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By William X. Chavez

The Mantos Blancos copper-silver district is located in northern Chile about 45 kilometers northeast of Antofagasta, as shown in Figure 1. Disseminated and veinlet copper and copper-iron sulfides containing economically significant silver values are hosted by andesitic to rhyolitic volcanic rocks of probable Jurassic age (Chavez, 1983). Field, mineralogical, textural and lithochemical evidence show that three major alteration types may be recognized within the district: (1) district-wide sodium metasomatism, manifested as albitization of feldspars and development of albite veinlets and pore-fillings, (2) local to widespread, incipient to intense addition (chloritization) or removal (bleaching) of magnesium and iron and (3) local to widespread, moderate to intense hematitization, usually spatially associated with bornite-digenite-covellite (as specularite) or digenite-covellite-chalcocite (as red hematite staining with or without specularite) mineralization. Carbonatization, occurring as veins, veinlets, vesicle fillings and irregular patches of calcite, varies in magnitude of development but is widespread. Sericitization of feldspars and groundmass is only locally intense yet is generally present as incipient alteration throughout the district. The district-wide albitization of the Mantos Blancos volcanic sequence has altered what were originally more potassic and calcic, less sodic, rocks to what are now more properly referred to as keratophyres (Battey, 1955; Gilluly, 1935, Hughes, 1975). The petrographic and lithochemical characteristics of the three major alteration types noted above are summarized below.

Jan 1, 1984

By P. Campbell, E. M. Gardy, L. Hachkowski

Introduction The efficient process control of a uranium mill and its associated mining operation requires a nearly continuous knowledge of the uranium concentration in the ore. Generally, the approach is to use laboratory assays of grab samples from the mill feed belt. In some cases, elaborate and expensive systems have been used to ensure random sampling, but even with these systems, mass-balance discrepancies still exist. There is a requirement for an on-line instrument that can give a prompt, accurate analysis of a large portion of the feed stock. The authors have recently evaluated a laboratory system that achieves these goals using neutron activation and delayed neutron counting. The development of the on-line uranium ore analyzer is a consequence of previous work done at the Whiteshell Nuclear Research Establishment (WNRE) (Campbell et al., 1978 and 1981), and is based on the emission of delayed neutrons after the neutron irradiation of fissionable materials. The mechanism of delayed neutron emission has been described (Keepin, 1965), but briefly is as follows. The fission fragments resulting from irradiation are in an excited state. Certain of these delayed fission products, precursors, decay to a more stable state by the emission of a delayed neutron. The delayed neutrons can be divided into six groups with effective half-lives ranging from 0.2-55 sec. It is important to note that more than 50% of the delayed neutrons are emitted within the first 6 sec after irradiation; this has an influence on the design of the analysis instrument. Measurement Cycle The measurement cycle involves a neutron irradiation, a delay time, and a counting period. The laboratory demonstration model of the ore analyzer comprises a californium-252 neutron source, a source chamber, a pneumatic transfer facility, and a neutron irradiation and counting module (Fig. 1). The ore sample is placed in the irradiation chamber. The neutron source is transferred to the center of the chamber for a 5-sec irradiation while the helium-3 thermal neutron detectors are switched off. As the source returns to the storage chamber, the detectors are switched on and the delayed neutrons counted. The total assay cycle is 16 sec. The current instrument design calls for the ore to be cut from the main belt every 16 sec by a mechanical arm and dropped into the analyzer directly, or via another belt. The cycle starts when there is a sufficient mass of ore in the irradiation chamber to depress a switch and stops when the delayed neutron count is finished. The ore is then dropped through the bottom of the analyzer chamber and returned to the main belt. The counts from each cycle are accumulated and the data reduced to give the desired information. Key for Fig. 1 A-Helium-3 neutron detector B-Wax moderator for neutrons C-Irradiation chamber D-Funnel for receiving ore E-Gate F-Transducers G-Biological shield for neutron source H-Transfer tube for neutron source I-Neutron source J- Microprocessor K-Accumulator for hydraulics L-Control panel M-Electro-hydraulic servo valve to control movement of the source N-Electro-hydraulic proportional valve to control movement of the gate O-Hydraulic power unit Irradiation and Counting Equipment Irradiation of the ore is achieved using a 1 X 10 7 neutron*s-1 californium-252 neutron source. The source is contained in an iron capsule and pneumatically transferred between the irradiation/counting and storage chambers. The irradiation/counting chamber possesses 12, 600-mm (24-in.) long helium-3 thermal neutron detectors embedded in an annulus of wax (Fig. 1). Two sets of six detectors are each interfaced to a preamplifier, amplifier and single-channel pulseheight analyzer system, and the two systems are connected to a scaler. A special timing unit controls the transfer of the source and the on and off switching of the detector assembly, in sequence with the movement of the source. Results and Discussion In the experimental demonstration, using the 107 neutron.s-1 source, a 10% uranium ore was measured to ± 10% (2o total error) in 10 cycles and ±6% (2o) in 100 cycles. Since a larger source was not available, it can be statistically predicted that a 109 neutron-s-1 source could be used to measure a 0.1% ore to ± 10% (20) in 10 cycles. The uranium can occur as discrete nonhomogeneous particles in the ore, and the error caused by such a distribution of particles is ± 4% (2o), as determined by

