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While convergence of plates at a subduction zone produces shortening at the toe of the overriding plate, this deformation is localized to the frontal 100 km or so of the plate. There is increasing evidence that the state of strain in back-arcs, volcanic arcs, and possibly the entire forearc is extensional. The most likely cause of this extension is rollback of the subducting plate and trenchward advance of the overriding plate. Arcs are thermally weakened, and are activated repeatedly through time. The primary expression of the extensional state of strain is spreading of the weak arc material, either by splitting the arc or by back-arc spreading behind it. This study presents evidence for extension of volcanic arcs from an analysis of the moment tensors of shallow earthquakes (

Jan 1, 1990

By Wright S

The feed to the Cockle Creek Imperial Smelting Furnace consists of mixed Pb/Zn con- centrates and lead sulphate-containing elec- trolytic zinc plant residues. Roasting was investigated as a means of desulphurizing the feed to less than 1%. Laboratory studies showed that two process streams were required in which concentrates containing 20% Pb were roasted separately from the leach residues. The residues along with fume from the roast- ing and a portion of concentrate were desul- phurized by means of the roast reduction reaction. Conditions were defined to give

Jan 1, 1986

By Whittaker B. N, Reddish D. J

This paper presents the physical modelling results of subsurface fracture development associated with Iongwall mining operations and an application of image processing techniques to interpretion of the results. Physical modelling results haióbeen obtained by employing a large sand and plaster model loaded purely by gravity as a means of fracturing the subsurface strata above the longwall excavation. The results have shown fracture development and crack propagation as a longwall face advances and demonstrated that the strength of stratified rocks, the presence and position of a weak band-, and the extraction thickness, have significant effects upon the overall fracture patterns above the excavation. Binary images of fracture patterns were scanned from the black and white photographs of the tested models using an image analyser coupled to a video camels. These images were manipulated by a custom written C program which allows the images to be processed in both vertical and horizontal direction. The images were filtered to quantitatively differentiate between vertical and horizontal fracture intensities. The vertical fracture intensity is particularly important as vertical fractures are considered to provide the main avenues for surface and subsurface water inflow into the excavation. The use of the image analysis techniques has shown a promising improvement in image enhancement and in model results interpretation in a quantitative manner. The numerical nature of the image analysis results will allow further statistical comparison with other modelling techniques to be undertaken and significantly increase the scope for use of the modelling technique results.

Jan 1, 1992

This paper describes the effects of physical variables in dewatering of mineral slurries with air as the filtrate displacing medium. Using a mathematical model with material related constants measured in laboratory dewatering curves are simulated for vacuum and pressure filtration. Four different mineral slurries are studied. Basic dewatering curves with variation in air-pressure are shown with iso-energy lines. Variables such as air pressure, feed concentration, cake thickness and cake formation pressure are discussed.

Jan 1, 1989

The Olympic Dam Mining Operation involves the supply of some 2.2 million tonnes per annum of ore feed for the metallurgical plant. To achieve this approximately 9 km of tunnels are developed per year to gain access to the long hole open stopes that supply the majority of the production tonnes.Vast amounts of data are produced in the mining activity from the geology, mine design, scheduling, surveying, shift reporting through to the statistical reporting and analysis of the performance of the mine activities. Care must be taken when obtaining the data to maximise the usefulness of the data to other users so not to impose constraints or additional processes on future users.

Jan 1, 1992

The conventional approach to the disposal of fine coal mine tailings, which involves piping the tailings as an aqueous slurry to a storage where they remain in the form of a permanent wet deposit, is becoming unacceptable. This approach is a legacy of a "contain and forget" mentality, which has economic advantages only in the short term. In the longer term, wet tailings deposits occupy large areas of land and present extreme rehabilitation difficulties. Alternative tailings disposal systems, which are sustainable and which facilitate rehabilitation, are required. The possible alternatives include the mechanical dewatering of fine tailings prior to disposal in combination with coarse reject, tailings disposal into spoil pile valleys, and the combined pumping to disposal of tailings and coarse reject. The most appropriate choice of fine tailings disposal strategy will vary from mine site to mine site. The chosen strategy should be optimised to meet increasingly stringent environmental requirements, within the constraints imposed by each mine. The alternative approaches represent significant departures from past practices, and require considerable industry driven research and development before they can be adopted with confidence. All three alternatives involve mixing of the fine tailings and coarse waste streams, aimed at creating a mixture of reasonable engineering properties. Understanding the engineering behaviour of such mixtures is central to the success of these alternative disposal strategies.

