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By Hll J. K, Zhang Y. G

The wear mechanisms of impregnated diamond drill bit matrices are complex and believed to be the key point in solving drill bit self-sharpening problems. A method has been developed to find the change in c,, the wear rate of matrices having different fracture toughness K_ at the increment of drill pressure P. The worn surfaces of specimens were placed under a scanning electron microscope to examine the wear patterns and wear mechanisms at different pressures, and were compared with the worn surface of a practical drill bit. A model is proposed that within a wide range of pressures there exist two different wear mechanisms and three wear regions for cemented car- bide matrix materials. In region one (linear region), at low pressure, the major wear mechanism is plastic deformation in which the preferential wear of the binder phase of the matrix results in the loss of WC, tung- sten carbide particles. Wear rate is controlled by hardness, H as Archard's formula predicts. Wear enters region two and three (non-linear region) simultaneously as pressure is being increased. Consequently, wear transfers to fracture mechanism in which micro-fracture occurs at the root of wear grooves and the material is removed mainly in piece and mass. It has been shown fracture toughness K,, plays a more important role than hard- ness H. It is concluded that for a specific drilling condition, the pressure on the matrix should be carefully controlled and a balance between hard- ness and toughness of the material is essential for a steady drilling Condition.

Jan 1, 1989

By Mudge S. T

Tin mineralisation occurs at Renison Bell, near Zeehan in Tasmania, as a group of cassiterite-bearing massive pyrrhotite bodies in Cambrian sedimentary rocks. Mineralising fluids from the underlying Pine Hill Granite have replaced carbonate rocks with massive sulphides and cassiterite. The discrete blocks of massive pyrrhotite have high density and high magnetic susceptibility contrasts with the comparatively barren country rock. They are strongly remanently magnetised and are excellent geophysical targets. A detailed geophysical model of the mine was created from a database comprising 1:2500 scale geological mapping and geological logs of approximately 4000 drill-cores. The model comprises 93 parallel cross-sections, each 1.5 km long, spaced 20 m apart. Each cross-section is comprised of up to 150 polygons which represent all known individual rock types and orebodies. The magnetic response of the model was computed and the residual between the model and the observed response, measured by a low-level helicopter magnetic survey, revealed several anomalies unaccounted for by the model. Drill testing of these anomalies led to the discovery of several hitherto unknown massive sulphide occurrences. Surface gravity data of the mine and surrounding district were enhanced by applying digital terrain corrections. The corrected Bouguer anomaly revealed a hitherto unknown positive anomaly associated with the ore zones of the Renison mine. The gravity anomaly of the model was also computed. Unfortunately, the limited resolution of the observed data prevented the delineation of ore targets. The terrain-corrected Bouguer gravity data were also used to model the shape of the underlying non-magnetic Pine Hill Granite. A computer inversion method was implemented to build a 3D block model of the granite. Results agreed with previous conventional 3D modelling techniques but yielded improved resolution of the granite form. The project involved development of new computer software to build and edit the large and complex 3D geophysical model of the mine and to compute the model's magnetic and gravity responses. Software was also developed to build and compute the gravity response of a 3D block model of the underlying granite.

Jan 1, 1997

This paper will describe the exploration project which led to the discovery of the La Escondida porphyry copper deposit in northern Chile and will serve as companion paper to the description of the geology of Escondida being presented by J M Ojeda. The author would like to express his appreciation to Robert Hickman, Chairman of Minera Escondida, for permission to present this paper.In July 1978, a proposal was made by J D Lowell to Robert Wheaton, then Exploration Manager of Utah International, that Utah fund a "grass roots" program exploring for porphyry copper deposits in northern Chile. Wheaton expressed interest, and it was agreed that Getty Oil Co also be invited to participate. A joint venture agreement for the Atacama Exploration Project was signed January 1, 1979, between Utah, Getty and Lowell. The project was managed by Lowell who reported to a management committee which through most of the project consisted of Lowell, Francisco Ortiz, Robert Wheaton, Maurice Young, Sigfried Muessig and Louis Rove. Oliver Warin and Jim Bratt participated in the committee in the last phase of the contract. Special thanks are due Louis Rove of Getty and Maurice Young of Utah who made contributions throughout the course of the project. Francisco Ortiz was resident manager through most of the project.

Jan 1, 1990

By K L. Silversides, A Chlingaryan, A Melkumyan

Multiple data sources can be fused to improve boundary modelling in stratified deposits such as the banded iron formation (BIF) hosted deposits in the Pilbara Region of Western Australia. Accurate boundaries are essential to produce high quality geological models. Initial models are based on the widely spaced exploration hole data. This creates a high level of uncertainty in areas between the holes, with different interpretations of the boundary equally probable. Including directional information collected in these holes in the models can reduce the number of possibilities. Including data collected during mining, such as blastholes and bench measurements, can further guide the model. This research demonstrates a Gaussian Processes based method of fusing these disparate data sources to better inform the boundaries. Our results demonstrate that when only exploration points are used the model creates a smooth boundary with minimal variation between the holes. Each additional data source refined the model and added additional detail to the boundary. For the blast data, the new detail projects down to the bench below the current bench to allow for a better prediction before mining commences on that bench.

