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By Ora H. Rostad

The sequence of events preceeding the discovery of the Mount Emmons molybdenite include some inadvertent near misses by several groups. The events are given in general chronological order to bring out the essentially contemporaneous, but different activities by several groups in two areas on opposite sides of Mount Emmons. The Mount Emmons molybdenite deposit lies in the Elk Mountain mining district. The west edge of the deposit is near the boundary between the Elk Mountain and Ruby mining districts as shown by the USGS map included (see Fig. 1). Considerable history regarding the Keystone silver-lead-zinc mine is given because of its proximity to the Mount Emmons molybdenite deposit which is on the other side of the mountain from Redwell Basin and where other significant activities took place. It should be noted that there was no documentary evidence available to me that would indicate that molybdenite was recognized to be present on, or under, any part of Mount Emmons, including Redwell Basin, before 1970. Veins containing silver-lead-zinc minerals were discovered in the Elk Mountain and Ruby mining districts about 1872. Some discoveries on the south flank of Mount Emmons about 1880 were developed into the Keystone mine. The Keystone has the largest cumulative production of metal ores of any of the mines in these districts. Most of the 413 Mt (455,473 st) of ore produced from the Keystone mine through August 1967 was produced after 1950. The ore averaged 175.4 gt (5.64 oz per ton) Ag, 2.62% Pb, 5.56% Zn, and 0.72% Cu.

Jan 1, 1991

Improve ground control in longwall gate entries by developing a practical method for evaluating longwall pillar designs. Background Longwalls have emerged as the most important technology to be applied to underground mining since the continuous mining machine. Longwall mines currently produce more than 30 pct of all the underground coal mined in the United States, up from less than 5 pct just 15 years ago. Safe longwall mining depends on maintaining ground control in the gate entries, the lifelines that provide access to the longwall face. In multientry retreat mining as practiced in the United States, rows of chain pillars are left to protect the gate entries (see figure 1). Chain pillars are subject to severe and complex abutment loads during the process of longwall panel extraction. The design of these pillars is often the single most important element in gate entry ground control and has been the subject of intensive Bureau of Mines research.

Jan 1, 1991

By F. Arslan

Gold extraction from refractory ores is still a problem. Gold losses in the cyanidation process are mainly due to the presence of sulfides and carbonaceous materials. Oxidation of carbon and sulfide minerals by sodium hypochlorite is a possible method to render the ore amenable to cyanidation, and earlier work by the USBM indicates that electrochemical generation of hypochlorite is promising. Laboratory work was carried out on the oxidation of pyrite and carbon in an electrochemical cell with a sodium chloride electrolyte. The results of preliminary tests are discussed in relation to the mechanism of electrooxidation of refractory gold ores and the estimation of current efficiency.

Jan 1, 1991

ACCUMULATED FUNDS Balance at 30 June 1990 (Loss) income over expenditure for the year (63 154)

Jan 1, 1991

The following is based on two examples of emission control with coal fired power stations as practised in Germany at Heilbronn Block 7 power station and the Rheinbraun coal combined power station with integrated high-temperature Winkler system (HTW). Heilbronn Block 7 demonstrates the successful emission control of sulphur and nitrogen oxides and the (HTW) system the reduction of the specific carbon dioxide emission. Both were sparked off by legislation which demanded certain emission control standards. Since the early eighties environment protection has been a matter of heated public debate in the European Community. A recent survey in Germany showed unemployment as being the only subject matter more frequently in the minds of people than environment protection. A new kind of forest devastation in areas away from industry has caused investigations by several government departments and private enterprise. Because of lack of conclusive evidence so far, the principle of PRECAUTION has replaced the CONCLUSIVE evidence as a base for new legislation concerning the environment. The new legislative standards for nitrogen oxide emissions in Germany for example have reduced NOx emissions of power stations from 1000 mg NOx per cubic metre of flue gas in the beginning of 1983 to 200 mg NOx per cubic metre of flue gas in April 1984. These new standards were enshrined in legislation when research provided some evidence linking nitrogen oxide emissions through photo-chemical reactions with forest devastation. Thirty European countries signed a treaty in 1983 expressing their concern about air pollution and their willingness to co-operate with each other in controlling large scale emissions.

Jan 1, 1991

By Felicia F. Peng, Wenguang Wang

The purpose of this research work is to predict the dust concentration distributions of different particle sizes on longwall faces. This Is necessary because the dust sources must be identified before dust control techniques can be recommended and applied correctly. The dust concentration data at longwall faces were determined by using Real-time aerosol monitors (RAM-1) and gravimetric monitors. However, these field data cannot explain the nature or the mechanisms of dust flow phenomenon on longwall face. Therefore, a mathematical model Is developed taking Into account the characteristics of airflow, the natures of dust generation and particles, the mechanisms of dust transport and deposition as well as the multiple dust sources on the longwall faces. In this paper, the identification of respirable dust sources on the longwall faces are determined. The dust particle size distributions In various longwall faces are analyzed and classified. The comparison analyses of field data and model predictions are presented. Specifically, the general trends of dust concentration on the longwall faces obtained at different positions and at various conditions are discussed.

