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By P R. Botha

Mining has played a significant role in human development and without the mining sector, society would not enjoy a large number of the benefits that it does today. However, mining has also carried with it some important lessons, which remain the source of ongoing learning. One of these lessons is the poor closure or abandonment of mines, worldwide. This has in many cases resulted in large tracts of unproductive land, representing a source of environmental pollution and a safety hazard to the community. Frequently associated with this is a legacy of mining communities having fallen into economic and social decline, beyond mine closure.Due to this legacy, governments, society and the mining sector pay far greater attention to mine closure planning today, than was done in the past. Typically closure planning has focused on the engineering aspects of a mine, namely decommissioning of the workings and plant; dismantling of unusable infrastructure; and rehabilitation of disturbed land. These are important aspects of closure but a more holistic, long-term approach is required which encompasses environmental and social aspects and aims to leave a positive legacy behind.In planning for a mine closure scenario with a lasting positive legacy, it is critical that the broader receiving environments (social, economic, physical and biological) within which a mine is located, define and drive the closure plan and the mine planning as a whole. This ensures that the broader environment influences mine closure, as opposed to looking at how a closed mine will impact on the environment. The ultimate aim is to first understand the broader environment and then to fit the closure of a mine into it. The earlier this approach is followed in the life of a mine, the greater the operational time frame available, and hence a better chance is presented for planning and managing a mine towards the desired, tested and agreed post closure scenario. Within this broad context, there is tremendous scope to achieve successful mine closure. However, it is critical to note that mine closure is not the sole responsibility of the mining companies, and neither is it possible for said mining companies to achieve mining closure alone. This concerted effort requires a multi-stakeholder approach in which partnerships are created and risks, responsibilities and opportunities are shared and managed. To achieve sustainable closure, a multi-stakeholder approach based on an initial forward-looking closure vision is required. This approach provides an early basis for consideration of alternative land uses and economic options from which specific actions to achieve the preferred option can be defined. The Anglo American plc Mine Closure Toolbox has been formulated and developed around this concept. The Toolbox aims to expand mine closure planning - from financial provisioning for rehabilitation and physical closure, to planning for sustainability beyond mine closure and leaving behind a positive legacy.This paper focuses on the business case for mine closure planning and provides an overview of the Anglo American plc (AAplc) Mine Closure Toolbox.CITATION:Botha, P R, 2012. The business case for mine closure planning and an overview of Anglo AmericanÆs mine closure toolbox approach, in Proceedings Life-of-Mine 2012 , pp 7-10 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By S Porter

The Melbourne City Link Project is a privately funded road infrastructure project linking three significant existing freeways in the vicinity of the Central Business District. The State Government, through the Melbourne City Link Authority, has contracted Transurban to build, own and operate City Link for a concession period of 34 years before the road network is transferred to the State. Transurban has a contract with Transfield Obayashi Joint Venture (TOJV) to design and construct the works. The project is divided into the southern and western sections and the tunnel works comprised the significant component of the Southern Link. Outside of the cut and cover tunnels at the portals, the driven tunnels component was constructed by TOJV direct labour. TOJV subcontracted all design work to a joint venture of Hyder Consulting and CMPS&F (Hyder/CMP). The geology in the tunnel corridor and generally below the city of Melbourne is highly variable and constantly changing. The tunnels were driven, for the most part, in siltstone and sandstone of the Silurian age, but also intersected overlying basalts and clays. The Silurian bedrock is a fractured aquifer that is connected to overlying alluvial aquifers. Consequently, the construction of the tunnels was a complex engineering task. This paper details the operational relationships and procedures developed to deliver a design that was aligned to the construction constraints and delivered an end product that met all technical, quality, cost and program goals.

