten, C, Davie, A, Goldstein, O, Lyu, R, Grace, A, Evans, B, Pentecost, D, Thomas, T, De Macedo Camargo, L, Craig, J, Salomao, G N, Hellicar, A, Biggins, D, Timms, G, Coombe, M, Shahriar, M S, Smith, G and Rahman, A, 2015. A multilayer 3D index tool for recursive block models supporting terrestrial and extraterrestrial mine planning, in Proceedings Third International Future Mining Conference, pp 289–296 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

The Savage River open cut magnetite mine is located in rugged terrain in densely rain forested northwest Tasmania. The mine and concentrating plant are both in the Savage River valley. Pickand Mather Incorporated (PMI) operated Savage River as an open cut magnetite mine between 1966 and 1996. Acid rock drainage (ARD) was first noted in the last ten years of the operation, leading to elevated concentrations of heavy metals downstream of the mine. When operations ceased in 1996, PMI returned the mine to the Tasmanian Government along with a remediation fund of $11.4 million. At that time, the assessed cost of remediation was in excess of $120 million. As a result of the ongoing ARD contamination and to facilitate both a new operation and effective remediation, Goldamere Pty Ltd negotiated an agreement with the Tasmanian Government in 1996, which resulted in the Goldamere Act and the Goldamere Agreement. The agreement has allowed Australian Bulk Minerals (ABM) to remediate the Savage River mine in conjunction with the Tasmanian Government while re-invigorating a previously closed mine by providing ABM with an indemnity against past pollution. ABM can configure its mine and waste planning activities to maximise remediation benefits without fear of future litigation for past mistakes. The effect to date has been the development of a long-term strategy to remediate the Savage River and short-term remediation works such as water management, which provide benefits to the ecosystem. After five years, the Savage River is no longer significantly impacted by ARD for 30 kilometres downstream and trout are now reported within the reaches of the mining lease. The arrangements between ABM and the Tasmanian Government are an example of a genuine WIN WIN situation where co-operative environmental management of the site results in significant improvements and where the æregulatorÆ and the æminerÆ are working together to achieve mutually beneficial goals. The end result is a significant benefit to Tasmania.

Jan 1, 2003

By J Tibbett, F T. Suorineni, B Hebblewhite

Block caving is an important mining method for the future economic exploitation of large, low-grade, steeply dipping orebodies. While block caving is not a new method, there are still many unknowns surrounding the mechanics driving the process, particularly as we are forced into deeper, higher-stressed and stronger ore deposits. The caving industry is desperate to provide some explanation behind the myths of caving geomechanics to better predict and manage current caves and caves of the future. Large amounts of data are collected to help understand caving, but it is not fully utilised and current approaches for analysing the data are capacity limited. The application of virtual reality and scientific visualisation (VRSV) technology to visualise and analyse block caving is a critical future component in the assessment toolbox. VRSV enables large, complex, multidimensional data sets to be analysed and the power of human visual problem solving processes to be utilised. Block caving is a complex system and needs to be analysed as a system, rather than looking at individual factors one at a time. A software module has been developed at UNSW Australia for use in the advanced visualisation interactive environment for analysis of the block cave mining system (BCMS). This fully immersive, 3D virtual assessment tool shows exciting potential and is used to analyse the BCMS with a close linkage to time (ie the chronological occurrence of data). This tool will enable a true investigation into the cause and effect relations within the BCMS. Current research is investigating Newcrest Mining Limited’s Ridgeway Deeps operation and is aiming to turn some of the cause/effect relationships into increased geomechanics understanding to provide improvements to ground control management. This paper outlines the methods of assessment used to analyse BCMS geomechanics with VRSV and shows the potential of the software module for BCMS analysis.CITATION:Tibbett, J, Suorineni, F T and Hebblewhite, B, 2014. The application of virtual reality technology and scientific visualisation to the understanding of block cave mining systems, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 195–200 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

An intensive safety campaign at Mount Isa Mines Limited from 1956 to 1966 saw the lost time accident frequency rate fall to half its original level. A review of the safety programme was carried out in 1967 and in 1968 the Five Point Safety System was introduced. The seven years since its introduction have been years of significant achievement both in production and safety. Improving safety is a fundamental part of Mount Isa Mines Limited's policy and this system has been a major tool in implementing that policy. To be successful personnel need to be prepared and trained for its introduction and subsequently counselled on its use. A carefully prepared programme is required to phase in various aspects of the system and to make use of complementary steps. The system has been a success and it is anticipated that the continued drive to improve the use of principles of the system will further improve safety. It is hoped that this paper will be of value to those personnel concerned with industrial safety in Australia.

