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By M. Gallego, R. Oyarzun, L. Ortega

Evidence of metallogenic activity in an area dominated by Upper Precambrian and Palaeozoic metasediments was partially explained in the 1980s when drilling and a geophysical survey detected hidden intrusions, but questions remained to be answered about the nature of the fluids. Sb mineralisation at El Juncalon vein-type deposit was selected for geological, geochemical and fluid inclusion studies as a model with a relatively simple quartz-stibnite-pyrite paragenesis. Many of the characteristics were those of Chinese-type vein Sb deposits, which can be regarded as atypical of the epithermal type as they are hosted by clastic rocks

Aug 1, 1995

By V. A. Melezhik, A. H. Green, L. N. Grinenko

Finally, a theoretical model is constructed that takes

Aug 1, 1994

By R. Venugopal, T. C. Rao, N. Suresh

Experiments were carried out using the cyclone to treat coal in the size range -2.0+0 mm. The diameters of the cyclone outlets (vortex finder and spigot) were varied to study their effects on cyclone performance. The cyclone products were deslimed over a screen with an aperture of 0.075 mm. The performance of the separator was studied for washing coarse coal (-2.0+0.075 mm) and fines (-0.075 mm). Performance curves were plotted for the separation of -2.0+0.075 mm coal. The concept of a generalised distribution curve was adopted to predict cyclone performance. A mathematical representation was derived from the generalised distribution curve. The specific gravity of separation for individual size fractions showed a decreasing trend with decreasing particle size down to 0.85 mm, beyond which a reverse trend was noted. It was also found that the fine size fraction (-0.075 mm) does not separate on the basis of size or specific gravity but follows the water distribution

Apr 1, 1995

By L Besra, A. R. Prasad, B. P. Singh

The role of surface-chemical phenomena and the physical processes that participate in the dewatering of a suspension of alumina trihydrate were subjected to a systematic investigation, which has increased understanding of the influence of surface tension, contact angle and adsorption in the process. The residual moisture content of the cake can be reduced significantly through the use of surface-active agents in slurry pretreatment or as wash-water additives. The effectiveness of a particular surfactant is hard to predict from any single parameter, but is dependent on its ability to reduce surface tension and possibly to modify the solid-liquid contact angle. If scaled up to industrial operation of the dewatering step of the Bayer process in India, the use of these chemical additives could substantially improve its process economics, reducing the fuel costs for thermal drying by a much as Rs 50/t

Jun 21, 1905

By P. P. Jenkins, T. G. Ball

Paper presented at the Drillex '90 conference held in London, 5 April 1990. Two drilling techniques are employed - guided longhole drilling and reverse circulation coring - for underground longhole exploration of the coal reserves and the fault structures that affect them. These are complementary to, or replacements for, surface boreholes, underground development drivages and seismic techniques. The developments of the drilling techniques and some case histories are presented in detail.

Jan 1, 1991

By Boorder De, B. S. Panov, A. B. Westerhof, V. A. Korcemagin

Paper presented at the conference on Economic geology in Europe and beyond II, models for <mineral deposits> in sedimentary <basins>, held in Keyworth, UK, 13-14 April 1994. The Hg and Sb deposits of the Mediterranean and Circum-Pacific Belts are often found at elevated structural levels, suggesting that their preferential occurrence in young orogenic belts is not a fundamental metallogenic feature but merely reflects their chances of surviving post-orogenic peneplanation. In western Europe their emplacement appears often to be related to late orogenic extensional events accompanied by a notable increase in heat flow. Although Nikitovka and Almaden have quite different settings, both appear to be related to deep-reaching shears. Together with brittle fault zones at higher levels, these provided pathways for fluid phases that originated at least partially within the mantle. The Nikitovka deposits are located in the Donets segment of the 2 000 km Pripyat-Dniepr-Donets palaeorift in the East European Platform. Initiated in the mid-Devonian with a possible Precambrian precursor, its listric boundary faults displace the Moho from a depth of about 50 km north and south of the rift to 35 km along the axes of the Pripyat and Dniepr segments. The steep central anticline of the Donets segment, within which the main Hg-Sb district is located, is interpreted to be associated with a reactivated fault reaching into the upper mantle. The Almaden syncline, formed during the Variscan Orogeny, may be an older pull-apart basin or half-graben associated with the collapse of the Cadomian Orogenic Belt. It is situated on a major ENE-WSW-striking shear zone which may represent a Late Cadomian transfer zone reaching into the mantle

