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By R G. Moreby, S Bluhm, FávonáGlehn, C Pascoe

Resolution Copper Mine in Arizona, USA, is planned to be a 2000 m deep panel cave mine with virgin rock temperatures exceeding 80¦C in rock with high crystalline silica content, resulting in a very challenging ventilation and cooling system design. This is one of the largest copper orebodies ever found and, with a planned rock production rate of 120 kton/day. The project is currently in its prefeasibility phase and the paper discusses features of the ventilation and cooling system design which includes multiple ventilation shafts with total primary ventilation flow of about 3000 m3/s and both surface and underground refrigeration plants producing more than 140 MW refrigeration capacity. The cooling system features large surface bulk air coolers chilling all downcast air supplemented by an underground secondary air cooler system and a chilled service water system. This will be a very challenging mine to ventilate and cool but this work has demonstrated that it will be technically achievable with the application of existing technology.CITATION:Bluhm, S, Moreby, R G, von Glehn, F and Pascoe, C, 2013. Life-of-mine ventilation and refrigeration planning for Resolution Copper Mine, in Proceedings The Australian Mine Ventilation Conference , pp 125-138 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

Digital Simulation of Particulate Processes The inherent complexity of mineral particulates (shape, size and mineralogical texture) has challenged conventional simulation model approaches for decades. Much effort was expedited in using mathematical assumptions to accommodate stereological effect. With the advance of instrumental methods such as x-ray microtomography 3D structure can, in many cases, be measured directly. The information derived from such measurements provides direct input to building the structural digital model. In addition digital simulation methods that enable creation of process realistic particulate properties in an efficient digital computer space have demonstrated their effectiveness to model a variety of realistic packing, sorting and multi-phase processes. The paper reviews recent advances in the use of information derived from 3D micro-tomographic imaging and laser scanning technology can be coupled with digital methods to enable simulation of tablet compaction and dissolution, filtration and permeability, column packing and leaching kinetics, packing and cementation of nuclear waste. By assigning 'properties' to a digital zone (voxel) in the computational space it is possible to mimic the realistic characteristics of quite complex particulate mineral processing systems. The system self-adapts to correct the coherent particle characteristics (shape, size, compound, porosity) with time. Such simulations are useful to elucidate the sensitivity of system performance to variations in process parameters. Dimensional scaling of the approach is also possible, as the case studies will illustrate, in deploying the method to both small (micron) and large (m) features. The use of process realistic simulations presents experimental challenges in code validation. It is in this context that other tomographic methods play a role in direct 3D measurement of system behaviour such as electrical and optical sensors.

Sep 13, 2010

Rutile Beach Sand from Hard Rock

Sep 13, 2010

By D Kepert

It is the role of the exploration geologist to create wealth through the discovery, delineation and characterisation of economic mineralisation. This requires a critical depth of geological understanding.Unfortunately, the resource industry is well known for its cyclic nature. Many of the current generation of workers have only ever experienced the boom of the ‘super-cycle’ and are only just discovering the negative side to the business. For the case of the geologist and especially the exploration geologist, the magnitude of peaks and troughs are usually amplified and may become destructive to all parties. During the uptime a healthy stream of exploration good news becomes the staple diet of company releases, in particular those of junior companies attempting to bolster the share price. The geological knowledge and experience gained thus forms a significant and integral part of the value and therefore, future of a company. On the downturn it is often viewed that geologists are a luxury, an optional extra and a burden on the bottom line with companies entering a period of memory loss and myopia.Retention of geological knowledge however remains critical as projects, companies and cycles mature. Beyond exploration per se, this knowledge becomes both fundamental in de-risking and commercialising an asset (through development or divestment) and in positioning the company for cyclic or counter-cyclic opportunities.The growth and retention of this knowledge base is difficult to quantify in terms of direct value but becomes one of a successful resource companies greatest assets. At worst, its loss can lead to millions of investors’ funds wasted on missed opportunities, drilling, or poorly designed plant and mine.But the rocks are around for the longer haul and pay little notice to the vagaries of the scurrying of Man.This paper reflects on some of the authors own observations through 25 years of iron ore exploration, in why it is critical to always rigorously question the prevailing geological (mis)understanding and the technical and commercial benefits which that may bring, and looks forward to the future.CITATION:Kepert, D, 2015. Geology – the affirmative case, in Proceedings Iron Ore 2015, pp 285–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By A Weeks, W J. Shaw, A Kuk