Jan 1, 1999

All companies and individuals who embark on a business venture incur costs. For the most part these costs can be conveniently categorised, firstly into capital and operating costs and then into the various elements of these major cost centres. Although the nature of expenditure naturally differs as between industries certain broad cost types are characteristic of all heavy industries. The capital costs of gaining access to an orebody, equipping a new mine, building a treatment plant and perhaps refining and smelting facilities are likened to capital expenditure by a manufacturer on new plant and equipment required for an expansion or new product innovation. Similarly the day to day costs of labour and materials employed in the running of a mining operation can be likened to similar costs in other heavy industry. There is another group of costs that are not so easily categorised. Most industries incur unavoidable costs that do not form part of the direct or capital costs of physical production. These costs include taxes and other payments to government and research expenditure. The mining industry has a particularly heavy burden of non-production costs and it is the objective here to highlight and analyse a few of them. These costs are exploration expenditure, infrastructure expenditure, royalties and income tax. This is not to suggest that these are the only major non-production costs that the mining industry needs to bear. The industry may incur significant costs for environment protection, land tenure maintenance and on liaising with Government on a wide variety of matters. It is for reasons of subject manageability that the list is confined to the four costs mentioned. For the mining industry, exploration and infrastructure expenditure, royalties and income tax have several distinguishing features. Firstly, they are generally proportionately large costs. Exploration and infrastructure expenditure for example, could well exceed mine development costs. Depending on how royalties are levied, they may be very high in relation to profits earned and many in fact exceed profits. Secondly, except for income tax, they are costs that are generally not payable by other industries. Exploration expenditure is in some respects comparable with industrial research and development. However, because mines are wasting assets exploration is necessary for survival, and it is likely to form a larger part of costs per dollar of profits or sales than R&D. It can therefore be said that exploration is of far more significance to the miner than R&D is to the typical industrial company. Furthermore, unlike exploration expenditure, R&D results are transportable and patents permitting, transferable. The infrastructure burden that miners must carry is unique to the industry. Whereas urbanised industry is not usually liable for the capital cost of power, water, transport, townships and community facilities, the miner must finance these projects himself. Neither the payment of royalties, nor of course, income tax are unique to the mining industry. Royalties are more properly described as a unique charge on some primary industries but however described, they are a charge that manufacturing and service industries do not have to pay. Whilst we all pay income tax, the mining industry's uniqueness derives from the special problem that the industry has in arriving at annual net income in view of the capital intensity of the industry, partly due to expenditure on infrastructure, the indefinite life of capital equipment and its unpredictable residual value, funds expended on exploration and long lead times associated with a mine development. The third distinguishing feature of these costs is that, with the possible exception of exploration expenditure, they are heavily influenced by the policies and actions of Government. As such the industry has a responsibility to promote the industry by emphasising its potential to improve national product including exports and by requesting that the Government provide for the industry in its long term planning and seek its co-operation to prevent the industry incurring inequitable penalties relative to other industries.Finally, exploration and infrastructure expenditure are significant because they are front-end charges on a project. When due allowance is given the time value of money and the deferment of income from a mining development to which they relate, exploration and infrastructure expenditure assume greater importance than the raw money expenditure suggests. For all these reasons, exploration and infrastructure expenditure, mining royalties and mining income tax are worthy of detailed study. This is the purpose of this paper. The objective is to examine the determinants that give rise to them and provide some thoughts on their impact on on-going and potential mining developments and, where relevant, to make some suggestions as to how they may be minimised.

Jan 1, 1977

By Flann R. C

A small modification to current industrial practice should lead to better nickel powders for use in alloying, electroplating, and powder metallurgy. Nickel powder compacts sold for alloying are not always suitable for electroplating applications, since some presently used commercial powders will expand on sintering. Further, such nickel powders are unsuitable for use in the production of powder metal parts, because of expansion during heating of the near-net-shape preforms. Research in these laboratories has enabled the elimination of expansion, and led to techniques for the production of compacts suitable, in particular, for commercial use in both alloying and electroplating. The techniques include: powder pretreatment, cold pressing and sintering, hot pressing, and hot pressing and sintering. In this way compacts are readily prepared with densities of at least 93 per cent of solid nickel, and these, when used as anodes in Watts general purpose and bright baths, give both cathode current and plating efficiencies of 90-98 per cent.

