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By Larry Schneider

Are you one of the thousands of hunters, fisherman, or hikers who purchased handheld GPS systems over the past several years and then been disappointed in their accuracy and performance. Or maybe you are one of the hundreds of blasters who have attempted to use GPS as a method for locating the exact position of their blast and measure distances from the blast to nearby structures. If so, you may have found that the accuracy of the handheld GPS systems left much to be desired. It may be time to get the units back out of storage and give them another try. As of midnight, May 1, 2000, the federal government has turned off the “error” built into the system known as “selective availability.” Here is a brief explanation of what that means in a question and answer format.

Jan 1, 2001

Study on Basic Theory of the Grain Settlement in Fluidised Bed This paper takes thick goal grains (less than 1.5 cm) as research object. According to different densities and particle sizes, thick goal grains are divided into 20 kinds of narrow density and narrow size level average grains. Free settling and hindered settling tests are respectively carried out in ?100 fluidised bed thick goal separators. Hindered settlement includes hindered settling velocity test and measurements of suspension density. Results show follows. (1) Fluid state in separator belongs to transition region. Alien's law is the appropriate formula of thick coal particles free settlement terminal velocity. (2) The main factors affecting hindered settling velocity are the number of solid particles in medium and the structure feature of the particle group. The bigger volume fractions of solids ? is, the smaller decreasing velocity coefficient of particle hindered settlement ¯ becomes. In the organism from bottom to top, density of suspended particles in fluidised bed gradually decreases, but near the top of the suspended particles, the density increased slightly. With increase of density and size, suspension density reducing extent increases from bottom to top of separators.

Sep 13, 2010

The ore milled from the Lead Lode of The Zinc Corporation leases consists of a fairly granular mixture of galena, marmatite, chalcopyrite, tetrahedrite, pyrrhotite, pyrite, and lollingite with a gangue association of calcite, quartz, bustamite, rhodonite, mangan-hedenbergite, garnet, fluorite, mangal1o-calcite and apatite. The silver content of the ore occurs in three minerals-tetrahedrite, dyscrasite, and pyrargyrite, the last two mentioned occurring in microscopic association only. Other metallic and gangue minerals are also present in this complex mineralogical association, but do not influence the milling operations. Fortunately, the silver minerals favour the galena and chalcopyrite as their host minerals, thus facilitating the recovery of both copper and silver in the lead concentrate. The ore from the Lead Lode assays from 14-18% lead; 3·0-4·5 oz. silver per ton, and 9·5-12·0% zinc.A parallel lode, known as the Zinc Lode, is well developed in The Zinc Corporation leases. This lode assays from 6-8% lead, 1·5 oz. silver per ton, 18-25% zinc with a siliceous gangue. The common Lead Lode gangue minerals-ealcite, rhodonite, bustamite-are very rare in present underground exposures. No metallurgical work was done on this ore during the pilot plant operations.The aim in the milling process is to produce: 1. A lead concentrate with the maximum economic recovery of lead, silver, gold, copper and antimony, and minimum zinc content.2. A zinc conc,entrate with the maximum economic recovery of zinc, cadmium, and cobalt, and minimum iron, arsenic and fluorine content.3. A waste residue containing sufficient granular material to be utilized as underground fill.In considering the economics of the milling practice the above three requirements plus consideration of the tariffs submitted by the purchasers of concentrates were the deciding factors in the evolution of the present milling practice.Towards the end of 1924 The Zinc Corporation Limited added to and adapted the old zinc tailings plant for the treatment of 5,000 tons of crude ore per week. This plant, which operated until January, 1936, was in general principles similar to the standard Broken Hill methods of ore concentration, whereby the galena was recovered by the gravity concentration methods of Hgging and tabling with selective flotation concentration of the residual galena and marmatite. One important difference from other Broken Hill plants was that the primary grinding of the jig tailing was performed with flint-loaded mills operating in closed circuit with revolving screens. Two primary grinding sections were installed, each...

