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By H J. Stedman

A Transient Electromagnetic (TEM) geophysical survey was trialled in Bowen Basin Permian coal measures overprinted by Cretaceous intrusion. The trial’s intention was to compare whether TEM could assess residual coal more accurately and economically than drilling.TEM results were promising but had limitations. TEM did not compare to drilling for defining coal thickness or relative level definition. However, TEM resolved conductive anomalies laterally; providing a qualitative picture of remnant coal.Three material types and associated conductivities occur within the trial area: overburden (sandstone/siltstone), intrusive sills and heat affected coal.Ground conductivity was analysed by measuring decay of residual current within the TEM loop. Fast decay related to resistive overburden and intrusion, attenuated decay related to conductive coal.Generally speaking, carbon content governs coal resistivity where good quality, low ash, bright coal is more resistive relative to dull, high ash coal. Though in the trial area, relative to intrusion and overburden, coal was found to be the most conductive of the three materials.By modelling conductive anomalies, a general picture emerged of remnant coal regions. Subsequent highwall exposure reconciled with conductive TEM anomalies.CITATION:Stedman, H J, 2017. Findings from a transient electromagnetic trial for heat-affected coal, in Proceedings Tenth International Mining Geology Conference 2017, pp 233–238 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

Grade uncertainty can have a number of important implications for a mining operation. One of the most significant risks in not considering grade uncertainty in planning is the over or under allocation of processing or mining capacity when compared to realised grades. This could lead to wasted capital expenditure or missed opportunities to add value. This paper demonstrates a method that optimises production capacity and mining schedules in the presence of grade uncertainty. Applying this method to the case study of a nickel deposit recommended a reduction in processing capacity, an increase in mining capacity and more extensive utilisation of stockpiles than optimisations completed with traditional methods. As a result, average NPV improvements of between seven per cent and 27 per cent were gained.

Dec 6, 2010

By R L. Brathwaite, S E. Belliss

Linear and semi-circular features were mapped in the volcanic terrain of the southernCoromandel Peninsula, North Island, using JERS-1 synthetic aperture radar (SAR), Landsat-4 Thematic Mapper, and SPOT-2 multispectral satellite data, digital elevation models, and aeromagnetic data. The mapped features typically correspond to recognised physiographic features and are thus a useful aid to mapping the structural trends in the region. Major linear features exhibit a strong N-S to NNE-SSW alignment, and lesser NW-SE and NE-SW trends. All these are superimposed on pervasive, closely spaced, NNE-SSW and NNW-SSE lineaments present over most of the hilly parts of the map area. There are few major E-W aligned features. Some alignment trends correspond to strike directions of veins in the epithermal gold-silver deposits of the region, but none of the known mineralised structures were visible on the remote sensing data.   The volcanic rocks are Late Cenozoic in age and include a variety of rock types: andesite and dacite flows, domes and tuff breccias, rhyolite domes, tuffs and tephra, lacustrine siltstones, and ignimbrites. Mapping of different textures in the SAR image failed to provide additional information on rock types to that derived from the Landsat and SPOT images. A simple discrimination of rock units based on radar texture is apparently prevented by the complex volcanic geology, superimposed hydrothermal alteration, and long period of erosion.

Jan 1, 1994

By J E. Nethery

At the Red Dome and Mungana deposits in north Queensland, Australia, it is proposed that mineralisation and alteration developed as a 'telescoped' overprinting continuum, ranging in style from hypothermal to epithermal, reflecting the major changes that developed in the regional setting over the period circa 325 - 290 Ma. Regional assessment suggests that this also applies to many other precious and base metal deposits within a 40 km length of the host Siluro-Devonian Chillagoe Formation.   A ten stage paragenetic sequence of structural preparation, multi phase intrusion and associated mineralisation, alteration and brecciation is postulated for the Chillagoe district.

