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Discovered in 1896, the Sons of Gwalia orebody is located in a ductile mylonite zone within a sequence of Archaean pillow metabasalts and minor metasediments of greenschist facies which are variably sheared.The ore zone has good continuity, being 110 m wide and 500 m long, dipping 45 degrees east and plunging 70 degrees to the south to a depth of 1500 m downplunge. A strongly-developed foliation is present together with a prominent lineation paralleling the plunge. The mylonite zone consists of unmineralised chlorite schist and a 'U' shaped mineralised zone of chlorite-sericite schist with varying amounts of quartz-carbonate as veins parallel to foliation, boudins, and locally as massive quartz-carbonate. Pyrite is the dominant sulphide present.Grade control utilises RC holes on a 10 m x 10 m pattern, with infill blast rig holes 5 m deep where necessary.Some visual control of ore boundaries is present and, combined with good ore continuity and a knowledge of the structure of the orebody, enables cost-effective grade control to be achieved. To-date, over three million ounces of gold have been produced from the orebody.

Jan 1, 1993

By Orr T. O H, Hodkinson I. P

The Mount Leyshon breccia complex is located on an east-west trending contact between Cambrian metasediments (Puddler Creek Formation) and the Ordovician Mt. Leyshon granite, within the Lolworth-Ravenswood block. Detailed mapping of basement, breccia and igneous unit geometries, crosscutting relationships and resolution of complex chronological relation- ships indicates that the Mt. Leyshon breccia complex should be reinterpreted as a number of intrusive igneous and breccia phases. This is in contrast to a previously published account of a largely extrusive geological setting. A complex structural history dominated by strike-slip faulting is preserved within the basement units and is responsible for controlling the location and geometry of the breccia complex. The breccia complex has been divided into brecciated "basement", "main pipe breccia" and an "interactive magma/breccia sequence". Main pipe breccia (the most voluminous unit within the complex) has been re-interpreted as an intrusive breccia, rather than an extrusive or vent fill as previously proposed. This is based on the following evidence: 1. the facies characteristics of the main pipe breccia, 2. the presence of a progression from cohesive basement through to mixed breccia, 3. minor basement block rotation during breccia complex formation, and 4. the partial structural control on the main pipe breccia. No unambiguous evidence exists for pyroclastic facies, although the fine breccia variant commonly contains "accretionary structures", very similar in appearance to those formed during pyroclastic processes. In view of 1. above, they are interpreted to be the product of particle accretion during upward movement of fragmental material, although an origin due to altera- tion cannot be completely discounted. heir occurrence in the main pipe breccia indicates that their presence within a rock unit is not necessarily diagnostic of nvroclastic nroeesses.

Jan 1, 1991

Resource rent tax is a form of taxation or royalty, which only become effective at such a time as a pre-determined rate of return has been achieved by an operation. The offshore petroleum industry in Australia is already subject to RRT as is the Roxby Downs (Olympic Dam) Mine in South Australia. Both the mining and petroleum taxation regimes in Papua New Guinea include a resource rent tax component called Additional Profits Tax (APT). The implications of the current form of Additional Profits Tax for shareholder cash returns are that the tax burden on the operation may suddenly increase at some stage in the life of the mine, if and when the threshold level of profitability for the tax to be triggered is exceeded. From that point in time onwards the cash return to the shareholders on the capital invested is greatly diminished. For mining companies in Papua New Guinea, the effective tax rate increases from 35% to 57.75% as a result of the onset of Additional Profits Tax. This tax rate penalty is so severe that there appears to be merit in considering the concept of managing profitability through time rather than purely maximising annual pre-tax profits as is currently the case in most mining operations. This would have the benefit of deferring or perhaps preventing altogether the onset of the tax. One possible method for the effective management of profitability is through the control of average mining grade by cutoff grade manipulation. Traditional cutoff grade theory has usually considered taxation as a direct cost at a fixed or variable percentage of annual profits. As a result of this most analyses are conducted on a pre-tax basis. If tax is included in analyses it is usually present as a time independent function of gross profit. Additional Profits Tax is both time and rate of return dependent and therefore not adequately accommodated by currently accepted cutoff grade theory. A review has been made of the effects of resource rent taxes on both the investment decision-making process as well as possible development and mining strategies which may be employed by mining companies faced with Additional Profits Tax. The review includes examples based on the structure of Additional Profits Tax which is levied in Papua New Guinea.