Grade control is a process that requires the interaction between many components of the mining operation and successful grade control is only realised through good data, robust systems, and a well-trained, motivated and disciplined workforce.The Mt Magnet Gold Project Pty Ltd (MMGP), a wholly owned subsidiary of Ramelius Resources Limited, started mining at Mt Magnet in February 2012 with high expectations for success. Positive cash flow would fund an aggressive exploration and mine development program in the area to increase mine life. Disappointment followed when after start-up the operation had issues achieving budget grade and realising the predicted grade of the mined ore. In January 2013, things started to improve. During the next six months, gold production steadily increased with successive months achieving record production. What had changed?Improvements started following the realisation that controlling grade was not the sole responsibility of the mining geologist and that everyone on-site has a role to play. This paper examines the factors that delivered success for MMGP.CITATION:Weeks, A, Shaw, W J and Kuk, A, 2014. Who is responsible for grade? – an evaluation of the value chain at Mt Magnet Gold Project, Western Australia, in Proceedings Ninth International Mining Geology Conference 2014 , pp 477–482 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By T Schrimpf, I Bryan

The life cycle of a mining project begins with initial regional exploration and ends with mine closure and rehabilitation. Between resource definition and the commencement of mine construction is the study phase. In this phase technical concepts and processes are defined, evaluated and assessed with the aim of establishing whether the deposit is economically feasible. The study phase usually involves various steps from a concept/scoping study to prefeasibility and ultimately definitive feasibility study. The complete study phase can take several years. Although the costs for studies are low in comparison to actual construction and operating costs of a mining project, they are significant especially for junior exploration and mining companies advancing projects to the point of being funded.The studies aim to determine selected parameters for the project, eg mining and processing methods, operating strategy, etc and provide a roadmap for project development ahead. Although mining studies are of the utmost importance for the mining project and the project owner, they are usually carried out using a conventional engineering approach: the consultant or design engineer works to a defined scope of work. The resulting design might be based on good engineering, but might often also fail to provide the solution for the project owner that delivers the best shareholder value. An alternative to this more traditional approach to project evaluation is what we have termed a value engineering approach. Value engineering is a creative, organised effort, which in the case of a mining study analyses the requirements of the study for the purpose of achieving the essential outcomes with the highest shareholder value. The outcome of a study is a concept that delivers the highest achievable value of the resource project and shows the way ahead to realise this value. Through a group investigation by experienced, multi-disciplinary teams the value of the resource is improved through the study of alternative options, methods and processes. The scope of the study is not limited to a narrowly defined engineering scope, but to the creation of value.The study commences with the identification of key value drivers and risks, based on the available information (drill data, geotechnical data, metallurgical test work, etc). This enables the quantification of key uncertainties, risks and value adding opportunities. Study efforts concentrate on key value drivers and are not unnecessarily spent on side issues. This approach can significantly reduce the time frame and costs for the study phase.This paper describes in more detail RMDSTEMÆs value engineering approach to mining studies and illustrates it with examples and case studies.CITATION:Schrimpf, T and Bryan, I, 2012. The application of value engineering principles to mining studies, in Proceedings Project Evaluation 2012 , pp 163-170 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012

The timber township of Powelltown, Victoria lies N.E. of Yarra Junction, 60 miles east of Melbourne and in the site of the mill of the Victorian Hardwood Company Proprietary Ltd.A lift gauge railway owned by the company connects Yarra Junction on the Warburton line, with the township through two or three smaller mill centres on the way.The company has been operating for some 12 years. In the divide, about four miles from Powelltown, between the Little Yarra and Latrobe rivers, cutting was continued with material being handled by winch and double incline haulage over the divide. A small bush locomotive dealt with the traffic between the divide and the cutting site.In order to reduce costs, which were heavy at the haulage, the company decided to make a continuous railway from Powelltown to the bush by means of a tunnel through the divide.Hand bore holes were put down on the proposed line of tunnel and showed that the divide at this point consisted of decomposed depth of about 100 ft. towards the eastern or Latrobe side - and that the undecomposed granite summit lay to the west of the surface summit.The bores also served to locate the underground water line, this was afterwards found to rise and fall with wet and weather.To avoid tunnelling in hard and heavy water, the grading of the was laid out with the summit of the hard granite the point in the line.

