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The major coalfields of Australia are almost unique in the occurrence in some areas of CO partly or almost completely replacing CH4,t1e normal seam gas from metamorphism of coal due to time and depth of burial. This CO2 situation has some benefits but mostly it introduces particular safety problems result- ing from the high density of CO2 relative to air, magnifying problems of gas dilution in ventilation, and the greater affinity which coal has for CO2 than for CH4 increasing proneness to gas-dynamic phenomena. The occurrence of most CO2 seam gas can be directly related to igneous intrusion and to its associated pneumatolytic injections. Whilst intrusions locally increase the rank of coal by their contact metamorphic effect, normal coal metamorphism due to time and depth of burial continues after intrusion and injection together with the ongoing metamorph- ic production of CH . This new CH slowly displaces any CO to leave some present-day intruded coals with seam gas with reduced CO2 or even without any significant CO2 associat- ions. The seam gas maps of the Bowen and Sydney Basins and more detailed maps of specific areas exemplify these situations. Mining progress, plus more searching studies of igneous-coal relationships provide improved understanding of the factors involved.

Jan 1, 1986

By K Barbosa, G Wilkie, F Reyes, V Jokovic, C Evans

The idea behind Grade Engineering is to exploit the natural heterogeneity of an orebody (spatial, temporal) in order to divert low-value waste out of the mining value chain. Essentially, this involves rejecting material at relatively coarse particle sizes (10 mm to 200 mm). However, lack of knowledge about the inherent particle grade distributions in these coarse particle size ranges limits the opportunities for optimisation. Particle grade distributions are essential for quantifying and modelling gangue liberation and yield curves. These curves can then be used to predict the mass and value flows that will go towards the accept and the reject streams. Particle grade distribution information for particles coarser than 10 mm can be collected based on chemical assays of sufficient number of individual particles. However, for smaller particles (1 mm to 9 mm), a significantly larger number of particles is required for assays. Moreover, in some cases, the mass of individual particles is smaller than the minimum mass required for chemical assaying. Also, other quantification techniques such as automated mineralogy, eg Mineral Liberation Analysis (MLA), require extended measurement times to analyse statistically representative numbers of particles at these size ranges. This work investigates the use of 3D X-ray microtomography to fill this quantification gap at these size ranges (1 mm to 9 mm). In-house image processing algorithms are used to estimate the mineral/metal content in each particle. Particle grade distributions, as well as density distributions, are thus produced without a minimum mass requirement and with each scan providing information about tens to hundreds of particles at a time. Mineralogical data from MLA analysis, of finer size ranges, is used to inform X-ray microtomography, so a simpler 3D mineral map can be obtained using the image intensity. Chemical assay information of the scanned samples is used to validate and correct the mineral phase segmentation.

Aug 24, 2022

By B McFadyen, Y Potvin, K Woodward

The Australian Centre for Geomechanics (ACG) held two workshops in 2019—one in Australia and one in Canada—to discuss processes and methods currently used in the mining industry for stope design and reconciliation. In practice, this work strives to optimise stope performance and aims to maximise ore recovery (minimise underbreak), while minimising dilution (overbreak). One of the key findings from the workshops was that current stope design practices, almost exclusively, rely on some versions of the empirical Stability Graph methods developed in 1980s. Although robust and useful at the feasibility study stage, there are a number of inherent shortcomings with this approach. The Stability Graph’s limitations first lie in that it cannot assess underbreak, which is a very important measure of performance. Furthermore, the method doesn’t consider a number of factors which often have a critical influence on stope stability, for example, drilling and blasting or the presence of faults. Given the current industry standard practice, there is a great opportunity to reinvent the stope design process to optimise performance. A finding of the workshops was that every mine quantifies stope performance in terms of volume reconciliation with a focus on dilution and ore losses, and reconciling metal tonnes recovered from the mill. Many mines further investigate stope performance by looking at individual stope faces and the causes for the deviations between the planned stope shape and the measured cavity. Recent research at the ACG has shown that investigating overbreak and underbreak at a higher resolution is a powerful way to identify the root causes of overbreak and underbreak. Finer scale assessment is achieved using an octree analyses, which effectively divides the relevant stope volume into cubes on the scale of a metre and produces many tens of thousands of data points. The octree data structure and subsequent analysis underpins a data-driven stope design methodology. The ACG is currently developing a design approach based on multivariate modelling methods that can account for the many variables that influence stope performance and forecast stope overbreak and underbreak results. Back-analysing stopes based on octree reconciliation results provides a rich database for training the model. Once the model can achieve reliable forecasting of overbreak and underbreak, an interactive drill-and-blast design will allow for the assessment of different firing strategies to optimise stope performance.

