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By Gao Zhinzhong, Gu Zhengxing

China abounds with phosphate resources, but most of them are of old geological age, have high dolomite and other impurities, and are fine grained. Prior to beneficiation, fine grinding is usually required for liberating impurity minerals from phosphate. These deposits are perhaps the most difficult to treat phosphate ores in the world. In its 30-year campaign for efficient utilization of indigenous phosphate resources in China, the Lianyungang Design and Research Institute (CLDRI) has developed fine-particle flotation technology for beneficiation of such low-quality phosphate ores. The processes of direct flotation using L or S series depressants and carbonate flotation have been successfully applied on industrial scale with very satisfactory results. This paper introduces three phosphate beneficiation practices in China: the Jinping plant of Jiangsu province, the Dayukou plant of Hubei, and the Wengfu plant of Guizhou.

Jan 1, 1999

By H. Y. Jennings

An extensive field and laboratory experimental program was carried out to compare the waterflood behavior of carefully preserved soft and unconsolidated cores with measurements on the same cores after extraction. Results obtained from using idealized consolidated and unconsolidated porous media in which wettability could be carefully controlled were contrasted with the preserved core data. The controlled tests on idealized porous media investigated the effect of wettability, flood rate, core length, core permeability and consolidation on the displacement of high viscosity oils. It was concluded from these studies that waterfloods are more favorable when carried out with crude oil in preserved soft and unconsolidated cores than with the same cores after they have been extracted and re-saturated. Waterfloods are usually more favorable when carried out with crude oil in extracted .soft and unconsolidated cores than with refined oil of the .same viscosity in the same cores. The less favorable behavior of extracted soft and unconsolidated cores compared to preserved cores is due to alteration of the core by extraction. Preserved cores saturated with native water and oil should be used for laboratory displacement experiments because they more accurately reflect true reservoir behavior INTRODUCTION The demand for low gravity crude oil created by refinery modernization has focused attention on increasing the production of this viscous crude oil. Billions of barrels are in place in fields that are depleted, or nearly depleted, by primary production mechanisms. Since low gravity reservoirs are relatively recent, geologically, the solid matrix material is usually soft and unconsolidated sand. Such formations are also characterized by a high clay content. Evaluation of sophisticated oil recovery processes with the associated high capital investments has increased the demand for special core analysis tests on material from these soft and unconsolidated sand reservoirs. Data in this paper have resulted from an extensive field and laboratory experimental program. The initial objective vras to provide soft and unconsolidated sand cores for laboratory measurements with as little alteration as possible from their reservoir condition. A secondary objective was to compare the waterflood behavior of these carefully preserved cores with measurements on the same cores after they had been extracted and resaturated. When the comparison showed markedly different behavior the final objective was to attempt to explain the difference by making measurements on idealized porous media free of clay in which initial wettability could be carefully controlled. EXPERIMENTS MATERIALS Core Material The preserved cores used in this study were obtained with as little alteration as possible from their reservoir conditions. Special techniques were developed to satisfy this objective. The cores were cut with native crude whenever the crude had the necessary properties to satisfy the minimum drilling fluid requirements. A pure hydrocarbon chromatographic tracer was added to the crude to provide a simple, safe and inexpensive method to distinguish between oil filtrate and formation oil. Details of the tracer technique used in this study and the procedures used to handle and process the soft, unconsolidated cores have been published.' The core samples were then preserved and packaged at the well site with a dip-applied strippable plastic, or by using a rubber sleeve from a rubber-sleeve core barrel. The final step was to insure that the carefully taken and preserved samples were not altered by processing in the laboratory. Some soft and poorly consolidated sands were carefully shaped in the lab and encased in a protective mounting without disturbing their three-dimensional integrity. Many samples were so poorly consolidated that they literally flowed from the package when the seal was broken. A technique was developed to obtain cylindrical plugs from these samples by using liquid nitrogen as the drilling fluid in a conventional core-drill, drill-press assembly. The idealized porous media consisted of sintered rods of Alundum RA 139, outcrop sandstone identified as Al-hambra sandstone and packs of No. 130 Nevada sand. This sand is 95 per cent 140-200 mesh. (Physical properties of these porous media with those representative of preserved cores are in Table 1.) The natural cores and most of the idealized porous media were 1 1/2-in. in diameter and 3-in. long. The samples used to study the effect of core length were 1 1/2-in. in diameter and 12-in. long. Liquids Water and oil produced from the formations being studied were protected from the atmosphere and collected in carefully cleaned glass or plastic-lined containers. The production was free of chemical additives such as emulsion breakers and corrosion inhibitors. The crude oil was

