Search Documents

By P. A. Geusebroek, N. A. Duke

Abstract - The Lupin mine, located in the central Slave province just east of the western boundary of Nunavut Territory, is a world-class example of a Neoarchean-aged banded iron formation (BIF)-hosted lode-gold deposit. At the minesite the gold-mineralized Lupin BIF, separating stratigraphically underlying psammitic wacke and overlying argillaceous turbidite sequences, delineates the Lupin dome, a hammerhead-shaped F2/F3 interference fold structure occurring at the greenschist to amphibolite facies metamorphic transition within the thermal aureole of the Contwoyto batholith. Detailed paragenetic relationships indicate that peak thermal metamorphism coincided with the switch from regional D2 compression to rapid D3 unroofing of the Neoarchean orogenic infrastructure. Gold initially precipitated with pyrrhotite, replacing amphibolitic BIF at the apex of the Lupin deformation zone, separating the east and west lobes of the Contwoyto batholith. Over the course of associated prograde/retrograde metasomatic overprints, gold was further remobilized during garnet and loellingite/arsenopyrite growth in chlorite-altered selvages of late-forming ladder quartz veins. A metamorphic model of ore genesis, with gold being scavenged and transported by metamorphic fluid that was shed and structurally trapped at the amphibolite recrystallization front, is favored over the previously proposed syngenetic and exogenic models of gold concentration that have tended to polarize genetic interpretations to date.

Jan 1, 2004

By Jeff Friedman

This paper addresses certain problems to be encountered when a blasting contractor agrees to provide indemnification. Nearly 100% of all blasting work is performed pursuant to a contractual agreement. Whether the explosives engineering firm works directly for the property owner, or for a general contractor by way of subcontract, indemnification agreements are generally required to protect owners, operators, general contractors, and other interested parties in the event there is subsequent litigation. These contractual requirements are typically referred to as indemnification and “additional insured” agreements. We will address the ramifications of contractual indemnification as well as “additional insured” agreements in this presentation. Some of the aspects of this paper will include:

Jan 1, 2004

By Brian D?Olier

Much of the aggregate that is being exploited at present from these areas is a ?relic? deposit. It was originally eroded from primary source rocks and transported to a depositional centre by processes that are now either greatly reduced in effectiveness or are largely absent at the present time. Following the retreat of the Devensian ice sheet, the subsequent rise of sealevel and the drowning of large areas of the continental shelf along with the lower reaches of many rivers, a fresh sequence of sediment sources, pathways and sinks now exist. Sediment is being eroded from several, pre-existing source areas and transported along different, well - defined pathways to a number of new depositional sinks. Some of the present, licenced, aggregate dredging areas lie close to these sources, pathways and sinks with the consequent dredging activity being perceived by some as interfering with the ?natural process? that links the offshore and the coastal / littoral zones. With this perception in mind, the principal, sources, pathways and sinks between Flamborough Head and Beachy Head will be highlighted and the relationship of dredging activity upon them, evaluated. It will be demonstrated that offshore dredging activity has no effect upon supplies of sediment to coastal beaches.

Jan 1, 2004

The papers in this section of the conference and indeed the conference as a whole will rightly focus on the recent û the state of play around the Pacific Rim. However, to set the scene I propose to take a longer-term perspective. In so doing I wish to illustrate and emphasise that change is normal and natural û to paraphrase Bob DylanÆs 1963 classic, æThe times they are (always) a-changinÆ Æ. The challenge is how to cope with such change, in an industry, a corporate and a personal sense. A further challenge for geologists, both exploration and mine-based, and indeed for anyone, is to understand where they fit in the broader picture. For several reasons it is appropriate first to look briefly at the minerals industry in the Pacific Rim around a century ago. It was here in Adelaide in April 1893 that the first general meeting of the Australasian Institute of Mining Engineers (or The Australasian Institute of Mining and Metallurgy as it later became) took place and where the Centenary Meeting was held in 1993. The late 1800s and early 1900s was a period of extraordinary change in the minerals industry regionally and worldwide. The industry benefited from the economies of scale provided by improved mechanisation. It further benefited from the introduction of technically qualified professionals, such as chemists, metallurgists and mining engineers, although the usefulness of geologists had yet to be recognised commercially. With the rise of such professionals, technical societies formed and flourished. At the same time international financial markets and trade were expanding, a gold standard was widely supported and the financing of mining ventures was well established. Mining was an international business and its people travelled widely. As a consequence of the better-educated mining professional, the ready exchange of knowledge and the availability of finance, new processing techniques such as pyritic smelting, the cyanide process and flotation were developed. These, together with much improved materials handling in the mining and processing phases, dramatically changed the economics of the minerals industry.

