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By D Finn, D Kentwell

Experience has shown that the E-Type multiple indicator kriging (MIK) estimation technique often works well for resource estimation in stockwork mineralisation that contains a mixture of high and low-grade mineralisation types that are difficult or impossible to separate spatially. E-Type MIK, like ordinary kriging (OK) is a smoothing estimator and where data is sparse can result in estimates of grade tonnage curves that do not reflect the true block variability at selective mining unit (SMU) scale. The rank and replace (RR) estimation methodology is designed to reproduce both local block accuracy and true block variability at SMU scale and has shown good results when used with highly skewed unimodal diffusive style mineralisation. This paper examines the use of RR with mosaic style mineralisation typically found in stockworks via a case study using real data from Newcrest’s Telfer West Dome deposit. Resource level estimation results for ordinary kriging (OK), E-Type MIK and RR are compared to close spaced grade control models as the reference reality.Results show that stationarity requirements and declustering can severely impact on the usefulness of the rank and replace technique and that it should only be used where trends are not too strong and data are relatively uniformly spaced. This does not rule out its application to stockwork or mosaic style deposits. However, in this case, the presence of trends and different data densities requires the non-stationary domain to be further broken down into sub domains for the RR technique to be effective.CITATION:Kentwell, D and Finn, D, 2017. Testing new estimation techniques – rank and replace: a stockwork case study, in Proceedings Tenth International Mining Geology Conference 2017, pp 365–374 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By D Reid

Many of the relevant engineering behaviours of tailings are controlled to a large degree by the density of the material. For example, loose tailings are prone to brittle strength loss, while dense tailings are dilative (i.e. gain strength) at large shear strains. The critical state framework has been successfully developed over the past few decades to assess whether in situ conditions are contractive or dilative, and estimate relevant engineering parameters on that basis. Tailings comprising primarily silt-sized particles, when subaqueously deposited, often form a particularly loose state compared to subaerially deposited material of similar index properties. Such subaqueous deposition occurs in the decant pond area, where the tailings typically pluviate in quiescent conditions within a pond of standing water. Silt tailings deposited in such a manner have been observed to be extremely loose in a number of TSF investigations. Of particular concern, the deposited material in such cases appear to be significantly looser than can be reproduced in the laboratory - even using moist tamping, the sample preparation method which can usually produce the loosest samples possible in laboratory conditions. While the loose density of subaqueously deposited silt tailings is clear, in a well-managed upstream-raised TSF the decant pond is usually small and far from the perimeter embankments, however there are a number of examples where the engineering performance of such materials becomes relevant – for example, when historical deposition practices were poor, resulting in subaqueous deposition near the perimeter embankment. This paper outlines the geotechnical characterisation of a number of such subaqueously-deposited zones, compares the in situ state to that achievable in the laboratory, and discusses options for assessing the expected engineering performance of such materials when comparable laboratory tests are unavailable.

Jul 1, 2021

By G P. S Resende, D E. G Oliveira, E A. S Baeta, T F. Bravin

There is currently in the mining industry, as well as in other industries, a movement seeking to increase investments in decarbonisation processes to help combat global warming. Among some initiatives taken is replacing diesel-powered mobile equipment in the mines with electricity-powered equipment, such as electric off-highway trucks or even belt conveyors in the mining operation. Samarco is a Brazilian mining company that since its conception has used a conveyor belt mining system in its mining operation, using only a small number of trucks to complement the mining process. This mining process that combines conveyor belts and trucks has brought environmental gains for the company since the environmental impact of conventional truck-only mining is greater than that of the combined system. To measure these gains, a medium-term mining plan was developed in which two fleet scenarios were detailed. One scenario contemplated a high level of detail of belt mining seeking its maximisation, while the other considered the operation performed 100 per cent by trucks, eliminating the use of conveyor belts. Through the comparison of these two scenarios, it was possible to make an inventory of atmospheric emissions and greenhouse gases for each one of them considering data such as types of equipment, diesel consumption, total distance travelled and energy consumption. The results showed that the fleet scenario with conveyor belts results in periods with up to 15 per cent less greenhouse gas emissions and 37 per cent less total particulates compared with the truck-only scenario. Therefore, the results confirm the environmental benefits of the method and the need to look for ways to even expand it in future operations through a study to identify the potential areas in the long-term mining plan.