Jan 1, 1975

The homologous series of saturated fatty acids investigated in this study generally show a steady gradation of properties with chain length. The solution pKa values were assumed constant at 4.9, however reported pKa values could be lower or higher. Hematite flotation response and surface pressure for aqueous solutions of these fatty acids were measured as a function of pH. For the shorter chain fatty acids, the undissociated acid was shown to be the predominant surface active species with flotation, supplemented by the physical adsorption of acid anions as the chain length increased. The reduced solubility of the longer fatty acid carbon chains made these reagents ineffective as flotation agents. The maximum flotation response of hematite using tetradecanoic acid corresponded with the precipitation edge of the reagent. The results show that the values of surface pressure of the surfactants are not always a good indication of their effectiveness as flotation collectors.

Jan 1, 2005

Since the early 1990s it has been evident that electricity demand has outstripped investment in generation and transmission. At the same time, concerns were being expressed about the risks associated with the run down of the Maui gas field. It is axiomatic that the necessary investments firstly require a stable and supportive regulatory and fiscal environment, and secondly that such investments have long lead times. A unwillingness by successive Governments to fund the necessary infrastructure, however, lead to the profound restructuring of the electricity with the ultimate objective of transferring the investment risk from Government to the private sector. Successive power crises since 1992 result from a failure to put in place a regulatory framework necessary to provide the environment to allow the private sector to make the needed investments within the necessary timeframe. The electricity sector has now stabilised to the extent that the regulatory risks associated with generation investment have been reduced. This does not mean that risk has been eliminated, however, and both economic and environmental issues will continue to constrain investment in some power proposals particularly those in the South Island and especially any South Island coal or gas thermal proposal. This is firstly because of several very simple economic issues:  1. while the South Island may have significant coal resources it lacks a significant electricity market; 2. except for a six to ten week period in a dry year, low cost hydro will price any large-scale South Island thermal out of the market which will restrict any large scale thermal station to a dry year and/or peaking load; 3. except for a six to ten week period in a dry year, export capacity on the HVDC link to the North Island is constrained to around 964 MWe (and 482 MWe from North to South in dry years); and 4. construction of any new thermal plant in the northern half of the North Island will price any South Island thermal station out of the market. There are also significant environmental issues associated with the establishment of a large scale thermally based power station in the South Island. Because the South Island lacks any large scale economically proven gas reserves, the environmental constraints considered are those associated with coal production. A coal mine dedicated to power generation will have significant on-site impacts associated, in particular those associated with disposal of opencast overburden and visual impacts. These will, however, be partially offset by the relative remoteness of such sites to population centres. What cannot be offset, however, is the off-site impacts, in particular, CO2, SOx and NOx emissions, water disposal and acid mine drainage.

Jan 1, 2003

By Minchinton A

CPeX is a non-ideal explosive performance prediction model. The model takes into account the rate of energy release, the extent of chemical reac- tion and the effect of confinement on energy release. The model resolves the explosive energy into `shock' and `heave' com- ponents as a function of explosive type, hole diameter and rock type. The predictions of the model are compared for a bulk emulsion, and a prill-doped bulk emulsion in soft rock. The predictions, based on calibra- tion of the model with simple unconfined detonation velocity measure- ments, show the significant effect of non-ideality on explosive Performance.

Jan 1, 1988

The Beverley uranium mine û now in production in the remote north of South Australia at1000 tonnes per annum û was established to meet a projected, but little-recognised shortfallin primary supply of uranium for the nuclear industry in the early part of the 21 st century. Inthe context of AustraliaÆs lack of bi-partisan support for uranium mining and the nuclearindustry, a four to five year window of opportunity existed from 1996 to establish the mine.During this period, Beverley achieved a number of firsts including: the first ISL mine inAustralia; the largest ISL mine in the world and the first to produce more than 500 tonnes ofuranium in its first year; the first to be established under a new Native Title regime in SouthAustralia; and the first to be established under a revised South Australian Mining Act.Beverley was brought into production against the background of: hostile opposition fromanti-nuclear activists; a suspicious and at-times hostile media; a regulatory and politicalcommunity that was unfamiliar with ISL mining; commercially unsophisticated Aboriginalgroups; an inexperienced engineering industry; and the vagaries of development in a remote,semi-arid location with neither population nor infrastructure. The lessons that can be learnedfrom Beverley showed that û like much in life û flexibility and timing are crucial.

