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By Douglas A. Anderson

The US Bureau of Mines, in RI 8507, has shown that blast vibrations at low frequency are more likely to cause damage and complaints than those at higher frequency. Since that publication in 1980, the Office of Surface Mining and many state and local regulatory authorities have incorporated frequency in their regulations for acceptable ground vibration from blasting. Even when frequency is not explicitly stated in regulations, it may become an issue in hearings or in court.

Jan 1, 1992

By J. Cayouette

In 1995, Louvicourt mine started one of the first paste backfill operations in Canada. From 500 000 t in 1995, the annual paste backfill tonnage produced reached 800 000 t in 1999. The maximum throughput of the surface plant (including binders) is 3500 tpd with a final density of 75% to 76% solids which gives a slump of 15 cm to 17 cm. Following the start-up of the paste backfill plant, the backfill strength performance levels were well below the pilot plant’s predictions. The introduction of ferrous slag, laboratory tests on various binder ratios with or without additives, and the desliming of the tailings enabled us to optimize the mix and operation costs. Primary and secondary stopes are filled respectively with a paste containing 4.5% and 2% binders in a mixture of 20% cement to 80% ferrous slag. In certain stopes, the binder ratio may vary from 2% to 7%, but always in a ratio of 80/20. Six years after start-up, or 4.5 Mt of paste backfill later, this paper discusses the present operation and the major changes that have occurred over the years to optimize both the operation and the paste fill quality.

