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By Bernhard C. Koch, Richard W. Hutchinson, Bernhard Free

The Tertiary Silverton caldera collapsed asymmetrically to the southwest 27.5 m.y. ago. Resurgent volcanic activity is expressed by a quartz-monzonite stock at the southern caldera margin and by the Red Mountain porphyry stock in the northwest of the caldera which were emplaced at 25 m.y. and 11 m.y. b.p., respectively. The apical Eureka graben formed between 27.5-22.5 m.y. ago and transects the Silverton caldera southwestward. In the northeast it terminates at the 22.5 m.y. Lake City caldera margin. This graben as well as caldera faults provide dominant structural control for base and precious metal deposits. The epithermal gold mineralization of the Gold King mine is proximal to the Red Mountain stock in the north central part of the caldera. Here, west-northwest striking faults related to the collapse of the caldera intersect northeast faults of the Eureka graben. Superimposed upon earlier base metal mineralization at 23 to 22.5 m.y. b.p., the 11 m.y. younger gold metallization was a distinct event at Gold King. Supergene enrichment of the hypogene precious metal assemblage resulted in a metal tenor of up to 3,016 g/t gold and 1,088 g/t silver. The deposit is hosted by quartz-latite tuffs, flows, and flow breccias of the Burns Formation. Veins, up to 5 m wide follow steeply southeast and northwest dipping structures of the Eureka graben. Subsidiary veins up to 2 m wide branch off the main lode and are termed "flat veins" because of their conformable strike but shallow dip of 45' to 50' toward the northwest. Meteoric water-dominated hydrothermal solutions generated by the Red Mountain stock ascended through intensely fractured, ferruginous

Jan 1, 1988

By M A. Mongillo

Most geophysical and geochemical data collected during regional exploration programmes are in vector form (location, value), and have traditionally been presented and interpreted in a profile or contour map format. However, the human vision system can interpret data presented in image format much more easily and new information is often revealed by the judicious application of powerful interactive computer image enhancement techniques. This paper describes a practical demonstration of the application of such tools to gravity and resistivity datasets from the Central Volcanic Region of theNorth Island.   Filtering, contrast enhancement, relief shading, pseudo-colouring and then overlaying of the gridded datasets in image format has helped identify inter-relationships such as the association between many low resistivity anomalies (epithermal deposits or geothermal resources) and the edges of large gravity anomalies (calderas or grabens). Similar revelations should result from the application of these tools to the integration of other mapped datasets from geophysical, geochemical and geological disciplines.

Jan 1, 1992

By Bruce Conard

For many years, Bruce Conard has been engaged in reading about and discussing the desired sustainability of the mining and metals resource industry. He has, however, become concerned that there is a greater issue that requires our urgent attention: what challenges do we face as a global society? His Distinguished Lecturer presentation traces the idea of environmentally sustainable economic development but concludes that a business’ interest in its sustainability is predicated on the sustainability of our global society. Conard reviews some of the most serious challenges, including population growth, clean energy supplies, freshwater availability and climate change, and calls on scientists and engineers not only to apply their skills in helping solve these challenges, but most urgently, to speak with intelligence and passion about the need to act now.

Jan 1, 2014

By Bianka Nani Venturelli

Estudou-se o efeito do tamanho de grão austenítico nas propriedades de tração do aço Hadfield refinado com Hf. Estas propriedades foram comparadas com as de um aço Hadfield sem refino, ambos com a composição química de acordo com a norma ASTM A128 – grau B2. Adicionalmente, foram usadas técnicas de caracterização macroestrutural, microestrutural e fractográfica. A caracterização macroestrutural mostrou que o aço Hadfield com adição de Hf apresentou tamanho do grão austenítico (600 ?m) aproximadamente cinco vezes menor do que o do aço Hadfield sem refino (3000 ?m). Os resultados do ensaio de tração mostraram um pequeno aumento (~6%) no valor do limite de escoamento com o refino do grão, em acordo com a Equação de Hall-Petch para materiais austeníticos. No entanto, os resultados dos ensaios de tração do aço Hadfield refinado mostraram aumentos que não foram previstos para as propriedades de resistência à tração (~37%), alongamento (~53%) e tenacidade (~88%). O exame fractográfico dos corpos de prova de tração indicou predominância do mecanismo de fratura dúctil para o aço Hadfield sem refino, enquanto que o aço Hadfield refinado apresentou predominância do mecanismo de fratura intergranular dúctil.

