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By Juras ST, Krouse RH, Godwin CI

The Buttle Lake camp is in central Vancouver Island, southwestern British Columbia, Canada. The camp hosts world-class polymetallic volcanogenic deposits of Devonian, Frasnian age (370Ma). This paper describes an on-going sulphur and lead isotope study of the major orebodies.Sulphur isotopes were determined for sulphides (pyrite, chalcopyrite, bornite and galena) and sulphate (barite). Sulphide analyses are markedly different from sulfate. The differences are explained below in a unique model.Sulphide isotopic compositions cluster tightly (del34S -6.7 to 4.6), and demonstrate isotope reversals. Calculated temperatures of correctly ordered mineral pairs are unrealistically high. We conclude that the sulphides are in isotopic disequilibrium, presumably because of rapid precipitation from a quenched plume in an anoxic environment, and because of subsequent sulphide replacement.

Jan 1, 1990

By Finch W, Dunne R

Understanding how liberated and unliberated minerals behave in comminution and classification circuits is of vital importance to ensure that maximum liberation occurs without unnecessary and costly overgrinding. This paper presents the results of a study carried out by the Julius Kruttschnitt Mineral Research Centre and Newcrest Mining of the liberation performance of Newcrest Mining's New Celebration grinding circuit. Using data from surveys of the circuit, together with QEM*SEM analyses of individual streams, a detailed picture of the liberation and classification of gold-associated pyrite is presented. In addition the relationship between the QEM*SEM analyses and results from laboratory leach tests are also discussed. Using the survey and QEM*SEM data, mathematical models were constructed of the performance of the ball mill and cyclones, and simulations carried out to investigate ways of improving the performance of the circuit. The results from the more promising scenarios are Reviewed.

Jan 1, 1993

By T Connor

Alkali emissions are one of the environmental challenges facing alumina refineries. Queensland Alumina Limited (QAL) is undertaking a number of initiatives to continuously improve its environmental performance. One of these is a program aimed at the reduction of alkali emissions. Alkali emissions originate from a number of sources (eg elevated open tanks), and its level depends on a number of process parameters/ mechanisms (ie splash filling, thermal currents in tanks, streams discharged from a pipe, tank temperatures, atomisation) and climatic conditions (eg wind speed and direction, rain, etc). Under normal operating conditions, there is a continuous low level of alkali emissions from the plant. Certain vessels within the plant have been identified as major contributors to this level of emission, while certain activities within the plant contribute to a temporary elevation (æspikeÆ) of alkali emissions. QAL developed a method using phenolphthalein-treated pads to measure emissions within and outside QAL boundaries. These provide no information about mass emission rates but are important for detecting if alkali material is present. Since mass emission rates are important for determining if improvements in emissions are made, QAL identified the need to design an improved sampling method. Following the development and implementation of a sampling and analysis method to monitor alkali emission concentrations, QAL is conducting a number of feasibility studies evaluating a range of alkali emission reduction options. The alkali measurement method will be used to track and demonstrate progress in this environmental initiative. This paper will discuss the measurement method and emission reduction options being evaluated.

Jan 1, 2005

By S C. Dominy

The Bendigo Goldfield is located in the state of Victoria, Australia, and is one of a number of quartz-reef fields that make up the greater Central Victorian Goldfield. At Bendigo gold particles are characterised by their very coarse nature, ranging from below 100 to over 10 000 ¦m in size. Some 60 per cent of the gold occurs in particles greater than 1000 ¦m in size. This characteristic ensures that the mineralisation is very challenging to both sample and evaluate. Diamond drilling provides a measure of geological structure, but is a poor measure of in situ grade, understating it by up to 75 per cent. Drilling combined with on-reef development, bulk sampling and geological interpretation has been used to define Indicated Mineral Resources. For grade control, a balance had to be sought between sample representivity, cost, turn around time and practicality. Sampling of extreme nugget effect deposits generally requires the use of bulk sampling in order to be representative. However, the cost and turn around time is significant. As a result, a 50 kg micro-bulk sampling system has been introduced that attempts to overcome these problems by providing a fast, practical method that can discriminate between ore and waste. As the mine passes into production, grade control will increasingly become dependent upon geological data collection and interpretation.

Jan 1, 2005

By Carr SD

The Omineca Belt of the Canadian Cordillera straddles the western boundary of the North American paleocontinental margin and accreted oceanic and island arc terranes. Crustal thickening of the orogenic belt was initiated in the Jurassic and culminated in latest Cretaceous and Paleocene times.Thin-skinned shortening of the Rocky Mountain Foreland Thrust and Fold Belt was balanced by basement-involved crustal imbrication within the Omineca (hinterland) Belt. Middle and upper crustal rocks of the hinterland (Selkirk allochthon) were thrust eastward and ramped onto basement of the North American continental margin. By latest Paleocene the southern Omineca Belt formed an elevated crustal welt that was at least 60 km thick.Within less than 3 Ma of the culmination of crustal thickening the belt was rapidly uplifted and tectonically denuded. The southern Omineca Belt was extended by as much as 80% as upper crustal rocks were displaced on moderate to low angle normal sense shear zones and brittle normal faults. This oro-genic collapse is interpreted to be a gravitational response to crustal thickening and thermal soft-ening, facilitated by reduction in plate-boundary-induced far field stresses.