Jan 1, 1941

By Ronald Molnar

"High demand for metals is driving the exploitation of lower grade and more complex orebodies. These projects are often the initiatives of junior mining companies with limited financial resources. In addition, existing operations seek to enhance revenue from their existing metal recovery operations, through the production of value-added by-product metals and chemicals. Typically, hydrometallurgical circuits, often with novel chemistry, are required to exploit these new ores, to produce the multiplicity of products that will make a marginal project economical, or to increase the product range of an existing operation. Often, the mineral processing engineer is given the task of coordinating the development of a back-end hydrometallurgical flowsheet for their mineral processing project. This paper discusses the objectives that companies have when they commission the operation of a hydrometallurgical pilot plant. The paper goes on to enumerate some of the principal differences between mineral processing and hydrometallurgical pilot plants and the effect these have on the design, operability and potential pilot plant outcomes. Important factors include working with chemically reactive solutions and pulps, elevated temperatures operation, changing rheological properties of slurries, the complexity of integrated circuit flowsheets with long hold-up times and multiple recycle streams, and the need in some cases for extreme attention to purity and cleanliness. Examples will be drawn from the extensive experience base of SGS Minerals Services at the Lakefield site, in piloting both mineral processing and hydrometallurgical process flowsheets.INTRODUCTIONWe are currently experiencing a period of strong growth in the demand for metals. This in turn is turning the spotlight on a great many smaller mining companies and mining promotion ventures trying to tap into the rising metal demand. Some of these companies want to develop their properties and recover metals while others want to develop to the point that a major company will take an interest, or in some cases buy them out completely.With the heightened interest in metals, many orebodies that have been known about for years are being reconsidered for exploitation. Often, the reason they have not been developed to date is because of difficult metallurgy and marginal grades leading to marginal economic viability. In both cases the key that unlocks the resources is often the application of a novel metallurgical flowsheet, often a hydrometallurgical flowsheet."

Jan 1, 2006

By Thomas O. Glover

Cameroon continued to enjoy sustained economic growth that began with its independence in 1960. Growth in the gross domestic product (GDP) averaged 2.8% per year during the 1960's and the first half of the 1970's. Starting in 1976 and for the succeeding 10 years, the GDP accelerated rapidly owing to the coming on-stream of Cameroon's small but domestically significant offshore oil industry. In 1985, the GDP grew by 7.8%, but in 1986, it was only up 5.5%. The country's sustained economic growth in dollar terms of gross national product (GNP) per capita reached $1,075 in 1986. The ranking in GNP per capita by the International Monetary Fund put Cameroon in the middle-income category for developing countries. The sustained economic growth rate up to 1986 was due to the injection of income from oil into the economy, but crude oil price reductions in 1986 brought a slowdown. In 1986, crude oil production grew to 200,000 barrels per day, an increase of 8.2% from that of 1985. Most of the oil came from the Société Nationale Elf Aquitaine (SNEA) wells in the multifield Rio del Rey complex. Additional output came from the Moudi Field operated by Compagnie Française des Pétroles S.A. Proven oil reserves in Cameroon were 540 million barrels. At 1986 production rates, and in the absence of further discoveries, Cameroon will have exhausted its recoverable oil reserves by the year 1995. Owing to worldwide crude price reductions, the country's oil income fell 60% between 1985 and 1986, from $1.82 billion2 to $0.72 billion. Cameroon's refinery operator commenced operating the Sonara refinery in 1981 at Point Limboh. Sonara's capacity of 43,000 barrels per day was small by most standards. In 1986, natural gas reserves, estimated at 100 billion cubic meters, were not produced commercially because there were no domestic users. Proposals for a multibillion-dollar liquefied natural gas plant at Kribi had been submitted; however, work on the plant had not commenced.

Jan 1, 1988

By Neil F. Archer

Due to the increased chance of violations and shutdowns by the U.S Occupational Safety and Health Administration(OSHA) and the U.S. Environmental Protection Agency (EPA), a company can save itself problems by taking control of the dust caused by conveying material. A complete dust-control policy can keep these emissions confined, sealed and suppressed, protecting the environment from fugitive, airborne dust. Material handling and processing, storage and traffic are the major dust producing sources. All industries that convey dry, light material need a dust control system.

