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By C A. Locke, J Cassidy, J L. Mauk

The Waihi-Waitekauri region hosts numerous low-sulfidation epithermal deposits that both outcrop and occur at depth. Zones of intense hydrothermal alteration enclose the Au-Ag bearing quartz vein deposits. Hydrothermal alteration includes the destruction of magnetite by hydrothermal fluids, pervasive silicification adjacent to quartz lodes and potassium enrichment due to adularia and illite deposition. High-resolution airborne magnetic and radiometric, and new gravity data delineate distinct geophysical anomalies associated with hydrothermal alteration and mineralisation. Five magnetically quiet zones occur in the region varying in size from 3 to 34 km2 and in geometry from circular to irregular zones. These zones represent the near-surface extent of strong to intense hydrothermal alteration associated with fossil geothermal systems. All epithermal deposits in the region occur in magnetically quiet zones. Over 120 new gravity stations together with existing data across the Waihi district have defined a positive Bouguer gravity anomaly coincident with the magnetically quiet zone. Eastern and western gradients of 50 gu/km bound the anomaly that contains two flat gravity highs west and east of the Waihi deposit. Strong potassium signatures in airborne radiometric data correlate with outcropping zones of alteration and are consistent with the presence of adularia and illite minerals. Hydrothermally altered zones are represented by areas of low Th/K ratios as a result of low thorium concentrations in andesite and elevated potassium levels in altered zones.

Jan 1, 2003

Reverse Cationic Flotation of Iron Ores - Floatability of Amphiboles at Depression of Iron Oxides by Starch

Sep 13, 2010

By N F. Fraser

Seafield ResourcesÆ offshore placer gold project covers c.10 000 km2 of the Westland continental shelf between Karamea and Jacksons Head, from the low-water mark out to the 120 m isobath (Figure 1). De Beers Marine (DBM), the marine diamond subsidiary of the De Beers Group, will carry out the project with geological input from Placer Solutions (PSL). DBM bring a wealth of expertise and advanced technology to the project, developed during their 20 years of exploration and mining of diamond placers on the Atlantic shelf of southern Africa, where they have also maintained a strong environmental record.   Glaciers and high-energy rivers emanating from the Southern Alps have transported substantial quantities of gold bearing sediment onto the Westland continental shelf during Pleistocene glacial periods, when fluvial gradients are steeper, sea level is c.120 m lower and most of the shelf is exposed. These deposits have been extensively reworked by the advancing shoreline and marine processes during interglacial marine transgressions, and most are now buried beneath a variable thickness of post-glacial marine sand, silt and mud. DBM will use side-scan sonar, swath bathymetry, Chirp sub-bottom profiling and a magnetometer to map the sea floor and sediments beneath it, guided by PSLÆs predictive geological model for gold distribution on the shelf. Cactus grab and vibro-core samples will be used to ground-truth the geophysics and provide stratigraphic, sedimentological and gold distribution data for incorporation into the geological model. Areas of interest identified by the geophysical and sampling data will be investigated in more detail, with closer-spaced geophysics and Mega-drill sampling to a maximum sediment depth of 20 m beneath the sea floor. These samples will be raised to the ship with air-lift suction technology, processed onboard for mineralogical and grade information, then returned to the sea floor. Environmental baseline data will be gathered from Van Veen grab samples of seabed sediment taken throughout the area during the prospecting programme.

