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By L Q. Amorim

The mining district of the Quadrilátero Ferrífero (QF) in southeastern Brazil contributes to 70 per cent of the Brazilian iron ore production, which reached 370 Mt in 2010. Traditionally, four iron ore types were mined in the QF region:1. soft haematite,2. hard haematite,3. friable ‘itabirite’ (the Brazilian name for metamorphosed banded iron formation), and4. canga (an indurated iron-rich crust).With the exception of the hard haematite, these categories derive from supergene enrichment of the Paleoproterozoic Cauê Itabirite. High current iron ore demand means that the QF high grade supergene ores will be depleted in a few decades. Consequently, several mining projects are being developed to exploit unenriched, fresh itabirite. Among them, the Mineração Usiminas Serra Azul project in northwestern QF is one of the most advanced. Four major itabirite types occur in the QF region:1. siliceous (or standard),2. dolomitic,3. amphibolitic, and4. magnetitic.The dominant type in Serra Azul region is a fresh siliceous itabirite, composed essentially of haematite, martite and quartz that averages 36 per cent Fe (51.5 per cent Fe2O3) and 47 per cent SiO2. The second type, the magnetitic itabirite, consisting of magnetite, martite, gruneritecummingtonite, quartz, dolomite, stilpnomelane, and subordinate haematite, is typically a strongly magnetic greenish banded iron formation with the iron grade varying between 25 and 35 per cent. Chemically, it differs from the siliceous itabirite due to the relatively high CaO, MgO and, consequently, high LOI contents. Together with supergene ores, fresh itabirites have been included in the ore reserves of the Serra Azul project. We anticipate that all the four types of fresh itabirite will be incorporated as ore in the QF region, causing a huge increase on the iron ore resources of the district, and representing enormous environmental and technological challenges for the local iron ore industry.

Jul 11, 2011

By L R. Sousa, M He

Rock burst is common in deep underground excavations and is characterised by a violent ejection of block rocks from excavation walls. It is critical to understand the phenomenon of rock burst and particularly the failure mechanism. Laboratory experiments are one of the ways. For that purpose, a rock burst laboratory test system was developed at the State Key Laboratory for Geomechanics and Deep Underground Engineering at the China University of Mining and Technology, Beijing. A true triaxial test system, designated the Deep Underground Rock Burst Analogue Test Machine, was developed, which can transfer a stress state from three-direction-compression on six surfaces to the compression on five surfaces with one set free. The rock burst experimental system comprises an acquisition of acoustic emission signals, a high-speed recording in order to accurately record the kinetic characteristics of rock fragments ejected during a rock burst event and the possibility of infrared thermography showing the surface temperature of the samples. In this paper, analyses of typical results from rock burst tests are presented with a description of the obtained results. The mechanisms of rock burst are illustrated, and a rock burst classification is proposed based on these laboratory tests. For the control of rock burst, the constant resistance, large deformation (CRLD) bolt or anchor is presented for accommodating the large displacement of surrounding rock masses and absorbing the impact of the sudden release of rock burst while outputting a constant resistant force in response to the external load. The CRLD bolt or anchor has had practical applications in underground mines. Finally, in situ tests performed in a tunnel at Qingshui coalmine, China, are analysed in detail.CITATION:He, M and Sousa, L R, 2014. Experiments on rock burst and its control, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 19–32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By Mitchell I, Gelfi P, Dunne R, Pyper R

Dump leaching at Teller in its present form began in the fourth quarter of 1988 as an adjunct to milling operations. Initial plans called for a dedicated dump leach facility capable of processing ore at an annual rate of 2.0 million tonnes. Construction of a dump leach pad, collection and process ponds, carbon adsorption system, elution plant as well as reagent addition and ancillary facilities was initiated in mid-1988. During the course of construction, additional reserves were proven. As a result, design throughput was increased to 4.0 Mtpa. Leach pad capacity and solution supply systems were upgraded to handle the larger throughput. However, the carbon adsorption/elution facilities were not upgraded due to space limitations. During 1990 it was decided to expand the dump leach operation to 6.0 Mtpa. Construction of a second leach pad was required which was initiated in early-1991. Plans were again upgraded prior to completion to a target annual throughput of 10.0 million tonnes was. A further two leach pads have been constructed. The first of these being completed during the latter part of 1992. Construction of the latest and largest pad commenced early in 1994.