Jan 1, 2003

By Jerry T. Shelby

Surface and underground mining operations require equipment with high power output ratings. Haul trucks, loaders, dozers, and other equipment need increasing horse-power to meet production demands. To get more horsepower out of the engines driving the equipment, most manufacturers use turbocharging. Detroit Diesel puts the number at about 90% turbocharged, while Caterpillar estimates 75% to 80% of all its equipment is turbocharged. Turbocharging increases the power output and overall engine efficiency. But it presents some maintenance and operational problems that were not factors when only naturally aspirated engines (nonturbocharged) dominated the scene. A turbocharger is an exhaust-driven air compressor. Using the waste energy in the engine exhaust, a turbine wheel is driven. This wheel is connected by a common shaft to a compressor wheel. The shaft is supported by two plain bearings, or bushings. As the turbine wheel is rotated, the compressor wheel continually compresses the intake air to the cylinders. Compressing the intake air means that more air can be put into the cylinder to burn more fuel. The more fuel the engine can completely burn or combust, the more horsepower the engine can produce. Even though the turbocharger is a relatively simple device, it is a sensitive engine component. It requires special consideration at engine start-up and shutdown. Being freewheeling and exhaust driven, turbochargers can experience temperatures of 540°C 1000°F) and rotational speeds of more than 100,000 rpm. Due to those temperatures and speeds, lubrication is critical to the operation and life of a turbocharger. The turbo is located high on the engine, with the oil supply running through an external line from the sump. The recommended practice is to start the engine and allow it to idle for a few minutes before any revving or loading. This allows the oil to reach the turbo and properly lubricate the bearings before high rotational speeds are seen. Turbo oil supply lines can be as long as 1.5 m (5 ft). Depending on ambient temperatures and oil viscosity, it can take as long as 30 seconds for oil to reach the spinning turbo. However, as little as five seconds without oil can damage the turbo's bearings, reducing its life and overall efficiency. Lubrication problems seen at shut-down can also significantly affect turbo life and efficiency. Manufacturers recommend an idling period of five to seven minutes before engine shutdown. This allows the turbo to slow down and cool off somewhat to help prevent oil coking and bearing damage. When the engine stops, so does the oil supply. There is very little oil left on the bearing surfaces and in the turbo oil supply passages. The immediate heat transfer from the turbine wheel to shaft, bearings, and turbo body literally cooks what is left. This high heat without oil flow can cause bearing deformation by actually melting some of the bearing material. The rapid oil oxidation and coking will restrict oil passages, damage bearings and shaft. Besides heat soaking, there is another problem. If the turbo is spinning at high speeds when the engine is shutdown, the turbo must spin-down to a stop without oil flow. With the large size of turbos used on mining equipment, this spindown time without oil can be for as long as 10 to 20 seconds. Fortunately, lack of lubrication at start-up and shutdown and the subsequent bearing damage can be prevented by oil injection devices. These devices hold a reservoir of engine oil. The oil is injected to the turbocharger bearings immediately on start-up and for several minutes after shutdown. Oil injection devices are spring loaded, hydraulic accumulators. They are actuated at start-up by a solenoid wired to the starter motor. Engine oil pressure charges the accumulator during normal operation. Upon shut-down and loss of oil pressure, the device provides oil to the turbo for about two or three minutes. With an oil injection device, the engine can be started and immediately driven without fear of turbo damage. Also, an abrupt shutdown will not damage the turbocharger since the device will continue to lubricate for two or three minutes. A word of caution. Be sure the oil injection device provides positive oil displacement (pressurized oil flow). Do not use a gravity-flow device. Unless it is a true accumulator, the device could starve the turbo for oil on start-up, Ask for start-up and shut-down pressures and delivery times before considering installation. Keep the oil clean, and follow the manufacturer's recommended oil change intervals. These intervals are usually shorter than with naturally aspirated engines. Use oil with a CD rating designed for diesel applications. A multiviscosity oil is preferable. Use a synthetic engine oil, such as Mobil's Delvac 1, Gulf's Super Duty II, or Chevron's Sub-zero Fluid. Synthetics have much better flow properties at low temperatures. They also have greater oxidation stability (they can take the high heat of turbo-bearing lubrication. And they produce fewer deposits because they are more thermally stable. But synthetic oils do cost more - two or three times more. One additional point - maintain the air intake system. Since all mining is usually in a dusty environment, air filters should be changed regularly and intake systems should be checked for leaks. All intake air passes through the turbo. Any dirt or abrasives entering the turbo will damage the unit and shorten its life. While mining is a heavy duty business with severe operating conditions, you can get the life from your turbocharger that you expect by following a few simple steps: • equip the turbo with an oil-injection device to provide lubrication on start-up and shutdown; • change the oil and filters regularly; and • use the proper oil-synthetic, if possible.

