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By U Briem, R Verreet

The level of wire rope technology used in mine hoisting applications has a significant effect on the overall efficiency of the hoisting system. This paper discusses the effect that a reduction in rope mass per unit length and an increase in rope breaking strength can have on rock skip capacity and hence mine shaft output. A 20 per cent reduction in rope mass per metre for a typical 48 mm hoisting rope, while maintaining the breaking strength, increases the skipÆs capacity by circa 30 per cent at a suspended rope length of 3000 m. Such gains in shaft output, without any significant changes to the shaft or winder design, can have major implications for the feasibility of future deep mine projects. The technical challenge for rope manufacturers is how to get rid of 20 to 30 per cent of the rope mass while keeping the breaking strength and modulus of elasticity of the whole rope constant. CASAR are currently developing steel wire rope constructions where the steel IWRC has been replaced with high strength, high modulus fibres such as Kevlar«, Spectra« and Dyneema«. One of the key aspects of such composite rope designs is to ensure equal load sharing between the different rope components, ie in proportion to their area. If there is a significant difference in modulus between the fibre core and the steel outer strands, the core may not carry its proper proportion of the load and the outer strands would be overloaded. Some technical aspects of the design of composite steel wire ropes are discussed. A design and operational issue that needs careful consideration is the safe non destructive testing (NDT) of composite ropes. Traditional magnetic NDT would only be capable of inspecting the steel wires. Techniques therefore need to be developed that would give operators a reliable indication of the condition of the load bearing fibre core. This paper also discusses possible solutions to this very important NDT question.

Jan 1, 2005

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

By Motyka J, Adamczyk AF, Witczak S

A case study of migration of a paper factory fluid wastes, on the distance of 5 km from an underground disposal site to an ore mine is presented. The ore mine in question, situated in SW Poland is pumping 3.5 m3/s (ca 300 000 m3/day) of groundwater, producing a cone of depression about 150 m deep and several kilometers wide. The migration of wastes (pollutant) occurs within the carbonate karstic aquifer of Triassic age. The aquifer is about 100m thick and is characterized by the coefficient of hydraulic conductivity equal to 8 m/day on the average. The results of systematic measurements carried out for 13 years enabled to estimate the mean breakthrough curve of the pollutant. On this basis and taking into account the coefficient of hydraulic conductivity as well as the mean hydraulic gradient between the disposal site and the ore mine, the migration parameters of the polluting material, i.e. the real flow velocity, the effective porosity and the longitudinal disper- sivity have been calculated. As the measurements considered a long migration distance of the pollutant, the obtained hydrodynamic dispersion constant (dispersivity), in the authors opinion, is reliable enough to be applied for regional groundwater calculations, regardless of the "scale effect".

Jan 1, 1988

Most coal mines in Chongqing Area are highly gassy mines and liable to outburst of coal cnd methane. In order to harness mine environment and raise the Prodction capacity, methane predrainage is generally taken as a main preventive measure against outburst by all mines. In the recent ten years, the drainage volume per year has increased from 38.25 million m3 to mote than 100 million m3 with a volume over 12 m3 per tome of coal. In some mines, the draining rate is approaching to 50 percent, the rate in mining districts is up to 60 to 70 percent. The predrainage volume accounts for one fourth of total drainage volume. All these have effectively prevented the occurrence of coal and methane outbursts.This is the current situation of methane predrainage in coal mines in Chongqing area, the methods of predrainage to prevent outbursts and related parametres comprise:1. methods, technologies, supervision and effect of predrainage in different geological and mining conditions,2. the change of methane parametres pre-and post-drainage and the analysis of the effect of methane predrainage to prevent outbursts, and3. ways to improve the effect of methane predrainage.Thus the safety, reliability and production of Changqing Coal Mines will be enhanced.