Jan 1, 2003

By W. A. Backofen, D. L. Holt

Push-pull fatigue tests have been carried out at 4.2°K, 77oK, and room temperature on two poly crystalline materials of widely different stacking-fault energy (?): pure copper (? - 70 ergs per sq cm) and the Cu-8 wt pct A1 alloy (? - 2.8 ergs per sq cm). Constant stress-amplilude was imposed and measurement was made of the plastic-strain amplitude (ep) at saturation. Lives extended from 104 to 106 cycles. Designating lives at the various temperatures by NRT, N77, and N4.2. the ratios N77/NNT and N4.2/N77 ranged from 3.5 to 18 under the condition of common Ep . Metallo-graphic examination revealed different crack morphology in Cu-8 Al fatigued at room temperature, and at 77" and 4.2oK. At room temperature, cracks lay in or near grain and lain boundavies; at 77o and 4.2oK. cvacks were transcrystalline. Tests on single crystals of Cu-8 A1 showed that such a change in the cracking mode in polycrystallitle material accounted for a factor of- about 3.25 in N77/NRT . The longer life at lower tewperatztre (conslant cp) has heels attributed to two deuelopinents: a reduced production of the dislocation tangles and subgrain boundaries which serve as paths of rapid cracking, and suppression of oxygen chetni-sorption at the crack tip It was concluded that in both materials the luller accounted for an extension of the life at 4.2oK beyond that at room temperature by a factor of 15. XV ECENT experiments on the fatigue of Cu-A1 alloys in the so-called high-cycle range (greater than lo4 cycles) have emphasized the importance of stacking-fault energy (y) as a quantity affecting crack propagation rate and fatigue life.1,2 It was found in comparisons at essentially fixed plastic-strain amplitude that crack growth rate decreased by a factor of about 5 over the composition range from copper (? - 70 ergs per sq cm) to Cu-8 wt pct Al (? - 2.8 ergs per sq cm). The argument was made that, when stacking-fault energy is high, cross slip and climb are favored, so that dislocation tangles and/or subgrain boundaries form more readily under cyclic loading. Since the boundaries and tangles act as paths of rapid crack propagation ,3, 4 life is shortened as a result. However, when stacking-fault energy is reduced (as by alloying), cross slip and climb become more difficult, with the result that substructure formation is retarded and growth rate is also reduced. A purpose of the present work was to investigate the substructure effect in relation to temperature. As temperature is lowered, ? is varied only slightly (if at all), but decreased thermal activation can interfere with cross slip and climb. Thus substructure formation could be curtailed and life increased. Fatigue life in the high-cycle range is also known to be strongly influenced by environment. Working with copper, Wadsworth and Hutchings observed that life in a vacuum of 10-8 mm Hg exceeded life in air by a factor of 20.5 They isolated oxygen as the agent that furthered cracking. While the details are still unclear, a requirement in any mechanism of oxygen-accelerated cracking is that there be chemisorption at the crack tip. That could prevent welding on the compression half cycle,= interfere with reversal of slip,1, 6 or aid in breaking metal-metal bonds at the crack tip.5'7 In the work being reported here, temperature was lowered by immersion in liquid nitrogen and helium, which also served to reduce both the oxygen concentration and chemisorption rate. A possible effect upon life, i.e., a lengthening, had to be recognized. Several researchers have determined fatigue lives at low temperatures presenting their results in the form of stress amplitude (S) vs cycles in life (N) curves.8-11 Such curves reflect, primarily, the fact that metal is strengthened by lowering temperature; effects of substructure and changing environment tend to be masked. The difficulty can be overcome by comparisons based on identical plastic-strain amplitudes, and in the present work the dependence of life on both plastic strain and stress amplitude was established. EXPERIMENTAL Materials. The principal materials were polycrystal-line copper (? - 70 ergs per sq cm)" and the Cu-8 wt pct Al alloy (? - 2.8 ergs per sq cm),I3 the latter being near the limit of solubility of aluminum in copper and having, therefore, the lowest stacking-fault energy in the CU-Al system. Specimens were machined from 0.118-in.-diam cold-swaged rods of high-purity (99.999 pct) copper and the Cu-8 Al alloy, the latter produced initially in a graphite boat by induction vacuum melting a mixture of 99.999 pct Cu and 99.99 pct Al. The machined specimens were annealed to produce mean grain diameters of about 0.070 mm in copper and 0.190 mm in the alloy. Specimen dimensions are given in Fig. 1. Values of the tensile yield stress, ultimate strength, uniform strain (determined by the Considgre construction), and reduction of area, for both materials at 4.2oK, 77oK, and room temperature, are listed in Table I. The tensile apparatus in which these results were obtained has already been described.14 Apparatus. Specimens were fatigued in push-pull with a machine that is illustrated schematically in Fig. 2. The specimen is first soldered into the top grip (1) with Woods metal, and the grip is then screwed into the inner tube (2) which is connected to the drive rod of the Goodmans vibration genera-

Jan 1, 1968

By F. Parada Luna, F. Parada Torres, J. Salvo, A. Reghezza

In the pyrometallurgical processes of copper concentrates, arsenic is preferentially concentrated in the dusts carried by the gases as a result of their volatility and subsequent condensation in the gas cleaning train. In this work results obtained by alkaline leaching of the dusts from Ministro Hales roasting plant, belonging to Codelco, are presented. For the Ministro Hales plant the alkaline leaching would be an alternative to the recirculation of dusts to the roasting furnace. The experimental study considered NaOH and NaOH plus NaHS leaching of two samples of dusts, with 4.24 and 2.55% arsenic respectively. The results show that it is feasible to extract 90% of the arsenic and 50% of the antimony at room temperature using only NaOH, and when the temperature increases to 95ºC, the extractions of As and Sb increase. Copper remains in the solid residue with less than 1% dissolution, and the NaOH net consumption was approximately 140 kg/t of dust. In leaching tests with NaOH + NaHS, two types of methods were tested, baking plus leaching with water and direct leaching with a NaOH+NaHS solution. With the second method arsenic extraction increased to 95% and copper dissolution was less than 0.01% at 85ºC, NaOH 100 g/L, NaHS 90 g/L, 1.5 h and L/S ratio of 5/1 (L/kg). The bismuth remains stable in the solid in all cases. INTRODUCTION The presence of arsenic in copper concentrates has increased with time and the environmental regulations are becoming increasingly more stringent. In concentrate treatment pyrometallurgical plants, most of the arsenic is volatilized condensing in the gas train and is collected along with the entrained solids to form the flue dusts. Under these conditions, in smelters of copper concentrates with high arsenic content, the dusts are being treated in hydrometallurgical plants to extract and stabilize the arsenic, which also means that most of the copper contained in the dust is co-extracted with the arsenic. This affects the recovery of copper in the smelter and an alternative such as the selective alkaline leaching of arsenic, would allow the copper from flue dust to be recovered.

