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By M Barley, C A. RosiFre, L Lobato

The Carajßs iron ore deposits contain approximately 17.5 billion tons of ore with >64 per cent Fe and occur in the eastern part of the Amazonas Craton. They are hosted by jaspilitic banded iron-formation (BIF) of the Carajßs Formation which, together with metavolcanic rocks, comprise the ~2.75Ga Grpo Parß Group of the Itacai·nas Supergroup in the ~1000 km long, E-W trending Carajßs Synclinorium. The Carajas Formation comprises discontinuous layers and lenses of partly dolomitised BIF (17 - 43 per cent Fe and 35 - 61 per cent SiO2) and lenses of high-grade iron ore, cut by mafic sills and dykes. The high-grade iron ores occur as large tabular bodies of friable (soft) hematite with smaller lenses of hard (compact) hematite. The hard hematite ores typically occur at the contact with the underlying volcanic rocks and are surrounded by an aureole of hydrothermal carbonate alteration. BIF that has been overprinted by dolomite and magnetite crystallisation has recently been discovered at depth in the N4E Mine. With increasing amounts of carbonate, the original lamination (microbanding) and other fine primary structures in the BIF have been progressively obliterated resulting in alternating carbonate and iron oxide mesobands. The friable hematite ore that is characteristic of the Carajßs deposits results from ongoing weathering and leaching of the carbonates from this type of altered BIF. The hard hematite ores probably result from more extensive early oxidation. The association of both carbonate-altered and jaspilitic BIF with the N4 Mine is similar to that observed at the Mount Tom Price deposit in Western Australia, where carbonate-altered BIF occurs below massive hematite ore with a jaspilitic halo developed above the orebody. This indicates that as at Mount Tom Price, hydrothermal carbonate alteration and associated loss of silica from BIF may be an important step in the formation of these giant hematite deposits.

Jan 1, 2002

The paper describes the development leading to the bucket wheel excavator systems now used in the Latrobe Valley and refers in particular to the new S.E.C.V. dredgers Nos. 14 and 15 which will be employed in the Loy Yang open cut. The design concept and operating possibilities of these dredgers are described in detail with reference to the machine characteristics designed for the operating conditions in the Latrobe Valley. The design is compared with units of similar capacity in open cuts of other countries.

Jan 1, 1982

This paper deals with the evolution of Canadian shaft sinking technology over the last 15 years. Most, if not all, shaft excavation projects in Canada prior to 1990 were sunk using traditional benching methods with labour intensive equipment. In the late-1980s, J S Redpath Limited of North Bay, Ontario, Canada, were contracted to deepen the shaft at Atomic Energy of Canada LimitedÆs Underground Research Laboratory (URL) located in southern Manitoba. The laboratoryÆs role was underground hydrological and geomechanical research, so the project offered both time and opportunity to conduct additional experiments while sinking. The offshoot of the research program was the true birth of the Canadian version of full-face, long round shaft sinking technology. Throughout the 1990s, this sinking method has been further refined over a number of shafts. The results have been faster sinking rates, a safer work environment and an overall improvement in project economics.

Jan 1, 2002

Porphyry type mineralization of Lower Cretaceous age in eastern Queensland has been recognized only from the easternmost part of the northern New England Orogen (Day, Murray and Whitaker, 1978), within the northern Yarrol Province (Horton,1982). Recent work about the Mt. Suthers (Pb, Zn, Ag, Cu, Au), Lug-e-nor (Cu, Pb, Zn, Ag, Au, Mo), and German Tully (Cu, Au, Bi) prospects suggest that there has been a phase of porphyry type mineralization within the Gympie Province, of Lower Cretaceous age, overprinting earlier Permo-Triassic phases. About the Mt. Suthers Prospect surface samples of shallow, medium to heavy textured soils derived from marine sedimentary rocks of Permian age, and extrusive and intrusive igneous rocks of intermediate composition and Triassic age, were analysed for Cu, Zn, Pb, Co, Cr, Ni, Fe, V, Mn and Ag. Whereas strong iithological control determined the distribu- tion of Cu (diorite) and of Cr, Ni, Fe and V ,sedimentary rocks), the distribution of Pb, Zn, Ag and of Cu, were determined by mineralization of faults by a cavity fill hydrothermal process. Gold is associated with the Pb, Zn, Ag mineralization. Co and Mn showed distributions independent of lithology and structure. The fault controlled style of mineraliz- ation at Mt. Suthers is repeated at other localities to the south; Calgoa, Marodian, and German Gully. Relative dating of structural features and isotopic dating of nornblende porphyrites (134-135 m.y.) near and related to those mineralized at German c;ully suggest a previously unrecognized phase of porphyry copper style mineralization in south-east Queensland of Lower Cretaceous age (Fig. 1).