Jan 1, 1991

At many locations in Australia the decommissioning of mining operations will require the disposal of excess water. If the water is contaminated its disposal may be restricted by government guidelines. The timing of water disposal may be critical to the schedule of close-out. The uncertainty of the annual rainfall input to the water storage and disposal system may determine the success or failure of close-out. The uncertainty associated with any outcome can be used to determine the reliability of the system, or inversely its risk. The technique of Monte Carlo simulation, using the uncertainty in annual rainfall, is applied to quantify the risks associated with water disposal as part of the requirements for close-out in two case studies. In both case studies it is assumed that water disposal is via evaporation only. The first case study is the Nabarlek operation, located about 270 km east of Darwin. This project is required to complete the engineering work associated with its close-out by December 1995. The second study investigates the situation of close-out for the Ranger Uranium Mine, about 250 km east of Darwin. It should be noted that the Ranger mine was examined as part of the annual update of its contingency rehabilitation plan and the probability of implementing the plan is extremely small. The probability of success for the Nabarlek case varied from less than ten per cent to greater than 95 per cent depending on the management strategy. Four possible strategies were investigated for the Ranger mine with the chance of success varying between 20 and 95 per cent. The estimation of the evaporation rate and the area allocated to evaporation was critical in both cases. By applying seasonally based evaporation pan coefficients determined on site, rather than an average monthly value of 0.75, the chance of success was improved by up to 35 per cent for Ranger. Simulation modelling is able to provide information on the likely response of mine water management systems and the level of risk. This information is required to efficiently plan and manage the disposal of water for close-out.

Jan 1, 1994

In the 1890s, The Goldfields Water Supply Department in Western Australia commissioned the diamond drilling of two deep artesian exploratory water bores near Coolgardie (Blatchford, 1899). At the time, in spite of strongly-worded advice to the contrary from the Government geologists, there was a wide popular belief that you could obtain artesian groundwater virtually anywhere providing you drilled deep enough. The first Coolgardie hole was drilled to over 900 m, despite the fact that the bore penetrated granite from a depth of 5 m below the surface. Drilling proceeded for more than 16 months, between July 1896 and November 1897. A small quantity of salt water was struck at a depth of 36 m. The second bore was mercifully terminated at a depth of 50 m, also in granite, with again only a small inflow of salt water. Such were the desperate lengths that were pursued to obtain a reliable water supply for the influx of people in the Eastern Goldfields gold rush. The WA Goldfields continued to rely on huge condensers for water supply until that great engineering feat, the construction of a water pipeline from Mundaring Weir to Coolgardie, was completed in 1903. An enormous network of rail tracks penetrated outwards from Kalgoorlie and Coolgardie for the collection of timber, principally to feed the condensers. Remnants of the rail network are still visible today. The acute shortage of fresh water led to great deprivation, disease and death among the early miners. Today, the water problems faced by the mining industry are thankfully not as severe, but they are nevertheless no less challenging. The southern part of the WA Goldfields is a notoriously difficult area for finding potable quality groundwater. Even as recently as the 1990s, there were occasional serious efforts to find potable groundwater in that area, some very imaginative and innovative. One mining company, working south of Southern Cross, spent many months experimenting with recovery of potable quality water from a shallow freshwater lens overlying hypersaline water in a low permeability weathered granite aquifer. They used very low capacity pumps manufactured from car windscreen washer pumps powered by solar panels.

Jan 1, 2000

By Pollmans GJ, Hoberg H, Schneider FU

The Institute of Mineral Processing at Aachen University of Technology has been engaged in fine and ultrafine comminution for several years. Former investigations had been dealing with the mechanical activation with the aim of increasing the solubility of highly resistant oxides such as tantalite and niobite while research on the product of ultrafine powders is of major importance at the moment. Materials of that kind are of increasing interest in the production of extremely resistant ceramics, in the development of new raw materials, in powder metallurgy and in the production of fillers (extender pigments) and pigments. The creation of ultrafine powders is difficult and very expensive. They can be produced by means of condensation or dispersion methods. One important method of dispersion is mechanical comminution. Due to long and intensive research and development all over the world important advances have been achieved but still a great number of questions and problems occur especially in producing materials of submicron and nanometer grain sizes which could be answered or solved only insufficiently up to now. These mentioned difficulties refer especially to: ò the required energy input into the feed material, ò the forming of strong agglomerates and wall stickings, ò the required product qualities, and ò the entire and reliable characterisation of the products. Basic investigation aim to clarify the micro and macro processes of ultrafine grinding and work towards solutions to the difficulties mentioned above. The aim of the Institute's research is the development of a new grinding device for producing ultrafine powders. First results of a laboratory scale mill of that type will be presented in this paper.