Jan 1, 2002

By K J ROSENGREN

Underground rock mechanics was initiated as a formal discipline in Australia by early studies for underground structures for the Snowy Mountains Scheme in the 1950s. These techniques were quickly embraced by underground mining and there has been steady development to the present time. The paper reviews the status of current techniques for rock mechanics studies and discusses some important issues such as ground support, mine filling and caving. It concludes that a considerable degree of engineering judgement is still required for the practical application of rock mechanics to underground mine design.

Jan 1, 1992

Before commencing design of a coal prepar ation plant, it is essential to have detailed information of the raw coal to be treated to- gether with a clear understanding of the products required. Prediction of raw coal size distribution, particularly the amount of fine material, is difficult and the methods employed should be large scale pilot plant studies or techniques to simulate coal degradation and shale breakdown in water. A detailed knowledge of well proven coal preparation processes and new developments allows processes and process combinations to be compared to'obtain the maximum economic recovery when using lower cost, less efficient processes within acceptable limits. Equipment should be selected bearing in mind its precise application and the location where it is installed. Plant layout should be carefully studied to minimise equipment requirements and to simplify construction. Measurement, control and automation should be an integral part of plant design in order to obtain the optimum performance of the processing equipment.

Jan 1, 1974

By J Heyes, T Cooper, M Stimpfl, R Staines, J P. Pearce

Acid and Metalliferous Drainage (AMD) is one of the key risks facing the mining industry worldwide. If not properly managed and/or not identified in a timely manner, AMD has the potential to decrease environmental values for generations to come. Ore extraction generates vast volumes of mineral waste (waste rock and tailings) which are stored in perpetuity at the mine site. Some of these materials are not inert and when in contact with air and water can react, generating poor quality water and compromising operational and closure environmental objectives. Understanding the geochemical behaviour of waste rock and tailings is therefore key to identifying risks and opportunities which support effective mineral waste management strategies across the mining value chain and progress toward an environmentally sustainable future that minimises closure liabilities. To ensure AMD risk is recognised and managed uniformly across its portfolio, BHP developed a Global AMD Management Standard for implementation across all operations, including closed sites. The AMD Management Standard provides a management framework to support the consistent, simple and sustainable global management of AMD risks. This ensures mines are planned and operated to be environmentally smart and modern, geochemical risk management is not an afterthought but a key driver, and environmental sustainability is actively pursued to reduce closure liabilities. The AMD Management Framework, on which the Standard is based, was adapted from industry leading practice guidance, ensuring it applies to multiple regions. The framework also comprises sequential requirements throughout the mining life-cycle. It is an iterative framework with an adaptive management approach that is designed to incorporate new data, information and management opportunities into AMD risk assessments and mine plan revisions.

Jul 1, 2021

Most mineral products exported from Australia to Japan, with the notable exception of coal, are purchased with weight and quality determined on discharge. Sampling of imported minerals for purpose of payment is done at facilities owned and operated by the purchaser. The selling shipper is represented at the weighing, sampling and testing by an independent inspection group who supervises the whole procedure. Sampling and testing are done within the provisions of the contract between the two parties, and normally in accordance with the relevant Japanese Industrial Standards (JIS). These JIS specify such things as the number and mass of increments to be taken; the practice of taking these increments; the method of determination of moisture, size distribution and quality. The JIS concerned with sampling however, are meant to be basic guides rather than rigid rules. Hence sampling and testing practice varies from plant to plant. In general Japanese sampling facilities and methods are elaborate and efficient. Opportunity is given for the discussion of varying technical viewpoints between consumer and shipper. However the resolution of differences and the implementation of changes normally takes a long time. Such discussions seem best reduced by prior contract agreement on reasonable specifications and detailed testing methods. The independent inspectors

Jan 1, 1976

EnergyAustralia is a state-owned corporation in the state of New South Wales, whose responsibility includes ownership and management of an electricity distribution network. Expansion of the high voltage distribution network in the Sydney central business district (CBD) includes the requirement to run an additional five 132 kV feeders over 1.7 km from south of the CBD to a new 132 kV substation in the northern section of the CBD. A driven tunnel is currently being excavated in Sydney sandstone beneath Darling Harbour to contain the new 132 kV feeders. Tunnel construction methods involve both roadheader and tunnel boring machine (TBM) excavation. This paper describes the design development of the cable tunnel, discusses the use of a geotechnical baseline report as an integral part of the contract documentation and provides an update of the current construction works.  

