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By Feebrey CA, Duncan RA

The Ebor Volcano in northeastern New South Wales is an eroded example of a central-type intraplate volcanic-intrusive complex. It is of Miocene age (19-20 Ma) and has similarities to other central-type volcanoes in eastern Australia which may represent manifestations of sub-lithospheric hotspot activity. Thick lava flows are exposed around the Great Escarpment and are dominated by a tholeiitic basaltic suite, ranging from ol-tholeiite to qz-tholeiite to icelandite with ages of 19.2-19.6 Ma. On its western edge, the tholeiitic lava suite probably overlies remnants of basanite flows belonging to the Eocene (-48 Ma) Doughboy province, but elsewhere, minor alkaline basaltic lavas may be coeval with the tholeiitic suite. Several felsic bodies were emplaced into the volcano at -19.0-19.2 Ma and include subalkaline and peralkaline types. The Crescent Complex is a Miocene-age, strongly differentiated mafic to felsic intrusion in basement rocks and centrally located in pre-erosion reconstructions of the Ebor Volcano. It is interpreted to be a major feeder for the tholeiitic lavas based on age and composition. Evolution of the dominant tholeiitic suite proceeded from a parental ol-tholeiite magma, through qz-tholeiite, icelandite and small volumes of felsic rocks by fractionation of plagioclase, olivine, clinopyroxene and titanomagnetite, accompanied by enrichment of SiO2, F,FeO/MgO, alkalies and HFSE.

Jan 1, 1995

By Bourne R. W, Smith T

This paper presents initial findings of a project examining novel processes for the treatment of refractory sulphidic gold concentrates. Non-oxidative roasting of such concentrates for 12 hours at 750¦C resulted in the finely disseminated gold agglomerating to form discrete grains. The pyrite and arsenopyrite decomposed to form pyrrhotite, whilst the labile sulphur and arsenic driven off was collected on a condenser as a mixture of elemental sulphur, metallic arsenic and various arseneous sulphide compounds. As a result, the cyanide solubility of the gold contained in sulphidic refractory gold concentrate from the Emperor mine in Fiji improved from 54.5 per cent to 98.4 per cent; from the Fimiston mine in WA (65.2 per cent to 96.6 per cent), from the Windarra mine in WA (69.6 per cent to 91.3 per cent), from the Harbor Lights mine in WA (20.4 per cent to 60.7 per cent), and from the Wiluna mine in WA (12.6 per cent to 28.0 per cent). The non-oxidative roasting conditions have not been optimised for each of these minerals. Subjecting the non-oxidatively roasted minerals to mild oxidative acidic iron sulphate pressure leaching (with typical temperature of 100¦C and typical oxygen overpressure of 500 kPa) to remove iron and so further liberate finely disseminated gold, resulted in the cyanide solubility of the gold exceeding 96 per cent for each of these five concentrate types (including those from Harbor Lights and Wiluna). Thiourea leaching of the sulphur-rich residues under acidic conditions resulted in remarkably high gold extractions being achieved. These novel processing options need to be optimised, and their economic viability established.

Jan 1, 1991

By Gillies A. D S, Lee A. H

Water is an integral component of a mining operation. To-date water management has received a low profile in the overall management of mining operations. To cost effectively meet the requirements of government environmental legislation the man

Jan 1, 1994

The Koongarra uranium deposit was discovered in August 1970 by Noranda Australia Limited. Denison Mines Limited acquired the rights of ownership in October 1980 and has continued the 'struggle' to bring the proposed mine, containing approximately 13 300 tonnes of U308 of Indicated ore and having a value of $1 billion (1984 dollars), into operation. During the 14 years that have passed, the owners have found it necessary to deal with numerous Federal, State and Territory government departments, aboriginal representatives, handle thousands of communications, attend and convene countless meetings and spend millions of dollars. This paper addresses the history, the requirements, the problems and the costs to date for what - no return.