Sep 18, 2023

By S Bluhm, R Funnell

Creative mine-designs are constantly being applied in the deep platinum mining industry in South Africa. Recently, this has resulted in deep hot mine-designs including room and pillar, bord and pillar or stall and pillar layouts and the use of in-stope trackless mechanisation. In these mines, the ventilation systems use refrigerated air and high fan pressures and as a result ventilation leakage can have a huge impact. Leakage is a serious impediment to cost-effective operation and potential leakage in future projects is a major factor in judging project viability. This paper describes certain mine layouts and quantifies the extent of the leakage. Based on typical field data, a range of seals from ævery poorÆ to ævery goodÆ was defined and used to estimate overall leakage. Within these mine networks the ventilation pressure, temperature and density all vary significantly and with the multiplicity of leakage paths it was necessary to make use of the VUMA-network simulation package. For the examples examined, the leakage was found to be up to 85 per cent for æpoorÆ category seals and up to 50 per cent for ægoodÆ category seals. The total air flow (and refrigeration) requirements grow exponentially with strike distance due to the compounding effects of higher pressure and more leakage paths. It is shown that beyond certain depths and strike distances the leakage will become so great that it will be impossible to operate cost-effectively û even with ægoodÆ seals. Indeed, in these examples the projects were not considered viable in their original format because of the high ventilation-cooling costs and the mine-designs were modified to include footwall drive systems û the cost of which was justified by the reduced strategic risk to operating ineffectiveness due to leakage.

Jan 1, 2005

By L Mollison, K W. Mills, N R. P Baczynski, M F. Lee, I A. de Bruyn

This is the first of two papers concerned with rock stress inputs to various mine design issues at the large Ok Tedi open pit mine in Papua New Guinea. The companion paper (also published at this conference) is ‘The Application of Rock Stress Inputs to Stability Assessments at Ok Tedi Mine, Papua New Guinea’ (de Bruyn et al, 2014).Stresses are a required input for numerical modelling of mine design issues. However, for some operations, like the very large Ok Tedi open pit mine in remote rugged mountainous terrain, direct and representative measurement of rock stresses can be technically difficult and expensive. In such situations, development of an appropriate and sufficient understanding of rock stresses can be challenging.This was addressed for Ok Tedi by considering the following:The tectonic and regional geologic setting of the mine.Results from three different programs of rock stress measurement over 19 years, including hydraulic fracturing (1991), acoustic emission (2007) and overcoring (2010). Some interesting results of the overcoring work are discussed. It was done in a 4 km long drainage tunnel, which intersected a thick monzodiorite intrusive that has metamorphosed contacts to host contact Ieru Formation siltstones; anomalously low horizontal stresses were measured within the monzodiorite.Compilation of rock stress measurements from other New Guinea mines and prospects, both in Papua New Guinea and Indonesian West Papua.Comparisons between the variable Ok Tedi rock stresses and similar data from other porphyry copper deposits.CITATION:Lee, M F, Baczynski, N R P, Mills, K W, de Bruyn, I A and Mollison, L, 2014. Rock stresses at Ok Tedi, Papua New Guinea, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 337–346 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By Quintiliani G, Giordano V