Mar 22, 2022

Results of blasting trials conducted at Gregory Mine, a large open cut coal mine situated in the Bowen Basin, show that fragmentation was improved or equalled whilst reducing the amount of explosives previously required. This was achieved by a system of deck loading whereby two or more explosive charges, separated by air gaps, were positioned in the blast hole, thereby extending the effective explosive column whilst minimizing the total explosives required. In the three trials to date, a saving of approximately 213 kg of ANFO per blast hole was achieved. This represented an approximate 20% reduc- tion in ANFO requirements.

Jan 1, 1989

By J P. Moodie

Recent trends in flotation technology are briefly reviewed. These show that considerable development has been made as the operators, suppliers and technologists have responded to the challenges of the industry. Most of these advances have been based on empirical and phenomenological methods. There is a considerable opportunity to make further advances through a more fundamental, scientific approach. Some of this work is discussed and, although progress is being made on this front, industrial uptake has been somewhat slow. A number of specific issues facing the industry are discussed.

Jan 1, 2005

Grade control is an important factor in the on-going success of a mining operation. Grade control criteria will vary depending on the commodity being mined. Financial considerations determine the actual grade control criteria at any one mine site. Mining and metallurgical capital and operating costs are ultimately used in ascertaining cut-off grades employed in grade control. The metallurgical characteristics of the ore, and ultimately the equipment selection and design of the plant, are based on samples provided by the exploration geologist. Ore variability is an important factor in designing the process plant. Ore variations, outside of those catered for in the design, as well as large ore changes on a daily basis, will impact on the metallurgical performance, and hence the economics of a mining operation. Therefore good liaison between the grade control geologist and metallurgist will undoubtedly lead to a more consistent, and more profitable mining operation.

Jan 1, 1993

By Nowell SB, Cottrill DA

Host-rock - wallrock major and trace element geochemistry associated with epithermal gold mineralisation in the Hauraki Goldfield of New Zealand is poorly documented, even though rock geochemistry is a recognised tool in exploration. Such responses assist in recognition of the regional scale imprint of fossil hydrothermal activity, and indicate targets for detailed evaluation within these alteration zones.Recent investigation of gold deposits in the Waihi (Gladstone), Golden Cross (Empire), Thames (Waiotahi) and Coromandel (Tokatea) areas indicate enrichments of Au, As and Sb in the andesitic wallrocks hosting mineralisation. Of the other elements examined, Si, K and Rb are enriched, and Na, Ca, and Sr are depleted at all deposits. These trends are best developed in the vicinity of veining. In deposits with clay alteration dominating (Waiotahi and Tokatea) there is also depletion of Mg, Mn, Zn and Cu. Ba and Cr are variably enriched or depleted within different styles of alteration. Base-metal enrichment in the wallrocks is not a feature of Hauraki deposits.

Jan 1, 1990

I In an optical microscope, mild attack by cyanide solutions on various minerals can be observed by means of colour changes as well as etching patterns. However, the mineral may not be identifiable due to the coloured film. In some cases, a transfer algorithm between mechanical stages enables the surface-altered mineral to be identified in the SEM. A more severe attack may not be so informative, as it is not known whether the mineral attacked has been completely dissolved away. The leaching behaviour of some common minerals is described.

Jan 1, 1991

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

The Mt Leyshon Gold Mine is located 30 kilometres south of Charters Towers in Northern Queensland. The current open cut mine has been in operation since 1986. In 1992 a feasibility study was completed that recommended an increase in production to over 240 000 ounces of gold per year. This proposal required an upgrade of the processing plant to five million tonnes per year, and an enlarged mining fleet to provide additional ore, and to meet the increased waste removal requirements. The implementation of the mine expansion program during 1993 required the Life of Mine plan to be extensively revised. This required the assessment and management of potential risks associated with the mine design. The updated geological model using the 1992 drilling results along with the actual contract mining and processing costs were used to establish a series of nested optimised pit shells. The total and incremental quantities and costs were then analysed to determine a suitable pit perimeter. The pit and phase plans were then created and used to devise a staged development plan. The block layout plans for each bench were then established from which a detailed life of mine production schedule was created.

