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By D. M. A. Flight, P. M. Green, J. A. Plant, P. R. Simpson

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. The British Geological Survey's regional geochemical database is used to identify the patterns associated with the various mineral deposit types and to examine the extent to which their distribution reflects the presence of long-lived metallogenic provinces in the crust. Image analysis provides new insights into the setting of the mineralisation, geochemical constraints on tectonic models of Caledonide evolution and evidence for terrane amalgamation and large-scale processes. There is evidence that much of the mineralisation reflects the presence of long-lived provinces with a distinctive geochemistry reflecting their origins as zones of crustal extension. In the case of the Middle-Upper Dalradiam sedex deposits, the relationship between geochemistry and tectonic setting is direct. In other cases, rocks deposited in extensional zones appear to have acted as reservoirs of ore-forming elements which were further concentrated during later events

Jun 19, 1905

A systematic study of groundwater conditions at eight underground mine sites exhibiting a wide range of groundwater qualities throughout Australia has been completed at the WA School of Mines. This has resulted in a new corrosivity classification for groundwater driven corrosion processes for cement grouted cable strand used in the Australian underground mining industry. The new corrosivity classification is simple to use and corrosion rates may be predicted from readily obtained in situ measurements of groundwater dissolved oxygen.

Jan 1, 2008

By John A. Herbst, Xiangjun Qiu

"Prediction of wear on a microscale level in mineral processing equipment turns out to be a challenging undertaking. This is particularly true for cases in which the objective is to use such predictions for wear parts design. The key to obtaining such predictions has turned out to be the use of physics based models along with phenomenological constitutive equations. In this paper, two components of the HFS tool set, one for particles (DEM) and one for slurry (MPF), are used for modeling. These tools are applied to the simulation of wear of SAG/AG shell lifters/plates and wear in slurry pumps. In each case wear predictions are validated with plant measurements.INTRODUCTIONHigh Fidelity Simulation (HFS) has emerged as an important tool set for mineral processing plant equipment design and optimization (Herbst and Potapov, 2003; Herbst and Nordell, 2002; Herbst and Lichter, 2006). This tool set consists of Discrete Element Modeling (DEM) of particle motion, Multi-Phase Flow (MPF) for liquid motion, discrete grain breakage (DGB) for particle fragmentation and discrete grain liberation (DGL) for mineral liberation (Campbell, Potapov and Tsuji, 1997; Ferzinger and Peric, 1997; Potapov and Campbell, 1996; Herbst and Potapov, 2005).Three sample snapshots of basic HFS illustrating the use of each of the various types of mineral processing equipment are shown below.Figure 1 shows a snapshot of a DEM simulation of ball charge motion in a commercial scale Vertimill. DEM simulation involves simultaneous solution of Newton’s Laws of Motion for 400,000 balls."

Jan 1, 2007

By Timothy D. Stark

Jet grouting has increasingly become a ground improvement technology used to address seepage concerns and provide strength improvement to soils underlying dams. The technique of jet grouting uses high pressure/volume jet fluids to erode existing soil, evacuate some or most of the soil, and mix the remaining cuttings with cement slurry to form soilcrete. While considered a useful technology, this paper discusses some of the problems that can develop while jet grouting in or below a dam with an operational reservoir and seepage condition. Jet grouting experience at Tuttle Creek Dam indicates concerns with respect to ground fracture; spoil return, column diameter consistency, and homogeneity of resulting soilcrete. Recommendations are presented to increase monitoring of downhole parameters during jet grouting to better understand the downhole pressures and soil response during jet grouting.