Jan 1, 2008

By B J. Wilde

Evaluating the resources and reserves in a mineral deposit requires many interdependent subjective decisions. The decision of stationarity is arguably the most important. This decision includes: the choice of domains that subset the entire deposit, modelling the boundaries of each domain, and understanding and considering the nature of the contacts between domains. Reasonable choices are made in consideration of the geological context, the available data, the goals of the study and the available resources for the study. This paper reviews aspects of the decision of stationarity in modern resource assessment with a focus on quantifying uncertainty and using numerical/statistical tools to help the geomodeller. The use of volume/distance functions to quantify uncertainty in domain limits is particularly important and is presented in detail. The use of contact plots provides help with the continuity of grades across domain boundaries. Realisations are not assembled as a branching combinatorial of all possibilities, but as a set of realisations that provide a measure of uncertainty. This paper amounts to a definition of stationarity for modern resource assessment.

Sep 26, 2011

By P Moser, P Schimek, F Ouchterlony

This paper summarises the findings of 27 model-scale bench blasts in magnetic mortar, which were conducted from 2011 to 2014 at the blasting site of the Montanuniversitaet Leoben.The aim of the study was the investigation of the influence of blasthole delay times in small-scale bench blasts on the face characteristics and cracking damage created in the surrounding rock, which affects the fragmentation in subsequent rows.The test specimens or blocks, which were produced out of magnetite concrete, were roughly 1:100 in scale to normal bench blasts. The confinement of the testing blocks at the sides and back ensured the similarity to normal bench blasts with regard to the wave transmission into the surrounding rock. The specimen contained three or four rows with five blastholes each and were shot row by row, with virgin (undamaged) material in row 1 and increasingly damaged or preconditioned material in the following rows.The tested delay times varied between 0, 28, 73 and 140 µs, which corresponds to 0, 0.4, 1.0 and 2.0 ms/m of burden.The evaluation of the material properties showed that the use of magnetite concrete eliminated the inhomogeneous behaviour of rock, but some unexpected differences of the individual production cycles were still detected.The characteristics of the bench after each blast was evaluated along three horizontal lines out of a 3D model of the bench face. The tested delay time sequences of the virgin (first row) and single preconditioned blasts (second row) produced more overbreak for longer delays, while the third-row shots resulted in a smoothened surface independent of the chosen delay.The introduced damage after every blast was evaluated by an observation of irregularities on the newly blasted bench face. The visible cracks at the top of the testing blocks were documented and divided into several crack families according to their angle, length and origin. The remaining block was broken out of the blasting site after blasting, cut into several horizontal and vertical slices and dye penetrant spray was used to visualise the cracks created. Some of the detected crack families showed an influence of the delay time. The calculated mean crack density and mean crack intersection density showed that longer delays resulted in a higher degree of damage.The fragmentation results were well reproduced by the basic three-parameter Swebrec function. The observed improvement of fragmentation in the second- and third-row blasts was linked to the preconditioning of the burden for the following row while blasting the actual row. With the exception of the simultaneously initiated blastholes, the blasts showed coarser fragmentation for the shortest delays, while the longest delays generated the finest fragmentation.CITATION:Schimek, P, Ouchterlony, F and Moser, P, 2015. Influence of blasthole delay times on fragmentation as well as characteristics of and blast damage behind a remaining bench face through model-scale blasting, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 257–266 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By T D. H McGrath, O Baker, W P. Staunton, C Ypelaan