Jan 1, 1967

By Waldemar Dyrssen

BEFORE discussing the relation between air pre-heaters and waste-heat boilers in conjunction with the open-hearth furnace, it is necessary to have a clear idea about what a preheater can accomplish and what effect it has on the open-hearth furnace, especially from a thermal point of view. It is generally recognized now that the heating of the combustion air in the checker chambers of the open-hearth furnaces is not as efficient as it is-desirable to make it. It is also generally recognized that heating of the air in checker chambers of ordinary construction has its limitations. These limitations are mostly the .space occupied and the cost that would be involved if checker chambers were made larger than according to present practice. There are, however, other. reasons why checker chambers cannot give the highest possible air temperatures. Checker chambers are capable of heating air to very 'high temperatures by using waste gases of extremely high temperatures and, in fact, higher temperatures can be reached with checker chambers than with any other means available. The temperature to which we can heat, air, however, is limited very materially by -the temperature at which the air enters the checkers, be-cause of the fact that checker chambers, as at present constructed, are not efficient in heating air through a wide range of temperatures. In other words, if air in-stead of entering the checker chambers at atmospheric temperatures could enter at about 1000 to 1200 deg. F., the resultant air temperature at the top of the checker chambers would be materially increased. There are now on the market metallic air preheaters which are ex-tremely efficient for preheating air to about 1200 deg. F. Such heaters occupy very little space and can usually be installed at a relatively low cost.

Jan 1, 1928

By L. Diestelow

Evaporation and crystallization processes are used extensively in the mining industry to provide many pro-ducts. In the case of solution mining evaporators are used to concentrate, or to concentrate and crystallize the raw materials being mined. In the case of underground, or strip mining dissolving and crystallization are used in many processes in order to purify the ore to saleable materials. Presently evaporators and crystallizers are being used in the production of sodium chloride, potassium chloride, sodium carbonate, sodium sulfate, lithium chemicals, aluminum, and many others. The evaporator is a device designed to remove water or solvent from a solution. In an evaporator the energy released by steam condensing on one side of the heat transfer surface is transferred to the product solution on the other side of the heat transfer surface. As long as the boiling temperature of the product liquor is below the condensing temperature of the steam, the product solution will absorb heat. This heat absorption causes vaporization of the water (solvent) in the product solution resulting in concentration of the product. The simplest evaporator is the single effect evaporator. If we assume the feed introduced into the single effect evaporator is at its boiling point, ignore radiation losses, and assume the steam into the heat exchanger is dry and saturated, then the heat transferred will correspond to the latent heat of vaporization. Therefore, one kilogram of condensing steam will produce one kilogram of evaporation. Economies in energy usage compared to the single effect evaporator can be made by using multiple effect evaporators, or vapor recompression evaporators.

Jan 1, 1993

By Hans-Christian Kurzweil, Klaus Mussger

CERN, the European Laboratory for Particle Physics, are upgrading their existing particle accelerator for the next generation of experiments and have three major packages of underground construction work in progress. Each package involves the construction of shafts, cavern, tunnels and surface buildings. This paper gives an overview of CERN, the LHC Project and a more detailed discussion of design process, design review and construction works of Experimental Point 5. The LHC works at Point 5 include two large shafts, two major parallel caverns with a total span of 50 m, which are separated by a 7 m wide and 28 m high concrete pillar, and a system of secondary tunnels and caverns. The overburden ground consists of around 50 m of water bearing moraine (silty, clayey gravels and sands) overlying 20 mof molasse, which consists of horizontally bedded marls and sandstones. The shaft shave been constructed with ground freezing, primary concrete lining, membrane and secondary slip formed concrete lining. The concrete pillar was then excavated and concreted in advance of excavation of the two caverns. Cavern construction includes primary support of shotcrete lining and rock bolts, followed by waterproof membrane and primary support of shotcrete lining and rock bolts, followed by water proof membrane and insitu concrete secondary lining.

