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The metallogenic belts of the Central Andes (iron, porphyry copper, polymetallic and tin) are genetically related to an eastward migrating magmatic arc. The polymetallic belt of the Bolivian Altiplano formed during Miocene arc broadening and lies in a critical position for understanding the genesis of this zonation. It is penecontemporaneous with parts of the copper and tin belts, and shares many characteristics with them. The differences between the belts result from contrasting volcanic and feeder stock geometry, depth of erosion and country rocks, and are not due to variations in magma chemistry, age or Benioff Zone depth. Polymetallic mineralisation in the Altiplano is epithermal in style and mostly related to flow-dome volcanism. The intermontane basinal setting precludes deep erosion to expose the epizonal feeder stocks and predicted porphyry copper mineralisation. In contrast, erosion of the less abundant stratovolcanoes of the Altiplano-Puna and Pampean Massif may expose contemporaneous Miocene porphyry copper mineralisation in subvolcanic stocks. The tin belt is coincident with the Paleozoic fold belt of the Eastern Cordillera. The occurrence of minor tin in Altiplano epithermal deposits hosted by Paleozoic sediments, and the persistence of tin mineralisation in the tin belt over 350Ma, suggests that Paleozoic sediments are the source of the tin.

Jan 1, 1987

By Peri Mehling, Allister Brown

Environmental regulations concerning the processing of gold ores and the treatment and disposal of spent process solutions range from rigid standards in some locations to site specific options in several other jurisdictions. This paper examines the regulations and policies in two North American jurisdictions. Emphasis will be placed on the mill process and waste stream treatment and disposal, and implications for environmental impacts. Case examples of mine licence requirements will be discussed, with brief descriptions of individual treatment and disposal systems. Policies and environ- mental regulations within each jurisdiction will be examined in terms of potential environmental protection.

Jan 1, 1987

By K. T. Cunningham

The Oakfield, New York Hine of the United States Gypsum Company is a shallow, room and pillar mine developed in the Camillus Formation of Silurian Age on the up-dip edge of the northern Appalachian Basin. The gypsum comes to subcrop beneath a variety of glacial materials and is subject to solution activity by groundwater. A geologic environment unfavorable to mining activity is thus created. Since 1978 seismic studies have been used to supplement core drilling to determine a conservative boundary between normal and questionable mining environments. A single channel seismograph, originally in use, is now replaced by a twelve-channel unit and is used to determine bulk material velocity which is the basis for defining the mining limit.

Jan 1, 1987

By Madgwick J

A novel method for determining viable cells of the mineral leaching bacterium Thiobacillus ferrooxidans has been developed. The cells were collected on 0.45/Lm cellulose acetate filters, washed with artificial minewater, and incubated in the presence of ferrous ion at pH3 in an atmosphere containing radioactive (14C) carbon dioxide. Colonies of bacterial growth were detected by the image formed on X-ray photographic paper (autoradiography). The method was compared with three conventional techniques and shown to detect three orders of magnitude more cells in cultures of Thiobacillus ferrooxidans in the late exponential phase of growth.

Jan 1, 1987

By David C. Lager

While not a new construction technique "top/down" construction is seeing increased use in high rise building construction. Using diaphragm wall, drilled shaft and mining construction techniques, top/down construction enables construction of both the below grade basements and high rise structure simultaneously. To date the top/down method has been used on at least four major building projects in the United States. This paper will review the economic, engineering, construction and schedule issues associated with top/down technology on two projects -Olympia Centre, Chicago, and One Westwood, Los Angeles. Top/Down construction is currently under consideration on several additional projects in the United States.

Jan 1, 1987

By Hoffmann CF

Thermal conditions at depths of several k.i'-.r.,etres in hydrothermal systems are a major (actor controlling gold transport into the epithermal environment. Understanding of the coupling of thermal, metal and ligand (HZZ S) sources in the root zones of hydrothermal systems therefore becomes important for the application of tectonic and igneous petrochem- ical studies to regional scale precious metal exploration. The evaluation of favourable conditions in this source zone and application to explor- ation rests on a detailed knowledge of the gases, H2S, CO2 hydrocarbons and other trace components preserved in fluid inclusions. Recent developments in analytical techniques now permit examination of these components and the recognition of complex hydrocarbons in rluid inclusions from epithermal and other lydrothermal systems appears promising for ieoosit-source correlation.

Jan 1, 1987

By Thomas H. Koenning, William E. Bruce

Determination of the state of a mine fire is an important function during firefighting and during rescue and recovery operations. It is imperative that an accurate, up-to-date assessment of fire conditions be available for persons directing such activities in order to avoid unacceptable risk to mine rescue teas and/or fire fighters. Many indicators which consist of ratios of the concentrations of fire gases have been developed over the years for determining the state of a mine fire. Results from numerous gas sample analyses are necessary for determining the trend of the fire. Some indicators are preferred because the influence of sample dilution, a frequent problem, is said to be eliminated. Definitions and examples of indicator6 found to be useful in diagnosing recent western U. S. coal mine fires are presented. Mine gas explosibility is an important subject also requiring rapid assessment. Example explosibility calculations are presented applying one widely used method. Establishing limits for withdrawal of personnel are discussed.

