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Low displacement fault zones often comprise a mesh of interlinked faults, extensional-shear and purely extensional vein fractures. Hydrothermal mineralisation localised around such structures testifies to their importance as conduits for fluid flow. Mesh structures are most commonly developed in situations approximating bulk pure shear but predominantly simple shear meshes also occur. They appear to develop through the infiltration of pressurised fluids into a heterogeneous rock mass with varying material properties. In some circumstances, mesh formation appears to be a precursor to the development of major through going faults. Mesh formation generally involves hydrofracturing (Pf > s3, at least locally) and the condition Pf ~ s3 to be maintained for the mesh to remain a high permeability conduit, requiring fluid over pressuring at other than shallow depths in extensional-transtensional regimes. The volumetric character of earthquake swarm activity appears to result from the passage of hydrothermal fluids through mesh structures, representing a form of distributed fault-valve action along suprahydrostatic hydraulic gradients arising from magmatic intrusion, compaction overpressuring, metamorphic dewatering, etc. Fluid redistribution in the crust is influenced by maximum hydraulic gradient (not necessarily vertical), by existing permeability anisotropy arising from bedding and other forms of crustal layering, and by structural permeability developed under the prevailing stress field. Strong directional permeability develops in the s2 direction, parallel to fault-fracture intersections within the mesh and orthogonal to fault slip vectors. In particular tectonic settings, stress-controlled permeability allows strongly focused flow through fault-fracture meshes with high potential for mineralisation. Favoured localities for mesh development include short-lived link structures along large-displacement fault zones such as dilational jogs, lateral ramps, and transfer faults.

Jan 1, 1995

Development and Validation of Ore Characterisation Test and its Use in Variability Campaigns of Comminution Circuits Impact testing was developed by assessing the fragmentation characteristics of ore samples after controlled impact. Standard methods are, however, limited to relatively large and coarse samples, which thus precludes their use in early stages of projects, as well as where only drill cores are available. The method described in this paper is based on the same concepts of controlled ore breakage, but using relatively smaller samples. It is particularly useful in assessing the variability of ore characteristics in early stages of greenfield projects, as well as in predicting the performance of existing grinding circuits. A validation program was carried out in which a good adherence to the original test results was obtained. The results were used for (a) simulation of a copper comminution circuit as a function of the ore characteristics, and (b) evaluation of sampling protocols used for assessing fragmentation characteristics.

Sep 13, 2010

Investigation of the Classification Operation in a Coal Pulverising Vertical Spindle Mill Coal pulverisation in power plants is a major electrical energy consumer. In 2006 more than 41 per cent of world electricity generation was from coal where pulverisers use 0.5 to 1 per cent of gross generation. Therefore, pulverisers are an important target for optimisation not only for reducing costs of power generation but also for reduction of greenhouse gas emissions. A better understanding of the operation of pulverisers is an essential requirement for their optimisation. However, little information is available, other than operating experience, on the performance of pulverisers and how these react to changes in operational variables. This study investigates the effect of changes in coal and airflow feed rates on the classification performance that occurs in an industrial scale ball-and-race vertical spindle mill in which the pulverisation and classification processes are linked together due to the separator classifier being an integral component within the pulveriser. In order to decouple the breakage and classification processes, samples were cut from upward flowing streams through sampling ports drilled on the pulveriser body at different locations. Specific sampling tools were developed. Samples collected from the pulveriser were size and density fractioned to distinguish the differences in behaviour of the components, namely coal and mineral matter. The coal flow rates on dry basis within the mill and around the separator classifier were calculated by mass balancing the multi-component data. The difference in classification behaviour of components during pneumatic transport was confirmed. The response of the circulating load in the mill (~600 to ~1100 per cent) as well as the dependency of fineness of the streams to the operating variables was demonstrated. The approach taken in this study has proved that development of a classification model for a vertical spindle mill pulverising non-homogeneous materials, eg coal, requires treating these materials as multi-component/composite substances.

Sep 13, 2010

The resource industry must prepare for the inevitable shift towards automation as an operational objective. Although this may seem like a distant concern, many mining companies and equipment manufacturers are already conducting full-scale automation trials. The necessary technology is advancing at a rapid pace yet the training of people to support it at the trade level lags far behind. Those given the responsibility of installing and maintaining automated equipment in the mining environment require a unique set of skills and knowledge. These training needs demand attention to ensure that the wider uptake of automation is sustainable and achieves its full potential.   This paper documents work undertaken by CRCMining and the Mining Industry Skills Centre towards establishing a training framework seeking to address the needs of trade level personnel tasked with the support of automation equipment. A comprehensive definition of the skills and knowledge required by the hypothetical automation-specialised tradesperson is presented. The training pathway identified for these personnel is also described. This work forms part of the Mining Industry Skills Centre's Automation Skills Formation Strategy, funded by the Queensland Department of Education and Training.

