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Geophysical anomalies result from the passage of hydrothermal fluids through rocks. Interpretation of these anomalies, when integrated with available geological and geochemical data, assists the construction of a conceptual model of the original hydrology of the system. The original extent of a geothermal system is often indicated by the distribution of low resistivity argillic clay alteration. Quartz-adularia vein deposits, silica sinters or stockwork (often mineralised) cause local increases in resistivity. Appropriately chosen electrical techniques can therefore be used to help target such structures. Airborne magnetic surveys have also proven useful in New Zealand epithermal exploration, because hydrothermal fluids destroy magnetite causing extensive demagnetisation anomalies. Ground magnetic surveys can sometimes be useful for geological interpretation on a local scale. Positive gravity anomalies may occur as a result of mineral precipitation (silica or calcite) in high porosity host rocks, while negative gravity anomalies can result from hydrothermal fracturing and leaching of relatively dense host rocks. The relative merits of these geophysical techniques as used in the exploration of epithermal mineral prospects are discussed, with particular reference to the Hauraki Goldfield. The preferred method for defining zones of quartz veining/silicification is vector or tensor gradient resistivity. Exploration strategies and technique refinements are suggested as a means of improving the resolution of potentially mineralised target structures, in a more efficient and cost effective manner.

Jan 1, 1993

By D Garcés, M Meléndez, R Castro, E Viera

Enhancing the understanding of gravity flow in caving operations is a key factor in the design, operation and success of caving methods. Consequently, much research has been performed to increase knowledge about gravity flow. Many valuable theories have been gained from different research approaches, which include physical modelling, numerical modelling and a limited number of full-scale tests. Recent advances in technology have allowed Codelco Chile to carry out trials using Smart Markers technology. This technology was used in Esmeralda mine’s Block-2 at El Teniente mine from August 2012 to January 2015. This paper aims to determine the characteristics of the extraction zone and obtain the data that will allow greater understanding of gravity flow for design and draw control purposes.The collected data from recovered markers were analysed using a linear interpolation of both the initial position of the markers and drawbell accumulated drawn tonnage. For each drawpoint in the trial, the regularity or irregularity of flow was analysed based on the recovered markers and the drawn tonnage. Correspondingly, the relationship between flow characteristics and observed fragmentation in drawpoints was analysed. The gravity flow of the Smart Markers revealed that current drawpoint spacing provides the interaction conditions of adjacent flow zones. However, it is possible to increase the drawpoint spacing while allowing caved rock to be extracted from the major and minor apexes.The results of this research also verified that full-scale test data are the predominant factor in the production level design and production control at El Teniente mine.CITATION:Garcés, D, Viera, E, Castro, R and Meléndez, M, 2016. Gravity flow full-scale tests at Esmeralda Mine’s Block-2, El Teniente, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 349–358 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

South Africa has joined the league of other major Western World countries by officially adopting its own code for public reporting of Mineral Resources and Mineral Reserves. The recently published South African Code for Reporting of Mineral Resources and Mineral Reserves (SAMREC Code or Code) (SAIMM 2000) is presented here in its local and global context. The main aspects of the Code are listed and elaborated upon. The Code has been written with the participation of the major South African stakeholders in the field including Government institutions, the legal confraternity and the mining industry. Relevant foreign organisations, such as the Australasian Joint Ore Reserves Committee (JORC) and the United Nations contributed to its compilation, and supported it. The Code thus enjoys endorsement both locally and, to a large extent, overseas. The Code is modelled on, and is 90 per cent compliant with, the Australasian Code for Reporting of Mineral Resources and Ore Reserves (JORC Code) (AusIMM, 1999). The paper also elaborates on the duties and responsibilities of Competent Persons signing off resource and reserve reports and on the new listing requirements of the Johannesburg Securities Exchange (JSE), formerly the Johannesburg Stock Exchange, which has officially adopted the Code.

