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By Lloyd A. Morley

A concept is presented to improve underground coal mine electrical system safety and availability. This proposed technique is based upon the ability to predict incipient failures in the mine power system. Prediction is made possible by a new method, developed during this research, which uses a minicomputer to implement pattern recognition algorithms. The theoretical basis of the prediction system is discussed, along with synthesis of the hardware and software sections. The deterioration modes which could be detected are examined, and an evaluation of the system's ability to predict incipient failure is presented. Typical results of the system's performance during laboratory simulation of power system deterioration are given.

Jan 1, 1977

Strata bolting/dowelling reinforcement techniques are being reintroduced into the mines of the National Coal Board. There are strong reasons for the selection of the full hole anchorage principle of bolting and for the development of the wood/resin dowel. There are strong reasons also for the measurement of strata bed separation as the method of assessing the effectiveness of a roof bolting system. There are several designs of bolts. Instruments have been developed for investigation and control purposes. Different drilling and bolting machines have been employed in trial sites. In addition comparative laboratory model work has been conducted on simple non-bolted and bolted systems.

Jan 1, 1971

By I M. Platten, C J. S Sangster, Y Xie, S C. Dominy

Cononish is a steep, narrow NE-SW trending vein system that was emplaced into late Proterozoic metasediments. It shows brittle style deformation and postdates metamorphism and associated Caledonian foliations. The ore shoots plunge 45¦SW, have a 40 to 80?m intersection with the existing underground development and extend between 40 and 260?m down plunge. Small-scale sulfide-bearing domains within the vein carry the highest gold grades. They collectively define the ore shoots, where one or two and rarely three of the domains are present at an individual site in the vein. Gold occurs as electrum, with minor native gold. Silver occurs additionally as tellurides and native metal. The gold/electrum is fine-grained, generally <100?¦m in size and locally clusters. Visible gold up to 2000?¦m in size is rare. Gold and silver are generally spatially associated with sulfides in quartz. The main sulfide is pyrite, but galena, chalcopyrite and sphalerite occur also. Electrum and gold occur with galena in pyrite-hosted fractures. Gold is also associated with the contacts between galena and pyrite grains. Discontinuity of individual domains, variation in domain thickness and internal heterogeneity results in short scale variation in grade across the structure. Over 16?km of diamond drilling and a 1.2?km exploration adit has provided data to support a Mineral Resource estimate of 169?000?oz Au and 631?000?oz Ag reported in accordance with the 2004 JORC Code.CITATION:Dominy, S C, Platten, I M, Xie, Y and Sangster, C J S, 2013. Gold-silver vein mineralisation at Cononish, Scotland, in Proceedings World Gold 2013 , pp 445-454 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By P Campi, M Dodds

The EastLink project is a 39 km tollway to the east of Melbourne and includes twin three-lane 1.5 km driven tunnels. The hard rock tunnels are being built to avoid passing the motorway through the Mullum Mullum Valley to help preserve the unique flora and fauna in the area. This paper describes the process of transferring the support requirements from the ædrawing boardÆ to the tunnelling face by integrating the temporary support design with the contractorÆs tunnel excavation and support procedures, including sharing of responsibility between the designer and contractor for selection of the support type and the production of a project specific rock mass classification system to enable more objective determination of ground conditions. The methods developed during the design phase incorporated a formal system of reviews, support selection and feedback by monitoring tunnel and ground responses. During construction, the process was implemented using a set of simple documentation and regular structured communication between the contractor and the designer.  

Jan 1, 2008

By Marke Wong

? Vietnam?s economy is growing so fast that gross domestic product (GDP) growth remained above 8% in 2005 and exports are rising steadily at 25% per year. ? Demand for electricity is expected to increase 18% per year through 2010 requiring an additional estimated 7,547 MW before 2010 ? Domestic coal demand is expected to be over 45 Mt by 2010. ? The Quang Ninhcoal deposits are estimated at 6.5-7 billion tons (350m) Vietnam News Agency. Saturday, May, 6, 2006. ? National resources are now estimated at 10 billion tonnes; not including a relative new coal bed discovery estimated at 210 billion tonnesin the Red River Basin.

