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By M I. Pownceby, M A. Rhamdhani, D M. Fellicia, S Palanisamy, R Z. Mukhlis

The trend of global copper production has prospectively increased over time. Based on typical mined ore grades, 1 t of copper ore generates approximately 6–10 kg of copper, which requires much energy, usually in the form of metallurgical coke. Copper production using carbon as a fuel and reductant contributes up to 0.3 per cent to global greenhouse gas (GHG) emissions. As a result, research into decarbonisation processes applicable to reducing low-grade copper sulfide ores, copper oxides, electronic wastes and other alternative complex Cu-rich materials has increased. Alternative fuels for reducing carbon-rich emissions in pyrometallurgical copper processing include methane, ammonia, biomass, solar and wind power, but in recent times increased focus has been on hydrogen as a potential fuel and reducing agent for materials such as oxidised copper scrap, Cu2O/CuO and Cu-rich slags/e-wastes. From a thermodynamic perspective, hydrogen exhibits a significantly more negative standard Gibbs free energy (ΔG°) than copper oxide making it a suitable reductant and the exothermic thermal effect from reaction between hydrogen and Cu2O/CuO may be used to control process parameters. These characteristics renders hydrogen an ideal gas for reducing copper oxides and copper-containing slags/e-wastes. This review article assesses previous research on utilising hydrogen for producing and refining copper from primary and secondary feed materials.

Jun 19, 2024

By Q Gong, J Li, J Zhao, Y Zheng

Excavation by tunnel boring machines (TBMs) offers many advantages over conventional excavation methods, in terms of safety level, working environment, advance rate and overall cost. While TBMs have been extensively used in civil tunnel construction, they are also viewed as a competitive alternative to the drill-and-blast method for underground mining, attracting increasing attention from the mining industry. This paper presents an overview and general assessment on applications of TBMs in mines, by reviewing more than 60 TBM applications in underground/open pit coal and hard rock mines around the world. The projects range from the early exploratory trials of TBMs in mines in Germany, England, South Africa and America in the 1960s and 1970s, to the ongoing projects in Australia, China and Chile. The paper focuses on the geological compatibilities, the problems encountered, the solutions undertaken and the lessons learned from those projects. The paper summarises the progress made in the past and highlights the challenges faced by TBMs in mining due to complex ground conditions and geometrical requirements. With the technological advances of TBM and experiences gained in the past, more applications of TBMs are expected in underground coal and hard rock mines.CITATION:Zheng, Y, Gong, Q, Li, J and Zhao, J, 2014. A review of the applications of tunnel boring machines in mines, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 691–704 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By M R. Asef

Although generation of environmentally harmful hydrogen sulfide is considered to be related to sour gas fields, sweet gas reservoirs and waste fluids, travertine springs and geothermal fields may also produce acid gas (H2S and CO2) under certain conditions. The potential parameters influencing such a possibility need to be fully investigated to evaluate the extent of the consequences and predict hydrogen sulfide generation accordingly. Reports on hydrogen sulfide production at different regions and fields were gathered worldwide for the cases when some of them did not have such a problem previously. In order to inspect different aspects of these case studies, some other regions with no hydrogen sulfide content were selected as control. In all cases water samples were taken carefully for chemical analysis in the laboratory. Besides, mineral compositions were characterised in some cases for better evaluation. In order to give a thorough prospect of hydrogen sulfide production, a geochemical model was prepared. In situ engineering geological conditions, especially pressure and temperature, were assigned in the model to investigate the possibility of H2S generation using PHREEQC software. The results of modelling revealed that although many similarities existed between mineral compositions of the cases, certain formations were particularly prone to hydrogen sulfide generation. For better evaluation, important exchangeable cation ratios such as potassium/sodium, calcium/magnesium and ion proportions like sulfate and chloride were calculated as trends of the formations. As expected, the model could successfully monitor a higher ratio of SO42- and Cl- in potential H2S generator formations. Wide variation in percentage of HCO3- was considered as a secondary observatory parameter for better estimation. In addition, it was noticed that higher anion content created an environment ready to absorb any cations and this makes H2S generation easier. Finally, using correlations between predictors and estimators for low depth and deep samples defined the degree of effectiveness for every sample.