Jan 1, 1984

By Scott SD

The 1986 PACLARK Expedition established that propagation of a seafloor spreading zone into continental crust has created a complex series of volcanic basins on the floor of the Western Woodlark Basin. In addition to abyssal basalts, felsic volcanic rocks were recovered - especially at the leading edge in the extreme west. A recent deposit of hydrothermal Fe-Mn oxides was discovered on an axial seamount of basaltic andesite, and seawater plume anomalies suggest current hydrothermal venting elsewhere. As a modern analogue for the settings in which ancient volcanogenic massive sulfide orebodies probably formed, the Western Woodlark Basin warrants further investigation.

Jan 1, 1987

Grade control plays an essential role in the good running of a mine. The factors at play are many, starting from a good analysis of the geology and a correct sampling procedure. Once this is achieved (and it is an essential prerequisite), the problem is to adequately define what is ore and what is waste. This paper tries to show, through a small example, how simple geostatistical techniques (variography, and moving average or kriging), can help in accurately defining these limits in a geologically homogeneous zone, thus allowing optimal use of the available information.

Jan 1, 1987

By Chapman J, Kanchibolta S. S Poetschka N L

A field study was undertaken at Marandoo iron ore operations to investigate the effect of blasting on the lump/fines ratio. Three blasts, each in a different ore domain were monitored and the blasted ore was subsequently audited through the tr

Jan 1, 1998

Ore textures in Australian BIF-derived ores are quite complex and have formed the basis for ore genesis models, which includes hypogene upgrading or supergene upgrading then regional metamorphism for the microplaty hematite ores and supergene upgrading for the martite-goethite ores. Despite a high level of ore texture knowledge, little is known about the spatial distribution of ore textures within deposits or their relationship to downstream processing. This paper describes a new iron ore texture classification system to better understand the vertical textural zonation characteristics of Australian BIF-derived deposits, the interpreted role of recent supergene upgrading processes on modifying primary ore textures and their implications for downstream mineral processing. The iron ore textural classification scheme presented uses textural groupings defined on the basis of similarities in mineralogy, ore texture, porosity, mineral associations and hardness. The scheme is non-genetic and has been successfully applied to deposits in the Pilbara, Yilgarn and Gawler cratons. The main ore texture groups include dense martite/hematite, microplaty hematite, microplaty hematite-goethite, martite-goethite, goethite-martite and goethite-rich. Each group can be further subdivided into physically hard to softer subcategories. The ore textural groups can be divided into those interpreted to be associated with primary replacement of BIF and secondary textures resulting from more recent modification by near-surface hydration or dehydration processes. A schematic vertical section through BIF-derived deposits consists (from surface) of detritals underlain by a carapace, both of which may have been eroded, followed by a hydrated zone with replacement of primary ore martite and microplaty hematite by vitreous goethite. The hydrated zone is underlain by 0.2 - 6 m thick zones of intense dehydration and textural infilling of porosity with hematite and hydrohematite. Immediately below the dehydration zone is a strong zone of leaching, where more porous and friable ore textures occur, followed underneath by a gradational contact with primary ore. Secondary supergene processes can impact on beneficiation with hydration and leaching resulting in more difficult density separations at the concentrator stage due to reductions in density differences between ore and gangue and loss of heavy media into pores. Supergene modification of primary BIF-derived ore textures can substantially change lump metallurgical properties, with hydration and dehydration favourably increasing lump yield but reducing resistance to thermal shock whilst leaching will give the opposing outcome. The lump properties of ore textural groups appear to be relatively consistent within and between the iron ore deposits examined.

