Search Documents

During the past 18 months a rock mechanics project has been in operation at Renison Limited. The project was established to identify and investigate key problem areas that would affect future production at the Renison mine. An in-house approach was adopted, using shall compact equignent, to investigate ground behaviour. Information on the rock stress field was considered to be particularly important for an understanding of ground behaviour. A high horizontal stress component exists, which enables large flat dipping spans of hanging wall to be opened up, with support being provided by post pillars. The amount of support provided by these post pillars has been found to be low.

Jan 1, 1982

By Kershaw M. G, Maughan R. C A

A process for eliminating nickel from electrolytic zinc plant solutions by precipita- tion with dimethylglyoxime (DMG) was developed to enable the Electrolytic Zinc Company of Australasia Limited (EZ) to treat nickel-bearing zinc dust precipitates. These precipitates are leached to recover their Cd and Zn content. The final Zn bearing solutions contain relatively high Ni concentra- tions (20-100 mg/1) and are treated with DMG and then neutralized to pH 4.6-4.8. The pre- cipitate is filtered off and the solution returned to circuit. DMG consumption is about 200% of theo- retical requirement, and Ni removal is 80% complete overall.

Jan 1, 1977

By G Chitombo, M Ruest

In surface mining, studies of the kinematics of blasted rocks using high speed film/video image analysis have allowed the estimation of the starting time, direction and magnitude of visible movement of fixed sections of the free face. Horizontal displacement versus time plots from discrete targets at the face generally report changes in slope over very small time intervals. These changes indicate step increases in velocity due to the action of explosive gases. In practice, the onset of rock mass movement, different to localised spalling, has been associated with a response time which exceeds the combined times of detonation, propagation and reflection of stress waves. This time is referred to as minimum response or burden movement time. As an engineering index, burden movement time has been used to provide guidelines for the selection of inter-hole and inter-row delay sequences in production blasting. With respect to improving breakage and fragmentation, it has been demonstrated that the delay interval between adjacent explosive charges should be less than the expected burden movement time. Similarly to reduce confinement between rows, delay intervals should exceed the expected burden movement time. The Hybrid Stress Blasting Model (HSBM) is a modelling framework that dynamically links an ideal and non-ideal explosives detonation code to a geomechanical rock model. This blast simulation tool is aimed at analysing the role played by different explosive formulations in fragmenting and/or damaging various rock types under different degrees of confinement. In the current framework, the rock behaviour under extremely high pressures and loading rates is calibrated from shock tests and the role of the explosive in fracture growth is accounted for and assumes a compressible fluid flowing through the explicit fracture network. The model is being developed as part of an international collaborative research project funded by a consortium of companies comprised of explosive and equipment suppliers and major mining houses. As part of the development and validation of the HSBM project, data from literature addressing the kinematics of the rock mass (ie burden displacement, face velocities and response times) has been collated and used to evaluate the current version of the code. A series of numerical experiments have been conducted with the view to: evaluate the response of the rock mass to changes in burden distance given by the impact of both stress waves and radial gas flow pressure;compare the modelling outcomes in terms of displacement, response time and face velocities to documented field observations; andcompare stress induced and stress/gas induced modes in terms of burden displacement outcomes. Results from these experiments have shown that in its current form the model is able to capture the trends observed and measured in practice. This is with respect to the simulation of burden displacement, response time and average face velocities for different geometries and charging conditions. The experiments have served as consistency checks which form part of an ongoing and comprehensive evaluation and validation of the HSBM code also aimed at addressing some of its current limitations.

Jan 1, 2007

Jan 1, 2004

This paper examines the reform of mining legislation over recent years, the establishment of new Crown land management agencies, and the role of the Crown and environmental groups in nature conservation in New Zealand. It describes the relationship of the minerals industry to the Department of Conservation and environmental groups over recent years, and the prospects for mineral development on the Conservation Estate in future.