Jan 1, 2019

By Shosei Serata

Salt cavities have been proven to be a suitable structure for underground storage of various matters in gas, liquid or solid form. Since the technique of underground storage was developed mainly through field experiences in solution mining, a wider use of solution cavities for storage of gaseous and solid matters requires evaluation of three basic rock mechanics problems; cavity instability, boundary rock failure and surface subsidence. Cavity instability is due to the non-linear long-term creep properties of the surrounding ground media which are sensitive to cavity pressure changes associated with the storage. The cavity boundary rock failure is caused by the loss of effective confining pressure to the boundary rock media in the process of storage of gaseous and solid matters. Surface subsidence is the final outcome of the stress envelope originated around a cavity, eventually reaching the ground surface. The rock mechanics processes of instability, failure and surface subsidence are explained by using various field examples in salt domes and bedded formations. Methods of solving the problems are discussed including stress relief, stress control and computer optimization of design.

Jan 1, 1973

By L. M. Cumming

"The contact between dolomite of the St. George formation (Cambro-Ordovician) and limestone of the overlying Table Head formation (Middle Ordovician) is a regional disconformity. This is best illustrated from exposures on Pointe Riche Peninsula, near Table Point, and along Port au Port Bay. The contact occurs along 180 miles of the west coast of Newfoundland from St. John Island in the north to the western part of Port au Port Peninsula in the south. A disconformity of the same age occurs between the Romaine and Mingan formations on the north side of the Gulf of St. Lawrence.Dolomitic beds beneath the disconformity locally contain concentrations of base-metal sulphides. Sphalerite occurs in dolomite pseudobreccias of the St. George formation at Zinc Lake, 7 miles northeast of Daniels Harbour. The 'Western Newfoundland Lower-Middle Ordovician regional disconformity is interpreted as having originated on and near the edge of a broad platform, and to have provided an important regional geological control in the localization of zinc mineralization."

Jan 1, 1968

By P. Sangurmath, C. Gundewar, M. Riyazulla, V. Vasudev, N. Shadaksharswami

Dharwar craton in the southern Indian shield, comprises the Neoarchaean foreland in the west and a relatively younger accretionary complex composed of granitoids and intervening gold-bearing volcano-sedimentary belts. The Hutti schist belt hosting a major gold producing mine is situated in the northern part of the eastern Dharwar craton. It is a horse-shoe shaped structure comprising predominantly of pillowed metabasalt of tholeiitic composition with minor amounts of clastic sediments and felsic volcanic rocks. The belt is intruded on all sides by circular to tabular bodies of granites and granodiorite. Important gold deposits are located at Hutti, Hira-Buddini and Uti villages. Felsic volcanics in the Hutti belt occur as tabular bodies of quartz porphyry and breccia. Two of the gold-bearing reefs in the Hutti mine, Viz., Middle and Strike reefs are intimately associated with tabular sub-vertical sheets of mylonitic quartz-feldspar porphyry intruding pillowed metrabasalt. In Uti mine area, the felsic volcanics occurs as a tabular body. At Hira-Buddini, the felsic volcanic occur as a irregularly shaped sheet in pillowed metabasalt. Mineralogical and geochemical studies suggest that the felsic volcanic rock in Hutti mine area is a rhyolite and at Uti and Hira-Buddhini it is of dacite composition. Scheelite occurs as veins, veinlets, stringers and blebs along fracture planes of felsic volcanics in the Hutti mine area, whereas at Uti and Hira-Buddini it is insignificant. On the basis of spatial association of metabasalt and felsic volcanics and on geochemical grounds, we interpret that the felsic volcanics might have originated by the partial melting of basalt. REE patterns of the granite, granodiorite and metabasalt of Hutti are similar to each other indicating that they could be co-magmatic. However, REE in the Hutti felsic rocks is significantly higher than in Uti and particularly Hira-Buddini mine areas. The two felsic volcanic samples drawn away from the mineralized zone from all the three mine areas were analyzed for tungsten. In Hutti one sample assayed 0.15% and another 0.062%. At Uti, in one sample it assayed 0.056% and another less than 1 ppm, whereas at Hira-Buddini, it is less than 1 ppm in both the samples. The spatially associated basalt analyzed 23 to 235 ppm tungsten, whereas granites and granodiorites have very low (<1 ppm) tungsten. Therefore, the source of tungsten in the felsic volcanics of Hutti area could be traced to metabasalt. The absence of significant amount of tungsten in the felsic volcanic of Hira-Buddini could be attributed to the lack of REE enrichment compared to REE in Hutti and Uti felsic volcanics.

