Search Documents

By A. K. Mukherjee, J. E. Dorn

A modified Peierls model is Presented for the rationalization of the asymmetric plastic behavior of single crystals of bcc metals. The model assumes that the asymmetry of slip arises from a tendency toward asymnetric splitting of the a/2[111] screw dislocation. The approach differs from former theories however insofar as it assumes that the splitting is so minor ttut only the core energy is modified and that no real partial dislocations exist. As a consequence, the concepts of a line energy of a partial dislocation, interaction between partial dislocations, constriction energies, and stacking fault energies are not invoked. Instead the present analysis is based on a specialization of the Peierls mechanism which assumes an asymmetric dislocation core which is modified by the effective stress and permits cross slip. The theoretical predictions on the stress-temperature -strain rate and orientation relationship agree qualitatively with the limited experimental data that are currently available. Additional experimental work over wider ranges of conditions is suggested to provide more complete evaluation of the possible validity of this theory. RECENT experimental investigations on the low-temperature thermally activated deformation of bcc metals have confirmed the existence of several unique orientation effects. These will be described with the aid of the standard stereographic projection shown in Fig. 1. If slip were determined exclusively by crystal symmetry, the deformation characteristics would be symmetrical about X; = 0 and independent of whether the specimen were subjected to a tension or a compression stress, regardless of what combinations of slip planes might be operative. Experiments, however, reveal that neither of these symmetry based predictions are valid. A schematic representation of the commonly observed asymmetry of both the yield stress and the plane of slip is shown in Fig. 2. A reversal of the direction of stressing results in an inversion of the asvmmetric behavior. 1) Asymmetry bf Yielding. A detailed investigation on the asymmetric yielding in an Fe-2.7 pct Si alloy was repoEted by Tabka, Tikeuchi, and Furubayashi,1 Similar trends have been observed by Keh and Nakada on iron,' Stein on molybdenum,3 Bowen, Christian, and Taylor4 on columbium, Sherwood, Guiu, Kim, and pratt5 on Ta, Cb, and Mo. The degree of asymmetry not only depends on the atomic number and alloying but, in all cases that have been examined, it also increases with a decrease in the test temperature. 2) Asymmetry of the Slip Plane. Asymmetric $I-~: curves of the type shown in Fig. 2 have been found for several Fe-Si alloys6-8,1 and columbium.4 There is general agre_ement that near X: = 30 deg slip occurs by the [111](211) mode so that ?1 = 30 deg. As X; decreases it appears that [111](211) to [111](101) cross slip takes place leading to slip band traces on intermediate planes. And as xi approaches 0 deg, sharp