Jan 1, 2004

By J M. Santini, I C. A Streimann

Arsenic is a naturally occurring element in the environment and is toxic to biological systems. Arsenic can exist in the environment in the following redox states, arsenite (+3), arsenate (+5), arsine (-3) and elemental (0) (Oremland and Stolz, 2003). Arsenic is released into the environment by natural and anthropogenic activities such as rock weathering and ore mining, respectively. Such activities result in the release of the soluble inorganic arsenic oxyanions, arsenite and arsenate. The redox state of arsenic in the environment is influenced by a number of factors including, redox potential, pH and microorganisms (Irgolic et al, 1977; Genc-Fuhrman, Tjell and McConchie, 2004). Recently, the ability of microorganisms to influence the cycling of arsenic in the environment has attracted much attention. Microorganisms that can oxidise arsenite and reduce arsenate have been isolated and the mechanisms of arsenic metabolism are currently being investigated. The differences between arsenic resistance and arsenic metabolism are being revealed. The role of microorganisms in the release of arsenic into the environment is of particular importance with arsenic contamination of waters causing the death of millions of people worldwide, due to the consumption of contaminated water (Vasken Aposhian et al, 2003; Islam et al, 2004).

Jan 1, 2004

By P J. Clark, A W. Fisher, R G. Ford

Site characterisation of subsurface contaminant transport is often hampered by a lack of knowledge of site heterogeneity and temporal variations in hydrogeochemistry. The use of a regional-scale data compilation derived from satellite imaging is discussed with respect to directing design of site characterisation to monitor the fate of a Dense Non-Aqueous Phase Liquid (DNAPL) plume in Nevada. Evaluation of the drainage basin contributing to the groundwater flux into the study site was used to re-assess the site conceptual model and re-direct the characterisation effort. The use of highly resolved measurements of subsurface hydrogeochemistry in space and time were employed to identify the predominant biogeochemical processes controlling arsenic transport during discharge of groundwater into a pond at a site in Massachusetts. Direct-push conductivity measurements coupled with vertically-resolved sampling within the pond and adjoining aquifer demonstrated spatial and temporal variations in dissolved arsenic within groundwater and the pond water column and sediment pore water. Spatial variability was observed over the scale of centimetres to metres, and temporal variations were observed over the scales of days (following storm events) to seasons. Microbially-driven redox processes maintained anoxic conditions in groundwater and at the sediment-water interface (iron and sulfate reduction) and exerted both a direct and indirect influence on arsenic solution speciation and partitioning to surface water sediments.

Jan 1, 2004

By Naresh Koirala

The Greater Vancouver Regional District completed installation of a 2.5 Km long, 2400 mm diameter concrete sewer in Delta, British Columbia in 2000. The sewer traverses through area of peat and soft ground. The ground investigation along the sewer alignment consisted of cone penetration tests and auger drilling with standard penetration tests. The gravity sewer is supported on precast, pretensioned spun concrete piles imported from Malaysia which had never been used for a major project in North America. The capacities of the installed piles were tested using pile driving analyzer (PDA) and three static load tests. A total of 46 PDA tests were carried out during pile installation. The paper describes the pile vetting process the owner went through prior to accepting the piles for use in the project and performance of the piles. It compares the pile capacity estimated from the PDA tests with that estimated from soil mechanics methods using data from cone penetration tests and standard penetration tests. The ranges of estimated capacities calculated by different methods are discussed from design capacity selection considerations.