A research field of interest and a topical subject with the aim to reduce a considerable amount of coke in ironmaking is the injection into blast furnace stack of hot reducing gas combined with use of auxiliary fuels at tuyeres. In recent years evaluation studies and prelimirfary industrial experiments have been carried out on this subject in Europe and Japan. Even if these experiments seem to confirm the advantages theoretically expected, it appears as useful to cast more light on new problems concerning the improvements of this technique. In this report some aspects are analysed on fluid dynamics of blast furnace process with two gas flows: the main flow coming from the bosh and cross flow of the reducing gas injected in the lower shaft. A research on a blast furnace physical model was made with the aim to obtain information about the phenomena which occur in the full scale blast furnace. This work was carried out on cold models IN and tridimensional) in which the radial gas distribution was experimentally measured. A mathematical model based on gas diffusion was implemented aimed at simulating gas distribution inside the reactor taking into account the number of injection tuyeres. A good agreement between experimental and theoretical data allows for extending results to industrial practice in order to determine operating conditions assuring good performance of blast furnace with high amount of auxiliary fuels.

Jan 1, 1975

By F J. van Zyl, C A. S Thomson

"Anglo American Thermal Coal conducted a high level study of all of its underground collieriesto determine if there were electrical power saving opportunities at the main fan stations.A systems approach to electrical power savings was used to identify potential savings in the various components of a primary ventilation system. Furthermore, only technological interventions were considered to obtain electrical power savings. From generic technological driven electrical power saving strategies four energy savings strategies were identifi ed, namely potential overall reduction in ventilation volume, improved underground air utilisation, optimisation of fan-set effi ciency and potential fan drift design optimisation. The study indicated the colliery (say Colliery D, Shaft A) that showed most potential in the four technology driven energy savings strategies. A detail study was undertaken at Colliery D, Shaft A to increase the confi dence level and the study confi rmed that up to 45 per cent of the main fan absorbed power can be saved (475 kW) with an estimated capital payback period of 18 months. The study clearly showed that an integrated approach to optimise the entire mine ventilation system has great potential for power saving, and that a clear, well -defi ned methodology will be applicable to similar underground collieries. This paper discusses the background to the study and the process followed to implement the energy savings initiative at Colliery D, Shaft A."

Jun 1, 2012

By G Fergus, M Hart, S W. Weeks

Rio Tinto Alcan has undertaken feasibility level assessments into the expansion of its bauxite mining operation in an area south of the Embley River in far north Queensland. The project has the potential to extend their Weipa operations by approximately 40 years.The construction and operation of two additional mineral ore processing plants are proposed for the South of Embley project. Golder Associates was engaged to develop and conduct modelling assessments of potential sources of water supply required by mineral ore processing.Two models were developed using GoldSim: a dam yield model and a water balance model. GoldSim is a graphical object-oriented modelling environment with a capacity to carry out dynamic probabilistic simulations. Originally developed by Golder, GoldSim has been applied successfully in a decision support role to a range of mine water management operations.The dam yield model was used to provide estimates of reliability and volume of annual water supply of several potential surface water dams. This information was then used to determine a hierarchy of water supply options for processing plant operations. The water balance model dynamically simulated the water demands of the two production plants and the consequential response in water supply, with respect to the timing and discharges provided by the various source options.Use of the model provided a preliminary operational tool to assist with water supply management decisions. Water quality issues required a blending of water from separate sources and attention paid to scheduling to ensure water supply through the dry season. The model also helped identify risks to water supply in the event of underperformance of one or more water supply sources. This allowed the operational rules to be refined to minimise those risks.The dynamic and stochastic modelling approach provided a method for identification of water supply issues susceptible to seasonal climate variability.CITATION:Weeks, S W, Hart, M and Fergus, G, 2013. A dynamic evaluation of water supply security susceptible to climate seasonality, in Proceedings Water in Mining 2013, pp 197-208 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