Jan 1, 1984

Jan 1, 1984

By Donald E. Zipperian

The studies described in this paper have established that flotation conducted in a column cell provided with gas generation by aspiration into surface tension lowered water, may considerably increase the efficiency and particle size range of a flotation process. Operation of a DEISTER FLOTAIRE ® Cell at several Southwest United States flotation plants under continuous rougher, scavenger and cleaner conditions has demonstrated the main positive features to be: (a) higher capacity per unit volume than conventional flotation equipment, (b) improvement of flotation of plus 0.210 m particles, (c) improved flotation of particles minus 0.037 m.

Jan 1, 1984

By R. P. Vinson

The Bureau of Mines examined the effects of high humidity and water droplets on the GCA Corp. real-time aerosol monitor (RAM--l). which uses a lO4mm cyclone preseparator. Tests were conducted both in a laboratory and in a full-scale model mine entry. The laboratory tests were conducted in a test chamber saturated with moisture and water droplets. Under these extreme conditions. the RAM-I responded by indicating dust concentrations of 1-1/2 to 2 mg/m3? although the air was dust free. Within the first 2 h of each test. water accumulated in the cyclone and affected the cyclone particle separation characteristics. resulting in readings of 3 to 4 mg/m3. In addition. condensation formed inside the RAM-I case and affected the liquid crystal display (LCD). However. the full-scale mine entry tests revealed that the RAM-I can function ac-ceptably in an atmosphere of water vapor and water droplets similar to the most severe conditions found in an underground mine.

Jan 1, 1984

By DiStefano AB, Dale SG

This paper describes the laboratory study implemented to investigate the application of the subaerial technique to tailings disposal for the proposed Olympic Dam Mine. The results of the study and the resulting design parameters are presented. The subaerial technique of tailings disposal is described and the advantages of the method for disposal in arid climates highlighted.