Jan 1, 2002

By L Basnayaka, N Subasinghe, B Albijanic

"It has been recognised that the presence of clay minerals in ores adversely affect flotation performance. In this study, changes in rheological properties of the flotation pulps under normal operating conditions were studied with additions of bentonite and kaolinite clays at various concentrations. Zeta potential measurements were also carried out to determine the changes in surface charge due to adsorption of clay particles. The results showed that bentonite clay adversely affects floatability of pyrite while kaolinite clay had a lesser influence on flotation of pyrite. The addition of Ca2+ ions to the pulp containing bentonite modified the rheological characteristics and in turn improved the pyrite flotation. It was also observed Ca2+ ions suppressed the swelling properties of bentonite and altered surface charge properties of bentonite clay particles. It has been shown that the flow index affected the ultimate recovery and it may provide a means to monitor flotation performance in routine plant operations.Citation:Basnayaka, L, Subasinghe, N and Albijanic, B, 2016. Effect of Clay Rheology on Flotation of a Refractory Gold Ore, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 77–84 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By Waters JC

Pseudoclastic hydrothermal alteration textures occur within quenched coherent dykes forming part of a subaqueous dome complex (-4 Ma) on Ponza Island, Italy. These textures are similar to those observed in considerably older (-500 Ma) subaqueous volcanic rocks at a number of localities throughout the Mount Read Volcanics in Tasmania and elsewhere in ancient volcanic sequences of this type in Australia. This is significant because the processes of formation, hydrothermal alteration and secondary mineralisation of ancient volcanic sequences may be better understood if we can make comparisons with modern analogues. Observations at Ponza imply that these pseudoclastic alteration features form synvolcanically or immediately after dyke emplacement and lava extrusion. This is compatible with scenarios presented for their formation in ancient sequences in the Mount Read Volcanics, Tasmania.

Jan 1, 1995

The ore reserves of the Frieda porphyry copper prospect in Papua New Guinea have been estimated using kriging and an alternative method. Only very erratic variograms could be obtained from the raw data and thus it can be expected that kriging variances will be unrel- iable. The frequency distributions of the two sets of estimates show expected differences and the resulting mineable reserves show similar expected differences. More drilling and the use of disjunctive kriging are needed to produce reliable estim- Ates.

Jan 1, 1979

By Melcher G

The challenge to the zinc industry is shifting from maximum metal recoveries to the environmentally safe processing of the ore concentrates. The main source of solid residues from hydrometallurgical zinc processing is the iron content of the concentrates. Unfortunately iron precipitates from leach liquors contain various compounds which cause them to be considered as environmentally unsafe, unless they have been cleaned in subsequent process steps. This calls for separating the iron from hydrometallurgical processing as early as possible. For this purpose a process has been designed to eliminate the iron directly after neutral leaching the calcine. This is being done by direct smelting the neutral leach residue with a cyclone/top blowing unit. The zinc is recovered from the neutral leach residue as a metal oxide to be recycled to the zinc process. The iron is converted to a slag, which is resistant to atmospheric attack. Key data of the integrated hydro-/pyrometallurgical process are presented as derived from pilot plant tests by cyclone smelting and top blowing the slag.

Jan 1, 1993

By Mozley R

Contaminated sediments are a multinational problem. A crucial factor in solving an environmental problem is knowledge of, not only the amounts of polluted soil, the contaminants involved and their concentration, but also the historical background of the problem. Processing polluted soil is a tailor made activity based on rational decisions resulting from a detailed treatability study. Lack of information about characteristic properties of a specific sludge/pollution combination is the main obstacle in the route from first ascertaining that a particular harbour subsoil is polluted, to final identification of the full scale treatment plant. In the first instance, information must be generated regarding the distribution of pollutants in relation to the distribution of the original geophysical components. Based on this information rational decisions can be made on separation at a particular cutpoint and what sequential techniques should be involved for a certain fraction. For this purpose a `fingerprint method' is presented especially developed for investigation of polluted soil and sediments. The heart of the fingerprint method is a series of sequential hydrocyclone separations, by which a series of products is generated. The objective of the fingerprint method is to select an optimised treatment procedure in which the pollutants are concentrated in as small a volume of material as possible, leaving the bulk of the material clean. The pollutants can then readily be destroyed or isolated from the environment. The philosophy and advantages of the fingerprint method are demonstrated for a harbour sludge containing heavy metals as main pollutants. Hydrocyclone separation combined with flotation of both the coarse and fine fraction resulted in reusable and dischargeable products. Flotation of the fraction of fines was carried out by means of an experimental flotation cyclone enabling the selective recovery of mineral particles with diameters less than 10 microns. The overall conclusion is that design and engineering of treatment flow schemes for polluted dredged materials is a tailor made activity based on rational decisions resulting from the fingerprint information.