Mar 15, 2021

By R D ROSENTHAL

BHP Iron Ore Ltd's Mt Whaleback is the largest single open-pit iron ore mine in the Pilbara region of Northwestern Western Australia. A division of BHP Minerals, one of three core businesses of Broken Hill Proprietary Company Ltd (BHP), BHP Iron Ore - Newman is a joint venture with minor participants C Itoh Minerals and Mitsui. Mine planning for Mt Whaleback generates detailed sequence plans for a long term forecast incorporating equipment requirements, marketing forecasts, and pit development strategy. Utilisation of several computer packages, both commercially available and site modified, are necessary to achieve such a demanding task.

Jan 1, 1992

By Williams M

Sheet flotation is a new two dimensional column flotation cell that produces continuous spectrum of products. Analogous to a shaking table in its performance and analysis, sheet flotation is a sheet of bubbles rising through packing contained between two walls. Feed enters the sheet at the lower left and the product exit along the top and right edges. Iligh grade materials exit at the top left, middlings exit at the top right comer and low grade waste materials exit at the bottom right. As in the case of a shaking table, two motions are required: up and right. Bubbles furnish the upwards movement for hydrophobic particles, slanted packing the rightward movement for hydrophilic particles. The sheet flotation cells is analysed as a 40 x 40 array of simple cells. In practice, 1000 x 1000 arrays of simple cells may be expected. With larger arrays, excellent separations may be expected. Because there is no recycle, there is no build-up of middlings in

Jan 1, 1993

By S Hughes

The smelting of concentrates and secondary materials has been subject to increasing challenges in recent years due to declining grades of feed materials, increasing impurity levels and ever more stringent environmental regulations. In addition there has been a growing focus on maximising the efficiency of energy usage and recovery of values. New opportunities have been created with rising metals prices and improved systems for the collection of secondary materials, giving rise to a need for more flexible process solutions.This paper focuses on a number of specific cases where a process solution has been developed using the Outotec« Ausmelt Process to meet particular feed material challenges and overcome limitations inherent when employing traditional pyrometallurgical processes.The first case involves the development and commercial implementation of a smelting process to recover values from zinc smelting residues typically deposited into dams as a waste product. The second case describes the application of the Ausmelt process for the smelting and converting of secondary copper feed materials, including e-waste. These materials contain a wide range of metals and plastics and need to be processed appropriately to maximise the recovery of values whilst avoiding environmental problems. The third case study covers the smelting of nickel concentrates containing elevated magnesia levels as well as nickel bearing catalysts with high alumina content, neither of which can be readily processed when employing traditional pyrometallurgical technologies. CITATION:Hughes, S, 2013. Pyrometallurgical process solutions for complex raw materials, in Proceedings MetPlant 2013 , pp 519-530 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By Marois R, Hauff P, Kowalyczk P, Lipton G, Bedell R, Neville R, Edmundo G, Ehling M, Kern R

The Canada Centre for Remote Sensing (CCRS) has developed an airborne sensor, the SWIR Full Spectrum Imager (SFSI) which detects in the Short Wave Infrared range of the solar spectrum from 1220 to 2420nm. In June of 1995, a demonstration flight was undertaken in the state of Nevada with the support of the companies listed above. The focus of the flight was to collect image data over well known mineral deposits with the objective of evaluating the applicability of this sensor to alteration mineral mapping. Some of the Nevada sites chosen include Cuprite and Goldfield, volcanic hosted acid sulfate systems; Yerington, a structurally complex porphyry copper deposit; and Virginia City, a Quartz- Sericite-Pyrite vein system with advanced argillic pods. Ground spectral data was collected with the PIMA-II spectrometer. Solar reflectance calibration was done by Desert Research Institute personnel at Virginia City and Cuprite. This paper will discuss the configuration of the sensor and present image and ground data for Goldfield and Virginia City.

