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By P G. Gaylard

P754 has been an unusual project in that its main aim was to develop a code of practice for metal accounting with the following key objectives:Development leading to an agreed industry standard at corporate governance level Significant improvement of the credibility of metal accounting from deposit to saleable product Development of guidelines for data collection, data analysis, reporting and audit A data analysis toolbox which provides go/no go testing for metal balance data Promotion of industry adoption of these guidelines to improve transparency and financial credibility. Over time, these guidelines may evolve into a code and eventually into a standard Develop and train engineers to become expert in metal balancing and reporting. Papers like this one and the workshop which follows this conference are part of promoting the code for adoption by industry. Developing a code of practice has traditionally been the provenance of professional bodies associated with particular industries û often on a voluntary basis. Given todayÆs industry pressures, it was felt that funding key input might accelerate the development process as well as offer opportunities to research some of the problems and to train some post graduate students in a difficult discipline. In fact, the project has brought together six industry sponsors from a wide range of process types, three research providers, and funded students in South Africa and Australia. The project has also attracted input from the financial community. A textbook to support the application of the code has also been written. The industry sponsors have made the Code and Guidelines available on request to help to facilitate its use by the mineral industry beyond the sponsor group. The Code and Guidelines have already been translated into Spanish and Portuguese which suggests that industry acceptance may happen quite quickly. The main thrust of the code is to integrate commercial and technical performance to a much higher degree. The Check in-Check out (CI-CO) method has been chosen as the vehicle for this combined approach. The mass and metal values used for CI-CO are 'absolute' and provide the basis of financial transfers. The CI-CO process occurs at each transfer of custody - whether between divisions within a company, or between companies. This approach means that measurement of mass and metal flows becomes the critical element of the process and that a quantitative knowledge of measurement accuracy and precision is also essential. This knowledge allows technical differentiation between differences which are within the expected margin of variation and those which must be formally identified as discrepancies and subject to a process of investigation and sign off. Hence, the application of the code for most companies should be more evolutionary than revolutionary, but with substantially more emphasis on measurement and definition of measurement error. Where this can be achieved, it should bring the mineral industry more into line with other industries competing for investment funds, community acceptance and future employees.

Jan 1, 2008

The purpose of this work is to determine the equilibrium-state of the aqueous-solution which is produced by the leaching processes, including natural weathering of pyrite minerals. The latter can lead to acid-mine-drainage (AMD). The ferric iron species (Fe3+) resulting from bacteria-catalysed oxidation of ferrous iron (Fe2+), in the presence of water and air, is known to bring about steady-dissolution of minerals chalcopyrite (CuFeS2), sphalerite (ZnS), pyrite (FeS2), and so forth. Good-aeration, relatively high-porosity and sufficient bacterial activity tend to promote leaching in waste-rock-dumps. The composition of the aqueous-phase that accumulates in the pore-space (or in open-pits) is of practical interest as it would strongly influence the leaching of both sulfide and non-sulfide minerals. Since the reactions among the various ionic species occur relatively fast, the solution-phase may be regarded as approaching a state of virtual-equilibrium and it is possible to determine by computation the respective concentrations of the many dissolved species. For the Cu-Fe-H-O-S system, these species may include: H+, Fe2+, Fe3+, Cu2+, HSO4-, SO42-, OH-, CuSO4o, H2O, Fe(OH)+, Fe(OH)2+, Fe(OH)2+, Fe2(OH)24+, Fe(SO4)+, Fe(HSO4)+, Fe(HSO4)2+, and Fe(SO4)2-. The aqueous-system which may be constituted from appropriate mole-quantities of H2SO4, FeSO4, Fe2(SO4)3, and CuSO4 is in fact the result of various natural processes (reactions) and due respect must be accorded to the extents of these reactions. The present model computes the equilibrium molalities of the foregoing ionic and neutral aqueous species, using the iterative equilibrium constant method that ensures strict-adherence to charge-balance and elemental molar-balance constraints. The dissolving sulfide-minerals (FeS2, CuFeS2) consume Fe2(SO4)3, H2O, and O2 and yield FeSO4, H2SO4, and CuSO4 while the aqueous-phase tends to become progressively acidic (declining pH) reflecting the gradual increase in the extents of sulfide-dissolution reactions. The equilibrium-state of the solution-phase is computed for specific set of values for the extents of respective reactions. The temperature and pressure of the system are 25¦ C (298.15 K) and 101.325 kPa (1.0 atm), respectively. The mica-like minerals such as the biotite [H2K(Mg,Fe)3Al(SiO4)3] tend to consume much of the H2SO4(aq), with the extracted K+, Mg2+, Fe2+ and Al3+ ionic species accumulating in the solution. The precipitation of the jarosites (potassium, hydronium, or ammonium) contributes to the removal of ferric and ferrous species from the solution-phase. In the present work, the emphasis is on predicting the compositions of the aqueous- and condensed-phases with advancing time or increasing æextent of reactionÆ. The results of such calculations are compared to published data on raw AMD (acid-mine-drainage).