Oct 30, 2017

By G. K. Mann

Fragmentation analysis of blast or crushed rock material is a time-consuming and costly process. During the last two decades, the mining industry has been investigating image-based analysis systems as an alternative to generate fragmentation results. Many image-based techniques and commercial products have emerged during the last few years, and the mining industry has recently begun using these tools for real-time estimation of size distributions. Some existing systems require manual image editing to add or delete edges (or net) before executing the fragmentation analysis routine. This manual procedure may take hours of time for each image analyzed. Reliable and robust image segmentation should be able to handle a wide range of rock textures and sizes under a variety of lighting conditions. This paper describes a novel software application, which has the capability to autonomously capture images and analyze them to generate the particle size distribution. The system can also process a batch of images captured during a fixed duration of time and produce the overall particle size distribution. The new method has different layers of segmentation modules, which allows the system to operate under a wide range of rock textures and lighting conditions. A new grey-level slicing technique is developed which can perform under a range of illuminating conditions. The Canny-based edge detection technique is used to segment rocks appearing in dark regions.

Jan 1, 2006

By Parker A. J, Giles D. E

Solutions of copper(II) sulphate in acidified aqueous acetonitrile leach copper from copper-lead matte derived from the drossing of lead with sulphur to produce solutions of copper(I) sulphate. The reactivity of the matte constituents towards copper(II) sulphate is Cu2S> PbS > CuS > > Pb. According to the leach conditions, part or ,all of the copper may be leached 'leaving a residue of CuS/PbS, or S/CuS/PbS04, or S/PbS04, to be recycled to the lead smelter. Complete extraction of the copper requires leaching with oxygen which occurs under mild conditions in the presence of acetonitrile and sulphuric acid in water. Copper is selectively recovered as a pure product by electrochemical or thermal disproportionation of copper(I) sulphate solutions. A notional process is proposed.

Jan 1, 1979

By Maral Papazian Bedian

Construction contracts in the USA contain the clause "Value Engineering" ? an interesting and curious clause allowing contractor initiated design changes. Misleading is the interpretation of value engineering implying cost saving and sharing with the owner, and curious is the timing, just before beginning of actual construction. It is not surprising that such a clause would simply be ignored, because it involves change, often major design changes in very short time; and change is feared, moreover, it is vehemently resisted by all parties, owner, designer, contractor. The problem in the USA may lie in the divergence and separation of the two entities: Designer/Engineer and Builder/Contractor, assigned to the "one" engineering project. The priorities and incentives of these two groups are very different. The Engineer spends years, even decades, in design and prepares contract drawings often without a deep understanding of construction methods. Worse, with all the time available to him and in our era of tremendous advances in computational methods and speed, the designer turns in plans that are inexcusably exaggerated code-based design with excessive safety factors. As to the Contractor, he builds, often without appreciation of design principles or regard for design engineers. Redesign to apply a new technology or optimization of an inferior design just before construction becomes unthinkable. It is not surprising that adverse and hostile relationship between the designer and the contractor is a norm with extended disputes and claims, not to mention the cost these entail. Surprisingly, "Value Engineering" was successfully implemented in record speed on several very large projects in the metropolitan New York area. The process of change was unconventional, painful, and even comical. Four case studies are presented: two Design/Build: the 1.2 billion dollars Hudson-Bergen Light Rail Transit System in New Jersey and the 90 million dollars MTA Bus Depot in Manhattan, and two Conventional Design/Bid/Build: the 90 million dollars Queens Boulevard Bridge and the 150 million dollars Long Island Expressway.