Jan 1, 1995

By Katsuyama K, Nag DK

Three aspects of rock mechanics, namely, in-situ stress estimation by acoustic emission (AE) method, strength of rock mass and role of chemicals to reduce the strength are covered. It is possible to detect the previously applied maximum stress by stressing a rock specimen to the point where there is a substantial increase in AE activity. This is known as Kaiser effect. From the AE signatures in the second and subsequent loadings, AE take-off point was identified more easily than in the first loading. In determining the compressive strength of rock mass, two factors have to be considered, namely, the size effect on the compressive strength of intact rock and the effect of discontinuities on the compressive strength of rock mass. Although a modified Bieniawski criterion gives best agreement with the triaxial test data, modifications have been suggested to Hoek-Brown criterion due to its popularity. It is possible to reduce the tensile strength of sandstone by saturating it with weak chemical solutions made with dodecyltrimethyl ammonium bromide, polyethylene oxide and aluminium chloride by up to 30%. In the case of compressive strength, there is no appreciable effect. The possible explanation is that the chemical solutions produce an effect on the strength of sandstone only when the failure mechanism is dominated by tensile mode.

Jan 1, 1998

By Purvis A. H, Greenwood-Smith R, Sowerby B. D

A nuclear technique for the determination of copper and nickel in bulk samples and drill core has been developed at Lucas Heights andfield-tested at Mount Isa. The technique, which is highly specific to the element being measured, utilises the gamma-ray resonance scallering process.A bulk mineral analyser was installed in mid-1976 for the routine assay of copper in bulk samples and drill cores, and remained in operation until late 1981. The operation of the analyser over this five-year period is reviewed with particular emphasis on reliability, accuracy and principal usage.The main application of this analyser was in stope planning and design whereby several thousand drill-core and Wall-chip samples were analysed. It was also used as an aid to underground grade control of stopes where ore dilution by supporting barren backfill was a problem.

Jan 1, 1984

By G E. Holt

Active EM subsurface imaging is a proprietary technique developed by Marschall Acoustics Instruments Pty Limited (MAI) to image subsurface features at depths useful for the mining industry. Similar in field operations to high resolution seismic surveying, the Active EM technique employs electromagnetic energy rather than elastic wave energy. Received backscattered energy in the Active EM technique is thus due to differences and contrasts in electromagnetic permeability and permittivity in the subsurface, analogous to LamTÆs constants in elastic wave imaging. Carrying the analogy to seismic imaging even further, the Active EM method employs high power transmissions of very wide-band coded signals of a controlled polarisation. Likewise, the array pattern and polarisation of the receiving transducers is also tightly controlled. Thus, in a certain mathematical sense, Active EM is the electromagnetic equivalent of high power high resolution vibroseis seismic surveying. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By B Petrie, D J. MacKenzie

The Macraes mine is producing 175 000 ounces Au/year from a mesothermal deposit with total resource of at least five million ounces. The deposit is hosted in greenschist facies Otago Schist, a widespread Mesozoic metasedimentary sequence that forms the basement of the South Island of New Zealand. Mineralisation was controlled by a late metamorphic shear zone which had both brittle and ductile structures accompanying mineralisation. The shear zone dips shallowly (about 15¦), subparallel to the shallow-dipping regional foliation, and mineralization occurred during southwesterly-directed thrust motion. Mineralisation occurred under greenschist facies conditions (about 350¦C) during uplift of the Otago Schist in the late Jurassic. No syn- or late-metamorphic igneous bodies occur within the schist belt. The hosting shear zone is up to 120 m thick, and is traceable for more than 30 km along strike. The shear zone is truncated by an underlying low angle normal fault that juxtaposes mineralised lower greenschist facies rocks on to unmineralised upper greenschist facies rocks.