Sep 26, 2011

By P Gehrke, S O’Gorman

The precise measurement of NO2 was historically difficult in road tunnels, hence criteria and design analysis was based on converting from NOx concentrations via a set NO2:NOx ratio. The reliable direct measurement of NO2 is now possible, however design analysis is still dominated by emissions tables and formulas specified in terms of NOx. For converting from NOx to NO2 in a road tunnel environment in Australia, the ratio has typically been assumed to be ten?per?cent. This has generally been based on the recommendation in PIARC (2000) and on the ‘average’ value cited in PIARC (1995).Determining this ratio is important as changes in engine technology and in-tunnel pollution criteria along with improvements in CO and particulate emissions control, may mean that NO2 will become the driving factor for future ventilation requirements. Correct selection of this ratio can directly impact the ventilation capacity and system design.Recent research has indicated that choosing a constant ratio of ten?per?cent for all tunnels may not be appropriate. The in-tunnel ratio has been estimated to be as much as 20?per?cent to 30?per?cent and depends on the location in the tunnel, the type of ventilation system and the traffic/fleet characteristics. This paper discusses the effect of some of these parameters on the NO2:NOx ratio in road tunnels.The findings indicate that the ten?per?cent upper limit on the NO2:NOx ratio in PIARC (2000) may be a conservative value for design purposes for longitudinally ventilated road tunnels of typical length in Australia. A value of seven?per?cent to eight?per?cent may be more appropriate in some circumstances. However, the value chosen will depend on the specific tunnel in question and the confidence in traffic conditions expected. Values above ten?per?cent may be encountered for short periods but usually when the NO2 levels are low.CITATION:O’Gorman, S and Gehrke, P, 2014. NO2:NOx ratios in Australian road tunnels, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 95–102 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

Mining is an intensive resource development industry, where operations are often of relatively short duration and can result in dramatic impacts on the natural environment during the operational period and for many years post mining. An integral component of all mining operations is water û through exploration, resource definition, mine development and operation, rehabilitation and the long-term post-mining land use. Water is a basic requirement in the provision of worker amenities, in drilling, as a means of dust suppression, as a medium for washing or processing the mine product, and as an aid in establishing vegetation on post-mining landforms. Water also plays an important role in mobilising environmental contaminants and is the primary medium for the transport of contaminants off the mine or processing site into the wider environment. It is for this second reason that the mining industry considers water management as a key component of mine management. Cost-effective water management relies on planning that incorporates a total mine system approach commencing prior to exploration and continuing through to rehabilitation and decommissioning. One of the primary considerations that will provide confidence to both government and community at the time of mine closure and lease relinquishment, will be the evidence that any water originating from, or passing through, the mine site is of a quality that will not have any negative impact on the surrounding environs into the future. The role of vegetation in stabilising disturbances to a landscape is well known, as is the recognition of vegetation being a fundamental component of the water cycle through the physiological processes resulting in the transfer of water back to the atmosphere through transpiration. In terms of water management at a mine site, the two crucial issues are the æquantityÆ and æqualityÆ of water that enters a receiving æoff-leaseÆ catchment. In terms of tolerances of the receiving environment, the total load of potential contaminants becomes critical, a reduction in which can be achieved through reduced volumes of water discharged, reduced chemical and physical concentrations of contaminants in that water, and ideally, both. This paper examines the potential role of vegetation in reducing the quantity of water released from a site, and secondly considers vegetation in the role of influencing the quality of that water.

Jan 1, 2003

By M Norbert, P Mok

The mainline running tunnels for Legacy Way comprise of two-lane tunnel boring machines (TBM) driven tunnels. The length of the TBM tunnel section is approximately 4.2 km. The TBMs employed are double shield TBMs. Typical support to the segment ring while advancing a double shield TBM comprises of filling the excavated annulus between the ground and the segmental lining by injecting pea gravel, followed with primary grouting to fill between the pea gravel some distance behind the excavated face. The methodology adopted for the Legacy Way project, however, did not follow this typical approach, instead, two component grouting of the annulus was carried out.Where the annulus is typically filled with pea gravel, support is provided to the segment ring very close to the end of the tail shield, whereas in the case of two component grout this is not practical as the risk of grouting in the tail shield is high. The staging of the two component grout injection, the grout early age strength properties become key issues in ensuring that the segment ring leaving the TBM tail shield is stable and can support the necessary external loads.Two-component grout is a grout with two components, cementitious grout (component A) and accelerator (component B), commonly adopted for earth pressure balance (EPB) TBM. The grout reaches its thixotropic state in a matter of seconds providing initial support for the segment rings. Manual injection of two component grout to fill the bore annulus was carried out in stages leaving a portion of the segment rings unsupported. Ring stability during TBM advance was provided by a combination of ram thrust and the segment circumferential joint shear connectors.This paper outlines the design considerations such as rock load derivation by probabilistic analysis carried out utilising the software JBlock, 3D finite element analyses using the software Strand7 for ring stability and the testing and back analysis of the shear connector load bearing behaviour. In particular, the actual available capacity of the shear connectors against their published capacity by supplier was discussed.CITATION:Mok, P and Norbert, M, 2014. Tunnel boring machine excavation stability – double shield tunnel boring machine advance with partially grouted annulus, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 51–62 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By W Kendall