Jan 1, 2007

By Beatriz Lemos Clemente

A maneira com que acontece a nucleação interfere diretamente na forma dos contornos de grão e também nas propriedades do material em questão. Para visualizar melhor, pode-se utilizar uma célula cúbica, na qual é possível notar que em cada eixo há diferença de textura e densidade entre os grãos já desenvolvidos. Neste trabalho, foram empregadas duas vias de estudo a fim de obter os resultados desejados. A primeira delas é a nucleação homogênea dos grãos e a outra, a nucleação não homogênea, ambas com velocidade constante. Esse fenômeno pode ser visto durante a recristalização de grãos. Rios e Villa [6] criaram um método efetivo para analisar a cinética das transformações homogêneas e não homogêneas a partir do método de JMAK[1-5]. Para comparar método analítico foi desenvolvida uma simulação computacional com base no modelo analítico Rios e Villa [6], foi utilizado a metodologia do Cone Causal (método estocástico). Os gráficos gerados confirmam a teoria de Rios e Villa [6] para esses casos particulares e comparam os resultados obtidos com o conceito de JMAK [1-5].

Oct 30, 2017

By Raymond Chenier

British Columbia (BC) is Canada’s most western province. The landscape in BC is amongst the most beautiful and pristine in the world. Along with its beauty come vast mountain ranges, coastal rain forests, swamplands, deep river valleys, and almost every type of landscape imaginable. These all have, or at one time had, logging roads constructed. Some of these areas should never have had roads constructed due to poor drainage and unstable slopes, but some of the roads could be considered engineering masterpieces. To navigate a vehicle the size of an off-road logging truck down the side of a mountain with an 80°h side slope or greater can be a hair-raising experience. Not to mention coastal rains and/or high elevation blizzards. These factors collectively make logging BC’s most hazardous occupation. People are seriously hurt, sometimes even killed everyday.

Jan 1, 2001

By H. Ding

Calcium carbonate/Titanium dioxide composite, characterized by coating TiO2 on the surface of CaCO3 particles, is an important substitute for titanium dioxide. This paper studies preparation method of CaCO3/TiO2 ,composites based on mechano-chemical effects, measures its properties as a pigment, analyzes the binding form and interface reaction mechanism between CaCO3 and TiO2. Through single finely grinding of CaCO3, co-grinding of CaCO3 together with TiO2, and mecha-no-chemical effects produced in the course of grinding, CaCO3/TiO2 composites can be prepared successfully. Results indicate that grinding fineness of CaCO3, co-grinding time of CaCO3 and TiO2, the weight ratio of grinding media to mineral feeding, and the amount of TiO2 have much influence on the properties of CaCO3/TiO2 composites. CaCO3/TiO2 composites have the properties same as titanium dioxide pigment, oil adsorption and ultraviolet adsorption same as TiO2, and 90% of hiding power as that of TiO2. Wet grinding of CaCO3 causes the production of mechano-chemical effect and hydroxyl group, through which CaCO3 and TiO2 can be bonded together. Repulsion occurs between the particles of CaCO3 and the particles of TiO2, respectively, they are both in good dispersion. But attraction occurs between CaCO3 and TiO2. TiO2 particles are distributed evenly on the surface of CaCO3. Therefore, coating of TiO2 on the surface of CaCO3 particles and chemical bond between them make CaCO3/TiO2 compo-sites have pigment properties of Titanium.

