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By T Wettainen, G Shekhar, M Stromsten, B Skawina

The aim of a transportation system in an underground mine is to move the rock masses from one location to another in the most preferable manner by minimising the long and short-term operational costs. A continuous improvement of material transportation systems used in mines generates a need for continuous investigation of the current and new underground transportation systems. In an underground mine, an orepass is a common system used to transfer the material to the lower levels. If this system loses the ability to transport or store the necessary material capacities, it would result in production disturbances. In this paper, discrete event simulation (DES) was utilised to analyse the material inflow and outflow of the orepass systems when subjected to the different conditions. The study presented in this paper is based on the Malmberget mine, the second largest underground sublevel caving (SLC) iron ore operation in the world.

Mar 15, 2021

By P Brown, M Nagarajan, A Green, P Dare-Bryan

Coal loss is an important issue at many coalmines, with losses of five per cent being common. The type of loss varies from mine to mine but is dependent on mine strata, the drilling and blasting processes applied and the mining method used. Typical coal loss mechanisms from the drill and blast process are coal roof damage and edge loss. Usually a reduction in coal loss is in direct competition with the need to provide material that is well-fragmented and a muck pile that has the required cast percentage. These competing issues were addressed over a two-year period at a mine in the New South Wales Coalfields by implementing a five-step approach. This was centred around building an understanding of the coal loss mechanisms utilising proprietary heave- modelling software, measuring coal losses by comparing survey to drill and/or gamma logs and implementing appropriate coal loss reduction processes. The end result exceeded expectations with a 95 per cent reduction in coal loss. Mine excavation productivity was maintained and coal loss minimised to less than one per cent of the in situ coal block.CITATION:Nagarajan, M, Green, A, Brown, P and Dare-Bryan, P, 2015. Managing coal loss using blast models and field measurement, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 429–436 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By L Cain, C Every, S Mirlatifi, J Ashley

This paper presents a geographic information system (GIS) based method for the prediction of ground movement and the associated impact on existing buildings and structures due to tunnelling in the North West Rail Link (NWRL) project. The NWRL is a priority rail infrastructure project for the New South Wales (NSW) Government and includes 15 km of twin tunnels between Bella Vista and Epping, which will be Australia’s longest rail tunnels. The NWRL tunnels will be constructed in an urban environment where the prediction of ground movements induced by tunnelling and the associated impacts to existing structures must be assessed in the early design stages of the project. An assessment process was developed using GIS able to respond to design changes.An iterative GIS analysis methodology was developed to generate ground settlement contours and identify impacted buildings and structures in response to multiple changes in tunnel alignment during design development stages. The GIS analysis undertook to rapidly provide detailed and accurate parameter information including tunnel depth from surface, tunnel separation, diameter and sample point proximity to the tunnel and assess ground movement contours along the project alignment. Determination of the ground surface settlements were based on empirical methods proposed by Peck (1969) and Mair (1993). The control parameters and the relationship between damage categories and risk classifications for impact assessment were based on Burland, Broms and de Mello (1977), Rankin (1988) and Boscardin and Cording (1989) methods.The GIS-based ground movement impact assessment approach adopted for the NWRL project demonstrates an efficient, iterative and robust approach and could provide an initial framework for other similar tunnelling projects where rapid design changes and early understanding of tunnelling impacts are required to bring greatest benefit to all stakeholders.CITATION:Mirlatifi, S, Cain, L, Ashley, J and Every, C, 2014. An iterative geographic information system based approach for the assessment of tunnelling impact to existing buildings and structures, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 647–652 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By K George