Ore sorting has the potential to reduce the feed to wet plants and in the case of complex orebodies that can significantly reduce the water, energy and reagent consumptions and resulting operating costs for the project. The application of ore sorters has sparked renewed interest and application in the precious and base metals mining industry in recent years as a result of the continuing development of new sensing technology and very fast information processing that is making ore sorters applicable to a much wider range of ores and larger scale operations. The application of ore sorters involves a range of trade-off decisions that have economic impact upon the benefits of ores sorting to the project under consideration. This paper will present some typical trade offs to be considered and their impact in a particular project setting. CITATION: Kendall, W, 2018. How economics drive the application of ore sorting, in Proceedings Complex Orebodies Conference 2018, pp 24–27 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

By D Will

RedrossThe Redross orebody averages 1 m wide, has a strike of 50 - 350 m, dips at 55° and has a basalt footwall and an ultramafic hanging wall. The most successful and innovative aspects of mining Redross were:•ore development innovations, 90 per cent of development was split fired with a shanty back profile to enable larger and more productive equipment to be used and resulted in higher development grades, improved project payback time and improved ore recovery;•hand held stoping using a multiple level, bottom up ‘V’ shaped hand held stoping method that allowed mining on multiple levels with hand held productivities between 50 and 90 tonnes per shift;•the use of 1 m cement pillars and 7 m high crown pillars were used to create multiple mining areas that enabled high overall production rates from hand held mining this orebody; and•the use of vertical cement pillars to enable hand held mining of adjacent stopes without leaving ore pillars.MarinersThe Mariners orebody averages 3 m wide, has a strike length of 50 - 250 m and dips at 50° with a basalt footwall and poor ultramafic hanging wall. The most successful innovative ideas of re-opening Mariners were:•Dewatering the existing mine workings utilising ‘oilfield’ technology by installing a long submersible pump in on existing pump rising main. This enabled the mine to be dewatered at rates up to 100l/ sec and helped overcome the 45 to 55 L/s inflows.•Overcoming the technical problems associated with Mining N07 ore blocks which had severely deteriorated from being underwater for five years by using reverse firing techniques to improve extraction rates and reduce dilution.•Mass firing a large mining block in the N08 with minimal void space because of deteriorating ground conditions.•Use of a longhole version of the Redross hand held mining method to achieve 100 per cent extraction of the N09 higher grade lenses.

Mar 21, 2011

By Marshall GA, Dickerson AW

The efficient operation of large haul trucks in large open pit mines requires an economic trade off between the haul route quality, the haul truck payloads and the level of haul truck reliability. This paper describes an investigation into the relation- ship between haul route surface quality and the level of structural reliability of a haul truck main frame. An instrumentation system for unattended recording of data on a haul truck operating normally in a mine and com- puter based analytical procedures were developed and used to identify which road segments contribute significantly to fatigue cracking at various sections of a haul truck main frame. INTRODUCTION In many open pit mines there is exten- sive use of large haul trucks to move over- burden and minerals. In most open pit hard rock mines, both the overburden and mineral ore are moved by large rear dump type haul trucks. Similar haul trucks are also widely used for coal overburden and mine site coal haulage operations in New South Wales, South Australia and Western Australia. Large bottom

Jan 1, 1982

By A Vickerfält, J Huss, J Martinsson

The European Union has listed vanadium (V) as one of the critical raw materials for the transition to a future green society, as stated in the Critical Raw Material Act, written by Grohol and Veeh (2023). In the steelmaking industry based on V-containing iron ore, V is a possible by-product from the slag. A requirement for slags to be suitable for V extraction is a V content preferably above 8 wt per cent as V2O3 and a phosphorus (P) content below 0.1 wt per cent as P2O5. Hence, it is important to keep V in the slag phase while the P is moved to the metal phase during the steelmaking process.