Jan 3, 1987

By F P. Hao

Organo-sulphur-based collectors (eg xanthates, dithiocarbamates and dithiophosphates) are widely used in the flotation of sulphide minerals. Xanthates (ROC(=S)Sû), for example, adsorb strongly at sulphide mineral surfaces, in a reaction that is electrochemically coupled with the reduction of dissolved oxygen. One of the oxygen reduction products, hydrogen peroxide, reacts directly with dissolved xanthate, leading to its oxidative decomposition. Experimental work has been conducted, using ethyl xanthate, to understand the molecular mechanism by which hydrogen peroxide reacts with xanthates. A number of degradation products have been identified, some of which have not been reported previously. This oxidative decomposition reaction pathway is discussed in the broader context of xanthate decomposition in flotation systems. One of the identified ethyl xanthate decomposition products, ethyl perxanthate (ROC(=S)SOû), has been observed in the process water of a number of mineral processing operations. The interaction of this molecule with goethite (α-FeOOH) particles, typical of that found in tailings dams, has been studied in more detail using attenuated total reflectance (ATR)-FTIR. The ethyl perxanthate molecule has been found to coordinate to iron (FeIII) at the goethite surface, and undergo a surface-catalysed decomposition process. In the presence of both PbII and goethite, a ternary surface complex is formed, where ethyl perxanthate is coordinated directly to surface adsorbed PbII atoms. The results obtained give some insight into the environmental fate of ethyl xanthate in tailings streams, and a basis on which to consider the environmental importance of such species in tailings dams. Strategies for the destruction of residual xanthate levels in waste water streams are discussed in terms of the likely reaction products.

Jan 1, 2002

By G. Gomez Ciments-Calcia

The sources of complaints by neighbours of the operating quarry are due to the 3 following causes : - Impulsional noises or air hoch wawes – Vibrations - D u s t How a blasting in a quarry operation is felt by neighbours cannot be measured solely by the various limits set by national and European regulations regarding vibrations and air shock waves (sound pressure).

Jan 1, 2002

By James A. Mason

The State of California has instrumented numerous buildings, bridges, and dams throughout the state with earthquake recording devices. These accelerometers are strategically placed to measure the response of the structure to a specific seismic event. This comprehensive program enlightens the field of seismic engineering after each earthquake. The Office of Strong Motion Studies, California Strong Motion Instrumentation Program, a sub-branch of the Division of Mines and Geology, provides a professional service unequalled in the world. Within hours of a local earthquake, a preliminary report with the epicenter / hypocenter, structural damage, and time history records are available to all interested parties. The included partial report in the appendix, see section 5.1, is one of the reports that C.S.M.I.P. produced after the Loma Prieta Earthquake of October 17,1989. The diagram on the cover is even of interest. This is a small portion of San Francisco. The values on the diagram are the recorded maximum horizontal ground accelerations at that location in the city. For example, the acceleration at Yerba Buena Island was 0.06g. (The "g" refers to the acceleration of gravity. Thus, a 0.06g acceleration refers to the force, F=m*a, that the structure would experience. For this case, the force would be six percent, 6 % , of the mass of the structure.) Yet, directly on the other side of the Bay Bridge, at Treasure Island, the acceleration was 0.16g. Yerba Buena Island is a natural island composed of hard granular material. Whereas, Treasure Island is a man-made island of imported filled. Here one can see the absorption / transmission difference between hard material, which interact with short seismic wavelengths, and soft cohesive material, which interact with long seismic wavelengths.