Apr 1, 1995

By G. B. Harris, A. R. Laplante

Fine tungsten was used to mimic gold and fine and coarse silica and magnetite to mimic gangue. The optimum flow rate of fluidisation water varied from 1.7 l/min for fine silica to 5.6 l/min for coarse magnetite. Overloading at optimum flow rate was then investigated. With fine silica gangue no overload occurred under any of the conditions studied, and there was very little overload with fine magnetite. Coarse silica caused appreciable overload, but only after a significant bed of tungsten had been formed; with fine magnetite gangue the onset of overloading occurred earlier. Finally, with coarse magnetite severe overloading occurred almost immediately. Overloading was modelled using a first-order kinetic rate constant for erosion of the concentrate bed and a critical mass of constant above which it takes place. The results clearly demonstrate the importance of removing oversize to maximise recovery, particularly with a high-density gangue

Jun 18, 1905

By S. Henley

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: The database: a pre-requisite for large-scale use of AI in mining). Artificial intelligence is a term which has been widely applied to different techniques including rule-based systems using inductive and deductive logic algorithms, neural networks, learning systems and genetic algorithms. In principle it should be applied to adaptive statistical techniques. Some of these applications have been coded in languages which are specifically suited to the novel requirements of AI but are not easy to integrate with more traditional computing methods. Efforts have been made to bridge the gaps, particularly with database management systems and such efforts at integration should provide the key to future success in the application of AI. A field which has been termed "knowledge engineering" cannot be credible as such if it fails to provide easy access to raw materials of "knowledge" i.e. the data residing in databases. In the mining industry there are a number of significant areas in which AI could usefully be applied throughout the industry, but its advance is slow because of the lack or inefficiency of such database links. Current development of object-oriented database systems for geology and mining holds out hope for such integration in the foreseeable future

Apr 1, 1994

By H. S. Sichel, W. J. Kleingeld, C. E. Dohm

A model of ore value distributions is presented that is the culmination of a statistical approach rather than simply a model that has been successfully applied to the evaluation of ore reserves. Detailed geological and physical observations based on large sampling data sets have been used to support the statistical modelling. Fundamental to the modelling process is the concept that the occurrence of a given grade value in space is a function not only of the presence of the mineral but also of the fact that it is associated with a specific trapping mechanism. The concepts have been specifically applied to gold mineralisation

Aug 1, 1995

By J Kokado, N Hatta, S Yabushita

A theoretical model is described for prediction of the capacity of fines from porous ores, such as cokes and sintered ores, to be removed by a pneumatic, horizontal-type classifier prior to charging into a blast furnace. First, the influence of variation in the apparent density and drag coefficient of porous ores on removal efficiency is analysed from a stochastic standpoint. The effect on efficiency of collisions between particles in the classifying region is then examined analytically in relation to the ratio of the mass flow rates of particles and air (the loading ratio). Finally, a theoretical model is constructed that takes these factors into account. Theoretical and experimental results are compared and classifying efficiency is discussed from both experimental and theoretical viewpoints.