Jan 1, 1970

By D. S. Tomalin, D. F. Stein

The effect of reducing oxygen to low concentrations on the fracture of high-purity iron single crystals has been examined at 78° and 20°K. It is found that iron single crystals grown by the strain-anneal method usually contain a few occluded grain boundaries which may become embittled in the presence of oxygen, thereby nucleating cleavage fractures. High purity with respect to interstitial elements was found to inhibit twinning and evidence is presented for an orientation dependence of the resolved yield stress. Deformation occurred by slip rather than twinning at both temperatures of testing with elongations of as much as 9 pct at 20°K. THE fracture properties of iron single crystals have been observedl-3 to be a function of temperature, orientation, and purity. Allen, Hopkins, and McLennan1 demonstrated that at 78°K iron single crystals became increasingly brittle as the tensile axis approached the (001) pole of the stereographic unit triangle. Iron crystals with the tension axis near a (001) pole were completely brittle and orientations near the (011)-(111) boundary were very ductile, achieving a 100 pct reduction in area prior to fracture. Later work of Biggs and pratt2 and of Edmondson3 demonstrated that by reducing the carbon content of the single crystals the transition between brittle and ductile failure at 78°K could be shifted to orientations nearer the (001) pole. Ed-mondson went further and pointed out that any mechanism which tended to increase the yield strength of the iron (i.e., carbon addition, pre-strain) also increased the tendency for brittle behavior at 78°K. Thus by a reduction of carbon content Biggs and Pratt were able to obtain ductile behavior to within 20 deg of the (001) pole, and Ed-mondson was able to obtain ductile behavior to within 26 deg of the (001) pole. Edmondson's material had a total interstitial content (carbon, oxygen, and nitrogen) of approximately 60 ppm and, although Biggs and Pratt reported no analysis, indications were that their iron contained comparable impurities. Stein, Low, and seybolt4 purified iron single crystals to a total carbon, oxygen, and nitrogen content of approximately 20 ppm. They observed a lowering of the yield stress with this increased purity, and thus one might have expected an observation of increased ductility. Although they tested specimens of orientations which the previous workers had indicated should be ductile, the crystals failed at a 78°K in a brittle manner with little elongation. Stein noted,' however, that about 90 pet of the failures could be traced in origin to occluded grains. Allen et al.1 and Edmondson3 do not report examination of their cleavage surfaces, but Biggs and pratt2 reported that microscopic examination of the cleavage surfaces of many of their specimens revealed the presence of small occluded grains. Honda and cohen6 and Keh7 have also observed the initiation of fracture at occluded grains in iron single crystals. Therefore, the additional complication of occluded grains must be considered in studying the properties of iron single crystals and the origin of fractures determined if the ductility exhibited by the crystals is to be considered meaningful. Various investigators8-12 have studied the effects of impurities on grain boundaries in high-purity polycrystalline iron. Rees and Hopkins10 showed that the addition of oxygen to low-carbon (0.002 pet) iron weakened the grain boundaries, causing a shift from transcrystalline to intercrystalline fracture and a progressive decrease on the brittle-fracture stress with increasing oxygen content. In addition, it has been shown by Low and Feustel11 that the addition of carbon to polycrystalline iron containing oxygen eliminated grain boundary brittleness. Thus, oxygen can embrittle grain boundaries in high-purity polycrystalline iron, but the addition of an appropriate amount of carbon can eliminate the oxygen-induced brittleness. The oxygen content (19 ppm) of the iron "single crystals" employed by Stein el al. was large enough to suspect impurity effects at the occluded grain boundaries. Allen et al.1 Biggs and pratt,2 and Edmondson3 may have masked any occluded grain problem in their specimens considering the relatively high carbon levels they employed. stein13 demonstrated that the addition of as little as 0.9 ppm C to previously purified (less than 5 x 10-3 ppm C) "single crystals" would increase the elongation from a few percent to more than 20 pet at 78°K and the fracture was not associated with grade boundary initiation.

Jan 1, 1965

By L. D. van Dyk

The extraction of iron and lead from their oxides with a volatile organic ligand such as acetylacetone in the gas phase offers potential advantages of lower energy consumption, recycling of the extractant, recovery of pure metals, and a reduced environmental impact compared with conventional extraction processes. The influence of reaction temperature, ligand flow rate, and metal oxide levels on the extraction and rates of reaction of iron and lead from single metal oxide (synthetic haematite (Fe2O3) and synthetic massicot (PbO)) systems in a fluidized bed was studied. It was found that at the investigated acetylacetone flow rates, the influence of mass transfer was limited, but that the reaction suffered from reactant starvation. When the metal load increased the effect of starvation on the rate of reaction also increased. The reaction kinetics increased with an increase in temperature for both systems. At low metal oxide concentrations more that 80 per cent of the iron and lead could be extracted from their respective metal oxides after only four hours.

Jan 1, 2012

By L. F. Mondolfo, F. A. Crossley

SURFACE effects in the brittle fracture of materials such as glass and in the plastic slip of zinc and cadmium crystals are well known.' Recently, another surface effect has been found for zinc monocrystals. It has been observed that certain normally ductile zinc monocrystals become ex- tremely brittle when their surface is coated with a layer of oxide or copper plate.

Jan 1, 1952

A new watersoluble binder for mineral ore pellets has been developed by the sulfonation of bituminous materials. A highly effective binder for iron ore pellet making is obtainable from bituminous materials produced in the hightemperature cracking of crude oils. This paper deals with production process and basic properties of this binder as well as new applications in the field of iron ore pelletizing.