Jan 1, 1994

Over the longer term, the adoption of new technology is an essential component in the endless tasks of reducing mining costs, improving safety and improving environmental standards. However the choice of which of the many available new technologies to adopt and which not to adopt is not easy and the price of mistakes can be very high. The most important issue for mine developers faced with making such choices is knowing whether or not a new technology has been developed to the stage where the timing is right for its adoption. A system for categorising new mining technologies is provided. It provides a basis for more easily reaching common understandings about various new technologies and the background information supplied provides an understanding of what it takes to get new technologies to the proven stage and the risks of never getting there. Wherever possible, new full-scale mine developments should not rely on unproven technologies. Approaches to handling situations where a proposed new mine development is not feasible on the basis of proven technologies are also provided. If any commitment to the use of unproven technologies is made, a guarantee of high quality development support from the supplier of that technology is essential. Several case studies of successful and unsuccessful new technology development programs at BHP are Provided.

Jan 1, 1997

By M Lund

Due to operational and regulatory practicalities, pit lakes will continue to be legacies of many open cut mining lease relinquishments. Unplanned or inappropriate management of these significant geographical features may lead to a short-term liability to all stakeholders during mining operations, or to ongoing liability to the local community and environment following lease relinquishment. However, the potential for pit lakes to provide benefit to companies, communities and the environment is frequently unrecognised and yet may be a vital contribution to the sustainability of the open cut mining industry. Improved remediation technologies are offering more avenues for pit lake end use than ever before, at the same time mining companies, local communities and regulatory authorities are also becoming more aware of the benefit these water resources have to offer. Sustainable pit lake management aims to better minimise short- and long-term pit lake liabilities, and yet also to maximise short- and long-term pit lake opportunities as well.

Jan 1, 2006

By Bevan JE

The US Bureau of Mines is conducting research to improve the health and safety for underground coal miners, and the efficiency of the mining systems that are used. In 1986, the Bureau began a major research effort on the technology for computer-assisted mining systems for underground coal mines. The initial target was technology for continuous mining machines that would allow them to extract coal by computer-assisted operation. Technology areas being investigated include guidance systems, machine condition systems, computer systems, machine control, human-machine interfaces and planning. In each of these areas, individual system development has progressed to where underground testing of these systems will begin in 1991.In addition to coal extraction, the Bureau has also begun research for the development of technology for computer-assisted roof bolting. The Bureau is developing technology for a "smart" roof bolter that would be able to sense and analyze strata conditions to determine the requirements to provide a competent roof. The system would determine the location of the hole, drill the hole to length, and select and install the appropriate bolt.

Jan 1, 1991

By Valery W, Morrell S, Loughlin P, O&apos

Traditionally, blasts in mining operations are designed to prepare the in situ rock mass for excavation and transport without much consideration being given to the downstream comminution processes. Blasting is in fact the first step in a chain

Jan 1, 1998

Major discrepancies between mine estimates and estimates from plant metallurgical balances are a common problem in many gold and base metals mines around the world. Many existing practices are based on practical protocols that often fall short

Jan 1, 1998

By I Taylor, M Nugus, C Gordon

Resource estimation and selective mining of structurally complex, high nugget orebodies presents a major challenge to the Mine Geologist. At the Golden Pig BIF-hosted gold deposit in Western Australia, an estimation method has been developed that replaces an assay-based resource estimate with one based on mineralisation intensity. Subjective coding of the mineralisation intensity has a more robust connection to local grade than drillhole assays. Indicator variograms of the five mineralisation codes are well structured with anisotropy directions similar to observed structural controls. The proportion of each mineralisation code is estimated and a weighted average of the average grade of each code calculated for a block. Initial validation has shown that the model is a good predictor of the mineralisation intensity, and the application of appropriate local average grade for each mineralisation code gives a reliable block grade estimate.