Jan 1, 1984

By W. A. Haley

Wheel loaders became important bulk materials handling tools in the early fifties. As they grew in stature, productivity, reliability, and acceptance, the demand for larger, more rugged machines evolved. In the early sixties, the introduction of a 6-yard model by a major equipment manufacturer led quickly to widespread experimenting and rapid worldwide acceptance in loading blasted rock in stone quarries and smaller metal mines. As the wheel loaders grew in popularity for shot rock loading, larger models, 12- to 15-yard size were developed and saw widespread use by 1970. In the past 20 years, at most quarries and small to medium size mines, most cable operated power shovels have been replaced by large wheel loaders and more recently, hydraulic excavators as the primary loading tool. Wheel loaders larger than the 15-yard class are not used widely. Until about 1970, very few overburden haulage trucks were used in domestic coal mines. About that time, many states started enforcing stringent mine relcamation regulations and in 1977, even more stringent federal legislation was passed. These controls brought about drastic changes in coal surface mining methods in the mountainous areas of Appalachia, in smaller midwestern mines and in the large mines of the western states. Basically, simple material casting methods were replaced at most eastern mines by "haul-back" and "mountain top mining" methods using controlled placement of overburden as it is removed from the coal. These methods dictated much more extensive use of loaders/ shovels and trucks to the point that most coal mining in those areas is now by loader/shovel trucks methods. And those areas have become the home of the country's largest population of large wheel loaders and trucks in the 35- to 85-ton size class with a trend to even larger trucks and shovels. To maintain equal production or provide for growth, the new methods have caused a sharp increase in machine intensity to the extent that at some mines, up to three times as many machines were required to mine a million tons of coal in the late seventies as compared to the machine needs in the sixties. Mining costs and coal prices also took a big jump in the mid-seventies, paralleling the drastic price increases in oil and other forms of energy.

Jan 1, 1984

By Robert B. Fulton

Summary of data and estimates for 52 fluorspar properties in the following 13 foreign countries: Mexico Thailand China (PRC) Morocco Tunisia Italy Spain South Africa France United Kingdom Kenya Namibia Federal Republic of Germany Data includes deposit type, resource tonnage and grades, mining and beneficiation methods, annual production, fluorspar products and by-products, manpower requirements, capital and operating cost estimates. For operating properties, engineering and cost data have been developed for present and anticipated levels of production. Hypothetical operations have been assumed for undeveloped deposits.

Jan 1, 1984

By K. Haramy

Coal mine bursts or bumps involve the violent, rapid failure of coal and rock in or around a mine excavation. Failure is normally associated with high stress and brittle or brittle-elastic materials; in coal mining, bursting may also be associated with desorbing gas, and this type of failure is termed an outburst. This paper discusses factors affecting coal mine bursts and several methods to predict bursts, including microgravity, microseismic, rheological, rebound, and drilling-yield methods. Methods to avoid burst conditions using volley firing, hydraulic fracturing, and auger drilling are also discussed. A case study is presented in which the redistribution of stresses and displacements was found to be associated with a burst at a deep longwall coal mine. The research showed that stresses are redistributed following the burst.

Jan 1, 1984

By T. E. Ackman

Scale inhibitors and slow-release polymers were tested by the Bureau of Mines at mine drainage treatment facilities. The scale inhibitors were investigated to determine their effectiveness in controlling gypsum (CaSO4) scale; the polymers were investigated to determine their effectiveness for increasing settling rates of suspended iron hydroxide. Two types of scale inhibitors were tested at a site having a severe CaSO4 scaling problem. Both proved to be effective in controlling scale formation; in addition, one caused the dissolution of CaSO4 deposits. Slow-release polymers were tested at three mine drainage treatment facilities. These gelatinous polymeric flocculants were found to be convenient and easy to use, but only effective when pH could be controlled.

Jan 1, 1984

By Wen H. Su

Multiple seam mining and its associated problems are very serious in Southern West Virginia where poor planning or lack of knowledge in seam interaction often results in complete loss of coal properties. Several measures have been proposed to alleviate the interaction prob¬lems under various multiple seam conditions, but few of them are spec¬ific in terms of mining plan. Two parallel approaches are adopted for this paper. One is field investigation which consists mainly of mine site visits and gathering of data. The other is the two-dimensional finite element simulation of mine workings using the data gathered as input. Two typical cases which represent the past and present multi¬ple seam mining practice in West Virginia were investigated. Much attention is focused on the interaction problems experienced and the important parameters controlling interaction. Several key parameters controlling interaction in multiple seam mining were analyzed. Proper mining plans, by which the interaction problems can be minimized, are proposed for the individual cases after a better understanding of the interaction mechanism was realized through finite element analyses.