Jan 1, 1993

By H. Ikeda

INTRODUCTION [Slide 1] The Role of the MMAJ Ladies & Gentlemen, it is a pleasure for me to be able to make a speech at this SME annual meeting, representing the Metal Mining Agency of Japan. [Slide 2] Today’s Topics In my presentation today, I would like to divide my topics into four parts. First of all, I would like to describe the current situation of Japanese non-ferrous metal mining and mineral processing industries in Japan. Secondly, the supply and demand of non-ferrous metals in Japan. Thirdly, I would like to spare some minutes on the overview of overseas development by Japanese mining companies. Finally, since some people may not be sure what the Metal Mining Agency is or what this Agency, I would like to briefly introduce the Metal Mining Agency of Japan.

Jan 1, 2001

This backgrounds the methods, and technical terminology, of digital image processing techniques used to write out remote sensing imagery.

Jan 1, 1983

By W. Pawlos, A. Bakalarz, M. Duchnowska

This paper presents the results of an investigation into the influence of hydrodynamics on a preflotation process for the copper sulfide ore from the Fore-Sudetic Monocline deposits in Poland in a flotation machine. The main aim of the preflotation stage for Polish copper ore is to remove the easy-to-float organic matter — organic carbon — that causes serious problems in metallurgical processes. The organic matter is connected with the presence of shale ore. This paper describes the preflotation experiments conducted to investigate the effect of various stirrer speeds. The upgrading selectivity of copper and organic carbon were analyzed and compared. The results show that the effectiveness of separation between organic carbon and copper decreases with increased stirrer speed in the laboratory flotation machine. The more intensive the mixing of the flotation suspension, the lower the selectivity of the preflotation experiment. Lower stirrer speed probably provides lower mechanical entrainment and flotation of copper minerals.

By J. D. Bosman

The problems associated with squeezing rock conditions in tunnels are well known and have been extensively investigated in the past. Although squeezing conditions are predominantly found in tunnels developed in weak rock types it has been noted at the No. 6 Shaft of Hartebeestfontein Mine where the host rock consists of hard, brittle quartzites. This paper investigates typical time-dependent deformation mechanisms in the rock at Hartebeestfontein Mine. The paper will focus on observations made in a strike-orientated tunnel that intersected weak quartzite layers, that were sandwiched between two competent quartzite beds. The observed squeezing mechanism is dominated by creep along bedding planes with a soft talcaceous infilling that behaves in a clay-like fashion when saturated in water. Stress-induced deformation processes, some distance into the sidewall of the excavation, force the already fractured periphery of the excavation into the void. A laboratory study of the creep of intact rock and discontinuities collected at this site was conducted to characterize the time-dependent behaviour. The difference in creep rates between the two types of quartzite found at this site is described in the paper. Creep tests performed on the talcaceous infilling material found that its presence allows substantial shear creep along discontinuities. Attempts were also made to simulate the squeezing mechanism observed underground with numerical techniques. Due to the discontinuous nature of the mechanism described above, a viscoplastic displacement discontinuity technique was used as it allowed for the explicit simulation of discontinuity creep. The results of the modelling and how it compared with the observed behaviour are described in the paper. Environmental impact statement The work described in this paper will not cause any new, or contribute to any existing, hazards confronting the environment.