Jan 1, 2003

By G J. Butler

Since 2005 BHP Billiton Iron Ore has been working with the consulting company Runge to implement the software XPAC Advanced Destination Scheduler (ADS) in life-of-mine studies. The Mt Whaleback mine, being the single biggest open cut iron ore mine in the world, presents some special challenges in scheduling. The biggest challenge has been the slow run time and difficulty in targeting all ore and waste requirements. The high waste to ore strip ratio means that much of the cost of mining is tied up in waste dumping. It is therefore very important to schedule waste efficiently. At Mt Whaleback there is an additional challenge of managing two types of waste: inert and environmentally sensitive pyritic material. This paper shows how the XPAC destination scheduler is configured to achieve efficient and repeatable waste scheduling results at the Mt Whaleback mine. It also discusses proposed improvements to the process. The overall ore and waste schedule is configured to target mining parameters, crusher feed and grades. The schedule is run in two stages. The first stage is ore mining. The waste that needs to be mined is locked in a sequence. The second stage is the waste scheduling. The waste destination scheduler uses three inputs: source waste parcels locked in a sequence, a haul road and a waste dump block model. The process involves setting some rules for dump progression and haul path selection. These can be validated. The schedule is then run to target the shortest travel time. The results of scheduling are graphical and numeric and can be transferred into many different formats for reporting. The graphical result shows face positions in time that can be used for detailed dump design. The numeric results are used to estimate truck fleet size, fuel consumption, labour and equipment financials. The process has been successful in reducing the project time line, increasing the ability to do more scenarios and increasing schedule accuracy, transferability and repeatability.

Jan 1, 2007

By Baafi EY, Appiah HK

The Prestea Goldfields Ltd of Ghana, West Africa has produced over 170 t of gold with average grade of 11 g/t since 1912. The deposits occur in a wide shear zone which closely follow the Birimian-Tarkwaian contact. Both the Birimian and Tarkwaian systems are of Precambrian age. Underground exploration is carried out to delineate ore bodies by means of AX size diamond drilling at 50 m sampling intervals. After the orebody has been delineated, development work is carried out by exposing the gold reef. Channel sampling is then carried out at about 3 m intervals in both the stope and stope drives. A channel sample length is commonly 0.6 in, but may vary depending on physical characteristics of the reef. The values of channel samples are linearly combined to obtain the average reef or slope values and/or widths of the exposed sections. The sampling practice and methods of improving the efficacy of sampling at the mine are described.

Jan 1, 1976

By Biswas AK, Hayes P

During the reduction of iron oxide pellets in the blast furnace it has been found that catastrophic swelling (up to 300% volume increase) can occur. Although the burden preparation conditions can be designed to avoid this phenomenon the exact reason and mechanism of the swelling has yet to be clearly identified. Swelling of the burden is undesirable since it reduces the interparticulate voidage in the blast furnace thus reducing gas flow through the stack resulting in low production rates of iron. The present study differs significantly from previous experiments in that reduction is carried out on single crystals of wustite thus the problems of control of gas composition and specimen preparation are minimised. The microstructures formed on reduction have been examined by optical and scanning microscopy. Pure wustite and wustite doped with various levels of CaO have been examined after reduction in controlled CO-CO 2 gas mixtures at 968¦C. The catastrophic swelling on reduction coincides with the formation of an unusually open iron structure in which the iron appears as whiskers or needles as previously reported. The spacing and thickness of the needles are shown to vary with impurity content and gas composition. Metallographic examination has shown in addition, however, that the whiskers do not necessarily constitute the only product form of the iron produced and in CaO containing wustites with less than - 2% CaO there is a transition from needle growth to porous growth of iron. Thus the % swelling of the oxide particles is dependent on the initial size of the oxide grains. Samples of FeO - 10% CaO exhibited a previously unreported product inorphology associated with the nucleation of 2CaO.Fe203.

Jan 1, 1980

By P A. Dowd

This paper describes an integrated approach to the evaluation of ore loss and ore dilution via geostatistical simulation of in situ geology and grade characteristics, simulation of blasting mechanisms and simulation of loading from a blast muck pile. The approach is demonstrated on a case study. The sequential Gaussian method is used to simulate in situ bench grades on the scale of the smallest selectable volume within a blast muck pile. The simulated grades of these component volumes are interpreted as the reality that would be available with exhaustive sampling. The simulated bench is subjected to a blast simulator, based on the SCRAMBLE model, which effectively moves each of the component model volumes to its final resting place in the blast muck pile. Ore/waste delineation and selective loading processes are applied to the simulated muck pile to determine the degree of selectivity that can be achieved by various sizes of loader and types of loading and to quantify ore dilution and ore loss. An in situ model representing the reality of knowing only the data and information that are available from specific grade control drilling and sampling grids is obtained by sampling the geostatistically simulated model on a specified grid. The volumes comprising the in situ model are then populated by estimates based only on the data and from the specified grade control drilling and sampling grids. Different drilling and sampling grids are used to generate different models, each reflecting the levels of data and information available. Selectivity is assessed as a function of the drilling and sampling grids as well as the size and type of loader. Performance is assessed against the ideal selectivity that could be achieved on the perfect knowledge model comprising the simulated values of each component volume. Costs, prices and financial criteria enable an optimal selection of the grade control drilling grid, size of loader, type of loading and blast design.

