Search Documents

This paper provides an update to a paper by the author on an overseas explorer's perception of New Zealand, presented at the 1997 New Zealand Minerals & Mining Conference. New Zealand has one of the most open and internationally competitive economies in the world. The petroleum exploration industry in New Zealand is booming with a record number of wells planned for 2000. New Zealand is keen to encourage investment in mineral exploration to develop its natural resources. A study of the geological potential of New Zealand estimated the value of known and potential resources of metals at $86 billion. Gold has the greatest potential, with a total resource estimated at $33.5 billion. The price of gold has averaged NZ$554 since the beginning of 1998, and NZ$593 in the last year, which is very competitive with other countries. An assessment of country risk compared New Zealand with twenty other countries in ten risk categories: sovereign risk, land access, environmental issues, land claims, mining legislation, social risk, infrastructure, civil unrest, natural disasters and workforce. New Zealand ranked fifth, showing it has low country risk. This provides a high degree of certainty for investment, which is important for the perception of New Zealand as an exploration destination. Corruption was considered separately, and New Zealand ranked third out of ninety countries, showing it is one of the least corrupt countries in the world. New Zealand has a favourable business environment, good geological potential, low country risk and no corruption. Despite this, New Zealand has not registered on the radar screens of overseas mineral explorers, and the positive factors appear to have been overlooked. New Zealand has considerable undeveloped mineral potential, and with the current rise in commodity prices, it is hoped New Zealand can participate in a resurgence in mineral exploration.

Jan 1, 2000

By William R. Yernberg

The “China & East Asia Mineral and Energy Re-sources Symposium — CEAR 2000” was held Jan. 23-26, 2000 in Denver, CO. Conference sponsors included Resources and Technology Symposia of Colorado and the Asian Journal of Mining. The meeting was attended by representatives from China, Japan, Mongolia, Korea, eastern Russia (Siberia) and the United States. The US attendees consisted of interested parties from mining and energy companies, financial institutions, consultants and government agencies. In his opening statements, L. Maness, Jr., president of Resources and Technology Symposia of Colorado, said that the “goal of the conference was to make jobs and friendships and to introduce people to each other.” The conference provided an opportunity for Western mining interests, including mining companies and investors, to meet with government agencies from both sides of the Pacific.

Jan 1, 2000

By D. W. Wu, M. T. Haque

A novel impedance probe has been commissioned specifically for capturing fast dynamic information about filtration processes. It provides an attractive alternative to more complex measurement techniques in situations where the slurry system is primarily one-dimensional. The probe can monitor mud-line, slurry densification and drainage. Dynamic variations in cake permeability are obtained by combining dynamic mud-line information obtained with the probe and filtrate rate data derived from a leaf test apparatus. The measurements are re-viewed in relation to micro structural measurements obtained on iron ore filter cakes. The practical significance of these measurements for optimization of the filtration process is discussed.

Jan 1, 2000

By R Crookes

Mine to Mill optimisation is not a recently developed concept. It is one which is finally gaining greater acceptance in the Australian Mining Industry, possibly as a consequence of the downturn in markets and certainly made possible by the development of tools and techniques to measure and predict performance of mining equipment and milling plants. Fragment size after blasting has a major bearing on the performance of all aspects of mining and a major influence on the economics of the mine and mill. The process to optimise fragmentation consists of identifying the key factors, measuring their sensitivity through a modelling and trialing program and conducting economic evaluations on the changes on both the mine and mill. Management of the Ernest Henry copper-gold mine in NorthernQueensland, Australia, has espoused the Mine-to-Mill concept and isactively pursuing excellence in blasting to drive down the total cost of mining. Ernest Henry has extremely hard, wet and heavily jointed geological conditions, and had high powder factors and a large percentage of oversize material reporting to the crusher or ROMstockpile. A blasting improvement program was undertaken betweenErnest Henry Mining, Thiess Contractors and Orica Explosives tooptimise the ore size distribution, particularly the oversize component, as a step to reducing production costs. Measures of success included bringing the rock breaker back from double shifts to part-time operation and increasing direct dumping into the crusher from 70 per cent to 92 per cent. Tools and technologies to predict and measure the performance ofindividual blasts are needed before it is possible to optimisefragmentation or the downstream processes. These include suchspecialised Orica Explosives tools as SABREX, POWERSIEVE, andPOWERLINE and commercially available drill monitors. As importantare the more common still and video camera, borehole loggers,measuring tapes, surveying equipment such as face profilers, and ahigh-speed camera if possible. There are many tools which can be applied however it is rarely necessary or possible to use all of them due to time constraints and a point of diminishing returns. The critical point is knowing what the true parameters of the blast were compared to design - only then can the predictive tools be effectively utilised. Stage one of the program has seen gradual improvement as theunderstanding grew and practices have been implemented resulting inreduced bridging in the crusher, geological mapping with respective blast designs and the oversize component under control. This paper is about a process approach which links tools and technology to understand the fragmentation drivers and then to optimising the size distribution.The continuous improvement program continues...

