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By T. K. Bundtzen

Placer gold in the Iditarod and Innoko mining camps of western Alaska is derived from a suite of comagmatic, Late Cretaceous to Early Tertiary, alkali-calcic, meta-aluminous. volcanic-plutonic complexes and peralumi-nous rhyolite sills that intrude Mesozoic flysch. Heavy-mineral concentrates from 42 mining operations and streams draining known mineralized areas in the igneous complexes contain placer gold and a variety of ore minerals derived from epithermal to hypothermal conditions of formation. The minerals include cassiterite, ilmenorutile, samarskite, cinnabar, scheelite, chromite, stibnite, silver sulfosalts, monazite, and zircon. Results of the study show that 1) cinnabar. stibnite, and quartz formed with the bulk of the placer gold in an epithermal lode environment, 2) chromite appears to have originated in mafic phases of monzonite plutons and alkalic basalts, and 3) niobium-tin-tungsten-uranium-silver values may have been derived from stockwork accumulations in cupolas of monzonite plutons.

Jan 1, 1987

Determine the advantages and operational limitations of water-let-assisted cutting used with mining equipment. Approach The Bureau of Mines con-ducted a research study to evaluate water-Jet-assisted cutting both in the laboratory and in underground mines. Earlier research on water-jet-assist was limited to laboratory studies where bit speeds and penetration depths were very low and large cutting force reductions were reported. For the past years, research by the Bureau of Mines and others has been concerned with the application of water-jet-assisted cutting under more realistic mining conditions. Study Results Water-jet-assisted cutting employs a mechanical cut-ting bit combined with a moderate to high-pressure water jet directed just in front of the bit tip to assist in the cutting process. Recent Bureau findings show that the addition of the water jet to the cutting bit can improve cutting in harder materials, significantly reduce respirable dust and bit wear, and increase product size. Some of these findings are presented as follows.

Jan 1, 1987

By K. R. Johnson

Changes in the pattern of computer systems for mine planning and geologic evaluation are occurring as a consequence of the introduction of 3-D high performance graphics terminals. The VULCAN system is described and an outline of its functionality is discussed. Increasingly, the integration of both database systems and graphics and databases will occur, allowing a greater degree of information access to mine operators. The system covers areas of database, drillhole graphics, mine design and layout, surface and solid modelling as well as reserve inventory generation. The design of the software is such that it is fairly commodity-independent and entirely menu-driven, to enable non computer-trained personnel easily to access the system.

Jan 1, 1987

By E. Dermietzel

The fundamental ideas of Computer Aided Lignite Mining (CALM) with respect to hardware and software used at Rheinbraun are explained and outlined in detail. The computers used in the main data processing department and in the different departments in the mines are described. Special emphasis is laid upon the network connecting the computers at different places for data-exchange. Concerning technical applications, the main facilities of CALM are deposit and pit modelling, complex geomechanic computations and mass calculations, data recording from the production process in the pits and refining plants, and detailed information and planning systems for water management and mining equipment. Concerning administrative applications, the main facilities of the software are the accounting system with cost controlling and planning, the materials management system with stock control, forward planning and computer supported order procesing, a system for the administration of property within and surrounding the mines, and systems for personnel administration and payroll. The various software systems developed for these application and the influence of data processing technique, such as data base management and the interconnection of data processing systems, are demonstrated.

Jan 1, 1987

By C. R. Jenkins, G. S. Taylor

Three sedimentation ponds had their performance evaluated before and after installation of modifications. Each pond had a floating baffle installed, two had siphon outlets, and one had a floating outlet device. Baffles inhibited short circuiting, and the outlet devices retarded flow following a rainfall event and drained the pond, creating a large storage volume to maximize detention time. Total suspended solids and settleable solids tests were measured on samples of influent and effluent to evaluate pond performance. Particle size analyses were conducted on samples containing measurable amounts of solids. Performance improved in each pond, with baffles providing the major improvement.

Jan 1, 1987

By J. Douglas Causey

In 1986, at the request of the Bureau of Land Management, the U.S. Bureau of Mines studied the 7,940-acre Southern Otay Mountain Wilderness Study Area (CA-060-029), and the 5,750-acre Western Otay Mountain Wilderness Study Area (CA-060-028) in order to evaluate their mineral resources. The wilderness study areas are located in San Diego County, CA, about 20 miles southeast of San Diego. No mineral resources were identified in the Southern or Western Otay Mountain Wilderness Study Areas, based on literature, field observations, and sample results. The wilderness study areas are underlain by a complex blend of Late Jurassic, moderately metamorphosed sedimentary and volcanic rocks. Evidence of mineralization is not obvious.

