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By Jin C, Shi X

The electrochemistry of leaching gold with thiosulphate has been studied systematically by using electrochemical techniques. Results show that the current peak of anodic dissolution of gold occurs at about 50 mV(SCE) and there is passivation in the polarisation curve in the thiosulphate solution in the absence of ammonia. Ammonia markedly improves the anodic dissolution rate of gold and reduces the passivation as well as making the current peak shift negatively. Results also show that there is no current peak for a cathodic process in the range of 0 -900 mV(SCE) in the thiosulphate solution in the presence of oxygen but absence of cupric ions and ammonia. In the solution containing 0. 1 mol/L cupric-ammonia ions, the peak occurs at about -400 mV (SCE) and the cathodic process is characteristic of a catalytic reaction. Oxygen presents a predominate effect on the cathodic process. Based on the electrochemical investigation, the following mechanism of leaching gold with ammoniacal thiosulphate has been proposed. Ammonia reacts primarily with gold ions on th anodic surface of gold and the formed A (NH3)2+ rea~s then with S2O 3 in solution to form the stabler Au(S203) 2 . Cu (NHS) 4 gains electrons on the cathodic surface and is reduced to CU(N) ? which is then oxidised by oxygen and regenerated into Cu(NH3) 4 after entering the solution.

Jan 1, 1993

By M E. Dunphy, P Silversmith

The Reefton Goldfield, both historically and potentially, represents a significant gold producing camp in the Westland province of New Zealand. Some two million ounces of gold have been produced from the Greenland Group host rocks between 1870 and 1951 with the most significant producers being the Blackwater and Globe Progress mines.   Steep terrain, high rainfall, poor outcrop, widespread fluvio-glacial deposits, tertiary cover and sometimes onerous environmental access conditions have proved a challenge to conventional exploration techniques. In addition classic exploration techniques have come up against a desire to reduce exploration cycle time and exploration costs while increasing both quality and quantity of geological information.   The trial, and subsequent implementation, of Wacker sampling has proved a highly successful and effective geochemical tool currently being utilised to target, discover, and define potential economic gold mineralisation in the Reefton Goldfield.

Jan 1, 1997

By S Doyle

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Macraes gold mine in Otago, New Zealand, is developed along the central portion of the Hyde-Macraes Shear Zone (HMSZ), which dips gently to the NE, and is traceable over 30 km of strike, before disappearing under tertiary cover. Mineralisation is most intensely developed along the hanging wall shear, which defines the upper limit of the shear zone, although significant packages of quartz vein arrays and mineralised shears occur sporadically beneath the hanging wall shear.The Macraes gold mine is now in its 25th year of operation, well beyond the projected mine life at the time of commissioning in 1990, and currently contains over triple the measured and indicated resource inventory that was defined at start up. The extended mine life and resource growth has been driven by exploration and resource development success, efficient low-cost mining and processing, improving gold price, as well as an ethos of continuous improvement.The emphasis of Oceanagold’s exploration and resource development has shifted over time; from hanging-wall-focused mapping, soil sampling and step-out drilling, through exploitation of previously drilled stockwork mineralisation, to the pursuit of blind, higher-grade underground targets.Mineralisation within the HMSZ remains open at depth, and the regional potential has not been fully tested. Given the relatively low-grade of gold mineralisation at Macraes, the consideration of tungsten as a supplementary co-product provides an exciting opportunity.CITATION:Moore, J and Doyle, S, 2015. Resource definition in the world-class Macraes gold mine, New Zealand, in Proceedings PACRIM 2015 Congress, pp 557–564 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

The space probe Magellan is on its way to Venus (May, 1989) and with its sophisticated radar systems will discover much more about our twin planet. There is tennuous evidence that Venus once had liquid water. Did it have life? Why was it not stable and why did liquid water not persist through the period of the dimmer young Sun? These are profound questions for us. We understand why Mars froze when volcanism terminated (Just as Earth will freeze one day) but could Earth boil if we continue to add greenhouse gases (Broecker, 1985). What will happen if 10 billion humans continue to use fossil carbon as their main fuel source? The Earth is warming fast and the new satellite data show that the oceans are warming faster than we thought. Is this just a fluctuation or is the greenhouse signal coming through the normal noise of climate?