Jan 1, 1997

Mining companies in order to compete and succeed in being viable business propositions must look to the future and select mining methods which guarantee improved efficiency and productivity as well as lower costs.A mining company in adopting a method of mining must now select the equipment most compatible. To some mines compatible equipment may mean the use of drilling jumbos to replace hand held rock drills or the use of load haul dump units to replace scrapers. To other more mechanized mines compatible equipment may mean the use of raise borers and road heading machines. The right decision will be where equipment compliments method in such a way that the working environment is improved, productivity is maximized, cost if reduced and all profit opportunities are optimized. An example of such is where the use of improved mining techniques in underground operations may see cut off grades reduced. By selectively mining these lower grade orebodies, smaller operation's ore reserves improve and the capacity for continued growth is enhanced.

Jan 1, 1990

By V N. Rudashevsky, N S. Rudashevsky

Characterisation of platinum-group element (PGE) deposits and their process products has many challenges for the process or applied mineralogist. It is now well established that the PGE distribution for such samples is variably divided between submicroscopic concentrations of PGE in sulfides, tellurides and related minerals occurring as discrete platinum-group minerals (PGM), of which there are a large number of species, many with partial replacement between the PGE and between anions. Each PGE deposit type requires a targeted approach but fundamentally, there are two general methodologies in vogue. One way is to make a large number of polished or polished thin sections for detailed scanning electron microscopy (SEM)/optical examination to determine the PGM distribution and their associations and grain sizes. The other is to make concentrates of representative crushed or processed samples, thus having fewer subsamples to examine. Our method of choice is to use hydroseparation (HS) for concentration. HS provides representative concentrates of sizes down to ~10 ¦m, not possible by other techniques. Various microbeam methods have been used for analysis of trace quantities of PGE (EPMA, micro-PIXE, SIMS and LAM-ICPMS). We prefer LAM-ICPMS (laser ablation microprobe û inductively coupled mass spectrometry) because of the relatively large analytical volume sampled, the ability to measure all the PGE, monitor up to 20 elements, together with detection levels in the tens to a few hundreds of ppb. We provide typical results derived in studies of stratiform PGE ores and tailings, and a massive Ni-Cu sulfide ore.

Jan 1, 2008

By Jagger N. D

Lead residue from the Zinc Leach Plant at Pasminco's Port Pirie Lead Smelter was previously filtered on a vacuum drum filter and further dried in a gas fired rotary kiln prior to stockpiling and transport to the Sinter Plant. This process involved several materials handling stages, recycled significant amounts of zinc and often resulted in poor environmental conditions. These problems have been overcome by pumping the thickened leach residue approximately 450m to the Sinter Plant where it is filtered in a Larox Automatic Pressure Filter. The filter cake is discharged onto a conveyor belt, held in a storage hopper and then fed directly to the main sinter plant feed stream. Filtrate is returned to the process for additional zinc recovery. The laboratory and pilot plant filtration results are briefly discussed and compared with the operating plant data. The filter installation and ancillaries are described in detail along with the commissioning, operating and maintenance experience over the past 4 years. This installation has overcome the environmental and materials handling problems and resulted in annual savings of approximately $1 million.