Jan 1, 1995

By B Lumsden

During periods of high metal prices and strong metal demand tailings retreatment can be economic. Most tailings retreatment operations are technically challenging, low margin operations, because the easily recovered mineral has already been removed, therefore, process improvements can potentially yield large economic benefits. The Hellyer tailings dam was owned by Intec Ltd and contained 10.9 million tonnes grading 2.8 per cent zinc, 3.0 per cent lead, 88 g/t of silver, 0.16 per cent copper and 2.6 g/t gold. In November 2006 the Polymetals Group, as operator, restarted the Hellyer plant to retreat these tailings. Within a few months the operation had stabilised and Polymetals was meeting budgeted targets of throughput, metal recovery and concentrate quality. Polymetals and Intec then investigated methods that would improve the metallurgical result for this difficult to treat tailings. Since the tailings are fine-grained with 80 per cent <45 ¦m, magnetic aggregation of the paramagnetic sphalerite was evaluated. Magnetic aggregation of an oxidised tailings feed has not been tested before, nor had the technology been available when Hellyer ore was originally processed. Extensive statistical test work showed magnetic aggregation of the sphalerite fines in the zinc cleaner circuit increased total zinc recovery. The increase in the mean zinc recovery with magnetic conditioning was 3.63 per cent, at a statistical level of confidence of 97.8 per cent, and at the same mean zinc concentrate grade.

Jan 1, 2009

By G B. Arehart, J L. Mauk

Quartz veins from the Martha Hill epithermal gold-silver deposit, Waihi, commonly exhibit crustiform banded textures. Visual differences observed between bands are primarily the result of a 1 to 1500 ¦m variation in quartz grain size. Quartz band textures are dominated by anhedral interlocking quartz mosaics, commonly associated with minor adularia and sulphide phases; these textures are interpreted to be products of amorphous silica crystallisation. The occurrence of rhombic adularia suggests that prolonged boiling influenced parent fluids. In contrast, the presence of coarsely crystalline bands, made up of subhedral to euhedral quartz grains, infers primary crystal growth from solution; evidenced by the occurrence of growth-zoned quartz within these bands. There is a narrow range of 3.3ë in d18Oquartz between maximum and minimum isotopic values for the deposit. Significant overlap in d18Oquartz values are observed between the Martha and Welcome lodes. However, statistically significant and commonly systematic differences do occur between individual bands analysed in most samples. Temperature fluctuations may be the dominant factor responsible for observed inter-band variation.

Jan 1, 1995

By J J. Culberson

The past 10 years has seen use of computers become widespread in the mining/exploration industry (including coal, precious and base metals, oil/gas and industrial minerals). This paper will concentrate on the use of computers as a tool to provide technical solutions (including data management, mine planning and operational support) to this industry rather than the use of computers to aid accounting, maintenance and inventory (æcommercialÆ) applications. This paper will review the processes and benefits of the use of computers in mining. We then review the use of technical computing locally here in New Zealand and see what business benefits local users have found from using computers in mining. We have, in research for this paper, spoken with mining software vendors from around the world to find out what is currently the æbest practiceÆ in the industry. The paper will then list what those vendors see as the ultimate improvement on the cards for the future of mining software.

Jan 1, 2000

Recent legislation in the environmental field gives the mining industry an opportunity to take timely action to address its image. Shifting the focus away from mining (the activity) to minerals (the resource) will enable the mining industry to stand on equal footing with other industries and will help minimise the vulnerability to political and interest groupsÆ interference.