Aug 21, 2024

ADDRESS BY THE PRESIDENT OF THE INSTITUTE (MR. J. G. SYMONS) IN PRESENTING THE AWARD TO ELLIOTT SYLVESTER TIMOTHY O'DRISCOLLTim O'Driscoll comes from a mixture of Irish and Scottish stock. His family on the paternal side settled on land in Western Australia in the middle of the last century. His family on the maternal side were part of the W.A. goldfields scenc, including places such as Kanowna, and the Great Fingal mine, near Cue, where his grandfather lies buried.The combination of land and mining environments may perhaps have contributed to an innate interest in geology shared by Tim and his two brothers, all of whom became geologists.Tim showed an early liking for mathematical and geometric subjects, and in his B.Sc. studies at the University of Western Australia he took a major in mathematics along with geology in 1940.His first job was on the Kalgoorlie Golden Mile, and then at Norseman. After serving as a flying boat navigator in the north and south Pacific theatres in World War II he returned to Kalgoorlie and thence to Broken Hill.

Jan 1, 1977

By A Boeing

Rock-breaker automation and remote operation improves the safety and efficiency of mining operations. This paper presents an overview of the Rocklogic rock-breaker automation system architecture that provides collision avoidance, automated parking and remote operation functionality. The system consists of a distributed computer control system that interfaces with sensors attached to the rock-breaker, the rock-breaker hydraulics and the site infrastructure. We present results of an automated Transmin rock-breaker installed in a production environment at an underground Australian mine site. The system has been in production use for over 900 days, during which there have been no reported collisions and 100 per cent adoption of the remote operation technology. As a result, Rocklogic has significantly improved the safety of rock-breaking operations and reduced the rock-breaking cycle time, thereby improving the site’s overall throughput.CITATION:Boeing, A and Douglas, E, 2014. A remotely operated robotic rock-breaker with collision avoidance for the mining industry, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 131–136 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

By W Liu, S Gao, D Wei, B Cui, Z Guan, Y Shen

Beneficiation of low-grade fine-grained hematite ores becomes increasingly important due to rapid depletion of high quality iron ore resources. However, fine particles, especially ultra-fine particles, make efficient beneficiation of these ores more difficult. Therefore, methods to reduce the influence of fine particles must be considered to achieve better beneficiation performance. Analysis and systematical beneficiation tests were carried out on an ultra-fine-grained hematite ore slime from washing a fine grained hematite ore. Ore particles were found to be presented in loose soil. While some of the ore particles were agglomerated, they were very fine and contained up to 76.5 per cent -0.023 mm material. In this paper, using a single magnetic separation flow sheet with sodium silicate (SS) as a dispersing agent, a concentrate containing 65.05 per cent Fe was obtained at an iron recovery of 68.58 per cent from the hematite ore slime of 56.65 per cent Fe. The single magnetic separation flow sheet was simple and reliable, the agent SS was effective in dispersing ultra-fine particles. The results are believed to be applicable to similar hematite ores.CITATION:Wei, D, Guan, Z, Gao, S, Liu, W, Shen, Y and Cui, B, 2013. Beneficiation study of an ultra-fine-grained hematite ore slime, in Proceedings Iron Ore 2013 , pp 495-500 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By M W. A Asad, E Topal, D S. S Sandanayake

Underground mine planning requires an optimal stope layout as a prerequisite for the definition of an optimal production schedule. The procedure to generate an optimal stope layout considers an orebody model and economic parameters as inputs. It evaluates all possible combinations of mining blocks and creates a set of stopes by satisfying the physical mining and geotechnical constraints. Thus, the procedure is computationally complex, and generating a solution to the problem is a challenge. This paper presents an implementation of a new heuristic algorithm that solves the stope layout problem. In two case studies, the algorithm achieves 11.2 per cent and 22.5 per cent superior solutions to the industrially available maximum value neighbourhood approach.CITATION:Sandanayake, D S S, Topal, E and Asad, M W A, 2014. Implementing a new heuristic approach to the underground mine stope layout problem, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 243–248 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By D Kepert