Jan 1, 1987

Scale build-up in titanium palladium alloy spent electrolyte heat exchangers in the residue treatment plant commissioned at Risdon, Tasmania in 1971 was shown to be a mixture of manganese dioxide and anhydrite (CaSO4). The manganese dioxide was deposited as a result of thermal decomposition of permanganate ions present in the spent electrolyte. It was shown that deposition of manganese dioxide and associated anhydrite scale could be prevented by prior reduction of permanganate ions to the manganous (Mn++) state by the addition of ferrous ions. In the plant this was conveniently accomplished by injecting into the inlet line to the heat exchangers sufficient zinc plant solution containing ferrous sulfate to decolourise the spent electrolyte. This action prevented deposition of such scale for another 21 years, until the heaters were finally decommissioned in March 1992. Measurements indicated that addition of the reducing solution lowered the anodic potential of the titanium alloy by 200 - 300 mV (depending on the solution resistance), but that it was still +300 to 400 mV with respect to a standard calomel electrode. It was shown that, if necessary, a small impressed current could be applied to provide anodic protection. Before scale deposition was overcome by the addition of ferrous sulfate solution, badly scaled heat exchangers were cleaned by recirculating a solution of hydrogen peroxide in spent electrolyte or dilute aqueous sulfuric acid, after laboratory testing of a variety of possible solvents for the scale. Corrosion tests indicated that attack on the titanium alloy by the acidic peroxide cleaning solution was insignificant.

Jan 1, 2005

By D S. Collins, Z Hosseini, I Pinnock, Y Toya

Microseismic monitoring is regularly used in the mining and geotechnical industries to provide detailed information about rock mass response to operational activities. This paper implements a variable 3D velocity model (VM) at a North American hard rock mine with the aim of further improving the accuracy of seismic event locations. A collapsing method is also used to help analyse two individual seismic event clusters at another North American hard rock mine. In the first case study, the location accuracy of events is shown to improve by moving from a conventional single VM to a variable 3D VM that accounts for voids and different geological domains. The modal average for the event location accuracy improved from 14 m to 5 m when the 3D VM was used. Additionally, the single VM failed to locate 26 per cent of the seismic events that were located by the 3D VM. In the second case study, the distribution of seismic events was further enhanced by using a collapsing method that highlighted planar structures. The collapsing method was performed on two large event sequences that occurred in close proximity and identified different seismic event distributions. One aftershock sequence aligned along a plane, suggesting an activated structure, while the other large event sequence had a more 3D distribution of events, suggesting a complex stress redistribution on smaller structures.CITATION:Pinnock, I, Collins, D S, Toya, Y and Hosseini, Z, 2016. Large event sequence analysis and 3D velocity models for seismic event location accuracy, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 879–884 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Anievas JB, Sevillano AC

This paper describes the acquisition, exploration, development, initial operation and subsequent financing of the Bulawan mine by means of a listing on the Toronto Stock Exchange of a subsidiary of the parent company, Philex Mining Corporation.Located on the island of Negros in the Philippines the property is unique on at least two counts: it is a disseminated gold deposit that occurs in a region of predominantly porphyry copper mineralisation; and it is a gold deposit that is mined by a bulk method of extraction (front and block cave) instead of the normal selective mining methods.

Jan 1, 1997

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

Jan 1, 2006

Project-finance risk assessment is mature and approached systematically. Mining industry due diligence remains fragmented with specialists addressing different aspects of the project such as reserves/JORC, environmental impact, commodity market, even financial analysis/ modelling. Each professional has a natural tendency to believe that the risk factors they have examined are the key ones necessary to be reviewed, as if their review will stand in isolation from others in the way a project materialises. By first laying out the project risk categories and risk matrices, this paper examines the due diligence process with a keen eye to the risk assessment and overlap/interaction. Some cross fertilisation of due diligence techniques from other industry sectors is placed into the mining context. Six case studies are then presented with regards to due diligence features in each projectÆs feasibility review or financial information/ offering memorandum. A power case first shows the differences between the due diligence expectations of banks versus bond financings. Then some Australian and Indonesian mining development cases are analysed to see the due diligence learning points. Some of these were project/due diligence failures. The conclusion focuses on the value of a systematic risk assessment for project evaluation, all from the project-finance perspective.