Jan 1, 1989

By OÆGrady P

Finite element analysis is becoming a routine component of design of longwall extractions, now superseding more traditional somewhat intuitive approaches. Finite element modelling is relatively inexpensive and provides an adequate degree of similitude to give satisfactory analysis. The physical modelling of two decades ago is now largely replaced by numerical methods of which finite element is the best known. Important data for finite element work are physical properties, including creep aspects, introducing the non-linearity of stress response.Various computer packages are available and some were used to model two specific UK examples, using both linear and non-linear approaches. It appears that non-linear approaches will yield most benefit. The use of materially non-linear analysis is merited by the greater similitude it provides between model output and real mine situations.

Jan 1, 1991

By Hilde TWC

Synthesis of GLORIA side-scan sonar and other geophysical data has provided morpholo- gical and tectonic details of the interaction between the Nazca and South American plates along the Peru Trench (80S-15¦S). Our analyses suggest that a new propagating rift of the Galapagos type is evolving along the Mendana Fracture Zone (MFZ). Subduction induced rift- ing of the Nazca plate is accompanied by organized seafloor spreading for the last 3 Ma at least. GLORIA sonographs and bathymetric mapping show an 8-10¦ divergence in MFZ width towards the Peru Trench. The fracture zone comprises numerous ridges and troughs and a lack of sediment cover in the axial part. Young magnetic lineations (anomalies 1-2A) are observed within the fracture zone wni.cn are orthogonal to the older Nazca plate lineations. The central anomaly narrows west- ward and can be observed up to 400 km seaward of the trench whereas anomaly 2A is terminated about 200 km from the trench axis. Recent SeaMARC II sonar mapping in the region shows large igneous blocks in the Trench axis to the north of MFZ but absent to the south. We believe these blocks represent young seafloor of MFZ rift/spreading center broken off from the ridges as they subduct along the Peru Trench. The MFZ rift is propagating west- ward at a rate of 115 km/Ma (25 km/Ma relative to the South American plate). Given the present rates of accretion at the East Pacific Rise and of propagation along MFZ rift, the Nazca plate will be divided into two parts in about 35 Ma.

Jan 1, 1987

By T Sirinawin, R H. Murfitt, W Shywolup

The Bong Mieu Project lies within the Pre-Palaeozoic Kontum Craton near the southern margin of the regional Phuoc Son û Tam Ky Suture. The Suture and accompanying Truongson Fold Belt of Indosinian age host significant gold and base-metal bearing districts including OlympusÆ other project at Phuoc Son to the west of Bong Mieu and OxianaÆs Sepon project in Laos. The Bong Mieu Project is located some 90 km south of Da Nang and some 30 km south-west of Tam Ky, the provincial capital of Quang Nam province in central Vietnam. The project area is covered by an Investment Licence of some 30 km2 which was granted in 1991 and a mining permit of some 365 ha granted in 1992. Several mesothermal, gold-silver deposits with assigned resources are present on the property. Deposits with assigned resources contain some 615 000 ounces of gold in situ. These are at Ho Gan and Ho Ray which are potentially exploitable by open-pit mining and Nui Kem which is potentially exploitable by underground mining. Newly discovered extensions to the known deposits at Ho Gan, Ho Ray and Nui Kem, and several other new prospects, are currently being investigated by drilling. The Ho Gan mineralisation is of mesothermal, shear and shear breccia quartz vein, as well as intrusive breccia hosted style. Nui Kem mineralisation is of mesothermal, shear and shear breccia quartz vein style. The Ho Ray mineralisation is of skarn (gold-bismuth-tungsten) and lesser quartz vein style. The deposits straddle and flank the east-west trending Bong Mieu Anticline which trends through the central portion of the Investment Licence. In this paper the geology of the deposits, details of resources, results of recent exploration on the Investment Licence and recent engineering and mining studies at Ho Gan are briefly reviewed.