Jan 1, 1925

A broker relies heavily on mineral valuations and independent experts' reports to provide the fundamental information, both technical and commercial, which provides the basis of estimating the sharemarket value of securities and underlying assets. It is important to appreciate the significant variance that can occur between the market value and other types of valuation at a particular point in time. In general, most experts' reports and valuations seek to provide estimates of technical/fundamental or ""fair"" value which correspond to the Corporations Law and accounting standards requirements. They do not usually attempt to estimate (stock) market values and it is usually and quite correctly the broker's task to estimate market values on the basis of a technical appraisal and consideration of all other commercial, market and financial influences. Therefore ideally, an independent experts' report or information memorandum will include material relating to commercial and management aspects of a company as well as detailed technical reviews and fundamental valuations. Wherever sensible cash flow projections can be made, cash flow-derived valuations, usually based on discounted cash flow (DCF) calculations, remain the preferred valuation methodology. Brokers in general would not argue with this preference. However, there is a paucity of examples of valuations where alternative methods are applied as a check on the reasonableness of a DCF-based estimate.

Jan 1, 1994

The Mineralogy and Reactivity of Pyrrhotite from Selected Nickel Ore Deposits and its Effect on Flotation Performance

Sep 13, 2010

By Gupta R. C

Direct reduction of iron ore by solid reducing agents have been studied extensively and summarised by several authors (Otsuka and Kunii, 1969; Abraham and Ghosh, 1979; Frauhan, 1977; Rao, 1971; Kawasaki, Sanscainte and Walsh, 1962; Ghosh, 1970; Rao, 1979). While studying the reduction behaviour, it is generally agreed that the reduction occurs via gaseous intermediate, generated by carbon gasification reaction which involves mass transfer, heat transfer nucleation and growth, etc through a) reduction reaction occurring at solid reductant, and b) reduction reaction occurring at solid iron oxides, thus making the overall reduction process very complex in terms of clearly defining the reduction kinetics of the system. In addition to this, practical difficulties like correctness of reaction temperature, (Seaton, Foster and Velasco, 1983) difficulties in isothermal temperature studies of reduction, difficulties in monitoring the reduction process while using gaseous reductants and separation of reduction by volatile matter from overall reduction process make the reduction kinetics more complex (Misra).

Jan 1, 1999

By P Jones

Fosterville Gold Mine is an underground operation located approximately 20 km northeast of Bendigo and 170 km north of Melbourne. Fosterville is the most productive gold mine in Victoria, producing over 100 000 ounces of gold annually. Access to the underground is via two portals cut into previously mined open pits. Fosterville is 100 per cent owned and operated by Northgate Minerals, a gold and copper producer with mining operations, development projects and exploration properties in Canada and Australia. (Northgate Minerals Corporation, 2010).Underground operations commenced in 2006 with ore production focused on three orebodies – Phoenix, Ellesmere and Falcon. Primary ventilation to the existing operation is provided by wall mounted exhaust fans located underground. This system provides approximately 220 m3/s of primary ventilation to the operations with intake achieved through the portals. Exploration drilling during recent times has uncovered another lode, the Harrier orebody, located 2.2 km to the south of the existing workings. Due to the location of the new Harrier orebody, vent analysis revealed the requirement for a separate source of primary ventilation to service Harrier. Figure 1 shows a current underground long section and the location of Harrier in relation to the existing workings. A number of options were considered, including a parallel decline from one of the existing two portals, however, a 4 m diameter, 350 m deep surface ventilation shaft was selected as the most suitable and feasible option for the mine.In December 2009, geotechnical drilling commenced to determine the most suitable location for the shaft. Site locations were constrained by a number of factors including interaction with current and planned surface infrastructure as well as proximity to nearby community members at the southern end of the mining lease. Results from the geotechnical drilling indicated that the majority of the proposed shaft would be suitable for a 4 m raise bored shaft. However, the top 40 m of the proposed shaft were deemed unsuitable for raiseboring due to zones of weakness that would likely influence the stability of a 4 m diameter shaft (Robinson, 2010). Following independent geotechnical advice and input from experienced raiseboring contractors, it was decided to construct a 40 m presink prior to raiseboring activities.A crane mounted auger was chosen as the preferred method to construct the presink. This method differs substantially from traditional blind sinking methods which are highly labour intensive. The auger, or drill, is designed and built to be attached to a crane base using engineered pivoting cradles. The auger is suspended from the crane jib by pennant ropes attached to hydraulic rams. The auger applies rotation and axial loads to the drilling tools via a telescopic steel bar (Kelly Bar). Drill tools are attached to the bottom of the Kelly Bar and comprise an assortment of drilling buckets and reaming barrels. Drilling buckets cut in situ material and collect the spoil for removal and are used for the excavation of the ‘pilot hole’. Reaming barrels are used to expand the diameter of the excavation by directing cuttings into the pilot hole which are then removed by the drilling bucket. In June 2010, the presink was constructed utilising a crane mounted auger with support to the shaft walls applied via a remote fibrecrete unit. The excavation method involved cutting a series of smaller diameter holes (2.4 m wide) before reaming out to the final diameter (4.7 m wide) in 4 - 5 m vertical increments. Fibrecreting activities were carried out on the backshifts, to ensure the stability of the excavation and minimise interaction between the two units. The presink was completed on time and offered many advantages compared to traditional blind sinking methods, including safety, costs and timing. This paper will examine the benefits of this method as well as lessons learnt and future applications in the mining industry.