Jan 1, 2007

Addressing community concerns in relation to an economic activity, particularly when it causes significant community impacts, is especially important for the development of extractive industry projects. Pipelines comprise an integral part of many hydrocarbon developments, which may cause different effects on local economic development, communities and the environment compared with open cast mines. This paper explores community impacts associated with a case study of the oil pipeline æEastern Siberia-Pacific OceanÆ in the Republic of Sakha (Yakutia), Russia. Based on semi-structured interviews, conducted in 2006 - 2008 in Russia, the paper investigates claims of local communities about potential impacts of the pipeline development of their environments and economic activities as well as community claims for greater involvement in sharing the benefits from this major infrastructure project. A community of Indigenous people, Evenk, is likely to be most profoundly affected by the development due to impacts on their traditional activities such as hunting and reindeer herding. The paper examines in detail the regional economic, social, environmental and Indigenous peoples concerns over the construction of the oil pipeline and investigates actions and methods adopted by community organisations to voice their concerns about the pipeline development. Finally, the paper assesses the process of interaction between the pipeline developers and regional stakeholders.

Jan 1, 2009

By M J. Nugus, F Clark, E J. Hill, J T. Carswell, J S. Cleverley, N H. S Oliver

High-nugget gold orebodies are difficult to model in 3D because samples from diamond drill core are generally too small to provide reliable estimates of the gold content of the larger body of rock, and therefore interpolation of gold assay values between drill holes is also unreliable. As a result, gold resources are generally underestimated in areas of high nugget. In practice, proxies for gold mineralisation, such as presence of alteration, specific structures or high vein density, have been used by geologists to predict rocks which are favourable for mineralisation. However, there has been no automated method for combining the predictive capabilities of several proxies, except by human judgement.We have been developing a method to combine several different types of geological features or geochemical analyses into a single measure using conditional probability. Conditional probability provides a meaningful numerical measure for the favourability of rocks for containing high-grade gold mineralisation. This measure can be interpolated in the exploration space, providing a sound basis for a 3D model of the orebody. We have developed this technique using data from the Sunrise Dam Gold Mine, which is a high-nugget orebody hosted in a structurally complex Archaean greenstone belt and which has historically proved to be a very challenging orebody to model.CITATION:Hill, E J, Nugus, M J, Clark, F, Oliver, N H S, Cleverley, J S and Carswell, J T, 2013. Predictive three-dimensional modelling of nuggety gold orebodies, Sunrise Dam, Western Australia, in Proceedings World Gold 2013 , pp 463-468 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

No paper available.

Jan 1, 1996

By A J. Burchell

The introduction reviews the tunnelling carried out in Singapore since the early 1980s. Between 1983 and 1990, Phases 1 and 2 of the mass rapid transit system were constructed. These included some 20 km of bored and cut and cover tunnels together with 18 underground stations. Some particular points of interest in this massive project are briefly commented upon. Reference is also made to other underground or underwater schemes undertaken during this period such as the proposed large caverns project and the submerged tunnel to Pulau Seraya. A description of the subsurface works, now under construction in Singapore, follows. This includes an all underground North-East railway line 20 km long with 16 stations. At a budget of US$ 3 billion, this is a major civil engineering undertaking. Another project is the extension of the railway to Changi Airport which involves 3.5 km of twin tube tunnelling together with a major underground station which is fully integrated into the airport terminals. An on-going program of further major railway extensions over the next 10 to 15 years is in place and an outline is given of some of the most important underground sectors. Other proposed projects such as the underground roads system and the deep level sewers are briefly described. Together they demonstrate the very significant volume of underground construction scheduled for the next century in Singapore.

Jan 1, 1999

By McLennan T, Howells E, Zastawny H, Watt J. S

Nuclear techniques have been used to determine the solids weight fraction (W) and ash content of (fine) coal in slurries independent of voidage variations. The method is based on the correlation between W and the hydrogen concentration Hsl (wt/wt) of the slurry. Hsl is determined by combining measurements of neutron moderation and ?-ray transmission. Both Wand ash content are determined by combining the above measurements with the ash-sensitive measurement of X-ray backscatter compensated by a measurement of iron K X-ray intensity.The nuclear analysis system, called the SIRO coal slurry gauge, has been proved in a six-week plant trial at the BHP Steelworks washery at Newcastle, NSW. Several probes, each containing a radioisotope source and scintillation detector, were immersed directly into the coal slurry in the feed box upstream from the bank of flotation cells. For 140 samples W, ash and voidage varied in the ranges of 0 to 13 wt percent, 26 to 41 wt per cent and 0 to 4 vol. per cent, respectively. The r.m.s. difference in solids weight fraction, determined by probe measurements and conventional assay, was 0·52 wt per cent. Ash was determined with an r.m.s. difference of 2·0 wt percent in the coal. Better sampling techniques were used in the last half of the plant trial, and r.m.s. differences were 0.35 wt per cent solids and 1·5 wt per cent ash.