Jan 1, 2005

By B Saunders, J Carpenter

PanAust’s Phu Kham copper-gold operation (Phu Kham) in Laos is currently limited by throughput in the Semi Autogenous Grinding (SAG) mill. The ability to accurately predict SAG mill throughput (throughput) is therefore critical to accurately forecast copper and gold production. During the fourth quarter of 2016 the proportion of hard unweathered rocks in the mill feed increased, resulting in a period of lower than expected throughput. These low throughput rates prompted a study with the aim of identifying a practical solution for throughput predictions. The study identified an empirical modelling approach based on actual SAG mill throughput rates. The empirical model was then optimised by linear programming to identify the ideal feed blend of unweathered rocks to achieve a maximum SAG mill throughput.Rock strength was the initial focus of the throughput study at Phu Kham because previous studies had identified a strong link between rock strength and throughput. It was determined that there was insufficient valid data to adequately model but sufficient data to qualitatively characterise rock strength. The data identified that the weathering and lithology had a controlling influence on the rock strength. Complicating throughput predictions were operational improvements (changes to blasting and mill settings) implemented in response to the lower than expected throughput. This created uncertainty with the throughput equations. A self-learning empirical modelling method was developed to predict the throughput by incorporating fundamental rock properties with operational practices and improvements. The method is based on the proportion of mill feed with similar weathering and lithology (a proxy for comminution performance) and the actual mill throughput using the SAG mill as the analytical instrument. The modelling method simultaneously incorporated the sum and interaction of unmodelled influences including blasting, crushing and mill settings. The empirical modelling method worked at Phu Kham because the lithology and weathering has an intuitive and observable controlling influence on SAG mill throughput. The modelling method is described along with a worked example of feed blend optimisation using linear programming.CITATION:Carpenter, J and Saunders, B, 2017. Empirical mill throughput modelling and linear programming for blend optimisation at the Phu Kham copper-gold operation, Laos, in Proceedings Tenth International Mining Geology Conference 2017, pp 291–296 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By J Bang, I-H Jung

Ti is an important constituent for steels and superalloys. During the continuous casting process and ElectroSlag Remelting process (ESR), Ti in molten steel and superalloy can have chemical reactions with casting flux and ESR slag containing CaO and CaF2. In order to investigate such exchange reactions, the understanding of the (Ca,Ti//O,F) reciprocal slag system is prerequisite. In the present study, a coupled phase diagram experiment and thermodynamic modelling of the (Ca,Ti//O,F) reciprocal system was performed. In particular, the phase diagram of the CaF2-TiO2 system was experimentally investigated by Differential Thermal Analysis (DTA) experiment and quenching experiments followed by Electron Probe MicroAnalysis (EPMA) phase analysis. The Gibbs energy functions of all solid and liquid phases in the (Ca,Ti//O,F) reciprocal system were optimised to reproduce the present data and all available reliable experimental data in literature.

Jun 19, 2024

Removal of Arsenic in Fluorite Ore by Simultaneous Grinding-Leaching with NaHS Generally speaking, a high-grade fluorite ore is converted into hydrogen fluoride (HF), which is essential for the semiconductor manufacturing. With the continuous depletion of resources, novel technologies for processing low-grade fluorite ores are urgently needed, in order to lower the arsenic concentration to less than 100 mg/kg. In this study, a low-grade fluorite ore was upgraded by removing arsenic, which is difficult to remove by conventional method. The mechano-chemical leaching of fluorite ore (i.e. the sample was ground in presence of NaHS, using a beads mill) was carried out to investigate the removal of arsenic from the low-grade fluorite. Experimental results showed that the arsenic concentration was reduced to 73.2 mg/kg.

Sep 13, 2010

By R G. Barker, A B. Christie

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. More than 11 Moz of Au and 50 Moz of Ag have been produced from epithermal deposits in New Zealand, almost entirely from 50 deposits in the Hauraki goldfield. Since the 1980s, new deposits have been discovered at Waihi (Favona, Trio, Correnso) and nearby at Golden Cross. Feasibility studies into reopening the Talisman mine at Karangahake are continuing, and advanced projects with preliminary inferred resource estimates are reported at Wharekirauponga, Neavesville and Muirs. In the Taupo Volcanic Zone, 11 prospects have been drilled, resulting in the definition of large but low-grade Au-Ag resources at Ohakuri. In Northland, several Au, Ag and/or Hg prospects are known, and small quantities of Ag and Hg have been mined. Six prospects have had some drilling, with the most advanced exploration at Puhipuhi. The application of Taupo Volcanic Zone geothermal systems research to the modelling of former hydrothermal mineralising processes in some epithermal prospects has enabled better targeting of exploration.CITATION:Christie, A B and Barker, R G, 2015. Exploration for epithermal gold deposits in New Zealand, in Proceedings PACRIM 2015 Congress, pp 533–540 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