"The carbon-in-pulp process has been used extensively in the gold industry since the late 1970s to recovery leached gold from solution. Despite more than 30 years of experience in operating carbon circuits, average gold solution loss has remained at an average of 0.02–0.03 ppm (mg/L), higher than the ‘best practice’ target of 0.01 ppm.Process modelling, such as SIMCIL developed by the Curtin Gold Technology Group (GTG), can provide information on optimum set points; however, manual control of the circuit limits the potential benefits.An automated carbon measurement device, the Scout Carbon Meter, has been developed to allow for automation of carbon concentration measurement, and automated control of the carbon transfer pumps. This paper describes the results from the evaluation of the first two prototypes of the meter.Citation:Staunton, W P, McGrath, T D H, Ypelaan, C, Baker, O and Eksteen, J J, 2016. Optimising Carbon Management - Increasing Gold Recovery and Decreasing Costs with the Carbon Scout, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 225–228 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By P B. Hills

This paper discusses the computerisation of the drill hole database, some historical records and the creation of a three-dimensional model of the gold bearing structures for resource estimation and mine design at the Beaconsfield Gold Mine in northern Tasmania. The phase of the work reported here commenced in November 1997 and was completed in March 1998. The historical mining on the Tasmania Reef had reached a depth of 450 m below surface when work ceased in 1914. Production up to this time was 854 000 ounces gold. Recent activity has concentrated on testing depth extensions of the previously mined ore structure, to a depth of 1000 m below surface, and the establishment of an underground mining operation to exploit this resource. The lode structure at Beaconsfield is a typical mesothermal vein style deposit. Gold is contained within narrow quartz, carbonate and minor sulphide reefs or veins. Reef width is variable from a few centimetres to several metres with æsplitsÆ or bifurcations being common. The reef averages 2.7 m true width in the economic zones. The key feature of this style of mineralisation is that reef continuity can be confirmed by drilling to a high level of confidence, but the gold grades are somewhat more erratic in nature. The resource estimates were based entirely on drill data. The drill intercepts on the reef were coded for each split directly into a database and these allocations validated graphically. The distribution of grades and widths show an increasing gold grade with reef width for both the drill hole and historical data. The same histogram patterns, mixed populations and overall arithmetic average grade for the historical mine (at 21.52 g/t > 3 g/t Au) and new drill data (at 21.55 g/t > 3 g/t Au) would indicate that there has been no major change in the overall style or grade of the ore from the historically mined areas to the new resource. The reef, host geology, area of historical workings and resource zones at the Beaconsfield Mine were defined as a series of closed wireframes. The Tasmania Reef was modelled as five mutually exclusive wireframes, one each for the Main Reef, Footwall split, Second footwall split, Third footwall split and Hangingwall split. The data for this exercise was extracted directly from the drill hole database, stored in Microsoft Access format. The formation of the solids was largely automated with manual validation and refinements allowing for multiple runs using different interpolation methods and combinations of drill holes. A rotated 3D-block model in the plane of the Tasmania Reef was created to contain the grade model and allow for tonnage, grade and reef width estimates. An inverse distance squared (ID2) interpolation method was used with ranges of 25 m along strike and 125 m down plunge with blank areas infilled with 50 m by 250 m. Each reef split was filled separately using only drill intercepts from that split. The method was independently validated used MIK methods. Longitudinal sections have been prepared showing gold grade, reef width and width +grade. Estimates were also made for arsenic, sulphur and other minor elements. The long sections show three distinct mining zones. A method is presented for the conversion of the resources to reserves by the addition of mining parameters for minimum mining width, minimum pillar, cut-off grade and internal and external dilution. The selection is done on columns within the block model, and allows for all splits to be considered at once. Multiple runs can be made for varying combinations of parameters to test different mining methods and their impact on reserves, mine life and NPV.

Jan 1, 1999

By Davies H, Pigram C, Sunata W, Falvey D, Loxton C, Giddings J, Rogerson R

PALAEOMAGNETIC CONSTRAINTS ON TERRANE TECTONICS IN NEW GUINEA Chris Klootwijkl), John Giddingsl), Wahyu Sunata2), Chris Pigraml), Charles Loxton3), Hugh Daviesl), Rick Rogerson3) and David Falveyl) 1) Bureau of Mineral Resources, Canberra, Australia 2) Geological Research and Development Centre, Bandung, Indonesia 3) Geological Survey of Papua New Guinea, Port Moresby, Papua New Guinea