Jan 1, 2012

By EFFC/DFI Concrete Task Group

Concrete technology continues to advance rapidly and modern mixes with five components – cement, additions, aggregates, (chemical) admixtures and water – often have characteristics which differ significantly from the older three component mixes – cement, aggregates and water. Recent trends have favoured higher strength classes and lower water/cement ratios, resulting in greater dependence on admixtures to compensate for reduced workability and to meet the (often competing) demands for workability in the fresh state and setting time. The application of testing methods which reflect the true rheological properties of the concrete has not developed at the same rate as the mixes themselves and it is still not uncommon for the slump or flow table test to be used as the only acceptance test for fresh concrete.A joint review of problems in bored piles (drilled shafts) and diaphragm walls cast using tremie methods by both the European Federation of Foundation Contractors (EFFC) and the Deep Foundations Institute in the United States (DFI) identified a common issue. The review determined that many of the problems were caused by (or in part due to) the use of inadequate concrete mixes with inadequate workability, or insufficient stability or robustness of the mixes. It further identified the primary causes as inadequate concrete specifications and inadequate testing procedures. The consequences of these problems are often significant and it has been recognised that spending more time and money on getting the concrete right is the most cost effective approach.A joint Concrete Task Group was set up by EFFC and DFI in 2014 to look at this issue and this guide is the output from that Task Group. A research and development project, funded by the Sponsors of this guide, is being carried out by the Technical University of Munich in conjunction with the Missouri University of Science and Technology. This project includes desk studies, laboratory testing, and onsite testing at worksites in Europe and the US. The research work will be completed during 2016.

Jan 1, 2016

By Louis A. Panek, John A. Stock

A flat slot is created in rock to cause stress relief effects in a pair of hydraulic borehole pressure cells (previously installed in drill holes above and below the slot ) , which act as sensing devices . This relief is annulled by repressuring the slot by means of a flat hydraulic cell . The slot pressure at annulment is taken to be the existing ground stress at right angles to the plane of the slot . A number of trial installations in the rib of a mine drift showed that for a valid determination of ground stress the sensing devices that respond to relief and repressuring must be within a specified zone close to the pressure transmitter ; otherwise the indicated ground stress may be excessive . By using an additional pair of borehole pressure cells , installed a few feet away , the existing rock stress can be redetermined at intervals , irrespective of a change of stress intensity subsequent to the initial installation . Based on these findings , equipment and procedures have been developed that make possible the installation and operation of a permanent rock stress monitoring station for observing mining - induced stress changes . The station consists of a 12 - in - wide hydraulic pressure cell cemented in a flat slot and four 2- by 8 - in flat hydraulic pressure cells in nearby drill holes . All drilling for the installation can be done with an air leg drill and conventional bits . Once the installation is completed , all required information is obtained by Bourdon pressure gage readings . The apparatus is simple , relatively inexpensive , and reliable under operating conditions in a wet mine . Unlike most methods of rock stress determination , this scheme permits periodic remeasurement of absolute rock pressure over several years , without additional drilling or instrumentation . Similar to other flat slot procedures , stress measurements are obtained without making auxiliary tests to determine elastic

Jan 1, 1964

By Robert L. Lappi

Volume I of this report described the demonstration of cross-ridge mountaintop coal mining. This document, Volume II, is intended for use as a supporting document to Volume I. This report describes the MATHMINE Mine Simulation System, a modularized software system used to support the demonstration of cross-ridge Mountaintop coal mining. The MATHMINE Mine Simulation System was used to generate mine plans for coal extraction at lowest cost. The functional details, data requirements and output of the software system are detailed here. The computer program was written in FORTRAN. One module which generates resource location data required the use of SAS?.

Jan 1, 1984

By D. A. Buckingham

The Bureau of Mines evaluated potential availability of domestic nickel from 23 deposits, Evaluations included an estimation of in situ and recoverable resources, applicable mining and processing technologies, and capital and operating costs. Discounted cash flow analysis with a 15-pct rate of return was used to determine the average total cost of production of each operation, Identified in situ resources contain 9.0 million metric tons (t) of nickel; 5.5 million t is recoverable as nickel metal or ferronickel. Demonstrated in situ resources contain 8.2 million t of nickel; 4.8 million t is recoverable as nickel metal or ferronickel. No nickel is available at a total cost of production equal to the January 1983 market price of $3.24 per pound. Analyses indicate that potential annual production can only meet current consumption levels at a total cost of production of $7.60 per pound of nickel, Nickel's availability is contingent on (1) successful adaptability of nickel processing methods to domestic resources, (2) location of a smelting facility, and (3) marketability of byproducts and coproducts. Analyses were performed on the effects of byproduct and coproduct revenues, energy, labor, and transportation costs, and metallurgical recoveries on nickel's availability.