Jan 1, 2000

By L. A. Cramer

Platinum metal was first utilized by the Inca civilization in South America where it was found in alluvial deposits along the San Juan and Atrato rivers that lie between the Andean mountain range in Colombia and the Pacific Ocean. The nuggets found in these rivers average between 77% and 86%platinum, 7%?8% iron and small amounts of copper, gold and other Platinum Group Metals (PGMs). The Incas often alloyed platinum with copper to increase its workability and fabricated various ornaments from it. With the arrival of the Spanish in the early 1700s, platinum was labelled a nuisance for the Spanish in their quest for alluvial gold because it concentrated with the gold and had to be removed by either extended amalgamation or by hand sorting. It was at this time that platinum received the root of its current name for the Spanish referred to it as platina del Pinto, platina being the somewhat derogatory diminutive of plata (silver). Pinto was a river in Colombia where the Spanish first distinguished it. The English eventually adopted ?platina? and it is only in recent times that the Latin name platinum has been accepted as the metal?s common English name. From its first introduction to European scientists in 1740, platinum was unappreciated because of its brittle nature and difficulty of working and as a result had little commercial value. Its ability to be dissolved in gold did lead to some counterfeiting of gold bullion and even to the debasement of gold currency.

Jan 1, 2000

By A. Z. Toper

This is a sampling of the papers presented at the conference, the proceedings can be bought from the SAIMM An extensive research programme to address the issue of rockburst control has been undertaken over a number of years. This paper discusses the development of preconditioning techniques to control face bursts, for safer mining in seismically hazardous areas. Preconditioning involves regularly setting off carefully tailored blasts in the fractured rock immediately ahead of a mining face, so as to encourage slip on pre-existing fractures, in order not to allow the accumulation of high strain energy density in the rock mass. Two different preconditioning techniques have been developed, namely face-perpendicular preconditioning and face-parallel preconditioning. Both have prevented face bursting in areas to which they have been applied, even though several large seismic events have occurred close to the faces in some areas. In addition, minimal overall damage was observed in the preconditioned panels following these events, compared to similarly exposed unpreconditioned panels. Preconditioning has also provided some protection to the face area from distant events, through the capacity of the preconditioned ground to absorb energy. An improvement in hangingwall stability and productivity has also been noted in preconditioned areas. In order to determine the optimum blast parameters for achieving the most effective preconditioning, an extensive optimization study was carried out for the face-perpendicular preconditioning technique. While optimum values for parameters such as hole length, diameter and spacing were determined, it was ultimately concluded that the differences in results obtained by varying the preconditioning parameters were less significant than the clear positive differences observed when comparing preconditioned areas with non-preconditioned areas.

Jan 1, 2000

By J. Luxford

The last decade has seen an enormous increase in the use of contractors right across the Australian mining industry. So much so that contractors now operate 33 of the 68 underground metalliferous mines around Australia and are making significant inroads into iron ore in the west and coal in the east. Safety used to be a low priority for many contractors. The picture has changed dramatically in recent years as most contractors take a far more professional approach to safety management. This paper examines the changes that have occurred and the requirements for effectively managing safety in a contracting environment.

