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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

I In an optical microscope, mild attack by cyanide solutions on various minerals can be observed by means of colour changes as well as etching patterns. However, the mineral may not be identifiable due to the coloured film. In some cases, a transfer algorithm between mechanical stages enables the surface-altered mineral to be identified in the SEM. A more severe attack may not be so informative, as it is not known whether the mineral attacked has been completely dissolved away. The leaching behaviour of some common minerals is described.

Jan 1, 1991

The care necessary to ensure a reliable estimate of average value from the individual values of a series of bore holes sunk in any alluvial deposit containing coarse gold was well exemplified in checking over the mining returns from a previously bored deposit in Central Otago, N.Z. While the working returns are always liable to vary considerably from bore values in any particular sub-section of an area, still, over any considerable area, the two must check within small limits, if profits are to be calculated and capital raised on the average value given by boring.The present figures have probably more value than those from, dredge returns since accurate measurements are difficult to obtain in irregular water-filled dredge paddocks, whereas in the case under review the paddock walls stood almost perpendicular, and, as the measurements were taken and checked in the empty rectangular excavation, the yardage estimate may be taken as substantially exact.NATURE OF DEPOSITThe area consists of a narrow valley deposit of fluvio-glacial origin, the original deposit having been eroded and the gold reconcentrated by post glacial rivers. The wash is between 80 and 90 ft. deep, and is formed in two distinct layers:(i.) The top layer from surface to 70 ft. or 80 ft. consists of about equal quantities of gravel mixed with glacial drift, and a small amount of clay. The gravel is typical discoid glacial stone of a maximum size of about 4 in. diam. by 1 in. thick, and consists of soft micaceous schist and laminated slate. This upper layer of wash contains no coarse gold whatever, and very little fine; indeed, in mining, the top 30 ft. is discarded without being passed over the boxes.(ii.) The lower layer of wash to bedrock is similar to the upper, except iihat it contains about 10% of larger discoid stone up to 12 in. diam. by It in. thick; 90% of the gold is concentrated in this bottom layer.

Jan 1, 1929

With the advent of the resources boom in the late-1960s most of the larger scale resources projects in Australasia were commissioned on an æowner miningÆ basis, where the mine owners owned and operated the primary mining equipment. Then, in the 1980s with the arrival of the gold mining boom in Western Australia and elsewhere, a change occurred û most of the mining activities were carried out on a contract mining basis. Over recent years, however, there has been a marked trend amongst larger Australasian open pit mining operations back towards owner-controlled and operated mining operations. The reasons for this are many and are addressed in the paper, but centre on the concept of the owner being prepared to assume more of the mining risk in exchange for the advantage of not having to pay a contractorÆs profit margin. Where mining contracts are entered into, the older æschedule of ratesÆ format is being replaced with less adversarial and more entrepreneurial contract alternatives involving operating cost and risk sharing in a spirit of æfair dealingÆ. Leasing and maintenance issues have also been influenced in recent years by the advent of more flexible contract arrangements with equipment suppliers. Group purchasing has also had some influence for project operators. For many mine owners, the optimal risk management profile involves a practical offsetting of the assumption of mining risk on the one hand, against the removal of litigation risk and potentially reduced operating costs on the other. Potential pitfalls may arise where equipment size and type requirements vary with time or where manpower management, mining flexibility, job skills or safety exposure factors are relevant. These issues are commented on in the context of some well known examples, and an update is provided on contract mining versus owner operation in large-scale Australasian open pit mining generally.

Jan 1, 2002

Recent well-publicised problems with the start-up of new mining projects have continued to feed the perception that the mining business in general and Ore Reserves in particular are a poor risk. New mines commonly experience difficulties when the true variability of ore characteristics becomes apparent during commissioning. At this critical stage, the impact of lower metal recovery, reduced throughput or increased consumption of reagents and energy can have a catastrophic effect on economic returns, as illustrated by the premature closure of some operations. There appear to be several common reasons contributing to the poor performance of mining projects, of which three are examined here: lack of early risk assessment before feasibility studies are started, inadequate sampling for metallurgical test work and variability of the run-of-mine (ROM) ore. An underlying feature of these issues is the lack of effective interaction between geologists, mining engineers and metallurgists/ process engineers. Geologists need to be more aware of ore processing issues and the range of characteristics that need to be considered as part of the resource estimate. Metallurgists need a greater understanding of the variability of the run of mine ore in terms of all the characteristics that influence the design and operation of the plant. Mining engineers need to determine the short-term variability of the ore in the mine schedule, so that there is confidence that the quality of the run-of-mine ore will be within the design specifications of the plant. A substantial overlap between these disciplines and sharing of areas of responsibility is necessary if these and other technical problems are to be better understood, production estimates are to be improved and commercial risks are to be reduced. Although the JORC Code (1999) provides guidelines for reporting all the issues that are material to an Ore Reserve estimate, some issues are rarely fully addressed in Ore Reserve reports. In particular there is no formal requirement for a metallurgist to assure his or herself of the appropriateness of the Ore Reserve classification. Consequently the level of uncertainty related to recovered grade and ore processing characteristics may be understated. It is suggested that to meet the concerns of bodies funding new mineral developments a stronger multi-disciplinary approach to the analysis of mineral deposits and reporting of Ore Reserves is required. The culmination of this approach would be the formal requirement for a geologist, mining engineer and a metallurgist to co-sign Ore Reserve reports.