Jan 1, 2004

By L. Munsamy

The bulk of primary mining at the Anglo Coal's Bank Colliery was carried out by drill and blast method, in a bord and pillar layout exploiting the No. 2 Seam. Secondary extraction, top/bottom coaling, also took place using both the drill and blast (D&B) method and continuous miners (CM). Extensive mining in this seam resulted in the risk of sterilising the No. 4 Seam reserves. Therefore, multiseam design guidelines established by Salamon and Oravecz (8) were re-evaluated in light of the low safety factors and the low pillar width to mining height ratios of pillars in the No. 2 Seam. Two and three dimensional (2D & 3D) numerical modelling was carried out to quantify and verify the parameters that influence the multiseam mining. The modelling was conducted primarily in two dimensions (plane strain), with 3D models to confirm the validity of the 2D results. A panel risk assessment flow chart was developed to assess the panels with respect to pillar failure and multiseam mining. This flow chart was extended into the evaluation of risk of surface subsidence using the current rock engineering knowledge. The aim of this risk assessment tool is to assess all underground workings at Anglo Coal collieries simply and rapidly. The identification of high-risk areas would warrant further investigation and possible backfilling to reduce the risk of pillar failures ensuring that reserves in the No. 4 and 5 Seams above are intact.

Jan 1, 2004

By Dennis J. Kemp

Laterite projects are found in the tropical and sub-tropical regions of the world. As a result severe meteorological situations accompany such projects, often in regions of high seismic activity and political uncertainty. Frequently, socio-economic development supported by political interest is a major driver for development, while environmental protection imposes numerous stresses on the project. This paper will review and examine the many social, environmental, technical and financial issues that a mining and extraction process is subject to during development. The options that must be evaluated will be discussed in the context of sustainable development. Issues of project standards and cultural impact through to long-term issues such as greenhouse gasses and climate change will be assessed in redirecting project environmental norms. Although a rationale for sustainable project can be developed many long- term uncertainties around issues remain. Keywords: sustainable development, communities, social issues, standards, energy, waste management, consultation, agreements

Jan 1, 2004

By Y S. M Tabatabaei, R Hosseini Tabata

Application of Acidithiobacillus ferrooxidans bacteria to flotation of Sarcheshmeh low-grade copper sulfide ore was studied. Sarcheshmeh low-grade ore contains pyrite, which causes some problems in the flotation of copper minerals. In this study, A ferrooxidans was used to change the surface chemistry of pyrite and copper sulfide ores and consequently, their flotation behaviour. In the presence of A ferrooxidans and xanthate as a collector, pyrite was depressed whereas chalcopyrite and other sulfide minerals were unaffected. In addition, the pulp pH remained unchanged. It was shown that the surface chemical properties of the bacteria could be manipulated successfully to achieve the desired effects in a flotation process. The results showed that the recovery of pyrite in the presence of the bio-depressant is 50 per cent lower than when no bacteria were present. At the same time the recovery of chalcopyrite remained unchanged.

Jan 1, 2004

By Kiseong Hyeong

The Intertropical Convergence Zone (ITCZ), where the southeast and northeast trade winds converge, is the effective climatological barrier that separates the southern and northern hemispheres in terms of dust budget. Asian and N. American dusts dominate in the Pacific north of the ITCZ, while Central and S. American dust prevails south of the ITCZ. In order to understand the nature of latitudinal and depth-related variations of mineral composition in terms of position relative to the ITCZ, deep-sea core sediments were collected from 9°N to 17°N at a 2° intervals along the 131.5°W meridian and analyzed for mineral composition. The amount of illite in surface sediments decreases gradually from 65% at 17°N to 31% at 9°N. In contrast, smectite increases from 11% to 56% southward. The observed mineralogical variation toward the ITCZ is attributed to the increased supply of volcaniclastic material transported via the southeast trade winds from the Central and South America source regions. Smectite-illite transition, a phenomenon that the amount of smectite increases over illite, occurs at around 10°N, the northern margin of the ITCZ. This result indicates that the change in latitudinal position of the ITCZ in the geological past could be recorded by the smectite-illite transition in deep-sea cores. The cores studied show down-core variation of mineral composition from illite-rich at the surface to a smectite-rich clay suit at depths, similar to the latitudinal variation. The smectite-illite transitions observed in these cores are likely the records of changes in latitudinal position of the ITCZ. The depth and age of the smectite-illite transition is getting shallower and younger towards the equator, implying that the ITCZ was located farther north during late Tertiary and has shifted southward to the present position of 5°N~10°N.

