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By Kasaneva S

The San Cristobal gold district is located 110 km east of the port of Antofagasta, Chile. It contains the San Cristobal gold mine, where Niugini Mining Ltd. commenced a heap leach operation, with initial reserves of 10.1 million tonnes grading 1.34 g/t An, in December, 1990. The San Cristobal district occurs within an upper Cretaceous-lower Tertiary magmatic arc. The main mineralisation occurs within a northwest trending subvertical zone, 1km long and 70-100 m wide, which contains rhyolite porphyry and minor breccia, and is locally termed the "subvolcanic complex". At the San Cristobal mine, most gold mineralisation occurs in subvertical quartz-pyrite veins which were emplaced in dilational sections of an imbricate fault system. The bulk gold resource comprises four ore shoots which formed where the vein system intersects the subvolcanic complex. Gold-bearing quartz-pyrite veins also occur at separate prospects, the Three Sisters and Sol prospects, west and south of the San Cristobal mine. Hydrothermal alteration consists of potassic and propylitic assemblages related to intrusion of the subvolcanic complex. This alteration is overprinted by a phyllic stage which is associated with the emplacement of the quartz-pyrite veins. The oxide zone is 180 m thick, and contains native gold, electrum, limonite, and manganocarbonates. The underlying hypogene zone contains pyrite with minor chalcopyrite, sphalerite, galena, covellite, bornite, chalcocite, and arsenopyrite. Fluid inclusion studies indicate that the deposit formed at approximately 270¦ C, and the mean salinity of the fluid was 4% NaCl equivalent. These observations enable the San Cristobal deposit to be classed as a porphyry-related, mesothermal quartz-vein system of the low sulphidation type.

Jan 1, 1995

By P Bergin, J M. Galvin, J Harris, J Li, P Kirsch, M Shi, B Hebblewhite, B Whittaker, R Mitra, D Sprott

Controlling unwanted ground movement is critical in mining as well as many other highly hazardous environments, such as construction and tunnelling. Sharing knowledge about effective hazard management is paramount to improving health and safety and operational outcomes across industries, and some industry sectors have embraced this openness as part of the way that they do business. In 2010, the Australian Coal Association Research Program funded the RISKGATE project to build a body of knowledge for managing a broad range of hazards across mine sites, lease areas and mine infrastructure within a mine-life or product life cycle perspective (eg from exploration through to decommissioning, or design through to operation). The RISKGATE body of knowledge was assembled from Australian coal industry experts through a semi-structured bowtie analysis-based action research workshop cycle. By capturing operational knowledge from industry experts, RISKGATE serves to provide a cumulative corporate memory at a time of high personnel turnover in the coal industry.This paper presents an overview of RISKGATE topics within the geological and geotechnical domain (strata underground, ground control open cut, outburst, coal bumps and bursts, tailings dams and inrush) with a summary of individual topic structures, as well as showing the contrasts and inter-relationships between these ground management topics. The online user can access information about the causes, controls and consequences related to a priority unwanted event (ie the point at which control of energy is lost) and use this information as a prompt for the development of risk assessments, incident investigation, audits of practice/plans/procedures and for training and development.The paper concludes with a discussion of how RISKGATE can be adapted to other mining domains (eg coal outside of Australia, hard rock mining worldwide, construction, tunnelling) and the opportunity for application of this body of knowledge and the RISKGATE action research process for knowledge management in other highly hazardous environments.CITATION:Kirsch, P, Hebblewhite, B, Sprott, D, Harris, J, Li, J, Shi, M, Whittaker, B, Galvin, J M, Bergin, P, Mitra R and Williams, D, 2014. RISKGATE – shared coal mining knowledge for managing risks across ground management, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 247–254 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By Paine G. G

The measurement of the fragmentation size distribution of a blast muckpile can be achieved directly by screening the entire muckpile. Screening of muckpiles in a production operation is generally not practical due to the logistics and time involved moving large volumes of rock through a screening plant. An indirect technique to assess blast fragmentation size distributions has been developed. This technique uses photographs of the blast muckpile taken at intervals during the excavation cycle. The images from the photographs are input to desktop computer software via a digitiser tablet. The software compilates the rock fragment sizes and calculates a size distribution. This paper discusses the technique and subsequent data analysis. Examples of the application of this technique for the assessment of comparative blast performance are given.