Jan 1, 1990

By Hudson S. B

With a particular electrode configuration, and a particular combination of electrode voltage and roll speed, a relatively small increase in electrode voltage, or a relatively small decrease in roll speed, resultsin a marked improvement in the separation of zircon from ilmenite. In general, fine minerals can be separated using a higher roll speed, or a lower electrode voltage, than is required to separate coarse minerals. The ionizing electrode should be reasonably close to the point at which mineral is fed on to the roll, and nearer to the roll than the non-ionizing electrode. The optimum conditions for the separation of zircon from ilmenite may not apply for the separation of other non-conductors from other conductors.INTRODUCTIONAlthough the high tension separators used in the Australian beach sand industry are efficient, this efficiency has been gained very largely by a process of trial and error, and not by a systematic study of the effects of changes in the operating variables. The optimum roll speed for a particular electrode position and electrode voltage, and the optimum electrode voltage for a particular roll speed and electrode position, can both be determined quite readily. It is not so simple to determine the optimum electrode position for a particular electrode voltage and roll speed. The reason for this is that the electrode used in high tension separators consists of two parts-an ionizing and a non-ionizing electrode respectively. The angular and radial positions of these electrodes, relative to the feed roll and to each other, affect the behaviour of conductors and non-conductors to varying degrees.

Jan 1, 1962

Nordberg has conducted extensive research, during 1982-85, on the effects of cone crusher variables such as speed, throw and cavity design on the productivity of the crushers. Simultaneously, Nordberg's engineers have developed advanced design and testing techniques that ensure efficient and reliable crusher designs. Combination of this knowledge has resulted in a design of the MPI000 (1000 hp) crusher which fits on the existing 7ft Symons foundation and yet is capable of producing twice the ton- nage of the 7ft. In this paper the development of the MP1000 crusher and its performance compared to the 7ft heavy duty and super heavy duty crushers will be discussed. Also, substantial cost savings resulting from the application of such a high performance machine will be presented.

Jan 1, 1988

By Coin CDA

From a study of coke samples obtained from the tuyere level of four Australian Blast Furnaces, the nature of in-furnace coke degradation has been investigated. At the periphery of the raceway is a concentration of fines and the lump coke appears dull and rounded. However coke from the deadman is angular and relatively undegraded. Cokes made from higher rank coal appear to suffer preferential attack of the reactive maceral derived component (binder). The coke from lower rank coal appears to be attacked non-preferentially by the solution-loss reaction. Initial attempts to simulate these phenomena have given results consistent with these findings. From chemical analysis of the tuyere probe samples there appears to be a relative increase in carbon and decrease in-.sulphur and phosphorous between stockline and tuyere level. An overall decrease in coke mineral matter derived material was noted and associated with this was a significant gasification of silicon. Consequent formation of silicon carbide was noted.

Jan 1, 1981

By Stewart Gillies A D, Just G. D

An internationally recognised and uniform method for classification, categorisation and designation of mineral and energy resources is not yet available. With the increasing need for reliable and comparable coal resource data it is necessary to standardise the traditional classification procedures by quantifying the three basic evaluation criteria of economic feasibility, geologic assurance and recovery. For well documented deposits, geostatistical methods can considerably improve classification quality. A review is undertaken of major classification with particular emphasis on those that incorporate limits on estimation error.A geostatistically based algorithm for classifying coal resources within the current Queensland and New South Wales codes has been developed.Application of the classification algorithm for resources from a number of seams exhibiting different structural characteristics is assessed. The method is found to give classification results that closely reflect the error associated with an estimate of resource quantities based on current sampling densities.lbis requires a careful geostatistical analysis with an emphasis on geological awareness. Resource category restrictions although albitrarily assigned should remain constant for all deposits being compared. This requires some engineering judgement with additional interpretation also required for isolated and peripheral block.

Jan 1, 1990

The closure of the only professional mining school in New Zealand will mean that the minerals industry will have to explore other options to fill their mining professional positions. Globally mining is not seen as an attractive career option for young people and recruitment into mining courses is at a low level. Yet industry demands ever increasing competencies with respect to technology, environmental issues and legislation. This paper addresses this issue by first discussing the attributes required of graduate mining professionals. It then looks at alternative ways on how these can be met internationally and on the home front.

