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By David M. Mchaina, Allan E. Hall, W. C. H. Kruining, Alan Coode, Stephen Hardcastle

This paper details an investigation into the feasibility of recirculating mine exhaust air in Saskatchewan potash mines. This project was initiated following a previous study at Ruttan Mine, Manitoba, which indicated that recirculation of exhaust air to reduce winter heating costs was feasible. The potash industry was selected for study because the mines use a minimum of blasting in their production methods and the exhaust temperature is significantly higher than that of most metal mines. These factors simplify the monitoring system required and have the potential for greater waste heat recovery. A series of measurements of underground mine pollutants was made at the main exhaust and intake shafts in order to determine the feasibility of introducing controlled recirculation of exhaust air. An experimental recirculation circuit was created by opening two existing doors situated between the return and intake shafts. During this recirculation trial, the air quality parameters at the intake, mixed intake and exhaust measuring stations were monitored. The results obtained from a questionnaire circulated to the regulatory agency and the major potash producers together with results obtained from underground field studies at Central Canada Potash (CCP) Division of Noranda Minerals indicated that controlled recirculation of mine exhaust air has potential application in these mines either to reduce heating costs and/ or to increase the face air quantities. A recirculation system is to be designed in conjunction with CCP and the Saskatchewan Ministry of Labour, Mine Safety Unit to attempt to implement a working recirculation system for CCP.

Jan 1, 1989

By Mark W. Springett

The examination of relatively well behaved distributions subject to truncation by a cutoff grade in the mine clearly demonstrates that a bias is inevitably introduced when the selection is based on the results of samples which are subject to even the most idealised error distribution. The idealised error used in this paper is assumed to be normally distributed with a mean of zero and is thus unbiased. The bias introduced can be minimised but it cannot be eradicated. A better understanding of the bias can lead to improved procedures for mine sampling, sample preparation, assaying and estimation of selection units which will not only reduce the discrepancy but more significantly will increase the efficiency of mining selection and hence profitability.

Jan 1, 1989

By Jim Avraamides

Historically, much of Western Australia's gold production has come from the refractory sulphide-telluride ores located in Kalgoorlie's Golden Mile. Most of the recent gold boom has been associated with low grade, open pit free-milling oxide deposits. Primary sulphides are commonly encountered at depth and in many cases are highly refractory. Different approaches to the problem of recovering go1d from these ores have been adopted subject to local conditions both technical and environmental. The least preferred option is the preparation of a gold- rich flotation concentrate which is shipped to a smelter. Roasting of flotation concentrates can be practised in certain remote locations where sulphur emissions are tolerated. Fine grinding of flotation concentrates followed by direct cyanidation is another popular approach although this often leads to fouling of carbon by flotation reagents in the adsorption section and high soluble gold losses.

Jan 1, 1989

By Faust William A.

At Gold Fields' Chimney Creek Mine, gold ore deliveries to the milling and leaching circuits will come from three separate pits. The challenges in mine scheduling are to combine tonnage flows from these distinct ore bodies to produce a minimum of 4.665 kilogram (150,000 ounces) per year while maintaining a stable workforce and constant mine equipment requirements. A secondary goal is to have the end of milling operations coincide with the completion of leaching of the oxide ore reserves. This paper discusses the techniques used to prepare the long range plan and some of the considerations and practices that will be required for the plan's accomplishment.