Jan 1, 1990

By Bell LC

Overburden removal, mining and reclamation are now accepted as the basic operational steps involved in the winning of coal by open cut methods. To attain the lowest operational cost, the recontouring and revegetation of spoilpiles must be planned concurrently with the planning of overburden removal and mining. The earthworks associated with reclamation work on spoilpiles often account for 75 - 90 per cent of total reclamation costs. Experience at Callide Mine has shown that the way that spoilpiles are contoured does influence water retention and can reduce erosion from rainfall run-off. However, provided the recontoured slopes meet'Mines Department specifications, the quality of reclamation work is judged not by the quality of the earthworks but by the plant regrowth on the reshaped surface. Thus it is the quality of the revegetation which is of prime importance. For vegetation to be successful, time must be spent on planned research into methods of overcoming plant nutrient deficiencies and selection of suitable grass and tree species. The research programme undertaken at Callide Mine consists of three stages :- laboratory studies glasshouse trials field trials

Jan 1, 1978

Continuous, steady-state laboratory flotation tests showed that the recovery of cha1copyrite from a naturally occurring ore, under conditions closely resembling those of plant practice, could be expressed in terms of a first order rate equation.Tests on full-scale plant flotation cells, using impulse tracers, indicated ideal mixing of the pulp in the cells.It was demonstrated that values of first order flotation rate constants can onlv be obtained from conventional methods of analysis in special cases.Analysis of a plant sampling campaign by the author supported a first order kinetic equation for two mineral species, and for the individual size fractions of one of these.The effect of stage-addition of reagents is interpreted in kinetic terms.

Jan 1, 1966

By V Ser, I Smit, C Robertson

Anglo American has been researching the potential benefits of inter-particle comminution techniques for several years. Inter-particle comminution has additional benefits in terms of milling circuit performance such as energy consumption and stability. This paper focuses on the flotation benefits. Inter-particle comminution leads to selective breakage, mineralogical analysis has shown that this leads to improved liberation of the valuable minerals. In addition to selective breakage, the relatively short residence time experienced in typical inter-particle comminution machines allows more efficient classification which contributes to a æsharperÆ product size distribution. The effect of particle size in flotation has been well documented in literature. In general, it is has been shown that there is an optimal particle size range for flotation, and that both above and below this range, flotation recovery is adversely affected. Results show that the narrow size distribution which results from inter-particle comminution improves flotation recovery. Furthermore, the absence of excessive fine gangue material which typically results from conventional fine (-75 ¦m) milling of talcaceous ores, can lead to 100 per cent savings in depressant consumption when such ores are subjected to inter-particle comminution. To-date, this technology has been evaluated on more than ten ores. This paper will focus on one set of results which demonstrates a number of common differences that exist between material that has been milled conventionally and using inter-particle comminution technologies, with emphasis on what the impact of these differences is on flotation performance. A pilot scale (200 kg/h) vertical roller mill (VRM) was used to produce the material, and the results shown will describe conventional laboratory batch, locked cycle and pilot plant flotation testwork.

Jan 1, 2005

By Porter I

Rock mass classification systems have emerged as a powerful tool which can be used for assessing ground conditions and determining support requirements in underground mines. They should not be used as a substitute for complete engineering design, but rather as a supplement to observational methods and analytical study. In general, the use of rock mass classification is attractive, but each classification system has various deficiencies. Use of any particular system should be made only with knowledge of that systems limitations. It is desirable to employ a number of systems and design methods which will allow for comparison and lead to a better understanding of the rock mass condition.The Rock Mass Quality system (Q-System), developed by the Norwegian Geotechnical Institute, and the Rock Mass Rating (RMR) System, Bieniawski, were designed primarily for civil engineering structures. Laubscher et al (1978) further developed the RMR-system specifically for rock mechanics engineering in the mining industry. A method of stope design, which introduces a stability factor for the rock mass and compares this with hydraulic radius, was developed by Mathews et al (1981). This paper reviews the above systems by applying them to stability assessment of crown pillars in two Australian metal mines and provides a critical analysis of the various approaches. In particular each system will be analysed to determine its suitability for use in crown pillar design. The most suitable system(s) will form the basis for future development in crown pillar stability analysis.