Jan 1, 1987

By M. D. Loy

In addition to products available from private vendors, many useful programs are developed at universities - in fact, many of these programs led the way to commercial development. Other projects are assigned to consultants with backgrounds in system design and mining. Both types of development have led to programs that can be acquired for the cost of a tape or disk. This paper highlights several underground mining packages. These programs consist of: ? USBM model-developed by the United States Bureau of nines. ? PSU model-developed by Pennsylvania State University. ? VPI model-developed by Virginia Polytechnical Institute and State University. ? NUS model-developed by NUS Corp.

Jan 1, 1987

Boring of a 7.5Km long tunnel under the city of Stockholm commenced in January, 1987. The 3.5m diameter tunnel will pass under the buildings and as no ground settlement is allowed, the regulation for water leakage into the tunnel is very strict. Probe drilling will be carried out continuously ahead of the boring and when water is encountered the rock has to be grouted before passing with the TBM. The tunnelling system enables probe drilling to be carried out during boring with the TBM. This has earlier been a capacity reducing factor as the whole operation has been stopped during probe drilling. The project is using a new generation TBM especially developed for hard rock formations which require higher thrust per cutter to get a high penetration rate.

Jan 1, 1987

By D. R. Maneval

The vast coal resources of North Slope, Alaska, can be expected to attract substantial interest because the nearly flat-lying coal beds of the coastal plain are specially amenable to surface mining. Mining on a scale large enough to justify coal development in this area could have severe environmental effects. The mitigation would be uncertain because large-scale coal mining and reclamation operations have not been carried out in the arctic. The deficiency of the scientific data base is another factor that requires consideration if coal mining has to develop in accordance with the objectives of PL 95-87. The objective of this paper is to establish the inter-relationship between the problems due to permafrost and factors in reclamation of post-mining land in order to find ways to transform nature in a rational and purposeful manner and to suggest specific reclamation approaches that may be appropriate in this region.

Jan 1, 1987

By R. Y. Wan, J. R. Parga, J. D. Miller

The direct recovery of precious metals from a1kaline cyanide solution is frequently accomplished by the well-established Merrill-Crowe process involving zinc-dust cementation. This is particularly true for silver. Plant data from two operations are presented and analyzed in terms of intrinsic reaction features. In such Merrill-Crowe plants a plate-and-frame filter press acts as a semicontinuous fixed-bed reactor with a distribution of particle retention times. For the plants studied, 99Yo of the silver is recovered with a solution retention time of less than 2 min. Differences in plant operating conditions and product characteristics can be related to the nature of the surface deposit of silver which forms on the zinc particles. From laboratory experiments and plant samples it has been found that the presence of lead in the system activates a change in the silver deposit morphology to the dendritic state which affects the rate of silver deposition as well as the filter cake porosity. Finally the plate-and-frame press is considered from an engineering perspective as a semi- continuous fixed - bed reactor to describe the behavior of the system.

Jan 1, 1987

By Demaerel. J. P.

Arsenic plays a major role during electroreflning of copper. Both the arsenic content in the anode and the arsenic concentration of the electrolyte have, in conjunction with other impurities such as lead, antimony, bismuth and oxygen, a direct influence on the quality of the cathode. The mechanisms are currently slime. inclusion and precipitation of insoluble compounds in the bulk of the electrolyte. Arsenic has also been reported to have a depassivating effect on the anode. An influence on the anode slime adhesion has also been found. A literature survey is given and these data are compared with and completed by our own results based on lab and pilot scale experiments as well as on Olen tank.house practice.

Jan 1, 1987

By J. W. Oberholzer

Problems with gravimetric sampling have led to the establishing of a computer linked tyndallometer dust measuring system. Preliminary tests conducted with the system indicate that the system can be used to do correlative exercises between mining activities and dust levels. The system also allows occurrence characteristics of dust levels to be determined. Use of this equipment will enable dust allaying methods to be tailored to the specific underground situation.

Jan 1, 1987

By E. Grygiel, J. Haynes, T. McNider

Jim Walter Resources Blue Creek No. 3 Mine was opened in one of the most gassy coal beds in the United States. Although face ventilation requirements exceeded 14,000 cfm (6 .6m3/s) air, continuous miner sections experienced an unacceptable frequency of frictional ignitions. Modifications offered primarily by the U. S. Bureau of Mines such as diffuser fans, water spray fans, and slow speed cutting motors were used with little success. However, laboratory tests conducted at the U. S. Bureau of Mines indicated that an increase in bit attack angle from 50° to 55°-57° significantly reduced the chances of the bit causing a frictional ignition. An experimental miner drum was built using this concept coupled with a new bit designed by the Bureau and manufactured by Hughes Tool Company that better protected the bit steel shank with a carbide cap. It was installed on a continuous miner and placed in an area of the mine prone to ignitions. 50,000 tons (45,500 metric tons) of coal were cut without a frictional ignition. When the miner was withdrawn for rebuild and a machine with an unmodified cutting drum placed in service, two ignitions occurred before 10,000 tons (9,100 metric tons) were mined. Other machines have been rebuilt and are in service, and to date none have been known to cause an ignition.