Jan 1, 1994

By P Grouhel

In the recent years several new blasting technologies have come into use in surface mines. Electronic initiation, low-density emulsion explosives and modelling software are in regular use throughout the world. In Australia, these new technologies have achieved significant application, largely in open cut coal mines where more than 20 per cent of blasting is now conducted with electronic initiation systems. These new techniques have contributed to the vast improvement in blasting outcomes evidenced by increased recovery of saleable product and faster excavation rates. In large surface mines, OricaÆs unique combination of electronic initiation systems, bulk emulsion explosives and modelling software can be harnessed to target critical value outcomes. This includes targeting better fragmentation, increased ore uncovery rates and better wall stability û all adding to improved mining operation profitability. Orica Mining Services have combined these technologies into a set of offerings called Blast Based Services (BBSÖ). The paper describes applications of these new technologies and possible benefits in large surface mines.

Jan 1, 2007

By F Shi, G Ballantyne, K Runge

There has been minimal innovation in the methods used to process an ore over the last 50 years. Productivity increases have largely resulted in increased equipment size without implementation of parallel improvements in technology. Complex orebodies of the future will need mining operations to adopt new technologies and techniques to make future ore treatment economically viable. Three emerging technologies, namely high voltage pulse (HVP) pretreatment, fine screening and the HydroFloat<sub>TM</sub> coarse particle flotation cell will be presented in this paper and the potential benefits that may result if they are adopted in mineral processing circuits will be outlined. The barriers that must be overcome before they can be adopted by industry with confidence will also be discussed. CITATION: Runge, K, Shi, F and Ballantyne, G, 2018. New technologies that will potentially enable processing of complex orebodies, in Proceedings Complex Orebodies Conference 2018, pp 126–129 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

By Wilkinson RDB, Van Der Meer FP

In order to overcome the statistical limitations imposed by the need to recover density tracers by hand, magnetic density tracers were developed to determine the efficiency of dense medium separators treating porous materials. The tracers were manufactured by extrusion of polypropylene ferrosilicon mixtures and subsequently coated with a distinctive paint to allow hand sorting according to density. Fifteen tracer batches were manufactured in the range 1.61 - 1.94 g/cm3. The tracer densities were determined by a hydrostatic method. The tracer method was applied to the dense medium separation of a Moroccan oil shale in a pilot scale Dyna Whirlpool separator. For each test, about 20,000 tracers were added with the plant feed and subsequently recovered from the products with a dry low intensity magnetic separator. The Tromp curve determined by conventional heavy liquid analysis was displaced towards lower densities compared with that determined by tracers, indicating that the porous shale particles absorb heavy liquid. It is concluded that for porous materials like oil shale and coal, the tracer method gives the most accurate results. In pilot scale testwork the tracer method is also much faster than the conventional heavy liquid analysis, as rather large samples have to be processed by the latter method to ensure Representativeness.

Jan 1, 1987

Over the 20 years to 1990 the Australian mining industry, presently worth some $A60 billion, generated a negative real rate of return (McDonald, 1992); not surprisingly under-performing the returns from bonds and industrial equities. Over this same period more than $A70 billion was invested in expanding the Australian mineral industry.

Jan 1, 1993

It is difficult with inadvertent explosions to establish fundamental data, especially of original dust, of pressure, temperature etc. and of ventilation oscillations, as exposed personnel rarely survive. Retrospective data from explosions must be derived from damage, from fatalities, from ventilation analyses, from analyses of dusts and other indications of temp- erature and duration of temperature. The five disastrous explosions selected for analysis provide examples of what data can be established as to the cause and extent of explosions. Such information is required for legal etc., inquiries subsequent to explosions, but most importantly to give the best guidance for avoidance of possibility of further Disasters.

Jan 1, 1981

By Gallet M, Watsford R. M S

The 1989 feasibility study of the chessy, france, copper, zinc, pyrite and barite orebody was based upon a classical flowsheet. The flowsheet included, three stages of crushing, conventional rod and ball mill grinding in series, and sequential flotation of four products utilising conventional mechanical flotation cells. To improve the profitability of the project the partners commenced a search for ways to reduce the projected capital and operating costs of the proposed development. This paper presents the improvements in the projected capital and operating costs as a result of design and concept changes. The major changes included: ò the simplification of the crushing section with the adoption of semi autogenous grinding (SAG) milling of primary crushed ore. ò the deferral of pyrite and barite flotation circuits until market conditions were positive. ò the simplification of the flotation circuit by the use of column flotation cells for combined rougher/cleaner duty. ò the purchase of second hand equipment. The result of these changes was to reduce the capital cost estimate of the plant from US$ 21 million to US$ 11 million and operating cost estimates from US$ 18.90 to US$ 13.60 per tonne of ore for a decrease of approximately ten per cent in potential revenues.