Jan 1, 1993

By T Davis

The 500 orebody in the upper levels of Mt Isa Mines in north-west Queensland was mined by sublevel caving and block caving from 1962 to 1969. The hot and reactive rock mass of this orebody provided significant mining challenges including ground temperatures above those resulting from the geothermal gradient. Recently Xstrata Copper has been studying the potential to mine this orebody by modern caving techniques. Part of the study process has included re-accessing the ore zones for diamond drilling and trial development. A cross-cut trial drive, the first primary development into the orebody in more than 30 years, encountered a temperature increase in development holes from low sixties to almost 80¦C in less than 10 m advance. The issues associated with managing this risk include sourcing suitable quantities of reactive ground explosives for a single small heading and the temperature limitations of the explosives and detonators. Risk management outcomes included controls to mitigate the safety and reliability risks relating to misfires. The control that dealt directly with the challenge of continuing development in elevated temperature ground was to cool the holes before and during charging. The most effective and practical cooling medium proved to be water. Rapid rock temperature recharge time meant cooling had to continue as close to firing as possible. Reticulation systems were constructed to allow cooling to take place up until withdrawal for firing. No misfires occurred with the cooling system and additional controls in place. This proved that developing safely and effectively in the elevated ground temperatures of the 500 orebody is practicable.

Jan 1, 2008

Wetherstones gold deposit is located just east of the township of Lawrence, in the Otago District of the South Island, New Zealand. The paper will describe aspects of the mining and exploration history of the Wetherstones gold field, current knowledge of the geology of the deposit, and speculate on possible outcomes of exploration in the modern era.   As at the famed Gabriels Gully situated nearby, most of the Wetherstones gold is/was contained in, or recycled into modern drainages from, the Blue Spur Conglomerate (æBSCÆ). The BSC is the basal member of a wedge of auriferous non-marine sediments of latest Cretaceous age which are tilted against the Tuapeka Fault Zone, a structure of regional dimensions. In particular mineralisation of elevated grade (which cannot yet be reliably estimated) appears to be concentrated in an elongate basement depression (ægutterÆ) of width around 100 m, variable thickness to a few metres, and axial length in excess of 500 m. The gutter plunges from the base of alluvial mining (where it has been partly exploited by underground methods) to depths of more than 100 m, beyond which it remains open and untested.   The prospects for a revival of mining at Wetherstones depend upon confirmation of what is here inferred to exist, and the discovery of additional gold. The economic prospects of the project however are enhanced by what is known or indicated of the geographic location, and anticipated geologic, mining and metallurgical characteristics of the mineralisation, and consequent anticipated environmental management issues.   The recognition of gold contained in pyrite in the BSC represents an upside to project economics which has never previously been evaluated. The Wetherstones Basin covers more than five square kilometres in areal extent. There is no modern exploration record of the majority of this area, leaving open the prospect of the discovery of additional gutters, and primary mineralisation in the underlying schist.   Australasia Gold Ltd has embarked on a program to reassess the potential resources of the Wetherstones gold mineralisation, and to evaluate the feasibility of mining.

Jan 1, 2004

Fire-clay blocks lining the combustion chambers of zinc concentrate flash-roasting, furnaces operating at 1,000-1,200° C. have suffered moderately rapid deterioration due to slagging. The attack is accentuated by high temperatures, and is probably caused by lead oxide volatilized from the roasted concentrate.Resistance of refractories to attack increased with increasing alumina content from 30 to 45 per. cent but at 90 per cent alumina spalling was troublesome. Magnesite bricks were'subject to some spalling, but some types may lie satisfactory. Chrome and chrome-magnesite bricks spalled seriously.Material thought to be suitable for use as a monolithic lining slagged badly and an alternative may be tested.INTRODUCTIONThe Electrolytic Zinc Company of Australasia Ltd. uses two multi-hearth furnaces and four flash or suspension roasting furnaces for the roasting .of zinc concentrates at its Risdon Works. The hearth roasting plant has been described previously by Forster (1949).A brief descriptioI1 of the first three flash roasters was given by Gordon and Forster (1955). A fourth flash roasting furnace began operation early in 1957. This furnace is somewhat larger than the earlier furnaces, and the designed capacity is also higher, auxiliary equipment being altered to suit. An important structural difference between the older furnaces and the fourth flash roaster is that the walls of the combustion chamber of the new furnace are lined with high alumina fire-bricks instead of fire-clay blocks. Thischange was made because the fire-clay blocks in the older flash roasters had shown s-evere wastage due to slagging by lead derived from the concentrate.