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

The spatial and temporal evolution from the porphyry to high-sulphidation epithermal environment can be assessed by integrating new results on such deposits (Arribas et al, 1995; Hedenquist et al, 1998) with past studies of plutonic and porphyry systems (Dilles and Proffett, 1995; Cline, 1995; Shinohara and Hedenquist, 1997; Hedenquist and Richards, 1998). Some time ago, Sillitoe (1973) argued for the nature of the tops and bottoms of porphyry deposits. He concluded that epithermal deposits may form over the tops of some porphyry systems. We can now conclude more confidently what the tops and bottoms of many high-sulphidation ore deposits appeared like while active (Arribas, 1995; Hedenquist, 1995). In addition, we better understand the nature of the zonation of high-sulphidation epithermal systems from the intrusive to surficial environment (Sillitoe, 1999), and how these two styles of ore deposit are related. Geological and geochemical evidence clearly indicates a continuum between these two ore environments. This improved understanding of genesis allows more efficient exploration for these deposits. There are many examples of spatially associated porphyry and epithermal ore deposits. A genetic connection has been suggested by some, and argued against by others. Nowhere is this spatial association better seen than in northern Luzon, Philippines, where the Lepanto high-sulphidation epithermal Cu-Au deposit overlies the Far Southeast (FSE) porphyry Cu-Au resource (Figure 1). Together these mineralised bodies contain a resource of >3.8 M tonnes Cu and >550 tonnes Au. Lepanto was largely mined out in early-1997. Post-war production until 1995 was 0.73 Mt Cu, 115 t Au and 393 t Ag at an average grade of 2.2 per cent Cu, 3.5 g/t Au and 11 g/t Ag. The recent discovery of the adjacent Victoria low-sulphidation quartz-Au-base metal vein deposit, with a resource of >68 tonnes Au (Cuison et al, 1998), illustrates the variety and abundance of mineralisation in the Mankayan district. This district also hosts the Guinaoang porphyry Cu-Au deposit (Sillitoe and Angeles, 1985) and other epithermal vein occurrences (Figure 1). This brief summary reviews the results recently published on the Lepanto-FSE deposits (Arribas et al, 1995; Mancano and Campbell, 1995; Claveria, 1998; Hedenquist et al, 1998), and stresses the evidence for coupling of mineralisation between the porphyry and high-sulphidation epithermal environments.

Jan 1, 1999

By R Aseervatham

The fast tracked mine development strategy attempts to blend feasibility studies and engineering/commissioning functions into a streamlined process. In this compressed process, environmental issues are difficult to control with respect to the optimisation of operational environmental performance. This paper presents a standard mine development process with specific focus on environmental issues, and contrasts this against Rio TintoÆs recent fast track experiences on the Hail Creek project (Australia), the Baranj project (India) and the Gokwe North project (Zimbabwe).

Jan 1, 1999

By M A. Knackstedt

Coupling between deformation processes and rock permeability is a major factor influencing the architecture of fluid migration and the localisation of ore deposition in several types of hydrothermal ore systems in middle to upper crustal regimes. Permeability in many hydrothermal systems is controlled by a dynamic competition between deformation-induced porosity-creation processes and porosity-destruction processes. Localisation of deformation within faults, fractures and shear zones leads to flow localisation, with large-scale flow systems forming when active faults and shear zones link to create percolation networks. Numerical modelling techniques are used to explore the growth of fracture networks and evolution of network connectivity during progressive deformation. Initial results indicate that networks reach a percolation threshold at very low strains. Near the percolation threshold, flow is localised along a small proportion of the total fracture population and favours localised ore deposition. At higher strains, flow is distributed more widely throughout the fracture population and may provide reduced potential for production of high-grade deposits. The distribution of mesothermal gold deposits along a small subset of the total population of co-active faults and shear zones in the Archaean Yilgarn Craton in Western Australia indicates that some hydrothermal systems maintain themselves near the percolation threshold for a substantial part of the lifetime of the system. Fluid-driven growth of fault/fracture/shear networks may lead them to self-organise near the percolation threshold.