Jan 1, 1987

By Edward J. Miller

Explosions and fires are without a doubt two of the most feared occurrences in modern underground mines. When they result in loss of life or substantial property damage, they usually gain world-wide media attention and have, on occasion, provided the impetus for legislative action. The very involvement of the Federal Government in mining was the result of a series of explosions which resulted in the loss of hundreds of lives. Fortunately, explosions of this magnitude are rare. Fires and explosions of lesser consequence are, however, more common and their severity may be more a matter of luck than anything else. The publicity which these events receive is usually restricted to the area immediately surrounding the mine and a1 though MSHA and sometimes the state prepare reports of their investigations, the general mining community is quite often aware of the circumstances surrounding these occurrences. This paper will discuss some of these "lesser" explosions which have occurred recently. These explosions have sometimes occurred in sealed or otherwise inaccessible areas of the mine involved, where conventional ignition sources such as electrical power were not present.

Jan 1, 1987

By R. Houot, C. Leschevin, G. Gillet

In mineral processing, conventional magnetic separators are equipped with traditional magnetic circuits (magnetic iron yoke with copper coils or iron-clad solenoid) that develop magnetic fields of less than 2 T'. For minerals of low magnetic susceptibility, use of these circuits has many disadvantages. Only a separator with a superconducting magnet can contribute to solving the problems and produce a high magnetic field. This paper presents and describes a magnetic separator having a superconducting magnet with integrated closed circuit for helium liquefaction. The system generator and maintenance are simplified by extensive automation realized by a versatile program- mable autocontrol unit. A comparative study if the results on concentration and purification of different raw materials with the new and with conventional separators is described.

Jan 1, 1987

By Gardavsky V, Gabell AR, Green AA

The I,)hyllosilicate mineral chlorite is a common constituent of altered rocks associated with volcanogenic massive sulphide deposits, and literature studies indicate that, in general, this mineral is progressively enriched in magnesium relative to iron as an orebody is approached. Studies have shown that there is a direct correlation between the Mg/Mg + Fe ratio of chlorite and its absorption spectra in the 2.7 to 3.0 um range. However, this region, which contains the fundamental 0-H stretch absorption features, is affected by intense atmospheric absorption, and therefore cannot be used for remote sensing. At shorter wavelengths (0.4 - 2.5um), there are windows where the atmosphere is sufficiently transparent and vibrational absorption bands still occur, although they are clue to overtones and combinations, and accord- ingly are much weaker than the fundamental features. Shifts to longer wavelengths with increasing iron content can still be observed in this region of the spectrum and, with better spectral resolution and sensitivity, it may be possible to monitor subtle variations in chlorite chemist by remote sensing techniques.

Jan 1, 1987

By Chang JF

This paper describes the advance in shaft sinking technique in terms of a vast complex of equipment in the last decade, and mainly recommends some ad- vanced technology and a vast complex of equipment, such as smooth blasting, la- ser guiding, shot-crete lining and rock- bolting, hanging bracket ring for drills, large-capacity wall grab, tipping device, storage bunker, and automobile haulage et.al., finaly, author in detail repre- sents some successful applications of advanced shaft sinking technique in some mines as an example.