Jan 1, 1974

By A. F. Marques

The Azores islands are located on a triple junction where the American, African (AFR), and Euroasian (EUR) plates meet. The Mid-Atlantic Ridge (MAR), oriented N-S, represents two branches of the T; an E-W branch defines the EUR/AFR boundary called the Terceira Rift. The nature and structure of this plate boundary, as well as the dynamics of the interaction of tectonics and volcanism remain unconstrained. The Azores plateau is seated on a mantle domain of anomalously low seismic S-wave velocities, and gravity and geoid anomalies, where the apparent thick crust is thought to relate to larger degrees of melting initiated at greater depths [1]. The cause of these anomalies is controversial but many authors consider the presence of an anomalously hot/wet enriched mantle probably supplied by a plume [2]. The geochemistry of the subaerial and most submarine lavas from the plateau reinforces the plume model beneath the Azores [3-4]. The origin, size and present location of the plume is under debate but an area near Terceira is the favoured plume centre [5]. [ ] SEAFLOOR HYDROTHERMAL SYSTEMS IN THE AZORES AREA (36ºN ? 40ºN) More than 150 active and fossil hydrothermal systems are known in the oceanic seafloor [6]. Many more are yet to be found on vast oceanic areas that haven?t been explored [7]. Ever increasing knowledge shows that modern seafloor hydrothermal systems can be hosted in felsic to ultramafic rocks, vary in size and shape and exhibit diverse amounts of sediment cover

Jan 1, 2011

Partition models are commonly used to assess the separation performance of circuits incorporating density-based processes. Unfortunately, this useful tool has traditionally been overlooked by the heavy minerals sands industry due to difficulties associated with the use of toxic dense liquids. In the present study, this problem has been avoided via the development of partition models based on experimental data from microscopic grain-counts. This technique, which uses different mineral species as density tracers, provides a new tool for evaluating the multi-stage circuits that are required to successfully upgrade heavy mineral sands. The partition model approach easily identifies shortcomings of existing circuits and, when used with conjunction with linear circuit analysis, provides tremendous insight regarding the optimum arrangement of unit operations in terms of separation efficiency and plant throughput capacity. An industrial case involving the redesign of a heavy mineral sand spiral plant is presented to demonstrate the utility of these process engineering tools in plant optimization.

Jan 1, 2009

By C. V. Deutsch, J. B. Boisvert, J. L. Deutsch

Data used to build geostatistical models come from a wide variety of sources with potentially differing sample errors and volume supports. Typically all available sample measurements are pooled together for statistical analysis irrespective of the quality of the data. The sample data is used to assess spatial continuity, make local estimates and assess uncertainty. A new methodology is proposed to simplify accounting for samples of differing quality. The result is improved estimates with higher weights assigned to high-quality samples, while low-quality samples receive less influence in resource estimation. A new dimension, d, is introduced and calibrated to account for sample error and/or volume during estimation. The addition of an extra dimension can be easily incorporated in existing kriging or inverse distance workflows. The only additional parameters required are the sample error and volume for each datum. The methodology is demonstrated and the improvement in local accuracy is documented. Extending the dimensionality of the domain to four (three spatial dimensions and the additional d dimension) requires a valid 4D variogram model; therefore, the spherical variogram model is generalized to arbitrary n-dimensions.

Jan 1, 2011

By Tuncel M. Yegulalp, Peter G. Zambas

In planning an underground room-and-pillar mine, the selection of the shaft or portal location and the orientation of the main haulage arteries is of paramount importance, particularly in view of the high dependence of the cost of truck haulage on the proper definition of these parameters. In an effort to facilitate this selection a computer program was written which, by relating the truck characteristics to the areal configuration of the property or ore body, derives the volume-weighted total fuel and time requirements for hauling ore from every panel within the property to a specified portal or shaft location through a predetermined gridwork of haulage drifts. By varying the size and orientation of the gridwork and the location of the portal or shaft access, an infinite number of configurations can be investigated. The results of this analysis can be plotted to indicate the optimum conditions.