Jan 1, 2004

By I Minniakhmetov, J Ashford

Orebodies constitute naturally occurring, commonly highly variable concentrations of minerals in the earth’s crust formed through varying and highly unpredictable processes. Orebody knowledge is a core foundation of a mining company’s asset base underpinning all decisions about Mineral Resource and Ore Reserves, future production, development and ultimately the profitability and competitiveness of a mining enterprise. The decision to invest in a mineral project is usually based upon a techno-economic evaluation of the project and having clear approval pathways to gain local community support and address social and environmental impacts. The main objective of the techno-economic evaluation is to determine the optimum development sequence for the particular orebody in question and to estimate the economic viability of the project and the future return on investment to its stakeholders, balancing the inherent value of the mineral in the ground against the costs of development and market pricing. With the exception of market-driven commodity prices, virtually all revenue and cost estimates fundamentally stem from the understanding and subsequent modelling of the orebody. A reliable estimate of the ore deposit grade and other geological value-drivers is the foundation upon which the business case for future mine development and operation is intricately dependent. Orebody knowledge is, therefore, the fundamental driver of the mineral project cycle, influencing the progression of studies and consequently, the resource company’s ability to declare Exploration Results, Mineral Resources or Ore Reserves which govern the source and cost of funding available to the project. Drilling provides a ‘vector’ to the true nature of the orebody and effectively buys time to manage the technical risk associated with the orebody. Despite its perceived high cost, in both time and money terms, drilling is the only available technology for acquiring the necessary orebody knowledge to support technical and economic studies and to minimise orebody-driven cash flow uncertainty and volatility. However, like all costs, pressure to minimise drilling budgets is ubiquitous across the minerals industry. Paired with inappropriate key performance indicators, drilling is often regarded as a cost to be minimised, rather than an investment to be optimised. Furthermore, as future deposits get deeper and more complex, the collection of orebody knowledge is increasingly on the critical path for project development. The increasing cost of data collection pertaining to these deposits increases the temptation to minimise orebody knowledge gathering at the cost of long-term value as the reduction or postponement of drilling results in greater orebody knowledge risk at all stages of the value chain. Indeed the true cost of the decision to drill less is rarely known until the mine is in operation, well after the mine project evaluation team has moved on. This paper aims to promote orebody knowledge as the fundamental source of endogenous project financial risk and, consequently, its critical importance in project financial evaluation. Furthermore, the report documents experimental research into the development of an econometric model for valuing orebody knowledge. Using the density of drilling data as a proxy measure of orebody knowledge, the proposed approach integrates well-established stochastic grade modelling techniques with the mathematical mechanics of Decoupled Net Present Value (DNPV) which, combined with stochastic grade modelling (conditional simulation), lends itself to the financial International Mining Geology Conference 2022 | Brisbane, Australia and Online | 22–23 March 2022 3 assessment of orebody knowledge risk. Based on this approach, a metric is formulated, representing the minimum value of the orebody knowledge added by additional drilling