May 1, 2006

By C. A. Sutherland

"Smelting of copper-gold ore from nearby Rossland mines started at Trail in the 1890s. As ore from the Rossland mines became exhausted, lead smelting of hand-sorted galena ore from other British Columbia mines was initiated. With the development of flotation technology for the separation of lead, zinc, and iron sulphides in the first two decades of this century, the large Sullivan orebody at Kimberley, British Columbia, became the f oundation for the growth of a major zinc and lead smelter at Trail. Lead smelting began in 1901, electrolytic zinc in 1916, and by 1984, the Trail metallurgical complex had produced 10 million tons of each metal. Its present capacity is 270000 tonnes per year of zinc and 110 000 tonnes/year of lead.This paper reviews the history of technological changes in the Trail production plants, emphasizing the zinc plant modernization program started in the 1970s, and also the planned introduction of the QSL oxygen lead smelting process in the late 1980s. Lead modernization will increase production capacity to a maximum of 160000 tonnes per year.IntroductionCopper-gold ore was discovered at Rossland, British Columbia, in the year 1890, starting a mining industry that was to last over three decade s. Selected ore was at first transported at high cost to distant U.S. smelters, so there naturally followed a decision to construct a small copper smelter to process the local ore to matte. It was built in 1896 at the mouth of Trail Creek on the Columbia River, about 10 km from Rossland. This little smelter was to develop and diversify in the next 90 years into the world 's largest lead-zinc producer).The mining boom that occurred in the northwestern United States and southeastern British Columbia in the period of 1890 to 1910 saw the brief operation of many small local smelters. The only one to survive was the smelter at Trail. The circumstances that permitted its continued life and subsequent growth, form a fascinating history of business deals, litigation, andsteady technical progress.Early investment in local railway transportation and options by F.A. Heinze, the smelter' s founder, attracted the attention of the Canadian Pacific Railway Company, which purchased Heinze' s assets in 1898. This provided the capital base for survival and growth of the smelter, which remained and prospered under the Canadian Pacific umbrella for almost ninety years. It was registered as the Consolidated Mining and Smelting Company of Canada Limited in 1906; in 1966, this name wasshortened to Cominco Ltd.The Rossland mines continued to supply copper ore for the smelter until the late 1920s, but lead-silver ore also became available from the contemporary mining boom in the Slocan area, about 80 km away. In 1901, the Trail smelter diversified into lead; and when the CM&S Co. acquired the St. Eugene Mine at Moyie and the Sullivan Mine at Kimberley, the smelter was guaranteed a firm supply of lead ore. The company also purchased the West Kootenay Power and Light Company, which even before the turn of the century had constructed the first of four hydroelectric generating plants on the Kootenay River near Trail. This acquisition assured the CM&S smelter and its local mines of a stable power supply and the opportunity to diversify into power intensive technology."

Jan 1, 1988

By Florian Häckel, Ulrich Schwarz-Schampera, Benjamin Bühring, Katja Schmidt, Dieter Garbe-Schönberg, KoschinskyM Andrea

"The Vanuatu island arc and its adjacent back-arc basins form part of the southern New Hebrides subduction system in the southwestern Pacific Ocean within a triangle defined by the Solomon Islands, New Caledonia and Fiji (Meffre & Crawford 2001). The back-arc region east of the volcanic front is characterized by three structural depressions namely Vate, Erromango, and Futuna (from N to S), also known as the Coriolis Troughs. Earlier studies of lava compositions reveal the occurrence of highly evolved alkali-rich dacites as well as ankaramite basalts within the individual troughs (McConachy et al. 2005).Here we present the first mineralogical and geochemical analyses of hydrothermal fluids and precipitates (sulfides, sulfates, Fe-oxyhydroxides), sediments, and volcanic rocks, sampled during the "Coriolis Volcanism and Vents" (COVOLVE) cruise SO229 in July 2013 aboard the German R/V Sonne. The samples were retrieved during several ROV Kiel 6000 dives directly from the newly discovered active vent sites at the neovolcanic Nifonea Ridge, and from multiple sites at water depths ranging between 200 to 2800 m within the Vate and Futuna Troughs as well as from the shallow water Epi Caldera NNE of the Coriolis Troughs (Fig. 1)."

