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By A Maldonado, A Robert, K G. Mercer

The Hamersley Group in the Pilbara, Western Australia, consist of interlayered banded iron formation (BIF) and shale host rock formations within which a large number of open pit iron ore mines have been established. The slope stability of most of the mining excavations developed within these formations is controlled by the relatively low shear strength of the shale groups and shale bands, which are the weakest rock types. Shale formations range from fresh to highly weathered and are generally highly fissile when fresh, and clayey when weathered. An accurate understanding of the shear strength of these materials across the entire weathering continuum is therefore a key importance for assessing the slope stability of these mines.Historically defect laboratory testing results for the Pilbara mines have been analysed mechanically using direct shear testing (DST) to measure a number of geotechnical characteristics of the rock bedding and defects. This paper sets out the current practice in the industry in terms of the laboratory testing and presents a possible application of hyperspectral data to empirically correlate the shear strength of shale bedding with the relative mineralogy abundance on the bedding surface. This was achieved by creating both hyperspectral and geotechnical data sets for the same samples.In the study the shale samples were separated into three distinct assemblages: iron oxide + kaolinite, iron oxide + white mica + kaolinite, white mica + kaolinite, which had 40, nine and two samples respectively. Analysing these assemblages alongside DST data showed that samples with white mica had reduced non-variable shear strength, whereas samples with iron oxide + kaolinite had an overall higher shear strength but with a greater variance. It is inferred that the reduced shear strength in the white mica samples is due to the sheet (or plate) like structure of the mineral, giving it a weak stress plane. Confidence in the trends observed can be reinforced by expanding the data set in future works. The investigation also includes a discussion on weathering grade and addresses the question as to whether mineralogy abundances influence these characteristics in Hamersley shales.CITATION:Maldonado, A, Mercer, K G and Robert, A, 2017. The relationship between mineralogy and shear strength of Pilbara Hamersley Group shales across the weathering spectrum, in Proceedings Iron Ore 2017, pp 423–430 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By D Craw

TheSouthern Alps in the South Island of New Zealand are currently rising rapidly as a consequence of continental collision along the Pacific-Australian plate boundary. Rapid uplift has resulted in a major thermal anomaly in the shallow crust beneath the alps. Alpine topography and associated intense precipitation, coupled with the thermal anomaly are responsible for vigorous combined topographic/convective circulation of water through the shallow crust.   Uplift is greatest in a wedge-shaped region between the Alpine Fault and an associated second-order backthrust system, the Main Divide Fault Zone, approximately 20 km to the east. The Main Divide Fault Zone is segmented into NNE and NE striking faults, which are regionally sub-parallel to the Alpine Fault, but dip northwest in the opposite direction. Reverse oblique-slip on the Main Divide Fault is in an easterly direction, with a greater component of strike-slip movement on the NE trending faults. Elevated topography in the Mt Cook region is related to thrusting of a relatively homoclinal sequence of semi-schistose rocks on top of lower-grade greywacke, which controls the position of the Main Divide. Tectonically induced fluid flow resulted in only minor alteration and hydrothermal mineralisation of fault-rocks in Alpine and Main Divide Faults, and localised deposition of quartz and/or carbonate in the immediate hangingwall.   The wedge between the Alpine and Main Divide Faults is segmented by third-order structures north of the Mount Cook region. A series of right-lateral (-085/700S) and left-lateral (-150/600SW) faults, which are synthetic and antithetic to the Alpine Fault, respectively, developed as a conjugate set during uplift. Fluid-flow in the Southern Alps is controlled by these third-order fault/fracture systems. Cu-Au mineralisation, hydrothermal veins, and surface hot spring activity are localised by third-order fault/fractures and appears to be enhanced where conjugates intersect.