Jan 1, 2008

By R Williams, P Kohout, J Comins

The Northside Storage Tunnel (NST) is the largest tunnelling project ever undertaken in Sydney. The tunnel extends deep underground from the western bank of the Lane Cove river to the North Head sewage treatment plant (STP), with a branch tunnel from Scotts Creek connecting to the main tunnel under Tunks Park. The aim of the tunnel is to intercept wet weather overflows from four key points along the northernsuburbs ocean outfall sewer (NSOOS) and provide short-term storage and transfer of sewage to NorthHead STP for treatment prior to discharge to the ocean through the deep ocean outfall. The project was an ambitious undertaking by an alliance between the client Sydney WaterCorporationand the engineering firms of Montgomery Watson, Connell Wagner and Transfield to design andconstruct approximately 20 kilometres of tunnel, tunnel declines and shafts in just over three years. In order to achieve this tight timeframe construction of the NST has been undertaken simultaneously at seven construction sites located across the northern suburbs of Sydney. As with most tunnelling operations, tunnel boring machines (TBMÆs) and roadheaders dominated the excavation activities. Tunks Park and North Head STP are the major tunnelling sites. An access decline was excavated using roadheaders at both of these sites to facilitate tunnelling using TBMÆs. Three TBMÆs 3.8 m, 6.0 m and 6.3 m diameter) were launched from Tunks Park and one TBM (6.5 m diameter) was launched from North Head. At the overflow interception sites of Scotts Creek, Lane Cove River and Quakers Hat Bay two vertical shafts known as drop and access/ventilation shafts were constructed. These shafts would provide the linkage between the existing sewer and the tunnel. As their names suggest the drop shaft would convey the wet weather sewage overflows to the tunnel while the access/ventilation shaft would provide access during dry weather and ventilation during a filling event. The fourth overflow site of Tunks Park would use the tunnel decline as its link to the tunnel. Originally these shafts were to be excavated using the raise bore method. This technique however, is entirely dependent on the TBMÆs reaching the shaft locations at the specified time. This was not the case at two of the three shaft excavation locations and top down methods of excavation such as, a percussive cone fracturing (PCF), blind bore, mechanical excavation and drill and blast were investigated to ensure the project met its completion schedule. Traditionally project decisions are dominated by cost and schedule objectives. The contractual arrangement of the Alliance however, required that the objectives of safety, community and environment also be considered in any decision making process. Thus each of these top down methods of excavation were assessed against these five objectives. On considering all of these factors the use of explosives was considered to be the superior technique.

Jan 1, 2001

By G Kuntz, V Wall, B New

The prime aim of the Campbell Mine project was to develop a 3D geological model for the Campbell-Red Lake system to contribute to an exploration model for the region. The base data is composed of over 60 years of geological data covering an area of 16 by 8 km, and from surface down to 1830 m depth. This paper concentrates on the methods used in the GeoSpace system for the processing, integration, display and interpretation of such a large and diverse data set. A block model was developed that recorded the relative frequency of each geological feature within each block. The data input for the block models were based on recoding of the Campbell Mine drilling and channel sample databases into lithological, alteration and structural subsets. The value for each geological characteristic inserted into each block is calculated from all available data that falls within the block. Relative and absolute comparisons of the individual variables provide a targeted outcome from which the blocks are coloured for visual inspection. Different combinations of variable comparisons can be evaluated so that required features are highlighted for interpretation. Blocks are displayed to illuminate the ædominantÆ rock type, according to a formula that may be varied interactively to display the features required by the geologist. This flexibility allows rapid remodelling of lithological distributions, commonly highlighting minor lithological packages not readily visualised in, and interpreted from, drillhole traces alone. The 3D geological model was built from the drillhole datasets and old mine plans utilising standard 3D mining, GIS and database software, with several iterations of plan and sectional interpretation. Near surface bedrock geological interpretations were further constrained by low level aeromagnetic data. The Geospace approach employs an innovative technique for visualisation of the distribution of lithological packages and alteration via block modelling. The method utilises the block model format of data handling as it is considered to be more visible than drilling, flexible enough to incorporate a wide range of data sources, and allows for spatial proximity relationships to be investigated. The method is a simple form of processing large data sets so that results are clearly visible. The calculation is much more rapid than estimation procedures, and does not have any requirement for geostatistical interpretation which is also time consuming. Geospace is not unique to any mine environment software and it is expected to be able to be performed in any system. The proper portrayal of the internal structure of the mineralised body will provide practical input to exploration and mining principally in the areas of resource estimation, exploration vectoring and ore/waste characterisation and may be incorporated with other data to include mine support and mine scheduling.