Jan 1, 1986

By J V. Lawless

Two types of low sulphidation epithermal deposits that have different gangue mineralogies and ore shoot geometries are recognised. One has laterally near-continuous ore shoots over a significant vertical interval that consist of quartz, chalcedony, pyrite, minor base metal sulphides and adularia, with electrum. The other type of deposit has discrete near-vertical ore shoots of a lesser vertical extent, that consist of quartz, pyrite, base metal sulphides, sulphosalts, electrum and in their upper parts barite, which are enclosed in veins of earlier quartz. The gold mineralisation in both deposit types is considered to be a co-precipitate of pyrite, with that in the first type of deposit produced by prolonged boiling in an upflow of a hydrothermal system (Upflow Deposits); an example is Waihi in New Zealand. The other type is produced by mixing, a deep water primed for gold deposition by prior limited boiling, with an iron-bearing oxidised condensate of the steam released by the boiling, in an outflow of a hydrothermal system (Outflow Deposits); an example is Thames in New Zealand. Early recognition of these different types of deposits can be used to develop mineralisation models of predictive value on which to focus exploration drilling. Early recognition of an Upflow Deposit promotes an extensive program to delineate the extension of the main ore shoot. In contrast recognition of an Outflow Deposit requires a more intensive approach to find individual ore shoots which, although smaller than those found in Upflow Deposits, may be high-grade, particularly if there is earlier mineralisation present to act as a protore.

Jan 1, 1999

By P K. Singh

Recent advancements in understanding the detonation process are noteworthy, but they are still based on somewhat hypothetical situations. The actual variables that are essential parts of normal blasting practice have not yet been taken into account in such treatments. These include the various initiation practices employed to detonate a column of explosive, from single point initiation to multi-point initiation in blast holes, and the effect on detonation characteristics of both detonators and explosives under multi-deck and multi-hole blasting conditions. The in-the-hole velocity of detonation (VOD) of an industrial explosive is dependent on explosive’s charge diameter and blasthole diameter. The relationship between blasthole diameter and VOD provides a fundamental guideline to the rate of energy conversion and energy release within the detonation front on the interaction of explosives with the confining medium.The in-the-hole VOD of explosives was measured at four experimental sites in India for different blasthole diameters, ie 150 mm to 311 mm, but for identical explosive composition being same particle size, density, viscosity and loaded into blastholes with the same degree of confinement. The results of the studies demonstrated that there is definite relationship in in-the-hole VOD of the explosive and the diameter of the blast hole. The study also confirmed that the explosives initiated with concentrated boosters yielded higher VOD in comparison to those explosives that were initiated with multi-point priming. The measured increase in VOD of explosives for increasing diameter of holes was up to 24 per cent. The rate of change in in-the-hole VOD of explosives increases with increasing blasthole diameter. It can be further stated that the in-the-hole VOD of the explosive reaches a fairly constant value after reaching a limiting/threshold diameter of 311 mm.

Nov 8, 2011

By G Danckert

The key technical theme of ‘orebody knowledge’ has been applied by Rio Tinto in the Pilbara iron ore precinct from 1966, when operations first started there. It forms the basis of present day application, as well as planning for the future.This paper will review how the early towns and mines commenced and how they formed the basis of Rio Tinto’s early operations, on which the Pilbara precinct has been based. A profile of the last decade of Pilbara growth will be highlighted, together with the current integrated network of mines, rail and ports and the next generation of expansions.The paper will specifically describe the Rio Tinto process of significant resource evaluation, including comprehensive drilling programs and the conversion from resource to reserves. It will also describe the overall mine planning process, both from the strategic view, as well as for short-term mine plans.The ability to innovate in resource development will be discussed. This will include not only the technical dimension of changing cut off grades, use of low-grade ores and managing low-grade stockpiling and beneficiation, but also the broader application of new technology and innovation in the iron ore business.