Jan 1, 1989

By David J. Lowell

The gold content of porphyry copper deposits ranges from less than 0.05 g/t to more than I g/t ((0.0017 to 0.035 oz per st) and the average is about 0.05 g/t (0.0017 oz per st) gold. Perhaps the highest grade mineralization found near a porphyry cop¬per deposit is the Ok Tedi Gold Cap ore body whose grade falls in the 2 to 3 g/t (0.07 to 0.1 oz per st) range. It is difficult to define a gold-rich por¬phyry copper deposit. All porphyry copper ore bodies contain some gold, but there seems to be a fairly sharp break in the gold content at about 0.1 g/t (0.003 oz per st) gold. There is also a problem in identifying dis¬seminated gold deposits that may have an indirect relationship to porphyry copper systems. This relationship is clear cut in deposits such as the Ok Tedi Gold Cap, the El Hueso deposit, the Fortitude and West de¬posits at Battle Mountain, NV, and the Sur¬prise deposit at Ely, NV. There are many other bulk disseminated, epithermal-type gold deposits - McCoy, NV, for example - that might be related to a porphyry system but where this relationship is remains very uncertain. In such places as the Goldfields and Tonapah district in Ne¬vada and in the El Indio, Chile district, there may be a vertically stacked ore deposit rela¬tionship between near surface epithermal deposits and disseminated molybdenite and chalcopyrite enargite mineralization at depth that may represent a deep porphyry system. This, however, has not been positively demonstrated. Most of the bulk epithermal gold deposits are probably not related to porphyry copper systems. Exceptions would probably be Ok Tedi, El Indio, El Hueso, Battle Mountain, and Lepanto where vertical or lateral zoning relationships are more apparent. This author believes that porphyry copper systems are related to a relatively unique type of intrusion that is probably distinct from, for example, the McCoy intrusivebody. For that reason, deposits such as McCoy, Chimney Creek, and the like will not be included in the definition of gold-rich por¬phyry copper deposits for this article. The interpretation of the origin of several of the deposits previously mentioned are subject to an unusual amount of contro¬versy. For example, geologists seem to be equally divided about the presence of a porphyry copper deposit below the El Indio deposit. Geologic setting Continental vs. island arc Several geologists have speculated that the gold-rich, moly-poor, porphyries are

Jan 1, 1989

By J. Cheung, H. Rabia

The traditional methods for predicting mine air temperatures are based on steady state heat transfer models as developed by Voss (1969) and Starfield (1983). These models are useful in providing approximate predictions of air temperatures in trunk and gate roadways. More complex models are required to provide predictions along faces. In practice, the heat flow in underground mines is of transient nature and recent observations in some British Coal mines show temperature variations of up to 5°C during a working week at any one point. In addition, the recent introduction of district recirculation of mine air in British mines requires a more precise prediction of air temperatures during start up of the system or during breakdown. A transient heat transfer theory based on the work of Jordon is presented. The method lends itself easily to computers due to the large number of calculations involved. The proposed transient model is validated using actual temperature data collected in roadways in Wearmouth Colliery in the North East of England. The transient results are compared with the steady state predictions of Voss (1969). Finally, predictions of air temperature in roadways for a recirculation system will be made using both the transient and steady state models. Temperature predictions along faces will be made using a separate model.

Jan 1, 1989

By M. Stefanakis, A. Kontopoulpus, K. Adam

The application of Bacterial Oxidation as a pretreatment step for the extraction of gold from the Olympias refractory pyrite concentrate is described. A wide review of Bio-oxidation is presented focusing on the current process developments and commercial applications relevant to the treatment of gold bearing sulphide ores and concentrates. Preliminary batch and semi- continuous tests on the Olympas concentrate indicated that with Bacterial Oxidation quantitative gold liberation may be achieved. fie effect of such parameters as pH, Eh, temperature, particle size, operating pulp density and retention time on the extent of sulphur oxidation and subsequent gold extraction by conventional cyanidation are also examined. Finally, a preliminary evaluation of Bacterial Oxidation as a potential process alternative for the treatment of the Olympias concentrate is presented.

Jan 1, 1989

By J. M. Melluish

The metallurgical response of the Point Leamington deposit has been studied. Two series of bench tests were conducted and various ore samples and flotation products were examined using image analysis techniques. The majority of sphalerite and chalcopyrite grains in this texturally complex ore were found to be smaller than 10 micrometers. Copper recoveries were low with losses mainly as fine inclusions in pyrite. Sphalerite recoveries were somewhat better due to a generally coarser habit. Gold and silver recoveries were also low and only solid solution silver was identified in the ore. The deposit shows poor economic prospects unless additional tonnage of high grade zinc ore can be delineated.