Sep 1, 2014

On-line radioisotope gauges determine information on the characteristics of ore to enable improved control of processing operations. In the metalliferous mineral industry, in-stream analysis systems based on radioisotope X-ray techniques determine concentrations of valuable minerals at various stages of the concentration process. In the coal industry, on-line gauges determine ash and moisture contents, and the specific energy of coal.In-stream analysis systems developed in Australia are installed in about 30 mineral concentrators. Their use has led to the increased recovery of valuable minerals, and the time taken to recover the cost of installation is usually several months. The savings to Australia resulting from use of these analysis systems is estimated to be more than $A 15 million per year.Australian experience in the training of mineral industry personnel shows that the most effective approach is to combine courses on nuclear techniques and control of processing operations. This is the basis of Australia's contribution to the minerals sub-project of the United Nations Development Program (UNDP) Industrial Project.

Jan 1, 1985

By John Ralston, Jona Addai-Mensah, Patience Mpofu

The flocculation and dewatering behaviour of kaolinite (non swelling) and smectite (swelling) clay dispersions has been investigated using hydrolysable metal ions Mn(II) and Ca(II) and anionic polyacrylamide-acrylate copolymer (PAM) at pH 7.5 and 10.5. A pH-dependent, specific metal ion adsorption behaviour, accompanied by a marked reduction in particle zeta potential and slurry shear yield stress, was observed to have a profound influence on the colloid stability of both types of clays. Due to the differences in the cation exchange capacity, the smectite clay dispersion required a higher amount of metal ions than kaolinite dispersion to produce similar effects. The adsorption density of the anionic PAM at the negatively charged clay particle surfaces correlated well with metal ion hydrolysis and adsorption behaviour, all of which had a strong effect on slurry settling rate and extent of consolidation. At pH 7.5 where Mn(II) ions hydrolyse, metal ion and flocculant adsorption densities were both greater in the presence of Mn(II) than Ca(II) ions. At pH 10.5, however, where Ca(II) ions begins to hydrolyse, higher adsorption densities were observed for Ca(II) ions in comparison with Mn(II) ions, as the latter hydrolysed completely and precipitated. The metal ion mediated flocculant adsorption led to improved hydrogen bond driven particle bridging and facilitated charge neutralisation flocculation mechanisms which significantly enhanced the dewaterability of both clay dispersions.

Jan 1, 2003

By D Wyborn, P A. Dowd

The characterisation of rock fracture networks is an important component of rock engineering applications involving stability assessment or fluid flow analysis. However, the derivation of a reliable rock fracture model remains a very challenging problem in practice. This paper describes a Bayesian framework, in the form of Markov Chain Monte Carlo (MCMC) simulation, for the construction of such a model. Model conditioning using different data sources is discussed including seismic events recorded during hydraulic fracture stimulation, rock face fracture mapping data and downhole geophysical survey data. The freeware FracSim3D is used for the simulations.

Sep 26, 2011

By K. Park

Coupled influence of sulphidizers and xanthates on the electrokinetic property and flotation behavior of malachite was systematically examined via electrophoretic mobility measurements and microflotation tests. The electrophoretic mobility results for the malachite before and after surface modification with different types (Na2S and (NH4)2S) and amounts (1×10-7?1×10-4 moles/g) of sulphidizers, showed that the isoelectric points (IEP) of malachite differed at the low dosage level depending on the type of the sulphidizer, which ranged between 5 and 9.5. However, the IEP values were observed to be shifted from high to low pH values with increasing amount of sulphidizers and finally ranged between 3 and 4, indicating that the sulphidizers played a different role on changing the surface property of malachite. In order to further understand the effect of sulphidizers on the electrokinetic property and flotation behavior of malachite in a sulphidizer+xanthate system, flotation tests were carried out with malachite sulphidized with Na2S and (NH4)2S (adsorptive amount=8×10-5 moles/g) at different bulk xanthate concentrations. The results showed that the flotability of (NH4)2S-treated malachite was greater than Na2S-treated one over the entire xanthate concentration investigated, indicating that the type of sulphidizers played important role in malachite flotation; however, no obvious correlation between electrokinetic property and flotability of malachite was observed.

Feb 27, 2013

By R. E. Brewer

Phelps Dodge Mining Company (Phelps Dodge) is operating a pressure leach vessel (PLV) for copper concentrates at the Bagdad Mine facility in Arizona. This single PLV unit was engineered and constructed based on continuous laboratory testing, reaction chemistry and kinetics, and available pressure vessel technology. The challenge of designing for optimum process retention time, agitation, oxygen mass transfer, temperature and pressure will be reviewed in this paper. The PLV interior lining, agitation equipment and compartment configuration chosen for the PLV will also be reviewed.