For over 50 years R W Miller & Co Pty Ltd operated old coal properties abandoned by former owners as uneconomic, some of which dated back to the last century. The companyÆs ability to survive with what were relatively poor quality coal resources required a small efficient management organisation. In 1970 R W Miller was involved in negotiations with other coal companies through coal sales contracts to develop private coal areas under the provisions of the old Coal Mining Act (1906) and these efforts led to the development of Lemington colliery. At the same time development of the Ironbark colliery holding near Newcastle commenced. In 1971, R W Miller approached the New South Wales Government for a resource replacement area to prospect for coal in the Upper Hunter Valley. Authorisation No 33 was finally granted on 30 September 1975, but the company found the area was inaccessible as most of the surface was owned by the Australian Army. Later R W Miller was granted Authorisation 66 of 2167.5 hectares at Mount Thorley near Singleton on 1 November 1976. The development of this coal mining project coincided with the second OPEC oil crisis in 1978 and a short-term boom for coal resources and the unrealistic expectations generated by the boom. This paper gives a broad outline of the development of the Mount Thorley project between 1976 to 1986 including the feasibility study and the many governmental and industrial delays that resulted in a three-year time overrun in the project development period.

Jan 1, 1998

By M E. Watson

Minimising dilution and ore loss is an important part of ensuring profitability of a gold mining operation. White Foil open pit gold deposit is a low-grade deposit and therefore managing ore quality is a high priority. Ground movement through blasting can displace ore and waste boundaries up to 10 m from their in situ location and therefore requires stringent ore movement monitoring and adjustment. There are currently only two options for monitoring blast movement – utilising visual targets (commonly lengths of polypipe) but this has widely been replaced by electronic blast movement monitors (or BMM). Regardless of the technology used, the basic principle is to compare the pre- and post-blast locations of the targets to determine the movement of the rock mass during blasting, which is then used to determine the final location of ore and waste boundaries.The Blast Movement Technologies (BMT) BMM system has been used at White Foil since June 2014. The system has been effective and reliable during that time; however, the annual cost of using the BMM system is greater than other monitoring alternatives. As such, the open pit geology team conducted a study comparing the BMM system against the conventional polypipe technique. The objective was to quantify the profit and loss that would occur based on the ore block transformations from both methods. Eight blasts were selected where polypipes were installed in additional holes adjacent to the BMM monitoring holes. The resulting movement vectors from the respective methods were used to create post-blast ore blocks by transforming the in situ ore blocks. While polypipe is a cheaper alternative, the BMM system tracks ore and waste boundaries more effectively resulting in better quality control, enhanced ability to minimise dilution and ore loss thus maximising profit. For these eight blasts, it is calculated that the BMM system resulted in A$664 978 extra profit through a reduction of ore loss. The total cost of a yearly BMM package was recovered in the first two blasts of this study. The primary reason for the difference is that polypipe had a poor recovery rate of 32 per cent compared with 92 per cent for BMM at White Foil. Therefore, the data used to transform the ore blocks was less representative, resulting in inaccurate post-blast ore block boundaries when using polypipe.CITATION:Watson, M E, 2017. Blast movement monitors or polypipe? A study into cost-effective blast movement monitoring at White Foil gold mine, Western Australia, in Proceedings Tenth International Mining Geology Conference 2017, pp 433–440 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By Pigdon SP, Anderson RM

The production of stabilised backfill at mine sites commonly uses Portland cement as the binder. Calcined gypsum has cementing properties and is cheaper to produce than cement. This paper discusses the strength of fills stabilised with calcined gypsum. Laboratory tests were carried out on specimens prepared from tailings obtained from four different sites to allow for the wide variety of tailings found in practice. The results show that the gypsum-based fills can achieve a strength of I MPa using around two and a half to four times the corresponding amount of cement.

Jan 1, 1998

By Brzezniak W

Conversion to trolley assist is a means of minimizing diesel fuel consumption, which in many mining situations offers a rapid payback of capital investment plus the inherent flexi- bility and maneuverability of truck shovel op- eration. Whendiesel electric truck shovel mining opera- tion with trolley assist is compared to alter- native mining methods such as conveyor systems, the trolley assist system can be easily justi- fied in terms of return on investment, payback and increased productivity. A review of present technology, performance requirements and past experience in the min- ing industry has led to the development of a trolley assist system for diesel electric haulage trucks which, is proven in the mining environment, offers significant reduction in fuel consumption and increased productivity.