The Dugald River lead-zinc-silver deposit is located approximately 60 km north-west of Cloncurry and 87 km north-east of Mount Isa. The development project is expected to turn operational in 2018. The resource is estimated to contain 61.1 Mt at 12.6 per cent zinc, 1.9 per cent lead and 34 g/t silver, with a projected mine life of 25 years. The evolution from exploration project to development project has presented multiple challenges for the technical team. Understanding and modelling the structural complexity of the deposit has been one of these challenges.Historically fault zones were logged as a lithology, with structural measurements recorded in a separate database table. When underground drill programs and development commenced in late 2012, it was recognised the deposit was more structurally complex than had been modelled. The extensive number of fault zone lithologies in core logging, made it difficult to identify fault trends and model faults in 3D software packages.In 2014, a structural project was conducted to produce a fault model for the deposit. The project highlighted that by logging the faults as a lithology, a shortage of fault characteristics was being recorded. Additionally, structural information could not be filtered to identify different fault sets due to the lack of information available to filter on. One of the major outcomes of the study was to change the methodology for the structural logging of drill core.Faults are now logged in a separate structural log. The structural log collects two types of information: interval data and point data. The interval data represents the damage zone of the fault in the surrounding rock and the point data the plane of movement for the fault. The faults are further characterised by their intensity on a scale of one to five, the type of fault structure (fault breccia, fault vein etc), the minerals present on the fault surface and structural measurements when available.The new data set allows fault data to be filtered based on fault characteristics, making implicit and explicit modelling of the faults more timely and accurate. The data set can be used to produce fault wireframes as single surfaces from the point data or hanging wall and footwall surfaces from the interval data. The logging method and how its applied in fault modelling form the focus of this paper.CITATION:George, K, 2017. A new approach to logging and modelling faults at the Dugald River Pb-Zn-Ag deposit, North West Queensland, in Proceedings Tenth International Mining Geology Conference 2017, pp 315–320 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By P Andersson, P Marklund

Evaluation of different techniques for bottom fill stabilisation showed that frozen fill was the most economical method. In order to test the method a full-scale field test was performed in the Rehnstr÷m mine. The test was instrumented with temperature gauges and extensometers. Before the field test, frozen fill was tested at the laboratory. The mechanical properties of the frozen fill were determined by uniaxial compression and creep tests. A deformation model for the frozen fill was set up. Calculation procedure for design of spacing between the freezing tubes, time for freezing and calculation of the necessary capacity of the refrigeration plant was developed. These procedures were calibrated against the field test. The results of these investigations allow the following conclusions: From a mechanical point of view, frozen fill has excellent properties as a structural member and it also has excellent properties to support itself and the fill above. Methods for the thermal and mechanical design of freeze stabilisation have been developed and found adequate. The need to place the freezing tubes several years in advance of the future sill pillar mining, requires careful long-term planning and accurate documentation.

Jan 1, 1998

By M Chen, Q D. Gao, Y G. Hu, P Yan, W B. Lu

The safety and stability of construction structures are often affected by blast-induced waves. Investigating the generation mechanism of shear wave (S-wave) during blasting is important, because it has a strong effect in blasting damage. In this paper the generation mechanism and verification of S-wave was studied analytically and numerically. Under the finite velocity of detonation (VOD) of cylindrical charge or the compression wave (P-wave) communicating with the interface of different media during the propagation, the generation mechanism of S-wave was analysed. Propagation of blasting wave in cylindrical charge was simulated with the elastic model, and the generation of S-wave induced by finite VOD was proved. To compare with different numerical methods in simulating the generation of S-wave, the blasting process of instantaneous detonation was simulated by using the elastic model, elastic-plastic model and smoothed particle hydrodynamics and finite element method (SPH-FEM) coupled model. Results demonstrate that the S-wave could not be found in middle section of the charge if the elastic model is employed. But when using elastic-plastic model and SPH-FEM coupled model, the generation of S-wave could be verified. Under the SPH-FEM condition, the amplitude of S-wave is larger and the arrival time difference between P-wave and S-wave is closer to theoretical results.CITATION:Gao, Q D, Lu, W B, Hu, Y G, Chen, M and Yan, P, 2015. Comparison of the generation of shear wave with different simulation approaches, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 79–88 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By E A. Gunn, J Zhou