Jan 1, 1979

By G Stephenson, G MacDonald, A Yeomans, S Sinclair, V Knott

Rio Tinto has actively committed to progressive reclamation, concurrent with commercial operations, at its Diavik Diamond Mine. The most significant piece of progressive reclamation undertaken at Diavik to date has been the construction of an engineered thermal rock cover for the mine’s largest waste rock storage area. This 80-metre-tall and 2000-metre-long area is known as the Waste Rock Storage Area – North Country Rock Pile (WRSA-NCRP) and contains the operationally segregated potentially acid-generating waste rock mined over the last 20 years. As part of the mine plan, an opportunity was recognised where a limited 1.5 per cent of the WRSANCRP surface area was required for storage of the balance of life-of-mine generated waste rock and a decision was made to advance the closure design almost a decade ahead of final closure. With over 12 860 000 tonnes of material placed and 57 443 dozer hours logged since cover construction, progressive reclamation on the WRSA-NCRP is scheduled to be complete in mid-2023, three years before planned cessation of commercial operations in 2026. The progressive closure of the WRSA-NCRP demonstrates Rio Tinto’s commitment to not only closure, but modern best practices with integrated mine closure. Over the past seven years, Diavik has overcome multiple implementation hurdles for this project including the psychology of operational standby, the financial mechanisms required to support closure, working within the constraints of a mine plan and the associated operational organisational structures. This paper outlines the lessons learned to provide an example of successful integrated mine planning for closure. The North Country Rock Pile project had three major learnings which resulted in an effective organisational structure that allowed for the execution of an integrated planning model for progressive closure. The initial hurdle the project faced was adapting the psychology of an operational open pit mining team. The team was an experienced mining group who came in with the perspective to target the shortest haul possible resulting in the initial perception that the longer haul of material to the NCRP was an un-necessary task impacting operational performance metrics. After the installation of an improved dispatch tracking system and performance metrics, it was possible to demonstrate that the mine was shovel constrained. This showcased the short haul was generating an increase in queue time not production. With updated performance metrics, the team was aligned to target a decrease standby through haulage to the NCRP. These performance metrics had to be reinforced by financial mechanisms. The operations team was able to offset costs by charging time to the capital project set-up for the closure of the NCRP. This allowed the operations team to receive credit for time that would have otherwise likely been standby. As well, the progressive closure project was able to receive the benefit of not having to incur costs for the drill, blast and load as that was done as part of the operation. This was a significant benefit to the project and one of the primary drivers for the early approvals of the work as the project costs were limited to the incremental haulage distance and placement of the material. Life of Mine Conference 2023 | Brisbane, Australia | 2–4 August 2023 114 While the combined operational and progressive closure approach provided financial advantages, it did result in the project being constrained by the operational activities. A traditional capital project is managed through a linear execution plan where the deliverables within a project are within the realm of control of the project execution team. However, the NCRP project had to be continuously adapted to the outcomes of the pit operations. This included geotechnical constraints, ore delivery, and other operational delays. To adapt, the planning module had to be dynamic but not reactive to allow for adjustments on a shift-by-shift basis. Based on this requirement the Diavik Closure Projects structure adopted a mine planning format. The team executed a similar planning timeline and reporting structure as the mine operations team, allowing planning to be integrated into the operational planning structures on a daily, weekly, monthly and quarterly basis. This resulted in the Projects team as a core pillar of the mine planning team. The process of continuous improvement spanned six years and has resulted in the project being ahead of schedule and under budget for the project’s scheduled progressive closure completion date of June 2023. The North Country Rock Pile project supports the argument that bulk earthworks progressive closure projects should be integrated into the operational mine plan. If the project is aligned the mine plan it allows for dynamic adjustments which capitalise on evolving opportunities inevitable in an operating mine. These cultural and organisational alignments should be supported by appropriate performance metrics and financial mechanisms to ensure united priorities. The result of this alignment provides long-term financial savings for the business as well as delivery of closure objectives.