Jan 1, 1984

By E Lounejeva, J A Halpin, A Chappaz, D D. Gregory, S Wu, T Lyons, P J. Sack, R R. Large, S W. Bull

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Newly published models suggest that some orogenic and Carlin-style gold deposits formed by the remobilisation of trace elements during interaction with hydrothermal or metamorphic fluids from early sedimentary pyrite that was enriched in Au, As and Te. The released trace elements are transported by the fluids to favourable trap sites where they are deposited. Therefore, early enrichment of Au, As and Te in source rocks (particularly in pyritic black shale) can be crucial to the formation of orogenic and Carlin-style gold deposits.The most important cause of the enrichment of gold and other trace elements in the sedimentary basins has been examined in this study to determine which basins are the most prospective for the development of orogenic gold deposits. An important influence for Au and other associated trace element accumulation in sedimentary pyrite is the temporal variation of trace element content in the oceans, as revealed by a database of over 1400 analyses of pyrite from black shale through geologic time. It is inferred that sediments coeval with those where sedimentary pyrite is enriched in Au and associated trace elements are more likely to be source rocks of orogenic and Carlin-style gold deposits.Factor analysis of the trace element content of pyrite through geologic time was conducted to investigate the multivariate relationships amongst trace elements and how these chemical factors explain the uptake of trace elements. One important factor includes Te, Au, Pb and Bi content. The incorporation of these large cations into pyrite is enhanced by As3+ substituting for Fe in pyrite lattice. The As3+ ion occurs in relatively oxidised environments and, thus, it is expected that shales deposited in non-euxinic waters are better source rocks for orogenic gold deposits.The examination of both the time in which the sediments were deposited and the redox conditions of the basin, and the ocean more broadly, can be used as a guide to approximate the extent of a basin’s fertility. To illustrate the use of this exploration tool, examples from the unmineralised Jet Rock Formation (UK) and the mineralised Castlemaine Group (Bendigo, Australia) are presented in this paper.CITATION:Gregory, D D, Large, R R, Halpin, J A, Lounejeva, E, Wu, S, Bull, S W, Sack, P J, Lyons, T and Chappaz, A, 2015. Accumulation of trace elements into black shale – how to identify a viable source rock for orogenic and Carlin-style gold deposits , in Proceedings PACRIM 2015 Congress, pp 59–64 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By E. V. Deshayes, W. E. Young

"INTRODUCTION The Camp Bird mine was investigated by Bureau of Mines engineers 3/ September 22 and 24, 1942, and April 29 and 30, 1944. In a subsequent report and supplement, it was recommended that core drilling be done below the 14th. level to determine if commercial ore existed at greater depths, and particularly if ore existed in the vein or adjacent thereto where it passes into the sedimentary formations estimated to underlie the volcanics approximately 400 feet below the 14th level.Seven diamond-drill holes aggregating 3,956 feet were drilled. Four of these holes were under the Hematite ore body and three were under the Big Discovery ore body. Two holes under, the Hematite ore body wore directed at angles but little steeper than the angle of dip of the vein and penetrated the sedimentaries beneath the volcanics close to the vein. Enough low-grade ore was found at the base of the Telluride conglomerate to indicate the presence of a large body of low-grade zinc sulfide ore. Two holes were directed to crosscut the vein at a depth of approximately 125 feet below the 14th level. No commercial ore was cut, but the vein showed the average width and same general characteristics as at the 14th level. One hole under the Big Discovery ore body was directed to crosscut the vein and test the base of the Telluride conglomerate in the footwall block. No commercial ore was found in either the vein or the sedimentary horizon. One hole was directed to test the base of the Telluride conglomerate in close proximity to the vein in the hanging-wall block. This hole was lost approximately 100 feet short of its objective, and a third hole was drilled to accomplish this same thing. The third hole was stopped approximately 50 feet short of its objective when failure of equipment caused a recess of the"