Jan 1, 2004

By D. C. Andersen, G. L. Smith, A. M. Marsh, J. Pearson-Taylor

Central to the success of any mining company is the ability to manage capital investment effectively so as to ensure acceptable stakeholder returns within an overall strategic context. Critical to this process is the effective selection and implementation of a strategically aligned project portfolio that enables optimal resource exploitation while operating within mandated bounds and identified constraints. Consideration is given to the strategic long-term planning process, an investment prioritization methodology and specific tools and techniques based on the discounted cash flow philosophy.

Jan 1, 2006

By Claude Hubert, Robert Sansfaçon

"The Malartic gold camp includes the Malartic Gold Fields, Barnat, East-Malartic, Canadian Malartic and Sladen mines. From 1935 to 1984, these mines have yielded 212 403 kg of gold. They occur within a 900 m wide belt of highly sheared, dislocated and faulted volcanic and sedimentary rocks (Piché and part of the Pontiac groups) herein named the Malartic Tectonic Znne (MTZ). The zone trends WNW-ESE and separates two lithotectonic sedimentary domains, the Cadillac to the north and the Pontiac to the south. The sedimentary domains are characterized by their coherent fold generations consisting of open to tight reclined and recumbent F1 folds that have been refolded into series of asymmetric upright F2 folds. A flat-lying schistosity (S1 ) and a vertical pressure-solution cleavage (S2) are ubiquitous throughout. Discrete sets of brittle and brittleductile faults are synchronous and parallel to each of these two fabrics.The MTZ trends N320° in the northwestern sector of the town of Malartie, changing to N2800 at its easternmost extremity. The Malartie and Sladen faults constitute its northern and southern boundaries respectively. These two faults also bound another set of faults oriented N305°. Throughout the MTZ, the faults at N280° and N320° and those at N305° outline a series of anastomosed motifs that constitute the principal structural feature of the Malartic district. Locally, a fourth set of minor faults at N065° combines with the other three prominent sets. All these faults have disrupted the gold-bearing volcanic, sedimentary and intrusive rocks encountered throughout the MTZ.The MTZ comprises numerous lozenge-shaped blocks of komatiites and basalts or greywackes and black shales which are cut by disjointed dikes, sills and small intrusions of felsic and mafic rocks. The latter includes gabbro, diorite, lamprophyre, monzonite and pegmatite. They frequently fill conjugate sets of fractures. In some areas, they are clustered into coalescent intrusions. The present morphology of these intrusive bodies( cube, chocolate-tablet boudin, parallel epiped and cigar) is not representative of their primary forms but the result of late shearing and faulting indicative of a major tectonic event subsequent to their emplacement. The intrusions were injected during a brittle stage of deformation related to the F1 folding but prior to the development of the F2 folds and subsequent tearing and shearing by late brittle and brittle-ductile faults . The ultramafic and mafic rocks are intensely altered to serpentine, tremolite, actinolite, carbonate, biotite, hematite and pyrite according to the nature of their proto/it h. In the vicinity of the MTZ, all lithologies exhibit mineral assemblages indicative of the upper greenschist or lower amphibolite facies of metamorphism.The structural evolution of the MTZ involved superimposed folding, shearing, transposition, mylonitization, brittle and brittle-ductile faulting. Each lenticular motif results from the combined effect of conjugate sets of shear zones that outline lozenge-shaped blocks where strain markers indicate different strain states from cores to margins. Bedding in ultramafic flows and/or sedimentary rocks is either NW-SE or NE-SW within the blocks but, in the vicinity of the Malartie and S laden faults, it has been rotated to become subparallel to the faults.Ore shoots are most commonly associated with altered and deformed bodies of diorite and monzonite, or some mafic and ultramafic schists and, at the Canadian Malartic, Sladen and East Malartic mines, with metasedimentary rocks. The shoots occur in close proximity to the various faults of the MTZ but the gold itself is intimately associated with pyrite, biotite and carbonate in halos bordering fractures crisscrossing the different host rocks. The density of fractures and the width of their altered zones have been significant parameters in the production of economic ore shoots. Grains of gold are visible in some veins of quartz a"