Jan 1, 1993

This paper gives a first-hand account of what a graduate mining engineer can learn by visiting Atlas Copco in Sweden and gives reasons why all mining engineering students should apply for this excellent scholarship. It will also (attempt to) refute the authorÆs mine managerÆs claim that the trip was a huge junket.

Jan 1, 2006

By Orid A

A fast, non-contact technique for measuring sizes of rock fragments on a conveyor belt is presented. An image processing technique called active stereopsis is used which makes use of a light stripe projected on to the surface of the fragments on the conveyor belt. A CCD TV camera is used to capture the shape of the distorted light stripe. the video image of this shape is then processed by a computer program so that the 3D profile of the surface can be obtained by triangulation. The sizes of the rock fragments are then calculated from this profile. The speed of the technique is improved by calibrating the light stripe system before measurement begins so that the profile of the fragment surface can then be measured using simple geometry. The technique is fast and highly parallel so that it is able to operate in real time.

Jan 1, 1990

Recent developments in engine, transmission and control technology, likely to give rise to improved performance and efficiency of underground mobile equipment, are reviewed. Turbocharging and the electronic control of fuel pumps and injectors can improve diesel engine performance whilst minimizing exhaust emissions. Ceramic materials promise further improvements in engine efficiency. Nevertheless, electrically powered machines, equipped with trailing cables or 'travelling plugs' are expected to find increasing application where there is less need for flexibility and where the cost of ventilation and heating or cooling makes diesel engines unattractive. Voltage to frequency converters and induction motors appear to have a future in mains powered machines. Vehicles employing energy storage in the form of batteries or flywheels will find increasing application, but it is expected that they will remain a minority until there is a significant break-through in battery technology. Hydrostatic transmissions having high power density and efficiency are likely to be used more widely. Electronic control systems are likely to be used to simplify jobs and to improve performance and productivity. Enhancement of remote control systems is to be expected for work in unsafe areas, but true robot operation is considered unlikely for the moment. Attention to ergonomic factors should produce significant productivity gains.

Jan 1, 1985

The effects of changes in sintering bed height, coke fuel, suction and basicity on sinter productivity, physical strength and mineralogy were determined. It was found that, for a given iron ore, there is a narrow -coke range which maximises sinter strength, irrespective of bed height (in the range 300 to 500 mm) or basicity (in the range 1.2 to 2.2). Increases in bed height, at a constant coke level, improved the physical strength of the sinter. Productivity increases were obtained by increasing the sintering suction but, at coke levels other than the optimum, these *ere somewhat offset by the decrease in sinter physical strength. At basicities higher than 1.2 (i.e. 1.6, 1.8 and 2.2) there was a narrowing of'the size range of product sinter, with a decrease in the percentage of top size material, and a decrease in the amount of fines produced. Changes in coke, bed height and basicity exert major effects on sinter mineralogy, while the Nagoya index was mainly influenced by cote and bed height Changes.