Jan 1, 2014

Mining is a high risk industry where miners seek to secure certainty in all of their dealings. The introduction of native title to the Australian legal system with the High CourtÆs 1992 Mabo decision and subsequent Native Title Act 1993 has added to the risks associated with implementation and the ongoing operation of exploration and mining projects. The High CourtÆs Ward case in August 2002 confirmed Crown ownership of minerals and petroleum. But the Court also found that a mining lease that allowed an exclusive possession for mining purposes did not extinguish all native title rights and interests. Although the Court was specifically considering WA mining tenements, the WA mining lease is very similar to the mining leases and licences that exist across Australia, meaning that these tenements are unlikely to fully extinguish native title. The Ward case means that native title remains squarely on the table now and into the future for those involved in developing exploration and mining projects. However, certainty and workability is capable of being secured and this paper discusses some means by which this may be achieved. The paper starts by considering two of the many 1998 amendments to the æfuture actsÆ regime under the Native Title Act, Indigenous Land Use Agreements (ILUAs) and the application of ægood faithÆ negotiation to all negotiating parties. It then looks at native title agreements, other issues affecting negotiations and tips for negotiation technique.

Jan 1, 2003

By Ravindra M. Chhatre

Uranium associated with phosphate deposits has been the subject of numerous investigations (1-8). In the land-pebble phosphate deposits of central Florida, uranium is found in the phosphate matrix (ore) and in the leached zone between the over-burden and matrix (1). Between 0.01 to 0.02 percent uranium is found in the leached zone, which consists of apatite and aluminum phosphate minerals (crandallite, wavellite, millisite) (Z). The primary phosphate mineral in the matrix is apatite, and the 0.005 to 0.01 percent uranium typically found in the matrix is associated with this mineral (1). It is generally believed that uranium substitutes for calcium in the apatite structure (3-5). Clay and quartz phases associated with phosphate deposits contain little uranium (1, 6), and no descrete uranium minerals have been detected in these deposits (4). A typical phosphate matrix consists of quartz, slimes (-150 mesh material) and recoverable phosphate. When the matrix is beneficiated, partition of uranium and radium takes place (9, 10). Although considerable data exists on how uranium is distributed in the phosphate deposits, no systematic study has recently been reported on the distribution of uranium during phosphate rock beneficiation. The purpose of this study was to determine how uranium is distributed in the various strata which comprise the overall land-pebble phosphate deposits, as well as how the uranium is redistributed during beneficiation of phosphate matrix. To obtain this information studies were carried out on matrix samples obtained from three different mines in central Florida. Using pilot-plant scale beneficiation, an analysis was performed on how uranium in the matrix is distributed among the pebble fractions, flotation concentrates, flotation tails, and slimes. The uranium level profile for an active mining area was also obtained. Also, since thousands of acres of slime ponds may someday become a source of both phosphate and uranium, a depth versus uranium content profile was determined for an inactive slime pond.