Jan 1, 1997

The criterion for assessing the accuracy of coal reserve estimates proposed by Philip and Watson (1982) is criticized.Following Royle (1977), it is suggested that the global estimation variance found by geostatistical methods is more appropriate.This method is applied to coal data from the Bowen Basin. This shows that two factors (the inherent variability of the variable under study and the total number of drill holes) have more influence over the accuracy of the reserve estimate than the form of the drilling pattern. Comparisons between the relative errors for different sized regions demonstrate that the spacing between drill holes is of secondary importance. The dominant factor is the total number of holes.Comparisons between the relative errors show that some variables such as sulphur need a much denser sampling than the others to obtain the same level of precision.

Jan 1, 1983

By Brimblecombe P

Morwell Open Cut is a continuous mining operation employing 5 buck- etwheel excavators, I bucket chain excavator and 54 conveyors. The combined bunkering capacity at both client Power Stations represents less than 12 hours maximum coal demand. This creates an extremely dynamic operating environment, which is further complicated with significant variations in both excavating and transportation plant capabilities. To achieve set objectives, including- I adequate reserves, 2 coal supply reliability, 3 cyclic plant maintenance, 4 minimal cost of coal, scheduling of the operation requires constant monitoring and reappraisal. Investigations are in progress to develop a computer based scheduling tool capable of simulating the complex operating environment. A review of computer scheduling packages currently available within the State Electricity Commission of Victoria has found limitations making most unsuitable for the task. The type of package found to be most suited is a knowledge based system ('Expert System')capable of operating within a set of rules defined by the user. Work is proceeding on the development of a knowledge base to test the effectiveness of Personal Computer based `Expert Systems'.

Jan 1, 1989

Adsorption of Alkylammoniums in the Interlayer of Montmorillonite and its Effect on the Viscosity of Organo-Montmorillonite Gels

Sep 13, 2010

By B Dunstan, F Wirfiyata

PT Newmont Nusa Tenggara (PTNNT) operates the Batu Hijau copper and gold mine and process plant on the island of Sumbawa, Nusa Tenggara (Barat)  NTB, Indonesia. The plant consists of a nominal capacity 120 000 t/d conventional semi-autogenous ball milling crushing (SABC) circuit followed by sulfide flotation to produce a bulk copper concentrate for sale. Process control is effected by a plant wide distributed control system that overlays an extensive integrated programable logic controller (PLC) framework. The system is enhanced by a supervisory expert control system.Since plant commissioning in September 1999, over US$4 million has been expended as part of a systematic continuous improvement approach to optimise plant control performance. Works completed to date include: redesign and upgrade of architecture of the control system to ensure long-term system reliability, security and upgradeability and to provide a suitable platform for advanced control; integration of supervisory and advanced control tools, techniques and instrumentation; and implementation of sound network communication and plant data reporting tools. This paper outlines the evolution of process control and associated systems and tools that contribute to successful operation and ongoing performance optimisation at Batu Hijau.

Jan 1, 2009

Investigation of the Classification Operation in a Coal Pulverising Vertical Spindle Mill Coal pulverisation in power plants is a major electrical energy consumer. In 2006 more than 41 per cent of world electricity generation was from coal where pulverisers use 0.5 to 1 per cent of gross generation. Therefore, pulverisers are an important target for optimisation not only for reducing costs of power generation but also for reduction of greenhouse gas emissions. A better understanding of the operation of pulverisers is an essential requirement for their optimisation. However, little information is available, other than operating experience, on the performance of pulverisers and how these react to changes in operational variables. This study investigates the effect of changes in coal and airflow feed rates on the classification performance that occurs in an industrial scale ball-and-race vertical spindle mill in which the pulverisation and classification processes are linked together due to the separator classifier being an integral component within the pulveriser. In order to decouple the breakage and classification processes, samples were cut from upward flowing streams through sampling ports drilled on the pulveriser body at different locations. Specific sampling tools were developed. Samples collected from the pulveriser were size and density fractioned to distinguish the differences in behaviour of the components, namely coal and mineral matter. The coal flow rates on dry basis within the mill and around the separator classifier were calculated by mass balancing the multi-component data. The difference in classification behaviour of components during pneumatic transport was confirmed. The response of the circulating load in the mill (~600 to ~1100 per cent) as well as the dependency of fineness of the streams to the operating variables was demonstrated. The approach taken in this study has proved that development of a classification model for a vertical spindle mill pulverising non-homogeneous materials, eg coal, requires treating these materials as multi-component/composite substances.