Jan 1, 1993

By L Olivier, R J. Lowther, J L. Lett, I Brunton

Hydraulic fracturing to precondition the orebody to enhance rock mass cavability is gaining acceptance in underground cave mining applications. Assisting cavability is becoming important as an increasing number of cave mines are being implemented in hard, deep and competent rock masses where clamping stresses are higher and cave column heights may be in excess of 1000 m. Propagating large caves to surface in such conditions can be challenging as risks such as slowed propagation and air gaps can develop during the process.Underground-based hydraulic fracturing is routinely used at Cadia East as a means of preconditioning the orebody to assist in cave propagation, fragmentation and seismicity reduction. This paper presents a summary of a surface-based hydraulic fracture program that was successfully implemented to assist in the propagation of the Cadia East Panel Cave 1 (CE-PC1) cave to surface through competent overlying rock masses. In this case study, the propagation of the CE-PC1 cave slowed as the cave grew past 750 m in height, initiating a Trigger Action Response Plan regarding the cave propagation rate. Surface-based hydraulic fracturing was subsequently used to stimulate the cave to propagate through the final 450 m to surface. The paper details the equipment, strategy, implementation and risk management involved in the program as well as the key learnings.CITATION:Lowther, R J, Olivier, L, Lett, J L and Brunton, I, 2016. Implementation of a surface-based hydraulic fracturing program to successfully propagate a large cave through hard, competent near-surface rock masses to achieve breakthrough, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 83–96 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By M Humphreys

Multi-episodic mineralisation is often characterised by different spatial trends exhibited by different generations of the mineralisation. The structural complexity of mineralisation together with the heterogeneous nature of the mineralised zones prevents unambiguous application of the conventional deterministic methodology for 3D constraining of the mineralised domains (ie conventional wireframing is ambiguous).A different approach, discussed in the present paper, includes a probabilistic definition of the domains encompassing one statistical population of the data. The domains are defined geostatistically using the indicator probability model. An indicator threshold is chosen for the definition of the high and low-grade domains. The spatial distribution of this indicator is then modelled by a variogram. The probability of exceeding the given grade threshold is than estimated by ordinary kriging for each modelled block. Blocks are then grouped according to their probability of exceeding the threshold and a continuous closed volume (domain) created from this likely patchy grouping using an appropriate structural model to fill the gaps). Methodology for the geostatistically assisted domaining is discussed in the paper. It is suggested that this technique represents an additional tool facilitating a structural interpretation of the mineralised zones.After the geostatistical domaining of the lode has been completed the grade within each of the domains is modelled using Uniform Conditioning method. Application of Uniform Conditioning for modeling the grade distribution has a significant advantage over linear methods (such as inverse distance or kriging) because Uniform conditioning enables estimation of local recoverable resources at different selective mining unit sizes that can be substantially smaller than the drilling density and are unable to be estimated directly.

Jan 1, 2002

A model was developed of a CIL/CIP circuit for recovery of gold and silver. The model uses a simple two rate representation of the leaching kinetics. Parameters for the leaching kinetics may be simply obtained by sampling the feed to a circuit and the tailings from each tank and assaying the solids for both gold and silver to obtain the assay profiles of the solids down the tanks. The parameters in such a leaching model would be expected to be a function of the ore type, the grind, whether oxygen was used and the general chemical environment. These parameters are primary inputs to the model for any simulation. Standard power law relationships are used to express the practical equilibrium between the gold and silver cyanides adsorbed on the active carbon and the tenor of the solutions. The parameters for this may be derived from solution and carbon assays for the same set of samples. The model is constructed by writing a mass balance for gold and silver in and out of each tank in the train and for the circuit overall. Other inputs to a simulation are the feed rate of ore, per cent solids of the slurry in the tanks, gold and silver loadings of the input æbarrenÆ carbon and the rate of movement of carbon through the circuit counter-current to the slurry. With appropriate practical parameters the simulation is able to reproduce typical tank profiles.

Jan 1, 2004

By J Robinson, D Herbert

Bench stoping operations at the Isa Lead mine have been underway for over 11 years. They were implemented to address safety, productivity and mining cost concerns noted with cut and fill mining operations which were then being used to extract ore from the Racecourse orebodies. This paper describes the main features of benching operations at the Isa Lead mine and identifies the key elements for the success of the method. Four case histories are presented which highlight several of these factors.