Jan 1, 2004

By G Brewster

The Eagle on the Hill tunnels form part of an upgrade of Mt Barker Road, 15 km to the southeast of Adelaide. The upgrade significantly improves safety and reduces delays on this major road, which winds steeply through mountainous terrain. The twin tunnels each spanning 15 metres run in parallel for a length of 480 metres. The tunnels are excavated in slightly weathered high strength slates and very high strength quartzites of the Saddleworth Formation on the western margin of the Mount Lofty Ranges. Steeply dipping slate cleavages and the high fracture ratio result in many slope stability problems in the project area. The level of geotechnical investigation undertaken prior to the calling of tenders for the project was extensive. This included the excavation of a pilot tunnel along one of the tunnel alignments, which allowed accurate mapping and rating of the rock, resulting in an increased level of confidence during the tender process. One of the features of the winning alternative tender design was the use of canopy tubes, flexible steel ribs and shotcrete to replace up to 40 metres of deep portal cuts in unstable rock with driven tunnels. Slope stability issues were overcome with the use of rock dowels and shotcrete. The support concept allowed the safe driving of the tunnel portals with as little as two metres of overburden. The design incorporated lining drainage and criteria for fireproofing based on European experience to ensure the ability of the tunnels to remain stable in the case of a severe fire incident. The support design allowed for maximum flexibility with a range of support types able to deal with the varying ground conditions. Design development and support refinement continued throughout the tunnel construction phase with close liaison between the designer and the constructor. Monitoring and review of feedback from the construction site by the Sydney based design team was easily achieved by means of electronic transfer of photographic and survey information, telephone and fax communication and regular site visits. The contractor for this project is Macmahon Concrete Constructions Joint Venture (MCCJV) and the designer is Connell Wagner. Excavation commenced in January 1998 with tunnel breakthrough having been achieved in early-August 1998 and mid-September 1998 respectively. Concrete lining construction is scheduled for completion in April 1999.

Jan 1, 1999

By A D. Paktunc

The surface reactivity of underwater deposited, high-sulfide copper mine tailings was evaluated under fresh and saline water cover conditions by measuring the surface and pore water quality as a function of time. The experiments were conducted in aquarium type lysimeters having a shallow, well-aerated water cover up to approximately 0.25 m over the tailings. Natural lake water was used for the fresh water cover and seawater for the saline water cover scenarios. The tailings showed significant surface reactivity and oxidation under both fresh and saline water cover conditions. The surface water quickly became moderately to highly acidic, and surface oxidation of the tailings resulted in increased dissolution and release of sulfates, iron (total), calcium, magnesium, aluminium, manganese, copper, nickel, zinc, lead, cobalt and silicon to the water covers. A moderate to slightly increased loss of total sulfides, including pyrite, chalcopyrite and sphalerite, occurred in the tailings surface layer to a very shallow depth. In comparison to the fresh water cover, the complete acidification of the saline water cover was delayed by approximately 30 - 40 days because of its additional available alkalinity. Whereas the rate of surface water acidification and release of aluminium and silicon were moderately reduced under saline water cover conditions in comparison to those for the fresh water cover, the release of calcium, magnesium, iron (total), copper, nickel, lead, zinc, sodium and potassium were enhanced. The mass transfer fluxes for dissolved copper, nickel lead, zinc and iron (total) from the tailings substrate to the surface water cover following surface water acidification were higher by 50 per cent or more in the saline water cover than those in the fresh water cover. This release was also reflected in moderate loss of pyrite, chalcopyrite and sphalerite in the very shallow upper surface layer of the tailings at the tailings-water interface, although the loss of pyrite in the surface layer was less pronounced. In both cases, the dissolution of aluminosilicate minerals moderated, to a certain extent, pH and acidity in the water cover.