Jan 1, 1999

By H Q. Zhang, M C Chai, W Fu, H Y Chen, L M. Wei, Q J. Yang

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Fozichong deposit – located in the south-western segment of the giant Qinhang metallogenic belt, South China – is a large-sized lead-zinc polymetallic deposit. This deposit contains two main ore districts, termed as the Guyi ore district in the north and the Hesan ore district in the south respectively. We present an integrated data set on sulfide minerals, fluid inclusions and stable isotope (H-O-S-Pb) geochemistry to better understand the features and genesis of the Fozichong deposit.Field and paragenetic relationships indicate three mineralisation stages forming the early (Po+Sp+Gn+Ccp+Py+Di+Ep+Qtz), middle (Sp+Gn+Ccp+Py+Ep+Chl+Qtz) and late (Gn+Sp+Py+Qtz+Cal) sulfide assemblages respectively. Mineral chemistry – particularly S/Fe and Co/Ni ratios in pyrite, Zn/Fe, Zn/Mn and Zn/Cd ratios in sphalerite and Pb/Ag ratios in galena – indicates a magmatic association for the sulfide minerals.Quartz and calcite coexisting with the sulfide minerals of various stages host abundant fluid inclusions. Quartz in the early stage contains two- or three-phase CO2-H2O and liquid-rich aqueous inclusions, which have homogenisation temperatures of 162~365°C and salinities of 2.9~17.8 wt per cent NaClequiv, whereas quartz and calcite from the middle and late stages are dominated by two-phase, liquid-rich aqueous inclusions that have slightly lower homogenisation temperatures (153°C~320°C) and much lower salinities (1.0~6.0 wt per cent NaClequiv). Hydrogen isotopes (dD = -59‰~-41‰), analysed using fluid inclusion waters from quartz and calculated oxygen isotopes (d18OH2O = -5.47‰~4.00‰) for the equilibrated ore fluids, indicate that the ore-forming fluids may have been sourced from magma and mixed with groundwater in the late stages. Sulfide minerals have d34S values of 2.3‰~4.3‰, consistent with a magmatic-derived source for sulfur. Lead isotopes (206Pb/204Pb = 18.592~18.794, 207Pb/204Pb = 15.648~15.864, 208Pb/204Pb = 38.909~39.580) confirm that lead and, by inference, zinc were mainly derived from magmatic rocks, with subordinate contributions from sedimentary rocks.Various lines of evidence support that the formation of the Fozichong deposit has close genetic association with the granite porphyry intruded in the late Yanshanian period (106 Ma), and it can be classified as a magmatic hydrothermal type lead-zinc deposit. We propose that the Hesan and Guyi ore districts may represent the proximal and distal products of a magmatic – hydrothermal system respectively.CITATION:Fu, W, Zhang, H Q, Chai, M C, Yang, Q J, Chen, H Y and Wei, L M, 2015. Genesis of the large-sized Fozichong lead-zinc polymetallic deposit, Guangxi, south China – constraints from the sulfide mineralogy, fluid inclusions and isotope geochemistry , in Proceedings PACRIM 2015 Congress, pp 609–614 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By A T. Job, P R. McAree

There is significant value at stake in the mining industry from the implementation of new technologies that support the enhanced profitability and sustainability of mines. However, in order to realise this value, new technology must be implemented in a way that is both effective and sustainable. The industry has a mixed history for technology implementation that provides fertile ground for understanding what is necessary for innovation to deliver value. This paper describes early stage research investigating why this is so, with the aim of improving how to deliver value. Several case studies are provided covering both successful and unsuccessful technology interventions. The paper identifies the common factors that emerge from the case studies, and offers a path forward for further research in this area.CITATION:Job, A T and McAree, P R, 2017. Three case studies on the implementation of new technology in the mining industry, in Proceedings Iron Ore 2017, pp 407–414 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By S Jahn, M Noel, E M. Rykaart, M Pau

Three soil cover test areas were constructed on waste rock backfilled into the Lichtenberg Pit, near Ronneburg Germany. A fourth, uncovered area was included as a control. Each test area measures 50 m by 65 m, and was constructed using full-scale equipment and construction practices. Extensive material sampling and testing was included as part of the construction. Devices were installed in each plot to monitor meteorology, infiltration, run-off, interflow, soil moisture, soil temperature, and soil pore gases. Boreholes were completed in each area and instrumented for temperature, pressure and pore gas sampling to a depth of approximately 60 m. Data from the monitoring instruments have been collected since July 2000, and have been comprehensively analysed and modelled on two occasions. The paper presents an overview of the test area design and instrumentation and the results of the two comprehensive data reviews. The reliability of the various monitoring methods is discussed and experience with several innovative methods is reviewed. The difficulties encountered in modelling the data set using common soil physical models are discussed.