May 1, 1948

By D. G. Willard

The U.S. Department of Interior, Bureau of Mines has evaluated the potential resource and annual availability of cobalt from 27 deposits or districts in 11 market-economy countries. More than 95 pct of primary cobalt production from market-economy countries, mainly byproduct output from copper and nickel operations, was analyzed. Approximately 1,200,000 mt of cobalt is potentially recoverable at the demonstrated resource level. Very large additional resources exist, especially in laterite deposits, but are at the inferred level. The producing operations evaluated in this study are expected to produce about 19,000 mt of cobalt in 1989, significantly less than the available capacity of about 31,000 mt. More than 14,000 mt per year of cobalt is produced from copper-cobalt deposits in Zaire and Zambia, of which 11,000 mt can be produced at a copper price of $O.60jlb or less with a O-pct discounted cash-flow rate of return (DCFROR). Approximately 4,400 mt of cobalt is produced annually from nickel-cobalt deposits in six countries, of which about 1,800 mt (in Canada and Brazil) could be produced at a nickel price of $1.50jlb or less at a D-pct DCFROR. Approximately 200 mt per year of cobalt is produced from a cobalt mine in Morocco. Most of the evaluated nonproducing operations and prospects that could potentially produce cobalt as a principal product or byproduct would require a total cost (including a 15 pct-DCFROR) significantly exceeding January, 1989 market prices of the principal commodities. Principal-commodity dependence, transportation routes, cobalt toxicity, and other issues that could affect the availability of cobalt are addressed herein.

Jan 1, 1991

By Leon del Valle, Joe Phillips

First, I want to thank my co-author, Leon del Valle for his help and collaboration in the preparation of this paper, and also ORICA S.S. our explosive supplier and contractor at the Refugio mine site for their collaboration. The Southern Andes Mountains present a number of challenges for mining operations, and associated blasting operations. This region of the world, in Peru, Bolivis, Chile and Argentina is an area of rapid growth in precious and base metal mining, and will continue to be a large growth area for explosives products and services. This paper will attemp to discuss some of the special considerations encountered in operating a safe and effective blasting program at high elevation and under extreme weather conditions, as well as outlining a recent improvement in blasting techniques at the Refugio gold mine in northern Chile. This paper is presented from a mine operator's perspective, which may be a bit of a disappointment for some of you interested in a detailed technical review of our program. It willl, however, provide an insight in how in-pit blasting techniques tie into the metallurgical processes at a modern precious metal mine and thereby become a key elemnet in its success.

Jan 1, 2000

By Jose a. Sanchidrian, Ramon G. Eguren, Javier L. Amigo

On December 2013 a MEMU exploded at a blasting site in Norway, after burning for more than two hours. This paper describes the analyses made to determine the actual yield of the explosion, the lessons learned from the event and the actions taken as a consequence. The conclusions of the analysis were the following: - The yield of the explosion was 650-1450 kg TNT. In terms of AN and ANE they correspond to 1300 – 3700 kg AN, or 950 – 2450 kg ANE or ANE/AN blend. These quantities are 8 to 31 % of the explosive precursors in the truck. The burning of the truck and its load for two and a half hours had consumed more than two thirds (perhaps up to 90 %) of the explosive precursor material.