Jan 1, 2004

By Lynce AJ

A method has been developed for the prediction 'of 'the- . performance of a multi-stage grinding=cyclone classification circuit of any degree of complexity on any ore for a wide range `of operating conditions, The-.method involves ;the. s` inu ation b'f the circuit on a digital computer by means of. matheinatical' models ":bf the"' individual units:, the. development of which is- also discussed'., At present, in order to establish 'the!'" charac'teristtics of they ¦ore- and the machines. in mathematical terms;. it is necessary to know'the performance of a , simpl,.e. ; system on tri.e ore - for! one known ,,feed rate and.fe.ed s,l-zing, analysis. ' ,Fiiither work on :the- separate identification 'of the terms defining the characteristics of the ore and the machines may permit the method to be, applied directly to the cj.4ta,derived from small scale tests on ores,

Jan 1, 1964

By Brockway DJ, Holmes RJ

A natural gamma-ray gauge has been devel- oped for discriminating overburden and inter- seam sediment from low ash coal located on a moving conveyor belt. It is based on the difference in natural radioactivity of the sediment and overburden compared with the low ash coal, which is detected with a highly ef- ficient "Polyscin" NaI(T1) gamma-ray detector located underneath the conveyor. Gauges have been successfully installed on the bucket wheel boom of the two coal dredgers at the Loy Yang Open Cut. They are used to warn dredger operators that they are digging overburden or sediment and that action is required to avoid the sediment or divert it to the waste dump rather than send it to the coal bunkers at the power station.

Jan 1, 1987

A case study of a landslide, which threatened vital infrastructure essential for the continuous operation of the Ok Tedi copper mine is presented. The paper presents a detailed description of the land- slide, outlines the assets at risk, and how the issue was addressed. This included the consideration of remedial options and the im- plementation of the most economically sound and geotechnically feasible remedial design which was completed within budget and on schedule. The paper is intended to highlight the responsibility of a mine based Geotechnical Engineering section in providing essential geotechnical investigations, design and professional advice on addressing stability issues in the infrastructure region.

Jan 1, 1997

The middle-Devonian Dulladerry Volcanics is a complex of A-type, predominantly rhyolitic ignimbrites, lavas and breccias. They form a NNW trending belt some 90 km long and 10-20 km wide, east of Parkes, NSW. The volcanics are dominated by widespread ignimbrite units with minor basalts, sediments and rarer andesites. The volcanics were deposited in a sub-aerial, possibly continental rift setting and are similar in chemistry and age to the Eden - Comerong - Yalwal Volcanic Zone (EVZ) on the NSW south coast. The volcanics exhibit an unusual Atype chemistry (high Zr, Y, Nb, REE, Ga). This distinctive composition illustrates that the volcanics are not comagmatic with the adjacent Yeoval Granite Complex or Eugowra Granite, which show typical I-type fractionation trends. Epithermal gold veins occur in basalt and andesite in the Dulladerry Volcanics at Mt Aubrey (Hopf, 1992), near Baldry. Alteration also occurs in the Glen Isla and Red Hill areas, with epithermal sinter recognised at Glen Isla. Copper and minor gold mineralisation occurs at the contact of rhyolite and andesite at Reedy Creek, but is not of epithermal origin. The analogous EVZ also contains several epithermal gold fields and it is this style of mineralisation which provides the most prospective targets in the Dulladerry Volcanics. Although the Dulladerry Volcanics also contain high background levels of REE and metals such as Zn and Pb, the general lack of fractionation and water-undersaturated character of A-type magmas does not lend itself to the development of significant concentrations of these elements into a fluid phase and mineralisation. The prospectivity of A-type volcanics in general could not be regarded as high. However, an indicator of some fractionation in the Dulladerry Volcanics is provided by the fairly low abundance (average 230 ppm) and wide range (

Jan 1, 1995

By Brown GA

Results are presented which demonstrate the feasibility of employing electrolytic membrane technology to process leach liquors derived from alkaline pressure leaching of scheelite concentrates and to recover and recyle sodium carbonate. Thus the problem of disposal of sodium sulphate is avoided. In a further application of the technique sodium tungstate is converted to tungstic acid which can be further processed by three possible routes to crystalline or amorphous tungstic acid or tungsten powder. In each route sodium hydroxide is produced which on carbonation can be recycled as soda ash to the pressure leach stage. Further testwork is required to determine long term operational conditions in the membrane cell and to confirm the effect and deportment of impurities on products. The process has been patented.