Jan 1, 2003

I offer some comments which might complement the valuable recent paper by De Angelis et al (1987), on the newly discovered nickel-copper deposit at Radio Hill.The authors have accepted subdivisions and correlations by Hickman (1977, 1983) although they are disputed (Fitton, Horwitz and Sylvester, 1975; Horwitz, 1979; Horwitz and Guj, 1986).Also, in my opinion, more plausible correlations of the Sholl Belt with Whim Creek Belt have been shown, but not discussed, in Hudson and Horwitz (1986, Figure 1). Our suggested correlations and subdivisions have appeared in publications and reports which are not readily available, but it is gratifying to note that many of the observations and conclusions of De Angelis et al are consistent with our conclusions of the Whim Creek Belt.The units of the Sholl Belt (of Hickman, 1983), between the Sholl Fault (Shear Zone) and the overlying Mt Bruce Supergroup to the south, equate well with units of the Whim Creek Belt. A basalt, characterised by an abundance of vesicles and similar in many ways to the Wararnbi Basalt of Fitton, Horwitz and Sylvester (I975), is well developed at the base of the succession, particularly in the southern part of the area (Figure 1). It is overlain by acid tuffs (locally metamorphosed, such as at Whundoo Mine) and associated acid and mafic lavas, similar to those of the Mons Cupri area. The mafics in the succession are marked by the absence of the numerous cherty sedimentary intercalations, such as the Marble Bar Chert, which occur in the Warrawoona Group; and they also lack the intense chertification that is prevalent in all parts of the proven areas of Warrawoona Group rocks.The Whim Creek Group is overlain, locally unconformably (two to three km east of Mount Negri), by the Negri Volcanics which include here the Louden Volcanics (unit Abu of Hickman, 1977), (Horwitz, 1979). The negri volcanics are an alternating sequence of variolitic and quench textured lavas not dissimilar to the highest units of the Sholl Belt (Figure 1). They range from high-Mg basalt to tholeitic andesites (Glikson et al, 1986, pp 79 and 84). The whole succession of the Sholl Belt is estimated to be of the order of four km in thickness, more consistent with the two km thick (Horwitz, 1979, Figure 1) Whim Creek area sequence than with the much thicker Warrawoona Group sequences. The Whim Creek Group (including the Negri Volcanics) is considered to be a widespread grouping (Fitton, Horwitz and Sylvester, 1976; Horwitz, 1979; Horwitz and Guj, 1986) which is prevalent in the northern part of the Pilbara Craton. It is considered by these authors to include the Mallina Formation turbidites of the trough area of Ryan (1965). One component, the Mons Cupri Volcanic, is about 2.95 Ga (Richards and Blockley, 1984). Between the Sholl Fault and Egina, the Whim Creek Group is intruded by large ultrarnafic to granophyric ills of the Millindinna Complex (Fitton, Horwitz and Sylvester, 1975), dated at 2.860 ± 002 Ga by Gulson and Korsh (1983) near the Sherlock River (south side of Caines Well Granite area). The Millindinna Complex has been equated to the same magmatic episode as the layered complexes of the Sholl Belt by Fitton, Horwitz and Sylvester (1975, p 20).