Aug 2, 2023

It is always difficult to sum up an open forum adequately and instantaneously, so, with the privilege of hindsight, and also with some time to reflect, I am exercising the Chairman's prerogative to put together my view of the overall conclusions. Hopefully, these may provide a focus for each Institute to formulate its own programme with respect to mineral industry education. First, in answer to the question, "Should there be Schools of Mines?", there was a very clear 'yes'. However, I reiterate what I said in the introduction to this forum, specific professional education for the mineral industry exists only because the mineral industry sees a need and wants it. If the mineral industry should decide that it does not need professionals with specific mineral industry training, then such training will cease to exist. As alluded by Dr Hackett, if such training ceases to exist, one must then question the need for Institutes of Mining and Metallurgy. Now, there's some food for thought! Specialist schools of mines (metallurgy and geology) can only exist in an environment of genuine interaction with, and support by, industry. For their part, schools of mines, used here in a generic sense, require leadership that is strong but responsive to industry needs. It is the leader that puts his stamp on a school, and, to a large extent, determines whether that school is 'good' or only 'mediocre'.

Jan 1, 1986

The originally estimated mine life at Kidston (starting 1984) was 12 years. Through a continuing process of re-evaluation and improvement in the operation and by expanding the geological knowledge in the region, the mine life has been considerably extended. With falling grades and harder ore, the additional reserves have come with increasing risk - not only in an economic sense associated with diminishing profit margins but also operationally, requiring innovative milling technology and geotechnical designs to provide a lower cost environment for continued profitable mine production.

Jan 1, 1994

By Corbett GJ

The Bulolo Graben represents an intra-arc rift formed by activa- tion of transfer structures in an extensional setting formed be- tween the eastern and western sectors of the New Guinea Origin. Crustal thinning has facilitated the emplacement of dacitic Edie porphyry intrusions, locally as flow dome complexes, phreatomagmatic (diatreme) breccias and the Bulolo ignimbrite/ agglomerate as an extrusive equivalent of the Edie Porphyry. Gold mineralization is localized along intra-graben structures, com- monly at the intersection with cross structures and occurs in sub- sidiary dilational fractures and not the localizing major structures. Gradations are apparent in the styles of mineralization according to the degree of erosion of the hydrothermal system. Hamata occurs as the deepest mineralization of the quartz-sul- phide style Wau, Hidden Valley, and Edie Creek are dominated by carbonate-base metal styles. Kerimenge grades from quartz sulphide through carbonate-base metal to epithermal mineraliza- tion, the latter style also being present in the periphery of Edie Creek. Here, pre-existing fractures of the Edie Creek Structural Corridor have been reactivated by movement on NS structures to form the ore-hosting dilatant lodes. Fluid flow may have been from the vicinity of the Nauti diatreme margin and along the vein System.

Jan 1, 1997

By J Tibbett, A Colebourn, B Hebblewhite, F Suorineni

The concept of Big Data refers to data sets that are so large, variable and/or complex that traditional data processing applications struggle to integrate the data for effective investigation, analysis and value generation. With advances in sensor technology and smarter equipment, the mining industry is experiencing Big Data, and in a different way to how the intelligence and marketing communities experience Big Data. Future mining will bring larger, more complicated and diverse data sets increasing the strain on traditional data integration and investigation techniques. Block caving is an important mining method for the extraction of massive, low-grade ore deposits due to its low operating cost and high production potential, given the right orebody geometry and ground conditions. This paper focuses on block caving due to its increasing popularity and importance in the future economic extraction of multiple commodities. The block cave mining system (BCMS) is a complex interrelation of factors, and due to the reliance on natural processes within the system, it is one of the least understood mining methods. Obtaining information on the factors within the BCMS generates large, complex data sets on various time scales. Each sensor network within the BCMS combines spatial and temporal information with tens to hundreds of recorded parameters. Data sets are quickly moving from multidimensional to n-dimensional. Optimisation of the BCMS is only possible through a holistic analysis approach, thus involving the integration of multiple, diverse, n-dimensional data sets (Big Data). This paper presents a current example BCMS Big Data situation involving 12 sources of information with differences in volume, data format and frequency of data generation. This suitability of virtual reality scientific visualisation (VRSV) as a solution to BCMS Big Data interpretation difficulties is then discussed. These 12 data sets can be effectively integrated using VRSV for intuitive and accelerated investigation of the BCMS. Potential future Big Data within the BCMS is presented involving 20 sources of information resulting from our increased need for monitoring and advancements in technology. Current methods of defining queries may not be suitable within these future complex, multidimensional data sets, and the potential of artificial intelligence algorithms within this system is discussed. These advancements in technology and machine learning lead to the requirement of live data acquisition and analysis. VRSV is identified as a suitable technology to satisfy the needs of real-time insight into the performance of these future caves for optimised management and reduced risk.CITATION:Tibbett, J, Suorineni, F, Hebblewhite, B and Colebourn, A, 2015. Virtual reality scientific visualisation – a solution for big data analysis of the block cave mining system, in Proceedings Third International Future Mining Conference, pp 109–116 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By Hammond J. R, Ward T. A