Mar 22, 2022

By J F. C L Costa, J C. Koppe, C Diedrich

Currently mineral resources evaluation is firstly expressed in terms of volume. Next the resources are transformed into tonnes by using an average bulk density applied to the whole deposit or, in some other circumstances, various different densities to distinct geological domains. Previous work in uranium, copper and nickel deposits used linear correlation between grades and bulk density to derive the density. Geophysics methods are also another good way to obtain density indirectly.These approaches do not take into account that two samples with the same grade but with different bulk densities can characterise different sample supports, leading to severe bias in grade and tonne estimates. It is important that the systematic measurements of bulk density are included into the estimation process, particularly when density is not correlated with the grades. Additionally, the extra time and costs involved in obtaining the bulk density data have made the mining industry disregard it.This study reports the impact in resource estimates by using a methodology that includes the bulk density variability. It involves the determination of a variability model for the bulk density and another model for the composite that was weighted by density as well as by its length. Next, these variables are estimated by kriging and the final grade estimates are obtained. The tonnages are obtained with the bulk density estimates. The conventional methodology was also applied and both estimates are compared to the reconciliation data from a major copper deposit. The results show a significant difference between the tonnage and grade estimates obtained from these two methodologies.The results show that considering density variability when compositing leads to a more accurate methodology resulting in better grade and tonnage estimates locally and globally.

Sep 26, 2011

By Tarvainen M, Mattila O

Outokumpu Oy has systematically developed the automation of mineral flotation covering the technology of both new devices and control methods, and as a practical result of this effort currently produces two on-stream X-ray analyzers. The Courier 300 system basing on conven- tional X-ray technology is applied to complex or large processes. The newer Minexan 202 dis- tributed probe system based on radioisotope technology is developed mainly for simple or small scale applications. In this paper aspects and experiences of these analyzer systems and their applications for flotation control are discussed with particular reference to the role of the computer

Jan 1, 1977

By Bluhm S. J, Feio L, Ramsden R

A new mining area at the Vaal Reefs gold mine is to have a shaft. system which will extend to a depth of 4 200 m and will require 130 MW of cooling. A novel feature of the proposed cooling system is a large underground air cooling installation in which an ice slurry is sprayed into the ventilation air. The design of the ice slurry bulk air cooler, in the form of counter.flow cooling towers, is discussed. Comparative thermal tests with cold water and ice slurries (with ice mass fractions up to 22 per cent), were carried out in a 5 m high test tower. The presence of the ice in the water spray increases the resistance to heat flow and reduces the overall thermal characteristics of the air cooler by 8 per cent. Notwithstanding this, the use of ice slurries is indeed beneficial in terms of overall costs. It is concluded that a 25 MW air cooler should use 410 kg/s of ice slurry with a 10 per cent ice mass fraction to cool 550 kg/s of air which is 75 per cent of the total air flow rate.

Jan 1, 1988

By Singh TN

Rampura-Agucha Zinc-Lead deposit is unique as it is reported for the first time in the gneissic terrain with a rich oregrade quality of early to middle Proterozoic of Bhilwara supracrustal belt in the Precambrian of Northwest India. These sulphide ores are mostly confined to the graphite bearing Quartzofelspathic gneisses with intermittent bands of Calc-Silicate granofels and amphibolite. The ore and country rock mineralogy and their textural features are indicative of highly metamorphosed deposit and further the presence of marmatite and monoclinic phyrrhotite revealed high temperature environment of deposition.The present paper deals with some of the ideas about the ore genesis and petrographics of the associated rocks for Rampura-Agucha Zinc-Lead deposits of Bhilwara District (Rajasthan).

Jan 1, 1990

The Northland Peninsula of northern North Island, New Zealand contains a complex and diverse record of volcanism which reflects rapid tectonic changes during the late Cenozoic. The main volcanic associations observed on the peninsula are late Cretaceous- early oceanic crust obducted onto Northland at the end of the Oligocene, Miocene arc-type rocks and Pliocene-Quaternary intraplate basalts. This sucession of volcanic successions can be related to tectonic convergence developing into subduction and followed by a an environment of tectonic tension. While the volcanic activity is ultimately linked to specific tectonic regimes, because of rapid change magmatism was decoupled from the specific tectonic event. This decoupling of magmatism and tectonism appears to be a feature of the zones of plate interaction in the southwest Pacific region.

Jan 1, 1990

This paper presents a new idea in field data collection for geological and scientific data. The computer keyboard has been replaced by a barcode wand driving a spreadsheet style editor. To use the full capabilities of computer hardware currently available, geotechnical and geological data can be entered and validated in the field, in a structured format, for later transfer into modem geological modelling databases. An example, using a geotechnical borehole log, explains the principles discussed. The generic nature of the Datcol system is illustrated by the application developed using the Norwegian Geotechnical Institute Rock Mass Classification system. A brief description of a modem spatial relational database is also given with particular reference to underground engineering.

Jan 1, 1993