Jan 1, 2003

By J Brisebois

The Wisemans Creek derelict mine site is located in native forest approximately 150 km west of Sydney. Mean annual rainfall at Bathurst, 20 km to the north, is 634 mm and reasonably distributed throughout the year, with slightly more rain falling in the summer months. Evaporation is 1350 mm per annum and considerably exceeds rainfall in all but the winter months (May to August). This results in a water deficit for much of the year. Groundwater is relatively deep, as it has not been intercepted in the shallow open cut workings. Investigation of the groundwater regime was beyond the scope of the current study. Mining has taken place on the site for almost 100 years, during which copper, talc and gold have been sequentially extracted from surface and shallow underground workings. The site is now characterised by the presence of small open pits, unprotected shafts and adits, mullock heaps and an unconfined tailing deposit from a small cyanidation plant. From a distance, the mine area is visible because of two distinct steep bare slopes below the relatively small mine workings and mullock heaps. The mining area was characterised in terms of its environmental, safety and heritage issues. Mullock from the early copper mining was found to be acid forming and leachate from this, combined with clearing of timber, has most likely resulted in death of vegetation below the heaps. The mullock also contains elevated concentrations of heavy metals. The gold tailing is apparently benign and not acid forming, although there are indications of oxidation and acid formation in the derelict gold open cut. Oxidation of the acid forming mullock still appears to be taking place even after being exposed to the atmosphere for at least 50 years, resulting in continued contamination of the slopes below the heaps with heavy metals. The concentrations of metals decreases with distance below the mullock heaps and also is confined to the ground surface the further away from the mullock, providing further evidence to support the theory that the mullock is the source of contamination. Despite this continuing contamination, its spread beyond the immediate mining area appears to have been limited because of the relatively dry climate, with only intermittent rainfall and stream flows. Irregular storm flows in the nearby creek could also have washed any contaminated soil some distance from the site and beyond the area investigated in this study. Remediation of the site and restoration of vegetation on the bare slopes will therefore depend on elimination of the source of acid and metals. Options for remediation, focussing on minimising cost by retaining the materials on or close to the site, are identified. The volume of the open cuts would appear to be close to that required for burial of the acid-forming mullock, thereby removing the source of surface contamination while keeping it above the groundwater table. However, implementation of this remediation plan will depend on the availability of funds to undertake the work through the New South Wales GovernmentÆs Derelict Mines Program.

Jan 1, 2003

Intensive exploration for iron ore in the banded iron-formations (BIF) of the Pilbara region of Western Australia began in the early sixties and almost immediately established the Hamersley area as a major iron province. The early genetic models for the BIF-hosted ores were based mainly on macroscopic examinations of ores from the "hardcap" zone, and generally accepted a direct relationship with weathering effects on a Mesozoic to Tertiary land surface. Brandt (1964) was the first to suggest a difference in age between the high-grade hematite ores and the more common hematite-goethite types. He initially accepted a supergene origin for both, but later opted for a hydrothermal origin for the hematite ores. Apart from MacLeod (1966), the published views of the next decade reflect a largely parochial interpretation of individual ore bodies, centred mainly on supergene models but with some support for hydrothermal concepts. Except for Ayres (1971), none of the models were backed by detailed mineragraphic data. In 1976, an AMIRA-sponsored CSIRO group began a Province-wide investigation of the wide variety of ore types and BIF, with emphasis on geochemical and textural studies. The resulting conceptual model for a world-wide unified supergene and supergene-metamorphic hypothesis is generally accepted in the Hamersleys.

Jan 1, 1986

By Billington WG

A structural study of northwest Fergusson Island, part of the D'Entrecasteaux Group, was undertaken using colour and monochrome aerial photography and Landsat imagery. The resulting interpretation shows an upstanding, in part, dome-like metamorphic core complex, which is bound on three sides by an en echelon series of low-angle, thrust faults. Faceted gneissic layers occur throughout the complex. These facets are triangular in plan view and range in size from a few tens of metres, to massive composite zones which traverse the entire uplifted zone, The lower surface of each of the facets are, in fact, low-angle decollements which, during uplift, slid one upon the other to accommodate the vertical and extensional movements. As a consequence, deep structural valleys developed which widen towards the zone of maximum uplift. In many places, recognisable topographic features are replicated on both sides of these valleys, and under the stereoscope can be visually reconstructed to their original pre break-up positions. The southern margin of the core complex is less dome-like and falls away, via a series of deeply-entrenched structural valleys, towards a volcano-studded lowland. The lowland appears to belong to a rift or arm, stemming from the more southerly located Goodenough Bay Infrabasin.