Jan 1, 1994

By J Jackson, E Sellers

Blasting related indices were developed to quantify variation in rock strength and structure for each stope, and for each lift of each stope, as part of a Mine to Mill study at an underground open stope mine. The indices were derived from combinations of data from underground diamond drilling because the simplifying assumptions contained in the block model prevented sufficient differentiation in rock mass characteristics to enable adjustments to the blast design.Application of combinations of blasting related indices enabled the identification of stopes with a high potential for inconsistent and oversize fragmentation, underbreak and overbreak. The indices also fragmentation outcomes to deliver increased material flow within stopes, better digability and predict indicative mill throughput. The stopes with issuesCalibration of the results enabled adjustments to the blast design based on the rock mass conditions and accordingly improved the blast outcomes. This enabled improved productivity by reducing underbreak and overbreak, having a more appropriate fragmentation, which reduces unplanned rock handling and improves bogging. The reduction in recovery drilling creates huge opportunities to improve output by reducing production delays and decreasing the overall cost per tonne. By understanding the explosive performance and blast energy distribution in relation to rock mass blastability poor, performing designs in blind upholes and convex stopes were identified.The conclusion of the work is that value improvement, regarding increased revenue and reduced costs, can be achieved across the whole underground Mine to Mill process chain by developing stope based indices from the existing geological information to correctly tailor the blast design to the rock within, and surrounding, the stope.CITATION:Jackson, J and Sellers, E, 2017. Blasting related indices as the key to underground blasting improvements in a challenging rock mass, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 23–32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By P Hodkiewicz

Recent structural interpretations based on historic stope shapes were used to develop a rapid and innovative method to domain and simulate structurally complex, high-grade gold veins at depth in the Edna May deposit. This involved ‘implicit’ modelling of drill hole data using Leapfrog software, which allows complex wireframe domains to be built and updated rapidly, compared to ‘explicit’ manual wireframing methods that are too subjective and time consuming. Conditional simulation was used for resource estimation, in order to simulate the highly variable gold grades associated with the veins. Similar modelling methods could be used to determine the mining potential of other historic gold deposits that are receiving renewed interest because of the high gold price.Gold at Edna May is hosted in the Edna May Gneiss, which is a WNW-striking tonalitic intrusion along a shear zone that dips approximately 45° towards the NNE. Gold occurs in multiple 0.5 - 5 m thick arcuate quartz veins that plunge steeply towards the west. Two phases of historic underground mining at Edna May (1911 to 1922 and 1935 to 1947) produced 360 000 ounces of gold at an average grade 19.5 g/t from seven ‘reefs’ to a depth of 240 m. This established Edna May as one of the highest grade gold mines in Western Australia at the time.Recent drilling by Catalpa Resources confirmed the potential for down-plunge continuity of high-grade veins. New structural interpretations, based on historic level maps and wireframe re-constructions of the arcuate stope shapes, were used as ‘structural trends’ in Leapfrog to model the mineralisation. The resulting wireframes capture the complex distribution of gold in the deposit and were used as domains for resource estimation.Conditional simulation using the Turning Bands method was used to simulate the expected variability of gold grades associated with this mineralisation style and the median of the 100 realisations was used to report an inferred resource. Results of this modelling method are being used to target vein extensions at depth, to consider different underground mining scenarios, and to assess the risks associated with developing and mining this high-grade and high-nugget gold deposit.

Aug 22, 2011

By Poplawski R. F

A 32-channel PSS seismic monitoring system was commissioned at Mt Charlotte mine in 1994, and at the time it was the first such system in Australian mines. The system continuously observes the occurrence of seismic events and locates them accurately in space and time. Mt Charlotte has a history of seismicity, with the largest event in recent years of Richter magnitude 4.3. The decision to 'go seismic' was made despite some uncertainty regarding its potential usefulness. However after the first year of operation, benefits have been realised in terms of less production downtime, improved mine safety and mine planning, and better understanding of the nature of Mt Charlotte seismicity. The seismic network has performed well, recording 550 events in its first year of operation to a location accuracy averaging ¦ 12 metres. System reliability is excellent, with very little downtime, and acceptable operation and maintenance times and costs. Observations show major distinct changes in the rate of mining induced seismicity over time periods of weeks and months. Events have tended to cluster in specific mine areas and on particular faults and structures. Case examples of pillar preconditioning, breakout around an orepass, and a major stope rockburst, illustrate the role of seismic data and the benefits it brings to safety, productivity and planning.