Jan 1, 1995

By C J. N Wilson

The central Taupo Volcanic Zone is a region of intense Quaternary silicic volcanism accompanying rapid crustal extension. Modem central TVZ is the most frequently active and productive silicic volcanic system on Earth, erupting rhyolite at c.0.28 m3 s-1. The rhyolites show no major compositional changes with time, but the total extent of magma chamber zonation has changed with the advent of rifting and crustal extension at c.0.7 Ma. At least 34 caldera-forming ignimbrite eruptions have formed a complex sequence of relatively short-lived, nested and/or overlapping volcanic centres in central TVZ. Taupo contrasts with other large silicic magmatic systems in the exceptionally high frequency, but small size, of caldera forming eruptions. This contrast reflects the thin, rifted nature of the TVZ crust that precludes the development of long term magmatic cycles at Taupo. Within central TVZ, non-rhyolitic compositions have been erupted apparently irregularly in time and space; in particular there is no evidence for a geographic separation of basalts from andesites. TVZ is a rifted arc, but its segmented nature, high thermal flux and voluminous rhyolitic volcanism make it unique on Earth.

Jan 1, 1995

The paper discusses the special mixing requirements for Metallurgical Plant Design and outlines the problems associated with the agitation in Mineral Processing Industry today. It also covers new applications such as state of the art large leach tanks and backfill for deep mining.

Jan 1, 2004

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

By M Olsen, L van den Berg

Bowen Basin coalmines suffer from hot and humid ambient conditions during the summer period. The ambient conditions combined with high VRTs, increasing depth of working and significant equipment heat loads results in heat issues underground. Coalmines operate under heat stress management plans as required by legislation with associated trigger action response plans (TARPs). Some mines also employ refrigeration as part of their heat management strategy.A recent case study was conducted on a mine producing about 4.5 Mt/a from their longwall and experiences summer surface ambient temperatures of about 23.5ºCwb. The expected virgin rock temperature is 46ºC at 300 m depth. The mine currently introduces a modest amount of surface cooling at the portal using ‘off-the-shelf’ air conditioning units. This system does not effectively manage face temperature primarily due to positional inefficiency.Underground conditions remain hot in summer and work is typically undertaken in accordance with the Heat TARP. This has a direct impact on the productivity of crews, worker comfort and also negatively impacts the workforce morale. The mine commissioned a study to determine a refrigeration strategy aimed at maintaining underground conditions below TARP levels 90 per cent of the time.The ventilation network model was calibrated against actual temperature data to simulate the heat loads including longwall, conveyor system, strata and auxiliary diesel fleet. This model was then used to determine the cooling requirements for bulk surface cooling, bulk underground cooling, surface district cooling and underground district cooling strategies.These estimates were used to undertake a total owning cost trade-off for the different strategies. The study concluded that a chilled air shaft has the lowest technical risk but the highest total owning cost due to shaft development needs. Introducing chilled water to an underground cooler via boreholes offered the lowest total owning cost and was therefore recommended.CITATION:van den Berg, L and Olsen, M, 2017. Heat load assessment and mine cooling strategies for a longwall coalmine, in Proceedings Australian Mine Vent Conference 2017, pp 231–236 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

By using knowledge-based technology to create a Virtual Mining Enterprise and integrating it with existing technical and financial computer systems, a gold mining company has been able to reduce the time taken to produce a mine plan from 14 weeks to less than one week. Typically, the mine planning process requires circulating and managing large amounts of information. Even with the use of computers in todayÆs business, this is often still a manual process involving file transfers and individualised spreadsheets. Mine planning also involves understanding and managing large quantities of complex and interrelated variables. Added to this is the ever changing dynamics and constraints associated with the business of mining. These issues not only hamper the planning process but also question the validity and usefulness of the mine plans being generated. By integrating the information and knowledge of the numerous departments involved in mine planning into one core Knowledge Base - so called æone version of the truthÆ, - mining companies are able to overcome these pitfalls experienced in traditional planning methods. Once set up, the Knowledge Base creates and runs a virtual mining enterprise with which to visualise and test various scenarios of mining, business and logistical activities. The final output is an optimised enterprise-wide plan with clear and detailed instructions for each of the divisions of the company.