Jan 1, 1959

By J Watson

Electronic detonator technology has been under development for the last two decades. Currently, there are a number of systems commercially available with several others still under development, each with its own unique features. This technology can offer a significant advantage to the drill and blast engineer through their ability to initiate an explosive charge at the æplannedÆ time. This new technology has created huge interest within the drill and blast community and also raised their expectations to produce better blasting outcomes. In many cases, specifications (or even expectations) of desired blast results are not properly defined. Interaction between the input variables (rock mass characteristics and blast design) and results (fragmentation, throw, damage, ground vibrations, etc) and their mechanisms, or relationship to one another, are not very well defined or understood. That is why rock blasting is still considered by many as an art rather than science. With one of the few remaining variables (cap scatter) now controllable, todayÆs blaster finally has the ability to apply science to his trade. Even though electronic detonators are available and becoming more commonly used, current field practices are not always conducive to extracting or deriving the maximum benefit from this new technology. In the authorÆs opinion, the following need to be understood to derive and sustain the maximum value: clear definition or specification(s) of desired outcomes from a given blast; impact of different features in an electronic detonator system (precision, accuracy, flexibility, reliability, etc) and their impact on the desired blasting outcomes; interaction of blast design variables (energy, energy distribution, timing, blast geometry) and their impact on desired outcomes; impact of rock mass variability and quality of blast implementation on the desired blasting outcomes; and critical need to utlilise appropriate tools and systems in order to measure and quantify benefits.In the authorÆs opinion a scientific implementation process is the key to derive the benefits. This paper analyses the industryÆs preparedness to derive the benefits from this technology and proposes a scientific methodology to understand, evaluate and sustain the value from this technology.

Jan 1, 2004

By D Thornton, B Smith, S Demey

Mine to Mill (MTM) optimisation, a total systems approach to the reduction of energy and cost in mining and mineral processing operations, is well-established technology. However, successful applications of MTM optimisation have been largely confined to gold, copper and lead/zinc semi autogenous grinding (SAG) operations, where the goals of tweaking the blast design to increase fines and hence throughput through the mill have been relatively easy to meet. The application of MTM optimisation in a more demanding environment, like that of a multi-stage crushing and screening aggregate operation, was conceived as part of a Department of Energy (DOE) initiative in 2004, aiming to reduce the energy consumption in the US aggregates industry. Two quarries operated by the Luck Stone Corporation of Richmond, Virginia, were selected for the demonstration sites. Dealing with ore variability and a requirement to maintain a fixed feed size distribution to the tertiary plant, whilst still aiming to increase yields of saleable products, presented some unique challenges. Despite these variables, the implementation of the MTM approach at Luck StoneÆs aggregate plant in Pittsboro, North Carolina, has led to a tangible improvement in productivity, particularly in the primary and secondary plants. The successful outcome was dependent upon several key factors, including reliable blasting and processing models, careful analysis of the rock conditions and plant configuration, understanding and buy-in from the Luck Stone operations staff, excellent collaboration with Virginia Tech staff and students, and long-term monitoring made possible through comprehensive PLC logging. This paper presents a review of the work conducted at the Pittsboro quarry and highlights the key reasons behind the successful implementation of the MTM approach in a complex plant environment.

Jan 1, 2007

The price of oil and other minerals may not make the costly business of offshore exploration seem -attractive at present. There is little doubt that the future search for the strategic resources will tend towards deeper waters particularly on the continental slope margins. In addition with the realisation that active tectonic environments (eg the Makassar Straits) cannot be excluded as potential hydrocarbon sources there is an increasing demand by the explorationists for deep water survey capability. Such deep water research has until recently been restricted to a few specialised academic institutions ;however with the anticipated extra, demand from other institutions, companies, and government agencies, Marconi Underwater Systems Limited (MUSL)and the Institute of Oceanographic Sciences in the UK have come together to allow MUSL to provide the deep water mapping system GLORIA on a commercial basis -for the first time. The GLORIA package comprises a deep water(more than 400m) side scan sonar system which, by operating at a frequency around 6.4 kHz can insonify swathes on the seafloor up to 60 km wide. In addition, single channel seismic, 3.5 kHz high resolution profiles, precision echo sounding, magnetic and gravimetric data all combine to provide as complete a regional interpretation as possible. The GLORIA system combines surveying at a reconnaissance level, covering as it does up to 20,000 sq.km per day, with a very high reliability, so that even in- economically unfavourable times, it can-still be considered as an invaluable and cost effective primary exploration tool. Analysis of the GLORIA data enables the identification of areas of particular interest requiring more detailed study by the more costly multi-channel seismics at a later date.