Jan 1, 1995

By I Ritchie, G Lane, C Morley, D Yataco

Marcobre SAC (Marcobre) is developing the Mina Justa project in Peru. The project has a lower grade oxide orebody overlaying the higher grade sulfide orebody. The oxide ore is treated by acid leaching; consumption of acid is high and is managed by vat leaching rather than the more conventional heap leaching process.The leaching process uses ore crushed to 100% passing 8 mm to optimise copper recovery. Acid consumption generally increases with a higher proportion of fines. Marcobre is investigating a three-stage crushing circuit with high pressure grinding rolls (HPGR) in the third stage, instead of the more conventional four-stage cone crushing circuit. The use of HPGR can result in higher fines production due to the higher compression forces in the crushing zone. This paper reports on the outcomes of the test work completed by Marcobre in 2016 and 2017 to manage fines production and compare the use of HPGR with conventional crushing on a high acid consuming ore.At moderate pressing forces, a HPGR crushing circuit appeared to produce similar size distributions to cone crushing. On average, both the copper recovery and the acid consumption in subsequent vat leaching were higher with HPGR crushing than with cone crushing.CITATION:Lane, G, Morley, C, Yataco, D and Ritchie, I, 2017. Are there differences in size distribution when comparing conventional crushing and HPGR?, in Proceedings MetPlant 2017, pp 60–72 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 11, 2017

By E Yurakov, D J. Ashelford, M I. Slate

The push for increasing coal production rates continues to place increasing demands on mine management to safely and effectively control seam gas. Gas drainage strategies applied vary in both effectiveness and form. Methods employed are a function of assessed risk, gas reservoir characteristics, surface and underground access, budgetary constraints and gas utilisation potential. With the aim of establishing and optimising the effectiveness and efficiency of gas drainage systems, Australian coal miners in cooperation with gas management specialists are embracing the use of gas reservoir simulators and gas emission models. This paper discusses the evolution of gas drainage practices in Australian underground coal mines and the role of gas reservoir assessment methods in optimising gas drainage systems and gas production forecasts.

Jan 1, 2005

By Fulton E, Ring RJ, Waters DJ

Laboratory leach tests of Nabarlek uranium ore carried out by the Australian Atomic Energy Commission to compare the effectiveness of Caro's Acid1 (permonosulphuric acid) as an alternative oxident to pyrolusite indicated reduced acid consumption in leaching and lime savings in neutralisation of tailings liquors when using Caro's Acid. Interox Chemicals Pty. Ltd. arranged a plant trial for Caro's Acid at Queensland Mines Nabarlek Plant. The trial confirmed that significant savings in acid and lime can be achieved under plant conditions. Plant operations also demonstrated improved redox potential control was possible using Caro's Acid.

Jan 1, 1978

Resource rent tax is a form of taxation or royalty, which only become effective at such a time as a pre-determined rate of return has been achieved by an operation. The offshore petroleum industry in Australia is already subject to RRT as is the Roxby Downs (Olympic Dam) Mine in South Australia. Both the mining and petroleum taxation regimes in Papua New Guinea include a resource rent tax component called Additional Profits Tax (APT). The implications of the current form of Additional Profits Tax for shareholder cash returns are that the tax burden on the operation may suddenly increase at some stage in the life of the mine, if and when the threshold level of profitability for the tax to be triggered is exceeded. From that point in time onwards the cash return to the shareholders on the capital invested is greatly diminished. For mining companies in Papua New Guinea, the effective tax rate increases from 35% to 57.75% as a result of the onset of Additional Profits Tax. This tax rate penalty is so severe that there appears to be merit in considering the concept of managing profitability through time rather than purely maximising annual pre-tax profits as is currently the case in most mining operations. This would have the benefit of deferring or perhaps preventing altogether the onset of the tax. One possible method for the effective management of profitability is through the control of average mining grade by cutoff grade manipulation. Traditional cutoff grade theory has usually considered taxation as a direct cost at a fixed or variable percentage of annual profits. As a result of this most analyses are conducted on a pre-tax basis. If tax is included in analyses it is usually present as a time independent function of gross profit. Additional Profits Tax is both time and rate of return dependent and therefore not adequately accommodated by currently accepted cutoff grade theory. A review has been made of the effects of resource rent taxes on both the investment decision-making process as well as possible development and mining strategies which may be employed by mining companies faced with Additional Profits Tax. The review includes examples based on the structure of Additional Profits Tax which is levied in Papua New Guinea.