Jan 1, 2000

By Allan E. Koski

Ceveland-Cliffs uses a specialized software package in mine planning at the Empire Mine, an iron ore mine it manages on Michigan’s Marquette Iron Range. The application puts together years of mining experience that began in the early 1960s on the eastern end of the Marquette Range. The Empire Mine is in its 38th year of production. It uses the software to model a complex and highly variable low-grade magnetite ore body, capturing the economics of mining and processing to the final product. With special attention given to geostatistical methods, the software is used for all geologic modeling, ore reserve estimation, ore control, pit design and short- and long-range planning.

Jan 1, 2000

By José A. Rios, José A. Vidalôn

The case study of a highland area in the Central Andes of Peru, where many abandoned polymetallic mines are found, is presented. Some of these mines generate metal leaching and acid rock drainage (ML/ARD) or have potentially ARD generating (PAG) tailings/waste rock storage. Effluents are discharged into the first of two lakes in line, which act as reservoirs for irrigating an important valley in the desert coastal region. Drainage fees, their relationship with the deposit and the solid-wastes mineralogy are discussed, as well as variations in water and sediments composition, the benthos, and the aquatic/riparian flora/fauna in these lakes.

Jan 1, 2000

By Nathaniel Arbiter

Flotation’s earliest patent was issued in 1860. However, the process was first applied commercially in Australia until 1904, and in Montana in 1911. Major advances followed both in reagent treatment and in cell design, with resulting process improvements. Mechanical cells have seen the widest use and with the major increases in plant capacities (Fig. 1) their volumes have also increased (Fig. 2). In 1991, the principal use for the process was to produce copper concentrates for smelting. It was applied to 243 Mt (268 million st) of copper ore. The total of all ores floated that year was 426 Mt (470million st). In 1997, US mines produced 257 Mt (284 million st) of copper ores for flotation, yielding1.75 Mt (1.94 million st) of copper.

Jan 1, 2000

Syncrude Canada produces a large part of Canada’s crude oil supply. The company processes about 225,000 bbl/day. The oil produced is used for jet and automobile fuel, home heating oil, plastics and other consumer synthetics. Crude oil is produced through a process of mining, extracting and upgrading bitumen. A rich supply of bitumen is contained in the Athabasca oil sands deposit in northern Alberta. Tailings from the bitumen processing are sent to a settling basin.

Jan 1, 2000

By Melvin I. Esrig

Lime Cement column stabilization of soft clay and sand in Salt Lake City, Utah and in San Francisco California is described and discussed. Stabilization permitted the construction, in a single stage, of a 14 m MSE wall on "medium" clay in Salt Lake City. It was used to mitigate the potential for liquefaction in San Francisco and to stabilize the Young Bay Mud beneath the BART extension to San Francisco Airport. These applications are described and the field measurements of performance are reported.

Jan 1, 2000

By N. S. Yet

This paper shall present the design and construction of bored pile and diaphragm wall for the proposed MHA complex in Singapore. The work was carried out by L&M Foundation Specialist Pte Ltd and PWD Consultants Pte Ltd was the consultant for this project. A brief description of the project is first presented to illustrate the scope and scale of the work involved, which includes the construction of bored piles and diaphragm walls and installation of steel stanchions in the bored piles. This is followed by a description of the methodology used to analyse and design the wall and bored piles. As both towers in this project are supported on bored piled foundation and are constructed by top down construction method, the analysis of the wall has taken into consideration the sequence of work phase by phase and this was carried out by means of a commercial finite element program called CRISP. Modelling of the problem will be briefly described and the findings from the numerical analysis will be presented. This is followed by a description of the structural and geotechnical design aspects of bored piles. The paper shall then describe the difficulties encountered for this project and solution used to solve the problem. The subsoil condition will be described with special mention on the encounter of very strong granitic rock at depth above the maximum excavation level of the basement at certain locations, hence necessitating the drilling of rock for a considerable depth for both bored piles and diaphragm wall. At this juncture, the construction method used to drill through the rock will be briefly described. For construction of bored piles, penetration of rock was carried out by chiselling or drilling using reverse circulation rigs. For construction of diaphragm wall, it requires the employment of Bauer hard rock cutter which uses cutting wheels fitted with roller bits and are capable of excavating into granitic rock of compressive strengths more than 100 MPa.