Jan 1, 1998

By W Valery, S Morrell

In the mining industry blasts are usually designed to fracture the in situ rock mass and prepare it for excavation and subsequent transport. The run of mine (ROM) fragmentation is considered good when it is fine enough and loose enough to ensure efficient digging and loading operations. Mining optimisation strategy is hence usually focussed on minimising total mining costs and maintaining these ROM fragmentation characteristics. Although this approach ensures an efficient mining operation it ignores the potential impact on crushing and grinding. Investigations by several researchers have shown that designing blasts to produce ROM fragmentation to optimise crushing and grinding performance enhances the overall efficiency and profitability (Eloranta, 1995; Kojovic et al, 1995; Bulow et al, 1998; Kanchibotla et al, 1998; Scott et al, 1998; Simkus and Dance, 1998). Field experimentation in this area is often found to be difficult because of high implementation costs and insufficient understanding about the effect of fragmentation at different stages in a comminution circuit. Modelling and simulation of blasting and comminution processes provide a more economic alternative to explore the impact of blast design changes on the down stream operations (Kanchibotla et al, 1998; Kojovic et al, 1998; Adam and Siddall, 1998; Bulow et al, 1998). However, the reliability of such simulations depends on:the ability of the models to reproduce the physical processes that take place; characterisation of rock mass in terms of its blastability and comminution characteristics; and in the case of blast modelling the ability to predict fines (-10 mm) has been found to be particularly important as this fraction has a significant effect on mill throughput.

Jan 1, 1999

By R G. Barker

The NZ Minerals Industry Association has continued to advance the interests of the minerals sector through leading the establishment of a Minerals Industry Advisory Committee, and the preparation of a technology strategy with funding assistance from the Foundation for Research, Science and Technology. The current moves mirror those of more than 30 years ago when a government initiative led to a resurgence of exploration through amending the mining legislation, redirecting Government research priorities and tax changes. The economic and political and commercial environment in 2001 is very different from that of the 1960s and success of these new initiatives depends on the continuing support and involvement of all sectors of the minerals industry, and building an improved relationship with the Government and the public.

Jan 1, 2001

By A M. Nyembwe, A M. Garbers-Craig, R Cromarty

With the depletion of high-grade lump iron ore, concentrates have been identified as an alternative material for sinter making. Adding concentrates to the sinter mixture reduces sinter bed porosity and gas flow through the sinter bed. This will result in lower sinter strand productivity. A potential solution to this problem is to add concentrate in the form of micropellets. This study investigates the effect of concentrate and micropellet additions on the permeability of the sinter mixture. Permeability was measured on sinter mixtures containing ten to 40 per cent concentrates and micropellets at various moisture contents. The effect of concentrate and micropellet addition on the permeability–moisture relationship was examined. The results confirmed that the addition of concentrates into the sinter mix decreases the maximum permeability of the sinter bed. The incorporation of micropellets into the sinter mix reduced the permeability less than concentrate addition. The study also showed that the maximum permeability of sinter mixes containing concentrate is reached at the same moisture content as the sinter mixture without concentrate addition. For sinter mixes containing micropellets, additional water must be added to obtain maximum permeability. Parameters including the granule size, void fraction and angle of repose were also investigated to evaluate their effects on the sinter bed permeability.CITATION:Nyembwe, A M, Cromarty, R and Garbers-Craig, A M, 2015. Effect of concentrate and micropellet addition on iron ore sinter bed permeability, in Proceedings Iron Ore 2015, pp 69–76 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By K J. Thompson

This paper describes the work which has been undertaken at the Ohai coalfields in Southland to restore overburden heaps during past opencast mining operations, and procedures which have been adopted to ensure that restoration is achieved concurrent with present opencast mining activities. The system implemented for the treatment of wastewater from opencast mining operati6ns is also described.