Jan 1, 1987

By McKenzie C. K, Stewart R. S, Simpson J

Blast control in small scale underground mining leads to improved fragmentation control, improved control over overbreak and dilution, and the optimisation of drilling and charging operations. Greatly improved control can be achieved through blast monitoring, to confirm proper implementation of blast designs and blasthole charging. Further improvements can be achieved through simple modelling, enabling blastholes to be placed in the correct locations and charged with the correct weight and strength of explosive. Improved design can be shown to significantly reduce overbreak and dilution, and even ground support costs. In one mine in Quebec, open stopes of widths varying from 2.5 metres to four metres and dipping at 36¦ to 38¦ were designed to achieve zero dilution using open sloping blasting practices. The first stope designed in this manner was monitored in detail and achieved its objective.A method for contouring damage around blastholes is presented as a basis for selection of drilling patterns, with particular application to the control of overbreak and dilution. Contouring can be used to provide reliable estimates of either overbreak or damage (where rock is broken het reynainc in nlarr)

Jan 1, 1993

By W Valery, A Jankovic

The ball mill in closed circuit with hydrocyclones is an industry standard, and well known methodologies exist for equipment sizing, selection and design. However, the potential to improve the capacity of ball mill circuits by replacing cyclones with screens has been recognised for many years and recently has been successfully realised, thanks to developments in fine screening technology. Proper methodology for equipment sizing and selection is required to capitalise on this opportunity, but there is currently insufficient information and few guidelines available on how to design such a circuit. This paper discusses the differences between ball mill circuits closed with cyclones and with screens. A methodology is described for equipment sizing and selection for a circuit closed with screens, and the laboratory testing requirements are described for low grade base metal ores and magnetite ores. An economic evaluation is also presented for a case study demonstrating the potential benefits of closing a ball mill circuit with screens.CITATION:Jankovic, A and Valery, W, 2013. Energy efficient ball mill circuit - Equipment sizing considerations, in Proceedings MetPlant 2013 , pp 285-295 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By Stokes WPC

The capital requirements to develop a new mining venture are becoming very large; amounts of the order of US$1,000 million are not now unusual among estimates to bring new mining complexes into production. At the same time prevailing political and economic conditions are making it increasingly difficult to determine whether or not a project is likely to be viable. These factors emphasise the need to carry out thorough evaluation studies of all mineral prospects before making major investment. Additionally with the rapidly changing economic climate existing at the present time, it is becoming more and more necessary to carry out reappraisals of existing mines. An important function of both initial evaluations and reappraisals is to provide the operators of the mine with effective mining plans to ensure that the operation will meet its required economic targets. P, p M. tl p b, c v, s c 1 n 1 f r d c e c e u w Modern computers are well equipped to store and manipulate large amounts of data with speed and reliability. Their use in the mining field r is increasing and this trend serves to free f technical staff from much of the time consuming m and error prone hand calculations which were o formerly required in determining reserves and w carrying out all forms of mine planning. r Nevertheless, computers are not a universal

Jan 1, 1980

The authors have succeeded in providing additional rigour and clarity to the formulation and execution of the dynamic programming algorithm for optimum open pit limit determination. The inclusion of the blocks on the J + 1 column in the search for Pmax, and constraining this search with blocks assigned a value of negative infinity, ensures an optimal solution within the defmed blocks. The effect of the negative infmity blocks is to preclude mining along the diagonal blocks from the first row that they occur in. Figure 1 graphically illustrates the effects of this on the calculation of P. A practical application for constraining mining with negative infmity blocks is the case where the pit outline is defined by lease boundaries and not by the value of blocks to be removed. Any legal, social or physical constraint could be accounted for in the same way.The danger in applying this technique is that the negative infinity blocks will override any other more profitable solutions that may exist. This is in fact what has happened in the example that the authors use. If a further column is added to the left hand side (column -1) and the calculation is carried out again, a more optimal x-section can be found. (If the negative infinity values are removed the same result is obtained.) This gives a pit value of 112 as against the 108 of the authors' optimal pit. This calculation is shown in Figure 2. Lerchs-Grossman optimization is reliable only if there are sufficient columns available to allow "mining" to optimum depth of the ore body and still allow the pit to break out at the surface within the confines of the columns.This author's approach is to create enough columns each side of the lateral limits of the ore to allow the pit to intersect the surface while still within the confines of the block model. Implementing the methods discussed by the authors helps to reduce the number of columns required to achieve this.