In this paper a project to develop a joint optimisation/simulation model for production planning in a mine-mill complex is presented. The system involves a mill receiving ore from a number of different locations, each with a unique mineral composition. The mill consists of several crushing and grinding circuits that function in series and parallel. Scheduling the flow of materials through the mill is complex due to constraints on throughput imposed by the millÆs design, the length of time material can be stockpiled on the surface, varying input mineral composition, and throughput targets for a range of output products.An optimisation model is used to create a set of campaigns (ore feed rates) over a given planning horizon under the assumption of deterministic mill throughput. A simulation model is used to evaluate the production plan under assumptions of stochastic machine failure and operational losses created by the need to cycle between input feeds. Campaign scheduling has two important implications for the simulation. First, during any campaign, multiple ore types may need to flow through the mill. However, the mill must be controlled to ensure that only one type of ore can be in a crusher, a grinder or a storage bin at any point in time. Second, as the mill switches from one campaign to another, the set of ores being processed may differ. Thus, the flow of ore through the equipment during a campaign changeover must be controlled to ensure that one or more of the ores from the current campaign can be completely eliminated before the ores from the new campaign are introduced.The simulation architecture employed for this project is Visual Basic for Applications (VBA) combined with MS-Excel as a user interface. A fixed step discrete event orientation is assumed as the simulation framework. A set of model constructs was built for the project with a specific Canadian milling operation in mind, but was designed to be representative of a broad class of milling operations. The constructs are implemented as class objects within the VBA structure, each with a number of properties and methods. The collection of VBA objects forms a composable modelling toolkit. These objects can be linked together by users, via MS-Excel, to represent a broad range of milling operations.

Sep 26, 2011

It would be a good thing when reviewing the challenges to be faced by the Australian gold industry to set the backdrop and scene for them, by briefly examining the history of this vital and dynamic industry in the Australian context. Gold mining in Australia had its official beginnings in 1851 when John Lister and William Tom discovered gold at YorkyÆs Corner, later renamed Ophir by Edward Hargraves. From that first tentative beginning, the ensuing rush of prospectors into New South Wales and Victoria meant that the annual gold production in those early years surpassed that of the next 40 years. This early rate of production was only eclipsed when AustraliaÆs production was once again lifted by the discovery of gold on the other side of the continent, in Western Australia. (Figure 1). The years leading up to the First World War saw Australian production peaking once again at over 115 tonnes of gold, a production rate that would not be surpassed until 1988. This renaissance in production at the beginning of the 1980s was achieved by the application of technology. The advent of bigger trucks and shovels meant that earth-moving costs dropped dramatically. This, coupled with the highly effective and efficient carbon-in-pulp processing route, stimulated the Australian gold mining industry into a state of frenetic activity. These two innovations were the principal factors that enabled the economic exploitation of the lower grade haloes left by the æold-timersÆ around the deposits exploited at the beginning of the last century-no high finding costs here. AustraliaÆs production through the 1980s and the early part of the 1990s was largely supported by the exploitation of these haloes. As these were depleted, the aggressive exploration effort stimulated by the strong cashflows of these early oxide deposits resulted in new æblindÆ discoveries which are now emerging as the backbone of the Australian industry (Figure 2). Gold production is a major contributor to the Australian economy. In 1998/99 the Australian gold industry accounted for approximately 16 per cent of the value of all mineral exports, which in turn accounted for over 35 per cent of AustraliaÆs total exports. As such, the Australian gold industry, by itself, accounts for just under six per cent of AustraliaÆs total exports (Figure 3). Consequently, the industry is responsible for over one per cent of AustraliaÆs gross domestic product. These statistics are all the more compelling when we consider that, at the beginning of the 1980s, goldÆs contribution to exports and GDP was insignificant (Figure 4). Within the Australian resources industry, gold mines and associated infrastructure account for ten per cent of all capital expenditure (Figure 5). From an employment point of view, in 1997/1998 the industry directly employed (excluding contractors) about 7700 people, approximately 15 per cent of all those employed in the minerals industry. Just under nine per cent of the workforce in the minerals industry are female, whereas in the gold industry over 16 per cent are female.