Jan 1, 1989

By David S. Yang, Osamu Taki

The innovative Soil-Cement Mixing Wall Technique, developed independently in Japan, consists of mixing in-place soils with cement grout using multi-axis augers and mixing paddles to construct overlapping soil-cement columns. The applications of overlapped soil-cement columns include cutoff walls for groundwater control and structural diaphragm walls for excavation support. The special features of this technique include water tightness, versatile strength design, and efficient installation in subsurface materials varying from clayey soils to cobbles or soft rocks. Through the introduction of two recent subway projects in Japan, this paper presents the design parameters, construction procedure, quality control and performance of soil-cement wall for excavation support and groundwater control.

Jan 1, 1989

By E. Ilgar

Biodegradation of spodumene by Asnergillus niger has been investigated. This organism oxidizes sucrose to citric and oxalic acids (in approximately 50-sot proportions) which degrade the spodumene mineral. The kinetic effects of leach variables on the dissolution of lithium were determined. The maximum theoretically attainable rate of lithium extraction was calculated for the effect of pulp density, to be V : 3.01 x 10 kg m sand the corresponding constant value, K = 12.47% pulp density. The apparent activation energy of lithium extraction vas found to be ^E = 20.3 kJ and frequency factor A = 5.66 x 10 s for S-spodumene leaching by synthetic -3 citric and oxalic acids (each in 0.05 kmol m-3 concentrations).

Jan 1, 1989

By Jean-Michel Rendu

Equipment capital operating costs represent a significant portion of the total cost of most mining operations, and a variety of computerized methods have been developed to assist in the selection and effective use of this equipment. The questions to be answered and the tools available to answer these questions vary with the type of mine to be analyzed, the stage of development of the mining venture, the size of the operation, the details required, and the technical or economic objectives to be reached. Even though a majority of publications are directed towards open pit mining operations, the underground environment is not neglected. In the early planning stages of a mining venture, equipment selection is the problem to be solved. The simplest computer systems are designed to' automate time consuming manual tasks. A data base is supplied to and maintained by the user, which describes the technical and economic characteristics of available equipment. The user specifies the physical environment within which the equipment will be used and chooses from the data base a combination of loading and transport equipment. The role of the computer is to detemine the production which will be likely reached, the associated costs, and other relevant statistics. This approach is most helpful when modeling small operations or isolated parts of larger operations.

Jan 1, 1989

By Eric K. Albert

The permit generation and review process represents both a time consuming and expensive task for industry and government alike. Changes in regulations and in review procedures cause additional delays. This leads to potentially higher costs of doing business and the extension of time for a project to lie started. This paper describes the motivation and methodology of applying an expert system to function in the role of a permit reviewer. The problems of representing the knowledge of the reviewer and regulatory criteria are illustrated. Futhermore, the selection method for the expert system shell is addressed. Finally, a sample review is demonstrated to show the results of applying this artificial intelligence method to the process of permit review.

Jan 1, 1989

By T. H. Parker

The Guasare Coal Project is located a short distance from Lake Maracaibo, in the Northwestern region of Venezuela. In 1987, Carbones del Guasare, a joint venture comprised of Carbozulia, ACC Venezuela, a subsidiary of ARCO, and AGIPCoal of ENI Group, Italy, was formed to develop the Guasare coal reserves for world markets. Drilling with the Venezuelan state of Zulia has indicated a coal resource of over 6 billion metric tons. Further exploration has delineated the Guasare deposit as an area particularly suited for cost-effective surface mining. The calculated mineable reserves of this area (300 million metric tons) and the coal quality characteristics are based on extensive core drilling programs.