Jan 1, 2003

By J. A. Bailey, J. H. Tundermann

The dihedral angles of the solid-liquid interfaces were measured at various temperatures above the solidus and the interfacial energies calculated when small additions of copper, indium, lithium, magnesium, antimony, and silicon were made to an aluminum alloy containing 3 pct Sn. When the results were compared with those of the Al-Sn alloy some differences were found which could be interpreted in terms of the ability of the added element to enter into solution or form intermetallic compounds with the aluminum and tin. It was shown that in some cases considerable changes in the shape of intergvanular liquid films can be brought about by comparatively small compositional changes in the alloy. DURING the melting or solidification of an alloy a temperature range is usually found where the presence of a liquid phase may be detected at the grain boundaries of a solid. It is believed that the presence of this liquid phase is responsible for hot tearing in castings and welds and hot shortness in the working of some alloys at elevated temperatures. Rosenberg, Flemings, and Taylor1 in a study of the solidification of aluminum castings have indicated the importance of intergranular liquid films and shown that their shape and distribution at the end of solidification effect the hot tearing characteristics of the material. The shape of such intergranular liquid films are determined largely by the ratio between the solid-liquid interfacial energy (yLS) and the grain boundary energy (ySS). A measure of this ratio (yLS/ySS , relative interfacial energy) is the dihedral angle 8. The dihedral angle 0 is related to the relative interfacial energy by the following expression: Rogerson and Borland 2 have also suggested that the shape of the intergranular liquid is an important factor in determining the susceptibility of a material to hot shortness. They showed that on a comparative basis materials having the lowest dihedral angles at a given temperature gave the greatest severity of cracking. They stated that liquid in the form of globules should be less harmful than liquid in the form of extensive films as more intergranular cohesion should be possible. Rogerson and Borlland 2 also showed that the susceptibility of an A1-Sn alloy to hot cracking can be reduced by small additions of cad- mium. It was found that the cadmium gave an increase in the dihedral angle at all temperatures. Ikeuye and smith3 investigated changes in the dihedral angle and relative interfacial energy with temperature for a number of ternary alloys formed when small additions of bismuth, cadmium, copper, lead, and zinc were made to an A1-Sn alloy. They found that in most instances changes in the dihedral angle were caused by compositional changes in the liquid phase; as the composition of the liquid approached that of the solid the dihedral angle decreased. They noted that the addition of a third element which was soluble in both the liquid and solid phases at a given temperature may decrease the dihedral angle (e.g., the addition of copper or zinc) but otherwise the ternary alloys formed exhibited dihedral angles between those of the A1-Sn binary alloy and those of the binary alloy of aluminum with the added element. Dwarakadasa and Krishnan4 investigated the changes in dihedral angle and relative interfacial energy with temperature when small additions of magnesium, iron, silicon, manganese, sulfur, cobalt, and silver were made to a copper alloy containing 3 pct Bi. They found that in all cases the added elements gave an increase in the dihedral angle and relative interfacial energy when compared with the values obtained for the simple binary alloy at the same temperature. It was noted that an increase in temperature gave a decrease in dihedral angle and relative interfacial energy in each of the ternary alloys studied. Similar results have been obtained by Ramachandran and Krishnan5 for the addition of small quantities of lead. This paper describes the application of dihedral angle measurement to the determination of the shapes of liquid phases at various temperatures above the solidus when small additions of copper, indium, magnesium, lithium, antimony, and silicon are made to an aluminum alloy containing nominally 3 pct Sn. An attempt is made to correlate the measurements with the relative solubility of the added elements in tin and aluminum. The work was undertaken to provide more data concerning the effects of temperature and composition on the shape of liquid films above the solidus. EXPERIMENTAL PROCEDURE In the present work ternary aluminum alloys containing nominally 3 pct Sn and small additions of high-purity copper, indium, lithium, magnesium, antimony, and silicon were made. The alloys were melted in a graphite crucible under an inert atmosphere of argon and cast into ingots 6 in. long by 0.5 in. diam. The ingots were then cut into rods 1.5 in. long, given a 50 pct cold reduction, and machined into test pieces 0.5 in. long by 0.5 in, diam for heat treatment. The alloy samples were annealed at the various test temperatures between the liquidus and solidus for approxi-