Jan 1, 1990

By Ramani R. V

In this paper, a comparative performance evaluation of geostatistical, spectral, and fractal methods is made for short-scale variability prediction. The algorithms compared are: sequential Gaussian simulation method; a random fractal algorithm based on the generalised stochastic subdivision method; and a spectral simulation approach adopted for direct multi-dimensional simulation. The data for this study have been obtained from a mined out coal property. As this property was being mined, a 7315 m by 7315 m (24000 ft by 24000 ft) coal block was extensively sampled at an approximate spacing of 107 m (350 ft) and the 60-ton samples were analysed for sulphur in the 1.50 float gravity fraction. This data set is used here with the three methods to generate the simulated realisations, which are analysed for semivariogram reproduction and for simulation errors. Although all three methods converge to the true semivariogram in an average sense, the coefficient of variation of the average semivariogram for the Fourier integral method is minimum. The realisations generated by the sequential Gaussian method have minimum mean simulation error. The choice of a simulation method based on variability reproduction and simulation errors remains difficult.

Jan 1, 1995

By Xueqiu H

Since the hypothesis of coal and methane outburst mechanisms based on elastic mechanics gives no consideration to time, it cannot give satisfactory explanation of the outburst occurrence and its development. A creep mathematical model of coal containing gas has been set up through creep tests and analysis under a condition of triaxial compression. Such a model can explain the phenomenon of coal and methane outbursts successfully. The tests proved that there is no essential difference between the rheological properties of prone outburst coal and non-prone outburst coal. Outburst can take place in any kind of coal if the rheological conditions of coal containing gas are met. The creep mathematical model provides a basis for establishing a comprehensive index of coal and methane outburst potential.

Jan 1, 1992

By Lukaszewski GM

The indiscriminate surface disposal of coal waste in the past has created a serious fire hazard in the bush of the northern New South Wales coalfields. Spontaneous or bushfire-induced combustion in large neglected dumps of this material has increased in recent years causing a rise in air pollution. Surface methods of coal waste disposal are still being practised, and in many cases new material is being added to old dumps, many of which are burning. CSI RO has conducted research on methods of preventing and controlling fires in coal waste and recommends practical methods of overcoming these problems. Some laboratory and on-site investigations are described and the hazards of improperly constructed dumps are considered. The available techniques of fire prevention and control are discussed in relation to Australian conditions. Proposals for the safe and economical disposal of coal waste are outlined.

Jan 1, 1970

MANPOWER RESOURCES The optimisation of human effort has been an ongoing and significant process in the coal industry since industrialisation as we know it began. The extent to which the changes sought have been achieved has, over the years, been in the main determined by the economic and political forces existing at that time and the determination and character of the individuals involved. The question of optimisation is therefore not new in our industry. Hopefully this presentation will demonstrate to the reader the effect of previous measures adopted by industry to optimise all facets of its operation and in particular that of the human Resource.

Jan 1, 1991

By Szwedzicki T, Jiang J

The acoustic emission (AE) technique has found wide application in rock engineering. Generally, acoustic emission, which is produced by a rapid microcrack growth, is an ubiquitous phenomenon associated with brittle fractures and can provide information on the failure process in rocks. The sudden release of stored energy in the form of an elastic stress wave that travels from the point of origin within the material to a boundary is called an AE signal or a discrete AE event. Based on a number of experiments and analysis, the correlations among the rock type, the complete stress-strain behaviour, mode of failure and AE properties are investigated and the AE pattern has been classified as four types: single-peak AE, double-peak AE, continuous AE and absent AE. Each type of AE pattern corresponds to a certain type of rock and is largely related to the internal structure and imperfection of a rock. Applications of the AE technique in stability monitoring, in situ stress assessment and seismic source location are also discussed.

Jan 1, 1995

In May 1977 a new dam was commissioned for disposal of 600,000 metric tonnes/year of tailings. Design basis, costs and construction problems are described. Problems arose, assoc- iated with lack of experience in building such a dam "from scratch". Solutions are described land costs given.