Jan 1, 2002

By Rienks, Wyborn D

The Ravenswood Batholith in the Charters Towers -Ravenswood area of north Queensland, was formed by three main episodes of granitoid emplacement between the Early Ordovician and the Early Permian. Granite to granodiorite plutons of the first phase of intrusions in the Early to Middle Ordovician, probably formed by partial melting of a thin continental crust as a result of the emplacement of mafic material derived from the mantle. Some of this mafic material subsequently intruded the Ordovician granitoids as gabbro to diorite complexes. The early granitoids were deformed and metamorphosed prior to emplacement of second phase granodiorite to tonalite plutons in the Late Silurian to Early Devonian. These later plutons have generally not been deformed or recrystallised. Geochemical and isotopic data suggest the Siluro-Devonian plutonism may have been generated by a partial melting of the tholeiitic material emplaced in the lower crust during the Ordovician. A third intrusive phase consists principally off Late Carboniferous to Early Permian gabbro-granite complexes, high level granite to granodiorite complexes, and rhyolitic plugs and diatremes near the batholith margin. Gold mineralisation in the batholith is associated with two major events: mesothermal vein formation in the Early Devonian and porphyry types in the Late Carboniferous to Early Permian.

Jan 1, 1990

Industry has a very special request to make. Environmental issues must not be allowed to become a factor of competition so that nations or individual industries can gain economic advantages for themselves by encroaching unduly upon the environment. An international harmonisation of the demands imposed on specific industries and industrial plants where discharges are concerned is therefore essential. The same applies to any to any action contemplated against noxious products. An important step towards that goal is no doubt represented by the United Nations Conference on the Environment scheduled for 1972. Conclusions: Australia must recognise its responsibilities in an inter- national movement to control pollution. It must react on a national scale to a problem which is threatening our whole national environment. To gather, collate and coordinate the information needed to ensure policies which strike a balance between conservation and development, we must look towards the Commonwealth to coordinate the activities of its own instrumentalities and those State and independent bodies working in the area. Financial aid must be provided to stimulate research and later to ensure that environmental protection policies are observed. These policies will be founded on social economic theories which will be both practical and sound, The United Nations conference on the Environment is scheduled for 1972 and in this is the opportunity for international cooperation. Cooperation in the field of controlling legislation and the collection of much needed data. There is an imperative need to assemble facts for world use - an international know-how bank which acquires the most sophisticated technology of process design and waste purification. Arising out of this Conference, is it too much to expect that there could be established an international authority for environmental control, whose activities are governed on a multi-national basis? Such an organisation would have as its primary concern the collection and classification of official regulations, as well as the sheer collation of data to permit economic evaluation of the costs of conservation of the environment. There is an international scope with different factors involved, including industrial technology: in other words, the concrete measures taken against industrial pollutants ought to be more or less identical for similar industries irrespectives of the countries in which they operate. The assembling of an international common foundation of knowledge is imperative so as to acquire the most sophisticated technology of process design and waste purification available for all who are interested.

Jan 1, 1971

By Christie AB

Stream sediment geochemical analyses from 140 mining company exploration surveys of the Coromandel, Northwest Nelson, Marlborough and Westland regions of New Zealand have been compiled from open file reports and entered on a database called REGCHEM (for Regional Exploration GeoCHEMistry). REGCHEM is supported by GEOEXPL, a custom-written computer software application which operates under the Microsoft Access relational database mangement system on a PC-type computer. The data are plotted as maps using the Maplnfo geographic information system (GIS) package. Thesholds separating anomolous values from background values are determined using the PROBPLOT univariant statistical package, which enables the descrimination and modelling of several populations. Relevant REGCHEM data are being incorporated into a GIS for the Coromandel region as part of ongoing studies to sevelop mineral deposit and metallogenic models for the region, and to assess regional prospectivity.]