Jan 1, 2000

By A G. L Pratt

Inclined troughed belt conveyors are more frequently being selected from a range of alternatives, which include shafts and trucks for ore haulage in underground mass mining projects. Belt conveyor haulage systems are being operated with lifts exceeding those normally associated with truck haulage systems and approaching the limits of shaft haulage systems. A belt conveyor haulage system, in this context, incorporates subsystems for: crushing,tramp detection and removal, andhaulage. This paper presents details of recent inclined troughed belt conveyor systems for underground mining operations, and explores the application of inclined troughed belt conveyors for the increasing demands of future underground mass mining projects.

Jan 1, 2008

By D Reid

Run-out analyses of tailings storage facilities are typically undertaken using methods based on rheological theory. These are reasonable techniques to model the behaviour of tailings that, through significant run-out and possibly mixing with supernatant water, are generally acting in a fluidised manner. Such modelling often follows on from two-dimensional continuum analysis models where, if failure is predicted, grid failure often occurs when deformations begin to increase. This results in a disconnect between the prediction of failure and the modelling of the potential extent of the failure.Recently, rezoning methods have been incorporated into commercially available two-dimensional soil mechanics deformation codes. Rezoning techniques enable large deformations to be modelled within a two-dimensional continuum analysis framework; however, while promising, the use of such tools is not yet widespread, and a consensus is yet to develop on how they should be applied to tailings dam run-out modelling.This paper uses FLAC rezoning techniques to model the flow behaviour of two historic tailings dam failures. The purpose of these analyses is to critically assess the performance of rezoning against some available historic failures. The required data to undertake such an analysis is outlined, along with the inherent limitations and assumptions required. Parametric analyses are outlined to address some of these issues. In general, the analyses undertaken underestimated the flow distance observed in the historic failures by varying degrees; however, in some instances, the analysis reasonably reproduced the qualitative shape of the initial failure zone. A variety of potential reasons for the discrepancy between historical observations and the models undertaken are provided.CITATION:Reid, D, 2015. The use of rezoning techniques to model historic tailings failures, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 201–206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By P Willems, J B. Crow, R Dale

Open pit mining commenced at Lihir Island in 1997 and is undertaken using a conventional drill, blast, load, haul methodology. Unique challenges at the operation include an active geothermal system, a well-developed advanced argillic blanket in the upper portions of the orebody and high rainfall. Grade control is effective utilising routine blast cone sampling. While this provides ‘just in time’ grade information for mill blending, there are opportunities to improve scheduling of mill feed, based on material classification of clay types and sulfur grades. The nature of the clay can impact on the handling properties while the sulfur grade is an important guide for autoclave blending, required for refractory gold. Drilling below the pit floor introduces hazards from the identified geothermal field. A trial Reverse Circulation (RC) program was implemented with the aim of defining four benches below the active mining bench. A comprehensive risk analysis, including the geothermal environment, was undertaken to design a drill collaring procedure with pressure diversion equipment. Operator exposure was minimised through ‘nil on foot’ principles with the driller located in an onboard cab, utilising remote rod handling. Sampling personnel operate in an elevated platform with access to protective covering. Samples from blastholes and the RC holes are processed at two site laboratories. One provides conventional Au fire assays with additional Infrared Combustion (Leco style) S analysis. The second laboratory collects material classification details from portable XRF (pXRF), near infra-red spectrometry (ASD) and Hardness Indicator Testing (HIT). An existing workflow was updated by the site to deal with the additional samples and ensure production ‘turn around times’ were retained for short-term planning. This required some changes to drying temperatures, compositing and screen sizing for the material classification. All results from the two laboratories are loaded into a centralised acQuire database for estimation into a single block model that informs the 13 week medium term planning (MTP) schedule. This paper describes some of the logistical issues faced when drilling in a geothermal area. It also discusses the selection and commissioning Quality Assurance of the sampling equipment and drill rig. Integration of the resulting assay data with existing resource models is also explained.