Jan 1, 1981

By P A. Montoya

La Colosa is a world-class porphyry Au project located in Colombia, currently undergoing prefeasibility analysis. As part of collaboration between AngloGold Ashanti and the AMIRA P843A GeMIII Project, the application of emerging geometallurgical characterisation testing and modelling tools has been incorporated in early stages of project development. The aim of the geometallurgical study is to map inherent comminution variability across the La Colosa deposit providing information critical for mine/mill design and optimisation. In this study, site-based data incorporating multi-element assays, quantitative analyse X-ray difraction QXRD bulk mineralogy measurements, EQUOtip rebound hardness data, and routine geological logging information from 59 diamond drill holes has been integrated with a range of geometallurgically specific comminution test (ie GeMCi, A × b, BMWi). The work in this paper demonstrates the integration techniques used at La Colosa to link routine data acquisition methods with comminution test results through the development of proxy support models. The integration incorporates a range of statistical techniques including principal component analysis and regression modelling. By creating proxy models, comminution index estimates can be propagated into the geological database enabling comminution processing domains to be defined. These domains provide the first spatial representation of comminution performance and variability at La Colosa and can be compared against traditional geological domains. This study provides the foundation for ongoing comminution characterisation as the La Colosa project evolves through project cycles into an operational mine.

Sep 5, 2011

By Flierman GA, Van Toor CH

Investigations were carried out of burden distribution using a full scale model of the furnace top. Various charging sequences were used and large differences were found between ore charged as sinter-pellets and as pellets-sinter. These were attributed to the differences in the angle of repose between the two materials. Permeability index was defined which was independent of the driving rate from which a furnace resistance index was obtained for use in weekly reports. Results are summarised as a single expression between blast rates and pressures and the values of Qbl and Qmax are continuously measured to aid the operators in controlling the wind rate in the safe AP region. Results also indicate a reserve in capacity of No. 7 BF.

Jan 1, 1975

By F Owusu-Mensah, F Nsarko

The Obuasi Mine has been in operation for the past 100 years. Within this period a host of mining methods have been employed during its various changing phases. The causes for the changes are multiple, ranging from orebody capability, dynamics, technology, safety, economics, production levels, geotechnical, etc. Mining methods applied have also ranged from timber square setts, conventional cut-and-fill, shrinkage stoping, sublevel caving, mechanised cut-and-fill, longitudinal and transverse open stoping, and lately longitudinal retreat mining method (LRMM).The Obuasi Mine has a world class underground resource potential of about 27 million ounces. A third of this is in reserve. The orebody is subvertical, with multiple lodes and with widths ranging from 1.5 - 40 m. It stretches along 8.5 km N/S strike. A cursory statistical analysis on the various resource ore widths show a higher percentage (60 per cent) of the resource being within the range of about 1.5 - 10 m. Thus a high proportion of the resource is amenable to narrow vein mining methods. This has enhanced the choice of LRMM as an alternative method. Also, with the increasing cost of mining over time, LRMM, which eliminates expensive and time consuming footwall drives, will become far more advantageous as compared to the transverse/longitudinal open stoping methods which currently constitute about 40 per cent of the total underground production.The LRMM currently delivers about 20 per cent of the Obuasi Mine production. Plans are underway to improve total underground production from the current average of 160 000 tpm to about >180 000 tpm in the next few years and about 20 - 40 per cent more in the foreseeable future. Recoverable ounces will also increase from 26 000 to about 34 000 ounces per month. The proportion of LRMM in the business plan is also expected to increase from the current modest level to about 50 per cent. Despite its tremendous advantages in terms of economics and productivity, the method is facing some challenges during its inception. The objective of this paper is to highlight some of the emerging challenges and their effect on production and offer possible remedies that could mitigate the current and possible future challenges.CITATION:Nsarko, F and Owusu-Mensah, F, 2012. The Obuasi mine - longitudinal retreat mining method application and challenges, in Proceedings Narrow Vein Mining 2012 , pp 59-70 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