Jan 1, 2002

Applicaton of Agricultural Residues from Pyrolysis in Flotation of Black Coal

Sep 13, 2010

Some crystal chemical properties of several apatites from Brazilian deposits and occurrences were determined; the samples had different origins (igneous, metamorphic and sedimentary). The aim was to establish relationships to their froth flotabilities behaviour. Detailed X-ray diffraction studies were carried out, to determine precisely the unit cell parameters and the degrees of crystallinity of the apatite samples. A thorough chemical analysis of these minerals was also conducted. Microflotation studies were carried out, using sodium oleate and dodecylammonium chloride as collectors. The crystallinity levels were determined for all samples studied, with the establishment of a crystallinity index, which varied from 10.0 to 4.5, on a normalised scale. A marked dependence was observed between this crystallinity sequence and flotability; for both collectors, flotability dropped drastically for crystallinity indices lower than 8.0. Also, the low crystallinity apatites showed a decrease in floatability, for longer conditioning times.

Jan 1, 1993

Pilot-Scale Study of Deep Cone Thickener for Phosphatic Clay Dewatering

Sep 13, 2010

Fine Gravity Separation in the Reflux Classifier, Exploiting a High Shear Rate, Laminar Flow Mechanism The Reflux Classifier is used in the gravity separation of particles over a broad range of particle sizes. The device consists of a fluidised bed zone, with a system of parallel inclined channels above. The inclined channels provide a significant hydraulic advantage over conventional fluidised beds via the so-called Boycott Effect (Boycott, 1920). This paper describes a new advance in fine gravity separation based on the high shear rate and laminar flow profile that arises when closely spaced inclined channels are deployed. As reported recently (Galvin et al, 2009a), a powerful density based separation mechanism develops from this arrangement, suppressing the effects of particle size. In this paper we focus on two areas, firstly the application of the separator in the laboratory for batch fractionation of particles of varying size and density to determine the grade recovery curve and hence the liberation, and secondly the step change in separation performance achieved on a continuous steady state basis when closely spaced inclined channels are used. The variation in the separation density with particle size decreases significantly, and the Ecarte Probable Error (Ep) remains at low levels over a broad size range.

Sep 13, 2010

The need for the hydraulic transportation of coal in the New South Wales coal industry, both from the coal face to the surface and from the coal mine to the consumer or the port for export, is explained. Details of research projects currently in progress and involving the hydraulic transportation of New South Wales coals are given together with information on the hydraulic transportation of coal in the United States of America. The potential of hydraulic transportation as a viable alternative to the proposed expansion and upgrading of the New South Wales railway system to meet the projected New South Wales coal production to the year 2000 is described.

Jan 1, 1980

An important consideration in any mining operation is waste disposal management. Tailings management at Macraes gold mine allows for the disposal of tailings into fully engineered embankment dams and overburden material to be incorporated as construction material into those embankment dams. This paper outlines the current tailings management practices.

Jan 1, 1992

By A Hekmat, M Fuentes, F Armijo, R Castro, F Rodriguez

Interpreting the behaviour of granular material and simulating the gravity flow are complex processes in cave mining methods. In this paper, a new Cellular Automata based code – FlowSim – is used as a flexible tool to simulate the gravity flow and subsidence zone in block caving mines. The simulation results of the gravity flow model in a real scaled mine as well as a scaled physical model are presented in this study. In this research, FlowSim was first calibrated at a mine, based on the information obtained from smart markers. These markers were located in five points of the second block of the Esmeralda sector, at the El Teniente copper mine, Codelco, Chile. The calibration was performed with the objective of reducing the discrepancy between the extraction zone defined by markers in the mine and FlowSim outputs. Regarding the mine data, FlowSim was calibrated with the minimum error of ten per cent between real and simulated results. Then, the calibrated FlowSim model was used to simulate the flow behaviour of a scaled physical model. This model was constructed in the Block Caving Laboratory of the University of Chile to scale down the same block of the Esmeralda sector with the scale of 1:200. The FlowSim outputs show that this software enables the simulation of the gravity flow of the scaled model with less than five per cent discrepancy in grade and dilution entry to the drawpoints. According to the obtained results, this paper recommends FlowSim as an appropriate tool which can improve the design of production level in block caving and can enhance the prediction of the subsidence zone and dilution entry.CITATION:Castro, R, Hekmat, A, Fuentes, M, Armijo, F and Rodriguez, F, 2016. FlowSim – a versatile flow simulation tool to quantify extraction and design alternatives for block caving, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 645–652 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