Jan 1, 1984

By Edward C. Dowling

Froth flotation has been used industrially for many years to separate valuable minerals from their associated gangue constituents. Notwithstanding the significance of this process to the mineral industry, many of the engineering tools needed for the evaluation of the flotation process are still in a developmental stage. Traditionally, the evaluation of a flotation test on both the laboratory and industrial scale has been based largely on a rougher recovery value achieved at a sufficiently long time to give a "final" or "equilibrium" recovery value. The assumption of a time equivalency for a given recovery value between various flotation tests or between laboratory tests and industrial operation underlies this method of evaluation. Such an assumption implies that flotation is an "equilibrium engineering process" and that the time-rate recovery of material from the flotation cell is not affected by changes in the flotation system. It has been shown by Bushell (1) and by Klimpel (2) that the assumption of time equivalency between various flotation tests is unjustified. Consequently, better tools are needed for evaluating flotation test results, Because mathematical flotation models which incorporate both a recovery and a rate function can completely describe flotation time-recovery profiles, they can provide an excellent tool to evaluate flotation tests.

Jan 1, 1984

By Jack Green

Within three major tectonic time frames of earth history: Microplate (±3.8 - ±2.6 billion years), intraplate (±2.6 - ±1.3 b.y.), and macroplate (=1.3 b.y. - present), precious - metal deposits are confined to specific structural, depositional and physico-chemical environments. Precambrian primary gold deposits are localized in two microplate greenstone episodes (±3.7 and ±2.7 b.y.); secondary gold in Witwatersrand placers (±2.6 b.y.). Precambrian primary platinum group metals are in anorthositic facies of layered mafic intrusions (±2.8, ±1.8 and ±1.0 b.y.). Most radioisotope mineral dates cluster - at these times and are coincident with inflections on polar wandering curves. These coincidences may reflect episodicity in lunar tidal disruptions and global deceleration effects in crust and outer core during micro- and intra- plate phases. Macroplate tectonics and an oxygenated atmosphere created favorable conditions for strata-hosted and plate suture gold and silver deposits. "Black smokers" at constructive plate margins and calc-alkalic calderas at destructive plate margins are loci for hydrothermal gold and silver.

Jan 1, 1984

By George W. Heunisch

The properties of Neutra-Fix® and Neutra-Ment® , two new lime substitutes for the treatment of acid mine drainage (Arm), have been compared with lime and Alkament®, two products presently in use for AMD treatment. The two new products are basically dolomitic byproducts and produce sludges that are more compact than those from lime. Sludge settling rates are faster than lime with iron concentrations after 24 hours that comply with EPA regulations. Material utilization and optimum pit are reported.

Jan 1, 1984

By Giovanni B. Barla, Stefan H. Boshkov

The block caving method is examined in this paper on the basis of experimental results and observations in the field, and through the use of numerical modeling by the Finite Element Method. The Grace Mine, developed by a panel caving method, served as a reference case. However, the results obtained and the simulation techniques which have been developed may find useful application in more general conditions as encountered in other mining operations by block caving. Following a brief description of the Grace Mine and of the mining method, the problems associated with the behavior of underground drifts at the production levels, during undercutting and caving, are addressed. The most important results obtained through monitoring of strains and loads in the supports of a runway are discussed, while giving relevance to the sequence of mining operations in the immediate vicinity. The most important geomechanical data, as provided for subsequent modeling, are described with reference to: (a) rock mass characterization and (b) in situ state of stress. Then, the numerical modeling procedures, developed by the Finite Element Method in order to predict the caving phenomena and the behavior of underground openings during undercutting, are discussed. Finally, an attempt is made to compare the pre- dictions of the numerical analyses with, the measurements carried out at the instrumented site. Suggestions as to how to improve the results both qualitatively and quantitatively are also given.