Jan 1, 1990

By John Fulton

The following table shows the shipments from the four Lake Superior iron-ore districts during the year 1887, and their total outputs from their beginning until the close of 1887.* It will be noted that the Menominee district is second in importance in its total output tonnage to the close of the year 1887. These ore deposits are found in jasper-slates and in the horizon between these and their associated clay-slates; in the latter they are true contact-deposits. They are found in this jasper- and clay-slate formation under varied conditions, yet, in all, certain characteristic laws are preserved. The angle of dip varies from 15° to 20°, and up to 85° and even 90°, with the horizon. The ore is rather soft, bluish-black in color, and is a hematite. It varies in thickness from a few inches to one hundred feet, or more. It is mainly "Bessemer" ore, containing 57 to 63 per cent, of metallic iron, and .03 to .07 per cent, of phosphorus. In the mining nomenclature of this range two conditions of the ore-lens are described by the terms "dip" and "pitch." The former is in common use in defining the relation of the ore-plane to the horizon ; the latter indicates the posture of the ore-body as it inclines east or west from its position at the opening of the mine. In the

Jan 1, 1888

By G. M. Schwartz, D. M. Davidson

THE Duluth gabbro outcrops containing sulphides of copper, nickel, and iron are located on both sides of State Highway No. 1 an airline distance of 8.5 miles southeast of Ely in northeastern Minnesota. The region of known sulphide occurrences includes parts of sections 5, T. 61 N., R. 11 W., and parts of sections 25, 26, 32, 33, and 34, T. 62 N., R. 11 W. These sections, given in Fig. 1, are all in Lake County, Minnesota. Part of the area, which lies entirely within the Superior National Forest, is shown on the topographic map of the Ely quadrangle. The original discovery was made in 1948 when a small pit was opened in weathered gabbro rubble for use on a forest access road. A shear zone had caused unusual decomposition in this glaciated area, and the resulting copper stain was noted by Fred S. Childers, Sr., an Ely prospector, who began searching the outcrops along the base of the intrusive. He was joined in further exploration by Roger V. Whiteside of Duluth. In the summer of 1951 a small diamond drill was moved into the area and a hole 188 ft deep was drilled, passing through 11 ft of glacial drift into sulphide-bearing gabbro. This paper is a preliminary report on the geology of the newly discovered ore. The Duluth gabbro is one of the largest known basic intrusives and may be defined as a lopolith.' It extends northeastward from the city of Duluth as a great crescent-shaped mass that intersects the shore of Lake Superior again near Hovland, 130 miles to the northeast, see Fig. 2. The distance around the outside of the crescent is nearly 170 miles. The form of the intrusive is simple at Duluth where it ends abruptly north of the St. Louis River; at the east end, however, the gabbro splits into two elongated, sill-like masses separated mainly by lava flows and characterized by minor irregularities. The outcrop reaches a maximum width in the central part where it is about 30 miles across, and a maximum thickness of about 50,000 ft. It may be significant that the sulphides occur at the base of the thickest part. The lopolith has segregated into rock types ranging from peridotite to granite. The most abundant types are olivine gabbro, gabbro, troctolite, anortho-site, and granite. Of lesser importance quantitatively are peridotite, norite, pyroxenite, magnetite gabbro, and titaniferous magnetite. Grout estimates that two-thirds of the gabbro at Duluth is olivine gabbro. Variations in the percentages of plagio-clase, augite, olivine, and magnetite-ilmenite constitute the only essential differences found among the basic rock types. The predominant mineral is plagioclase, mainly labradorite. Plagioclase and olivine seem to have crystallized early, and the olivine rich rocks, usually troctolite, are found in the lower part. Segregations of titaniferous magnetite are abundant near the base of the gabbro along the eastern part and also occur far above the base. These have recently been described in detail by Grout.' Near the top, segregation has produced a gradation to granite, or "red rock," as it is known locally. This consists of quartz, red feldspar, and hornblende. The red rock forms a zone with a maximum width of nearly 5 miles but is quantitatively unimportant from Duluth northward for 35 miles. In Cook county, where the gabbro splits, each of the two sill-like masses has a red rock top somewhat thicker in proportion to the gabbro below than in the main central mass. The intrusive ranges from coarse to medium in grain size and from granitoid to diabasic in texture. Throughout much of the Duluth gabbro in Minnesota banding and foliation are well developed, as Grout has emphasized.V he bands are mainly a result of variation in the percentage of minerals, as in troctolite with alternating bands high in olivine and in plagioclase. A few bands may consist largely of one mineral, as is true of some segregations of magnetite. Many of the banded rocks show a clearly developed parallelism of platy plagioclase crystals, and both banding and foliation are believed to conform to the floor of the lopolith. Throughout its extent in Minnesota the Duluth gabbro dips east and south toward Lake Superior. It is generally believed to extend beneath Lake Superior and is found as a smaller mass exposed along the north side of the Gogebic district in Wisconsin and Michigan. The dip at and near the base ranges along most of its length from 20 to 40°, but at places the internal banding dips even more steeply. The dip of the upper part is much less, and if it is assumed that the flows along the north shore of Lake Superior are a dependable indication, it does not exceed 15". The formations shown in Table I which are intruded by the gabbro range from Keewatin to Middle Keweenawan in age. They present a significant picture. At the top, the gabbro and its accompanying