Jun 1, 2010

By C A. Feebrey, R A. Duncan

The Ebor Volcano in north eastern New South Wales is an eroded example of a central-type intraplate volcanic-intrusive complex. It is of Miocene age (19 - 20 Ma) and has similarities to other central-type volcanoes in eastern Australia which may represent manifestations of sub-lithospheric hotspot activity. Thick lava flows are exposed around the Great Escarpment and are dominated by a tholeiitic basaltic suite, ranging from ol-tholeiite to qz-tholeiite to icelandite with ages of 19.2 - 19.6 Ma. On its western edge, the tholeiitic lava suite probably overlies remnants of basanite flows belonging to the Eocene (~48 Ma) Doughboy province, but elsewhere, minor alkaline basaltic lavas may be coeval with the tholeiitic suite. Several felsic bodies were emplaced into the volcano at ~19.0 - 19.2 Ma and include subalkaline and peralkaline types. The Crescent Complex is a Miocene-age, strongly differentiated mafic to felsic intrusion in basement rocks and centrally located in pre-erosion reconstructions of the Ebor Volcano. It is interpreted to be a major feeder for the tholeiitic lavas based on age and composition. Evolution of the dominant tholeiitic suite proceeded from a parental ol-tholeiite magma, through qz-tholeiite, icelandite and small volumes of felsic rocks by fractionation of plagioclase, olivine, clinopyroxene and titanomagnetite, accompanied by enrichmentof SiO2, SFeOlMgO, alkalies and HFSE.

Jan 1, 1995

By M Amanzadeh, S M. Aminossadati, B M. Masum, M S. Kizil, C R. Leonardi

Gas sensing systems are becoming more important in many industries such as oil, gas and mining operations. Particularly in underground coalmines, accurate and reliable monitoring of toxic and combustible gases such as methane, nitrogen dioxide, carbon monoxide and hydrogen sulfide is essential. Available conventional electrochemical sensors for gas measurements in underground coalmines suffer from shortcomings such as cross-sensitivity response, limited lifetime, high calibration cost, maintenance cost and safety. Recent studies have found that fibre optic-based gas sensors have potential to eliminate these issues. These sensors can also be used for long distance and distributed sensing of various gases, both of which are important for underground gas monitoring. The aim of this paper is to review the present underground mining gas monitoring systems and review the new generation of fibre optic-based sensing systems for use in underground coalmines.CITATION:Masum, B M, Aminossadati, S M, Leonardi, C R, Kizil, M S and Amanzadeh, M, 2017. New generation of gas sensors for underground coal mining applications, in Proceedings Australian Mine Vent Conference 2017, pp 189–196 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

By S G. Keyte

Gravity methods of recovering alluvial gold are not very efficient at particle sizes below about 0.l mm. Whereas such gold may not have been economic to recover in the past, the same may not be true today. Centrifugal concentrators, like the Knudsen and Knelson bowls, are showing promise after an inauspicious start, at least in New Zealand. The large proportion of heavy mineral in many auriferous beach sands and the natural hydrophobicity of fine gold should make flotation an attractive contender for its recovery. The conventional mechanical flotation cell is effective, but roughing, scavenging and cleaning are necessary to achieve both high recovery and low mass Yield. More problematic is the difficulty of maintaining coarse and dense sands in suspension. The air sparged hydrocyclone is effective at recovering fine gold from a fine Colarado River sand, but is not effective for the coarse and dense beach sands of New Zealand. The flotation column shows much promise for these sands, when recoveries of over 80 per cent and mass yields of less than one per cent can be achieved in a single pass. The froth separator of the USSR and flash flotation could also be worthy contenders. It is felt that flotation could be limited to naturally and artificially de-slimed concentrates.