Jan 1, 1967

By David De Klerk, Maximilian Richter, Thirunavukkarasu Pathmathas, Indresan Govender

We consider the average power dissipation distribution for dense granular flows of an idealised mono-sized charge (5 mm glass beads) in a 300 mm diameter tumbling mill operated in the cascading-to-cataracting Froude regime. By combining the inherent frictional nature of particles within a dense flow regime and noting that tumbling mills are typically characterised by collisional and turbulent stresses, we derive the power dissipation distribution for athermal boundary conditions. The input data to the model (velocity, solids concentration, pressure and flow depth) are obtained directly from non-invasive measurement using a nuclear imaging technique: Positron Emission Particle tracking (PEPT). The power dissipation due shear stresses is shown to be the dominant mode of dissipation in the tumbling mill with up to two orders of magnitude difference between pressure induced dissipation and shear.

Jan 1, 2014

By M. I. Brittan

Discussion Dr R. E. Robinson (Fellow): The author must be congratulated on a very meticulous and self-contained piece of work. It is indeed a pleasure to read a paper that is so clearly and systematically laid out, and where the conclusions and the testwork conducted have been so clearly described. The paper is complete in itself, which makes it very difficult for someone who is not intimately involved in the whole Torco project to make any comments on its content. However, two points that, strictly speaking, fall outside the scope of the paper are of considerable interest. The first relates to the particle size of the material treated. In the paper, the testwork is confined to one standard particle size (minus 60 plus 100 mesh). The essential feature of the paper is to indicate that the rate-controlling reaction in the whole segregation process is the rate of reaction of the ore particles with the reducing agent and the hydrogen chloride. One wonders, therefore, to what extent this relatively slow rate of reaction is affected by the particle size of the ore itself. One imagines that the reaction must take place by contact of the hydrogen chloride with the surface of the mineral particles, and it is reasonable to suspect that the rate of diffusion of the copper ions to the surface is a relatively slow process and is thus the limiting factor in this particular rate of reaction. It is possible, for example, that the improvement obtained, when the ore is subjected to reducing conditions before the chlorination, is due to a breakdown in the crystal structure of the original particle. This breakdown is brought about by the reduction and by the consequent increase in surface area available for reaction with hydrogen chloride. Can the author indicate whether any work has been done along these lines, and whether it has been established that the reaction depends on the surface area available? The second point relates to the application of this kinetic study to the actual operation of a Torco reactor. It was once planned to feed the sodium chloride, together with the reducing agent, into the top of the segregation chamber. In the paper, the author mentions that it has now been established that the segregation chamber behaves, to all intents and purposes, as a fluidized bed, and that there is, therefore, a rapid evolution of gas in the lower regions of the chamber, which, it is imagined, displaces the gas phase rapidly. Since the reaction between sodium chloride, water vapour, and the aluminium silicates in the ore is extremely rapid, one wonders how much of the hydrogen chloride produced is removed from the reaction zone before it has had time to react with the copper minerals. The extremely low consumption of sodium chloride (which is a vital feature of the Torco process) must depend on an extremely rapid circulation of the hydrogen chloride gas to all the ore particles in the segregation chamber. One wonders, therefore, if a system for the introduction of the sodium chloride into the bottom regions of the chamber might not result in even greater efficiency in the utilization of sodium chloride. ProC D. D. Howat (Fellow): All of us who have been concerned with the study of chemical reactions at high temperatures are keenly interested in kinetics and are well aware that this is not an easy study experimentally. Dr. Brittan is to be congratulated on the development of neat experimental methods and for his full discussion of the results obtained. Although the segregation process for the extraction of copper from oxide and silicate ores has been known for almost fifty years, the fundamental chemical and physical changes involved have been little understood and the fundamental data are very scanty. The work now in progress at A.A.R.L., together with that sponsored by the Anglo American Corporation in other research institutions throughout the world, is bound to produce new fundamental data and a much more complete understanding of this rather fascinating process. It is already apparent that some of the old and well-worn chemical reactions that were postulated to occur, just cannot take place in the way which was formerly accepted. Dr Brittan's work, carefully conducted and thoroughly analyzed as it has been, still leaves us with one great outstanding problem. The thermodynamic data and the possible reactions set out in Table I (page 281) of his paper leave us asking, in complete despair, how can copper be converted into a volatile chloride in the presence of HCl, CO and carbon at temperatures about 800°C? The thermodynamics all combine to show that copper should be reduced to metal as the first step in the process. This brings us right up against the second problem. If copper were reduced to the metal how would HCI convert it to the volatile chloride? On top of these problems is the unknown reason for the very high speed of reaction between CO, HCI and the ground copper ore. Still further into the region of the unknown is the reaction by which gaseous hydrochloric acid is produced in the actual process. Perhaps Dr Brittan is feeling grateful that he doesn't have to try to explain this reaction-at this stage of the research programme at least. The results very clearly show that both CO and HCl gas are essential for rapid production of the volatile copper chloride. Dr Brittan states that 18 minutes were required to attain 83 per cent extraction with HCl gas alone and this was reduced to 4 minutes when CO was