Jan 1, 1974

By N. E. Rogen, N. J. Grant

WHILE direct measurements of the growth of precipitate particles during aging is of fundamental value, few such measurements have been made. Direct measurements by means of optical or electron-microscopy and X-ray techniques are preferred, however, many of the aging studies have been based on indirect methods such as electrical resistivity and hardness. Because of the minute size of most precipitate particles (less than 1000A) the light microscope is of limited use while electron microscopy is subject to slowness, etching problems and consequent resolution problems. It is fortunate that alloys of the Nimonic type, based on Ni-Cr-Ti-Al, lend themselves to accurate and relatively easy particle size measurements. With proper balance of titanium and aluminum, the only aging precipitate is the gamma prime (r') Ni3,(Al, Ti)2 phase and this phase is the basis of the high-temperature strength of these allos.3-6 The Ni3(Al, Ti) phase is a face-centered-cubic, ordered structure with nickel atoms occupying the cube faces. Titanium atoms can replace three out of every five aluminum atoms and when substituting do so preferentially.2 Electron microscopy has shown that during aging of most of the commercial alloys of this type, precipitate particles are unusually uniform in size and distribution, and that the volume of (r') phase is large (20 pct).4,7 The aim of this investigation was to measure the growth of (y') phase during aging. In so doing, it was hoped that a clearer understanding of the aging process would be attained. X-ray line broadening was used as the measure of precipitate particle size. This technique was selected because it can measure and average the diameter of thousands of particles in one operation. The variations in hardness and matrix lattice parameter with aging were also studied and related to the particle size. EXPERIMENTAL PROCEDURE An alloy of the following composition was studied: Cr Ti A1 C Ni Wt pct 20.71 2.98 1.43 0.04 bal. At. pct 22.06 3.47 2.95 0.18 bal. The alloy, a 15- lb vacuum melt, was forged to 1/2-in. diam at a temperature of 1900" to 2200°F; was solution heat treated for 4 hr at 2000°F and water quenched; and was then aged in various ways. The ASTM grain size was 4 to 5. No (7') phase could be detected by X-ray analysis after solution treatment and electrolytic extraction. Aging was performed on 2-in. long specimens at 1400°, 1500°, and 1600°F for increasing times. One-half inch sections were removed after each time increment and were then electropolished in a solution of H3P04 saturated with chromium trioxide at a potential of 30 v and rectified with a tantalum electrode. Rockwell hardness measurements were taken using one side of the polished specimen. Matrix lattice parameter determinations were made on the other side using filtered chromium radiation references with the position of the (220) line of a silicon standard. To enable the precipitate particles of the (y') phase to be measured using X-ray line broadening techniques, it is first necessary to separate and concentrate this phase by electrolytic extraction. Extraction is necessary because the difference between matrix and precipitate lattice parameters is only approximately 0.5 pct and intensities of.the (y') phase lines are very weak relative to those of the matrix. The extraction techniques employed have been described before and found to produce a reasonably quantitative separation.398 A water solution of 15 pct H3Po4 is used at a current density of 0.5 amp per sq in. at 6 v. The precipitate particles are separated from the liquor by centrifuging and decanting and are then washed, dried and repowdered. A plot of the X-ray intensity vs diffraction angle for the (111) line of the precipitate particles was used as a measure of particle size. The intensity curve approximated the shape of Gaussian distribution function and its breadth was measured at the half height. The (220) line of a silicon standard was used to correct the measured line breadth for instrumental and other broadening errors. The Scherrer formula was used to calculate particle

Jan 1, 1961

By W G. Rowley

The Fortescue Metals Group story began in 2003 with a vision to establish an infrastructure project that would connect the stranded iron ore deposits of the Pilbara region of Western Australia with the steel mills of Asia. Following exploration successes in the Chichester Ranges using their new exploration model, Fortescue established significant iron ore resources at Cloudbreak and Christmas Creek during 2004 and 2005. By May 2006 the definitive feasibility study for mine, rail and port was completed, many of the key government approvals had been obtained, product development and market acceptance were complete and 1.07 Bt of total proved plus probable iron ore reserves were defined to support a 20 year mine life from the Cloudbreak and Christmas Creek deposits. Project construction commenced in September 2006 following a successful $3.2 billion capital raising. By April 2008, the mine and processing plant at Cloudbreak were completed along with the Herb Elliott port facility at Port Hedland and 256 km of heavy haul railroad linking the mine with the port. Mining of overburden commenced at Cloudbreak in late 2007 and by 15 May 2008 the first shipment of iron ore had departed for China. In the first 12 months of operation total shipments amounted to 24.6 M wet metric tonnes with weighted mean composition of 58.9 per cent Fe (64.4 per cent Fe calcined), 4.3 per cent SiO2, 2.0 per cent Al2O3 and 0.047 per cent P. Exactly 3.5 years between the Cloudbreak discovery hole and commercial production. The project success depended on many technical breakthroughs including a new exploration model, application of the surface miner as the main mining production unit, design of a new marketable fines product called æRocket FinesÆ, a highly efficient ædesandÆ flow sheet for upgrading of 2.4 per cent alumina run-of-mine to 1.9 per cent alumina Rocket Fines, 40 t axle loads for the heavy haul railway and a high capacity-highly automated port facility.