Jan 1, 1995

By J Vann, C Seymour

Geology is generally treated as a æfront endÆ step in mine development. After infill drilling, the majority of resource estimation, mine-planning, development, mineral processing strategies and operational procedures are planned and implemented with little geological input, particularly in open pit operations. However, significant benefits in overall costs, cash flow, and technical risk reduction can be realised when sound geology is utilised more rigorously throughout the mining process. This under-utilisation of geology in the mining process has arisen due to a combination of factors:A lack of interest in, or knowledge of the full mining process by geologists. Few geologists fully understand where their inputs make critical impacts on downstream users. As a result of this, geologists generally do not focus their inputs towards areas of greatest value added, ie addressing issues critical for other members of the mining team. Most importantly, few geologists effectively communicate their results to the downstream users of their geology models. The results are that the potential benefits of geology, and the appropriate status of geology in the mining industry, are not fully realised. It is fundamental to realise exactly what geologists do. Geologists constrain geological processes and geometry. All geoscientific tools at the geologistsÆ disposal are geared towards one of these goals. An emphasis on geological processes is present throughout the exploration process, whereas in the resource estimation and mine development process an emphasis on geometry is required. The mining process is a web of disciplines that are attempting to optimise development of a resource to provide value to shareholders. Yet few people within these disciplines have a full appreciation of this web, and where sound geology inputs can add value through various feedback loops. Geology inputs do not end at the resource estimation stage, nor are they relegated to grade control implementation. If geologists have an appreciation of the mining process and close liaison with the other disciplines such as geostatistics, geotechnical engineering, hydrogeology, and mining engineering, they can significantly benefit project costs, timelines, and constrain technical risk by addressing their issues at the earliest possible stage. Furthermore, the mining process is not a single pass timeline, but an iterative process where the exploration, resource definition, mine planning and mining loop is continually repeated over the life of a project. Therefore, the potential inputs of geology are critical throughout the mining process. Effective communication of the impacts of geology inputs on downstream users is often lacking on mining projects. The most effective way to communicate geological results is through where it impacts most û project risk. Focussing all geology inputs and communication in terms of potential material risk allows the geologist to be more effective in contributing value to the mining process, and allows the downstream users of geology inputs to better constrain the risks associated with their aspects of the mining project. Through a program of geologists:taking an interest in the entire mining process and identifying critical areas for geology inputs to downstream users (the geologistsÆ clients); focussing geology inputs to address the potentially material issues on mining projects; and communicating their inputs to the æclientsÆ in terms of technical risk, geology will be much better integrated into the mining process. As a result, the potential benefits of geology throughout the mining process will be realised, and the status of geologists within the mining process will be elevated to a more pivotal position.

Jan 1, 2000

By Mules GJ

Geotechnical investigations have played a key role in influencing decisions for development of the Porgera Gold Project in the highlands of Papua New Guinea. Porgera is located 130 km west-northwest of Mt. Hagen in steep mountainous terrain with high rainfall. Much of the site is underlain by weak mudstone of the Chim Formation and creeping colluvial soils. Landsliding is common on the steeper slopes and in the valley floors. Structures have had to be sited to avoid areas susceptible to these movements. Early stage feasibility investigations included studies of tailings dam and waste rock dump sites, processing plant sites and hydroelectriic schemes. Further studies, leading into the design stage included the Enga Highway upgrading, water supply and power supply schemes. As construction for the project proceeds geotechnical input remains at a high level, with emphasis now on maintaining viable stable sites and refining data on which designs were based.

Jan 1, 1990

To reduce the corrosion of a stainless steel crystallizer, caused by accumulation of chloride impurity in the liquor during the crystallization of ammonium sulphate, a strongly basic anion exchange resin in the sulphate form may be used to remove the chloride from the liquor. The spent resin may be regenerated with dilute ammonium sulphate.The ions involved are sorbed by the resin in the order Equation 1. The sorption of chloride from the liquor and the regeneration of the resin depend upon the effect of concentration on the formation of the the ion pair NH6SO4. The sulphate ion dominates sorption from dilute solution of ammonium sulphate containing minor amounts of choride; choride ion dominates sorption from concentrated solution.

Jan 1, 1976

An attempt was made to determine the lateral extent of analcite in the Newcastle Coal Measure sediments of the Sydney Basin. From an examination of the cores of eleven bores it was concluded that the mineral is concentrated in the western sector of the original Newcastle Basin and this presumably was the region of greatest sodium concentration and aridity. The distribution of the analcite is such that it appears to have little correlative value.

Jan 1, 1967

By Van Rooyen F

An introductory review of the current grade control blasting techniques (selective mining strategies) used in the Eastern Goldfields has recently been undertaken. The survey was initiated and conducted by the Western Australian School of Mines. Four distinct selective mining strategies have been identified and a number of trends have been highlighted. Many operations, however, have developed techniques which use a hybrid method to suit the site conditions. The aim of all the mining strategies is to produce an optimum product. The optimum product is one which contains no diluent and experiences no mixing of the various identified ore and waste blocks and is fully reco- vered at the minimum overall operating cost. Due to this unified aim all of the grade control blasting techniques have many common design Features.