Jan 1, 1988

By T Sparks

The Collie River catchment, located approximately 200 km south of Perth, covers an area of around 2830 km2 and is the source of run-off to the Wellington Dam, an important irrigation water resource for the Collie Irrigation District. The salinity of the Wellington Dam has increased due to historical clearing and irrigators currently use water with salinity levels approximately twice that of the Murray River in South Australia (Water and Rivers Commission, 2001). The Collie River Salinity Situation Statement (2001), released by the Water and Rivers Commission (now the Department of Water), identified realistic actions that could achieve the salinity reduction target. Subsequent benefit-cost analyses and prefeasibility studies recommended the diversion of the most saline flows in the Collie River away from the dam as an immediate intervention (URS, 2003). The East Branch of the Collie River above the locality of Buckingham (20 km east of Collie) contributes around half of the salt that flows into the Wellington Dam and the diversion and storage of the saltiest flows from the East Branch at Buckingham was identified as a viable option for reducing salinity in Wellington Dam. The proposal had one problem û the water could not be disposed of as quickly as it was diverted. However, in the vicinity of the diversion site were a number of coal mine voids and after preliminary discussions, the Government/Griffin Coal alliance was formed and from this the opportunities have continued. Diverted water would be stored temporarily in an adjacent mine void (Chicken Creek 4 void) and then disposed of to the sea. The disposal options included Western Power CorporationÆs saline discharge pipeline from Collie Power Station, or a new pipeline. The diverted water was also identified as a potential raw source for treatment and use in industry. This has opened up opportunities including desalination, water efficiencies in the power stations, increased reliability of water supply for the power stations, water for new industries, wastewater disposal options and extra water for PerthÆs water supply. In the process of solving the water storage problems the project introduced a range of mine water quality problems û heavy metals and pH û and the Department of Water (DoW) is now working with the mining industry and the Centre for Sustainable Mine Lakes (CSML) to develop treatment and management technologies. The project has received support and funding through the National Action Plan for Salinity and Water Quality (NAP) and it has been possible to accelerate and enhance this project as a result of NAP. The DoW has developed the proposal to an advanced stage and gained approvals for the capital diversion program to go ahead. The partnerships have expanded to include the second mining company, Premier Coal, the Water Corporation, Western Power and the Harvey Irrigation Cooperative. The proposal could feasibly result in a $90 million integrated water management initiative for Collie using the latest technology, mining operations and providing water for value adding industries in the local area. The DoW is not a mining company; however, our experience in managing water in times of shortage, environmental water quality criteria, competition for water and managing community expectations will have the same success factors:consultation and knowing your community and stakeholders, sharing issues and working in partnership can provide results far greater than the initial issue, even brackish water has value, every sector is in competition with each other and has to have a share of the water, an integrated approach can provide opportunities for development in areas of water shortage, and never think of water as wastewater.

Jan 1, 2006

The fluorspar deposits at Okorusu, Namibia are closely related to an alkaline igneous ring complex of late Cretaceous age (125¦7 Ma). The fluorite ores consist of relatively fine-grained purple replacement fluorite and subsequent coarser-grained purple and green vug-filling fluorite crystals. Homogenisation temperature measurements for 38 primary fluid inclusions shows that main stage purple to green fluorite crystals were deposited over a temperature range from 166¦C to 144¦C, and minor late yellow fluorite was deposited at lower temperatures from 132¦C to 128¦C. Homogenisation and freezing temperatures measured for 18 primary fluid inclusions shows that the fluorite-depositing fluids were less saline than Mississippi Valley-Type (MVT) ore fluids and overlap the lower temperature range of fluids that deposited epithermal ore deposits. Mining in three open pits (A, B and C) at Okorusu has gradually provided exposures which reveal that the fluorite orebodies have been emplaced primarily by the preferential replacement of carbonatites. Evidence for the replacement of carbonatite includes: replacement remnants of carbonatite within the fluorite ores; goethite pseudomorphs after the carbonatite minerals, pyroxene, pyrrhotite and magnetite, which are disseminated in the fluorite ores; andpartial replacement by fluorite of a large sill-like carbonatite body in the A pit. Electron microprobe analyses of minerals in unreplaced portions of the carbonatites show that their mineralogy consists of titaniferous magnetite, diopside pyroxene, apatite, biotite and calcite. Magnetite contains 6.97 per cent to 10.46 per cent TiO2, averages 8.44 per cent TiO2, and has an average V2O3 content of 0.35 per cent. At high magnifications under the scanning electron microscope (SEM), the magnetite shows abundant fine ulv÷spinel exsolution lamellae arranged in a cloth texture. Apatite contains moderately high fluorine contents that range from 3.21 to 5.0 per cent and average 4.2 per cent, and apatite crystals range in total rare earth oxides from 1.7 per cent to 2.61 per cent. Pyroxenes in the carbonatites are iron-rich diopside, and they contrast to pyroxenes in the fenites that are aegirine-augite. All of the microprobe analyses for mica crystals in the carbonatites give biotite compositions. Microscopic examination of fluorite concentrates from Okorusu provides mineralogical information important to the resolution of beneficiation problems. Fluorite ores that are related to carbonatites are typically accompanied by phosphorus benefication problems. The cause for the presence of phosphate in some of the Okorusu fluorite concentrates is a function of the presence of binary locked fluorite-apatite particles. The fluorite ores have also replaced marble locally in the A pit, especially along the A band in the B pit, and dominantly in the orebody proposed for the new C pit. Those ores are characterised by fine grain sizes, faint remnant bedding, lack of carbonatite mineral pseudomorphs and local presence of remnants of unreplaced marble. Concentrates derived from those fluorite ores are devoid of phosphorus, but commonly have elevated silica contents due the presence of free quartz. Carbonatite and marble were preferentially replaced by fluorite because the calcite was readily soluble in the presence of the fluorite-depositing fluids and the dissolution of calcite provided calcium for the formation of fluorite. 