Jan 1, 2002

Keywords: Pyrometallurgy, Wits University, research Wits Metallurgy celebrated its centenary in 2004. The department has been at the forefront of education and research and has contributed greatly to the metals and minerals industry, both in South Africa and abroad, in terms of human resources and knowledge generation. A significant number of industry and academic leaders worldwide are Wits Metallurgy graduates. Since its early beginnings, pyrometallurgy has always been part of the curricula and research offered by the department. Pyrometallurgical activities started to expand tremendously from the middle of the 1960s, especially by the formation - together with Mintek - of the Pyrometallurgy Research Group, which continues its internationally recognised research activities today. The research efforts have been concentrated on problems associated particularly with ferroalloy, steel, stainless steel production, and PGM/Cu-Ni sulphide smelting. In recent years, research has been further expanded to physical modelling of pyrometallurgical reactors. Almost all of the specific research projects were handled from a fundamental point of view, and hence a large number of MSc(Eng) and PhD degrees were achieved by candidates under the supervision of the Pyrometallurgy Research Leaders. Moreover, a significant portion of the research results were published in internationally recognized journals and conference proceedings. Among these, Infacon and the Molten Slags, Fluxes and Salts Conference series are worth mentioning. The studies from a fundamental point of view include thermodynamics, phase equilibria, transport phenomena, kinetics, and process dynamic aspects of high temperature processes and systems, both in the solid and liquid states.

Jan 1, 2006

By Conochie D. S, Grave N. C

Disposable-tip emf cells at present used in liquid steel can be used to measure the state of oxidation of high-iron slags produced in non-ferrous smelting. This provides a new tool for the control and evaluation of pyrometallurgical operations.An investigation of oxygen potential variations throughout a typical nickel smelter using the flash smelting technique gave a valuable insight into the process. Correlations of oxygen potential with ferric to ferrous oxide ratio and nickel content in slag were in reasonable accord with equilibrium data in the literature indicating that the probes may be used both as a plant investigation tool and possibly as a means of obtaining thermodynamic data for slags.

Jan 1, 1979

By Reeves M

A review of the literature available in English on kriging and geostatistics is given with the references cross-classified by their subject matter for convenience and ease of use.

Jan 1, 1979

By José Rogério de Oliveira Júnior

Neste trabalho foi determinada a influência do tamanho e da densidade de partículas sobre a perda magnética de um aço silício de grão não orientado (GNO) contendo 2%Si. Amostras provenientes de bobinas laminadas a frio após recozimento final, com dimensões de 305x30x0,54mm e teores de carbono 32 ppm e 46 ppm, foram submetidas a tratamentos de envelhecimento de 100 até 225ºC. A evolução da perda magnética durante o tratamento térmico de envelhecimento foi determinada interrompendo-se o tratamento em intervalos de tempo variados e realizando-se os testes magnéticos. Completado o ciclo de envelhecimento, todas as amostras foram avaliadas no microscópio eletrônico de varredura (MEV) para caracterização dos precipitados. Os resultados determinaram que o aumento da perda magnética ao longo do tempo, para uma dada temperatura, está associado à precipitação de carbonetos. O maior aumento da perda magnética encontrado correspondeu a uma distribuição de precipitados com tamanho médio entre 1,1 µm e 1,3 µm e a uma densidade de partículas de 0,025 partículas/µm2.

Aug 7, 2018

By Ashley P, Neale T

Alluvial gold was discovered on Sudest Island in 1888, and by 1893, an official production of 10 000 oz had been won by expatriate miners from shallow alluvial and colluvial workings. Hardrock sources were located and while one was developed at Mt Adelaide, production is unknown. Sudest Island comprises mostly phyllites and lesser coarse grained rocks which are cut by metamorphic quartz veins and basic (locally shoshonitic) intrusives. Sheared and altered basalts and serpent- inites represent are believed to be elements of an ophiolitic suite inferred to be associated with metamorphic core complex development and thus similar to tectonic environments on Misima and the D'Entrec- asteaux Islands. No epithermal-style quartz suggestive of a target similar to that on Misima Island has been identified on Sudest. A hardrock source for the alluvial and colluvial gold is interpreted to be metamorphic quartz veins similar to those in the Bendigo- Ballarat Zone of central Victoria, possibly remobilising gold derived from the meta- sedimentary and meta-igneous rock pile. The present focus is on development of a small scale alluvial gold mining operation in conjunction with exploration for hardrock targets. This latter programme remains at a reconnaissance stage.

Jan 1, 1991

By Artur Camposo Pereira

As fibras naturais foram estudadas como um material de reforço alternativo para substituir o uso de fibras sintéticas. Com o objetivo de melhorar as propriedades dos compostos de fibras naturais, é investigado o uso de tecidos de fibras naturais, uma vez que proporcionam reforço multidirecional e permite a introdução de uma fração de volume de fibra maior. Neste trabalho, investigou-se o comportamento de tração de compósitos de matriz epóxi reforçados com diferentes frações de volume de tecido feito de rami, uma fibra lignocelulósica altamente resistente. Os espécimes foram feitos pressionando o tecido com resina epóxi para garantir a impregnação total, e depois cortando o tecido no formato do molde. Finalmente, as camadas de tecido foram colocadas no molde com a resina líquida e o catalisador. O material foi curado durante 24 horas e testado. Os resultados revelaram um aumento na resistência à tração e quase nenhum efeito no módulo de elasticidade com o aumento da fração do volume do tecido.