Jan 1, 1987

By S Youds

The backfilling operation at Olympic Dam mine supports a 9.8 Mtpa underground Long Hole Open Stoping (LHOS) operation. It involves a combination of Cemented Aggregate Fill (CAF), surface rockfill and underground rockfill. The fill material is introduced from the surface via boreholes into the top of the stopes. Due to the deleterious effects of the dust and the thickness of the atmosphere in the stope it is not possible to view the filling process either at optical or infrared (IR) wavelengths. The need for a means to measure the filling process is driven by the placement of both rock and CAF fill in the stopes. The large volumes and high relative cost of CAF makes the minimisation of CAF fill a business priority. Incorrect filling can lead to the sterilisation of ore reserve. The use of millimeter wave radar to view through the haze to give real-time data on the relative positions of the different fill masses is being developed as an in-stope fill monitoring device. This paper reviews the salient points of the technology and its potential use in the backfilling operation at Olympic Dam. The broader potential of this technology for use in the mining industry by æseeingÆ through water and dust laden environments such as that found in stopes and ore passes is also discussed.

Jan 1, 2002

By Kyle J. H, Misra V. N

The most recent development in gold processing is the increasing use of heap leaching for the extraction of gold from low grade ore, and old tailings dumps. The reason for this trend is mainly to do with economics. The advantage of heap leaching is the considerable saving in both capital and operating costs. However, not all ores are amenable to heap leaching. It is only applicable to well oxidized ores that have suitable permeability char- acteristics, and the gold recovery is poorer than by conventional process. In this study, an attempt has ben made to ascertain the heap leaching characteristics of Western Australian gold ores on the bench scale using multiple, appropriately sized leach columns. The influence of particle size, flow rate, column depth and leaching time on the rate of gold extraction was determined. The percolation rate of cyanide leaching solution was deter- mined with and without gypsum additions. Efforts were also made to minimise particle segregation, fines migration and solution channelling during leaching, so as to improve solution percolation, gold extraction rate and recovery.

Jan 1, 1991

By K Thompson

The Diavik Diamond Mine is a world-class operation located in an extreme environment 220 km south of the Arctic Circle in CanadaÆs Northwest Territories. The mine has a number of distinctive characteristics û such as limited winter access via an ice road, mine infrastructure being located on an island, with mining taking place behind dykes holding back a lake, temperatures at the mine that get down to -45¦C in winter, and the presence of bears, wolves, foxes and wolverines! One thing that Diavik does have in common with other mines around the world is the need for reconciliation. In late 2005 Diavik implemented SnowdenÆs Reconcilor software system to facilitate the process of reconciling geological models, mine plans, production data and plant results. This paper provides a case study of the reconciliation system implementation. It outlines the migration of Diavik away from a comprehensive and effective spreadsheet-based reconciliation process to a commercial grade, automated and web-based information management system. This paper documents the reasons for moving away from the spreadsheet system, the key parameters used for reconciliation, and the benefits gained by closing the loop between reconciliation and ongoing process improvement.

Jan 1, 2006

By Mules GJ

Geotechnical investigations have played a key role in influencing decisions for development of the Porgera Gold Project in the highlands of Papua New Guinea. Porgera is located 130 km west-northwest of Mt. Hagen in steep mountainous terrain with high rainfall. Much of the site is underlain by weak mudstone of the Chim Formation and creeping colluvial soils. Landsliding is common on the steeper slopes and in the valley floors. Structures have had to be sited to avoid areas susceptible to these movements. Early stage feasibility investigations included studies of tailings dam and waste rock dump sites, processing plant sites and hydroelectriic schemes. Further studies, leading into the design stage included the Enga Highway upgrading, water supply and power supply schemes. As construction for the project proceeds geotechnical input remains at a high level, with emphasis now on maintaining viable stable sites and refining data on which designs were based.

Jan 1, 1990