Jan 1, 1978

By Earl A. Trager

The broad picture of world petroleum production at the present time is one of an excessive supply. In any consideration of corrective measures to be applied in the future, it will be necessary to include all the producing areas of the entire world. To illustrate, United States production during 1931 was 48 million barrels1 less than 1930, whereas world production exclusive of the United States increased, owing principally to increases in Russia, Rumania and Persia. Domestic Peoduction Let us first consider the domestic production situation. Due to the fact that United States production was maintained below current demand, about 40 million barrels of oil were withdrawn from storage during 1931. Consumption increased about 1.5 per cent over 1930, which is less than the recent annual rate of increase of 8 to 11 per cent. If the machinery to prevent waste in the petroleum industry operative for more than a year will continue during the coming year and drilling is held to the 1931 level, there will be a decided improvement in the domestic situation by the close of 1932. This will be due in large measure to the drastic reduction in exploratory work and drilling which has been in effect for more than a year. Looking ahead for two or more years, probably there will be a shortage of domestic production in relation to domestic demand, unless there are discovered several large pools comparable to Oklahoma City or East Texas. Were the United States isolated, our problems in so far as petroleum production is concerned might be considered well along the road to recovery. To maintain this perspective will require the cooperation of foreign producers in the future, or protection of United Statcs markets from foreign invasion. Let us review briefly the present situation in the United States. East Texas has been the most important factor during 1931. The large initial production of individual wells and the rapid rate of drilling

Jan 1, 1932

By L. F. Mondolfo

R301 is a clad aluminum alloy, composed of a core of a duralumin-type alloy clad with a magnesium silicide alloy. It differs from other well-known clad alloys in that the cladding and the core respond to the same heat-treatments, and therefore the cladding contributes appreciably to the mechanical properties of the material. In Table 1 are reported the compositions of the core and cladding alloy for the material used for the experiments. [ ] In clad aluminum alloys where the core contains copper and the cladding does not, at elevated temperatures the copper tends to diffuse from the core through the cladding. This fact is well known and many investigations have been conducted to determine the features of this diffusion.1-7 Most of those investigations cover materials clad with pure aluminum; the present investigation covers a material clad with an alloy. Since the cladding thickness on R301 varies with the gauge, as shown in Table 2, several gauges were investigated. [ ] MATERIAL AND PROCEDURE The material used was sheet of the following gauges: 0.025, 0.040, 0.064, 0.102, 0.170. Cut in pieces approximately 3 by 5 in., it was in the cold-rolled state and was soaked for increasing times at the following temperatures: 910°F., 940°F., 970°F. A Lindberg cyclone furnace was used for the experiments. The procedure was as follows: The furnace was started empty with controlling pyrometer set at the determined temperature. After the furnace had reached that temperature, it was run for some 20 to 30 min. empty, in order to allow the temperature inside to become stabilized. Then the first samples were introduced. A load thermocouple, with recording pyrometer, was connected with the sample of the heaviest gauge. About 10 min. was required for the material to reach temperature and the soaking time was counted from that point. After 200 min. soaking, the second group of samples was introduced without stopping the furnace. After 200 min. more, the third group of samples was introduced, and so on, until the last sample had been introduced. Every time the furnace was opened and new samples were added, a drop of temperature was registered by the thermocouple connected with the material

Jan 1, 1945

By R. W. Waterfill

MANY existing ore deposits of valuable metals have been worked out in their upper surface levels and the continued productivity of these mines is dependent on their extension to greater depths in the earth. The maximum depths at present reached are about 6000 to 8000 ft. below the surface, with no evidence of an impoverished ore vein. These mines are widely distributed; some of the best known are in South Africa, Brazil, India and in the western sections of the United States. Among the factors which increase the difficulty of working these mines at increasing depths are hoisting, rock pressure and temperature. The manner and effectiveness with which these problems are met will, no doubt, determine in a large measure the ultimate depths to which any mine can be profitably worked. The most critical of these three factors at present is the increase in temperature with depth. The high temperature and humidity in many of these mines at present is severely detrimental to the health of the workers and greatly hampers their efficiency. Some have almost reached a condition in which the human system cannot survive. The problems involved in the cooling and ventilation of mines have all been ably analyzed and presented in previous articles. For this reason, only a resume of conditions affecting the cooling and conditioning of deep and hot mines will be given in this paper before attention is directed to possible methods of improving atmospheric conditions in the working levels.