Jan 1, 2009

By B. C. H. Steele, C. B. Alcock

In choosing solid oxide electrolytes for use in the measurement of thermodynamic quantities at high temperatures, the two most important criteria are the values of the partial ionic and electronic conduc tizities. Measurements of these conducticities have been made for some Group IVA oxides and solid solutions of these oxides with CaO, Y2O3, and La2O3. The total conductivities as a function of temperature. oxygen partial pressure, and composition were determined, as well as the electromotive forces of cells in which the oxygen partial Pressures of the electrodes were between 10-7 and 10-29 atm at 1000°C. Additional factors that influence the experimental arrangements, such as the operating temperature, the appropviate cell atmosphere, and electrode kinetics, are also discussed. IT has long been recognized that galvanic cells incorporating solid electrolytes can possess many advantages for the measurement of high-temperature thermodynamic data. Unfortunately, the electrical-transport properties have only been established for a few solid electrolytes, although attempts have been made, and are still being made, to use such materials as porcelain' and magnesia.' Kuikkola and Wagner have discussed3 and demonstrated4 various applications of solid electrolytes, and, in particular, their work stimulated the electrochemical measurement of oxygen activities using cells incorporating the solid oxide electrolyte, Zr0.85Ca0.15O1.85 The excellent characteristics of this oxide electrolyte have been confirmed by the investigations of Kingery et al.5 (oxygen ion diffusion), Carter and Rhodes6 (zirconium and calcium ion diffusion), and Weissbart and Ruka7 (electronic transference number). However the observations of Peters and Mobius,8 later confirmed by Schmalzried,9 indicated that the electronic component of zirconia-based electrolytes could become significant at low oxygen chemical potentials. Under these conditions, thoria-based electrolytes have obvious advantages arising from their superior thermodynamic stability. It was known that certain thoria solid solutions possessed defect fluorite structures containing anionic vacancies (cf. Zro.85Cao.l50O1. 85), although data on their electrical properties were conflicting. Kiukkola and wagner4 concluded that thoria-based electrolytes exhibited appreciable electronic conductivity, whereas Peters and Mobius8 mentioned that the electronic conductivity only became important at high oxygen partial pressures, but gave no further details. In addition, both Kiukkola and wagner4 and Peters and Mann'" had determined the oxygen chemical potentials associated with the Fe-FeO, Co-COO, Ni-NiO, and Cu-Cu2O equilibria, and it was not known whether discrepancies in their results could be attributed to the different cell design, or the thoria-based electrolyte used by Peters and Mann. These uncertainties have been resolved during the present investigation into the measurement of low oxygen chemical potentials, and transport properties of the relevant oxide electrolytes are presented and discussed. Other experimental difficulties associated with low oxygen chemical potential measurements are also described, with particular reference to the Nb-O system. 1. THEORETICAL CONSIDERATIONS Oxide systems of potential use as solid electrolytes possess a large energy gap between the valence and conduction bands. Little is known about the defects present in these wide-gap metal oxides as a function of impurity content and deviations from stoichiom-etry, or the mechanisms by which electronic charges move in these solids. For these materials it is convenient to represent the measured conductivity as the the sum of three terms: where a, is the conductivity due to positive hole conduction (p type), and oe is the electronic conductivity due to electron conduction (n type). U there is a large concentration of ionic vacancies fixed by composition then the ionic contribution will not be a function of oxygen pressure. Although the possibility of a pressure-independent electronic component also cannot be ignored, it is likely that such a term would only become significant at very high temperatures, and in general the positive hole conduction will increase with increasing oxygen pressure, and the electron conduction will increase with decreasing oxygen pressure. It follows that the total conductivity is related to oxygen partial pressure as follows:

Jan 1, 1965

By P. G. Kovalchik

Recent research conducted by NIOSH, Pittsburgh Research Laboratory showed that electrical current levels permitted under present regulations may not limit cable temperatures to less than 90°C in reeled trailing cables. Reeled cables, tightly wrapped with many turns, all carrying current in an enclosed space, can become overheated due to poor heat transfer. This overheating can cause the cable insulation to soften and become easily damaged. The damaged insulation reduces the life of the cable and can lead to shock, electrocution, and mine fires. This paper describes a method of measuring the conductor temperature of mine trailing cables during normal operation. The temperature is measured using a 50/125 micrometer Graded Index Multimode Optical Fiber located in the center of the metallic conductors. Distributed temperature measurements are made using an Optical Time Domain Reflectometer (OTDR). This system is capable of measuring temperature with an accuracy of plus or minus one degree centigrade over a length of 4 km at 1-m intervals. With this unique way of measuring temperature, tests can be conducted simulating actual mine conditions and provide important data to allow MSHA's Approval and Certification Center to develop approval criteria for cyclically rated reeled machines.

Jan 1, 1998

By Burnham E. Field

The chemical industry is constantly looking for new materials which either are more resistant to corrosion than those now available or have improved physical properties to meet the requirements of higher temperatures and greater pressures. Attack by acids is one of the more important forms of corrosion and in the last few years the development of acid-resistant alloys has been quite rapid. Perhaps the most notable example is that of nitric acid, the problem of which has largely been solved by the chromium-iron and chromium-iron-nickel alloys. Sulfuric acid may be handled in lead, iron, or the iron-silicon alloys, depending on conditions. As to hydrochloric acid, no metal or alloy can be called entirely satisfactory for handling this acid under plant conditions.' The results of our investigations on the resistance of the nickel-molybdenum alloys to hydrochloric acid have been confirmed by those of Guertler, Rohn, Schulz, Jenge, and others12 but thus far only one such alloy has approached commercial production in Germany; this contains approximately 15 per cent. chromium and 7 per cent. molybdenum with the remainder chiefly nickel. Dr. S. W. Parr, as far back as 1914, developed a complex alloy known as "illium," with a nickel base and containing some molybdenum. 3 Dr. Parr was primarily interested in an alloy for lining bomb calorimeters, and while illium does show good resistance to acid it is too expensive for general use. Two United States

Jan 1, 1929

By Burnham E. Field

The chemical industry is constantly looking for new materials which either are more resistant to corrosion than those now available or have improved physical properties to meet the requirements of higher temperatures and greater pressures. Attack by acids is one of the more important forms of corrosion and in the last few years the development of acid-resistant alloys has been quite rapid. Perhaps the most notable example is that of nitric acid, the problem of which has largely been solved by the chromium-iron and chromium-iron-nickel alloys. Sulfuric acid may be handled in lead, iron, or the iron-silicon alloys, depending on conditions. As to hydrochloric acid, no metal or alloy can be called entirely satisfactory for handling this acid under plant conditions.' The results of our investigations on the resistance of the nickel-molybdenum alloys to hydrochloric acid have been confirmed by those of Guertler, Rohn, Schulz, Jenge, and others12 but thus far only one such alloy has approached commercial production in Germany; this contains approximately 15 per cent. chromium and 7 per cent. molybdenum with the remainder chiefly nickel. Dr. S. W. Parr, as far back as 1914, developed a complex alloy known as "illium," with a nickel base and containing some molybdenum. 3 Dr. Parr was primarily interested in an alloy for lining bomb calorimeters, and while illium does show good resistance to acid it is too expensive for general use. Two United States

Jan 1, 1929

By S T. Jarvis

Colliery spoil is the major constituent of colliery spoil ærockpasteÆ which has been used to infill abandoned limestone mines in the West Midlands of England since the early-1980s. The other constituents of rockpaste are pulverised fuel ash, lime and water. A key property of the rockpaste is its ability to flow within the mine workings over considerable distances before setting. This paper describes the work carried out to identify suitable sites as sources of colliery spoil for making rockpaste and goes onto consider the flow properties of the material and the monitoring methods used on-site. A full-scale trial comprising infilling a 6600 m3 section of an abandoned mine was conducted prior to the infilling of the Littleton Street Mine which had a volume of about 500 000 m3. As well as describing the methods used for monitoring the movement of rockpaste material, a description is also given of a dip-meter developed specifically for the purpose of measuring the level of paste in the mine. This paper shows how a colliery spoil based paste has been successfully used for infilling abandoned mine workings. The monitoring systems developed for use in the two case studies presented in this paper are now being used extensively for infilling other abandoned mine workings. To-date over 11 mines with a total volume exceeding two million cubic metres have been backfilled.