Jan 1, 2000

The excavation of ramps and tunnels often requires high-speed development with (or without) the use of high-energy mining equipment such as loaders, dump trucks, TBMs and roadheaders. This high-speed development creates a challenge in terms of providing a safe and productive working environment. For example, heat from continuously exposed surrounding rock, heat from broken rock, heat generated by mining equipment, potential in flows of hot ground water, pollution from associated diesel equipment and the distance of the advancing face from fresh through-ventilation all have to be taken into account when designing ventilation systems for high-speed ramp and tunnel developments. This paper discusses methods of achieving acceptable environments at the face and along the length of the tunnel. The methodology has been successfully implemented in the development of long (up to 20 km) TBM drives in the Lesotho Highlands Project and in mining projects in hot rock using drill and blast methods as well as mechanized methods using continuous miners and roadheaders. The determination of heat loads includes calculation of the heat flow within the surrounding rock, evaluation of the operating cycle of the equipment and the contribution to the overall heat load of the broken rock as it travels out of the tunnel. The determination of heat loads from surrounding rock in new tunnels required a modification of the algorithms generally used for established excavations. The paper also examines the use of, for example, mobile duct and fan systems to ensure that fresh air is delivered to the specific areas where workers are located.

Jan 1, 2000

By J. A. Flinn

Phelps Dodge’s Morenci copper mine has had six drills, six track-dozers, 16 shovels, two loaders, and 90 haul trucks equipped with either Caterpillar, Aquila, or Modular GPS systems for nearly three years. The Caterpillar Computer-Aided Earthmoving System is an open-architecture system, which allows for inputs to enhance orientation solutions and system functionality. This system has begun a new phase that leads to an intelligent mining system. Optimization techniques of the current system and inputs are reviewed. In addition, some practical issues of implementing new technology in a mining environment have been identified to aid in this new phase.

Jan 1, 2000

By Rajive Ganguli

There are several elements of online pedagogy and information technology that are being used in the University of Alaska Fairbanks’(UAF) course “ES 201: Computer Techniques,” to enhance classroom teaching. The use of information technology in this class grew from a desire to make lecture notes available to students. This has grown to include a sophisticated, online delivery software package. It provides chat rooms, discussion groups, and online testing and grading. Online delivery aside, the class uses the telnet, e-mail and C++/FOR-TRAN compiler facilities of the university server during class to enhance learning. During class, for example, the students read the lecture notes on the Web browser, telnet to their university Unix accounts, check their e-mail and download programs (to be covered in class) sent by me, and then compile, run and modify the programs. The class, therefore, requires students to be active most of the time. This ensures their full attention and better learning due to the hands-on experience (Fig. 1).

Jan 1, 2000

By L. C. Stilwell

Input-output analysis is a major branch of quantitative economics, and is used to analyse the flow of goods and services between production sectors in a national economy. Its purpose is to determine the relative value-adding capacity of each sector. The model has also, in recent years, found increasing use in assessing the environmental and ecological impact of development projects. It has, however, never been applied to individual production facilities, such as large mines, which themselves have complex economic structures, through which there is a flow of goods and services. Conventional cost and accounting systems, as used on mines, treat production sectors as separate cost centres, and do not determine the inter-relationships between them. This can lead to incorrect conclusions on the relative value of sectors and their impact on the total economic performance of the facility. This paper explains the basic principles of input-output analysis, and presents an example of its application to a simplistic model of a mine, which is used in the absence of any real data. The paper concludes that, by forcing definition of the value adding function of each sector, input output analysis will facilitate control of inputs, or costs. This will result in optimal application of resources and exploitation of ore reserves. The authors realise the model needs to be tested on an operating mine, and hope this paper will result in an opportunity to do so. The authors wish to thank the anonymous referees for their valuable comments.