Jan 1, 2008

By J M. F Clout

The low-grade clay-rich -1.0 mm fraction of fine iron ores have often proved difficult to upgrade and capital intensive to process when using traditional wet beneficiation technology including single or two stage hydrocyclone desliming, wet high intensity magnetic separation (WHIMS), spirals and final dewatering using fine screens. Very fine (<0.010 mm) clay-rich slimes simply follow the water split to the hydrocyclone underflow where it often impedes the subsequent processing performance of any downstream spirals and can result in troublesome direct dewatering of hydrocyclone underflow. The -1.0 mm fraction in goethitic iron ores is typically considered as waste. A new two-stage wet gravity separation flow sheet, referred to as the ædesandÆ process, has been designed to overcome these issues for the upgrading of low-grade clay-rich goethitic or hematite-quartz fine iron ores. The desand process is designed to treat the -1.0 mm range from -8.0 mm natural fines, to recover a -1.0 +0.038 mm higher-grade fraction by rejecting to tailings any low-grade clay-rich ultrafines and low density sand-size fine chert/quartz gangue and shale.The desand process consists of wet screens with a nominal 0.7-1.0 mm cut point which direct the undersize to hydrocyclones. The hydrocyclone underflow is then fed to upcurrent classifiers where the classifier middlings is sent to spirals and classifier and spirals concentrates are then dewatered using vacuum belt filters or fine screens. The three product upcurrent classifier is employed to further deslime the hydrocyclone underflow, producing firstly a coarse final concentrate, and then a deslimed middlings for feeding to spirals as well as a 0.100 mm clay and fine quartz or banded iron formation (BIF) sand in final overflow for feeding to the residue thickener. The upcurrent classifier middlings provides the spirals with a significantly cleaner feed material than traditional methods, with the end result that the spirals do not silt up with slimes and therefore can continue to run at their optimum. The upcurrent classifier and spirals form a complimentary pair, with the upcurrent classifier better able to send coarser, acceptable grade particles to concentrate and fine slimes to tailings whilst allowing the spiral to better reject coarser, subgrade low specific gravity particles. Test results for the Mayoko-Moussondji iron project, Republic of Congo, using upcurrent classifier-Wilfley Table (simulating spirals) gave acceptable mass recovery from run-of-mine (ROM) and Fe recovery from hydrocyclone underflow for HEMCOL (6.2 per cent mass recovery from ROM/43.1 per cent Fe recovery) and HEMBIF2 (5.1 per cent mass recovery from ROM/22.3 per cent Fe recovery) mineralisation types. The desand process also enables improved dewatering of -1.0 +0.038 mm product from a clay-rich plant feed.A number of new wet plants in the Pilbara use the desand flow sheet including FMGÆs Cloudbreak and their two Christmas Creek plants. Many potential new applications are being explored, with new iron ore plants in India as well as those being proposed for West Africa. Operational experience has highlighted the importance of providing clean process water to the upcurrent classifiers as well as ongoing design improvements including increased wear life, reduced maintenance and enabling a more steady feed rate to spirals.CITATION:Clout, J M F, 2013. Beneficiation of fine iron ores using the desand process, in Proceedings Iron Ore 2013 , pp 337-348 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

Minerals and Metals Group (MMG) Century mine (Century) is a large open-cut mine in northwest Queensland approximately 2.5 km long, 1.5 km wide and 240 m deep, with an ultimate pit depth of 320 m. In 2009, the mine experienced three failures which began as small failures, and progressively developed into significant multi-batter failures. The incidents were managed by a combination of analysis, redesign and practical management to achieve positive outcomes for the mine. On the south wall of the mine, a series of batter-scale wedge failures occurred in December 2007. Analysis of structure orientations and design changes aimed to minimise the risk of failure extending over multiple batters, while accepting a risk of further small-scale failures. Design changes were constrained by a culturally sensitive area (CSA) located south of the wall. As mining progressed, shallow wedge failures developed over multiple batters and cracks were observed 60m back from the pit crest, indicating that a large-scale wedge failure was developing. Movement increased in January 2009 as a result of significant rainfall. After considering several design options, the area was stabilised by a cut-back of the wall. Two multi-batter failures also occurred on the north wall as mining progressed through a structurally complex area. Both north wall failures began as small failures that progressively developed, and required a redesign of the wall below as well as practical management of safety aspects. The complex structural geology was difficult to predict ahead of mining, and required geotechnical input into design changes as mining progressed. All three failures potentially had significant impact for ore recovery, and were managed by a combination of analysis, redesign and operational management have resulted to achieve positive outcomes in a challenging mining environment.