Jan 1, 1953

By G. M. Schwartz, D. M. Davidson

THE Duluth gabbro outcrops containing sulphides of copper, nickel, and iron are located on both sides of State Highway No. 1 an airline distance of 8.5 miles southeast of Ely in northeastern Minnesota. The region of known sulphide occurrences includes parts of sections 5, T. 61 N., R. 11 W., and parts of sections 25, 26, 32, 33, and 34, T. 62 N., R. 11 W. These sections, given in Fig. 1, are all in Lake County, Minnesota. Part of the area, which lies entirely within the Superior National Forest, is shown on the topographic map of the Ely quadrangle. The original discovery was made in 1948 when a small pit was opened in weathered gabbro rubble for use on a forest access road. A shear zone had caused unusual decomposition in this glaciated area, and the resulting copper stain was noted by Fred S. Childers, Sr., an Ely prospector, who began searching the outcrops along the base of the intrusive. He was joined in further exploration by Roger V. Whiteside of Duluth. In the summer of 1951 a small diamond drill was moved into the area and a hole 188 ft deep was drilled, passing through 11 ft of glacial drift into sulphide-bearing gabbro. This paper is a preliminary report on the geology of the newly discovered ore. The Duluth gabbro is one of the largest known basic intrusives and may be defined as a lopolith.' It extends northeastward from the city of Duluth as a great crescent-shaped mass that intersects the shore of Lake Superior again near Hovland, 130 miles to the northeast, see Fig. 2. The distance around the outside of the crescent is nearly 170 miles. The form of the intrusive is simple at Duluth where it ends abruptly north of the St. Louis River; at the east end, however, the gabbro splits into two elongated, sill-like masses separated mainly by lava flows and characterized by minor irregularities. The outcrop reaches a maximum width in the central part where it is about 30 miles across, and a maximum thickness of about 50,000 ft. It may be significant that the sulphides occur at the base of the thickest part. The lopolith has segregated into rock types ranging from peridotite to granite. The most abundant types are olivine gabbro, gabbro, troctolite, anortho-site, and granite. Of lesser importance quantitatively are peridotite, norite, pyroxenite, magnetite gabbro, and titaniferous magnetite. Grout estimates that two-thirds of the gabbro at Duluth is olivine gabbro. Variations in the percentages of plagio-clase, augite, olivine, and magnetite-ilmenite constitute the only essential differences found among the basic rock types. The predominant mineral is plagioclase, mainly labradorite. Plagioclase and olivine seem to have crystallized early, and the olivine rich rocks, usually troctolite, are found in the lower part. Segregations of titaniferous magnetite are abundant near the base of the gabbro along the eastern part and also occur far above the base. These have recently been described in detail by Grout.' Near the top, segregation has produced a gradation to granite, or "red rock," as it is known locally. This consists of quartz, red feldspar, and hornblende. The red rock forms a zone with a maximum width of nearly 5 miles but is quantitatively unimportant from Duluth northward for 35 miles. In Cook county, where the gabbro splits, each of the two sill-like masses has a red rock top somewhat thicker in proportion to the gabbro below than in the main central mass. The intrusive ranges from coarse to medium in grain size and from granitoid to diabasic in texture. Throughout much of the Duluth gabbro in Minnesota banding and foliation are well developed, as Grout has emphasized.V he bands are mainly a result of variation in the percentage of minerals, as in troctolite with alternating bands high in olivine and in plagioclase. A few bands may consist largely of one mineral, as is true of some segregations of magnetite. Many of the banded rocks show a clearly developed parallelism of platy plagioclase crystals, and both banding and foliation are believed to conform to the floor of the lopolith. Throughout its extent in Minnesota the Duluth gabbro dips east and south toward Lake Superior. It is generally believed to extend beneath Lake Superior and is found as a smaller mass exposed along the north side of the Gogebic district in Wisconsin and Michigan. The dip at and near the base ranges along most of its length from 20 to 40°, but at places the internal banding dips even more steeply. The dip of the upper part is much less, and if it is assumed that the flows along the north shore of Lake Superior are a dependable indication, it does not exceed 15". The formations shown in Table I which are intruded by the gabbro range from Keewatin to Middle Keweenawan in age. They present a significant picture. At the top, the gabbro and its accompanying