Jan 1, 1990

Gold was first discovered in the Shotover by Thomas Arthur in 1862. He left his job as a shearer and soon there were up to 3000 miners working over the length of the river. Some parts were extremely rich and a few early miners recovered as much as 300 ounces in a day. From these early days of hand working the operations progressed through to hydraulic elevating once water races and pipes were installed after the Skippers road was completed about 1890. The riverbed was worked in paddocks with .the gravel being sluiced to a central suction which elevated the material over a sluice box. Use of this system continued intermittently through until 1977 when Joe Schieb retired û the last of the hydraulic miners. Many bucket ladder dredges worked on the lower Shotover near Big Beach where the Sew Hoy family recovered a lot of gold. Just after 1900, at least three worked further upstream, one on the beach where Shotover Jet now operates and one further up below the Moonlight. All the sections for this were transported in over the Moonlight Track and the boiler, steam engine and bucket ladder are still sitting at the edge of the river. up near Maori Point a dredge operated from Dredge Slip upstream. Records are poor on these dredges but they all suffered from the frequent floods and large boulders which damaged the bucket line. The last dredging attempt was about 1930 when a suction dredge was constructed on Maori Beach. This failed as seems to be normal for most suction dredging ventures. The river can drop to very low levels in the middle of a dry summer, and in winter when the water is tied up in the mountains as ice and snow. During 1863 when heavy rain melted snow in the high country, the river rose 35 feet overnight and drowned many miners camped on the banks. The ever present risk of flooding dominates the method of working and plant design.

Jan 1, 1987

Study on Ball Mill Grinding of a Cassiterite-Polymetallic Sulfide Ore

Sep 13, 2010

Electronic noses are being used in the processing industries and in fields such as environmental and occupational hygiene to detect a wide variety of problems from contaminated foods to toxic chemicals in soils. Recently, research has been conducted into the use of these devices for detecting spontaneous combustion in mines with the aim of producing a method for early detection of a developing heating. Gas samples were collected from both SimtarsÆ 16 m3 large-scale spontaneous combustion reactor and the University of QueenslandÆs two-metre column. The samples were analysed using an electronic nose. GCMS and HPLC were used to identify some of the components present. A number of issues both from a practical mine situation and a scientific standpoint have been identified that need to be addressed before these devices can be used to detect a developing heating. Aluminised bags routinely used in the mining industry to collect gas samples for analysis of the permanent gases are not suitable for use with electronic nose devices as they have a æfingerprintÆ from the polymer lining that interferes with the coal heating fingerprint. Tedlar bags used for environmental gas sampling are also unsuitable due to their fingerprint. Gas samples can be collected in glass gas bulbs with aluminium seals and successfully analysed. However the aluminium foil used to seal the bulbs is a restricted item in underground mines. It was also found that the volatile organic fingerprint of the coal heating was extremely weak at temperatures below 130¦C. Before a useful application can be developed, further investigation into the chemical species present in the off-gases from Australian coals is required.

Jan 1, 2005

Old Copper Flotation Tailings Waste Reprocessing

Sep 13, 2010

By F P. Hao

Organo-sulphur-based collectors (eg xanthates, dithiocarbamates and dithiophosphates) are widely used in the flotation of sulphide minerals. Xanthates (ROC(=S)Sû), for example, adsorb strongly at sulphide mineral surfaces, in a reaction that is electrochemically coupled with the reduction of dissolved oxygen. One of the oxygen reduction products, hydrogen peroxide, reacts directly with dissolved xanthate, leading to its oxidative decomposition. Experimental work has been conducted, using ethyl xanthate, to understand the molecular mechanism by which hydrogen peroxide reacts with xanthates. A number of degradation products have been identified, some of which have not been reported previously. This oxidative decomposition reaction pathway is discussed in the broader context of xanthate decomposition in flotation systems. One of the identified ethyl xanthate decomposition products, ethyl perxanthate (ROC(=S)SOû), has been observed in the process water of a number of mineral processing operations. The interaction of this molecule with goethite (α-FeOOH) particles, typical of that found in tailings dams, has been studied in more detail using attenuated total reflectance (ATR)-FTIR. The ethyl perxanthate molecule has been found to coordinate to iron (FeIII) at the goethite surface, and undergo a surface-catalysed decomposition process. In the presence of both PbII and goethite, a ternary surface complex is formed, where ethyl perxanthate is coordinated directly to surface adsorbed PbII atoms. The results obtained give some insight into the environmental fate of ethyl xanthate in tailings streams, and a basis on which to consider the environmental importance of such species in tailings dams. Strategies for the destruction of residual xanthate levels in waste water streams are discussed in terms of the likely reaction products.