The fire started in the development section from methane released into the mine through a roof-bolt hole. The date was 8 May 1998. The flames spread quickly as the coal was ignited. After eight hours the Safety Department decided to seal the vertical ventilation shafts and the slopes. The quality of coal in the Esmeralda Mine is very high quality, and Minerales Monclova (MIMOSA) decided to recover the facilities, however, the Esmeralda Mine coals have a very high gas content of 12 m3/t. Immediately after the mine was sealed, MIMOSA staff implemented a plan to monitor the gas levels underground and contacted specialists for assistance in bringing the mine back on-line. During the next 2.5 months, MIMOSA staff and the specialists observed and analysed the gas behaviour supported by a chromatograph. With the results of the observations and analyses, MIMOSA in consultation with the specialists developed a recovery plan based on flooding the area in which fire might have propagated and in which rekindling was highly probable. Those results were analysed by the command centre (Mexican engineers responsible for mine recovery). At the same time MIMOSA trained rescue teams which included miners who had no previous experience in mine recovery operations. By 20 August 1998, the mine command centre had re-opened the slopes seal. Using a æStep-by-StepÆ system, the rescue team began the recovery process by employing cross-cuts and using an auxiliary fan to establish the ventilation circuit. The MIMOSA team advanced into the mine as far as allowed by the water level and was able to recover the main fan. The official mine recovery date was 30 November 1998.

Jan 1, 2005

By M Gerards, M Steinberg, T Graham

The quality and quantity of Australia’s secondary deposits, which include tailings streams and tailings dams, are higher than most countries’ primary deposits. In addition, these secondary deposits have already been mined and processed, meaning that the recovery of high-grade product requires low capital and operating costs.The most widely used process for the recovery of these valuable fine and ultra-fine hematite iron particles is the wet high-intensity magnetic separation technique, originally developed by Dr Jones over 55 years ago. Many of the original machines are still working today.The aim of this paper is to demonstrate the capabilities in terms of grade and yield of using sophisticated magnetic separation modules. All results and figures are obtained from test work and design and engineering work with material from the Pilbara. In addition, consideration is given to dewatering of iron ore product and tailings.Two types of tailings have been identified for processing. Firstly, tailings that have already been deposited in a tailings storage facility, and secondly, live tailings streams from an existing wet iron ore beneficiation plant. In both cases, the technical and practical results are shown along with relevant flow sheets and plant layouts. Finally, this paper highlights the total predicted power and water consumption, capital requirements and projected operating expenses.The results show that the operating costs are significantly lower than the mining and processing operations that are required for an equivalent amount of iron ore. The recovery of iron depends on various factors but is within the 30–50 per cent range at an equivalent grade to the mainstream product. Another significant benefit is that the magnetic separation process is water positive, meaning that water is released rather than added in the process.The processing of the Pilbara’s secondary deposits will therefore result in an overall reduction in operating costs, an increase in product yield from a plant, extend the life-of-mine and offer environmental benefits by reducing the tailings footprint and water usage.The quality and quantity of Australia’s secondary iron ore deposits and tailings are such that many other countries would judge these as equivalent to primary deposits. Furthermore, these tailings are already mined, available and liberated to such an extent that the recovery of a valuable product is highly economical in terms of capital expenses and operating expenses.CITATION:Steinberg, M, Graham, T and Gerards, M, 2015. Recovery of iron ore fines and ultrafines from tailings by using wet high-intensity magnetic separation – JONES WHIMS, in Proceedings Iron Ore 2015, pp 191–196 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By G Maude, R Ayres, R N McLean, N A. Reynolds