Jan 1, 1998

A new classification of subduction related (epithermal- / mesother-mal) gold mineralisation styles based on the tectonic framework they occur in, has been found helpful in practice. It offers a ratio-nalisation of exploration efforts during all stages of work.Methodology on the ground during first pass- and follow up explo-ration which has been found effective for the various mineralisa-tion styles is being briefly outlined.

Jan 1, 1990

By Y. Nan

A new computer simulation model for the analysis of underground coal mine production systems in the Peoples Republic of China is presented. As a case study the model was used to analyse the railway system of an existing underground coal mine. Some results of this first application are given in this paper and some conclusions of common interest for underground rail haulage systems are discussed.

Jan 1, 1986

By Robert F. Kehrman

As with many new technologies, the rapid growth in solution mining for uranium has created uncertainties regarding the environmental impact of mining operations. In solution mining, the largest area of concern is the impact of the process on the quality of ground water supplies. As a result, a rapid and reliable technique of detecting lixiviant excursions is desirable. Such a method would replace the periodic sampling technique and should provide a more or less continuous monitoring method. To this end, resistivity techniques were evaluated as an alternate means of tracking lixiviant movement. A program was devised which had five specific tasks. These were: (1) evaluation of the techniques, (2) development of the most promising technique or techniques, (3) field testing of the techniques, (4) testing of the BuMines probe, and (5) reporting. The result of the analytical and field work is that various resistivity/ resistance techniques do provide a means of detecting lixiviant movement in Northern Wyoming. Surface and downhole galvanic surveys and controlled source audio magnetotellurics (AMT) were evaluated. All three techniques showed some degree of success.

Jan 1, 1979

By John G. Tate, George W. Nicolson, James L. Bruce

For more than 25 years modern mining has been carried on in the Island of Cyprus, Mediterranean Sea, by the Cyprus Mines Corp. of Los Angeles, Calif. The general features of these operations have been described.' From 1935 to June 30, 1940, top slicing in the Mavrovouni mine produced in excess of 2,000,000 long tons. The rate for the last part of this period was approximately 50,000 tons per month. Description of Ore Bodies The shape Of the Ore body now being top sliced in the Mavrovouni mine is an inclined irregular pyritic pipe or chimney of large dimensions) extending from unknown depths below the bottom level at elevation 250 ft below sea level) to the highest level at elevation 400 ft above sea level. The present surface above the ore body lies between 550 and 650 ft elevation. Undoubtedly the Ore body extended to surface and was Mined by the ancients by opencast and underground methods. The old pits were gradually filled up by erosion until now they show as slight depressions in the topography. The largest area of the Ore body is at elevation 170 ft below sea level, where the horizontal section is almost elliptical, with a width of 600 ft and a length of 1000 ft. Below this elevation the shape of the ore body continues to be elliptical but with reduced dimensions. Above this elevation it rises flatly towards the south with a substantial depression in the upper-side of the chimney and irregular ridges or wings rising on each side. It gradually grows smaller as it rises. The ore body is a pyritic replacement of andesitic extrusives which occur as flows and pillow lavas. With the exception of the upper portions of one or two small offshoots rising from the main ore body, all ore is completely surrounded by andesite. Most of the andesite lying above the ore body is covered by marl and Clay sedimentaries of Miocene and later age, The Miocene is presumed to be older than the ore mineralization. That portion of the andesites which lies between the sedimentaries and the ore body has been broken by slumpage, and weathered, and iron-Stained by the descending meteoric waters, It is a mass of crushed material that caves and follows downward readily as the top-slice stopes retreat. The main ore body is a heavy cupreous pyrites mass assaying on the average about 4.0 pet Cu; 48.0, S; and 42.0, Fe. In places the copper drops below 1.0 pet. on the borders of this heavy sulphide ore body lie disseminated cupreous pyrites ore deposits of large dimensions. some portions of these appear to be closely related to the heavy sulphide ore, as the ratio of copper to pyrite is about the same. The greater part of the disseminated ore, most of which lies immediately to the east of the main Ore body, contains less than 0.10 pct Cu and about 25.0 to 30.0 pct S. 'This probably can

Jan 1, 1949