Jan 1, 1991

By Kennewell G. J

This paper aims to present the evolution of the mining method in the Prince Lyell orebody. Initial strategy and practical experience are detailed as are the reasons for and benefits of changes to the method since 1972 when underground mining began. This section of the paper starts with ten series and concludes with 40 series which was completed in 1989/90.In addition, to update the series of papers written by various authors over the past ten years on Mount Lyell, a review of the experience in the current 50 series lift of mining will be given. As well, the basic planning guidelines are discussed for 60 series - the final lift of the Prince Lyell orebody.

Jan 1, 1992

Government established and financed the NZ Steel Investigating Co in 1960. Its investigations showed that a steel industry was feasible and desirable based uponNorth Island titanomagnetite ironsands, and charted a route for its establishment. The initial processing used post-1945 preheating and prereduction developments, but later innovative improvements created what was essentially a new New Zealand technology. Of the North Island titanomagnetite deposits: the small ones at Waipipi were best made available for export; those at Kawhia and Taharoa were too remote for the economic siting of a mill; that at Raglan proved too small; while at Waikato North Head three times the requirement of 50 million tons of concentrate were located in two sand areas averaging 18 per cent titanomagnetite. Economic studies showed that a South Auckland site would be ideal, close to New Zealand's biggest market. The mill site, on a basalt flow at Glenbrook, was located by a half-day's fieldwork - near both the Waikato North Head deposit, and a railhead for bringing in Waikato coal, etc, and taking out steel products.   This development was one of several since World War II which altered significantly the lives and homes of New Zealanders (others were natural gas, oil, geothermal power, epithermal gold, aluminium, opencastable lignite, etc). All had the essential ingredients of the highest government backing, direct or indirect government finance, and first-class New Zealand scientific and engineering skills (eg to create new technologies). Not one such project failed.

Jan 1, 1993

By OÆBrien D, Priddle D

In order to avoid costly moisture penalties on coal shipments and to minimise rail freight costs, screen bowl centrifuges were selected and installed in the Mount Thorley Coal Preparation Plant for dewatering fine coal product. The Mount Thorley fine coal circuit consists of desliming the -0.5 mm (ww) fine coal in two stages of classifying cyclones prior to recovery by froth flotation. Provision has been made to bypass the flotation circuit with the classified flotation feed reporting directly to product and the centrifuge dewatering circuit has been designed to handle either flotation feed or flotation product. Major mechanical failures of the gearboxes and the ceramic tiling occurred early in the operation life of the machines which led to design changes being made to achieve satisfactory operation. This paper discusses the operating experience at Mount Thorley with respect to both mechanical and metallurgical performance of the screen bowl centrifuges since their installation in 1985.

Jan 1, 1989

By Gray J, Krouse HR, Changkakoti A, Kwak TAP

The Dachang tin field with more than one hundred million tonnes of ore at 1% tin and 3% Zn is one of the largest tin fields in the world. It comprises five carbonate replacement tin deposits, of which the Changpo deposit containing about 80 million tonnes of ore at about 1% tin is the largest deposit. The deposit, hosted by middle Devonian limestone, argillaceous limestone and black shale, is genetically related to the Longxianggei granite.The oxygen, hydrogen and carbon isotope data of minerals, rocks and fluids suggest a magmatic fluid which evolved during the crystallization of the Longxianggei granite. Mass balance calculations show that the depletions observed in 180 and 13C values of calcites from the ore bodies to the country rocks were due to continous isotopic exchange reactions between the magmatic fluid and the marine limestones at different W/R ratios and between 300 and 600¦C.

Jan 1, 1990

By Cox I

Raiseboring is a technique that has become popular in modem mining engineering since the early 1960s. A study has been undertaken at the University of Queensland to determine important factors affecting the optimum diameter of raisebored shafts, excluding local parameters such as the maximwn excavation size that a particular rock type can safely accommodate.This model is used to examine each of these factors and the results indicate that the optimum diameter for raisebored shafts is generally between four and six metres.

Jan 1, 1991

The Pike River Coalfield is located on the West Coast of the South Island of New Zealand near the top of the Paparoa Range approximately 45 km north east of the coastal town of Greymouth. The Pike River Coal Company Ltd (PRCC) is owned jointly by New Zealand Oil & Gas Limited (NZOG) and private investors.   The project has followed a long and difficult road towards project implementation which is now a reality with mine construction scheduled to commence in November 2005. The first stage of the project, the consent and land access process has been the most difficult. Resource consents for the project were first applied for, granted and appealed in 1998. A second round of modified resources consents followed a similar path in 2001. Following consultation with a range of parties including local and central government as well as the Department of Conservation, in March 2004 the Minister of Conservation granted PRCC access through Department of Conservation land. In October 2004, the Environment Court issued a Memorandum of Consent granting resource consents with conditions that had been negotiated between PRCC and the appellants.   The second stage of the project, investigation and design, commenced in December 2004 and was completed in June 2005 with the PRCC board ratifying the project capital and operating budgets. While the investigation and design work was proceeding, PRCC were also engaged in securing private equity and bank debt funding for the project. Formal Board approval to proceed with project construction was granted in September 2005 following completion of fund raising.   The project consists of a number of significant construction activities, namely: +        10.5 km of mine access road through previous logged and virgin rain forest; +        2.2 km of tunnel through metamorphic rock; +        a coal preparation plant about 8.3 km from the mine portal; +        an underground coal preparation plant; and +        a major slurry pump station, high and low pressure underground water supply systems to support hydraulic mining units and underground coal transport respectively.   Project construction is expected to be completed in April 2007 with completion of the ventilation shaft. Mine production will commence in December 2006 with coal from pit bottom development which will be carried out by the mine owner.