Mar 22, 2022

By Sullivan T. D

The Lochiel Deposit is a large occurrence of soft brown coal about 130 km north of Adelaide. The deposit is undergoing continued evalua- tion of which an integral part was the excavation of a Trial Pit. The Trial Pit was deemed necessary to demonstrate that the deposit may be mined efficiently by draglines and the particular emphasis was on the geotech- nical and hydrogeological aspects of what may be termed difficult mining conditions. The dewatering of the Trial Pit was commenced in September 1986. After considerable planning and excavation was successfully completed in May 1987. The project is unique in terms of its size and technical com- plexity. It entailed excavation of over 230,000 m3 of overburden to an overall depth of 36 metres. The excavated material was utilised for experimentation in a Trial Dump. Included in the Trial Pit design were several novel techniques includ- ing depressurisation drains to improve mining conditions in soil strength materials and the use of vacuum to aid dewatering.

Jan 1, 1988

By W Zirima

A detailed, mine scale non-linear numerical model of Rosebery mine has been built for the purpose of simulating life-of-mine global deformations. The model was calibrated using observations of displacement and damage, and was then used to investigate the correlation between dissipated plastic energy (DPE) and seismic event occurrence. The study is unique because the seismic data was collected over a relatively short period using a temporary portable seismic system. It is the intent to undertake significantly more work, but the analysis of limited data shows that a very good, non-linear relation between DPE and event probability is present. The observed correlation is consistent with measurements from other mines where more data was available. With more data, the strength of the correlation will allow the DPE analysis to be used during the design and sequencing phase of planning to better design the mine to minimise seismic hazards.

Jan 1, 2008

By Van Groenou B

Traditionally mining and conservation have been regarded as opposing and mutually exclusive concepts of land use. Often problems are anticipated which cannot be substantiated by facts. In addition, an ill defined time-scale adds to potentially emotive issues. Examples from Australia and elsewhere are presented which illustrate the dynamic nature of the environment and accentuate sequence patterns in plant community development following natural and man-made disturbances. The mining industry generally appears to be aware of the environmental impact of mining and whilst endeavouring to minimise the disturbance, is still orientated towards maximum production.

Jan 1, 1984

By B Lumsden, R Smiles

Independence Group’s Jaguar Mine treats a polymetallic ore producing a copper concentrate and zinc concentrate. Effective separation of the sulfides requires relatively fine grinding with flotation feed P80 of about 75µm. Zn losses to final tails are greater than 60 per cent and <32 µm. When magnetic conditioning was first installed in 2010 it showed about an 8 per cent reduction of zinc in final tail and on some ores a similar benefit for silver as well. Current testwork is showing about a 12 per cent reduction in zinc and silver in final tail, consistent with the original testwork. Sizing of the final tail during the tests showed that the reduction of zinc and silver losses were only in the <32 µm fraction, as would be expected from an aggregation process. However, the most surprising result was about a 4 per cent reduction in zinc and silver in the plant feed with a >99 per cent statistical certainty. The reduction in zinc and silver in the feed is also only in the <32 µm fraction. Therefore, because the magnetic conditioning of Zn flotation feed cannot impact plant ore feed grade the hypothesis is that the magnetic conditioning is reducing the fine mineral from downstream processes, like filtering and thickening, returning to the plant feed in the recycled process water. This hypothesis is consistent with plant observation of dirty concentrate thickener overflow and measurements of solids in the overflow, as well as the average % Zn grade in cyclone overflow that correlates with the magnetic conditioning ON and OFF days. This paper presents these plant test results.CITATION:Smiles, R and Lumsden, B, 2018. Improving fine sulfide mineral recovery in Independence Group’s Jaguar Mine zinc circuit, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 433–440 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By D J. Robinson, L L. Kuhar