Jan 1, 2000

By T M. El Hajj, A C. Chieregati, M T. G C Marques, J M. Braga Jr, H Delboni Jr

"The estimate and control of sampling errors is essential for all mining operations, especially when dealing with strategic materials, such as niobium. This paper is based on a traditional quality assurance and quality control technique used to confirm mineralised intersection zones, and proposes the validation of sampling data using diamond drill twin holes, in order to evaluate and improve the quality of the current data set. The geological model of the niobium mine – located in Araxá, Minas Gerais, Brazil – was built including 77 diamond drill holes of a sampling campaign carried out during the 1970s. There are few records about the collection and preparation procedures of these past samples, making it difficult to estimate the errors associated with their analytical results. Therefore, 11 twin drill holes were drilled to compare their samples against the samples from the 1970s drilling campaign. The new hole locations were chosen as near as possible to the old holes location. The JORC Code, 2012 edition, relates the use of twin holes as a good sampling technique to assess sampling and assay data. Three parameters were considered to validate the 1970s drill hole campaign by the twin drill hole campaign: the difference of the coordinates between the paired holes the difference among the positions of the geological contacts to validate the geologic description the difference between the paired samples grades was calculated to validate the analytical results.The analysis of the grade range variation between sample pairs was based on three techniques: geostatistical interpretation of vertical semivariogram to obtain the nugget effect calculation of the relative difference between duplicates calculation of the error associated with the sampling protocol established according to Pierre Gy’s Theory of Sampling.The results were satisfactory for hole coordinates; however, the ore content showed a high deviation, although this divergence can be explained by the nugget effect. For the lithological intervals, the new results contributed to an effective identification of variations among lithologies, ie brown weathered ore and saprolite. The twin drill holes campaign successfully validated the geological model data, allowing effective mine planning and higher reliability of the reconciliation results.CITATION:Marques, M T G C, El Hajj, T M, Braga Jr, J M, Chieregati, A C and Delboni Jr, H, 2017. Theory of Sampling and geostatistics for twin drill holes analysis in a niobium mine in Araxá, Brazil, Australia, in Proceedings Eighth World Conference on Sampling and Blending, pp 97–106 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

May 9, 2017

By R. Karl Zipf, David Newman

The objective of this is paper is to review the current state of knowledge and practice in highwall mining (HWM). HWM has become a widely-applied method in surface mining, commonly used alone or in conjunction with contour or slot mining. It provides 800-feet to 1,200-feet of additional recovery when the economic stripping ratio is reached in contour mining or in slot mining when surface access to a reserve is limited. A significant attribute of the highwall miner is its versatility. HWM has been used successfully to mine abandoned pre-reclamation law highwalls, points or ridges uneconomic to mine by underground or other surface methods, outcrop barriers left adjacent to underground mines, separate benches of the same seam where the parting thickness or quality differences between benches render complete extraction uneconomic, previously augered areas containing otherwise inaccessible additional reserves and close or widely spaced multiple seams. The theory and design methods to assess roof, pillar, and floor stability are presented followed by three case histories. Simple design charts for sizing HWM web and barrier pillars are also presented. A recommended web pillar width may be obtained from the design charts given the overburden depth, the HWM cut width, and the mining height. Given the depth and panel width for a set of HWM cuts, another set of charts gives a suggested barrier pillar width. The case histories, from Northern and Southern Appalachia are used to illustrate the application of rock mechanics to quantify the stability of the highwall, roof, web pillars, and floor. The case histories involve 1) mining through a previously augered highwall, 2) mining under back-stacked spoil and 3) selective mining of closely spaced benches of the same seam. Because each site is unique, the appropriate pre-mining geotechnical analyses range from the calculation of roof, web pillar, and floor bearing capacity stability factors to detailed numerical modeling of the auger and underground mine workings. When operating in the vicinity of existing underground mine or auger workings, the determination of ground deformation and strains resulting from highwall mining is a necessary facet of a ground control investigation.

Industrial Minerals production in New Zealand is limited in both quantity and range, but imported in quantities that make New Zealand the world's biggest consumer per head of population. The use of industrial minerals is assured as both population and standard of living increase regularly. But to develop these minerals in the New Zealand environment requires the mineral, or its market (both local and export), to have characteristics that negate the remote geographical location. Volume and/or uniqueness can achieve this.