Jan 1, 1995

By Estoque J, Abaigar J, Domingo B, Acenas M

The Siana gold-silver deposit of Surigao del Norte, Mindanao, Philippines is perhaps one of the most complex in the world, being related to an ancient suture zone known as the Philippine Fault. Early accounts described the deposit as epithermal, consisting of an upper limestone replacement orebody and a lower vein type deposit hosted in andesite. Recent field and laboratory studies, in correlation with the latest findings on the archipelago's tectonic evolution, however, led to the present interpretation of the Siana ore deposit's origin as involving both syngenetic and epigenetic processes, with limestone breccia, similar to the Cow Head Breccia of Newfoundland, as the principal host to mineralization.

Jan 1, 1987

Secondary steelmaking (or ladle metallurgy) has been developed as a post- steelmaking ladle treatment to produce steel of superior quality. Its rapid growth has resulted from quality improvements, productivity increase, operational flexibility and process route economics. Advances in secondary steelmaking are very impressive during the past decade, and many commercial systems have been developed for performing one or more of the following unit operations: degassing, atmosphere regulation, reheating, refining with synthetic slag, rinsing gas treatment, injection of solid materials and alloying. The metallurgical requirements imposed by the current competitive steel market include more precise analysis tolerances, minimum level of detrimental elements, improved cleanness, demanding service performance and better processability. In most cases, these requirements could only be realized by the application of appropriate secondary refining facilities. Continuing developments in simplicity of design, cost advantage, quick cycle time, improvements in peripheral services such as refractories, instrumentation and in-situ analysis, extensive exploration of new applications, and the use of computer, can be expected. An exciting future is predicted for the widespread adoption of secondary steelmaking to perform most of the major refining functions over a variety of steel quality. It will also become a vital link in the total steelmaking process for production of tonnage steel at the large integrated steelworks and the mini-steelmills.

Jan 1, 1986

By Moore A. J

Control of blast vibration requires that its nature and causes be understood, and that effective control procedures be implemented to ensure compliance with limits related to the probability of damage to buildings/structures and human discomfort. This paper covers measurement equipment, assessment and prediction techniques, blast vibration control procedures and applicable statutory limits. It reviews current practice, and provides information on recent developments in blast vibration measurement equipment and control techniques, using examples based on Hunter Valley mining practice.

Jan 1, 1995

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 Askew J. E

All facets of current practices of cable dowelling at The Zinc Corporation, Limited and New Broken Hill Consolidated Limited are re- viewed. This includes materials specific- ations, installation practices and design pro- cedures. Cable dowelling for cut and fill stoping, square set timber stoping, longhole open stoping and level reinforcement is considered. Installation is simple and can be mechanised to eliminate heavy lifting. Quality control is essential for optimum performance of the re- inforcement. Design patterns must consider the mining method, reinforcement economics, acceptable stability standards and mine production priorities.

Jan 1, 1977

Among the various methods of thick-seam mining already well-tried in practice longwall caving with extraction of a single slice, as thick as possible, abandoning the top and/or the bottom coal, seems to be the most suitable one for the Australian coal mining industry. The production units of the future should be equipped with heavy double-drum shearer-loaders, wide armoured conveyors, (with one or two central chains) and shield support. Material of this type has been developed for seams up to 6 m thick. Output figures of more than 6,000 tROM/d from a single face can be looked upon as a quite realistic expectation. The problems of co-ordinating such large production units with the whole layout of the mine are discussed. The factors to be taken into account in the planning work and for preven- tion of mine fires caused by spon- taneous combustion are dealt with. For economic reasons the highest possible utilization factor of the very expensive equipment must be aimed at. Furthermore, the seams or parts of seams to be extracted should be carefully selected.

Jan 1, 1976

By I D. Hair

A numerical groundwater model was used to predict the nature of interactions between heavy mineral sands mining operations and the groundwater regime at North Stradbroke Island, Southeast Queensland. North Stradbroke Island is formed mainly of massive vegetated Cainozoic aged dune sands. Since the 1950s, a number of operations have mined rutile, zircon and ilmenite on North Stradbroke Island. In such mining operations, a dredge and an associated processing plant are floated in a pond either above or below the prime groundwater table The numerical model was based on the North Stradbroke Island Groundwater Management Model, developed in 2001 by the Department of Natural Resources and Mines (NR&M). This model was constructed using the modular, cell-centred, finite-difference groundwater flow model, MODFLOW, developed by the United States Geological Survey (USGS). The NR&M model was refined to improve model resolution and detail for simulating dredge mine paths. Of particular interest were: water table fluctuations induced by mining for the identification of slope stability risk; the optimisation of sand spear arrays supplying mine make-up water requirements; inflow and outflow rates to the dredge pond for overall mine water balance; and interactions with Eighteen Mile Swamp and water supply bores controlled by the Redland Shire Council (RSC). Depending on the water level in the dredge pond compared with the surrounding groundwater table, water either flows out of the dredge pond into the groundwater regime or from the groundwater system into the dredge pond. The MODFLOW river package (RIV) was utilised for the modelling study. Dredge pond movement was simulated using specialised software developed by Watermark Numerical Computing (WNC) to interpolate pond positions and map the dredge path to the model grid both spatially and temporally. As tailings placement affects the groundwater system through increased recharge, the MODFLOW recharge package (RCH) was utilised to simulate different recharge efficiencies. Long-term model predictions were made for the period from July 2002 to May 2021. Results of the modelling showed that exchanges of flow between mining operations and the groundwater regime could be effectively managed. The study provided valuable information which was used to develop an appropriate mine water management plan.