Jan 1, 2000

Large mining operations need equipment that consistently performs as expected. The most effective way of ensuring this is to have a defined life cycle with an optimised maintenance strategy. The determination of this life cycle is an economic decision, influenced by the construction and utilisation of the equipment. An effective life cycle costing (LCC) tool must be able to process the many variable factors involved.Many factors influence the costs that are associated with a machine over its life. The most variable of these are the costs of maintaining the equipment. Maintenance costs are dependant not only on the utilisation of the machine, but also on the strategy that has been developed to support the machine through its life. A combination of supplier support, component changes, regular servicing and unscheduled maintenance needs to be modelled, based on a variety of drivers. Traditionally spreadsheets have been used to model these factors, but the increasing complexity of the situation can make spreadsheets unwieldy and difficult to manage. A database solution that breaks each activity into its constituent components, links them to an associated mine plan driver and then aggregates the result is the ideal tool to provide a time based cost profile. The evaluation of a number of scenarios, representing different maintenance strategies/life cycles can be rapidly undertaken. Auditability through inbuilt tools is required to provide easy tracing of data. Use of the host company's account structure allows for reporting against the standard chart of accounts.

Dec 6, 2010

By R A. Binns, S Murao

The PACMANUS and Jade deposits are two active hydrothermal fields that are forming massive sulphide deposits at the Pacific rim margin. Both are associated with felsic submarine volcanic rocks and both occur in back-arc settings. However, PACMANUS is associated with almost sediment-free dacites and lies on the crest of a volcanic ridge, whereas Jade occurs in a heavily-sedimented tectonic depression associated with a basement of pumiceous rhyolite. The PACMANUS deposit is richer in Cu and Au, and Jade in Pb. Zinc, Ag, As and Sb contents are similar. Sulfide textures at PACMANUS suggest formation of Cu and Zn sulfides by simultaneous double-diffusion involving inwards-moving seawater mixing with outwards-moving hydrothermal fluid. By contrast, at Jade there is a more complex history of formation where initial growth of barite on the sediment surface, probably associated with microbial activity, formed an impervious cap which trapped higher temperature hydrothermal solutions.  

Jan 1, 1995

By K A. Campbell, K A. Rodgers

The Plumduff sinter occurs at Whenuaroa, near Puhipuhi, approximately 30 km north of Whangarei. It is one of three residual sinters in the southern portion of a mid- to late-Pliocene geothermal system. The deposit consists of many large sinter breccia boulders, including rudrocks (coarse breccias), scattered around the flanks and summit of the small conical hill of Plumduff. Three types of sinter breccia occur: (i) rudrocks consisting of large, angular to sub-angular clasts of layered sinter up to 0.8 m across, as well as smaller clasts of sinter (20 - 100 mm dia), and fragments of stromatolitic structures; all clasts are supported in a matrix of microcrystalline, transparent to translucent to milky quartz; (ii) fragments of layered angular to irregularly mottled sinter of white to grey or bluish hue supported in a translucent to opaque silica matrix; (iii) smaller, matrix-supported breccias with clasts both partially surrounded and/or penetrated, by a clay-like weathering rind, and sinter conglomerates with rounded to oblate clasts. Three principal types of fabrics constitute the bulk of the sinter: (i) stromatolites, including columnar, palisade and filamentous networks, showing progressive silicification, in fenestral, tufted to clotted fabrics; (ii) peloids and pisoids; (iii) plant-rich facies in which various silicified plant species occur in a silica matrix. All fabrics have counterparts in hot spring deposits in the Taupo Volcanic Zone formed at temperatures from 75¦C to 35¦C. Also present is steam-condensate-produced alteration: kaolinite and alunite as well as boulders of quartz lattice texture. Cinnabar only occurs in sinter on the north and south central slopes of the hillside. No quartz veins or geyserite were recognised.

Jan 1, 2001

Enterprise Optimisation is a methodology for increasing the value of mining and mineral processing operations through better long-term planning decisions. It involves a combination of ten mechanisms which deal with decisions at different stages of the value chain. A decision made at any point in the chain potentially affects the decision for all other points in the chain. The key, therefore, is to optimise them simultaneously. The Enterprise Optimisation approach can be shown to produce increases of five per cent to 35 per cent or more in net present value (NPV), even when several optimisation methods have already been applied. This paper steps through an example case study, illustrating the effect of each mechanism and how they can work together to develop greatly improved results. This example results in a series of counter-intuitive outcomes, which challenges conventional management practices and typical organisational objectives based on organisational silos.