Jan 1, 1988

By Korsch RJ

Permian oroclines in eastern Australia must have formed by sliding on a detachment surface. It is identified as a westward- dipping Devonian and Carboniferous sub- duction zone. Major strike-slip faults probably sole out on the same surface. One major fault with an associated serpentinite belt was pulled away from the craton abd bent into loops. Basins formed in the loops.

Jan 1, 1987

By R Peden

Recent, detailed mapping, (Allibone, 1986; Peden, in prep.) of north west Stewart Island, has shown that the Rakeahua Granite (Watters et al, 1968), is comprised of a wide range of granitoid bodies ranging from diorite to leucogranite. As a result of the wide variation in granitoids Allibone (1986), suggests renaming of the Rakeahua Granite to the Rakeahua Granitoid Complex. Names were also proposed for the individual granitoid bodies mapped.

Jan 1, 1987

Resource developers in Papua New Guinea (PNG) are now, more than ever before, confronted with land-owner related issues that can hinder their corporate objectives.Development of PNG's custom-arily owned land since independence has brought sudden changes with mixed success. Exploitation of mineral resources has had its share of problems, and Highlands Gold Limit-ed's (HGL) endeavours in the central Highlands of PNG are no exception.

Jan 1, 1994

Close spatial relationships between the deposits of the Etheridge Goldfield (23,000 kg of bullion) and various regional geological and geophysical features suggest that genesis of the ore deposits was a multi-stage process that started with magmatic and metamorphic stages in the mid-Proterozoic, climaxed with structural and hydrothermal stages in the late Palaeozoic and terminated with an oxidation enrichment stage in the Cainozoic. Acceptance of this hypothesis permits classification of the Georgetown region into areas likely to contain deposits of the Etheridge type and those unlikely to do so. Consequently there is little scop- for the discovery of extensions of this field. However, the stratigraphic interval between the source rocks of the Etheridge field and stratigraphically higher host rocks of the Croydon field may contain disseminated replacement gold deposits of the Carlin type. The potential host (pyritic carbonaceous, and locally dolomitic siltstone of the Candlow Formation) is locally faulted and cut by granitoids and the extension of a mineralised, long-standing zone of structural weakness.

Jan 1, 1980

Laboratory and pilot plant investigations aimed at recovering gold as an electroformed sheet from gold eluate and gold leach solutions and slurries are discussed. The electrolytic test work undertaken makes use of high surface area electrodes, in particular nickel-chrome foam metal and activated carbon, as well as ultrasonic activation. The process involves initial gold electrowinning (or adsorption onto activated carbon), followed by gold electroforming, both operations being carried out in a specially designed reactor. The pilot plant work mainly involved the treatment of gold eluate solutions from a South African gold mine containing 600 mg/L Au: some tests were also carried out on gold leach solutions containing 6 mg/L Au. In the former case, very efficient gold extraction onto the foam metal cathode was achieved using electrolysis combined with ultrasonics. The polarity of the gold-loaded cathode was then reversed and, using a replacement electroforming electrolyte, gold was electroformed in situ onto a polished stainless steel mandrel, from which gold sheet was subsequently removed. In the case of leach solutions, pilot plant tests confirmed laboratory findings that in the presence of calcium (resulting from the lime used during the leaching process) no electrowinning is possible. Laboratory tests showed, however, that when sodium (in the form of NaOH or Na2CO3) is added to the leach solution, electrowinning can indeed take place. Alternatively, if a special activated carbon electrode is used (without current), the non-ionic calcium aurocyanide complex is adsorbed on to the activated carbon. When a gold-loaded activated carbon electrode is made anodic in a gold electroforming electrolyte, gold electroforming is feasible, although the efficiency is very low. The possible implications of these developments for gold recovery are further examined.

Jan 1, 2007

Before proceeding to the main portion of the above subject, a few remarks as to the general question of our mill slimes seem called for, and, with this in view, it is intended to briefly refer to the salient, points connected with their production, treatment and disposal at the mills.It is well known that, owing to the inticate mixture of the constituents of our sulphide ore, 'a very great deal of crushing and grinding is required to detach the particles of galena from the zinc blende and gangue of the ore, and it will be readily understood that, in this operation, a considerable amount of the material is converted into a slime which consists of minute, but ,(as can be see~ under a glass) well definied particles of all the constituents· 6f the ore arid combinations thereof, the relative proportions of which depend on the dual characteristics of hardness and abundance of the different constituents. An analysis of the slime shows the contents to be as follows :-Galena (PbS)Blende (Zn S)Pyrites (Fe Sll)Ferric Oxide (Fell Os)Ferrous Oxide (Fe 0) contained in garnetsOxide of Manganese (Mn 0) contained in rhodonite and garnets