The Tom Price orebody, in the Hamersley Ranges of North West of Western Australia, is mined by Hamersley Iron Pty. Limited. The orebody is a folded sequence of hematite and shale bands capped with goethite, with a con- sequential variable iron content. The overall grade is below that required to yield spec- ification product, necessitating selective mining, 'Zone Plans' based on geological structure have been developed to yield forward information on material types and grades. Short and medium term mine plans - the initial stage of quality control - are based upon these 'zone plans'. Blasts are laid out to break to the grade boundaries, thus minimising dilution, and the samples taken from the blasthole cuttings provide blast grades. Blending of shovel out- put from different blasts forms the operational basis of grade control. Shales, being more friable than hematite, produce fines that are lower in iron grade than lump. Quality control in the mine centres around maintaining the target fines grade, compensation being applied in the mine if the fines grade lies outside the target range.

Jan 1, 1973

By P Trotta

The paper provides a structured methodology to investigate metallurgical problems within the operating concentrators. The strategy uses classical metallurgical data analysis as well as pulp, solution and surface analysis to determine the reasons for particular behaviours. The approach applies equally to all mineral-processing operations. To demonstrate its effectiveness a case study, based on work conducted at Pasminco Rosebery Mine, is described. In this work, the classical metallurgical analysis indicated that a significant amount of sphalerite reporting to the lead concentrate occurred as liberated particles. A combination of pulp, solution and surface analysis supported the hypothesis that the liberated sphalerite was recovered by inadvertent activation by lead ions. Laboratory studies have indicated that the use of sodium carbonate, by itself and in combination with zinc sulphate and sodium cyanide, when added to the lead regrinding mill can depress sphalerite flotation, resulting in an improvement in the lead grade/recovery curve. When this approach was tested in the plant other more dominant issues masked any positive effect the addition of sodium carbonate may have had. The plant trial highlighted the real need for additional regrinding capacity.

Jan 1, 2002

An extensive study was carried out to evaluate the performance of Outokumpu OK50, OK38 and Maxwell MX14 cells at ComincoÆs Red Dog flotation concentrator in Alaska. Tests were conducted by varying operating conditions of the cells installed in different circuits in the plant. The hydrodynamic and gas dispersion properties were measured and the metallurgical performance of the cells was evaluated for each condition used in the tests. This paper highlights the importance of superficial gas velocity, bubble surface area flux, gas hold-up, power consumption, residence time distribution and froth flow behaviour in optimising cell performance. The findings of these tests provide valuable insights into selection of the best cell operating conditions to optimise circuit performance.

Jan 1, 2000

By Morrison RD, Peberdy NJ

Simulator training provides a cost effective method of training operators in both the process and control aspects of a metallurgical plant. The components and requirements of a training simulator are described along with the benefits to be gained from simulator training. A table summarizing some applications of metallurgical training simulators is Given.