Dec 6, 2010

By A D. Campbell, G R. Power

Many caving mines use numerical flow models to simulate mine production, forecast recovered ore grades and optimise the draw strategy. In sublevel caving (SLC) mines, the effects of blasting and fragmentation at an individual ring scale generally cannot be included in these models. Previous attempts to use results from marker recovery trials to calibrate numerical flow models have been limited due to difficulties in accounting for blasting effects at a ring scale. This paper outlines how an empirical criterion for blasting and fragmentation was used to attribute variable flow properties into a numerical flow model based on the blast design and modelled fragmentation. The flow model was then validated using data from a number of full scale marker recovery experiments. The result of this approach was a significant improvement in forecast accuracy when compared against the same modelled cave marker recovery without the inclusion of these blasting effects. Improvements in the flow model are currently being adopted within the mine scale model to further improve the accuracy of grade forecasting, optimise the draw strategy and increase net present value. The integrated modelling approach is also being used to simulate the effects of different drill and blast designs on cave recovery. It is suggested that, if implemented, the technique would lead to improved blast designs in other SLC mines, increase the value of marker trial data and reduce costs associated with large scale blast design trials.CITATION:Campbell, A D and Power, G R, 2017. Improving calibration of flow models against SLC marker trials by linking blasting effects to particle mobility, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 11–22 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

The Use of Automated Mineralogy to Interpret the Batch Flotation Performance of Merensky Reef Ore

Sep 13, 2010

By S F. Simmons

The Ohaaki Rhyolite and the Rautiwiri Breccia are two volcanic units occurring in the shallow and deep parts of the Broadlands-Ohaaki geothermal system. Alteration of these units by chloride waters results in distinct mineral assemblages that also have distinct whole rock compositions. The Ohaaki rhyolite is altered to an assemblage dominated by quartz, adularia, illite and pyrite as a consequence of silica, potassium and sulfur metasomatism. Locally, these rocks contain up to 0.5 ppm Au. The Rautiwiri Breccia by contrast is altered to an assemblage dominated by albite, adularia, quartz, illite, chlorite and pyrite in association with modest sodium metasomatism. Whole rock oxygen isotope compositions of altered rocks range between 3.3 and 7.5 ë, and are generally lower compared to their fresh rock equivalents having values of 9.5 to 10.6 ë; the result is broad pattern of lower values with increasing alteration intensity.

Jan 1, 2002

By J R. Leeming

Mining law has developed in Great Britain (GB) over centuries, mainly in response to lessons learned after disasters and other major incidents. This has led to a culture of preventing repeat accidents, rather than predicting and controlling unsafe acts or conditions.This paper explains how, initially in response to a government drive to reduce the burden on industry, the opportunity was taken to review and reform all 48 sets of GB mining-specific law into a single document. The philosophy adopted, the procedure followed and the significant changes that resulted are explained.CITATION:Leeming, J R, 2017. The complete renewal of Great Britain’s mining laws for the 21st century, in Proceedings Australian Mine Vent Conference 2017, pp 3–8 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

Thermodynamics of Non-Cyanide Gold Solvents The present status of the raw material base in the gold industry requires specific ways to recover gold and silver from ores. Most gold is closely associated with sulfides which require flotation followed by pressure or bacterial oxidation. The next stages of processing usually require using expensive operations for the preparation of leaching. A lot of researchers want to find a new alternative solvent for the extraction of precious metals from these products. According to the authors, one of the best ways is to use sulfur-based solvents (thiosulfate, sulfite, and their various mixtures). Thermodynamics of gold and silver thiosulfate dilution are calculated for conditions: the concentration of Au - 200 mg/L, oxygen - 3.2 mg/L, thiosulfate - 79 mg/L, OH- - 170 mg/L. the general result is the possibility of process remains under standard conditions. (erAu = = 0.035 V, ?G298 = - 29.18 kJ/g-atom ??). Silver with thiosulfate forms two strong complexes: [AgS203]- and [Ag(S203)2]3-. ?G0 = -1027 kJ/mol. The complex [AgS203]- is less stable: ?G0 = 486 kJ/mol. It should be noted that despite the high stability of gold complexes, the sodium thiosulfate may decompose to sulfite and elemental sulfur during the process, especially when heating. Gold is slightly soluble in the sodium sulfite solution, however it forms the strong complex [Au(SO3)2]3-. Depending on the concentration of free S2O32-ions, silver with sodium sulfite forms three complexes: [AgSO3]-, [Ag(SO3)2]3- and [Ag(SO3)3]5-. The dissolution speed of gold in sodium sulfite solution may be in the same range as it is during cyanidation. In this case, a practical application of sulfite process can be also used, especially for the products containing free elemental sulfur. In conclusion, sulfite-thiosulfate gold lixiviants can be used for concentrates after pressure oxidation of the cakes.