Jan 1, 1903

By B Lumsden

During periods of high metal prices and strong metal demand tailings retreatment can be economic. Most tailings retreatment operations are technically challenging, low margin operations, because the easily recovered mineral has already been removed, therefore, process improvements can potentially yield large economic benefits. The Hellyer tailings dam was owned by Intec Ltd and contained 10.9 million tonnes grading 2.8 per cent zinc, 3.0 per cent lead, 88 g/t of silver, 0.16 per cent copper and 2.6 g/t gold. In November 2006 the Polymetals Group, as operator, restarted the Hellyer plant to retreat these tailings. Within a few months the operation had stabilised and Polymetals was meeting budgeted targets of throughput, metal recovery and concentrate quality. Polymetals and Intec then investigated methods that would improve the metallurgical result for this difficult to treat tailings. Since the tailings are fine-grained with 80 per cent <45 ¦m, magnetic aggregation of the paramagnetic sphalerite was evaluated. Magnetic aggregation of an oxidised tailings feed has not been tested before, nor had the technology been available when Hellyer ore was originally processed. Extensive statistical test work showed magnetic aggregation of the sphalerite fines in the zinc cleaner circuit increased total zinc recovery. The increase in the mean zinc recovery with magnetic conditioning was 3.63 per cent, at a statistical level of confidence of 97.8 per cent, and at the same mean zinc concentrate grade.

Jan 1, 2009

By B Roach, P M. Ashley, B Hooper

Mineral occurrences of the Hillgrove Au-Sb-W district are hosted in late Palaeozoic polydeformed, hornfelsed metasediments and Permo-Carboniferous granitoids of the NewEngland Orogen. In excess of 204 individual occurrences have been identified to date with the mineralisation developed as strike extensive (>20 km of known veining) and potentially depth extensive steeply dipping fissures. These are contained within an elongate area measuring some 9 km by 6 km in surface dimensions. Recorded gold production of 720 000 ounces along with current resources in the order of 340 000 ounces highlight the significance of this district. Historical antimony production is estimated at in excess of 50 000 metric tonnes. Significant tungsten of over 2000 t in the form of scheelite has also been produced from the field. Mineralisation is developed in veins, vein breccias, sheeted veins, network stockworks and as alteration sulfide haloes to the main structures. The vast majority of fissures are subvertical and vary in widths of up to 20 m in places. Paragenetic studies have previously indicated that the earliest mineralising event was a scheelite-bearing phase of quartz veining. Subsequent phases of arsenopyrite-pyrite-quartz-carbonate veining were accompanied by gold and minor base metal sulfides. Alteration is typically sericite-ankerite-quartz. Overprinting stibnite-quartz veining with gold-electrum, aurostibite and arsenopyrite form an important subsequent phase. Veining can be inferred from historical records to extend for vertical depths of over 1 km.

Jan 1, 2004

The beneficiation of heavy metal oxides, such as iron ore, is usually performed with heavy medium separation in cyclones, static baths and lately with Larcodems. Atomized ferrosilicon is most suitable as a heavy medium at densities above 3600 kg/m3 whereas a mixture of milled and atomized ferrosilicon is suitable at densities below 3600 kg/m3. When operating a beneficiation plant at densities higher than 3600 kg/m3 the quality of the ferrosilicon particles is an important factor that influences the control of the beneficiation process. Therefore, it is important to know how the rheology would be affected by the ferrosilicon quality as it also influences the control of the process at these elevated densities.

Jan 1, 2002

By G Mark, K L. Blake, G de Jong, J F. Rotherham, N D. Adshead

Magnetite deposits with distinctive ¦ actinolite ¦ apatite-bearing gangue and spatially-extensive sodic-calcic wall rock alteration occur in both Proterozoic metamorphic terrains and Mesozoic-Tertiary magmatic arcs. Examples from both settings constitute significant sources of iron ore (egKiruna, Sweden; El Romeral, Chile) and some host major Cu-Au deposits that have a local association with K-silicate alteration (eg Cloncurry district, NW Queensland; Copiapo district, Chile). A growing body of evidence points to a hydrothermal origin for these systems involving high temperature, low S oxidised fluids. The Cloncurry magnetite-Cu-Au deposits are products of the local structurally channelised influx of a specialised high salinity ore fluid into larger-scale alteration systems developed during pluton emplacement at greater depths than those associated with subvolcanic (porphyry) Cu-Au deposits. The geological characteristics of deposits in magmatic arcs are consistent with a similar mode of origin albeit in rather different tectonic settings.

Jan 1, 1995