BATMINÖ, BATMINEÖ, BATMINDÖ are an abbreviation for Business Analysis Tools for Mining, Mine Evaluation and Mine Design respectively. BATMINP are proprietary tools customised to suit individual client requirements. The first suite of tools provides for analysis and evaluation of open pit mining equipment alternatives and includes fleet selection, fleet sizing and production, productivity and economic outcomes. The models address all mine process activities including drilling, blasting, loading, hauling and auxiliary services. All models are built to provide for simultaneous evaluation of multiple alternatives that are time and condition related. Provision is made for modelling from first principles and/or default or shortcut inputs. Sensitivities to key input parameters are easily performed and consistent logic is applied throughout the process. The models are built to provide key outputs in a format suitable for presentation and documentation. Provision is also made in the models for validation of both inputs and outputs through benchmarking, back analysis and budget comparison. The same models can be used for short interval (12 month) planning and control, medium-term (three to five years) and long-term life-of-mine (LOM) planning. Millions of dollars are spent each year on mining plant and equipment. Decisions that impact on the medium and long-term are made. BATMINP tools have been used to perform studies with good results and in most cases the studies have been validated through back analysis and comparing model outcomes to real data.

Dec 6, 2010

Python Underground Processing Plant Critical Design The use of continuous gravity recovery in combination with a controlled breakage fine crushing and screening system followed by flash flotation has been incorporated into the Python processing plant. This provides miners with a flexible, robust, low cost, low energy pre-concentration process for the recovery of gold and/or heavy minerals. The Python plant incorporates fine crushing utilizing either High Pressure Grinding Rolls or Vertical Shaft Impactors in combination with the InLine Pressure Jig and Flash Flotation to continuously liberate and recover the valuable minerals. The use of these technologies has enabled a narrow, transportable pre-concentration plant to be produced which can easily be installed and operated in underground drifts and tunnels.

Sep 13, 2010

By S M. Aminossadati, R Bagherpour, F Hasheminasab

Mine ventilation is an essential part of underground mining operations used to provide fresh and cool air, as well as to dilute and remove contaminants from the work environment. This paper presents an overview of the ventilation and gas management systems in one of the underground coalmines in Iran: Parvadeh_1 mine. The mine is located in the Tabas coalfield in the South Khorasan province. It is the only fully mechanised mine in Iran utilising the longwall retreat technique. The mine produces 1.1 to 1.3 Mt of coking coal annually. The mine ventilation system currently utilises two 630 kW exhaust surface fans. The gas management system includes surface to in seam (SIS) predrainage boreholes. The underground mine is equipped with an underground gas reticulation pipeline that is connected to a surface plant for the production of methane gas. This study shows that the ventilation and gas management systems of the Parvadeh_1 mine are in line with the standards of Australian underground mines.CITATION:Hasheminasab, F, Aminossadati, S M and Bagherpour, R, 2017. An overview of ventilation and gas management systems in an underground coalmine in Iran, in Proceedings Australian Mine Vent Conference 2017, pp 41–46 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

Grade uncertainty can have a number of important implications for a mining operation. One of the most significant risks in not considering grade uncertainty in planning is the over or under allocation of processing or mining capacity when compared to realised grades. This could lead to wasted capital expenditure or missed opportunities to add value. This paper demonstrates a method that optimises production capacity and mining schedules in the presence of grade uncertainty. Applying this method to the case study of a nickel deposit recommended a reduction in processing capacity, an increase in mining capacity and more extensive utilisation of stockpiles than optimisations completed with traditional methods. As a result, average NPV improvements of between seven per cent and 27 per cent were gained.

Dec 6, 2010

By W J. Rankin

A study was carried out to compare the environmental impacts of a number of process routes for lead and zinc metal production from sulphide ores using Life Cycle Assessment methodology and based on average industry data derived from the literature. The processes investigated were:blast furnace production of lead; Imperial Smelting Process for lead and zinc production; and electrowinning of zinc with the mining and mineral processing stages common to all three routes. The effect of a number of process variables, namely ore grade, fuel source for electricity generation and efficiency of generation, on the environmental impacts was also examined. The environmental impact categories considered in the study were:total (or full cycle) energy consumption; Global Warming Potential (GWP); and Acidification Potential (AP). The results of the study show that when produced separately, zinc production is more than twice as energy intensive as lead production (viz 48 and 20 MJ/kg respectively), however when produced jointly by the Imperial Smelting process, the energy intensity of the two metals is not all that dissimilar (viz 36 and 32 MJ/kg respectively). The metal production and refining stage was found to make the greatest contribution to the overall environmental impacts for all three processes. The study also highlighted the importance of taking a life cycle approach when comparing the environmental impacts of different processes.