Jan 1, 1981

Selective Recovery of Platinum from Cobalt-Rich Crust

Sep 13, 2010

By D C. Grant, D J. Goudie, E Baird

The Scanning Electron Microscope – Mineral Liberation Analyzer (SEM-MLA) laboratory, as part of the Core Research Equipment and Instrument Training (CREAIT) network of laboratories at Memorial University, NL, Canada, has recently published efforts towards increasing the throughput of automated mineralogy systems by producing single-step trans-vertical moulds, rather than traditional 30 mm polished epoxy moulds. Due to the small particle size of iron ore grains in the -200 mesh size fraction (<75 µm), not all of the surface area on a mould is needed for measurement in achieving good statistical representation. In a new study, trimming of the excess area of a mould results in a smaller sample and increases the quantity of unique samples that can fit in a newly designed trans-vertical adapter for a FEITM MLA 650 field emission gun (FEG) scanning electron microscope. The complete analysis, using a newly designed sample block holder capable of holding 98 samples, required 57 hours of running time where each sample had an average of 33?400 particles measured and identified. The analysis was calibrated to allow for off-line discrimination of hematite/magnetite. The calculated Fe-assay values derived from MLA results were compared to those from bulk sample chemical assay. This shows the Fe assay having a correlation coefficient of >0.99 when the particle count is greater than 20?000. This study represents the most expedient method yet reported to prepare well-polished samples and analyse them in a timely manner that can allow for quicker results in process mineralogy.CITATION:Grant, D C, Goudie, D J and Baird, E, 2017. Analysis of individual - mesh iron ore samples in a single Scanning electron microscope automated mineralogy session, in Proceedings Iron Ore 2017, pp 535–540 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By D J. Black

Ventilation modelling is used to evaluate ventilation system performance. This paper describes modelling to assess potential changes to a single entry longwall ventilation circuit to improve ventilation and gas management. The longwall panel is extracting a 215 metre face in a 1.5 metre coal seam at a depth of 900 to 1000 metres below surface. The 1.5 metre B seam is located approximately 25 metres below the main 3.0 metre A seam and the gas content of both coal seams is approximately 20 to 25 m3/t. The B seam is extracted prior to the A seam and the mine relies on fracturing of the overlying strata to induce gas emission from the A seam to reduce the gas content prior to mining. Longwall operations in the B seam are constrained by limited ventilation and high gas emissions. Due in part to statutory limits on gas concentration and air velocity, the average longwall production rate is approximately 700 t per day.Gate roads in the B seam are single entry, developed using road headers and supported with steel arches. Additional timber cog support is installed to reduce roadway closure from abutment loading. Due to the slow advance of gate road development, mine management were reluctant to consider significant mine design changes, such as two heading gate roads; therefore, the investigation focused on determining the extent to which ventilation and gas emission impacted on longwall production performance, while recommending short-term, low-cost actions to improve ventilation and gas management to support increased longwall production.CITATION:Black, D J, 2017. Application of modelling to improve ventilation and gas management in a single-entry longwall panel, in Proceedings Australian Mine Vent Conference 2017, pp 239–244 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

By D Kotzen

Online cyanide analysers have been successfully used to control free cyanide in the gold/silver leach process for over 15 years. Use of such analysers leads to cyanide savings and improvement in recoveries. Plants with leach cyanide analysers show both lower and more consistent cyanide levels in tailings. Cyanide code compliance requires meeting residual cyanide targets in tailings. Monitoring and logging of the residual cyanide in plant tailings and effluent is required. Meeting targets may require cyanide recovery/destruction processes to be implemented. The operating cost of destroying cyanide is often the same order of magnitude as the cyanidation cost. Various cyanide destruction and/or recovery processes are reviewed. Choice of a process consistent with the environmental and operational requirements is illustrated. Online weak acid dissociable cyanide (CNWAD) analysers have recently been developed and introduced on gold plants. The application of a WAD 1000 online CNWAD analyser at a large gold plant is presented. The analyser ensures code compliance, reduces cyanide destruction process operating costs and forms a historical record of CNWAD values in tailings.

Jan 1, 2007