Jan 1, 1997

This paper characterizes the copper cycle, that is, the flows of copper entering and leaving the African economy over a one-year period (1994). The major flows over the entire life-cycle of copper are examined; these include production (mining, milling and refining), fabrication of semi-products and manufacturing of finished products, use, and the waste management system. The results reveal that substantial amounts of copper (of order705 Gg/yr) are mined in Africa; of that amount, about 70 per cent is exported following processing, 18 per cent is utilized by African fabricators, and 12 per cent is discarded. The flows of copper products from African fabricators and product imports from other continents exceed product discards by large amounts. This difference, about 0.25 kg Cu/capita/yr on average, is added to in-use stock, largely as wire, plumbing tube, and in electronics. Some 65 per cent of the copper in discard flows is contained in electrical and electronic products, where it is relatively easy to collect and process for reuse. About a third of the copper discard flows known is recycled. The actual percentage is almost certainly higher because of informal (and unrecorded) recycling. Much of the remaining discarded copper is diluted into the municipal waste stream, where recovery and recycling are probably not economically justified. Keywords: material flow analysis, resource management, material budgets, copper, stocks and flows, systems analysis, Africa, developing country

Jan 1, 2003

By L R. Marshall, M J. Rubenach, T G. Blenkinsop, J S. Cleverley

The source and transport regions of fluidised (transported) breccias outcrop in the Cloncurry Fe-oxide-Cu-Au district, providing insights into the origins of other fluidised magmatic-hydrothermal breccias such as kimberlites. Discordant dikes and pipes with rounded clasts of metasedimentary calc-silicate rocks and minor felsic and mafic intrusions extend several kilometres upwards and outwards from the contact aureole of the 1530 Ma Williams Batholith into overlying schists and amphibolites. The brecciation initiated at depths >10 km and may have resulted in surface breaching. We used analytical equations for particle transport to estimate clast velocities (eÆ 20 ms-1), approaching volcanic ejecta rates (up to 80 ms-1). The wide range of CO2 fluid inclusion densities (up to 150 MPa), the localisation of the base of the breccias in contact aureoles, and the scale and discordancy of the bodies suggests the breccia transport process was triggered by an abrupt release of overpressured fluid. At these depths, such extreme behaviour may have been achieved by release of dissolved fluids from crystallising magma, in combination with a strongly fractured and fluid-laden source, sitting under a strong, low permeability barrier, and such parameters may be analogous to the asthenosphere/lithosphere boundary in the case of kimberlite initiation. The relationship of these breccias to the Ernest Henry iron-oxide-Cu-Au deposit suggests they may have been either fertile or æfailedÆ orebody feeders.

Jan 1, 2005

By A. V. Peake

Continuous Mining presents an opportunity to extract reef in the stope ?continuously? by integrating the drill and blast activity using propellants or low energy charges. To date, the majority of effort spent on Continuous Mining systems has focused on developing an effective rock breaking process (micro breaking process), and to some extent, eliminating fumes and dust. The perceived benefits of applying low energy charges have been identified as: ?Concentrated mining yielding face advances of 40 to 60 m per month ?Lower stoping widths through better-controlled breaking ?Increase in the advance per blast ?Increase in labour productivity ?The potential to mine reefs where specific conditions make conventional mining uneconomic e.g. reefs with shales in the immediate hangingwall. However, the ability to successfully use low energy charges to create a ?Continuous or Semi-Continuous? mining method is dependent on overcoming the following challenges. ?Improving reliability of rock breaking. This is dependent upon achieving:? Improved drilling accuracy, and? Successful stemming or gas confinement, particularly in fractured rock ?Reducing gas and dust levels ?Reducing high costs. Through the research carried out in Future Mine, many different low energy rock breaking methods and systems were investigated. Whilst detailed results cannot be published here, the guidelines for overcoming low energy rock breaking challenges are discussed.

Jan 1, 2003