Oct 30, 2017

By K. Oraee

The empirical rock failure criteria play an important role in predicting the mechanical behavior of rocks, since affecting parameters on the behavioral properties of rocks are complex and numerous. Usually the empirical failure criteria are obtained by statistical methods, namely by means of fitting the mathematical function onto the experimental data. For evaluation and verification of the results, however, the quality and accuracy of the fit must be considered. This paper studies the efficiency and accuracy of conventional empirical rock failure criteria using a new approach, which is based on the analysis of uncertainty amplitude on the constant parameters of each criterion. The approach adopted here, is based on the combination of some parameters such as Mean Squared Error (MSE), Root Mean Squared Error (RMSE), type of function, degree of freedom and the confidence level of constants. Correlation coefficient (R2) is then a comprehensive test and can be used effectively for comparison and accuracy of empirical rock failure criteria.

Jan 1, 2012

By Faruk Oksuz, Phillip L. Covell, Martin Doll

A series of difficult ground conditions causing high groundwater inflows and hazardous gas intrusion abruptly halted the construction of a 6.4-meter (21-foot) finished diameter and 1,890 meters (6,200 feet) long tunnel planned to serve as a 4-millioncubic meters (1-billion gallon) per day capacity river outfall for treated wastewater. Some 808-meters (2,650-feet) section of the constructed tunnel, TBM, and all other tunneling equipment were completely flooded with hydrogen sulfide laden artesian groundwater. The subsequent pumping and tunnel recovery efforts were unsuccessful and the tunnel was abandoned. In the end, the construction contract was terminated and options to redesign and reconstruct the project were re-evaluated to maximize the use of already constructed tunnel facilities such as the construction access and inter-mediate shafts and six outfall diffuser shafts in the river.

Jan 1, 2007

THIS paper is the outcome of experiments carried on and experience gained. at the Waihi-Paeroa Gold Extraction Company's tailings plant at Waihi, New Zealand. The plant was erected to treat accumulated tailings which had been discharged into the Chinemuri River by the Waihi batteries.The Chinemuri River is a common sludge channel for all mining debris, tailings, and ashes from the power plants, the last being the cause of occasional high residues, which gave so much trouble to the management. The tailings were dredged from the bed of the river into barges by means of a Pohle air lift, the power being supplied: by a 13 b.h.p. Tangye oil engine driving an air compressor and a centrifugal pump. The sands were elevated from the barges by bucket-belt elevators over screens, to eliminate large particles and rubbish, into storage hoppers, and from there fed direct into four C. Judd Ltd. tube mills.The method of treatment was fine grinding in a weak cyanide solution, agitation in B. and M. tanks, filtration with turn-over vacuum filters, and precipitation with zinc shavings. The comparatively high values of the residues in gold gave a great deal of trouble, 'and it was not until repeated experiments were carried out that the cause of the trouble was located. While the value of silver residues remained stationary, the gold values...