Jan 1, 1986

By Burnett C. C H

GEMNet, (Grade Estimation using Mapping Networks), is a grade/reserve estimation software system that uses the artificial intelligence technique known as neural networks to perform reserve estimates from both two- and three-dimensional data samples from a mineral deposit. The system is the result of research carried out over the past three years into the feasibility of using neural networks for reserve estimation at the AIMS Research Unit in the Department of Mineral Resources Engineering at the University of Nottingham. This paper describes the architecture of the GEMNet system including details of the neural network components of the system. The performance of the GEMNet system is then compared to several other widely used reserve estimation techniques on two reserve estimation examples. The results produced by the GEMNet system compare favourably with more conventional estimation techniques, but require fewer assumptions to be made about the form of the data used, and do not require the use of complex mathematical modelling.

Jan 1, 1995

By Veloso L, Alvarez O, David D

Cerro Colorado operations The Cerro Colorado Mine is located 150 km east of Iquique in the Atacama desert of northern Chile. The mine is wholly owned by Rio Algom Limited of Canada and produces copper metal using a bio leaching process. Tw

Jan 1, 1998

By Grantham DL

ABS'TRACT For a number of years research efforts have been directed towards improving the efficiency of sampling and analysing coal mine roadway dusts. In the past decade the practicality of rapid, on site analysis of the incombustible content of these dusts using a radioactive technique has been receiving close attention both in Australia and overseas. Accurate measurement of the total incombustibles present is only possible by time consuming chemical methods. As the densities of the solid incombustible materials are greater than that of coal, they absorb a higher proportion of incident low energy gamma radiation than does coal. The amount of such radiation "back scattered" from mine dust samples is therefore inversely related to their average densities, and hence to their incombustible contents. This phenomenon can be used as a measure of incombustible content by employing an appropriately designed and calibrated instrument.

Jan 1, 1981

By T Clemens, D Trumm

Adopting environmentally acceptable practices in New Zealand is a crucial requirement for mineral wealth development. Recent planned expansions in the coal industry have increasingly placed mining in the media spotlight. A lack of appropriate national environmental guidelines has resulted in inconsistent responses and assessments of current and prospective mine sites. Such inconsistencies have lead to delays in decisions on developing economic mineral deposits that may have only minor short-term impacts, and have also allowed unacceptable environmental management practices to continue elsewhere.   A research collaboration between CRL Energy, Landcare Research, University of Canterbury and University of Otago aims to provide regulator groups and the mining industry with a unified approach to the requirements of the Resource Management Act 1991, which is the legislation that predominantly drives the nationÆs environmental policies and guidelines. The tangible outcome of this research programme will be guidelines for an integrated decision-making framework based upon robust multidisciplinary science. The result of this unified process will facilitate the development of viable mineral deposits and prevent excessive environmental impacts.   The framework will be derived from a synthesis of four objectives. Objective 1 identifies potential water quality impact. This objective is based on a targeted geochemical study of the lithology and waterways of the West Coast and Southland. Objective 2 categorises the degree of impacts on the ecology of receiving aquatic ecosystems and determines the processes that drive aquatic ecosystem recovery. Objective 3 identifies best strategies to sufficiently manage impacted ecosystems, and to prevent future unacceptable impacts. Objective 4 combines the findings of Objectives 1 - 3 into a standard decision-making framework. The development of this framework development will include wide consultation with representatives of the mining industry and regulator groups. It is anticipated that this multidisciplinary approach will provide a robust and coherent, standardised system that will assist in achieving industry and environmental targets.