It is the role of the exploration geologist to create wealth through the discovery, delineation and characterisation of economic mineralisation. This requires a critical depth of geological understanding.Unfortunately, the resource industry is well known for its cyclic nature. Many of the current generation of workers have only ever experienced the boom of the ‘super-cycle’ and are only just discovering the negative side to the business. For the case of the geologist and especially the exploration geologist, the magnitude of peaks and troughs are usually amplified and may become destructive to all parties. During the uptime a healthy stream of exploration good news becomes the staple diet of company releases, in particular those of junior companies attempting to bolster the share price. The geological knowledge and experience gained thus forms a significant and integral part of the value and therefore, future of a company. On the downturn it is often viewed that geologists are a luxury, an optional extra and a burden on the bottom line with companies entering a period of memory loss and myopia.Retention of geological knowledge however remains critical as projects, companies and cycles mature. Beyond exploration per se, this knowledge becomes both fundamental in de-risking and commercialising an asset (through development or divestment) and in positioning the company for cyclic or counter-cyclic opportunities.The growth and retention of this knowledge base is difficult to quantify in terms of direct value but becomes one of a successful resource companies greatest assets. At worst, its loss can lead to millions of investors’ funds wasted on missed opportunities, drilling, or poorly designed plant and mine.But the rocks are around for the longer haul and pay little notice to the vagaries of the scurrying of Man.This paper reflects on some of the authors own observations through 25 years of iron ore exploration, in why it is critical to always rigorously question the prevailing geological (mis)understanding and the technical and commercial benefits which that may bring, and looks forward to the future.CITATION:Kepert, D, 2015. Geology – the affirmative case, in Proceedings Iron Ore 2015, pp 285–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By D Craw, C Smith, C Martin

The Wangaloa coal mine closed in 1989, and an attempt to grow Pinus radiata on quartz-rich overburden dumps was not successful. The site is currently being rehabilitated with re-profiling and native plant establishment. Plants are being established in a range of substrates that consist of variably disaggregated Tertiary coal measure sediments derived from the mine sequence. This material has low organic matter content (typically <10 %), originating from coal fines or carbonaceous sediment. Substrate samples were collected during December 2003 from a range of sites varying in age, slope, and parent material. Nutrient analysis includes nitrate, ammonia, total N, total P, available P and readily exchangeable base cations. Total nitrogen and phosphorus are low on areas of recently disturbed, quartz-rich overburden, with total N =1200 mg/kg, and total P =200 mg/kg. Background forested areas have total N ranging between 2800 - 3300 mg/kg and total P of 420 - 500 mg/kg. Quartz-rich overburden sites contain available nitrogen levels of less than 6 mg/kg, while background forested areas are generally >20 mg/kg. The soils and water runoff are generally acid, with pH down to three. Water samples have been collected from both ground and surface resources on a monthly basis since December 2003. The main lake on the site had pH of 4.6 in 1999, and this remained relatively unchanged when 850 tonnes of lime were added in 2002. However, the lake pH changed to 6.4 within a one month period in 2004, and has fluctuated since that time.

Jan 1, 2004

By D Oliveira

The use of an equivalent continuum for a rock mass is not always suitable for situations where the failure is structurally controlled by discontinuities as in the case of wedges in the tunnel roof. In these instances, discontinuum approaches are usually preferred. Rock joints that are filled with soft infill are likely to be the weakest planes in a rock mass, having a dominant influence on its overall shear behaviour. In this case, the joint material model adopted for the discontinuities should be able to describe important mechanisms, such as asperity sliding and shearing, post-peak behaviour, asperity deformation, and the effect of the soft infilling. The latest version of a soil-infilled joint model is discussed here. It describes more comprehensively than previous models the occurrence of dilation and compression with lateral displacements, and also represents the hardening mechanism related to asperity interference as observed in the laboratory that cannot be readily captured by the existing joint models. An analytical approach for the analysis of rock wedges structurally controlled by soil infilled joints is presented.The analytical approach presented in this paper for assessment of symmetric rock wedges in the roof of a tunnel demonstrates, that the peak shear strength of the joint may not be fully mobilised before detachment of the wedge. The analysis verifi ed that an overestimation of the factor of safety may be observed when an elastic-perfectly-plastic joint model was assumed, whereas the computed maximum factor of safety was considerably less when adopting an appropriate soil-infilled joint model.