Jan 1, 2016

By L. C. Bird, N. T. L. Landgren, M. W. Mikhail

"Through funds made available in 1972 by the Nova Scotia Department of Mines and Energy (DME) and the federal Department of Regional Economic Expansion, a program was initiated to recover saleable coal from mine waste dumps adjacent to the existing Acadia wash plant in Stellarton, Nova Scotia.Following evaluation of these dumps in 1972, the Acadia wash plant was modified to treat high-ash material. The first production was recorded in late 1974. By the end of 1979, a total of 738,202 t of dump material had been processed, yielding a total of 205,212 t of thermal-quality coal.The successful Stellarton operation led to considering the possibility of recovering thermal coal from other dumps. Evaluation of the Westville dumps indicated total recoverable reserves of 1,346,617 t averaging 53.8OJo ash.Parameters for plant design were defined from the washability characteristics of the dump material and the results of a bulk test. Two options were proposed; one was to use the existing plant with some modifications, the other was to build a modular mobile plant that could be used at future dump sites in the province after Westville. At the 25% ash level, the potential recovery of coal from the dump was estimated at 41% yield (by weight) or 549,679 t."

Jan 1, 1981

By D. J. W. Piper, T. Hundert, G. Pe-Piper

"Abstract - Potentially commercial deposits of kaolin are found in the fluvial Lower Cretaceous Chaswood Formation, the sedimentologically proximal equivalent of deltaic sediments of the offshore Scotian basin. The geological setting of the kaolin deposits has been interpreted from high-resolution seismic-reflection profiles and boreholes, and mineralogical studies on one reference borehole. The kaolin is a product of early diagenesis involving meteoric water below the water table. The distribution of kaolin is controlled by the presence of intraformational unconformities that were sites of ground water recharge, and are marked by the development of oxisols above the water table. Such diagenesis was facilitated by interbedded, loosely consolidated, permeable sandstone. The highest-grade kaolin deposits are found in areas close to river belts, where overbank muds were not sufficiently drained to develop paleosols, but where later uplift created intraformational unconformities. In the sandstone, meteoric water flow altered feldspars to kaolin, thus yielding commercial silica sand deposits. It also altered ilmenite to rutile, which is concentrated as secondary placers in modern rivers that have eroded the Chaswood Formation and tills derived therefrom. Sommaire - Des dépôts de kaolin potentiellement économiques ont été notés dans la Formation de Chaswood d'’âge Crétacé Inférieur, laquelle constitue un équivalent latéral en milieu fluviatile aux sédiments deltaïques du bassin de Scotian. Le contexte géologique de ces dépôts de kaolin a été interprété a partir de profils de seismique-réflection à haute résolution, de sondages, et d’études minéralogiques sur un sondage de référence. Ce kaolin est un produit diagénétique précoce formé par de l’eau météorique sous le niveau de la nappe phréatique. La distribution du kaolin est contrôlée par la présence de zones de recharge associées à des discordances intraformationelles marquées par le développement d’oxisols au-dessus du niveau de la nappe phréatique. La présence d’interlits de grès perméables faiblement consolidés a contribué à l’efficacité de ce processus diagénétique. Les dépôts de kaolin les plus riches se trouvent en périphérie des rivières, là ou les boues de la plaine d’inondation n’étaient pas suffisamment bien drainées pour permettre le développement de paléosols, mais où des mouvements verticaux subséquents ont crée des discordances intraformationelles. La circulation d’eau météorique dans les grès a entraîné l’altération des feldspaths en kaolin, générant ainsi des dépôts économiques de sable de silice. Elle a aussi causé l’altération de l’ilménite en rutile, que l’on trouve dans des placers secondaires situés dans des rivières contemporaines qui ont érodé la Formation de Chaswood et les tills qui en sont dérivés."