Sep 13, 2010

In November 1969, New Zealand Steel Ltd pioneered the commercial use of the SL/RN solid fuel direct reduction process to make sponge iron as a feed material for electric arc furnaces. Serious process problems with the use of green balls and coal injection were progressively overcome. The process was developed by New Zealand Steel along a radical route, of feeding the fine grained raw ironsand concentrate and coal directly to the kiln. Contemporaneously with this development of direct reduction, steelmaking process innovations were made that enabled the arc furnaces to operate successfully with the high volumes of acid slag. The further expansion of New Zealand Steel's primary steelmaking capacity to replace the currently imported hot and cold flat rolled products is under consideration. The requirement to produce about 600 000 tonnes of steel slabs will be an opportunity to further modify iron and steel making plant and processes to optimise the economics. The conceptual and preliminary engineering selection of options is described.

Jan 1, 1980

By N van Aarde, B A. Moore, S van der Merwe

Frequently materials handling operations are compromised by transfer chute problems ranging from high wear rates, blockages and ineffective loading of the downstream conveyor. This paper will present the design flow implemented to overcome problems in two case studies utilising discrete element modelling incorporating material characterisation.Material testing is relevant in achieving a valid discrete element method (DEM) simulation model and subsequently a valuable design tool for transfer chute assessment and design. It is well recognised that in the current growth and demand for mineral resources, leading to ever increasing conveyor capacities associated with export terminals and mineral processing facilities that transfer chutes are a key focus point. The successful performance of the transfer chute is also dependent on operating with a ærobust rangeÆ of material flowability and handling characteristics. This requirement is crucial in accommodating mineral ores from developing resources, which are often more friable and stickier than in past decades.This paper will include details of chute installations associated with iron ore and coking coal, from the DEM simulations through to the performance of the installed and commissioned plant.CITATION:Moore, B A, van der Merwe, S and van Aarde, N, 2013. Implementation of advanced transfer chute designs, in Proceedings Iron Ore 2013 , pp 445-450 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By A B. Christie, F P. Bierlein

Lode gold deposits of the Western and Eastern provinces, South Island, New Zealand , formed as a part of the Cordilleran-style tectonism during Tasman/Tahua and Rangitata orogenesis along the Paleozoic-middle Mesozoic southern Gondwanan margin. These deposits, hosted by lower grade greenschist facies sedimentary rock sequences of the Buller, Takaka, Torlesse, and Caples terranes, universally show geological features that are consistent with the orogenic gold deposit model, and genetic features are generally suggestive of a metamorphic origin, with the possible exception of a magmatic fluid source for the mineralisation at Sams Creek. However, ore fluid chemistry in Mesozoic deposits of the Eastern province, particularly the low concentration of non-aqueous volatiles and the very dilute nature of the fluids, is uncharacteristic of most orogenic gold deposits; this must be explained by either a unique fluid source or fluid type, which we believe unlikely, or an unrecognised significance of relatively rare gas-rich fluid inclusions in the deposits. Absolute age data for gold deposits in both provinces remain equivocal, thus hindering definition of the exact temporal relationship between ore formation and terrane accretion, regional metamorphism, and magmatic arc emplacement. Mercury and antimony occurrences in subgreenschist grade parts of the Haast Schist may target the upper levels of unrecognised orogenic gold deposits. If low-grade, high-tonnage intrusion-related gold systems occur on the South Island, then they are most likely to be discovered in association with the small molybdenite-, scheelite-, or cassiterite-bearing quartz stockworks spatially related to the Karamea and Median batholiths.

Jan 1, 2005

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