Jan 1, 1991

Gold was discovered at Waihi in 1878. In 1987 the modern Martha Mine opened in the middle of the town of Waihi. Newmont Waihi Gold as the current licence holder has been operating the mine since 2000. The current open pit was scheduled to stop production in mid 2006. An underground mine is currently being developed to the east of the town.   In 2001 serious subsidence issues from historical underground mine workings outside the mining licence and the forecast closure of the open pit acted as a catalyst for the development of new communication initiatives.   In this context Newmont Waihi Gold and the Hauraki District Council initiated a community consultation process with the people of Waihi. The Waihi Community Consultation Committee (WCCC) was established in May 2003. After an initial brief to act as a forum for community participation in closure and rehabilitation of the Martha Mine, the group quickly took on a much more proactive role working towards the long-term social, environmental, cultural, economic and spiritual sustainability of Waihi.   In the course of over three years of meetings all groups represented on the committee have presented their views, developed ideas and established an organisational structure to bring those ideas to fruition. The challenge now is to work together to consolidate likely options, seek sources of funding, produce business proposals and implement the plan for the future of Waihi.   This paper backgrounds the experience to date and describes the outcomes of the process. For more detail on process considerations this paper should be read in conjunction with Part C by process facilitators, T Clark and S Stewart. For more detail on progress towards the groupÆs goals and future possibilities, this paper should be read in conjunction with Part B by Vision Waihi Trust CEO, E Morrow.

Jan 1, 2006

The paper briefly discusses the benefits to proponents of a formal environmental assessment process. It is argued that any process should be fair, cost effective and efficient, involve all affected parties, and should identify important issues at an early stage. The paper outlines the procedure used in Victoria, and the ways in which it attempts to address the above criteria.In conclusion the paper discusses progress towards a national approach to Environmental Impact Assessment. This is currently being pursued by the Australian and New Zealand Environment and Conservation Council.

Jan 1, 1992

By Osorio J. D C, McMahon M. D

Burwood Beach Sewage Ocean Outfall is being constructed by the Hunter District Water Board as part of an amplification scheme to eliminate pollution from adjacent bathing beaches. The outfall consists of a 93m vertical shaft, 1950m of 2.7m diameter tunnel with a series of diffuser outlets connecting the seaward end of the tunnel to the sea floor on a rock outcrop. The site of the work is in the Newcastle Coal Measures and the project is complicated by the proximity of colliery workings to tunnel alignment, although the colliery records provided valuable information on geological features. The location of the tunnel was determined to be in the Waratah Sandstone Formation immediately below the colliery workings after three different alternatives were considered. The shaft, which will be sized to suit contractor's construction methods and equipment, will be sunk through about 24.5m of alluvial material and 68.5m of rock. The tender documents were developed to allow the contractor considerable flexibility in construction method to suit available equipment. The specification also allowed great flexibility in tunnel construction method with minimum cross sectional area of 5.7m2 being the basis for a number of allowable alternative profiles ranging from circular to horseshoe.

Jan 1, 1987

By F Clark, B Catto

The Mako domain comprises the Mako lodes at Sunrise Dam Gold Mine, Western Australia. This domain was initially bulk or æbucketÆ domained for the open pit resource in 2000, due to complexity in defining the lodes as a result of low drill density. Negative ore tonnage and positive grade and ounce reconciliations were experienced during mining of the domain in the mega-pit, though only small volumes of the domain were mined. Significant amounts of exploration and underground grade control drilling has been completed since the initial bulk domain interpretation and greater geological understanding of the mineralisation controls and geology of the lodes now exists. Mako provides approximately 50 per cent of the ore tonnes and ounces for the North Wall Cut-back, the latest open pit phase of mining at Sunrise Dam. The importance of Mako to mill supply and life-of-mine planning, as well as past reconciliation performance necessitated a reinterpretation of the domain to increase confidence for mining. Historic exploration drilling, underground grade control drilling and detailed pit-wall mapping were used to build mineralised subdomains within the confines of the original domain. These reflect more closely the spatial extents and geological controls on the mineralisation. A new resource model using the multiple indicator kriging (MIK) technique was generated using the new domains. It resulted in a decrease in tonnes and ounces but increase in grade for the sum total of the new domains compared to the old æbucketÆ domain. This is attributed to the increased selectivity and structural constraints imposed by the new domains. A retrospective comparison of the Mako grade control from the mega-pit versus the new resource model was conducted, which æreconciledÆ 103 per cent tonnes, 106 per cent grade and 110 per cent ounces. This has provided confidence that the new model is a better estimate of the lodes. Qualitatively, the new model is a better representation of the geology and extent of the mineralised structures with significant areas of change identifiable. Grade-tonnage plots comparing the 2006 and 2008 models show that most tonnes have been shed from the low-grade û subeconomic grade cut-offs. This is mostly attributable to the volume reduction of æoreÆ in the 2008 model compared to the 2006 model, where the true mineralised zones are captured by the new domains. The reinterpretation and remodelling of Mako is an example of an evolved domain model and shows that mineralised zones need to be differentiated adhering to the geology and geological controls on mineralisation, which are understood largely due to increased drilling density coupled with mapping.