Jan 1, 2006

By Frank E. Federspiel

In 1992, the Bureau of Mines conducted a mineral resource investigation of the 78,000-acre Garns Mountain study area in southeastern Idaho. The area had been proposed for Wilderness. It is underlain by Paleozoic to Mesozoic-age sedimentary rocks about 11,000 feet thick. Rocks have been faulted, offset, and folded as part of the northerly-trending Idaho-Wyoming Overthrust Belt. Study area mineral occurrences are: phosphate in the Permian Phosphoria Formation; coal in the Cretaceous Frontier end Bear River Formations; and uranium in carbonaceous and phosphate-bearing shales and coal of these formations. Four zones of phosphate are estimated to contain about 528 mitt ion tons of rock with over 10% P205; samples of phosphate-rich rock also contained as much as 3950 ppm chromium, 3280 ppm vanadium, 23 ppm gallium, and 5540 ppm zinc. Fragments of poor-quality coal and carbonaceous shale were found in the area; coal was mined near the northeast border. Uranium content up to 0.016% U3O8 is in carbon-rich shales. Oil and gas were drilled for, with minimal success, in folded sedimentary rocks (frontier and Nugget Sandstone) in the Horseshoe anticline, near the east border. Examined workings included 12 dozer cuts, 4 trenches, 2 prospect pits, and 2 caved adits. No production is known, and no leases or claims are held for the area.

Jan 1, 1992

A field method combining solvent extraction and paper partition chromatography permits a simple and rapid semiquantitative estimation of gold in siliceous, argillaceous and sulphide ores. The method will facilitate the eyaluation of prospect samples in which the gold is too fine for separation by panning.Ethyl alcohol-hydrobromic acid mixtures are suitable for chromatographic development of the gold complex, and give clear reproducible definition of the gold zone. Substitution of commercial "methylated spirits" for the ethyl alcohol gives equally good definition, improving the potential of the method for field use.A batch of six samples in the range of 0·5 to 5·0 dwt/ton can be completed in two hours. The range may be extended by simple modification to higher or lower values.INTRODUCTIONIn a chromatographic method described previously (Lever 1958, Nevill and Lever 1959), gold from a standard volume of ore clamped between -plate glass was extracted by aqua regia on to the paper. After cautious drying the chromatogram was developed by an ethyl acetate-nitric acid-water mixture and gold was identified by spraying with stannous chloride solution. Sensitivity of the method in the low range was poor. The brown line obtained in the 1-3 dw/j ton range, caused by movement of gold in the reduced form, was not considered to be a satisfactory confirmation of the presence of gold. It was felt that the method would be improved by using a more elegant extraction and applying developing conditions which would produce a well defined purple line at all gold values. Iron was a limiting factor, and a method of eliminating its interference was needed.The method now developed overcomes these shortcomings, and gives a reliable result with a purple line for assay values of 0·5 dwtjton and over. Gold is dissolved from an...

Jan 1, 1964

By A. J. Monhemius

"This paper reviews the history of modern iron-control processes in hydrometallurgy. Attention is paid to processes developed in the electrolytic zinc industry for removal of iron from zinc sulfate leach liquors and the problems faced by the industry in the safe disposal of the iron residues produced by these processes. Past lessons learned are projected onto current efforts to develop hydrometallurgical processes for treatment of copper sulfide concentrates. It is argued that any attempt to create a “hydrometallurgical copper smelter” will fail, unless methods are developed that can recover iron in a form that can be directly used by the steel or pigment industries.RÉSUMÉ Cet article passe en revue l’histoire des procédés modernes de contrôle du fer en hydrométallurgie. Il accordera une attention particulière aux procédés développés dans l’industrie du zinc électrolytique pour l’élimination du fer dans les liqueurs lixiviantes de sulfate de zinc anhydre, ainsi qu’aux problèmes rencontrés par l’industrie en termes d’élimination sans danger des résidus ferreux générés par ces procédés. En projetant les leçons tirées du passé sur les efforts actuels, on pourra développer des procédés hydrométallurgiques pour le traitement de concentrés de sulfure de cuivre. Beaucoup prétendent que toute tentative de créer une « fonderie de cuivre hydrométallurgique » échouera à moins de développer des méthodes permettant de récupérer le fer sous une forme pouvant directement être utilisée par les industries sidérurgique ou des pigmentsINTRODUCTIONThis paper resulted from an invitation to the author from the CIM’s Historical Metallurgy Committee to give a presentation on the early developments of iron control in hydrometallurgy. This was to take the form of a plenary lecture at the 4th Symposium on Iron Control in Hydrometallurgy, which formed part of the 28th International Mineral Processing Congress, held in Quebec City in September 2016.I was naturally flattered that the invitation was to give the lecture at an IMPC, the prestigious conference series that has been held since the 1950s. That this particular IMPC was to include the 4th Symposium on Iron Control in Hydrometallurgy, a conference series held only every 10 years, made the invitation even more appealing and appropriate. This was because I had been co-chairman of the First Symposium on Iron Control, together with my erstwhile colleague, John Dutrizac, which was held 30 years ago in Toronto."