Mar 21, 2011

By T Baumgartl, R I. Maczkowiack, O White, P D. Erskine

Queensland legislation, industry codes and policies relating to mine rehabilitation and closure create the expectation of successful progressive rehabilitation and that the post-mining environment is being returned to a condition suited to a pre-agreed, beneficial end use. Yet none of the rehabilitated mined land in the Bowen Basin has been certified as successful by authorities suggesting there is a gap between current rehabilitation and the full environmental outcomes that the legislation could deliver. We tested the veracity of this perspective and reflect on where responsibility for any discrepancy lies.We first reviewed current Queensland legislation and industry codes relating to stakeholder engagement, rehabilitation, closure planning and post-mining land use. We tested the accessibility of the documentation trail for several recent coal-mining projects in the Bowen Basin and examined the level of detail in approval documentation. We then assessed the rehabilitation performance reports of these mines in relation to the contents of their approval documents. Legislation, guidelines and codes repeatedly emphasise the need to plan for closure before mine operations begin and to progressively perform rehabilitation with an agreed end-use in mind. Early stakeholder involvement in these processes and transparency of actions and outcomes are also encouraged by government publications. Overall, in terms of transparency, we found that relevant documents are generally available to the persistent enquirer. However, the rehabilitation and closure undertakings given in both mine company and regulator documentation were commonly generic and rehabilitation obligations were not explicitly incorporated into rehabilitation plans. Rehabilitation reporting was also weak in that no distinction is required between successful and unsuccessful revegetation, nor to closure objectives and mine completion criteria. Responsibility for the apparent disconnect between regulatory intent and actual performance appears to begin with the regulator too readily allowing generic information and in not requiring performance reporting to correspond with approved post-mine conditions. As a result, companies may have a much greater rehabilitation and closure risk than mine management expects. More poignantly, the checks and balances that are in the legislation are not yielding the environmental outcomes of which they are capable.CITATION:White, O, Maczkowiack, R I, Erskine, P D and Baumgartl, T, 2012. Walk or talk - Is the current mine approval process in Queensland delivering rehabilitation and closure success?, in Proceedings Life-of-Mine 2012 , pp 59-68 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

The rocks of Waihi and the surrounding district are almost entirely rhyolitic and ande5itic in character. Sedimentary rocks, with the exception of some surface deposits of clay loosely compacted conglomerate, etc., and one or two thin and broken beds of a very poor lignite, occasionally changed by igneous agencies into a bituminous coal, are almost absent. In the shafts sunk by the Waihi and Grand Junction companies outside the outcropping andesitic area of the Martha Hill, more than one old surface or lake bottom has been passed through. At these points layers of sand, consolidated volcanic mud and tuff, accompanied by numerous broken fragments of imperfectly silicified wood have been enccuntered, but these occurrences may, for the purpose of this paper, be neglected.The youngest rock of the district are rhyolites, probably of Pliocene age. At least three distinct classes of rhyolitic lava, each possessing features of unusual interest, may be made out. None of these, however, is gold-bearing. The youngest flow, a light-coloured, fine-grained rock, is remarkable owing to its enclosing at times fragments of carbonised wood, varying in size from mere specks up to quite large pieces of almost pure charcoal. Rhyolitic tuff is also met with. The rhyolites cover a large extent of nearly flat country east, south, and west of Waibi, here and there rising into barren, stony hills.Below the rhyolites, geologically speaking, but for the most part. forming hills which bound the rhyolitic plain, or rise out of it as isolated patches, come ahdesites of older...