Jan 1, 1987

By Alwan M

At Binebase mineralisation is hosted within an andesitic Neogene volcaniclastic succession on Sangihe Island, Indonesia. Two major alteration types occur; an initial widespread phyllic assemblage of quartz -illite with chlorite, smectite, gypsum and pyrite, and a superimposed quartz - barite - sulphide assemblage. The phyllic alteration arose from a neutral to weakly acidic hydrothermal solution of greater than 200 degrees C, and the quartz - barite - sulphide assemblage arose from a cooler slightly more acidic fluid. This second alteration event is interpreted to have selectively replaced permeable volcaniclastic breccias and coarse lithic tuffs within the altered sequence. Gold and silver mineralisation is associated with the latter alteration, and is locally controlled by the degree of silicification and sulphide abundance. The sulphides present are pyrite, covellite and chalcopyrite. The sulphides are very fine grained with colloform and framboidal textures and were deposited contemporaneously with the bulk silicification of the coarse sediments. A large portion of the mineralised rock has been oxidised to a quartz - barite -limonite - goethite - jarosite assemblage.Coincident gold, silver and antimony geochemical soil anomalies gave the best correlation with anomalous gold and silver grades in bedrock as identified by drilling. Resistivity proved a reliable geophysical method for delineating zones of silicification.

Jan 1, 1990

By M Biesinger, R St C Smart

Diagnosis of the surface chemical factors playing a part in flotation separation of a value sulfide phase requires measurement of the hydrophobic and hydrophilic species that are statistically different between the concentrate and tail streams. Statistical methods, based on the monolayer-sensitive time of flight secondary ion mass spectrometry (ToF-SIMS) technique, have been developed towards this ultimate aim by measuring hydrophobic species (collector ions, dimers and metal complexes, polysulfides) as well as hydrophobic metal ions, precipitates and added depressant species. Reliable identification of specific mineral particles is central to this statistical analysis. A chalcopyrite/pyrite/ sphalerite mineral mixture conditioned at pH 9 for 20 minutes to study transfer of Cu from chalcopyrite via solution to the other two mineral surfaces, since this mechanism can be responsible for their inadvertent flotation in copper recovery, showed no statistical difference in the copper intensities on pyrite and sphalerite (selected from Fe and Zn images) after this conditioning. Principal component analysis (PCA) identifies combinations of factors strongly correlated (positively or negatively) in images or spectra from sets of data. In images, PCA selects these correlations from the mass spectra recorded at each of 256 ¦ 256 pixels in a selected area of particles. In the image mode, PCA has proved to be a much better method of selecting particles by mineral phase with clearer definition of particle boundaries due to multi-variable recognition. It has clearly separated a statistical difference in copper intensities between the sphalerite and pyrite phases. The PCA method has been applied to concentrate and tails samples collected from the Inco Matte Concentrator demonstrating extensive CuOH and NiOH transfer between the chalcocite (Cc) and heazlewoodite (Hz) minerals. Statistical differences illustrate the important discriminating depressant action of NiOH in flotation despite the activation of Hz by Cu transfer. The adsorption of the collector at specifically-identified Cu sites has been elucidated by the study. Importantly, the statistical analysis has been able to confirm some mechanisms and deny others proposed to control recovery and selectivity giving more focus on the control factors.

Jan 1, 2005

About 74% of global seismic energy release occurs in the Circum-Pacific zone. Worldwide, about 71% of seismic energy release is in the form of shallow earthquakes, 27% as intermediate, and 2% as deep earthquakes. Seismic energy release is variable in time and has been shown to correlate with the amplitude of the Chandler wobble. It was high during the period 1949 to 1967, and is now at a rather low level, with the latest earthquake over M = 8.0 having taken place in Indonesia in 1971. The average worldwide recurrence rate for the expected largest magnitude earthquake (M "9.5) has been estimated as several tens of years, in marked contrast to the several tens of thousands to hundreds of thousands of years separating the largest volcanic eruptions. Geological studies are needed to establish reliable mean intervals between large earthquakes, and to detect the e;:istence of long-term fluctuations in the ste of occurrence. Seismic gaps have proved seful in static forecasting of large earthquakes, by identifying places where closer study of the variation with time of seismicity, deformation, and other parameters, may lead to the dynamic p_ediction of time, place and magnitude of earthquakes. The model of stress concentration at asperities explains the main features of seismicity in the Circum-Pacific. Slow earthquakes have been detected instrumentally, notably an event immediately preceding the 22 May 1960 Chile earthquake, the largest this century. It seems likely that this type of deformation may explain both instrumentally detected and macroscopically observed pre-seismic deformation, as well as unusual animal behaviour reported before some earthquakes. Seismic and volcanic events are interdependent, with large earthquakes commonly triggering eruptions. Melting of rock and intrusion of magma is likely to accompany many earthquakes.

Jan 1, 1987