Jan 1, 2004

By 12670

The Cigar Lake project will develop the world’s second largest high-grade uranium deposit. The Cigar Lake Phase 1 orebody contains approximately 226 million pounds U3O8 at an average grade of 20.7% U3O8. The mine, to be operated by Cameco Corporation, will use a unique water jet boring mining method to cut previously frozen ore. A distinctive ore handling design is required to handle the highgrade ore slurry exiting the mining machines. The ore will be crushed and ground underground, with the ore slurry then pumped to surface. Loaded into purpose-designed containers on tractor-trailer units, the ore slurry will be trucked to Cogema Resources Incorporated’s McClean Lake mill. McClean Lake will leach all of the ore. Forty-three percent of the resulting uranium solution will remain at McClean Lake for processing into yellowcake. The other 57% of the uranium solution will be shipped to Cameco’s Rabbit Lake mill for processing into yellowcake there. Detailed design for the Cigar Lake project is now underway. Barring regulatory or market delays, production could start up as soon as early 2006.

Jan 1, 2004

By H. K. Lin, J. L. Oleson

The purpose of this study is to develop a mathematical model to describe the oxidation of cyanide with SO2as proposed in the Inco process. This research employed a direct method for measuring the change in cyanide concentration with respect to time as effected by varying concentrations of SO2, copper and pH. Developing this model may be applicable in determining optimum conditions in a process well known and used in the mining industry. It was determined that the reaction is first-order with respect to cyanide, SO2and [Cu+2].The reaction order is 0.15, or zeroth order with respect to [H+] at pH range from 8.0 to 9.5.The activation energy, Ea, is 21.6 kJ/mol. The overall rate equation, as determined through this study is: [ ]

Jan 1, 2004

By G. Plascencia, A. Warczok, M. Zamalloa, T. Utigard, N. Behnood

The objective of this investigation was to investigate interactions between high-grade copper mattes and Rexal 60DB direct bonded basic bricks. The infiltration and attack of Rexal 60DB bricks by copper matte and continuous converter matte was investigated in laboratory tests at temperatures up to 1300 °C. The brick dissolution and infiltration tests did not show any significant difference between the 70% Cu and the 81% Cu mattes. More metallic copper was visible in the pores in the case of 81% Cu matte. An important mechanism for direct-bonded magnesia-chrome brick destruction is that oxysulphides start to infiltrate the brick, followed by slow oxidation of the matte producing metallic copper and cuprous oxide, which then react with MgO and Cr2O3, primarily attacking the direct bonds of the brick.

Jan 1, 2004

By A. Yoshida, H. Miura, S. Yamaguchi, Y. Oyama

A discussion is given on the ionic equilibria and precipitation reactions in seawater based on thermodynamic analysis, in order to understand the solubility of nutrient salts from dephosphorization slag for marine phytoplankton. Solubility of constituent ions in aqueous solution in equilibrium with solid phases are determined using thermodynamic data. It is proposed that CO2 potential defined as log Pco2 should be considered as an additional parameter to the Eh- pH diagram for the ionic equilibrium of slag components in seawater, since magnesium and calcium carbonate precipitation reactions determine the solubility of ligand ions in nutrient salts, such as phosphates, silicate, and sulfate.

Jan 1, 2004

By Arvindh Gupta

BC Hydro proposed to improve the stability of the existing Seven Mile Dam with 54 corrosion protected, re-stressable anchors comprising 92/0.6? strands each, in phase 2 of the program. Being globally the largest capacity anchors ever build, coupled with extra ordinary specifications, the project was a challenge for the entire post tensioning industry. The paper discusses the challenges associated with the anchor material supply as per specifications, extensive research and development carried out by Con-Tech Systems ltd. to overcome the challenges and contribute in making the project a success. The substance of this article is published in the Aug/Sep issue of ADSC magazine.