Jan 1, 2000

By M P. Simpson, J L. Mauk

The Golden Cross, low-sulfidation, epithermal deposit shows a number of features that are directly or indirectly related to boiling hydrothermal fluids. Occurrences of lattice calcite and their quartz pseudomorph equivalents in veins, and occurrences of adularia in veins and in the surrounding altered rocks in the vicinity of ore, are both direct evidence of deposition in the presence of boiling hydrothermal fluids. Loss of carbon dioxide causes calcite deposition (platy variety) near the level of first boiling, while adularia deposits due to the attendant pH increase along the cooling flow path. Indirect evidence of boiling include crustiform-colloform quartz banding, late massive calcite veins, clay-carbonate alteration in the shallow and peripheral parts of the ore zone, and the restricted vertical interval of precious metal mineralisation. The colloform quartz banding strongly resembles the banding in amorphous silica deposits found in geothermal surface pipes. This implies that fluids ascending the Empire Vein structure were saturated in amorphous silica. If so, then they must have undergone phase separation, which initiated at considerable depth (e.g. =1000 m) and very hot temperatures (e.g. =300¦C). On the basis of stable isotope data, late massive calcite veins appear to have deposited from CO2-rich steam-heated waters. Calcite deposited along heating paths as these waters descended into the upflow zone during late stage collapse of the hydrothermal plume. In active systems, such steam heated waters form by deep boiling. The high CO2 contents of these waters promote hydrolytic alteration and the formation of clay-carbonate alteration. Reaction path modelling using CHILLER and a deep, Broadlands-Ohaaki water as an analogue, shows that minerals deposit along boiling flow paths over discrete spatial intervals. Calcite and adularia deposit near the site of first boiling, followed by gold and then by amorphous silica. For deep boiling starting at 300¦C, these minerals deposit over a path length that exceeds 1000 m. The distribution of banded quartz and gold at Golden Cross are consistent with such a boiling model. However, the elevation of first boiling must have fluctuated over 500 m to account for the coincidence of lattice quartz (pseudomorphs of platy calcite) and adularia, crustiform-colloform silica and gold over distances of a few centimeters in veins. We deduce that a downward propagating boiling front and expansion of two-phase flashing in a flowing water column occurred during episodes of high vertical permeability and fluid flux in the Empire vein structure.

Jan 1, 2000

Traditional fine grinding mills in mineral processing relied on the use of steel medium for particle size reduction. The successful development of the Isa Mill(a horizontal stirred mill with 3000 litres of net chamber volume and 1120 kW rated motor power)adopted a novel product separator design that has led to a major revision of medium use in fine grinding. The Isa Mill separator has also successfully operated with a wide variety of medium types such as silica sands, river gravel, smelter slag, run-of-mine ore fractions and steel shots, with size ranges from 0.5 to 10 mm. A great flexibility of the Isa Mill operations has been achieved for processing a feed as coarse as 120 um to a product as fine as 5 µm. This paper discusses the performance of two inert grinding media used in the Isa Mills in Mount Isa Mines of Australia for processing galena and sphalerite bearing ores to below 10 microns. They are the copper reverberatory furnace slag (CRFS)and the heavy medium plant rejects (HMPR). A methodology was also demonstrated for comparing the medium performance and for scaling up the Isa Mills from a 1.5-litre laboratory batch mill to a full scale 3000-litre mill.

Jan 1, 2000

By Claude Deveau

"With ever decreasing feed grades, finer mineralogy and increased demand for product, it became obvious that a major step in equipment performance was required to reduce operating costs and increase production. Offsite testwork indicated that a Centrifugal separator was capable of recovering fine tantalum and that the newly developed C Series Falcon concentrator would be capable of replacing many pieces of aging equipment and provide improved performance. Further investigation led to the rental and the purchase of a Falcon C20 concentrator followed by a C10 to maximize circuit performance.Falcon Concentrators Inc’ s practice of working with the customer mirrors Tantalum Mining Corporation of Canada’s (Tanco) philosophy of continuous product development. This synergy honed valve design for continuous operation in a highly abrasive ore environment.Tanco has recently purchased two more Falcon concentrators for the recovery of additional tantalum from its spodumene circuit. These new units have additional user friendly operating features partially based on developments made at Tanco.The Falcon C Series units have enabled Tanco to maximize recovery of tantalum that was otherwise lost while using the original conventional gravity circuit."

Jan 1, 2000