Jan 1, 1991

By Kosta Fytas, Nour-Eddine Chaouai

"Selection of the appropriate kriging plan during indicator kriging estimations is of a paramount importance to the precision of ore reserve estimation. However, very little is known on the sensitivy of indicator kriging results when changing the kriging plan parameters (mainly search distance and number of samples). This paper evaluates the effect of the search distance and number of samples on indicator kriging results using a gold deposit as a case study.IntroductionBlock estimation using kriging is based on the autocorrelation function (variogram) on one hand and on the kriging plan on the other. As far as the variogram is concerned it is more or less subjectively adjusted and this is reflected on its parameters (range, sill, nugget effect and anisotropy). The effect of a poor estimation of these parameters on the kriging variance of ordinary kriging has been proven very important (Brooker, 1986). Choosing a kriging plan is generally a difficult matter depending on the estimation type (global or local). Generally there is not a unique kriging plan be cause there is not a unique structural analysis (variogram). There are no rules or dogmas in choosing a kriging plan but it is rather a function of the sampling pattern (David, 1982).Structural analysis requires the hypothesis of quasistationarity but very often either the data available within the zone of quasi-stationarity are too many so that the search distance is reduced during kriging or the data are too few to satisfy a stationary kriging system (Journel and Huijbregts 1978). As a rule, the larger the neighbourhood, the more precise the estimates should be , but for large neighbourhoods the hypothesis of stationarity does not always hold (Rivoirard 1987; Armstrong and Champigny 1989)."

Jan 1, 1991

By J. R. Woolsey, B. G. Noakes

A prototype remote placer drill (RPD) has been designed and successfully tested in the offshore gold district of Nome, AK. The RPD system is unique in its design and in the cooperative support that was provided during its development by industry, academia and government. The RPD was conceived as a low-cost, rapid drill sampling system for the reconnaissance of marine precious metal placer deposits. The drill functions as a counter- f lush system. It incorporates a dual wall casing and a rotating percussion bit driven by way of a drill rod through the central eductor casing by a heavy duty pneumatic rock drill. The cost of drill sampling in the exploration of marine precious metal placers has traditionally been high due to the technical difficulties imposed by the environment and the remoteness of the sampling target. The objective was to reduce capital and operating costs of a drilling program through the development of a portable system incorporating drill compoments having a high power-weight ratio that could be deployed from work vessels of opportunity. A principal design requirement was to operate the system remotely from the sea floor with only flexible connections to the surface. This includes cable for deployment and retrieval and hoses for air supply and sample recovery, thus making the drill system semi-independent of the vessel's sea-induced motion. The prototype RPD underwent full operational test off Nome, AK in late summer 1988. It was deployed from the landing door of a modified LCT vessel, and rigged for a single pass of 5 m (16.5 ft). More than 50 holes were drilled in a wide variety of bottom materials typical of the off shore Nome submerged beach placers. The prototype RPD proved to be an overall success, recovering representative samples throughout the section in all but the heavy boulder ground. Compared with a conventional drill system on board that was assigned to a production drilling system, the RPD was capable of reliably sampling moderate ground less than 6 m (20 ft) in thickness, using a smaller crew and operating in higher sea conditions.

Jan 1, 1991

By Zhou Jiemin

A mathematical model is developed to determine the economic thicknesses of refractories and insulations in rectangular furnaces, Both the heat loss cost and the lining investment are taken into account to achieve a minimum operation cost. For the sake of calculating the heat flux, the paper is particularly concerned with the simulation of the three-dimensional transient heat conduction processes in the lining and a Douglas-Rachford method is used to solve the finite difference equations, The model has been used to design an industrial electric resistance furnace operated periodically. the values of temperatures and power consumption measured from the furnace correspond with the model results.

Jan 1, 1991

This paper outlines the advances made in vacuum filtration as developed by Outomec Process Filters and details the results obtained at a number of Australian installations. The first section of the paper details the technical advances made by the use of ceramic media in vacuum filtration and explains the reasons for the use of the technology. The second part of the paper discusses a number of Australian installations of the ceramic vacuum filter and where possible compares the actual experiences with those predicted from the test work which preceded the installations. The Ceramec Capillary Vacuum Filter is a vacuum disc filter which combines the proven mechanical attributes of a disc filter with exciting new ceramic vacuum technology from Outomec of Finland.