Sep 13, 2010

The structure and tectonic setting has had a strong influence on gold mineralisation at the Porgera gold deposit. Here, the structural controls on the mineralisation at Porgera are discussed and placed in a regional tectonic context. The Porgera gold deposit is related to the emplacement of the Porgera Intrusive Complex. Prior to intrusive emplacement at Porgera,Papua New Guinea was affected by a major fold and thrust episode which occurred in response to arc-continent collision in the Late Miocene. After crustal shortening the region experienced a relaxation of compression which is expressed in the deformation accompanying mineralisation at Porgera. The first stage of mineralisation (stage I) is hosted by extension fractures, and is spatially associated with exposed intrusive stocks. A later episode of mineralisation (stage II) is hosted by the faults and fractures of the Roamane Fault Zone, which was active as a dip-slip normal fault during stage II mineralisation. Therefore a change in the tectonic environment from shortening to extensional tectonics can be seen at Porgera before and during mineralisation. Rapid fault-slip during stage II mineralisation may have aided high-grade gold mineralisation by subjecting hydrothermal fluids to changes in pressure, temperature, fluid-fluid and fluid-rock interaction. Uplift to form the highlands of Papua New Guinea occurred after mineralisation and was largely complete by 4.0 Ma.

Jan 1, 1995

By C Wu, H Chen

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.The Halasu porphyry copper belt, located in the East Junggar basin bounded by Chinese Altay to the north and the Tianshan mountains to the south in the Central Asian Orogenic Belt, is one of the major porphyry copper belts in Xinjiang province, north-west China. Combined with previous studies in this area, the magmatism can be divided into three periods: pre-mineralisation activity of 390 Ma syn-mineralisation activity of 380–370 Ma post-mineralisation activity of 360–330 Ma.Through the comparison of zircon chemistry from ore-bearing and barren syn-mineralisation intrusions, negative correlation was identified between Ti-in-zircon temperatures and oxygen fugacity, corresponding to the fact that late-stage syn-mineralisation granitoids contain high water content, high oxygen fugacity and low temperatures with higher mineralisation potential. In addition, the relative low initial 87Sr/86Sr ratios, high eHf(t) and eNd(t) values and mantle Pb isotope characteristics in this study support that the magma forming these intrusions was probably derived from juvenile crust generated during subduction-accretionary processes.CITATION:Wu, C and Chen, H, 2015. Zircon trace elements and Sr-Nd-Pb-Hf isotope systematic of the Halasu porphyry Cu belt, north-east Xinjiang, China, in Proceedings PACRIM 2015 Congress, pp 637–640 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By J Ward, B Rohrlach, B Rosero, J Silva, O Poma

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Alpala copper-gold deposit is a recent, high-grade porphyry Cu-Au discovery located in the Imbabura Province of north-western Ecuador. The deposit lies along the crustal-scale Chimbo-Toachi Fault Zone within the Dagua-Piñon terrane, which is an oceanic plateau accreted to the South American convergent margin in the Late Cretaceous. The deposit is hosted by quartz diorite stocks that intrude andesitic volcanic breccias of the Oligocene to mid-Miocene San Juan de Lachas Formation. Miocene-age calc-alkaline plutonism is associated with porphyry Cu, Cu-Mo and Cu-Au deposits in southern and northern Ecuador. The Alpala deposit lies along a sector of the Miocene arc that has recently been underplated by the Carnegie Ridge seamount chain that induced shoaling of the subducted Nazca plate beneath northern Ecuador.Surface expressions of the deposit were recognised in May 2012 during follow-up of stream sediment anomalies, when outcropping sheeted and stockwork porphyry-related veins were discovered in Quebrada Alpala. The roots of a NW-trending, structurally-controlled lithocap were recognised over an area of 4.5 × 0.9 km. The remnant lithocap exhibits well-defined mineral zonation mapped by TerraSpecTM analyses on grid soil samples. Soil sampling, heliborne magnetic surveying and channel sampling defined initial drill targets.Seven diamond drill holes were completed in the year from September 2013. Drill hole CSD-13-005 intersected 672 m grading 0.93 per cent Cu and 0.91 g/t Au in high-temperature, inner propylitic and locally potassic-altered quartz diorite intrusions. Overlying hydrothermal clay alteration assemblages define the base of the lithocap. A NW–SE trending footwall structure defines the south-west margin of the deposit. Drill hole 5 intersected high-grade sheeted ‘B-type’ and ‘C-type’ veins (Gustafson and Hunt, 1975) that lie along the south-west margin of an 1100 × 500 m magnetic anomaly that is the focus of ongoing exploration.CITATION:Rohrlach, B, Poma, O, Rosero, B, Silva, J and Ward, J, 2015. High-grade porphyry copper-gold mineralisation in north-west Ecuador – The Alpala Cu-Au porphyry discovery , in Proceedings PACRIM 2015 Congress, pp 369–376 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Sjaw WJ