Jan 1, 1987

By M, C A. RosiFre, R C. Figueiredo e Silva

Jaspilites and underlying basalt contacts of the Archaean volcano- sedimentary Grpo Parß Group, Carajßs, host giant iron mineralisation in the ~100-km long, E-W trending Carajßs fold. Preliminary, unpublished geochronological data point to a Palaeoproterozoic mineralisation event. Geochemically, jaspilites are typical volcanogenic banded iron formations. Basalts exhibit evidence of spilitic seawater interaction. Iron-associated hydrothermal alteration of mafic rocks was induced by fluid infiltration in amygdales, with development of chlorite- and hematite-dominated zones. In the case of jaspilites, iron mineralisation encompasses: partial replacement of jaspilitic microcrystalline hematite by blasts of martitic magnetite; jasper recrystallisation, producing fine-grained, hematite-free granoblastic quartz; martite recrystallisation, forming lobate¦subhedral hematite; pervasive porosity development by quartz-chert leaching; incipient cavity filling by microlamellar hematite; and advanced filling by coarser, euhedral and comb-textured, tabular- shaped hematite.Peak hydrothermal ore textures indicate typical epithermal-crust conditions, supported by preliminary fluid-inclusion calculations at 160 - 200¦C. Such temperatures and extreme fluid-to-rock ratios during alteration must have exceeded the ambient metamorphic conditions, with the infiltrating fluid relatively hot and capable of leaching SiO2. Therefore, mineralisation developed over exhumed, Archaean, brittly deformed rocks, with mineral associations representative of very low- to low-grade metamorphism. Considering that chlorite (¦talc) abounds in mafic rocks; hydrothermal albite is developed; dolomite fills veins and vugs; the typical rare-earth-element (REE) pattern of jaspilites is significantly modified in higher-grade hard hematite ores (higher LREE); pyrite, copper sulfide minerals and rare gold occur in association with carbonate-quartz-rich alteration zones, it is suggested that an alkaline, H2O-Fe-CO2 mineralising fluid dominated, also containing species like S¦Cu¦Au. Peak-mineralising conditions are likely to have resulted from a single, evolving fluid, via incipient- through advanced-stage alteration phases. The porous, high-grade soft hematite-type ore (SH), rich in microlamellar and anhedral hematite, must have derived from interaction with this relatively hot SiO2-leaching fluid, whereas the high-grade massive hard hematite-type ore (MH) developed due to closer fluid-rock temperature equilibrium conditions, attained by mineral reactions, with relative increase in the Fe/Σcations ratios allowing the precipitation of subhedral-tabular hematite that partially cements the soft-hematite ore. SH and MH hematite ore types must thus reflect intermediate and high fluid:rock ratios, respectively. Since the N5 deposit is to date understood to contain the largest amount of the MH ore, its units are interpreted as the loci of the highest fluid:rock ratios in the district. Preliminary mineralogical information regarding the S11 deposit of the Serra Sul (south range) implies higher-temperature conditions. The near-equant grain size and the granoblastic intergrain relationship, coupled with the presence of riebeckite, augitic pyroxene and garnet, suggest hornfels textures. The data collected, though still relatively sparse, permit the speculation that the immense driving force for the Carajßs world-class iron deposits was a relatively shallow, igneous-related hydrothermal system. If such a model is correct, then the Carajßs Palaeoproterozoic iron deposits could represent an end-member of the iron oxide-copper-gold hydrothermal system in the province.

Jan 1, 2005

By B C. Povey

HPGR technology has been used at a number of magnetite mines in the world and have significant energy advantages over SAG and AG technologies. The early design at Los Colorados in Chile has been in operation for more than 12 years - and operates very successfully though only reduces the feed size to -5mmThe Whyalla project magnet design pushed the concept to produce a preconcentrate of 80%-350micron - a significant reduction on previous plants though with some wear problems in the early years. The Karara design backpedalled slightly and will only crush to 80%-1.8mm.However, the design issues of using a HPGR to further reduce the feed size continue to be explored. The aim is to reduce the process risks associated with wear and also to reduce the complexity of the downstream process - with consequent benefits in terms of capital and operating costs.The designs are being developed for a couple of projects - one planned to produce 20Mtpa of concentrate with the potential to not only remove SAG and AG milling but also ball milling. The concept is to use multiple passing through the HPGR since, on the data available, the efficiency of the HPGR to reduce size does not significantly diminish as the feed size is reduce. This can be have benefits in both capital and operating cost.CITATION:Povey, B C, 2013. Pushing the use of high pressure grinding rolls in magnetite circuits, in Proceedings MetPlant 2013 , pp 176-189 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013