Jan 1, 1991

By S. Anderson

Advances in inexpensive computer automation led to the development and utilization of a computerized ore control system at Cyprus Coppers tone Gold Mine near Parker, Arizona. These new ore control practices improved accuracy, performance, and productivity of the ore control effort. An automated system for data collection, including bar coding of blast hole samples, laboratory analysis, data management, grade estimation, cut delineation, and ore zone stakeout, plays a major role in ore control practices. This is of particular interest because of the large amount of blast hole information being processed, analyzed, and reported daily.

Jan 1, 1991

"In numerous meetings, conferences and discussions over the past year, the Conference Board of Canada has been impressed with the efforts of Canadian organizations to improve their competitive position. The attempt should be made to try to pull together and synthesize what has been heard. The topic of this paper, however, is even more daunting. The task is not only to analyze and discuss what is happening now, but also to look into the future—to the year 2000.The future seems to have an endless capacity for surprises, often unpleasant. This is one of the lessons learned in the twentieth century, particularly over the last 15 or so years.This paper covers three areas of managing in a changing com¬petitive environment: (1) the major global and domestic trends that will influence the ways in which Canadian organizations are managed (2) how Canadian companies are responding or will need to respond to these trends; and (3) the implications of the preced¬ing for human resource management and human resource professionals."

Jan 1, 1991

By Francis B. Gularte, James E. Monsees, John-Paul Whyte, Gary E. Taylor

In a short section of the Los Angeles Metro Rail system approximately 222.5 m (730 ft) of 6.4 m (21 ft) diameter twin-tube tunnels separated by a 1.8 m (6 ft) narrow pillar were designed to pass under a major eight lane freeway and a metropolitan intersection with only 3.7 m (12 ft) to 5.8 m (19 ft) of loose fill and alluvium cover. The design considerations and the chemical grouting program used to stabilize the alluvial materials is discussed. Also included is a discussion of the novel shield used for tunnel excavation and the effects of the subsequent fire.

Jan 1, 1991

By Dale Nies, David P. Childs

The open pit gold and silver mining operations in the State of Nevada have historically used simple row by row, echelon, or chevron delay patterns. Common practice has been to use detonating cord trunklines and either detonating cord downlines or nonelectric common in-hole delays in conjunction with surface delays. Several operations use a series of downhole nonelectric delays with an entire row loaded with the same delay to develop similar patterns.

Jan 1, 1991

By H. Scott Swinden

"ForewordA symposium on base metal deposits was held in Bathurst, New Brunswick, from June 10-13, 1990, sponsored jointly by the Geological Surveys Branch of the New Brunswick Department of Natural Resources and Energy, the New Brunswick Prospectors and Developers Association, and the Geology Division of the Canadian Institute of Mining, Metallurgy and Petroleum . Papers prepared for the symposuim are being published as a series of articles in the CIM Bulletin. This second paper (the first was by Fyffe, et al., in Vol. 83, No. 938) in the series presents an overview of the paleotectonic settings of massive sulphide deposits in the Dunnage Zone of Newfoundland with emphasis on volcanic geochemistry.ABSTRACTCambrian and Ordovician volcanic sequences of central Newfoundland, which record the history of the Iapetus Ocean, are prolific hosts to volcanogenic massive sulphide (VMS) deposits. Geochemical, isotopic and geochronological studies show that the vestiges of Iapetus in Newfoundland probably record a complex series of island arcs and back-arc basins that were marginal to, rather than part of, the main ocean basin of Iapetus. The geochemical and isotopic data provide a means of characterizing the tectonic environment of individual volcanic sequences, and allow us to identify a number of distinct tectonic environments in which VMS depositiontook place.Four tectonic environments have been identified as being associated with VMS deposition: (I) back-arc environments hosting VMS deposits include both N-MORB-type ophiolites (e.g. Skidder?) and volcanic sequences with oceanic island (or within plate) tholeiite characteristics (e.g. Great Burnt Lake); (2) primitive arc environments include both supra-subduction zone (SSZ) ophiolites (e.g. Betts Cove, Rambler) and volcanic/epiclastic sequences (e.g. Point Leamington, Duck Pond) and are characterized by abundant arc tholeiites, with lesser refractory lavas and rhyolites; (3) mature arc environments comprise dominantly thick felsic and mafic volcanic piles in the Buchans - Robert's Arm Belt (including the Buchans camp) and are characterized by dominantly calc alkalic basalt and andesite; and (4) continental rift environments occur in the Hermitage Flexure area (e.g. Strickland deposit) and are characterized by dominantly felsic volcanic sequences.Island arc environments are by far the most prolific hosts to VMS deposits. Patterns of VMS distribution in central Newfoundland show that similar tectonic settings may be recorded by very different stratigraphic sequences (e.g. both ophiolites and thick volcanic/ epiclastic sequences may record primitive arc rifting) and emphasize the importance of the rifting in VMS generation, irrespective of the details of the tectonic or stratigraphic setting. The ability to judge the prospectiveness of a volcanic sequence by using whole rock geochemistry to evaluate its tectonic environment may prove useful in area selection at the grassroots exploration level."