Jan 1, 1978

The design and operating characteristics of the hydraulic cyclone elutriator were described in detail by Kelsall and McAdam (1963), and the method of operation of the commercially available version, the Cyclosizer, is described in the manufacturer's pamphlet (Anon). Complete details of the operating procedure are given in the relevant operating manual (Anon, 1964).The cyclones which form the basis of the Cyclosizer (Fig. 1) under normal operating conditions produce typical cut sizes of 44, 33, 23, 15, and 10 µm for cyclones one to five respectively for material with a specific gravity of 2·7. At the end of the selected elutriation period each sized fraction is discharged and collected for subsequent assay or analysis but all material rejected by the fifth cyclone (e.g. minus 10 \lm quartz) normally passes to waste. When this material is needed for separate study, although its amount and average analyses can be calculated by difference, it may be necessary to collect more than 250 I. of very dilute suspension, flocculate the solids, allow to settle, and decant off the supernatant liquid.This procedure is cumbersome and inconvenient and the simple technique to be described may offer some advantages. The temperature of the water fed to the Cyclosizer is maintained at a constant value for added reproducibility.PROCEDUREThe present overall treatment of the subsieve material (minus 37 \lm) fed to the Cyclosizer incorporated several refinements compared with normal operation and these may be best illustrated by anactual example. Material to be cyclosized (25 to 100 g depending on size distributIOn and specific gravity) is completely dispersed in water at 23 QC by vigorous stirrmg, using suitable dispersants if necessary, in a...

Jan 1, 1974

By Chen Z, Dong H

This paper describes the autogenous carrier flotation of 0 - 20 ¦m ilmenite using 40 -- 80 }tm ilmenite as carrier. Investigation is made of the influence of main technological parameters on autogenous carrier flotation. The mechanism of autogenous carrier flotation is discussed using extended DLVO theory. The main conclusions are as follows: 1. the smaller the fine particles the more easily they adhere.to carriers; 2. the selectivity of autogenous carrier flotation depends on the selectivity of adsorption of collector. In the autogenous carrier flotation of ilmenite/plagioclase mixture assaying 15.35 per cent TiO2, a concentrate containing 47.17 per cent Ti02 can be obtained by primary separation with a recovery of 93.05 per cent. KEYWORDS: Autogenous carrier flotation, extended DLVO theory, ilmenite, styrylphosphonic acid.

Jan 1, 1993

An improved technique for the quick and accurate measurement of the weight and centre of mass in the horizontal plane of large machines has been developed. On-site weighing of large plant such as bucket wheel dredgers is an important part of the commissioning procedure. The results from the weighing assist in determining the stability of the machine and also enable confirmation of the structural weight distribution used for stress analysis at the design stage. In this paper the techniques previously used for weighing are reviewed and the sources of error using these methods examined. A full descrip- tion of the current technique and procedure is given explaining how the measurement system comprising strain gauge load cells, displacement transducers, wind speed and direction sensors, data logger, computer and software was developed to enable quick and accurate measurements to be made. Proposed modifications to software necessitated by the replace- ment of current measuring instrumentation and computer are discussed. A typical example of measurements from the weighing of a large dredger, illustrating the accuracy of the new technique is given and the calibration technique used to check the accuracy of the force and moment measurements is explained. An outline of how the results are used to certify the machine for operation is given.

Jan 1, 1989

The invitation to speak today was in the form of a single sentence instruction: How does your company run and how do you communicate from top to bottom? It looks like I'll have to let you into our little secret. The team at Croesus know what works for us but we've never talked about it with others - least of all presented it at a conference such as this. In fact we tend to avoid the jargon normally associated with Best Practice or TQM, however in our own way, each of our staff are 100 per cent loyal to our company's aim to maintain and strengthen our commercial success. Just how we achieve this at Croesus is the subject of this presentation today, but first a little history. My dear old grandfather arrived in Kalgoorlie, as a mining engineer 100 years ago. Do you think he would have chuckled if someone suggested to him that a hundred years later we would just be starting to understand Kalgoorlie's geological mysteries? Well, here we are 100 years later and Croesus Mining is fortunate to be part of a generation now realising the true potential of Kalgoorlie's Goldfields. This provides us with a very fertile field in which to sow the seeds we can obtain from the World's Best Practice in Mining and Processing. With each new mineral deposit being discovered, old theories are being exploded. Each new deposit has a personality of its own, leading to some belated pioneering theories of where to drill next, and how to reduce internal costs so that we can win the war against constantly increasing external costs. What we have now and what the old timers didn't have is a huge database of geological input spanning several gold booms and a couple of nickel booms. My only interest in history is to pick up the points that may help us for our future. This is what we are doing in our company which is something of a David, in the David to Goliath range of mining companies in Australia. As a humbling thought; of the 115 164 tonnes of gold that the world's mines have produced throughout history, four tonnes have been produced by Croesus Mining. That's equivalent to 0.003 per cent of the total world's gold production. In the past financial year we achieved a dividend yield of five per cent. To put this into perspective, that's over twice the dividend yield of BHP, Australia's largest company. As we are somewhat less known than BHP, let me spend a few moments giving some particulars of our company's background.