In-situ recovery (ISR) is accepted and applied across many geographies, and approximately 50% of the world’s uranium is currently extracted by using an ISR method (World Nuclear Association, 2014). The low environmental impact, the elimination of risk for mine workers and the fact that all of the lowest-cost producers of uranium use an ISR approach should raise interest from traditional miners (IAEA, 2014). However, the broader application of ISR to other commodities and mineral systems remains limited. A number of demonstration (experimental) copper projects have been undertaken (Sinclair and Thompson, 2015) with a few copper projects in Arizona being close to demonstration (Florence, 2018 and Gunnison, 2018). Evidence of very few economically operating ISR copper projects can be found (for example, the Russian, Uralgidromed OAO, built by the Russian Copper Company in 2005 and operated as an ISR facility from the Gumeshevskoye deposit (Russia Mining, 2018). A number of gold deposits, particularly paleochannel deposits, have also been considered for ISR, but, to the best of our knowledge, only limited demonstration and no commercial operations have been established, yet (Kuhar et al, 2018 and references therein).CITATION:Robinson, D J and Kuhar, L L, 2018. Extending mine life through application of an in situ recovery approach, in Proceedings Life-of-Mine 2018, pp 56–57 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By G Yeowart, P D. Munro

The Prominent Hill copper-gold concentrator of OZ Minerals Limited in South Australia was built in 2008 and commenced commercial production in early 2009. It has a design ore throughput of eight million tonnes per year (Mt/yr). While the flow sheet has many items in common with other plants treating ores from iron oxide-hosted copper-gold deposits, the Prominent Hill concentrator also has some unique features. Plant design has been based on a 'template' of the very successful Ernest Henry concentrator. Initial options considered for processing Prominent Hill copper-gold ore are briefly examined as well as potential complications arising from the presence of a considerable tonnage of 'gold-only' material present in the deposit. Metallurgical test work and the subsequent decisions leading to the selection of a conventional crushing, semi-autogenous grinding (SAG) and rougher flotation circuit is discussed. One particular difference with other plants treating this ore type is that metallurgical tests and mineralogical studies identified that rougher concentrate had to be reground to a P80 of 20 - 25 microns or finer for adequate liberation of fluorine-bearing minerals. Subsequent satisfactory separation of fluorine-rich gangue material from the valuable copper sulfides requires highly efficient cleaner flotation to make a commercial quality copper-gold concentrate. Xstrata Technology's IsaMillÖ and Jameson Cell technologies developed to meet similar taxing fine grinding and flotation duties for the treatment of the refractory zinc-lead-silver ores of the Carpentaria-Mount Isa Mineral Province were selected for regrinding and cleaner flotation. Plant design has features aiding ergonomics for ease of operation and maintenance not commonly seen in recent projects with large sulfide flotation concentrators.

Jan 1, 2009

By Leggate J

In the past many coal mining projects commenced without any consideration being given to eventual site rehabilitation. Now that site rehabilitation is assuming greater importance with changing community expectations, and standards are becoming less negotiable, it cannot be ignored in either the development of mine working plans or economic models. The "unspecified" rehabilitation measures associated with many existing projects will be the subject of debate for some time to come yet. It would be wise to plan for the future. Once an agreeed standard of rehabilitation is accepted, good management involves considering practices which will facilitate eventual rehabilitation at least cost. Without planning for rehabilitation, many mines have adopted practices which are likely to result in very expensive rehabilitation measures and impact significantly on the overall profitability of the ventures. With adequate planning, procedures can be developed which achieve the same short term goals without significantly effecting cash flow but with very significant impacts on the final rehabilitation cost. This paper looks at the disposal of tailings and overburden in the coal mining process. The industry has in the past had an obvious preference for the "perceived" cheaper procedures for waste management such as wet disposal of tailings and high dumping of overburden. There are alternatives. The paper discusses the principles which should be incorporated into tailings and overburden disposal systems and identifies viable alternatives.