Jan 1, 1929

By J. T. Jordaan

Paper written on project work carried out in partial fulfilment of B. Eng (Mining Engineering) degree This paper addresses the critical parameters that need to be considered when designing a mechanized bord-and-pillar mining layout for a narrow tabular steep dipping orebody. These parameters are : ?Reef dip ?Reef width ?Geological structures within the orebody ?Physical dimensions of the selection of machines ?Gradeability of the selection of machines. The main objective in designing such a layout is to maximize machine efficiencies whilst minimizing dilution. This methodology was then applied in the design of a mechanized bord-and-pillar mining layout for a given piece of ground (Vlakpoort and Moddergat) using a given selection of machines. This piece of ground contains the PGM bearing UG2 Reef with an average thickness of 124 cm and dipping at 18°withadverse strike and dip changes. Two bord-and-pillar layouts were designed for this area. Layout 1 is characterized by the use of strike conveyors to convey ore on strike with an average LHD hauling distance of 35 m. Layout2 uses LHDs for all on strike conveyance of ore with an average hauling distance of 75 m. These two layouts were then technically and financially compared. It was concluded that layout 1 is theoretically superior but layout 2 was chosen due to its greater flexibility and probability of operational success. Layout 2 was also compared to conventional mining and it was concluded to be more economically feasible. However the latter is a proven mining method in these conditions and has a lower risk operational failure. Bord-and-pillar mining has some favourable promises such as improving labour difficulties, lowering operating costs and providing safer working conditions. The success of mechanized bord-and-pillar mining in narrow tabular steep dipping orebodies will depend on the extent of the research and development efforts which need to create and innovate technologies to overcome some of the current limitations stated in the above-mentioned parameters.

Jan 1, 2003

By D. Warkentin, M. Tomlinson, A. Nacu

"This study focuses on comparing the “blinding” effectiveness of various organic additives as part of a general review of using organic additives to mitigate preg-robbing and improve gold recovery during cyanide leaching of carbonaceous gold ores. The laboratory results compared the impact of various organic additives on the prevention of gold adsorption using both activated carbon and ore samples containing carbonaceous matter, generally referred to as total carbonaceous matter (TCM). Although several organic reagents were found to have a significant blinding effect on activated carbon, these results did not translate into increased gold leaching efficiencies with actual ore samples.INTRODUCTION Preg-robbing refractory ores, which contain carbonaceous matter, have been problematic in cyanide plants for many years. In industry, preg-robbing by carbonaceous matter may be mitigated using various techniques including flotation, to remove the carbonaceous matter; addition of blinding agents, to passivate the carbon surface and prevent adsorption of gold cyanide complex; roasting, to partially or fully destroy the carbonaceous matter; chemical oxidation (Abotsi & Osseo-Asare, 1986); pressure oxidation; or microbial deactivation (Dunne, Staunton, & Afewu, 2013). Carbon-in-Leach and Resin-in-Leach are also used as process alternatives in which activated carbon or resins are used to compete with the carbonaceous matter for gold cyanide adsorption. For highly preg-robbing ores, thiosulphate leaching may be considered as an alternative to conventional cyanide chemistry (Baláz, et al., 2000). Natural carbonaceous matter is composed mainly of hydrocarbons, organic acids, and graphitic/amorphous elemental carbon. Natural elemental carbon that behaves as activated carbon is considered to be the main reason for preg-robbing, although the true nature of this phenomenon is not fully understood (Tan, Feng, Lukey, & van Deventer, 2005). In general, the hydrocarbon fraction is assumed to have negligible interaction with gold, while organic acids, such as humic acids, may form complexes with gold, inhibiting its extraction in cyanide solutions. Organic reagents have been used for blinding carbonaceous matter in gold ores prior to cyanidation. Abotsi & Osseo-Asare (1987) tested various organic compounds, with two possible effects in mind. First, the organic compounds were expected to adsorb onto the surface of the solids as anionic/cationic species; the resulting electrostatic interactions between the Au(CN)2- anion and the negatively/positively charged surface would inhibit/enhance the gold uptake. Second, the organic reagents were expected to coat the surface of the carbonaceous component in the ore, limiting the available adsorption sites and reducing gold losses. Optimal reagent dosage depends on ore mineralogy, maturity and surface area of the carbo"