Jan 1, 2005

By Draper J. J, Lang S. C

Regional geological mapping and facies analysis of the Late Devonian to Early Carboniferous Keelbottom Group of the Burdekin Basin have resulted in a depositional model representing six siliciclastic-carbonate facies. The six facies represent alluvial fan, braidplain delta, siliciclastic shoreline, siliciclastic shallow marine, restricted siliciclastic/carbonate shelf, and carbonate shoal depositional environments. These facies are identified in the Star beds which are equated with and included in the Keelbottom Group in this paper. Facies are repeated throughout the Group, as a result of two transgressive-regressive cycles.The first transgression recognised in the Keelbottom Group began in the mid-Famennian, and followed deposition of the Late Devonian Dotswood Group. It was marked by the deposition of Siliciclastic Shoreline facies in the basal Myrtlevale Formation, which was succeeded by Siliciclastic Shallow Marine facies at the peak of the transgression. The return of Siliciclastic Shoreline facies in the upper part of the Myrtlevale Formation marked the onset of the first regression, which resulted in the progradation of Braidplain Delta facies from the northwest of the basin. During the peak of this regression, deposition in the western part of the basin was dominated by Alluvial Fan facies.

Jan 1, 1990

The first stage in process design for coal preparation is a study of the coal seam and its associated features followed by an examination of the mining method to.be employed and the coal market requirements. Normally benefication is based upon the differences in relative densities of the coal constituents and asso- ciated ash forming components. Since initial liberation is obtained at a relatively large particle size, the size to which coal is crushed is more subject to the market requirements than to liberation studies. It is possible to estimate energy requirements for comminution and recoveries and product grades can be cal- culated following the interpretation of standard laboratory tests. Numerous units are available for the separation and concentration of the components of run of mine coal in- cluding jigging, dense media separators, and for the finer particle size fractions, flowing film separators, dense media cyclones and froth flotation.

Jan 1, 1975

By Moore A. J

Blasting in mines in an urban environment can be conducted safely and within regulatory vibration limits by careful attention to detail and the application of correct techniques. Factors affecting blast vibration are described using surface and underground mining examples. An understanding of these factors provides an essential base for effective planning and operational control. Techniques are described for assessing and predicting vibration levels and the presentation of data for planning purposes such as environmental impact statements for new projects and the protection of buffer zones around existing operations.

Jan 1, 1997

The Permian rocks at Gympie were first studied as far back as 1868 in conjunction with the discovery of gold. The relationship of the Gympie Group to other sequences in the Gympie Composite Terrane is an important subject of investigations in a new mapping project of the Geological Survey Program of the Department of Resource Industries.In two areas the Gympie Group has been divided into four defined formations. They are the Highbury Volcanics (base), Ram mutt Formation, South Curra Limestone and Tamaree Formation (top) in the Gympie area, and the Mant basalt (base), Kolbar Formation, Gigoomgan Limestone and Teebar Formation (top) in the Gigoomgan area. Geochemical and lithological evidence from the basal volcanics of the Gympie Group (Highbury Volcanics, Mant basalt) indicate that they developed in an intraoceanic island arc setting. The overlying volcaniclastic sediments (Rammutt Formation, Kolbar Formation), which contain some continentally-derived material, are mainly of local derivation and shallow-water marine. A hiatus is present at the top of the Early Permian Rammutt Formation and Kolbar Formation. Following the hiatus, limestone sedimentation characteristic of a basin of restricted circulation developed in the Late Permian. There is some evidence of a hiatus between the limestone deposition of the Gigoomgan and South Curra Limestones and the overlying probable turbidite deposits of the Teebar and Tamaree Pnrmatinnc

Jan 1, 1990

Inefficient conveyors suffer carryback, leading to the build-up of materials on idlers, and other expensive components. They spill and leak material at loading zones and transfer points, causing accumulations that can damage the belt, wear moving components, and increase both cleanup labor and maintenance expense. They wander or mistrack, spilling material and en- dangering personnel and conveyor components, including the belt itself. And through these inefficiencies, they multiply an operation's hidden costs-the dollars lost because of missed production, of increased downtime, of the expense for the replacement of prematurely worn or damaged equipment. In this paper, the author will examine the importance of belt conveyors to mines and process plants He will trace the state-of-the-art in systems for cleaning belts, and controlling the release of fugitive material from conveyor transfer points, by exploring the roots of the problems, and demonstrating solutions that have been proven to be effective. Included in these systems to improve material handling are transfer point stabilization and sealing systems, dual belt cleaning systems, and belt training idlers.