Jan 2, 1970

By Norbert Steiner

For the desulfurization of weak SO2 gas streams, Degussa developed a process using dilute H2SO4 solution containing H2O, instead of conventional gas scrubbing with all solid absorbent medium (limestone, MgO). The process is based on fast reaction of H2O, with SO2 yielding H2SO4 up to 70% strength, depending on off-gas temperature. Compared to the conventional systems with typically < 95% efficiency, independent on the raw gas SO2 concentration, residual SO2 concentrations of less than 20 mg/Nm3 can be easily achieved, corresponding to nearly 100% removal. These features render the H2O, process a very attractive, low capital cost technology to retrofit existing conventional desulfurization plants.

Jan 1, 1996

John Keith Elers Douglas recently retired from active participation in the activities of the South African Institute of Mining and Metallurgy after over forty years of diligent and valuable service to the Institute. This account of his contributions to the mineral industry and associated organizations is presented as a tribute to all his hard work and dedication. Mineral processing The Fourteenth International Mineral Processing Congress, sponsored by the Canadian Institute of Mining and Metallurgy, is to be held in Toronto from 22nd to 27th October, 1982. The theme of the meeting is &apos;Worldwide industrial application of mineral technology&apos;.

Jan 1, 1981

Asarco&apos;s Sacaton unit, located near Casa Grande 45 miles southeast of Phoenix, Arizona, was brought into production in February 1974. Ore reserves are estimated at about 48 million tons at 0. 95% copper. Mineralization of the orebody comprises both sulfides and oxides, with minor amounts of gold and silver. Preproduction stripping of 40 million tons of overburden was accomplished in less than two years. Mining is done at the rate of 9,000 stpd ore with a waste-to-ore ratio of 4.6 to 1. 0. The mine is developed on 40 ft benches, and by 1979 underground block caving methods will be phased into the operation at a depth of 1900 ft. Ore is mined in the pit two shifts per day, seven days per week, and is hauled with 85 ton trucks to the primary crushing plant. Trucks dump their loads into a 165 st capacity pocket equipped with a chain curtain which controls the ore flow to the 6 ft 6 in. wide by 24 ft long (2. 0 m by 7.3 m) vibrating feeder grizzly. Grizzly bars are inclined at a 5º slope on the first half of the 0 feeder and 10 on the last half. Grizzly bars have 6 in. (13 mm) spacings which pass 60 to 70% of the mine-run ore. Grizzly oversize drops into a 48 in. by 60 in. (1. 22 m by 1.52 m) primary jaw crusher. Both the grizzly undersize and crusher discharge are collected on a 42 in. (1.07 m) conveyor belt operating 398 fpm (121 mpm) for transport to the 4,750 live st intermediate storage area ahead of the fine crushing plant. Capacity of the Sacaton primary crushing plant is a nominal 1150 stph (1043 mtph). It operates fourteen shifts per week with an effective crushing time of four hours per shift. An economical open-air design was used, but an enclosed operator control room is located on the upper level where the dump truck, feeder, and crusher can be observed. Oversize rocks are removed from the feeder or crusher by the 10-ton bridge crane. Direct operating costs for this well-designed primary crushing plant, including labor, power, supplies, and maintenance, are only 3.5 cents per short ton. An interesting feature of the Sacaton orebody is that the non-sulfide copper minerals, which are less prevalent than the sulfides, occur intimately with the sulfide minerals; for this reason, all ores as mined are treated in a flotation circuit using sulfidizing methods for oxide recovery.