Jan 1, 1902

By Prasad S, Chatterjee S. S, Singh B. N

The chief source of metallic iron for steelmaking in India, even today, as it is in most part of the world, is through blast furnace (BF) route. This will continue to be so in the foreseeable future as the technology is most efficient, both process and economy-wise. However, as the world is moving into the next millennium, a critical look is being given to the process primarily because of its non-ecofriendliness (as a result of extensive use of metallurgical coal/coke requiring elaborate pollution control facilities) and huge investment involved for supporting facilities like extensive raw material preparation and handling, agglomeration, adoption of sophisticated instrumentation and control system, etc.

Jan 1, 1999

By R J. Beazley, M C. Woods

"The International Cyanide Management Code (the Code) is a voluntary industry program for gold miners and associated cyanide transporters and cyanide producers. By becoming a signatory, a company commits to follow the CodeÆs principles and implement its standards of practice.Signatories are required to undergo an initial certification audit within three years and a recertification audit every subsequent three years. Recertification audits evaluate compliance over the preceding three-year period. This approach presents a number of challenges. Golder Associates has undertaken in excess of 75 initial certification audits and 25 recertification audits; more than any other audit firm. This paper outlines some of the challenges identified and lessons learnt from the recertification audit process. Central to the process is the challenge for organisations to maintain commitment to compliance over the full three-year period and effectively address deficiencies or non-conformances that may have occurred during that period in a prompt manner.The International Cyanide Management Institute (ICMI) provides guidance in evaluating deficiencies or non-conformances, which requires consideration of the æcauseÆ, ædurationÆ and æongoing compliance effortsÆ and an assessment of the concept of ægood faithÆ in response actions. Golder AssociatesÆ experience with the recertification process highlights some common deficiencies with Code compliance programs, such as: system breakdowns (leading to ineffective communication between departments or loss of information) exceedance of discharge limits inadequate inspections, maintenance activities and associated record-keeping.Such deficiencies can be attributed to: personnel changes organisational changes or structures management systems (eg integrated or standalone) awareness and interpretation of Code requirements transparency of management decisions with Code implications.We have identified that ongoing programed assessment is an effective strategy in maintaining Code compliance.CITATION:Beazley, R J and Woods, M C, 2013. Cyanide code recertification - the three-year challenge, in Proceedings World Gold 2013, pp 247-254 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 26, 2013

Unrelieved residual strains can influence the states of stress in rock masses. If cheap, stable structures are to be constructed in Tock in which large pressures are exterted by unrelieved residual strains, the pressures must be either utilized or neutralized. A photoelastic technique has been used to show that the release of residual strains in rocks is influenced by the mechanical properties of anisotropic rock fabrics. The relationships between directions of residual strain release and the attitudes of minor geological structures have been determined. For engineering design purposes it is possible to estimate the principal stress directions in rock containing unrelieved residual strains if the attitudes of such minor geological structures as foliation planes, lineations, and joints are known.INTRODUCTIONQuarry workers have long been aware that near-surface rocks may be highly stressed. In many cases the stresses are too large to be the result of gravitational loads. Dale (1923, pp. 34-35) gives many instances of deformation produced by the violent release of residual strains in quarry rocks. Coates (1963) has described powerful rock bursts and cases of rock deformation underground implying the existence of much larger stresses than are likely to result from present-day gravitational loads. The only explanation is that pressures of up to several thousands of pounds per square inch may be caused by unrelieved residual strains in rock.Instruments have been developed for measuring states of stress in rock masses. Most stress determinations in rock have been made on the assumption that rock behaves as a simple elastic material. It is now known that rock is a...