Jan 1, 1995

Tertiary laterite is extensively developed in the Darling Range area, but there is doubt that. the high relief areas along the Darling Scarp have been peneplaned. Three distinct laterite types are distinguished which are termed transported, introduced and residual laterites to avoid ambiguity. Transported laterites are recemented (primarily) lateritic materials and introduced laterites are chemical deposits of bog iron type. Residual laterites are formed in situ from the host material which can be either decomposed bedrock or detrital' clay, and the two varieties formed from these sources are termed residual A and residual B laterites. The genetic requirements for residual laterite formation are (1) host material, (2) porosity and permeability, (3) rainfall, (4) temperature, (5) relief and drainage, (6) vege- tation and (7) time. Previous theories on the origin of laterite appear to be inadequate and incompatible with field observations. Field investigations and drilling in the Darling Range area disclosed lenticular section and thickest laterite development on slopes and thin or oc- casionally no laterite development on crests. Lateritisation is considered a surface feature and the end product of the chemical weathering cycle. The relief and rain-water acting on a kaolinitic host material are con- sidered the major contributing factors in the

Jan 1, 1973

By Reed M. E, Cloutt B

Particulate samples were taken from the gas space in the settler of the Kalgoorlie nickel smelter using a vertical sampling probe and a specially designed isokinetic sampling probe which also quenched the samples. The vertical sampler was found to give unrepresentative samples. Suction thermocouple measurements of the gas temperature were also made. Using the isokinetic probe samples were taken at four points ranging from near the base of the reaction shaft to the base of the uptake at depths up to 1.5 m into the settler. Dust loadings and the sizing of the samples were determined. These parameters were found to be most affected by sample position and depth. The dust loading decreased along the settler but increased with depth. The loadings varied from zero near the roof to several hundred g Nm 3 near the slag. The dust also became coarser with increasing depth into the settler. Examination of the samples showed them to consist of spherical particles the largest of which were about 500 microns in diameter. The dust was mainly composed of mixed iron/nickel oxides with a little sulphide.

Jan 1, 1991

By He BQ

Static attachment of bubbles to solids is contrasted with dynamic attachment in flotation cells. The times of contact during particle-bubble collisions in dynamic attachment are compared with the induction time determinations and the kinetics of thinning of the liquid films separating solids and bubbles. The thinning is examined mainly in terms of electrostatic and dispersion (van der Waals) contributions to the disjoining pressure existing in the films. The local heterogeneity (on a molecular scale) of charge distribution invariably present at all interfaces (even at conditions of zero zeta potential) calls for some means to minimize possible electrostatic repulsions which arise when the electrical double layer at the air-bubble interface begins to overlap that present at the solid surface, on encounter between particles and bubbles. It is postulated that dipoles of frother molecules, owing to their ability to "flip over" (polarise), replace localized electrostatic repulsion by attraction within fractions of a milli- second, as long as the structure of the frother molecules is sufficiently "bulky" to maintain diffuse films (of mixed collector-frother) at the air/liquid interface of bubbles. The relaxation times of dipoles (signifying their "flipping over" ability) have to be shorter than the collision times between particles and bubbles for particle-bubble attachment to be facilitated under dynamic Conditions.

Jan 1, 1984

HoistEM is a helicopter-towed time domain electromagnetic system. This paper presents details of the towed array structure (the Hoist) as well as a description of the instrumentation. A comparison between HoistEM and ground TDEM (from which HoistEM was derived) is given. Over 50 000 line kilometres of HoistEM have been completed to date and datasets for structural mapping, nickel, base metals, manganese, ground water and bathymetry are presented and discussed.

Jan 1, 2004

Developed and built in 1982 for simultaneous bathy-metric and reflectivity mapping of the deep ocean by the Hawaii Institute of Geophysics, SeaMARC II was a breakthrough in sea-floor mapping technology. The design was developed cooperatively by industry and academia, and the system has served as a prototype for a new generation of mapping tools for operation in both shallow and deep water.Research programs using the SeaMARC II system have focussed on basic research into the geophysical evo-lution of the Pacific, ranging from intra-atoll mapping to surveys of the deep-sea trenches. During the past few years most work has been concentrated on detailed investigations of the morphology of mid-ocean spread-ing centers, seamounts, and the subduction zones which surround the Pacific. The detail provided by the high resolution, 10-km wide side-scan sonar images of fault and fold structures, combined with the swath of bathy-metric information obtained simultaneously, allow previ-ously unattainable analysis of seafloor morphology and are leading to development of detailed models for ocean crust genesis and deformation.

Jan 1, 1990