Jan 1, 1978

By Young-Geun Park

A new decarburization model for the RH system was constructed for calculating the decarburization reaction using a three-dimensional fluid dynamics program. The entire fluid flow in the RH process was calculated by evaluating the shape and volume of the plume zone, formed by Ar gas blown through multiple nozzles on the wall of the snorkel. On the basis of this fluid flow, the decarburizaiton reaction was calculated through establishing the decarburization reaction model, which considers the thermodynamics, reaction kinetics, and the decarburization sites (Ar bubble surface, bath surface, and the CO bubble fomtation at inner sites). The results from this model were compared with a real RH operation results with good agreement. Because it is possible to predict the carbon concentration at various conditions using this model, it may be useful in increasing the decarburizaiton rate. Key words : RH process, plume zone, decarburization, Ar bubble surface, bath surface, inner site, circulation flow rate.

Jan 1, 2001

By Fred W. Shultz

In the past we have been somewhat harrassed by the terms "&apos;quality control" and "process control". This is especially true where the industry is dependent upon the chemical analysis of their product which in turn informs them how, well they have been controlling the process. The information which they have received, in most cases, is of an historical nature rather than of current value. The word "control" is to have more significance in future operations. This is particularly true in the metals industry. As the industry continues to process lower grade ores, and processing costs continue to rise, they must obtain more information faster to exercise "control" to its fullest extent.

Jan 1, 1963

Belting worth thousands of dollars can be ruined in a few minutes because of careless maintenance or lack of maintenance. Proper belt conveyor maintenance means having a clean conveyor system at all times. The belt line should be visually inspected during each shift. Equipped with proper maintenance instructions, one belt man can patrol a belt line of 2 to 3 km (1.5 to 2 miles). His duties would be to lubricate drives and idlers (except sealed-for- life type), maintain belt and conveyor frame alignment, detect sticking idlers, and maintain an unobstructed right-of-way.

Jan 3, 1978

By Tristan Worsey, Nathan Rouse

Florida legislature allocated funding for the Florida State Fire Marshal to review the applicability of the United States Bureau of Mines (USBM) Report of Investigations (RI) 8507 blast vibration limits with respect to Florida and its soils. The study also discusses whether the current blasting vibration limits set by statute are still appropriate, including a review of measured vibration amplitudes and frequencies, structure responses, and theoretical analyses of material strength and strains.