Jan 1, 1997

Once and for all, the debate on the exponent in Gy's formula is pushed to its limit. It is explained why an exponent of 2.5, obtained when using a square root of nominal size d to adapt the value of a calculated liberation factor to a different comminution size, will rarely be encountered in practice, if no arbitrary decisions are made.

Mar 1, 2010

Predictive chemical models facilitate the selection, design and assessment of aqueous chemical processes. The development of expertise in aqueous themochemistry has not matched the explosion in computer technology for modelling, which has placed pressure on the need for acquisition of skills to critically assess the appropriateness of the models produced. The 'blind faith' culture which appears to be developing must be arrested by appropriate programs at the tertiary level and professional development strategies in the minerals industry.

Jan 1, 1996

By P J. Hawke

Within the Mesa J pisolitic iron ore mine, clay is distributed unevenly throughout the deposit and often forms as pods and channels less than 10 m in width. The mine resource model, based on 50 m + 50 m spaced drilling, has been unable to accurately delineate the clay for scheduling and mining purposes. Therefore, alternative methods for mapping the clay-contaminated ore were sought. Predictive clay mapping will significantly reduce production costs at Mesa J through improved selective mining practices, more accurate scheduling, reduced wear on mining equipment and minimising the need for maintenance of haul roads and ramps. High lateral resolution electromagnetic (EM) surveying using a Geonics EM31 instrument can quickly and inexpensively delineate the extent and orientation of the clays. Preliminary results indicate that a block model based on the interpretation of the EM data can accurately predict the distribution, volume and tonnage of ore and waste material. While rip-line mapping, infill drilling, ground penetrating radar and gravity can delineate clay with various degrees of success, none were as efficient as EM31.

Jan 1, 2002

By Chaves AP, Delboni H. Jr

Thermal comminution is an industrial process specially suited to very abrasive material, when contamination with Fe from wearing parts of conventional crushing and grinding equipment must be avoided. It involves an initial step of heating the material to be comminuted, followed by sudden cooling (quenching) and finally by a conventional mechanical process to disassemble the particle aggregates. The thermal step is, in fact, a pre-fracturing process. The heating operation causes changes in phase of the minerals and changes in volume of these minerals and other substances included in pores and cracks. The cooling operation causes thermal shock reversions or the phase transformation and consequent generation of internal stresses, high enough to fracture the solid.

Jan 1, 1993

For some time the-mining industry has been criticised, completely unjustifiably, by certain people who style themselves conservationists but are actually preservationists. The criticism of the mining industry - and indeed all developmental industries has an emotional background and is not supported by facts. Some claims have been so disturbing that the Australian Mining Industry Council considered that the industry should do more in stating its position and attitude than has been done to date. It was therefore decided to request the Australasian Institute of Mining and Metallurgy (which is a technical organization) to join with it in presenting this seminar so that the subject could be examined on a scientific and factual basis, removed from the pressures of, emotion, and so that the media and the public could be presented with some basic factual data and, I trust, convinced of the soundness of the industry's attitude and policy. Many of the individuals in the mining and metallurgical industry are men who chose mining as a career because the location of mines gives an opportunity normally available only in the more remote areas. "These men do not want to see their countryside despoiled. '-The mining companies they manage and w rk for have accepted a responsibility to the environment which grows out of their close relationship with the earth.

Jan 1, 1971

Wheal Gawler was Australia's first metal mine. This leader was followed by an army of other metalliferous underground mines and surface operations in Australia. As a mine it was not highly significant economically because its small total production of nearly pure galena had low multiplier effects on the economy of South Aus- tralia. Its importance lay in its symbolism: here was a silver-lead mine close to the new town of Adelaide posing the question of what other min- erals lay in the Mount Lofty ranges and in the fields beyond.

Jan 1, 1987