Jan 1, 1984

By M. Misra

Improved liberation and flotation of kerogen from eastern oil shale were accomplished with high-temperature grinding and a1 so with the addition of fuel oil during the grinding stage. Liberation measurements indicated that possible coalescence and aggregation phenomenon of kerogen particles during grinding may reflect this behavior. Additionally, ultrasonic treatment of the rougher concentrate prior to cleaning improved the quality of separation.

Jan 1, 1984

By Doris M. Hyde

The Government of Belize maintained strict control over spending in 1982 as a means of protecting its import-dependent economy against the effects of a general worldwide recession. The modest economic performance was not expected to differ substantially from the $152 million2 gross national product (GNP) estimated for 1981. Exports and reexports were expected to decline in 1982, partly as a result of the Mexican peso devaluation. Imports were also expected to decline slightly in 1982, but the overall trade deficit was projected some-what higher than the $44 million experienced in 1981. On September 21, 1982, Belize became an independent state. As a result, the new Government became eligible for assistance from international organizations such as the International Monetary Fund, the International Bank for Reconstruction and Development (World Bank), and the United Nations Development Program (UNDP). Belize's independence from its former status as a colony of Great Britain was marred somewhat by the unsettled territorial dispute between Great Britain and Guatemala. Guatemala declared Belize was a part of Guatemala and. therefore. refused to recognize it as an independent state. Negotations between Great Britain and Guatemala continued without resolution.

Jan 1, 1984

By D. E. Ranta

Orebodies with intricate three-dimensional shapes (such as porphyry molybdenum deposits) are difficult to model using geostatistics or other computer-assisted methods. The strong trends in their spatial grade distributions occur as mathematically complex shapes and prevent the customary assumption of local stationarity that is required for accurate ore reserve estimation. "Zoned Kriging", a new method developed by AMAX, solves this problem directly by using the geologist's interpretation of the ore zones as a parameter in the kriging equations. The geological basis and methods used in the Climax ore zoning technique are reviewed and discussed relative to their application in zoned geostatistical modeling. The Zoned Kriging technique is described and demonstrated using data typical of mineral deposits.

Jan 1, 1984

By Richard J. Goff

Technical Support, one of several major organizational units in the Mine Safety and Health Administration, provides technical assistance to the mining community in all areas of health and safety. One of its many areas of expertise is noise control. Depending upon the needs of the operator or inspector, the services provided can range from locating major noise sources to actually building noise controls. Over the years a vast amount of knowledge has been obtained as to what will work and what will not. DESIGN GOALS While many noise controls have been developed for mining equipment and operations, the most acceptable (ergo successful) have achieved the following design goals: - a noise level reduction of at least 5 decibels; - minimum interference with production; - inexpensive to install; and - effective in reducing low frequency noise.

Jan 1, 1984

"At a current mining rate of 3,750 tons per day, La Mine Doyon is currently the largest gold mine in Canada. La Mine Doyon is an open pit gold mine located in the Abitibi area of Northwestern Quebec. The project is a joint venture between Soquem, a Quebec Crown Corporation in the resource development field and Lac Minerals Ltd., a publicly-held, resource development company. Lac Minerals is the managing company and operator of the project.Doyon went into production in 1980 on a very limited basis at 600 tons/day, and has seen a step wise increase to the current rate of 3,750 tons/day. Initially, all the ore was processed at Noranda Mines, Horne Division as flux for the copper smelter. The East Malartic Mill in Malartic was then upgraded and began processing Doyon ore. The third step in the progressive increase of throughput was the commissioning of the Doyon mill in November of 1982. Doyon ore is currently being processed at all three locations.During 1983, an exploration ramp was driven to explore the ore below the ultimate pit depth. Current plans indicate the sinking of a shaft and the commencement of underground mining during the next 2 or 3 years.Since its humble beginning, La Mine Doyon has always been a success; ore reserves have been extended to the east and the west and will soon be confirmed at depth, the mining and processing rates have been increased 6 fold, and the recovery has been increased from a designed recovery of 85% to over 95%. The intent of this paper is to trace the history and reasons for these rather dramatic improvements."

Jan 1, 1984