Jan 1, 2019

By M. J. McLeod, S. Watters, G. G. Lutes, S. Castonguay

"Gold-bearing mineralization at Anomaly A occurs in polydeformed Ordovician turbidites of the Kendall Mountain Formation of the St. Croix belt in southwestern New Brunswick, and is hosted by WSWtrending, shallow-dipping, brittle-ductile high-strain zones associated with the latest stage of the second of four regional deformation events. Gold-bearing syn-deformational stockwork, massive, and multiply brecciated quartz-sulfide veined zones form irregular pods and sheets up to several meters thick, which contain arsenopyrite, pyrrhotite, pyrite, stibnite, and a variety of rare minerals that are gold-bearing. Mineralized zones are enveloped by locally auriferous, weakly to intensely altered wall rock. Vein paragenesis includes: (1) early (pre- to syn-D2) quartz-chlorite veins that are largely the product of migration of quartz by pressure solution; (2) crosscutting, multiphase, vuggy quartz-sulfide veins that contain most of the gold and are interpreted to be structurally controlled; (3) late, crosscutting, nondeformed, non-gold-bearing veins containing laumontite, chlorite, muscovite, quartz, fluorite, and base metal sulfides. Carbonate-poor alteration associated with zones of gold mineralization is lithology-specific, and appears to reflect overprinting of multiple events. Major elements removed during alteration include Si, Na, Mn, and Mg. The minor and trace elements removed include Co, Li, Sc, and possibly Sr, Ni, and Zn. Minor and trace elements added include Au, Ag, As, Sb, S, and possibly F, Cu, Pb, and Zr. On the basis of proximity, time constraints, and a similar ore mineral assemblage, gold mineralization at Anomaly A is interpreted to be a distal equivalent of the intrusion-related gold mineralization at the nearby Clarence Stream Main zone deposit. La minéralisation aurifère de l’Anomalie A se trouve dans des turbidites Ordoviciennes polydéformées de la Formation de Kendall Mountain, dans la ceinture de Ste-Croix du sud-ouest du Nouveau Brunswick, où elle est contenue dans des zones de déformation fragile-ductile à faible pendage de direction OSO associées au dernier stade du second de quatre épisodes de déformation régionale. Les zones aurifères syn-déformationelles se présentent en forme massive, de stockwork, ou de veines de quartz-sulfure bréchifiées à répétition formant des lentilles irrégulières et des couches de plusieurs mètres d’épaisseur contenant de l’arsénopyrite, de la pyrrhotite, de la pyrite, de la stibine, ainsi que divers minéraux aurifères rares. Les zones minéralisées sont entourées d’une enveloppe de roches faiblement à intensément altérées, localement aurifères. La paragénèse des veines comprend : (1) des veines précoces de quartz-chlorite (pré- à syn-D2) qui sont principalement le produit de la migration du quartz par solution-pression; (2) des veines polyphasées de quartz drusique et de sulfures contenant la plus grande partie de l’or, celles-ci sont considérées comme étant sujettes à un contrôle structural; (3) des veines tardives stériles, sécantes et non déformées contenant de la laumontite, de la chlorite, de la muscovite, du quartz, de la fluorite et des sulfures de métaux usuels. Les zones de minéralisation aurifère sont associées à une faible altération en carbonate contrôlée par la lithologie et semble résulter de la superposition d’événements multiples. Les éléments majeurs perdus durant l’altération sont le Si, le Na, le Mn et le Mg. Les éléments mineurs et traces perdus durant l’altération sont le Co, le Li, le Sc et possiblement le Sr, le Ni et le Zn. Les éléments mineurs et traces enrichis comprennent l’Au, l’Ag, l’As, le Sb, le S et possiblement le F, le Cu, le Pb et le Zr. Étant donné sa proximité géographique, les contraintes temporelles et les similitudes de leurs assemblages minéraux, la minéralisation aurifère de l’Anomalie A est interprétée comme un équivalent distal de la minéralisation aurifère associée aux intrusions du gisement avoisinant de la zone principale (Main"