Jan 1, 2017

By N. M. Skarbøvig

Safety nets have been used selectively in several South African mines over the years. Recently, however, an increased emphasis on mine safety has seen a resurgence of their utilization underground. This renewed interest has, however, also raised questions about the design and performance of these nets and their practical applications underground; these are the subjects of this paper. Generally, mine safety nets are used to protect personnel from falling rock in temporarily supported development ends, tunnels, ASGs and stopes. These diverse applications each require specific net designs, resulting in a wide product range. As a rule, however, mine safety nets need to carry specified static or dynamic loads with the least possible deformation. Because of the application-specific characteristics of mine safety nets, there is no South African national standard for them. Consequently, neither the SABS, nor the CSIR, performs standard tests on these components. In 2007, therefore, SIMRAC made available their Savuka facility for the testing of mine safety nets; the Savuka drop test became the accepted industry test standard for mine safety nets. From late 2007 to mid 2009, Norsenet, in collaboration with SRK Consulting, the designated operators of the site, conducted approximately 200 tests, which formed the core of Norsenet's database of safety net performance under various loading conditions. The test specimens comprised a wide range of net materials and config¬urations; the materials included: high density polyethylene, polypropylene, polyester, nylon, as well as a blend of polyester and polypropylene used primarily for reinforcement ropes. Net configurations encompassed the following parameters: net type, i.e., knotted nets or sewn nets; net strand type, i.e., braids, twines, or webbing; strand size; mesh size; mesh orientation, i.e., parallel or oblique to the net edge; net edge reinforcement, i.e., knotted, tied, with or without reinforcement ropes; internal reinforcement ropes, i.e., diagonal ropes and/or orthogonal ropes; as well as net attachment options, including loops and chainlinks. From the number of variables listed above, and the limited number of tests available, it can be appreciated that the findings of the test series required careful scrutiny. Nevertheless, principal performance factors clearly emerged: besides the obvious net mesh variables, such as net strand material, strand diameter and mesh size, it was the configuration of the reinforcement ropes and their attachment to the net panel which had the strongest influence on net performance. All the structural elements of a safety net need to work together to transfer the imposed load from the net panel, through the reinforcement ropes, to the net attachment points. In this load transference chain, the weakest link limits the strength of the structure. From this development work, Norsenet has gained valuable expertise to custom-design and manufacture nets to clients' specifications. The examples presented in the paper will also show the experience acquired in the installation of nets underground. Future work will include the establishment of a state-of-the-art net testing facility at Norsenet's factory in Vredenburg.. Keywords Mine safety net, safety net, protective device, mine safety, safety net design, safety net performance, safety net applications.

Jan 1, 2011

By Paul Cameron Gilmour

Geologically, as distinct from economically, "porphyry copper (molybdenum, gold, silver, etc.) deposits" might be defined as large, disseminated and/or stock-work occurrences of copper-minerals, generally averaging less than 1 per cent cop-per. They are normally associated with small plutons which range in composition from granite to diorite, although, typically, they consist of quartz monzonite or granodiorite. Circumstantial evidence indicates that these "minor" granitic intrusions may represent the intrusive phases of post-orogenic, calc-alkaline volcanism, this conclusion being suggested by: 1. Texture and grain size. 2. Prevalence of intrusive breccias. 3. Relationship to unconformities and estimated depth of emplacement. 4. Spatial distribution in relation to orogenic zones. 5. Age of mineralization and igneous episodes

Jan 1, 1972