Jan 1, 1987

By Sathit Tandanand

This report presents a Bureau of Mines study on the time-dependent behavior of coal measure rocks for future implementation in stability analysis and safety evaluation of in-mine rock structures. This initial study focused on moisture adsorption rate and strength degradation of shales in Pennsylvanian coal-bearing strata in the Illinois Basin. A reaction of clay minerals in Illinois shales with atmospheric water vapor was hypothesized as the adsorption and strength degradation mechanism. Part of energy exchange between shales and the environment was attributed to a free energy controlled by pore pressure of the rock and partial pressure in the environment. The relationships between adsorption versus time and strength degradation versus moisture content were derived and correlated with the experimental data. Partial saturation at various levels of relative humidity occurs within approximately 2 weeks at room temperature. The strength of shales tested decreases linearly with increasing moisture content. When the moisture exceeds 7 pct of the dry weight, these Illinois shales become unstable. To this end, the moisture content is a good predictor of rock strength for shales.

Jan 1, 1987

By K. Nagata, T. Kawashima, S. Tejima

The expanding volume of maritime coal transportation is intensifying the problems concerning large vessel service, port construction, trans-shipment, and environmental control. The major problem is the shipment of coal. Customary methods for bulk transfer must be improved and new systems developed. Slurry unloading has a key role in the new systems. This report reviews progress in slurry transportation research that has been done in Japan since the 1960s, when large-scale experiments for domestic transportation were done. Experiments on the effects of vibration on the slurry cargo and on reslurrying are focused on.

Jan 1, 1987

By J. E. Geier

This Bureau of Mines report reviews hypotheses for the mechanism by which water jets reduce the specific energy of cutting for drag bits. Several of these hypotheses are shown to be inconsistent with published evidence and new observations. The notion of a limiting cutting speed, above which water jets would be incapable of rendering assistance, is shown to be improbable. The hypothesis that seems most plausible is that specific energy reductions are mainly due to the erosion of crushed materials from in front of the bit. This hypothesis leads to a prediction that, for a given rock type and jet-bit configuration at a constant depth of cut, the reduction in bit forces should be a function of dM/dx, the jet energy spent per unit length of cut. This dependence upon dW/dx is shown to be consistent with other workers? results.

Jan 1, 1987

By Estoque J, Abaigar J, Domingo B, Acenas M

The Siana gold-silver deposit of Surigao del Norte, Mindanao, Philippines is perhaps one of the most complex in the world, being related to an ancient suture zone known as the Philippine Fault. Early accounts described the deposit as epithermal, consisting of an upper limestone replacement orebody and a lower vein type deposit hosted in andesite. Recent field and laboratory studies, in correlation with the latest findings on the archipelago's tectonic evolution, however, led to the present interpretation of the Siana ore deposit's origin as involving both syngenetic and epigenetic processes, with limestone breccia, similar to the Cow Head Breccia of Newfoundland, as the principal host to mineralization.

Jan 1, 1987

By R. J. Sweigard, R. V. Ramani

Three case studies were undertaken to investigate the role of land use potential evaluation in reclamation planning and to determine the impact of regional differences on final land use plans. The three surface mines studied were representative of operations in the Appalachian, Interior, and Northern Great Plains provinces. The scope of the investigations included a survey of regional characteristics, a detailed investigation of the mining operations and site conditions, and an assessment of local land use planning activities in the area of the mines. Special attention was given to key factors that presently determine the use of reclaimed land. Also, for each case study, the postmining land use potential was evaluated using site planning principles. Specifically, the environmental, economic, and social impacts of several potential postmining land use plans were considered.

Jan 1, 1987

By K. Verghese, H. M. Lee, R. P. Gardner, K. Boateng

Results of work on the development of a phenomenological model for the continuous flotation process wing short-lived radioactive tracer techniques for determining model parameters is reported. A model that incorporates a flotation first-order rate constant and a residence time distribution based on the cross-flow finite-stage (CFFS) model has been derived and investigated. The short-lived radioactive tracer techniques and the nonlinear search methods necessary to extract the model parameters have been developed. The conditions under which all the model parameters can be extracted from a single radiotracer experiment are detailed and illustrated. A micro- computer-based unique data logging system has been designed, assembled, and implemented for collecting the necessary transient radiotracer data. Results are reported for a continuous laboratory flotation process for the two systems, mica ore and coal.

Jan 1, 1987