Jan 1, 2009

The Que River and Hellyer polymetallic massive sulphide ore bodies are located 3 kilometres apart in the Cambrian Mount Read volcanics of Western Tasmania. Both deposits are classic examples of the Kuroko volcanogenic style. Base and precious metal rich hydrothermal solutions rose through a deep fracture system and vented on the sea floor, causing sulphides to accumu- late in adjacent topographic lows. Together the preproduction geological resource is approximately 23 million tonnes at greater than 18% zinc plus lead, with economically significant silver and gold. Exploration by Aberfoyle in the Mount Read volcanics com- menced in 1970. Que River was discovered in 1973 following a comprehensive data review, a regional stream geochemical survey and a helicopter-borne electromagnetic survey. Production began in 1981, and the mine is currently producing 300,000 tonnes per year. The ore is sold to the Electrolytic Zinc Company of Aus- tralasia Ltd mill at Rosebery. Ten years of extensive geological mapping, soil geochemistry, and induced polarisation, combined with continual study of the Que River orebody and its host rocks, formed a strong frame- work for the discovery of the Hellyer deposit, which was found as a result of drilling .a subtle time domain electromagnetic anomaly in 1983. Hellyer is currently being mined at a rate of 250,000 tonnes per year, with the ore being concentrated at Aber- foyle's converted Cleveland tin mill. Treatment of 1 million tonnes per year will begin in early 1989 at a new mill located near the Hellyer site.

Jan 1, 1988

By Cairncross A. A

Papers on technical aspects of the Melbourne Underground Rail Loop project are being presented at this conference or have been presented previously or will be presented at other forums. This paper provides the framework for these papers by presenting the overall engineering tasks. The conceptual design, the special investigations undertaken, the management of the project and the construction development are highlighted.

Jan 1, 1981

By R J. Goldfarb, A B. Christie, D I. Groves

Small orogenic gold deposits have the same deposit-scale geological and geochemical features as those that characterise giant orogenic gold systems (>16 Moz Au). Therefore, a broader-scale approach is needed to identify the critical controls on giant deposits and their disproportionate distribution throughout time and space. Ages of giant gold systems cluster around well-defined periods of lithospheric growth at continental margins, and it is orogen-scale processes during these Late Archaean, Early Proterozoic and Phanerozoic times that determine gold endowment of a province.   A critical factor for giant orogenic gold provinces appears to be asthenospheric upwelling at the time of gold mineralisation to most effectively transfer the thermal energy required to initiate and sustain high hydrothermal fluid flux. The extent of this fluid flux should be related to thickness of the lithosphere beneath a province at the time of gold mineralisation, such that giant gold deposits are much more likely to develop in orogens with oceanic or thinned continental lithosphere. A proxy for the latter is likely to be a short premineralisation crustal history such that thick subcontinental lithospheric mantle was not developed. Conversely, orogens with protracted premineralisation crustal histories are more likely to have a thick subcontinental lithospheric mantle, which is difficult to delaminate and, hence, such provinces will normally be poorly endowed. The nature of the lithosphere also influences the intrinsic gold concentrations of potential source rocks, with back-arc basalts, transitional basalts and basanites enriched in gold relative to other rock sequences. Thus, segments of orogens with thin lithosphere may be defined by conjunction of giant-scale fluid flux through gold-enriched sequences.   Although the nature of the lithosphere plays the crucial role in dictating which orogenic gold provinces will contain one or more giant deposits, the precise siting of those giants depends on the critical conjunction of a number of province-scale factors that control fluid conduits, traps, and seals in tectonically and lithospherically suitable terranes within accretionary orogens.

Jan 1, 2005