Dec 1, 1993

By J Hadijigeorgiou, R. W. Lawrence, R Pouling

The layered co-mingling method involves the disposal of waste rock with the addition, at predefined construction stages, of layers of dewatered mine tailings. The resulting waste structure displays bulk properties that are more favourable to acid rock drainage (ARD) control than the constituent materials alone. A laboratory test programme was conducted to examine the potential of this method. Columns containing different configurations of waste rock and tailings were percolation leached for 40 weeks and the leachates examined for various parameters. In the short term the chemical reactions that result from the introduction of dewatered tailings into rock waste can significantly improve the quality of the drainage. Columns with co-mingled material produced leachate with pH levels of 8, whereas leachate from the control column containing waste rock alone had a pH of 4. Larger-scale field tests are planned to determine the effect of the disposal method over the longer term

Apr 1, 1996

By S a m u e l D e a n

The author's written response to previous discussion was presented at the North of England Institute of Mining and Mechanical Engineers general meeting held in Newcastle-upon-Tyne, 8 April 1916, followed by further comments by Hare S. in support of his view that the conditions in English mines were the reason for less satisfactory results being obtained with heading machines and brief comments by Greener T.Y., President

Dec 1, 1916

By S. Babendererde

The twenty-ninth Sir Julius Wernher memorial lecture of the IMM, presented at Tunnelling '97, London, 2-4 September 1997. The tunnelling industry is well prepared to face the challenge from the population explosion in urban areas in the near future. Many well-established yet redundant concepts are still impeding progress, however, including the prediction of excessive surface ground settlements. The correct selection of TBM can minimise these, and ground deformations can be avoided completely if the appropriate techniques are applied. Advanced techniques have been used in the Tokyo Bay Crossing, where the tunnel lining was installed by robots. Other advanced techniques include the use of a sliding slip form to give temporary support to an extruded tunnel lining, the chemical processing of ground by polymers during earth-pressure balanced tunnelling and the use of electronic monitoring and steering devices in TBMs. There will be challenges to tunnelling in urban environments, as open cut techniques will no longer be tolerated. Two examples of mined stations are briefly discussed

Jun 19, 1905

By Qing Wang

In this method the state of an open-pit mine is represented by the number of benches that are mined in each predesigned mining phase (or pushback). Consequently, a specific mining schedule can be represented by a sequence of states which starts with the topography of the mine site and ends with the ultimate pit. For a given set of mining phases all feasible states are first generated and sequences of states are then evaluated for technical and economical feasibility. The best sequence, which gives the maximum net present value (NPV), is found by applying a dynamic programming optimisation algorithm. The algorithm also optimises the cut-off grade which satisfies the mill feed requirement for each planning period. It was found that the algorithm can be used not only for scheduling but also as an effective tool for analysing the effects of mining and milling capacities and cut-off constraints on the mining schedule and the total NPV. The algorithm, which was programmed in C, was successfully applied to a large Au-Cu deposit

Jul 1, 1996

By A. Sutton-Pratt

The African continent has been the most prolific producer of gold since mining began. Although most of this gold has come from South Africa, other countries have also been important contributors in the past. There is currently little production outside South Africa, Ghana and Zimbabwe, but the gradual globalisation of the industry over the past decade has resulted in growing interest in the region which bodes well for its future development. An outline is given of prospects and activity (or lack of it) in South Africa, Lesotho, Swaziland, Zimbabwe, Mozambique, Madagascar, Botswana, Namibia, Zaire, Tanzania, Kenya, Uganda, Rwanda, Burundi, Zambia, Malawi, Angola, Congo, Central African Republic, Gabon, Equatorial Guinea, Ethiopia, Eritrea, Djibouti, Somalia, Sudan, Chad, Libya, Tunisia, Egypt, Algeria, Morocco, Ghana, Ivory Coast, Liberia, Sierra Leone, Guinea, Senegal, Guinea-Bissau, Gambia, Mauritania, Mali, Burkina Faso, Togo, Benin, Niger, Nigeria and Cameroun