Jan 1, 1912

By B. S. Gottfried

This paper is concerned with possible transport mechanisms which occur during segregated burning (i.e., burning in an oil reservoir in which the oil-bearing formation is overlain by a "clean" porous zone containing only gas). ,Two analytical models are presented. In the first, burning is assumed to occur at the gas-oil interface, and the dominant mechanism is taken to be the rate at which oxygen diffuses to the interface. The second model assumes that combustion occurs within the clean zone, with the dominant mechanism being the mechanism of fuel deposition from the oil-bearing formation to the clean zone. ,Comparison of the results of the analyses with limited experimental data indicates that the latter mechanism is much more plausible. Both models are idealized representations of the actual process and are somewhat conjectural, however, owing to the lack of more definitive laboratory or field data. INTRODUCTION In recent years there has been considerable theoretical and experimental research directed toward understanding the recovery of crude oil by underground combustion. Although two different recovery schemes have been proposed, known as forward and reverse combustion, it is only forward combustion that shows promise of becoming a practical recovery technique.17 Most of the analyses of the forward combustion process have considered it to be pistonlike; i.e., oil is displaced by a vertical combustion zone which, with its ensuing gases, pushes die oil forward as the flame front is propagated through the reservoir.l-8,ll,l2,14-16 However, information gained in field pilot studies indicates that, at least to a certain extent, forward combustion proceeds in a segregated manner in oil reservoirs.10 An ideal segregated system is one in which the oil-bearing formation is overlain by a "clean" porous zone containing only gas. The location of the combustion zone in such a system is not immediately evident, although combustion is believed to occur either at the gas-oil interface or within the clean zone. In either case, the combustion zone may be horizontal and it moves in parallel rather than in series with the produced oil. The purpose of this paper is to explore the likely mechanisms by which segregated burning can occur, and to determine the sensitivity of the resulting models to changes in various physical parameters. Two governing mechanisms are considered: the case of a horizontal combustion zone at the gas-oil interface with the rate of combustion governed by the rate at which oxygen diffuses to the interface, and the case of combustion within the clean zone with the combustion process controlled by the transport of fuel from the oil-bearing formation to the clean zone. Both models are somewhat hypothetical and involve considerable simplification of the actual process. However, the results allow some preliminary understanding of segregated burning which is useful in the absence of more definitive laboratory or field pilot data.

Jan 1, 1967

By K. Ward

The Environmental Protection Agency (EPA) is beginning to provide compliance assistance visits to various industries, including mining, for Emergency Planning and Community Right-to-Know Act (EPCRA) compliance. The EPA inspectors may consist of a multi-media team deployed to review systems and procedures for EPCRA Sections 302, 304, 311, and 312. The Team’s focus may include emergency response plans, training programs, qualifications of personnel, and release notification protocols. This presentation takes a look at the EPCRA compliance challenges faced by Arizona copper mining and processing facilities.

Jan 1, 2001

By w. w. Milde

"Since its startup in 1975, the Rabbit Lake mill has been modified (0 process both increased tonnage and higher grade ore. Ore initially came from the Rabbit Lake pit . In 1985, a major mill expansion was commissioned to allow treatment of B-zone pit ore, which is mineralogically and metallurgically different fromRabbit Lake pit ore.Mill modifications, and the changing ore characteristics and processing targets which made them necessary, are described. Mill LocationThe mill complex, shown in Figure I, comprised of milling facilities, acid plant, power generation , warehouse and administration offices, is located approximately 1.5 Ian south of the Rabbit Lake pit, and about 8 Ian southwest of the B-zone open pit mine.Original Milling CircuitOre feed to the mill commenced June 10, 1975. The mill was designed to process 1500 tonnes per day , 483 000 tonnes per year with an average grade of O.44OJo Ups and an annual production of 2000 tonnes UPs' Run-of-mine ore was dumped directly onto a 60 em square opening grizzly. Oversize was broken with an Ingersoll-Rand hydrauli c rock breaker. Minus 60 cm ore was fed to a 6 m diameter by 1.8 m long Hardinge semi-autogenous (SAG) grate discharge mill. Mill discharge was screened over a Tyler double-deck vibrating screen, with screen oversize returned to the SAG mill feed chute via conveyor belt. Screen undersize (minus 2.4 mm) was pumped to 51 cm diameter Krebs cyclones in closed circuit with the SAG mill. Cyclone overflow (about 50% minus 74 micron) was thickened to 55% solids in a 30 m diameter neutral thickener .Thickened pulp was stored in two mechanically-agitated wood stave tanks (5.5 m diameter by 6 m high), to which sulphuric acid was added to obtain a pH range of 1.5 to 2.0. The fmalleaching was carried out in five more identical tanks. Sulphuric acid and sodium chlorate were used to maintain a pH of 1.5 and a terminal emf of -450 to -500 mV. Steam sparge was utilized to obtain a temperature of 45°C."

Jan 1, 1989

Shaft sinking through an amphibolite-granite rock mass experienced rock bursts on the shaft walls and benches. However, rock burst phenomena was exhibited only in granite, which is e1asto-brittle with ability to store strain energy caused by orogenic and man made stresses. To improve ground conditions, blasting of destressing holes at shaft corners was carried out. By this technique rock burst during shaft sinking was minimized, but not eliminated.

Jan 1, 1982