Conditional simulation is a set of geostatistical tools that is becoming popular as powerful personal computers make the use of these tools less costly. The more familiar set of tools for spatial estimation has a number of varieties (eg Ordinary Kriging, Simple Kriging, Multiple Indicator Kriging, etc) each suited to particular solutions of the problem of estimation, for example predicting the average grades of blocks in a region from more or less sparse data. Similarly, conditional simulation has a number of varieties, discussed in this paper, which in various ways address the problem of characterising the variability of a deposit between the known data locations.Conditional simulation can provide a number of equiprobable images of a deposit, at a finer resolution than would be economic or practical to sample, and that can be constrained by various criteria (which may be geological, statistical and geostatistical), to ensure that the images reasonably represent the deposit. These images can then be used to assess the risk involved in various practical mining decisions. Examples are provided where conditional simulation has been used for validating resource estimate parameters, optimising grade control sampling grids, and for ore block optimisation for mining grade control.

Jan 1, 1997

By Lonie W. M

The rapid development of the Australian steel industry over the past twenty years has greatly increased the demand for coking coal from the collieries owned by the Broken Hill Proprietary Co. Ltd. and Australian Iron & Steel Ltd. This in turn has called for an intensive and continuous programme of colliery expansion and new colliery development, along with the reorganization and modernization of existing collieries.This paper presents a general description of the factors involved and the techniques used in planning modern colliery development for the steel industry.PRELIMINARY GEOLOGICAL INVESTIGATIONSIn any colliery development, preliminary geological investigations require a detailed and practical knowledge of the geology and characteristics of the coal-field as a whole. In the early stages of the investigations, probably the most valuable information is obtained from outside the particular area under review, rather than within it, and unless the geology of the coal-field is understood, the projection of the known information into the unknown area cannot be carried out with certainty.Because development of the coal seams from the outcrops has been an apparently simple matter and not subject to the risks involved in deep mine development, the geology of the New South Wales. coal-fields has not received the attention that major mineral resources warrant.Only the most accessible regions of the coal measures have been generally prospected, while the potential areas remain...

Jan 1, 1957

Cessation of mining on the Bendigo goldfield makes it evident that, as the older generation fades away, knowledge of the famous Bendigo saddle reefs will be limited in the future by their written records. It is important therefore that the summarised account by D. E. Thomas (1953) in the Geology of Australian Ore Deposits should not be misleading. Fig. 6 in this article is stated to portray a cross section and longitudinal section through a series of gold shoots in the Garden Gully 300 ft. reef. The gold shoot along the capof the saddle reef is represented as extending down the east leg in a series of prongs, with the tips of the prongs about 50 ft. apart. It is the purpose of this note to indicate that this illustration can be suspected to be a diagram of the old stopes instead of a diagram of the distribution of gold in the quartz.The original sketches of Figs. 6 and 7 in Thomas' account were extracted, I believe, from the field note books of H. S. Whitelaw, years after his death in the late twenties. Whitelaw was stationed in the Bendigo office of the Geological Survey of Victoria, carrying out geological surveys of the Bendigo mines. He was there for many years before the Gold Research committee started its investigations in 1916 and he was acutely aware of the problem attached to the distribution of gold in the reefs. He had felt concern that manyauriferous reefs were being mined without adequate study and record and he decided, as he expressed it to me, to pick up what he could as he went along. There can be little doubt that the diagrams of Figs. 6 and 7 are products of this resolve.Opportunities to investigate gold occurrences at Bendigo were limited before 1916 because the field was operated by Manuscript received at The Institute 18th November, 1960.

Jan 1, 1961