Jan 1, 1991

By Chen Xizhe

The caisson is adapted to the foundation of concentrated heavy building. As there are the flowing sand, boulder or cobble and other serious obstruction, the open caisson can't sink, the caisson can solve these problems easily. Especially for the stability of the neighour building, the merit of the caisson is outstanding. Therefore, there are the pier, the foundation of heavy instrument and the large water pumping station etc. using the caisson in China. This paper introduce several caissons and successful experience by author's investigation. It contains the feature and application of the caisson : the examples of caissons such as a huge pier of a bridge acrossing a big river, a large instrument foundation and a large water pump station beside a river; the problem of the design of the caisson and notice items during the caisson construction etc.

Jan 1, 1991

By Michael D. McGill, John L. Turner, Don Sieger, Doyle Newhouse

Since its introduction by Atlas Powder Company in late 1986 as a means of highwall stabilization in surface coal mines (1), applications of the basic AirDek (2) blasting technique have multiplied rapidly.

Jan 1, 1991

By M. D. G. Salamon

In view of an urgent need for a simple means of simulating the behaviour of stratified rock masses, a long-dormant linear model is revived, generalized, and discussed in some depth. The model is piecewise homogeneous, consisting of a pile of homogeneous isotropic laminae in which the interfaces between beds are parallel and free of shear stresses and cohesion. The continuity of stresses and normal displacements is assured across the bedding planes and, to maintain simplicity, the theory of thin plates is used as the kernel of the model. The paper covers the case where the rock mass consists of discrete beds in which the layers are arranged either heterogeneously or systematically. The stratification is regarded as uniform when all the layers are of the same thickness and their Young's modulus changes exponentially with depth; and as homogeneous when all the laminae have identical thickness and properties. The case of uniform stratification is also treated on the basis of an equivalent quasi-continuum derived from the basic model. Attention is focused on the derivation of influence functions. It is demonstrated that the quasi-continuous models, when they are available, can replace their distinct-layer counterparts. The homogeneous quasi-continuum, which permits the derivation of its influence functions in closed form, facilitates the determination of the roof and floor convergence. In the case of a significant class of problems, the convergence distribution is defined by a second-order differential equation in the xy plane, which simplifies to a Poisson's equation if the mining excavations are unsupported. With this result, the paper prepares for the solution of a host of practical problems. These solutions are presented in a series of papers that are in the course of publication.

Jan 1, 1991

By B. M. Van Vliet

SYNOPSIS This paper outlines the principles involved in the regeneration of activated carbon for renewed use in the recovery of precious metals or the purification of water. While chemical methods are effective in restoring the activity of spent activated carbon containing only single or defined adsorbates, thermal methods have to be used when the spent carbon is loaded with a heterogeneous mixture of adsorbates such as those normally present in industrial process streams or effluents. The steps involved in thermal regeneration are described, together with the operating conditions that can be controlled to give the required degree of activation. Finally, an account is given of the structural changes that occur in a new or spent activated carbon during thermal treatment.

Jan 1, 1991

By Perry M. Jones

An important operational and environ-mental concern associated with in situ leaching activity is the balance between solution injection and recovery. Solution balance is an important indicator of the capability of a particular in situ hydrologic design to efficiently and effectively control and distribute leach solution within the target ore zone. The Bureau of Mines is investigating the factors that affect solution balance in an unsaturated ore deposit, as part of ongoing in situ leaching hydrologic investigations at the Cyprus Casa Grande Mine. Flow conditions in 58 injection and recovery wells at the Casa Grande In Situ Leaching Test Facility were monitored daily over an 18 month period. Changes in the balance between injection and recovery occurring during this period were evaluated using analytical and statistical methods. The results permit estimation of solution distribution and the volume of solution stored in microfractures and interstitial pore spaces within the deposit following 18 months of leaching. Approximately half of the difference between well injection and well recovery can be accounted for by solution movement through macrofractures into nearby drifts. Estimates of solution storage within the ore deposit at the end of 18 months of leaching range from 3.5 to 6.9 pet. of injected solution. These results also suggest that 13 to 26 pet. of the fracture/interstitial pore space in the deposit was saturated with solution after 18 months of leaching.

Jan 1, 1991