Jan 1, 1987

By Donchak PJ, Lang SC, Hammond RL, Bultitude RJ

The Hodgkinson and Broken River Provinces form the northern part of the Tasman Orogen. They are separated by a broad belt of Late Palaeozoic igneous rocks, but were probably originally continuous. They are bounded to the west by a system of major faults (Fig. 1) which separate them from the Georgetown Province. Although largely Precambrian, the Georgetown Province includes probable Siluro- Devonian granitoids, and in the south adjacent to the Broken River Province, metamorphosed Early Palaeozoic(?) volcanics and sediments of the Greenvale Subprovince. South of the Broken River Province, the Lolworth-Ravenswood Province includes probable Precambrian rocks, Cambro-Ordovician volcanics and sediments, and voluminous Ordovician to Early Devonian granitoids. The first systematic studies of the provinces were the 1:250 000 scale mapping programs by the Bureau of Mineral Resources and Geological Survey of Queensland (White, 1965; de Keyser and Lucas, 1968). These and subsequent regional studies were reviewed by Arnold and Fawckner (1980). Remapping by the Geological Survey of Queensland since 1982, and a concurrent regional study of the deformation by Hammond (1986) have provided much new data. We acknowledge the contribution of other members of the GSQ field parties - L. Cranfield, J. Domagala, B.G. Fordham, P. Green, R. Halfpenny, R. Hegarty, L. Hutton, S. Law, D. Macansh, T. McLennan and M. Scott.

Jan 1, 1987

By A. W. Mitchell

Mining of a bedded barite deposit exposed highly pyritic siliceous sediments which have weathered and degraded subsurface and surface waters. The ph, sulfate, and total dissolved solids are the most seriously affected parameters. Several solutions were tried and eventually horizontal holes were drilled into the mine wall to draw down the water table and decrease the movement of groundwater through oxidizing zones opened up by the mining operation. Areas of surface disturbance were capped with layers of soil, bentonite, and gravel to decrease the infiltration of water into the disturbed areas. These actions have begun to decrease sulfate and total dissolved solids concentrations and increase ph values.

Jan 1, 1987

By Lawless JV

Recent exploration for gold on the Pacific Rim has utilised similarities between active hydrothermal systems and epithermal gold deposits. The major control over formation of such deposits is the hydrology of the ore-depositing hydrothermal system, which varies depending upon its geologic setting.

Jan 1, 1987

By J. E. Chilton

The Bureau of Mines has developed a portable flammable gas detecting system for estimating the flammable gas concentrations in a mine containing one or more combustible gases at concentrations up to 100 vol pct. With this portable detecting system, mine rescue or recovery personnel can quickly determine if they are working in a potentially explosive gas atmosphere and either leave the area or make appropriate changes in the fresh air ventilation of the mine to render the area safe. The detecting system uses a commercial, intrinsically safe, flammable gas detector with a range from 0 to 5 vol pct methane (CH4). The flammable gas detector has a catalytic heat-of-combustion sensor that can detect all flammable gases that would be encountered in a mine including methane (CH4), ethane (C2H6), carbon monoxide (CO), and hydrogen (H2). To determine the mine gas concentration, the rescue worker dilutes a sample with fresh air carried within the detecting system. The concentration of the diluted sample is then measured with the permissable flammable gas detector. The actual mine gas concentration is calculated from the product of the indicated diluted gas concentration and the system dilution ratio using a pocket calculator or the nomograph on the side of the unit.

Jan 1, 1987

By Photios G. Ioannou, Guillermo F. Salazar, Herbert H. Einstein, Yeong W. Kim

The MIT tunneling group has developed, over the past decade, a number of decision support tools for the geologist and engineer, planner and designer, owner and contractor involved in underground construction. These computer based tools can be used in the planning and exploration stage of a project, in predesign and design, in construction planning and during construction. Tasks as different as optimizing information collection during exploration and during construction, as selecting major design alternatives in predesign and modifying design during construction, as providing cost and time estimation and considering social and physical environmental constraints, can be handled. Output can be in the form desired by the user ranging from geologic profiles (cross sections) to management reports.

Jan 1, 1987

By H. J. Sohn

Systematic studies were carried out on the adsorption of the silver thiourea complex on activated carbon. The experimental isotherm data fit the Freundlich isotherm equation. The adsorption rates increased with increasing temperature and decreased slightly with the increase of free thiourea concentration. The concentration of sulfuric acid had little effect on the adsorption rate. Adsorption kinetics correlated well with the Elovich equation, indicating adsorption is the rate-determining step.

Jan 1, 1987

By Stephen J. Harven

Geologic conditions in eight northern operating sections of Jane Mine, Keystone Coal Mining Complex. Armstrong County, Pennsylvania are defined by utilizing drillhole data and underground geologic mapping. Three of the eight sections are experiencing difficult mining conditions in the Shelocta "0" coal seam (formerly the Lower Freeport). The five remaining productive sections will exhaust their reserves within one year. Coordinating mine planning with future production levels is aided by indicating areas that appear favorable and lack the geologic conditions that cause difficult mining. Roof rock 1 ithologies, lithologic variations in and below the floor, jointing, overburden thickness, coal splits, paleochannels. and clay veins are the principal geologic factors believed to influence mining conditions in Jane Mine. Careful definition of each cause allows for a reasonable assessment of future mining conditions.