Jan 1, 1991

The cost of production from truck and loader fleets is influenced by management development of the culture of the organisation, work practices, systems and procedures of the production and maintenance teams. Establishing if the cost of production is the best that can be achieved then requires the measurement of results against established standards of performance. This paper provides a series of discussion points of the factors that influence the cost of production from men and machines for large scale open pit mining operation and provides some suggested performance standards in the form of Benchmarks. Most of the references have been drawn from established large scale deep pit mines in USA, Canada and Australia which have had to implement and constantly fine tune cost efficiencies in order to survive. The discussion provides:ò a review of priorities or the relative importance of the various cost elements for a mining system;ò suggestions of systems and procedures for the operation and maintenance of machines which are considered to yield the best overall results;ò examples of operations that have developed and implemented management systems and controls that are achieving good results in specific functions; andò suggested benchmarks of performance.

Jan 1, 1992

By M A. Etheridge

The evolution of economic precious metal and copper-gold deposits in high-level igneous terranes is dependent on very efficient fluid focussing. This is most readily achieved by contemporaneous deformation, igneous intrusion and hydrothermal activity. Mineralisation in these environments generally occurs in fault and fault-vein arrays developed in the cover sedimentary and volcanics sequences above older regional scale fault systems. Such reactivated fault systems are particularly prone to developing tile complex fracture arrays, extreme local dilation and dramatic increases in permeability that are necessary to efficiently focus hydrothermal fluid and produce large mineral deposits. The arc systems of tilePacific rim are typically structurally and tectonically complex. At any given period in the evolution of an arc system, it may be dominated by extensional, compressional or strike-slip deformation. Indeed, it is common for the tectonic environment to change repeatedly through the development of a single arc segment. As a result, structures formed in one tectonic environment are commonly complexly reactivated in quite different environments later in arc evolution. These complexly reactivated structures have greater potential to localise extreme fracturing, dilation and fluid flux than primary structures. Application of this knowledge to practical exploration requires an understanding of the primary geometry of the controlling fault systems, the fault movements during reactivation, intrusion and mineralisation, and the consequent location and geometry of dilational sites. Simple 2D lineament analysis and targeting on lineament intersections does not suffice. Chemical processes that results from structurally focussed fluid flow may also contribute to permeability enhancement and further enhance fluid flux. Two main types of chemical feedback are important. The first involves selective dissolution of minerals during alteration and tile consequent production of increased porosity and permeability. The second occurs where alteration changes the mechanical properties of tile rock mass, especially where it leads to a greater propensity for fracture (eg by silification). In near-surface environments (< ~1 km), geomorphic processes complement fault systems in focussing fluid flow to develop sub-horizontal bodies of mineralisation, such as the giant Ladolam gold deposit (>42 million ounces of gold).   Along with classification schemes which stress crustal level, host rocks and alteration assemblages, the styles of high level 'epithermal' and reated deposits must also be considered in respect of their controlling co-active fault structures. Such structural understanding, combined with understanding of tile chemical processes involved (eg host rock reactivity), provides a major tool for exploration particularly in terrains obscured by deep weathering. Geological interpretation based on integration of field mapping with magnetic, radiometric and other remotely sensed imagery provides a powerful complementary tool to the traditional geochemical and geophysical targeting techniques. Timely and effective geological input is capable of reducing exploration risk and providing a more cost-effective basis for drilling and development. Examples of deposits associated with fault reactivation in extensional, compressional and strike-slip settings within arc systems are discussed in this context.

Jan 1, 1995