May 1, 2010

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

Historical exploration of the Ballarat East goldfield defined two primary quartz vein lode types. Tracking the intersection of these lodes with vertical lines of enrichment (or so-called æindicatorsÆ) was the basic practice for historical mining. This strategy proved highly successful in terms of identifying quartz veins associated with mineralisation. However, it provides little understanding of the timing or processes involved in the formation of these veins, or the associated emplacement of gold. Current underground mapping shows the Ballarat East gold deposit can be subdivided into four stages of vein formation. The earliest veins (V1 and V2) strike north-south and formed during bedding flexural slip and limb thrust fault propagation in parasitic chevron folds. V3 veins are subhorizontal and relate to further fold tightening involving a transition from east-west compression to north-south extension that initiated re-shear of bedded slip surfaces and additional strike-slip faults. Sporadic V4 veins overprint the shallow-dipping sections of V2 and V3 veins and are associated with weak north-south compression. The V4 veins mineralogy is distinguished by a high carbonate content and sphalerite-galena sulfide assemblage. Vein sampling indicates a significant increase in gold mineralisation where overprinting by the later deformation/veining has occurred. As a result of these observations, a new model is emerging that identifies the chronology, structural control and spatial distribution of respective quartz vein types. This is a major advance in terms of exploration targeting, resource modelling and mine planning.

Jan 1, 2008

In the current climate, there is a real need to bridge the gap between theory and the real world mining considerations, and develop viable, cost-effective, high performance thickeners. With a greater need to extract profits from both difficult-to-process ores and lower grade orebodies, coupled with the necessity to produce 'greener', less water intensive technologies, suppliers need to take current thickener designs to the next level and into the 21st century. The complexity of 'getting it right' within a thickenerÆs feedwell, the 'nerve centre' of the thickener, is no small task. Delivering dilution water and mixing this water with incoming feed slurry, addition of flocculant, maximising flocculant-slurry interaction to build aggregate size, minimising unabsorbed flocculant percentage, volume average of solids volume fraction, momentum dissipation ratio, dilution recycle ratio, volume average shear, maximum shear rate at exit, aggregate size on exit, uniform discharge profile and more ù all of these need to occur in the right order and in the right proportions within the feedwell. This paper discusses the genesis and evolution of a new feedwell design, the first major innovation in the thickening industry in over 15 years.

Jan 1, 2008

Current models for the origin of banded iron-formation (BIF) derived in situ iron ore deposits assume that the typical chert and iron oxide banded BIF is the primary rock from which enriched iron ore deposits arise by the selective leaching of quartz and the residual accumulation of the iron oxides. Weathering extends to the base of all the hematite deposits of the Hamersley Province, which lie within the saprolitic weathering zone, as shown by the preservation of the primary textures, and are overlain by a hydrated goethite zone representing the solum. Since groundwater typically contains dissolved silica, derived from the hydrolysis of silicate minerals, greatly in excess of the saturation solubility of quartz, it is incapable of removing quartz from below the watertable, and quartz is preserved in all saprolites derived from quartz bearing rocks. Quartz may be dissolved in the solum due to the influx of meteoric water having little or no dissolved silica, but soil-forming processes that dissolve quartz likewise alter the oxides by hydration and transposition with consequent destruction of primary textures, and there is no suggestion of soil-forming processes having produced the deposits, which typically extend to considerable depths below the water-table. A characteristic feature of the typical hematite orebodies is the unaltered nature of the iron oxides in the ore compared to those in the adjacent cherty BIF. Although the solubility of ferric iron at >10 ppb is much less than quartz, any process capable of dissolving the huge volume of quartz must also affect the iron oxides, but evidence of this is completely lacking in most ore deposits. Hydrothermal alteration at Koolyanobbing in the Southern Cross Province affects both cherty BIF and ore, and clearly shows equal mobilisation and recrystallisation of hematite within quartz/hematite veins and in the surrounding cherty BIF, which shows no evidence for the selective leaching of quartz. Similarly, any metamorphic process capable of removing all quartz from BIF would leave characteristic evidence in the remaining oxides. However, a hydrothermal process may account for at least portions of certain ore deposits, in which the chert bands have been replaced by carbonates at comparatively low temperatures, to produce a quartz-free magnetite/ carbonate rock that is readily upgraded to high-grade ore by supergene dissolution of the carbonates. This process is interpreted to have formed high grade ore at Mt Gibson, Koolyanobbing æAÆ Deposit and Mt Tom Price North Deposit. In addition to carbonate replaced cherty BIF at Mt Gibson in the Murchison Province, there are extensive sequences of magnetite BIF without chert bands, and this chert-free facies of BIF is interpreted as the precursor to the majority of in situ hematite ore deposits, through oxidation and weathering of magnetite and iron silicate and carbonate minerals. The world-class martite/microplaty-hematite deposits of the Hamersley Province are a special case of BIF-derived iron ore deposits that were initiated during the Proterozoic era. Evidence from overlying Wyloo Group conglomeratic horizons containing clasts of Hamersley Group BIF indicates that microplaty-hematite formed within the clasts before deposition, and that Proterozoic subaerial oxidation and weathering of uplifted Hamersley Group formations produced the microplaty-hematite in both chert-free and cherty BIF.