Jan 1, 2004

By J Watson

Electronic detonator technology has been under development for the last two decades. Currently, there are a number of systems commercially available with several others still under development, each with its own unique features. This technology can offer a significant advantage to the drill and blast engineer through their ability to initiate an explosive charge at the æplannedÆ time. This new technology has created huge interest within the drill and blast community and also raised their expectations to produce better blasting outcomes. In many cases, specifications (or even expectations) of desired blast results are not properly defined. Interaction between the input variables (rock mass characteristics and blast design) and results (fragmentation, throw, damage, ground vibrations, etc) and their mechanisms, or relationship to one another, are not very well defined or understood. That is why rock blasting is still considered by many as an art rather than science. With one of the few remaining variables (cap scatter) now controllable, todayÆs blaster finally has the ability to apply science to his trade. Even though electronic detonators are available and becoming more commonly used, current field practices are not always conducive to extracting or deriving the maximum benefit from this new technology. In the authorÆs opinion, the following need to be understood to derive and sustain the maximum value: clear definition or specification(s) of desired outcomes from a given blast; impact of different features in an electronic detonator system (precision, accuracy, flexibility, reliability, etc) and their impact on the desired blasting outcomes; interaction of blast design variables (energy, energy distribution, timing, blast geometry) and their impact on desired outcomes; impact of rock mass variability and quality of blast implementation on the desired blasting outcomes; and critical need to utlilise appropriate tools and systems in order to measure and quantify benefits.In the authorÆs opinion a scientific implementation process is the key to derive the benefits. This paper analyses the industryÆs preparedness to derive the benefits from this technology and proposes a scientific methodology to understand, evaluate and sustain the value from this technology.

Jan 1, 2004

Previously, a variety of risk rating systems were used on different mines. However, these were mostly site specific and geology based systems. The purpose of developing a uniform rating system, to be used on all Anglo Coal open cast mines, is to provide an unbiased, standard and quantifiable assessment of the risk from highwall and lowwall failures. This takes into account relative differences in the importance of hazards, as experienced on each mine as a result of different combinations of geotechnical factors and mining conditions. The system is based on critical geotechnical and other parameters that have been identified by mining personnel and rock engineers. The primary advantage of this risk rating system is that all open cast mines in Anglo Coal use an almost identical system, which enables the user to compare their risk to the risk at neighbouring mines and/or other open cast mines. The system can be adjusted to meet local, mine specific requirements. The implementation of this new system (a computer program that automatically calculates the risk) has been made as practical and easy to use as possible. Therefore, this tool can be used by personnel from other mining disciplines not directly related to rock engineering.

Jan 1, 2004

By Mustapha Zergoun

This paper presents the results of load tests to assess the vertical load carrying capacity of concrete expanded base piles, or pressure injected footings, for various projects located near Vancouver, British Columbia, Canada. The site subsurface conditions and load test methods are described for the Vancouver International Airport site and the test results are reviewed under both compression and tension loading conditions. The pile load tests at Vancouver International Airport are compared to load tests at other sites near Vancouver. The pile load test results are reviewed with respect to available methods of estimating the vertical capacity of this type of piles. The effect of ground improvement by densification on the load test results is considered. The limitations of tension load tests on single piles with respect to uplift resistance of pile groups under seismic conditions are pointed out. Recommendations are proposed regarding pile load test methodology to estimate ultimate vertical load carrying capacity of plies for limit state design.

Jan 1, 2004

This paper will review the experiences of both big and small exploration/mining companies (local and foreign investors), including the impediments to exploration and project development in Indonesia since the Contract of Work was first introduced there (1967 Minerals, 1981 Coal). This is seen through the eyes of a person who has been employed in a managerial capacity in large and small concerns, and more recently as an independent consultant. Comment will be made on the political, legislative and social constraints imposed by the presence of a large group of disparate artisans (illegal miners) who now form a significant component of the Indonesian mining industry; the Bre-X debacle; the impact of the recent Regional Autonomy legislation; and changes to the Mining, Forestry and Environmental Acts. An overall view (including statistics) will be presented as to how recent Indonesian developments have affected international confidence in investing in its mineral sector over the past decade and it will be placed in an international competitive context.

Jan 1, 2004