Jan 1, 2002

By M Baker

Biodiversity offsets are conservation actions intended to compensate for the residual, unavoidable harm to biodiversity caused by development projects. The use of biodiversity offsets in the context of mining has significant potential for enabling mining to take place in areas with biodiversity values, where it would not otherwise be possible to meet the relevant legal tests under the Resource Management Act 1991, and potentially the Conservation Act 1987. This paper looks at the concept of biodiversity offsets (and environmental compensation generally) both in New Zealand and internationally, and considers how lessons learned overseas may be adapted for this country. In New Zealand the practice of biodiversity offsets and environmental compensation is ad hoc and variable. The challenge with biodiversity offsets is to establish a transparent and coherent means of identifying the overall priorities and objectives of adopting such an approach, as well as how the relevant values are measured and protected. Establishing a methodology for quantifying biodiversity value, and the need for clear policy guidelines on biodiversity offsets are identified as key areas in need of wider discussion.

Jan 1, 2007

Kinetic Study on the Leaching of Vanadium from LD Converter Slag Using Sulfuric Acid In order to reduce the environmental impact due to land disposal of LD (Linz-Donawitz) converter slag from steelmaking plant and to valorise this waste material, an acid leaching study was carried out to assess the effect of several parameters on the kinetics of vanadium dissolution. The characterisation and morphology of the feed investigated using XRD, XRF. The factors influencing leaching vanadium such as particle size, temperature, slurry density and the concentration of sulfuric acid were investigated and optimised. The maximum vanadium recovery about 95 per cent achieved at 70¦C, S/L: 1/15, acid concentration: 3M and for 150 minutes of leaching time. The dissolution of vanadium in sulfuric acid shows that there are two stages in the kinetics of leaching. At the first 15 minutes, there is a sharp increase in the amount of vanadium extracted and at longer leaching time, the extraction increase slightly. In the present work, the shrinking core model (SCM) was used to describe the acid leaching of vanadium compounds. A summary of the controlling regimes in the SCM are examined below for short time (less than 12 min.) and long time (more than 30 min.) stages. So, it was found that the kinetics of leaching in both stages is controlled by solid product diffusion regime.

Sep 13, 2010

By C A. Locke

Geophysical signatures of the Taranaki and Tongariro volcanoes reflect similarities in their age, composition and hydrothermal histories, but also reflect differences in host rock settings and edifice evolution. The Taranaki volcanoes have strong positive gravity anomalies showing that their edifices largely consist of dense andesite which reflects substantial lava production or dyke injection during construction and that large sub-edifice dyke/stock complexes occur. In contrast, the Tongariro volcanoes have strong negative gravity anomalies indicating low density edifices of volcaniclastic material; no sub-edifice intrusions can be identified, probably because of the lack of density contrast with host basement rocks. Strong positive magnetic anomalies over the younger cones can mainly be attributed to near-surface andesite lavas or dykes whereas subdued magnetic effects are associated with hydrothermally altered zones within both edifices and sub-edifice intrusions.  

Jan 1, 1995

A fundamental component of grade control at Tarmoola Mine has been the monitoring of assaying through quality assurance programs. The programs have concentrated on issues related to accuracy and precision of leachwell and fire assay techniques, sample preparation and grade variability within a sample. An outcome of monitoring has been identification of shortcomings in the application of assaying techniques to Tarmoola ore types that contain coarse particulate gold. Leachwell has shown satisfactory precision since introduction as the primary assay technique in October 1998 but leachwell accuracy and recovery through comparison with fire assay techniques has identified bias. A bias toward higher fire assays in grades above 2 g/t invoked an investigation into the cause of the discrepancy between leachwell and fire assay. Testwork evaluated Leachwell assay recovery by varying leach time duration, which showed that by increasing the leach time improved recovery significantly. Monitoring of leachwell against fire assay had shown that a leachwell (200 g) with a one hour leach has under-called grade when compared with fire assay by up to 18 per cent, on average, for Tarmoola ore types. Alternatively, optimisation of the leachwell assaying technique using a 200 g pulp and a two hour leach has returned, on average, higher assays than fire assay by up to eight per cent. Testwork on screen fire assays, duplicate assays and fire assay to extinction has demonstrated assay variability associated with coarse, particulate gold. The variability and distribution of gold in Tarmoola ore types has emphasised the importance of high quality sample preparation for leachwell assaying to ensure liberation of gold to leaching solutions. Assay quality assurance protocols are vital to assay data integrity and enable confidence in delineation of ore-waste boundaries and provide early recognition of problematic assaying periods and isolation of grade control practices, which depart from performance standards critical to the operation.