Jan 1, 1953

The uranium ore processed by the McClean Lake Operation is co-mineralized with niccolite, rammelsbergite and gersdorffite (nickel arsenides). During the strong acid leach process, the majority of the reduced arsenic is oxidized and liberated into the lixiviant solution as As+5. Following uranium extraction, the residual raffinate solution, enriched in As+5, reports to the tailings preparation process. In this process, Fe+3 is first added and mixed with raffinate (pH~1) to achieve a Fe+3/Astotal molar ratio of at least 3. This is followed by two stages of neutralization, using slaked lime to achieve a solution pH of 4, and approximately 7.5, respectively. Synchrotron based x-ray absorption techniques (XANES, EXAFS) applied to neutralized raffinate solids and tailings samples collected from the tailings management facility provide evidence that arsenic has been precipitated as a poorly crystalline form of the mineral scorodite (FeAsO4?2H2O).

Aug 1, 2010

By Henry R. Tiedemann, Eugene H. Skinner, George E. Wickham

Improving the state-of-the-art of tunneling is a continuing challenge to those involved in underground construction. New methods and procedures are usually evolved over a relatively long period of time as compared to advancements in other types of construction. To a large extent this is probably due to the fact that tunneling deals with a material or medium - the rock structure - whose physical properties are not only extremely varied, but in many instances virtually unknown until time of penetration. This hovering of the unknown tends to make "non believers" of many and at best leads to a general reluctancy of accepting new ideas or procedures. The situation is further complicated by: 1) discrepancies in terminology and respective meanings as used by different disciplines to describe, define or evaluate pertinent factors and their relative effect on the tunneling process and 2) the fact that no two tunneling situations are identical with respect to either geological conditions or construction and contractual requirements. In spite of the above there have been many successfully completed tunnels which make it apparent that both the technical and practical expertise needed to develop or project improvements is available within the industry. It is with this in mind that the RSR concept was developed. BACKGROUND This paper presents the findings and results obtained from contin-

Jan 1, 1974

By K. W. Harris, K. A. Perry

Reserve depletion in Central Appalachia is continuously creating unique ground conditions for underground coal mines with many of these difficult environments directly attributable to multiple seam mining and/or deeper overburdens. While many empirical studies have been performed in an effort to improve understanding of these problems along with potentially improving safety and extraction, many of the difficulties encountered lie outside of the normal realm of expected behavior. This is often the case when mining in bump prone ground, where additional concerns are introduced and design buffers are warranted. The boundary element software LaModel was used to study three bump events in a deep-cover, multiple-seam reserve located in Harlan county in the Kentucky region of Central Appalachia. This region is notoriously bump prone due to significant areas of deep cover, the presence of strong to massive lithology (such as sandstone), and an extensive history of underground mining that increases the probability of multiple seam interactions. Multiple seam interactions are best understood with respect to site-specific parameters, including both the geological and geometrical components of interburden, overburden and mine workings. Initially, empirical-based approaches (ARMPS/AMSS) were used when attempting to back-analyze the bump events. However, it was recognized that a more detailed investigation was necessary to understand the fundamental causes/conditions associated with the bump events. Consequently, the LaModel study resulted in a mine-specific calibration method for the reserve. With this method in place, enhanced bump prediction throughout the reserve is expected, such that the stability, recovery and safety of future mining may be improved.

Jan 1, 2014