Jan 1, 1964

At an early stage of the examination of most prospects, samples are taken; and the sample values obtained play an important part in determining the subsequent history of the prospect. It is, therefore, important that. eveJJy effort should be made to interpret asfully as possible the meaning of the observed results. In this connection, it is suggested that examination of the assay values of mine samples by simple statistical methods may bring to light information of considerable value, which might otherwise be missed.Although expert statisticians may derive more information from the available data, those who are, like the writer, less proficient mathematically, may also benefit by applying quite simple statistical methods. At least they will develop a useful habit of thought bywhich they become aware at all times that sampling results only provide estimates of the truth, but that an assessment of the precision of such results may be possible. The object of this paper is to provide some evidence of. the truth of these statements, by theuse of a few very elementary statistical calculations.General.The idea that any mine sample is subject to error from a variety of causes is a very familiar one. Doubt always exists with regard to the representativeness of a perfectly cut sample, and other errors may arise through imperfections of sample cutting, crushing, splitting and assaying. Some causes of error may give rise to "constant" errors, others may cause variable but one-sided "systematic" errors, and others again may bring about variable results without any tendency toward bias on the average. In statistical language, mine sample values are subject to errors which may have either assignable causes or chance causes. The former are those which can be isolated, or should be capable of isolation, while the latter are those remaining when all assignable causes have been removed. A single constant assignable cause brings about bias in all results, and one or more than one variable assignable cause brings about variation between individual results and perhaps an overall bias. The system of chance causes that would remain if all assignable causes were removed would cause variation between individual results but no overall bias. There is no sharp practical line of distinction between the two types of cause) of error; nor is it ever possible by any method of statistical analysis to be certain that there are no assign...

Jan 1, 1950

Drill cores from Section 62, New Broken Hill Consolidated Ltd., were used to study the petrology of rocks associated with the zinc lode. The distribution of the rock types in relation to the lode structure was determined. The distribution of the gahnite-bearing rocks was shown to be only partly conformable with the structure.It was concluded that large scale metasomatism was not widespread, that the rocks associated with the lode (except, perhaps, the quartz-gahnite-garnet rocks) were formed by metamorphism of sediments, and that rocks and lode were contemporaneously metamorphosed.INTRODUCTIONThis investigation was undertaken in order to study the rock types associated with the zinc lode of the Broken Hill orebody, and their relationship to the structure of the ore horizons. The work was confined almost entirely to the laboratory, and is therefore limited in its scope. It is hoped, however, that the information gained may throw some new light on the genesis of the lode.Certain inferences which are drawn from this work are at variance with the ideas of a number of earlier workers.In particular, the idea of large scale metasomatism developing many of the rocks associated with the lode, especially those containing manganese, is questioned. On the contrary, the rocks associated with the lode are more simply explained as highly metamorphosed sediments, in some cases modified by water introduced from surrounding rocks into zones of strong folding and faulting. As a corollary, a metamorphicsedimentary origin for the lode material, either as a concentrated sulphide deposit, or somewhat disseminated...

Jan 1, 1961

Variations in delay timing can have a marked influence on blasting effectiveness and, hence, on total production costs. In single-row bench blasts, delay firing is invariably more effective than simultaneous initiation. In single-row delayed blasts, there is an optimum inter-hole delay above and below which inferior blasting results are obtained. This optimum delay is equal to the time required for each charge to just effectively detach its quota of the burden. The inter-hole delay should seldom be less than 4 ms.m-l of burden.In multi-row blasts in which holes in a given effective row are fired on the same delay, the entire burden on any effective row should be detached from the rock mass just before charges in the next effeotive row detonate. Delays shorter than this give inferior blasting results and an increased likelihood of environmental and slope stability problems. If the inter-row delay is too long, cut-offs can occur, especially where the delay unit is located outside the blasthole. For a surface delay system, the optimum inter-row delay usually varies between 4 ms.m-l and 8 ms.m-l of effective burden. The number of rows that can be fired effectively with surface delay systems (in a single blast) is limited by the threat of cut-offs. Greater interrow delays and a larger number of rows per blast can be fired to advantage with down-the-hole delay systems.There are practical limits to the timing accuracy of all available delay systems. The existence of delay time variability should be recognized and duly considered in the design of blasts.The relationship between delay timing and blasting vibrations is not discussed.

Jan 1, 1977

By Cocquio D. S, Bauchau C

In the course of an integrated airborne survey in 1975, a uranium-molybdenum deposit was discovered by Minatome Australia Pty Limited in North Queensland, Australia, approximately 70 km by road west of Townsville.The mineralization occurs in a welded tuff unit within the Carboniferous St James Vokanics. It is structurally controlled by a complex of subvertical east-west fractures and is exposed over a strike length of 350 m. Drilling has traced a further 150 m extension underneath a barren capping consisting of a thick pile of vokano-sediments. The maximum width of the orebody is 150 m, and its vertical thickness is approximately 100 m.The primary ore minerals are coffinite, pitchblende and molybdenite, accompanied by various alteration products (particularly uranium molybdates).The vein-type mineralization is considered epigenetic.A comprehensive program of surface drilling and underground exploration is in progress to establish the uranium and molybdenum reserves.

Jan 1, 1980