Jan 1, 2008

By James M. King

Analytical models for transient groundwater phenomena, such as those of Theis, Cooper, and Jacob, are important but often limited tools for aquifer evaluation and drawdown prediction. Most were developed using simplifying assumptions which compromise their treatment of complex boundaries and most also contain functions that are mathematically complex and difficult to solve explicitly. Examples of such functions are the Bessel functions, the exponential integral, and similar well functions for leaky confined and water table aquifers. This paper describes the joint use of simple numerical techniques and numerical approximations of these functions to extend many analytical models beyond their conventional applications. The enhanced analytical methods represent many hydrologic problems more easily and realistically, permit a wider range of application, and often provide insight into the response of pumped groundwater systems without the need to resort to more complex numerical flow models. Use of the enhanced analytical methods usually requires the use of microcomputers due to the large number of computations. Examples presented here are the development and extension of type curves and the determination of drawdown distributions.

Jan 1, 1984

By E. F. Schnitzer, D. R. Haight, G. T. Krogman

The 1997 New Year’s Day Rogue River flood near Medford, Oregon, USA, entered historic channels, eroded a 150-foot-wide buffer, and captured an inactive gravel pond located within the channel migration zone. Channel redirection caused by pit captures threatened adjacent inactive gravel ponds. In response to this capture, a stakeholders group of concerned individuals and organizations was formed. This group ultimately developed a rehabilitation plan, which conformed to the Rogue River’s geomorphic trends. A two-dimensional model, FLO-2D, was used to evaluate channel splits, flood storage, backwater, and future conditions. Modeling results coupled with trend analysis were used to create a stable design where stream barbs, gravel redistribution, a channel outfall spillway, bendway weirs, bank reshaping, and revegetation were integrated into a single plan for a three-mile reach. The quick action by the stakeholders group averted further damage to the Rogue River system and surrounding environment. The project has preserved three miles of mainstem habitat, one mile of side channel habitat, and protected ten gravel ponds from pit capture.

Jan 1, 2006

The Perth Mint receives gold and silver from various sources for evaluation and refining. The metals are received in many forms and vary widely in assay. Refining is carried out using the Miller Process and the and the resulting market quality bullion is sold in a range of weights and alloys to suit the international bullion market and public demand. INTRODUCTION The Perth Mint was established in the late nineties as a branch of the Royal Mint, London, to refine the gold from the newly established gold- fields in Western Australia. The branch was opened for business in June, 1899. After refining, the bulk of the gold was used in the manufacture of sovereigns and half-sovereigns. Nowadays, although most of the gold received comes from the W.A. goldfields, some gold is deposited by producers in other states and in Papua-New Guinea, as well as scrap and trade wastes from manufacturing jewellers and old jewellery from the general public. Silver is deposited in the form of old silverware, recoveries from-photographic processes etc. Gold or silver may be lodged at the Mint in person, through a bank or other agency or by registered post. Telegraphic advice is usually given when gold is sent by the latter, so that insurance may be effected.

Jan 1, 1982

By Akram Marseet, Andrew J. Petruska, Rik Banerjee

Underground mine roof bolting is a crucial operation for miners’ safety and mine sustainability. Since roof bolting is a manual or human-supervised operation, miners’ safety is at risk due to dust or rock falls. Traditional machine learning algorithms have shown limitations to detecting drillable areas, mainly due to harsh lighting conditions. The authors propose an adaptive deep-learning framework for autonomous roof bolting. The proposed framework is based on implementing a binary semantic segmentation algorithm on color images to classify pixels that belong to rock from those that belong to non-rock. Significantly, the proposed framework implements deep learning semantic segmentation on images from traditional and neuromorphic vision sensors in underground mines. The performance of the proposed model shows an impressive accuracy level of at least 98% at a low number of training epochs with smooth learning curves. The high accuracy enables the implementation of autonomous roof bolting, greatly improving miners’ safety and operational efficiency while reducing human exposure to safety hazards. This research will advance the use of deep learning in mining automation and has the potential to revolutionize the traditional mining industry.

Feb 1, 2024