Jan 1, 1989

By Cheryl Lee Vatter

The Lupin mine consists of a gold mining, milling, and refining complex located 400 km (250 miles) northeast of Yellowknife and 100 km (60 miles) south of the Arctic Circle on the southwest shore of Contwoyto Lake in Canada's Northwest Territories. (Fig.1). The mine was commissioned in 1982 and is presently producing 6 t/a (193,000 oz per year) of gold from 612 kt (675,000 st) of ore. The success of this operation is due to such factors as the continuity and grade of the ore body, the competency of the host rock, low mining costs, efficient milling, the transportation of people and materials to and from the mine site, and the unique work schedule resulting in a stable workforce. Echo Bay Mines operated a silver mine at Port Radium on Great Bear Lake, Northwest Territories, from 1965 to 1982. The company first obtained an option on the Lupin property from Inco in February 1979 and completed an underground exploration program in 1979-1980. Topographic relief is low and vegetation is sparse in the continental subarctic climatic zone, consisting mainly of moss and lichens. Temperature extremes are from 24°C to - 45°C (+75°F to -49°F) with an annual mean of -12°C (+54°F). Permafrost extends from near surface to 500 m (1640 ft) in the ore zone. Its remote location and harsh climate presented some challenging design and logistical problems. Construction began at the Lupin mine site in 1980. Before construction, a 1.5-km (5000-ft) gravel landing strip was prepared, suitable for landing a C 130 Hercules. The entire Lupin project took 20 months to build. All of the men and materials were transported to the site with some 1100 Hercules flights and several hundred Convair 640 flights. The Convairs transported construction crews, which numbered 400 at their peak, and also carried 3.2 kt (3535 st) of supplies during construction. The facilities were constructed and commissioned for a total cost of C$135 million. The operation was originally designed to throughput 860 t/d (950 stpd). Expansion in 1983, circuit refinements, and some capital projects brought the daily throughput to 1.7 kt/d (1850 stpd). The underground mine delivers 612 kt/a (675,000 stpy) of ore to the mill at an average head grade of 8.46 g/t (0.3 oz per st). The ore is nonrefractory and is processed in a conventional cyanide leach using the Merrill Crowe process. Gold recovery is about 95.0%. The average production cost is $US5.85/g ($US 182 per oz) based on 1987 figures. Mining at Lupin – Geology The Lupin deposit occurs in amphibolite grade iron formation overlain by mudstones (phyllites) and underlain by graywacke (quartzites). Contacts between the wallrock units and the iron formation are well defined. It has been folded and tilted into a megascopic antiform-synform-antiform structure (Fig. 2). Gold occurs primarily within the sulfide rich iron formation, with some minor occurrences in sulfide poor iron formation. The distinction between sulfide rich and sulfide poor iron formation is based on a visual cutoff of 5% total sulfide content. Mining widths are determined by an assay cutoff of 4.2 g/t (0.15 oz per st) gold. There are few tons between 1.7 and 4.2 g/t (0.06 and 0.15 oz per st). The amphibolitic iron formation at the mine ranges from 1.5 to 20 m (5 to 65 ft) wide and has been followed over a strike length exceeding 1.7 km (5600 ft). The wider portions of the ore body tend to occur at its north extent and south nose. The gold-bearing iron formation appears on plan as a Z-shaped structure made up of three zones: the West, Center, and East. The West and Center zones dip steeply to the East (75° to 90°). Each of the ore zones plunge at an angle of about 65°. Total strike length of the three zones is more than 610 m (2000 ft). The zones are confirmed at a depth of 650 m (2130 ft) below surface. The Center zone is the widest and varies from 4.5 to 20 m (15 to 65 ft) while the West is the narrowest, averaging 1.5 m ( 5 ft). The footwall is comprised of quartzites that are strongly jointed and locally grades into phyllite, which comprises the hanging wall. The hanging wall and footwall are reversed in the West zone. Mineralogy of the ore at Lupin consists of amphibole minerals (hornblende, cummingtonite, and grunerite), feldspars, quartz, occasionally garnet, pyrrhotite, arsenopyrite, minor pyrite, and trace chalcopyrite. Also found in minor amounts are scheelite, apatite, epidote, calcite, tourmaline, and some arsenides (notable loellingite). Quartz