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Mabilo copper-gold-magnetite skarn deposit is located in southern Luzon in the Paracale mineral district, where iron has been produced historically from several skarn deposits. Mabilo occurs in the south-west of the district and is distinct and significant because of its high grades of copper and gold compared to historical mines.The Mabilo licence surrounds the Venida prospect, where past small-scale mining has exploited iron, copper and gold mineralisation in oxidised skarn. A ground magnetic survey in 2007 defined a number of strong anomalies under Quaternary volcanic cover south of Venida. The property was acquired by Sierra Mining Ltd in 2011, the magnetic data were remodelled and drilling commenced in September 2012. Diamond drill hole MDH001 targeted the strongest anomaly, which was 500 m south of Venida and under 20 m of volcanic cover. It intersected 94 m with an average grade of 2.2 per cent copper, 1.6 g/t gold and 36.6 per cent iron. Subsequent drilling was targeted by magnetic modelling, incorporating magnetic susceptibility data from drill core, which resulted in a high percentage of successful drill holes.The mineralised skarn preferentially replaces a dipping limestone unit within an Eocene sequence dominated by volcanic siltstone and sandstone, metamorphosed to marble and hornfels in the aureole of a Miocene quartz-diorite intrusion. Skarn occurs discontinuously along the eastern and southern diorite contact, controlled by primary sedimentary facies variation, structural geometry, fault offsets and intrusive contacts.Coarse magnetite skarn with garnet and minor wollastonite and clinopyroxene contains variably abundant chalcopyrite and minor molybdenite. Magnetite skarn occurs in sharp contact with unaltered marble or grades into garnet skarn with minor chalcopyrite. Structurally controlled retrograde skarn alteration is strong to intense and is characterised by bornite, clinozoisite, iron carbonate and chlorite. The retrograde skarn is weakly overprinted by late-stage pyrite veining and brecciation associated with clay-silica alteration with arsenopyrite and tetrahedrite-tennantite.The quartz-diorite stock is interpreted as the source of the prograde skarn-forming and mineralising fluids. Late-stage porphyritic intrusions in the contact zone indicate continuing magmatism during uplift, when telescoping led to a high-level, high-sulfidation overprint. This suggests the potential for deeper porphyry-style mineralisation.CITATION:Reynolds, N A, Ayres, R, McLean, R N and Maude, G, 2015. The Mabilo copper-gold-iron deposit – a new skarn discovery in the Philippines , in Proceedings PACRIM 2015 Congress, pp 431–438 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By B Rouvray, R Bertuzzi

The development of a design-and-construct tunnelling project in Australia from its concept to its construction requires designs to be prepared and reviewed at several distinct stages prior to documenting ‘for construction’. On recent projects the post-tender stages have been variously called 30 per cent—70 per cent—100 per cent; or concept–substantial–final; or system definition–preliminary–critical. The design is reviewed at each stage by the designer’s internal reviewer, the contractor and its independent advisor(s), the owner and its independent advisor(s), the project’s independent certifier, proof engineers and often third-party stakeholders and their advisors. Documentation for each stage often dominates the design effort, at times distracting from design. This paper presents the authors’ experience of this design-and-review process. Comparisons of design budget and actual design spend and design program implications are presented. It is postulated that a subtle change has occurred in our industry that has diminished the value of the design dollar. Is there a better process? An alternative is suggested.CITATION:Bertuzzi, R and Rouvray, B, 2014. Reducing the cost of tunnel design in Australia, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 501–506 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By J Hadjigeorgiou

The stability of open stopes in underground hard rock mines is influenced by several factors including the shape and size of the excavation, surrounding stresses as well as the degree of jointing. This paper presents a design methodology for stope analysis in jointed rock masses. The proposed approach relies on geological structural data to construct realistic three-dimensional joint network models. The stability of an open stope is determined based on a limit equilibrium analysis.

Jan 1, 2000