Jan 1, 2004

By R Morrison, P Owen

Particle breakage is an essential part of mineral processing. The aim is to reduce run of mine mineral ore to an optimal size for liberating target minerals and for subsequent recovery by separation processes such as flotation. This size reduction is typically accomplished in a series of stages in a grinding circuit tailored to the properties of the particular mine ore. Commonly this involves two or more classes of equipment starting with crushers, followed by SAG mills and then sometimes ball mills. Occasionally, high pressure grinding rolls or other novel devices are substituted. Broadly, energy consumption increases and energy efficiency decreases with the fineness of the material produced by each piece of equipment. For many operations, up to 50 or 60 per cent of total greenhouse gas emissions from a plant arise from the operation of the comminution circuit with the majority produced by the finest grinding parts, such as the SAG and ball mills. Wear of mill liners and grinding media also add to greenhouse gas emissions generated by their manufacture. The need for continual cost reduction and increasing regulatory and social pressure relating to greenhouse emissions create a strong need for improvements in comminution energy efficiency. Traditional experimental and modelling approaches are not well placed to create the required insights into comminution fundamentals or facilitate radical step changes in performance. This paper discusses the role that advanced modelling (based on coupled DEM and CFD) can play in improving the energy efficiency and performance of existing mainstream grinding equipment and in the development of new ones with radically superior performance. Achieving this goal will also require an improved understanding of ore breakage and methods to include sufficiently realistic breakage models within the DEM models. Developmental issues for the modelling and the critical need for validation of the advanced model features are highlighted.

Jan 1, 2004

By C E. Loo

The cohesive zone has a significant influence on blast furnace operation and performance. The high-temperature behaviour of the reducing ferrous burden determines the properties of the cohesive zone and is studied in a laboratory using a softening and melting test. This paper summarises recent work aimed at better understanding the physico-chemical changes in a ferrous bed during softening and melting. Using a combination of standard, non-standard and quenched tests supported by optical image analysis, this work has highlighted some important differences in behaviour between lump, pellets and sinter as well as between the two lump ores and two acid pellets. As with the two lump ores, one pellet is denser than the other and the denser ore/pellet is also higher in silica.Within the cohesive zone, densification of the ferrous layer leads to reduced permeability and greater pressure drop. From the work presented in this paper, two key mechanisms of ferrous layer densification were identified. Firstly, the formation of fayalite, which melts at low temperatures, can act as a lubricant between particles and lead to densification of the ferrous layer under load. Secondly, reduction to metallic iron is topochemical and fayalite in the outer shell of the particle restricts gas flow to the centre and results in the formation of a wustite core. As temperatures rise, the wustite melts and eventually exudes out of the shell, occupying void spaces between particles and further reducing layer voidage and permeability.This work has shown that density and silica content are two key factors that result in increased densification of the ferrous layer. For porous Australian lump ore, the higher porosity and lower silica reduces the formation of fayalite and limits the formation of the wustite core, ultimately leading to a more permeable bed. The difference between the porous and dense ores was more pronounced with the introduction of prereduction to better simulate blast furnace conditions. This suggests that a porous ore gives significantly better cohesive zone permeability and blast furnace operations than a dense ore.The behaviour of fluxed sinter particles is different in that the silica reacts with lime to form dicalcium silicate. Minimal wustite core forms because relict hematite particles in sinter are only small and reduction occurs uniformly throughout the particle. Even with significant loss of material through prereduction, beds formed from sinter remained comparatively rigid. Studies using a typical blast furnace burden mix of 80 per cent fluxed sinter and 20 per cent porous ore showed that the structures of these beds at softening and melting temperatures are very similar to the sinter-only test. Measurements of bed contraction and pressure drop also confirmed that the introduction of 20 per cent porous ore into a sinter bed did not alter its properties. This is an indication that 20 per cent ore can be easily accommodated by blast furnace burdens.CITATION:Loo, C E, 2015. Important acid ferrous burden properties in the cohesive zone of a blast furnace, in Proceedings Iron Ore 2015, pp 367–376 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015