Jan 1, 1987

By R. O. Dannenberg

The Bureau of Mines conducted laboratory investigations with the objective of developing an alternative process for recovering cobalt and copper from complex sulfide concentrates. Processes currently used depend largely upon precipitation techniques to remove impurities and recover cobalt from sulfate liquors prepared by oxidative pressure leaching of the sulfide concentrates. The Bureau conducted bench-scale research on a process for treating cobaltite concentrates, comprising (1) oxidative pressure leaching, (2) jarosite precipitation followed by H202 oxidation and pH control to remove iron and arsenic, (3) copper solvent extraction with a mixed hydroxyoxime-amine extractant, (4) copper electrowinning from recirculating acidic strip liquor, (5) selective cobalt extraction from copper solvent extraction raffinate with a phosphinic acid extractant, and (6) electrowinning of cobalt from a recirculating weak acid strip liquor. Overall cobalt and copper recoveries were 91.7 and 84.1 pct, respectively. Electrowon products assayed 99.8 pct Co and 99.89 pct Cu.

Jan 1, 1987

In the early 1950's, it was forecast that there would be, worldwide, a need for approximately sixty computers! Included in that estimate was provision for a considerable amount of geoscience modelling. Since 1950, the role and concept of the computer has changed. With that change has come alteration and adaptation within industry in order to better utilise the services and tools that computers can provide. For example the science of statistics prior to the computer was regarded as an intractible speciality. Computers have allowed the exploitation and further generation of statistical theory. In turn, as the science of statistics has become practical and relevant, the mineral geologist has moved from being essentially "a-numeric" to "non-numeric" to highly skilled in the application and use of very sophisticated statistical concepts. The modern computer provides the opportunity to perform many of the old practices more conveniently and/or economically and, perhaps more importantly, for exploration it provides- an enormous range of activities which previously would have been impossible. Such new activities allow for imaginative and creative application and extension of basic theory into practical situations, which when used by well trained, able people can open up new avenues of exploration. However, the use of such tools by poorly trained or incompetent people can lead to errors potentially as great as any success derived from the same tools. This paper reviews some applications of the computer to exploration, and attempts to discuss likely future developments.

Jan 1, 1987

By M. Ghiani

Biohydrometallurgy originated, some forty years ago, from an environmental problem, namely the serious pollution of the Ohio river by acid drainage water coming from neighboring subbituminous coal mines. Studies aimed at elucidating the cause of the intensive oxidation of the iron sulfide (pyrite) inclusions of those coals, led to the discovery of a bacterium, Thiobacillus ferrooxidans (Temple and Colmer, 1951), capable of acting as a catalyzer, accelerating the otherwise very slow chemical oxidation of iron sulfide to rates many orders of magnitude higher. However, it is now recognized that the biotechnology of microbial mining dates back to 1963, when the ability of this bacterium to solubilize copper from sulfide ores was ascertained (Razzell and Trussell, 1963). Much research has been carried out on biohydrometallurgy over these last 25 years and is still being actively conducted all over the world. The interdisciplinary nature of this young branch of science and technology is reflected by the variety of experts involved: microbiologists, mining engineers, hydrometallurgists, physico-chemists, mineralogists, solid-state physicists and biochemists. This intensive research effort has provided a solid background on the fundamentals of this technology, although many important issues have still to be solved, amongst which the enzymatic mechanisms controlling biocatalysis of mineral sulfides dissolution, the influence of bulk- and surface solid-state physics of metal sulfides on dissolution mechanisms, the interaction of the various strains composing natural microbial floras. Their elucidation should permit the rationalization of biohydrometallurgical techniques and the optimization of commercial processes. Biohydrometallurgy has already achieved satisfactory results: copper recovery from submarginal copper sulfide run-of-mine ores (i.e. assaying less than 0.3% Cu) by in-situ, dump and/or heap leaching is successfully practised in many countries and uranium recovery through bioleaching is competitive with other leaching processes.

Jan 1, 1987