Apr 1, 1996

By J. A. Every-Brown

Case studies are presented of three derelict sites in Kent and Essex that provide a good cross-section of opportunities for second-generation commercial uses of former chalk, limestone, clay and gravel workings. A 240 ha abandoned chalk quarry at Grays in Essex, now known as Chafford Hundred, is undergoing mixed development to include leisure facilities, a range of housing and commercial areas and an enhanced environment. The 120 ha of Stone Marshes now comprises the Crossways business park and the Dartford international ferry terminal. Reclamation and servicing required more work than had been anticipated and the fact that the area was within the green belt added to the delays, but Blue Circle was eventually able to provide a comprehensive development of the entire area to a high environmental standard. Stone Pit 1 landfill, at Dartford in Kent, is a former chalk quarry 40 ha in area and with an original average depth of 35 m. Landfilling commenced in 1976 and during the period 1979-1984 the site operator designed, developed and installed a gas collection and flaring system. From 1986 a gas plant supplied up to 5 000 000 therm/yr of landfill gas to a local cement works and in 1989 a 1 MW power generation scheme, later expanded to 3 MW, was commissioned. Gas is currently also supplied to a metal refining company for use in internal combustion engines

Aug 1, 1994

By P. E. J. Pitfield, S. D. G. Campbell

The regional structure of shear and deformation zones in the belt, which is recognisable in plan view on Landsat TM images, is interpreted in terms of a conjugate-shear model. Gold mineralisation is related to this framework at a variety of scales. The principal recurrent structural geometries hosting deposits at mines such as Motapa, Durban, Charliesona, Cecil, Sunace, Turk group, Queens district, How, Peter Pat, Matabele Sheba, Goodenough, Old Nic and Bushtick are associated with shear zones and folds and include conjugate systems (shears, shear intersections, kink sets), side-step systems (en echelon segmentation, duplexes, monoclinal inflections, antiform-synform couplets) and interactions of the two. Linear sections of shear zones are generally poorly mineralised. The same geometries are identifiable on all scales from local to regional, so sections of regional structural lineaments or areas within mines should be prioritised for further investigation or development on the basis of the gold-bearing geometries observed to be dominant locally

Apr 1, 1996

By J. A. Hudson, X. D. Pan

A rock mass responds to excavation according to the properties of the intact rock, the network of contained discontinuities and the susceptibility of the rock mass to weathering. Large deformation often occurs when one of these components causes the rock mass to have a low strength relative to the stress conditions. Analysis of such large deformations forms a significant feature of current numerical modelling in rock mechanics. A practical large deformation problem of roadways in a coal mine is described, demonstrating the requirements for improving numerical techniques. The development of a numerical model is then summarised with particular attention to several concepts pertinent to large deformation analysis in geomechanics. A numerical case study is presented in which the developed finite-element model is used and the results are compared with the in-situ measurements. Conclusions are drawn for rock engineering that are also relevant to both civil engineering and mining engineering projects

Sep 1, 1991

By D. C. Bailey, D. I. Hodson

Paper presented at the annual joint meeting of the IMM and IMinE held in Harrogate, 31 January 1991. The Neves-Corvo copper-tin mine is the highest-grade large-tonnage copper operation in the world and is now arguably the most significant producing base-metal mine in Europe, rating in the top ten world producers of both copper and tin. A description is given of the initial exploration work and the development of the project from the orebody discovery in the Iberian Pyrite Belt of southern Portugal in 1977 to full operating capacity in 1990. The chronological account includes discussion of the main organisational, financial, technical and environmental decisions and of the various difficulties encountered, and the challenges of the future are identified. The project was brought in on schedule and within budget

Jan 1, 1991

By P. S. Heyns, M. Heyns

A computer model has been developed of mine hoisting systems in deep South African gold mines. Particular attention was paid to the contribution of different modelling assumptions for the guides and guide-roller assemblies. Objective functions indicative of guide-roller tyre endurance, slipper-plate forces and perceived vibration levels were introduced to quantify dynamic performance. These objective functions were used to compare models. It was found that the choice of guide and guide-roller models did not influence the forces on the guide rollers significantly for typical shaft and conveyance characteristics at typical levels of viscous damping coefficients. The rigid and finite-element guide models gave the same results as those of the effective-stiffness guide model, and while the latter is suitable for simulation for design purposes, the finite-element model should be used for unusual guide geometries

Jun 19, 1905