Jul 11, 2011

By A Giyose, V Malysiak, K Davey

Batch flotation tests were conducted on a haematite-bearing Sishen iron ore slimes sample from South Africa using reverse cationic flotation. The effect of grinding on flotation performance, the flotation response of various key impurities in the sample, and the feasibility of increasing metal recovery by refloating tailings in a scavenger flotation step were investigated. The test results indicate that reverse cationic flotation is effective in rejecting impurities from the iron ore sample tested. From a head grade assaying 6.4 per cent SiO2, 2.14 per cent Al2O3, 0.402 per cent K2O, 0.082 per cent P and 0.194 per cent TiO2, the levels of impurities were reduced to 1.83 per cent SiO2, 0.88 per cent Al2O3, 0.095 per cent K2O, 0.066 per cent P and 0.174 per cent TiO2 in the final concentrate at a Fe recovery of 74 per cent. The flotation response of SiO2, Al2O3 and K2O were found to be better than that of P and TiO2. The testwork demonstrated that grinding to 80 per cent passing about 49 microns is essential for upgrading the Sishen iron ore to produce >67 per cent Fe concentrate grade. This grind size corresponds to about 80 per cent liberation of haematite from the gangue minerals. Fe recoveries up to 76 per cent were obtained by refloating the rougher tailings in a scavenger stage, with little effect on the final concentrate grade. Size-by-size Fe recovery data obtained indicated that particles below ten microns were mostly lost in the desliming stage conducted prior to flotation whilst some reported to the froth by entrainment. Some of the coarser haematite-gangue composite particles reported to the froth product by genuine flotation.

Jan 1, 2009

By A N. Parry, G van Wyk

"Sensor based automatic ore sorting technologies are used in the minerals industries to efficiently remove waste and submarginal grade material from crushed and screened run-of-mine (ROM) ore, producing a coarse (typically >10 mm) upgraded preconcentrate at an early stage in the mineral processing circuit. This avoids additional energy intensive downstream processing of this rejected component of the ROM feed, leading to lower unit operating costs and reduced tailings disposal volumes.Test work on bulk low-grade gold ore stockpile samples from Central Norseman Gold Proprietary Limited has been conducted, indicating high gold recoveries as well as high material rejection rates. A financial model, based on these results, evaluates grade sensitivity and identifies a minimum stockpile grade for adequate financial returns. The base case modelling estimates that the ex-stockpile grade (including the fines bypassed fraction) can be more than doubled through ore sorting and that the project will be highly viable with strong cash flow generation at stockpile grades as low as 0.7 g/t gold. The modelling will enable the company to benchmark ore sorting options against stockpile reclaim and screening operations currently employed. Citation:Parry, A N and van Wyk, G, 2016. Upgrading Low-grade Gold Ore Stockpiles by Preconcentration Using Ore Sorting - an Assessment of the Economic Impact and Viability, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 179–190 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By Medhurst TP, Trueman R, Hutchinson IN

A breaker line support (BLS) monitoring system, BLSmon, has been designed and constructed by the CSIRO and installed and commissioned at Laleham No.] Colliery, Queensland. This system was designed to record hydraulic leg pressure and canopy position measurements and relay these, in real time, to the surface. The system has shown itself to be capable of operating on the BLSs without any adverse affect on production. Analysis of the results of the monitoring exercise has shown that rate of change of leg pressures on the BLSs could be used as an aid in the prediction of adverse mining conditions. Under favourable mining conditions the supports were observed to initially unload from the set pressure, this unloading reduced with time and by the end of a typical lift cycle had either ceased or reversed slightly. This behaviour was considered to be due to one of four possible causes, these being; the compaction of floor debris, and/or compaction of the floor, and/or crushing of the roof and /or support creep. The actual cause can only be determined through detailed monitoring of both roof and support convergence. However observational data would suggest that compaction of debris and softened floor material beneath the supports was the most likely cause. The few positive loading rates recorded under these conditions were of short duration and occurred towards the end of individual lifts. Where mining conditions were unfavourable the negative rates of change of pressure, unloading of the support, were reduced throughout a lift, in both duration and magnitude, when compared with favourable mining conditions. Over the same period the positive rates of change were observed to be greater. The rate of change of loading and convergence can be utilised to identify the onset of instability in the lift area. However, before this facility can be utilised by the mine for the reliable prediction of instability more monitored data and sophisticated processing techniques are required.

Jan 1, 1992