Jan 1, 1991

The economically significant seams in the Bowen Basin fall into four age groups, two in the Lower Permian and two in the Upper Permian. Coal deposition in the Galilee Basin did not commence until late in the Lower Per- mi-an and persisted into the Upper Permian. The Lower Permian and early Upper Permian coalfields of the Reids Dome Beds, the Collinsville Coal Measures and the Fair Hill-German Creek Formation are restricted to the west flank of the Bowen Basin. The uppermost Permian Rangal-Elphinstone-Baralaba Coal Measures have widespread distribution across the northern half and on both flanks of the Basin. Coal Measures in the subsidiary basins at BlairAtho/ and Ca/en were probably deposited at the same time as the Collinsville Coal Measures. The structure of the north west flank of the Bowen and the east flank of the Galilee Basin is essentially simple, but in the remainder of the basin doming and faulting complicate the structure. Also, bordering a large sec- tion of the east flank, is the Dawson Tectonic Zone, where the beds are tightly folded and faulting is intense. Cok- ing of seams is common in the northern sector of the Basin associated with igneous intrusion. With the exception of the Duaringa Basin on the east flank of the Bowen Basin, Tertiary sediments and basalt flows are more common at the western basin margin. Thick deposits of Tertiary sediments also occur in the south of the Galilee Basin. Con- sequently, coal subcrop, especially in the older, more westerly situated, coal measures is often at depths in excess of 100 m. East of this, the depth of weathering can be as shallow as 13 m and most of the coal subcrop is acces- sible to mining by open cut techniques. Coals deposited in the early Upper Permian are commonly more vitrain rich than those above and below. In the Bowen Basin, coal rank decreases from the north west to the south east, that is, from the semi-anthracites associated with the Dawson Tectonic Zone to the sub-bituminous coals of the southern Galilee Basin.

Jan 1, 1975

By Alford R. A

The causes of the loss of heavy mineral from mineral sands wet concentrators were identified through detailed surveys of two such concentrators. It was found that tray and spiral sluices preferentially lost elongated panicles, but panicle size had little effect on loss. Recovery was shown to increase with panicle density. The major influences on the recovery efficiency of individual concentrating devices (stans) were feed rate and feed grade, recovery increasing with decreased feed rate and with increased grade. Uneven distribution of total solids and heavy mineral to individual stans contributed to losses through the corresponding effects in feed tonnage and grade. Computer simulation demonstrated that significant recovery improvements could be obtained by appropriate adjustment of splitters to optimise the characteristics of internal plant flows.

Jan 1, 1991

The potential of the developed multi-dimensional analysis system to assist interpretation from large data sets through derived digital mapping models is presented accompanied by preliminary results. The concept learning model is original and its application general. Applications exist in general science, engineering, earth resource management and economics. The developed system incorporates advances in machine learning, neural networks, object-oriented software engineering, knowledge representation and fuzzy logic. ' The specific application presented involves automatic earth resource modelling and assessment involving geological theories of mineral potential. The developed system functions as a new and powerful mineral exploration tool, To date the model has been trialled on an earth resource database and several published data sets. A more general potential application is knowledge discovery within databases. The specific theory that is tested in the experimental results is the nature of the cause-effect relationship between the hypothesised geological causes and the measured effects within a previously published test survey. Also integrated here are a neurophysiological cerebellar model of human learning, a new concept similarity measure for pattern recognition, modelled components to explain human concept formation through knowledge discovery and a means of permanent representation.The implementation is as a new artificial neural network architecture functioning as a hybrid expert system. Understanding of programmed concept learning is extended through the model. Also established is a basis for a new approach to multivariate data analysis. Spatial analysis for decision support is integrated over many dimensions, relationships, data types and data modes. Application of the developed methodology and system adds value to data bases. Discovered knowledge is represented as new generalisations, interpolations, classification hierarchies, aggregations and associations within a dynamic, maintainable and reusable integrated knowledge framework. New digital knowledge products and intelligent access follow. Permanently stored, maintainable, easily accessible and discovered knowledge improves decisions through extended hypothesis testing, spatial data analysis and inferencing, prediction, logical deductions and explanations.

Jan 1, 1995