Mar 8, 2011

By M Oyarzún

Direct relationships between rock texture and BWi (grindability index) have been established based on geological and metallurgical information supported by optical microscopy observations, gathered from 731 samples.Each recognised rock texture is observed to be related to a certain BWi range and, this texture is also characteristic of distinct lithological subunits (recognisable at mapping scale). Therefore, this relationship may provide an important tool for early milling in situ estimation.Since each textural type is a response to rock formation conditions, the causality of the relationship between BWi and texture is based on such conditions and, particularly, on the interfacial free energy among its components.According to the abovementioned textural features, the greater the free interfacial energy between mineral components, the greater the necessary energy required to break its grain boundaries and, consequently, the greater the necessary energy required for milling.If the textural evidence indicates that the rock was able to adjust the shape and/or size of its components – in a natural tendency of all systems to minimise energy– then the necessary energy required to break its grain boundaries will be lower.

Sep 5, 2011

By D Newton

The Mt Morgan Minesite in Central Queensland has been subject to both underground and surface gold mining operations since the late-1800s. The site is largely unrehabilitated and poor quality surface run-off and subsurface leachate is contaminating the nearby Dee River. The site is dominated by a large open cut, which now stores contaminated surface and subsurface run-off. Three models were used to simulate the complex hydrologic processes occurring at the Mt Morgan Mine: a rainfall-run-off model, a groundwater model and a storage behavioural model. Study results showed that the open cut is filling with water and will soon spill large volumes of highly polluted water to the Dee River on a regular basis if no remedial action is taken. This will result in a three-fold increase in pollutant load to the Dee River. Based on a consideration of water quality and quantity it was concluded that the first priority for future minesite water management should be the prevention of spills from the open cut. Potential management options to achieve this objective included surface rehabilitation, catchment diversions, modification of the pump-back system and controlled releases to the Dee River during floods. However, assessing the relative effectiveness of these measures required a thorough understanding of the complex surface and subsurface hydrology of the site. The results of a 100 year simulation of hydrologic processes revealed that previously favoured management options would be ineffective in preventing spills to the river. On this basis, a continuous treat and release strategy was proposed as the only reliable method of preventing future spills. The results of this study demonstrate that good environmental management decisions must be based on an understanding of the relevant physical processes and consideration of cumulative effects over an appropriate time scale.

Jan 1, 2003

By S J. Tear, L D. Queen

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Frieda River Project is located in the north-west of Papua New Guinea. The target commodities for a bulk mining operation are copper and gold associated with a large felsic porphyry system. The project comprises a series of deposits, with the Horse-Ivaal-Trukai (HIT) being the largest. It also includes the adjacent smaller Koki and Ekwai deposits.Previous resource estimates for the HIT were made using 14 separate mineralised domains based on structure, copper grades, lithology and alteration. H&S Consultants (H&SC) has revisited the deposit and concluded that a simpler methodology could be used for resource estimation without using wireframes as hard domain boundaries. This conclusion is based on reviewing all the available geological data combined with geological and resource experience of porphyry deposits.It is generally acknowledged that porphyry deposits form by diffusion of mineralising fluids through the host lithologies, meaning that sharp boundaries are unlikely unless these fluids encounter specific physical or chemical boundaries. It is important to prepare a comprehensive geological model prior to attempting resource estimation as it forms the framework for the estimates; however, not all geological features may be relevant to the distribution of mineralisation and there can be a tendency to overcomplicate the estimation process by using too many domains. Unless a hard boundary can be identified consistently and unequivocally, it is generally better not to use a boundary in that location.H&SC completed unconstrained models with no top-cutting using both a simple flat search ellipse and a steep search ellipse to generate global resource estimates reported within a predetermined pit shell at a 0.2 per cent copper cut-off. Both outcomes are within 10 per cent for the tonnes, contained copper tonnes and gold ounces compared to the constrained resource estimate. The slight differences are most likely due to the different search strategies, but also indicate the robustness of the unconstrained modelling approach.CITATION:Queen, L D and Tear, S J, 2015. The Frieda kiss – keeping it simple , in Proceedings PACRIM 2015 Congress, pp 361–368 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015