Jan 1, 1991

By J Brisebois

The Wisemans Creek derelict mine site is located in native forest approximately 150 km west of Sydney. Mean annual rainfall at Bathurst, 20 km to the north, is 634 mm and reasonably distributed throughout the year, with slightly more rain falling in the summer months. Evaporation is 1350 mm per annum and considerably exceeds rainfall in all but the winter months (May to August). This results in a water deficit for much of the year. Groundwater is relatively deep, as it has not been intercepted in the shallow open cut workings. Investigation of the groundwater regime was beyond the scope of the current study. Mining has taken place on the site for almost 100 years, during which copper, talc and gold have been sequentially extracted from surface and shallow underground workings. The site is now characterised by the presence of small open pits, unprotected shafts and adits, mullock heaps and an unconfined tailing deposit from a small cyanidation plant. From a distance, the mine area is visible because of two distinct steep bare slopes below the relatively small mine workings and mullock heaps. The mining area was characterised in terms of its environmental, safety and heritage issues. Mullock from the early copper mining was found to be acid forming and leachate from this, combined with clearing of timber, has most likely resulted in death of vegetation below the heaps. The mullock also contains elevated concentrations of heavy metals. The gold tailing is apparently benign and not acid forming, although there are indications of oxidation and acid formation in the derelict gold open cut. Oxidation of the acid forming mullock still appears to be taking place even after being exposed to the atmosphere for at least 50 years, resulting in continued contamination of the slopes below the heaps with heavy metals. The concentrations of metals decreases with distance below the mullock heaps and also is confined to the ground surface the further away from the mullock, providing further evidence to support the theory that the mullock is the source of contamination. Despite this continuing contamination, its spread beyond the immediate mining area appears to have been limited because of the relatively dry climate, with only intermittent rainfall and stream flows. Irregular storm flows in the nearby creek could also have washed any contaminated soil some distance from the site and beyond the area investigated in this study. Remediation of the site and restoration of vegetation on the bare slopes will therefore depend on elimination of the source of acid and metals. Options for remediation, focussing on minimising cost by retaining the materials on or close to the site, are identified. The volume of the open cuts would appear to be close to that required for burial of the acid-forming mullock, thereby removing the source of surface contamination while keeping it above the groundwater table. However, implementation of this remediation plan will depend on the availability of funds to undertake the work through the New South Wales GovernmentÆs Derelict Mines Program.

Jan 1, 2003

Determining the environmental consequences of green field projects is becoming an increasingly important component of new projects. Feasibility studies are regarded by potential investors as incomplete if a comprehensive Environmental Impact Assessment (EIA) has not been completed. These EIAÆs need to meet various local and international requirements in order to achieve bankability. Heavy mineral mining projects are often located in ecological sensitive coastal zones, and bring with them a suite of social impacts in the mainly developing countries within which they are usually located. This paper draws on experience gained in undertaking EIAÆs for heavy mineral mining projects in Kenya, Mozambique and South Africa, and uses these case studies to identify potential pitfalls. Important lessons include the need to initiate the EIA process as early as possible in the project, in order to develop management systems to mitigate the environmental impacts of exploration. Close and on-going consultation with affected communities is also seen to be critical to the success of the EIA. Proactive participation on the part of the environmental consultants with the project team and all interested and affected parties (IAPs) is important. An EIA commissioned later in project planning makes it difficult for the EIA to contribute in a positive manner to the project. Early engagement with environmental consultants allows the environmental assessment to develop from a report to an actual process, and to become fully integrated with project planning. The proviso is that an initial æfatal flawÆ assessment is required to identify any potential æshow stoppersÆ, in order to meet one of the important objectives of EIA, namely an assessment of whether or not the proposed project is the preferred development intervention in the study area. For more controversial proposals this may require the commissioning of a Strategic Environmental Assessment (SEA), which circumvents some of the limitations of the project level EIA. Whilst confidentiality is a constraint to full disclosure, an open participatory approach to public consultation is essential to add credibility to the EIA process and to gain, at least, the acceptance of the process from the majority of IAPs. Full disclosure is encouraged by organisations such as the International Finance Corporation, who acknowledge that good public consultation costs a lot of money, but bad public consultation costs a lot more! An open approach to disclosure presents understandable difficulties for proponents, as they are required to give up some of their control over the project, and to trust the social scientists engaged in the process. However, independence in the EIA process is critical to its success. This paper will highlight these and other issues by drawing on five case studies to identify lessons learnt, and explore the above themes in more detail.

Jan 1, 2001

Gold mineralisation at Wapolu lies within an exposed arcuate zone at the decollement contact between a basement dome of high grade metamorphics and an overlying ophiolite sequence. This contact was originally a thrust fault which has since become a decollement zone for gravity sliding in association with basement doming. Hydrothermal models for the gold mineralisation postulate an epithermal system in which fluids were channelled up the decollement with boiling of those fluids causing hydrothermal brecciation and subsequent gold deposition. The alteration assemblages, fluid inclusion data and geochemistry indicate that the upper levels of the system are exposed.

Jan 1, 1987