Jan 1, 2003

The mining industry continues to be a major driver of the Australian economy generating over A$130 billion in export earnings in 2008/2009. However, the industry has been cited as a significant contributor to green house gas emissions. Australia's proposed carbon trading scheme, the Carbon Pollution Reduction Scheme (CPRS) will financially impact on mining operations; this calls for a holistic planning approach for mining operations taking into account the impact of the emissions trading scheme. Since carbon trading is a new area of study, particularly within Australia, the quantitative effect of the CPRS on the mining industry is uncertain and current mine planning practices do not directly consider emissions. This paper presents results of the study into the impact of the CPRS on a hypothetical large scale open pit operation, using a spreadsheet model based on linear programming and simulation. By varying the production rates, life of mine (LOM), carbon price and ore grades among other variables several scenarios were simulated to determine the impact of emissions trading scheme on the net present value of the project. This study found that the adoption of the proposed Carbon Pollution Reduction Scheme could impact mining operations in Australia by a three per cent to six per cent reduction in net present value, for carbon credit costs of $25/t to $50/t respectively. While the six per cent reduction in net present value for a mining operation is significant, rising fuel prices have had a similar effect in recent years. The most energy-intensive processes are the milling circuit and the flotation concentrator circuit. These processes are jointly responsible for up to 60 per cent of the total emissions, depending on the production rate and the level of offshore processing conducted. Clearly, the introduction of the CPRS makes it is imperative for mining companies to assess the impact of carbon emissions on a mining project during mine planning.

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

The Metallurgical Development of an Enargite-Bearing Deposit

Sep 13, 2010

By D Cumming-Potvin, S W. Jacobsz and E Kearsley, J Wesseloo

This paper describes a physical modelling program that recreated block cave propagation in a geotechnical centrifuge. A brief description of the design of the test along with the sample material and monitoring equipment is given. The samples tested showed caving behaviour and fragmentation distributions that one would expect from caving mines, with one cave deviating due to pre-existing major discontinuities in the sample. A series of fractures formed ahead of and parallel to the cave, implying that an extensional failure mechanism may play a larger role in cave development than previously thought. The results of acoustic emission monitoring of the tests show a seismogenic zone advancing ahead of the cave; however, the quantity and quality of the data is too limited to draw any further conclusions.CITATION:Cumming-Potvin, D, Wesseloo, J, Jacobsz, S W and Kearsley, E, 2016. Results from physical models of block caving, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 329–340 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

The West Coast region of the South Island is situated astride the Pacific û Australian plate boundary zone. The most significant component of this zone is the Alpine Fault. A variety of reconstructions of the pre-Alpine Fault plate tectonic configuration of the New Zealand continental area have been attempted over the past 25 years or so. Most of these have not been closely constrained by a regional compilation of field data related to the age and horizontal displacement history of the Alpine Fault. A model in which the Alpine Fault was initiated no earlier than the interval 18 - 16.5 Ma (B.P.) is proposed, a significantly younger age of inception than has been widely accepted as the onset of dextral displacement along the plate boundary through the South Island. A subsequent history of displacement is presented consistent with the West Coast basin stratigraphy. The alluvial gold content of some parts of the Miocene to Pleistocene conglomerate sequences is also discussed.

Jan 1, 1996

By G D. Richmond, J C. Chomley

Copper has been mined intermittently at Gunpowder, north of Mount Isa, since 1927. Most ventures have had some initial success but fluctuating copper prices, the small-scale of the operations and the remoteness of the site led to closures or sale. Processing routes have included direct sale of high grade ore, flotation of oxide and sulphide concentrate, and copper cement production from mine solutions. Copper cathode has been produced by heap and in-place leaching coupled with solvent extraction and electrowinning (SX/EW). Aberfoyle Limited recently purchased the Gunpowder operation and is expanding operations. An innovative high recovery tank leaching process, including a low temperature, low pressure autoclave, has been adopted. Copper cathode will be produced from an expanded solvent extraction/electrowinning plant at approximately 45 000 tonnes per year. The combination of expanded throughput and high metal recoveries will make Gunpowder a cost competitive producer.

Jan 1, 1998