Jan 1, 2003

By Moort van J C

A new low-intensity magnetic separator which operates by spinning particles in a continuously rotating magnetic field is able to reduce particle entrapment of non-magnetics to an almost insignificant level. In such separators the removal of ma

Jan 1, 1997

A major problem in the continuous casting of aluminium killed strip steel is the incidence of black and grey lines in the strip surface caused by the alumina inclusions. One place for limiting the number of alumina inclusions is by providing favourable fluid flow conditions in the ladle so that the inclusions float out to the surface or adhere to the ladle wall. In laboratory equipment 20 kg of steel was melted in an alumina crucible of 14 cm diameter in an induction furnace. Deoxidation was carried out while the melt was constantly stirred by argon bubbling. Bubble frequencies were measured at the lance tip using a microphone technique. High speed cine photo- graphy was incorporated to measure melt top surface velocities. Experimental results indicate that the rate of removal of inclusions is a function of both the gas input and the power input. However due to unfavourable surface area to volume ratio, reoxidation of the melt took place. Some other experimental difficulties in working at high temperatures are also discussed such as lance design, melting arrangement and sampling techniques.

Jan 1, 1984

The procedure used for Truck Maintenance is described systematically in this paper. Emphasis is given to manpower required, work facilities, daily maintenance and oil sampling procedure. Scheduled Preventative Maintenance Service, Electrical Service, Component Change, Truck Overhaul and Outside Contractors are also discussed. The system used, achieves the required results with an average haul truck availability in 1981 of 87.9 per cent. INTRODUCTION Situated on the Island of Bougainville, in Papua New Guinea, the Bougainville Copper mine nestles in a valley near the crest of the Crown Prince Range, between 600 m and 980 m above sea level. The mine is serviced by two towns, Arawa - an open town on the Coast and Panguna at the Mine Site. Currently Bougainville Copper operates an open pit mine removing an average of 198 000 dry metric tonnes of material per day (115 000 tonnes ore and 83 000 tonnes of waste) with a fleet of electric shovels and 154 tonne electric haul trucks.

Jan 1, 1982

By Sneddon A

Expansion of central production facilities at the Kutubu Petroleum Development Project in Papua New Guinea (PNG) required excavation of a steep hillside overlooking operating crude oil processing, storage and pumping facilities. Drilling and blasting were used to remove a large volume of rock which varied from hard limestone to soft sandstone, with zones of soft clay and many underground caverns. Similar ground conditions had made it very difficult to predict and control blast-ing results during previous excavation in this area.Special conditions of the project included restrictions on ground vibration levels at a high pressure oil pipeline and pump station within 100m of the blasting area, and a prohibition on any flyrock. As work progressed, some blasting was necessary with 20m of installations being constructed on the levelled project site. Thus blast design, drilling and charging were carefully controlled to avoid any incidents which could interfere with oil production or progress of the construction project.

Jan 1, 1994

The transportable moisture limit of a mineral concentrate (TML) is of great importance in the shipping of that material from Australian ports. Each year Australian mining companies incur substantial costs as a consequence of delaying shipments and/or multi-handling concentrates so as to comply with transportable moisture limits. Despite this there is a general lack of in-depth knowledge concerning factors that influence the parameter. Eight major Australian mining companies supplied sizing, specific gravity and TML data for their concentrates. Zinc, lead, copper and bulk concentrates were represented in their data. Estimated surface areas of the concentrates, as calculated from their normalised sizing data, correlated strongly with the reported transportable moisture limits. This high correlation prevailed in spite of the acknowledged limitations associated with the use of multi-sourced data and the adoption of simplistic approaches in the normalisation of sizing data and the estimation of surface area. Based on the broad range of concentrates studied, concentrate sizing data were concluded to offer potential as an alternative means of reliably estimating transportable moisture limits.

Jan 1, 1993