Jan 1, 2002

By G C. Sen

All mining and quarrying operations that employ blasting to fragment and move broken ground have a price to pay for æby-productsÆ such as vibration and noise. These æby-productsÆ cannot be eliminated but they can be controlled and modern blasting techniques have improved to the point that excessive environmental restrictions can be adhered to whilst maintaining acceptable production rates and quality. Accurate measurement is the key to control, and as the environmental limits are becoming tighter, the proper way to measure vibrations from blasting operations becomes an integral part of the mining or quarrying operations. The basic vibration monitoring system consists of a primary sensor connected to a data logger and computer software for the analysis of the signal received and recorded. Currently, as with all fields of measurement, much improvement has occurred over the past decade, and electronic devices are much more accurate and reliable. Data analysis has also improved considerably with the computing power that is available to field operatives today. Mounting the primary sensor has been often overlooked in supposed æstandardsÆ with procedures such as double sided tape, resting on a flat surface provided the vibration level is less than a given amount. But if it is worth going to the expense of the monitoring equipment and manpower, surely it is worth a little extra effort to ensure the primary sensor is coupled to the ground effectively. The primary sensor must move with the ground and measure this movement; so if the primary sensor is allowed to move without respect to the ground (ie poor coupling to the ground) then a false record of the physical event will be measured. This scenario can easily be a practical reality if the primary sensor coupling method to the ground is not effective. In this study a number of mounting methods were fabricated and connected to similar data monitors and a series of ænormalÆ production blasts were used as the vibration source. These mounting devices were measured against an in-house procedure (the æstandardÆ) and the relative merits compared. A laboratory investigation was also carried out to look at the physical parameters of the æsoil and their effect on vibration attenuation of the in-house standard method.

Jan 1, 1999

By B Chi, A Mahanta, R A. M Maddever, O Dominguez

BHP Billiton, in collaboration with Sodern and CSIRO, has developed a downhole logging tool for measuring geochemistry in situ. The FastGradeTM 100 (alternatively, FG100), exploits pulsed fast and thermal neutron analysis (PFTNA) to analyse the rock. This method is based on the detection and measurement of characteristic gamma rays emitted from isotopes in the material that become briefly radioactive when they are bombarded with neutrons. The tool outputs raw spectra arising from three types of neutron interaction, namely, inelastic scattering, neutron capture and neutron activation, which occur in successive time-windows (Smith et al, 2015). The spectra contain peaks at specific energies that are characteristic of the different elements interacting with the neutrons, the gamma count of which is related to elemental concentration. BHP Billiton uses in-house data processing software to convert the measured spectra to elemental concentrations.Much work has been done to understand the tool response under a wide variety of environmental and operating conditions, including logging speed, borehole rugosity, the presence of cavities, water etc. Effort has also been directed at understanding and quantifying the current sources of error in our conventional assays due to sample collection, preparation, and laboratory instrumentation in order to use this information as a baseline to compare against the FastGradeTM 100 results.To date, the FastGradeTM 100 primary use has been as a verification tool (JORC, 2012). However, beyond this, it has considerable potential to improve productivity in both exploration and production environments due to its ability to provide geologists with assay results soon after a hole is drilled.This paper presents initial test work and tool performance, including accuracy and precision under various conditions. Results are illustrated by comparing tool measurements to assays from laboratory samples collected from both reverse circulation and diamond-drilled holes.CITATION:Chi, B, Maddever, R A M, Mahanta, A and Dominguez, O, 2017. Near real-time assay with downhole assay tool (FastGrade™ 100), in Proceedings Eighth World Conference on Sampling and Blending , pp 137–144 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