Jan 1, 2000

By H W. Wu

The objective of this paper is to examine some modern forms of auxiliary ventilation fabric ducting with streamline design fittings and the efficiency of construction practices. The most dynamic form of auxiliary ventilation is a moveable fan and ducting, which is easy to install and uses light weight fabric. The porous nature of some ducting construction results in leakage and loss of efficiency. Flexible fabric ducting is primarily associated with metalliferous mining and industrial material quarrying. Some applications are found in coal in stone/rock development and with use of dust scrubbers.Forcing auxiliary ventilation systems employing circular fabric ducting have been examined. Leakage of air from ducting is affected by ducting material and construction methodology (such as welded or sewn), quality of installation, number of joints, total length, pressure differences between the inside and outside and diameter. The best ducting system with welded construction can have up to four times less leakage as compared with some systems with sewn construction. It is also evident that the sewn type ducting will deliver less air to working faces and require more fan power, hence higher operating costs to run when connected to the same fan.A case study has also been undertaken to compare predicted operating costs of auxiliary ventilation systems connecting various types of ventilation duct fittings. The study also assesses the technical importance of streamline design with low aerodynamic resistance to reduce the shock losses of the duct fittings. It was found that the system connected with streamline designed fittings is able to provide some power cost savings and deliver more air compared with the system fitted with conventional fitting pieces.Using a ventilation ducting system with a lower leakage and frictional characteristic represents a sound solution to new challenges faced by the industry for increasing demand for better quantities and quality of air delivered to working faces; this is due to higher production schedules and stricter mine health and safety regulations within the Australian mining industry.CITATION:Wu, H W and Gillies, A D S, 2017. A comparison of auxiliary ventilation systems and their predicted operational performances, in Proceedings Australian Mine Vent Conference 2017, pp 207–214 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

Improving the Sustainability of Primary Metal Production - The Need for a Life Cycle Approach

Sep 13, 2010

Core samples, which were collected by the author from the Busang prospect, East Kalimantan, reflect a progressive evolution of a large magmatic-related hydrothermal system that is comparable to that encountered in many similar systems elsewhere in the Pacific region. The initial, localized deposition of sheeted porphyry quartz-molybdenite veins took place at high temperatures and fluid salinities, and at relatively deep levels. This was followed by an extensive phase of phyllic (sericite-quartz-pyrite ¦ tourmaline-apatite) wallrock replacement and vein formation. Propylitic (epidote-chlorite-carbonate-quartz) alteration was formed marginal to the phyllic assemblages. These porphyry-related events were centred in the Southeast Zone, and are probably associated with the emplacement of a felsic intrusion at depth. This event contributed only trace gold to the system. The early stages of hydrothermal activity were followed by an episode of quartz (¦ adularia) û carbonate û base metal sulfide veining, which was accompanied by argillic (illitic-kaolin clay) wallrock alteration. This event was sulfide-rich in the Central Zone and carbonate-dominated in the Southeast Zone. Gold mineralisation was observed in Central Zone drillcore to be associated with both sulfide, as well as carbonate, deposition. A final stage of epithermal-style quartz ¦ stibnite û realgar veins are, in the Central Zone, locally gold-bearing. The latter two events are interpreted to be associated with the late-stage exsolution of metal-bearing brines from the felsic intrusion that formed the earlier porphyry quartz-molybdenite veins and widespread phyllic-propylitic alteration.

Jan 1, 2002

By H Mali, B Kain-Bückner

Different types of lump iron ore-bearing particles were investigated in terms of their raw material properties depending on their behaviour during reduction. To predict the reduction behaviour different types of lump iron ore and pellet brands were characterised by their mineral abundance, texture and pore size. The image processing software VisuMet was developed to semi-automate the evaluation of photomicrographs from polished sections of lumpy iron particles. The results were compared to the standard reducibility test after ISO 4695. The evaluation of lump iron ores is based on the simulation of the transformation of the different iron minerals due to their sequence of reducibility. The progress of the reduction front is simulated and the result is a degradation curve. Pellets were also investigated due to their different pore size distribution. The results indicate that the pore size influences the reducibility in addition to mineral abundance. The evaluation with VisuMet of the lump iron ore and pellet samples correlates with the reducibility provided by the ISO 4695 test. The determination of the mineral abundance by VisuMet is comparable to common point counting with a correlation coefficient of 99.67 per cent.CITATION:Kain-Bückner, B and Mali, H, 2017. VisuMet – analyses of lumpy iron carriers with image processing, in Proceedings Iron Ore 2017, pp 557–560 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017