Jan 1, 1975

In process industries, time-dependent random fluctuations of raw material characteristics and mass flow rates in bulk material or pulp flows cannot be always prevented for different reasons, eg because of the geological situation (no uniform formation of the deposit) or/and because of technological reasons (segregation in bunkers or on stockpiles). Since a long time, there has been practical experiences that such fluctuations can have negative consequences, eg: ò fluctuations of the final products characteristics, ò higher expenditure for process control, and ò worsening of technological characteristics (recovery, sharpness of separation etc). In the literature, there can be found a lot of details as to, eg the improvement of the sharpness of separation in a jig in dependence on the raw material blending (Kubitza, 1981; Gathen, 1983) or the decreasing flotation recovery with increasing raw material characteristics fluctuations in iron and potash ore processing plants (Bubnova, 1978). Up to now, however, these consequences of random fluctuations, eg on the separation efficiency were not predictable theoretically. It could be shown by means of the general model for mechanical macroprocesses (Graichen, 1989), that the reduction of input fluctuations passing a blending facility can be calculated in this way. In this example, the steady state of the process is the wanted one, but, in general, the model is able to describe also non-steady states of the process regarded. On the other hand, the general model of mechanical macroprocesses has been used successfully for modelling separation processes, eg cross-flow and air classification (Molerus, 1969; Neesse, 1991; Senden, 1979; Tichonov, 1973). That is why it was tried to model the influence of input fluctuations on the separation efficiency, that means, the impact of non-steady states - as a consequence of random fluctuations - on a separation process. The models discussed in the literature are related nearly exclusive to the steady state of the process. The reasons for that lie in the (relative) simplicity of the models and the fact that the steady state is aimed at by means of blending processes under practical conditions - because of the advantages mentioned above. These models cited have proved to be superior to other models, since the basic general model for mechanical macropocesses makes possible the consideration of turbulence acting in the process unit and influencing the separation process essentially. This is valid also for modelling the turbulent cross flow classification, applied to mechanical classifiers and hydrocyclones, where the correspondence between the separation characteristics (cut size, separation sharpness) calculated and determined experimentally is much better than for other models.

Jan 1, 1993

Proposals designed to use stockpiles and buffer stocks to achieve price stabilization and better resource use have a long history. They are super- ficially simple to understand. The benefits seem clear. And yet I am well aware that this is not a simple subject: the more one studies it, the more complex it becomes. Worldwide interest in re- source management, while receiving fresh impetus from the OPEC actions, also has a long and chequered history. Those venturing into such ter- ritories must be forewarned of the traps and pit- falls which abound. Interest in these schemes has waxed and waned over the years with the fluctuating fortunes of the producers or consumers. As I write this paper towards the end of 1977, I am acutely aware of the low ruling prices for zinc, copper, and nickel. These sacrifice prices remind me that it is difficult, for example, for a surveyor, to be calm and rational if he is up to his neck in a swamp full of crocodiles. He might be forgiven for forgetting that the aim was to drain the swamp! I am also aware that when swamps are drained, painful and dangerous stumps sometimes stick out. Hence, in looking at the subject of stockpiles and resource management we must not set our sights too high, perhaps not initially hope for perfec- tion, if we want to secure worthwhile changes. My approach is to acknowledge a bias for the market system. We have, however, had experience (remember the 1930s) of some weaknesses in the untrammelled operation of free markets. Thus our international economic relationships over the past 20 or 30 years have been based on a desire to retain as much as possible of a liberal world trading system backed by such organizations as the GATT, IMF, and the U.N. to ensure the necessary cooperation. Some nations have seen this system work only partially in their best in- terests. GATT, for example, has been reasonably effective in liberalizing trade in many manufac- tured goods but far less so in regard to agricultural or semi-processed goods.

Jan 1, 1978

By Ehlers HK

Mount Isa Mines Limited has 25 rod and ball mills of various sizes installed in two Concentrators at Mount Isa. A continuing investigation into installation, design and materials of liners for these mills has been in progress since the early sixties. Both manual and mechanical methods of liner installation are used and described. Materials for the various applications have been evaluated, mainly by field trials. Design of liners has also been evaluated by field trials and the history of trials in No.4 Concentrator is given. The purpose of the investigation has been to reduce the cost of mill lining and the life of many linings has been greatly increased as a result of this work.

Jan 1, 1978