Resources and reserves are critical inputs into the determination of an operating mineÆs financial results and balance sheets, but how well understood is this fact. Do the investors, directors, accountants and geologists/engineers responsible for preparing or relying on relevant aspects of the end results properly understand the inputs and outputs and the associated risks that may be established. The first step is to understand how financial reports are impacted. The most obvious, and best known, impact is in the calculation of depreciation and amortisation charges against long term assets. In addition, however, there is a requirement to regularly determine whether asset book values are impaired û this is nearly always performed globally by the preparation of a discounted cashflow model for a mine which is usually based on a mine life as determined from the resource and reserve statement û the particular driver here is normally the short and long term production plans. A key aspect of the short term production plan is that it would normally not assume that the reserve and resource statement implies consistent grade, stripping ratios, etc. However, outside of the early years of a plan, more generic assumptions of these variables are often made in conjunction with the reserve and resource statement. Depending on the timeframe of the detailed production plans, this can have a large impact on a projectÆs net present value. Other financial balances that may also be impacted include restoration and rehabilitation provisions, retrenchment provisions and deferred or equalisation stripping accounts. The age old question of whether all reserves should be used or whether some or all of the resources should be included for financial reporting purposes has never been adequately resolved. It is our view that there should be no prescriptive answer to this question but judgement of all professionals involved in the process needs to be included. Furthermore, the company needs to be able to support their conclusions with well thought out and appropriate answers. This may not be in line with the approach that certain accounting standard setters may be proposing or taking, and this paper will outline the current status of global requirement and the likely future directions. Whether reserves or resources are utilised, does not change the key requirement that those preparing or using reserve and resource statements need to understand key aspects. For example: geologists/engineers do they know how reserves or resources will be used? have they imparted information on variability of key drivers such as grade or depth or dilution? do they know that major financial/business altering decisions may be made based on the analysis? accountants do they understand where the numbers have been derived from and the assumptions that may have been made in their determination? do they understand the degree of accuracy (or inaccuracy) that may exist particularly with resources)? do they understand the history of resource reconciliations and what it may mean for the future? directors do they understand the processes undertaken by the company to prepare the financial report and the interaction between the geologists/engineers and accountants? do they understand the potential sensitivity of results to the input variables? Financial reporting is extremely reliant on the use of the reserves and resources, however, the geologists/engineers, accountants and directors do not always understand the interactions between themselves which may lead to misleading public reporting. More education and communication between various parties is needed.

Jan 1, 2002

Declining metal prices over the last few years have reduced the number of new metallurgical plants being built and limited opportunities for introducing new processes. However, technological advances are still being made. With increasing economic pressures, the emphasis is now on reducing unit costs by making equipment larger and through use of technologies with lower operating costs. This trend can be seen in the increasing size of grinding mills and flotation cells used in recent plant designs and in the adoption of HPGR crushing as an alternative to SAG milling. Few new technologies achieve widespread introduction until there are clear economic or operational drivers. These might currently include: ò          increasingly stringent environmental standards; ò          availability of exotic materials for equipment construction; ò          increasingly sophisticated instrumentation and control systems; ò          the need to treat increasingly refractory oretypes; and ò          the length of supply routes to many new plants. As a result of these drivers, a number of new and revitalised technologies will get increasing prominence in the design of new operations, such as: ò          use of ultrafine milling equipment such as MIM's Isamill for treatment of refractory gold ore concentrates; ò          use of thiourea as an alternative for cyanide in sensitive locations; ò          novel hydrometallurgical routes for treating base metal ores in remote locations; ò          paste thickening for tailings deposition; and intensive cyanidation of gravity concentrate

Jan 1, 2000

By B Rosemberg, F Lemos, A J. B Dutra

The chemistry of cyanide solutions is complex, this complexity being responsible for the ability to act as complex-forming agents in metal dissolution processes, among them gold and silver. Such ionic species are used in hydrometallurgical processes, in particular in gold extraction and electro-plating. Due to the high toxicity of cyanide, the discard of effluent from processes and/or industries demands rigorous treatment so as to minimise its concentration. Among the conventional chemical treatment of such effluents one can mention SO2/air; biological degradation; oxidation by using hydrogen peroxide; oxidation by sodium hypochlorite, etc. However, the electrolytic recycling process is also promising for cyanide recovery and offers the possibility of recycling it to the aforementioned industrial processes. Such a process does not use additional chemicals but enables direct re-utilisation to the main process aiming at adjusting the cyanide concentration.

Jan 1, 2002