Jan 1, 2019

By Erik Westman, BEN WESTON, SETAREH GHAYCHI AFROUZ, KATHRYN DEHN

This study investigates the changes in seismic velocity of rockmass before and after three major seismic events to determine any potential identifiable precursory velocity changes associated with these events. Induced stress measurement is one of the challenging tasks in deep underground mining, with extreme impacts on the safety and stability of the mine. This study used p-wave passive seismic tomography to image the velocity redistribution within a rockmass, which can indicate induced stress level changes in the rockmass and detect the velocity changes that might precede a major seismic event or a rockburst. The ultimate goal of this research focus is to develop another tool for the deep-mining community that will help to increase safety and efficiency. For this purpose, the hypothesis of conventional mechanics, which implies induced stress at the hypocenter (as inferred by the p-wave velocity) increases until the seismic event occurs, is evaluated. It is found that the p-wave velocity did not increase at any of the three hypocenters prior to the seismic event occurring; however, the p-wave velocity did increase in the closest “zone center” for two of the three events. 

By M Dusci, A Trueman, S Poos, R Baumgartner, M Brittan

The Canahuire epithermal Au-Cu-Ag deposit in southern Peru is a complex and challenging deposit for metallurgical studies. It has issues of gold locking in sulfides and non-sulfides, deleterious elements and acid rock drainage (ARD). From scoping study to feasibility study, there has been considerable improvement in the understanding of the important geometallurgical characteristics that need to be measured and modelled. This paper presents the current understanding and the requirements to continue to provide optimal models for mining studies.Significant effort has been put into understanding the genesis of the deposit. Improved spatial and temporal understanding of lithology, alteration, structure and mineralogy was used to build a geological and alteration model of the deposit.Early metallurgical programs quantified the effect of head grade on process plant recoveries, but the geometallurgical and statistical analyses did not identify other physical characteristics that influence these recoveries. The studies improved the understanding of the nature of locked gold which can occur as minute inclusions (&lt; 5 ¦m) in sulfides (primarily pyrite with lesser arsenopyrite, pyrite being 100 times more abundant than arsenopyrite) and gangue minerals (quartz and carbonates) as well as solid solution in arsenopyrite and pyrite.The presence of pyrite and the limited buffering capacity of waste rocks increases the potential ARD, which will require mitigation costs before, during and after operations. Waste rock ARD potential has been classified and incorporated in the geometallurgical model. The current classification of waste rock at Canahuire, using international classification standards, is limited due to the complexity of the deposit.Complex deposit metallurgy necessitates a complex process flow sheet, including flotation and cyanidation. Economic recovery will be constrained by the relationships between economic variable grade, other elements and mineralogy. These constraints and inter-relationships are difficult to establish throughout the deposit with a single test. A follow-up geometallurgical program is under investigation and will attempt, with the help of additional test work, to map areas of higher and lower recoveries. It is hoped that metallurgical response can be linked to measurable parameters other than head grade. If this is possible, these factors can be incorporated into future geometallurgical models.CITATION:Baumgartner, R, Dusci, M, Trueman, A, Brittan, M and Poos, S, 2013. Building a geometallurgical model for the Canahuire Epithermal Au-Cu-Ag Deposit, Southern Peru - past, present and future, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013 , pp 51-58 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 29, 2013

By Mutmansky J. M, Organiscak J, Qin J, Bhaskar R

The results of a two-year research study into the relationship between quartz dust levels in host material and in respirable dust in continuous mining sections are presented in this paper. The experimental design and sampling procedures for underground data collection are outlined. The sample analysis procedures for quartz determination, the analysis results and conclusions of the study are discussed.

Jan 1, 1988