Jan 1, 2002

By A Radici, S Russell

The Dampier Port Upgrade was completed in 2007 and is the largest project in Rio Tinto Iron Ore's expansion program. The project doubled Dampier Port's iron ore shipping capacity over a five year period. Sinclair Knight Merz (SKM) was appointed by Rio Tinto as the Engineering, Procurement and Construction Management (EPCM) contractor to manage Phase A and Phase B of the Dampier Port Upgrade. The aim of the project was to increase the Dampier Port capacity from 74 to 140 million tonnes per annum (Mt/a). This increase in shipping capacity tripled the capacity of the Parker Point facility from 34 to 94 Mt/a, whilst the East Intercourse Island facility increased from 40 to 46 Mt/a. The Dampier port remained fully operational throughout construction and achieved record yearly export tonnages over the period of the project. The $US1.4B project was completed ahead of schedule, on budget and with an outstanding safety record. Significantly the project team set an industry benchmark by achieving five million man-hours Lost Time Injury (LTI) free. The project has been recognised by the Engineers Australia 2008 Western Australian Engineering Excellence awards as category winner in resources and the overall winner in WA, and went on to win a National Engineering Excellence award. This paper provides an overview of the EPCM project management and an insight into some of the key drivers that have delivered this outstanding project.

Jan 1, 2009

By J Finlay, P Betts, D Milton, H Williams

The aim of this paper is to present an innovative method to help delineate potential target volumes for haematite-goethite mineralisation as opposed to more magnetic ores. This is achieved through interpretation and modelling (2.5D and 3D inversions) of ground magnetics and gravity surveys over the Koolanooka South prospect in Western Australia. The targets are assumed to be dense and weakly magnetic and hosted within banded iron formation (BIF) horizons. Geophysical interpretation (2D map) was performed using a variety of processed magnetic and gravity images (Betts et al, 2007) to determine the distribution of lithologies, to understand the structural architecture and to map out any anomalous areas of excess density (possibly indicating goethite alteration). The created geological map is used to build geological cross-sections (geometrically consistent) that were modelled (in 2.5 D) against both potential field datasets. The crosssections are consequently used as the framework to build a 3D geological model. The model defines 3D volumes of rocks including several BIF horizons. The distribution of densities and magnetic susceptibilities of the BIFs is inverted within the GOCAD«-VPmg environment to reduce the misfit between the response of the model and the observed gravity and magnetics. By combining the results of both petrophysical property distribution it is possible to map out (using classical GIS type queries in 3D) volumes of higher density and lower magnetic susceptibility.

Jan 1, 2009

By G K. Robinson, M D. Sinnott

Three-dimensional granular flow models have been run to simulate three types of sample cutters: a cross-stream cutter, a vezin, and a cross-belt cutter. This type of modelling involves solving the equations of motion for large numbers of individual particles as they travel along a conveyor belt and interact with a sample cutter. It allows flows of bulk materials to be visualised and understood. Here we have used spherical particles. These results illustrate some advantages that modelling has compared to physical bias testing: By taking reference samples which are very close to the actual samples, the estimation of bias can be achieve quite precisely with very few runs. (Many Standards about bias testing recommend a minimum of 20 runs, but we have found that five runs generally provide adequate precision.) Potential bias can be divided into two components: the particles which are missed but should have been sampled and the particles which are extra but which should not have been sampled. This more detailed information can provide useful insight. Exactly the same material can be sampled using different sample cutters, thereby avoiding a source of variation that complicates physical testing. Much more detailed visualisation is possible, allowing better understanding of the bulk material flow in various circumstances.

Jan 1, 2005

By W A. Peppin, D N. Riley, N W. Schulenburg

In June 2008, a joint airborne collection using hyperpspectral systems was tested on a single Twin Otter aircraft. This experiment was designed to incorporate two airborne hyperspectral sensors for geological and environmental projects. Mineral exploration and environmental impact statements are two areas where full spectrum hyperspectral data can document the mineralogy at the surface prior to mining operations. Many previous hyperspectral remote sensing collections were collected on a single aircraft with a single sensor. Mineral mapping using hyperspectral sensors that measure in complimentary regions of the electromagnetic spectrum is cost effective as it allows for the mapping of clays, sulfates, carbonates, feldspars, quartz, garnets and many other minerals. This report describes the experiment using the following two hyperspectral sensors: ProspecTIR, a visible near and shortwave infrared (VNIR-SWIR) sensor with 356 channels and spectral range of 0.4 to 2.5 ¦m, along with a spatially enhanced broadband array spectrograph system (SEBASS), a midwave and longwave infrared (MWIR-LWIR) sensor with 128 channels from 2.5 to 5.3 ¦m and 128 channels from 7.6 to 13.5 ¦m. SpecTIRÆs ProspecTIR system and The Aerospace CorporationÆs Spatially Enhanced Broadband Array Spectrograph System (SEBASS) are pushbroom sensors, have high signal to noise ratios, have similar swath widths and instantaneous fields of view. Examples of data collection experiment will be shown with a focus on mineral/lithologic identification and mapping along with environmental assessment in the western United States. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By F Clark, B Catto