Jan 1, 1989

By Tad S. Golosinsk

Use of computers for hoist evaluation and design dates back to the early 1960's. Mine hoist production calculations, repetitive in nature, were computerized first. More elaborate modeling of hoist operations followed soon. Typical for this, early period are the models described by Touwen (1973), and by Albert and McIvor (1984). Apart from the simple hoist production calculations, the models were very complex, typically written in Fortran, and often required advanced computing facilities and expertise to run the simulation. The early models were strictly deterministic, with no consideration given to the random nature of hoisting operations. The effects of randomness of the hoisting process on hoist performance were often accounted for by introduction of the deterministic factors, most notably of an "utilization factor" related to the hoist production. The value of the latter was based on observations of actual hoist performance, and could vary in a wide range. For example Harvey (1973) reports values of the "utilization factor" to be between 0.7 and 0.92.

Jan 1, 1989

By K. Osseo-Asare

Metal recovery from solution, i.e., the formation of a solid product from a purified aqueous electrolyte solution, is increasingly becoming more than a simple matter of bulk precipitation. In many cases, operating conditions must be carefully manipulated to control the rate and yield of the precipitation/crystallization process, as well as the purity and physical characteristics of the solid product. A review is presented of the underlying physico-chemical processes, with emphasis on solution and interfacial chemistry. Opportunities for the integration of hydrometallurgical metal recovery and materials processing operations are discussed.

Jan 1, 1989

By M. Misra

The interaction of xanthate with SO2 in the flotation of sphalerite and chalcopy.ite is discussed. 'The SO depression of sphaledte is due to the decomposition reaction of xanthate by SO2 The decomposition reaction is dependent on the cole ratios of xanthate/SO2, oxygen concentration and pH. Xanthate adsorbs at a faster rate by chalcopyrite than sphalerite. The faster rate of xanthate adsorption by chalcopyrite and the specific action of S02 on the surface of chalcopy.ite facilitate the selective separation of chalcopyrite from sphaledte.

Jan 1, 1989

By Jianping Sheng, Francis Otuonye

The potential for methane and coal dust explosions in underground coal mining operations has increased in recent years with the introduction of fast coal-cutting machines. Dust explosions usually follow accidental ignition of a methane pocket. The dynamics of the explosion may be strong enough to pick up and disperse coal dust deposited on mine surfaces and ignite the mixture. A self-sustaining dust explosion can then develop and propagate at large distances. Ignition of dusts can result in a fire, and this may also lead to a dust explosion if the burning dust becomes airborne. Entrainment of dust and the resulting dust concentration in the gas stream are some factors which determine the features of the subsequent explosion and flame propagation. A model of coal dust transport in the gas stream due to the initial explosion is presented. In this model, equations for the conservation of mass, momentum and energy are coupled with the convective-diffusive model of dust transport. The system of equations is solved numerically to obtain dust concentration, convective velocity and gas pressure profiles.

Jan 1, 1989

By Jr. McCulloch

Mining operations of Freeport Indonesia (FI) are located approximately 4 degrees -6' south latitude, 137 -7' east longitude in Irian Jaya the eastern most state of Indonesia (Figure I). The mines are located approximately 96 km (60 miles) from coast in the Carstenz Mountain range. The ore bodies are between 2900 and 4000 meters (9500 and 13 000 ft) elevation.

Jan 1, 1989

By John S. Thayer, Frederick E. Brinckman, Kenneth L. Jewett, Gregory J. Olson

Interest and research in biorecovery of metals has focused mainly on cell-based metal leaching and precipitation. However, production of non-enzymatic metabolic products by microorganisms related to metals bioprocessing also deserves attention. For example, it is well known that biogenic inorganic (e. g. H2S04 ) and organic acids play a role in metal dissolution. There are other metabolic products of microorganisms which can catalyze useful metals transformations. These include methylated metabolites such as alkyl halides which can dissolve metals from ores and also reduce certain metal ions in solution to pure metallic particles. This paper describes some of our research on metal dissolution and precipitation by such metabolites. Examples include the production of high purity elemental metal particles of gold, platinum and palladium by volatile metabolic products.

Jan 1, 1989