The Mako domain comprises the Mako lodes at Sunrise Dam Gold Mine, Western Australia. This domain was initially bulk or æbucketÆ domained for the open pit resource in 2000, due to complexity in defining the lodes as a result of low drill density. Negative ore tonnage and positive grade and ounce reconciliations were experienced during mining of the domain in the mega-pit, though only small volumes of the domain were mined. Significant amounts of exploration and underground grade control drilling has been completed since the initial bulk domain interpretation and greater geological understanding of the mineralisation controls and geology of the lodes now exists. Mako provides approximately 50 per cent of the ore tonnes and ounces for the North Wall Cut-back, the latest open pit phase of mining at Sunrise Dam. The importance of Mako to mill supply and life-of-mine planning, as well as past reconciliation performance necessitated a reinterpretation of the domain to increase confidence for mining. Historic exploration drilling, underground grade control drilling and detailed pit-wall mapping were used to build mineralised subdomains within the confines of the original domain. These reflect more closely the spatial extents and geological controls on the mineralisation. A new resource model using the multiple indicator kriging (MIK) technique was generated using the new domains. It resulted in a decrease in tonnes and ounces but increase in grade for the sum total of the new domains compared to the old æbucketÆ domain. This is attributed to the increased selectivity and structural constraints imposed by the new domains. A retrospective comparison of the Mako grade control from the mega-pit versus the new resource model was conducted, which æreconciledÆ 103 per cent tonnes, 106 per cent grade and 110 per cent ounces. This has provided confidence that the new model is a better estimate of the lodes. Qualitatively, the new model is a better representation of the geology and extent of the mineralised structures with significant areas of change identifiable. Grade-tonnage plots comparing the 2006 and 2008 models show that most tonnes have been shed from the low-grade û subeconomic grade cut-offs. This is mostly attributable to the volume reduction of æoreÆ in the 2008 model compared to the 2006 model, where the true mineralised zones are captured by the new domains. The reinterpretation and remodelling of Mako is an example of an evolved domain model and shows that mineralised zones need to be differentiated adhering to the geology and geological controls on mineralisation, which are understood largely due to increased drilling density coupled with mapping.

Jan 1, 2009

The increasing global demand for rough materials forces almost every mine to look at the mechanisation in their processes. This will not onlyimprove performance but with safety issues becoming more and more prevalent, the need for the introduction of mechanisation technologies to mining applications is essential. Ongoing developments are occurring in almost every field, ranging from basic developments to specialised mining. Mechanical tunnelling and shaft sinking have set the standards regarding safety, profitability and environmental protection. Different machine types and working principles have been developed to suit the geological and hydrological requirements of tunnelling projects worldwide. Continuous activity in research and development leads to constant optimisation of tunnelling performance.

Jan 1, 2008

By A Murphy, D Lauder, J Miranda

Minera Alumbrera Limited operates the Alumbrera concentrator, treating a nominal 80 000 tpd of porphyry gold/copper ore. It is located in Argentina, 1200 km north-west of Buenos Aires in Catamarca Province, at an elevation of 2550 m above sea level. Treatment facilities consist of crushing, SAG and primary ball mill grinding circuits, rougher flotation, ball mill regrinding, gravity recovery and cleaner flotation. It is one of only a small number of concentrators in the world, which uses Jameson Cells alone for cleaner circuit flotation. Plant design was started in June 1995, with commissioning commencing in July 1997. Following a successful ramping up to design tonnages and recoveries, a number of options were reviewed to improve gold and copper recoveries. This paper concentrates on a detailed size by size flotation recovery project, commenced in May 1999. Utilising optical microscopy, scanning electron microscopy and analysis of surface chemistry it has allowed losses by size fraction to be quantified and options for enhanced recoveries to be developed. Coupled with extensive circuit surveys it has also provided an insight into previously unknown properties of Jameson Cell operation. Among these are unique residence time and bubble formation reactions to reagent and pulp flow variations, which has permitted a number of novel changes to the operation to maximise capacity and recovery.

Jan 1, 2000