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By K Palmer

Alluvial platinum was recovered during gold mining operations in Maud Creek, a tributary of the Howard River. Average electron probe analyses give Pt 88.75, Fe 5.27, Ir 0.70, Os 1.06, Pd 0.34, Ru 0.14, Rh 1.29, Cu 1.06. Rare grains of a Pt-Fe-Cu alloy are also present and an unusual feature of all grains is the relatively high rhodium content which finds expression in segregations of rhodium arsenide, cherepanovite. Platinum is found in the Orepuki area of Southland, where it is probably partly derived from the mafic rocks of the Longwood Complex. Rocks of the Rotoroa Complex, similar to those of the Longwood Complex, form bedrock in Maud Creek and are possibly the source of the Howard platinum. Alternatively, it might be derived by glacial transport from the Matakitaki ultramafic block 30 km to the southwest. Origin from the Rotoroa rocks is preferred as, if the Matakitaki rocks are part of the Dun Mountain Ophiolites, they might be expected to contain osmiridium rather than platinum. The ratio Pt:Ir-Os has been widely used to distinguish low Pt:Ir-Os ophiolitic from high Pt:Ir-Os gabbroic assemblages. Mafic complexes such as Longwoods, Darran, Rotoroa, and Riwaka might be expected to show similar high Pt:Ir-Os ratios and be targets for platinum exploration. Detrital platinum examined from the Parapara area, Golden Bay is mainly osmiridium, with rare grains of rutheniridosmine, very similar in composition to that found in concentrates from the Kaniere dredge, West Coast.

Jan 1, 1987

By T Harding, T Riggs, D Taylor

High-grade hematite ores in the Hamersley Province of Western Australia are associated with hydrothermal magnetite-apatite and magnetite-hematite-carbonate-apatite proto ores below the modern weathering surface. In addition, hydrothermal alteration of country rocks, once believed to be absent, is now recognised widely in shales and dolerites up to several hundreds of metres away from the ores. Both observations appear to exclude a simple supergene model for ugrading the host iron formations to high-grade hematite ore. Similar hydrothermal proto ores and country rock alteration are now being recognised in other high-grade hematite deposits worldwide, or have been recognised in the past.

Jan 1, 2002

By Associates

The headwaters of Skippers Creek and the Shotover River are reputed to be among the richest alluvial gold catchments in the world. This alluvial gold has no doubt been derived from reef systems similar to, and associated with, the Bullendale lodes. Physiographically the prospect covers steep ridges and deeply incised gullies between the Richardson Mountains in the west and the Harris Mountains in the east. Vegetation is mainly tussock with bush either side of Murdochs Creek. Access to the area is by metalled road to Skippers and then by 4WD track to Bullendale. Alternatively the prospect area can be reached by helicopter from Queenstown in around ten minutes.

Jan 1, 1992

The overwhelming weight of scientific opinion indicates that human activity is having a discernible and negative influence on the earthÆs climate system. The Australian Government, together with about 100 other nations, has accepted the findings of the Intergovernmental Panel on Climate Change third assessment report, released in 2001. This report was prepared by several hundred eminent scientists from all over the world, from various scientific disciplines and with differing opinions on global warming. The IPCC third assessment report contains a series of relevant, significant conclusions; for example, it finds that there is an increasing body of observations that gives a collective picture of a warming world and other changes in the climate system. Global average surface temperature increased over the past 100 years by about 0.6¦C. This may not seem much, but in the 900 years beforehand, the EarthÆs temperature remained relatively stable. The 20th century was the warmest of the past 1000 years in the northern hemisphere (there is much better information available from the northern hemisphere than the southern hemisphere). The 1990s were the warmest decade of the millennium in the northern hemisphere and 1998 was the warmest year. Although many factors influenced the EarthÆs climate, scientists are confident that greenhouse gas increases were the main factor contributing to global warming in the last 50 years of the 20th century. Increases in carbon dioxide, methane, troposhperic (lower atmosphere) ozone, halocarbons and nitrous oxide have all contributed to global warming. Combating climate change cannot be done without the cooperation of industry and the community at large. It is important that Government and industry work together to achieve greenhouse gas abatement while ensuring continued economic growth. The cause of the problem û the generation of greenhouse gas emissions û lies at the heart of the structure and size of modern economic activity. Greenhouse gas emissions are embedded in our way of life from our energy consumption patterns to the basic production of food. Moreover, the costs of the impacts of climate change to the earth will be potentially revolutionary, not merely evolutionary. It is in this light, acknowledging both the seriousness and nature of the problem before us that I want to reflect on the key drivers in the international climate change negotiations. A consideration of the past, present and future from what I see as the mid-way point in the process. In 1997, Parties agreed to adopt the Kyoto Protocol, which sets out mandatory targets for greenhouse gas emissions for developed countries.

Jan 1, 2002

By F P. Hao

Organo-sulphur-based collectors (eg xanthates, dithiocarbamates and dithiophosphates) are widely used in the flotation of sulphide minerals. Xanthates (ROC(=S)Sû), for example, adsorb strongly at sulphide mineral surfaces, in a reaction that is electrochemically coupled with the reduction of dissolved oxygen. One of the oxygen reduction products, hydrogen peroxide, reacts directly with dissolved xanthate, leading to its oxidative decomposition. Experimental work has been conducted, using ethyl xanthate, to understand the molecular mechanism by which hydrogen peroxide reacts with xanthates. A number of degradation products have been identified, some of which have not been reported previously. This oxidative decomposition reaction pathway is discussed in the broader context of xanthate decomposition in flotation systems. One of the identified ethyl xanthate decomposition products, ethyl perxanthate (ROC(=S)SOû), has been observed in the process water of a number of mineral processing operations. The interaction of this molecule with goethite (α-FeOOH) particles, typical of that found in tailings dams, has been studied in more detail using attenuated total reflectance (ATR)-FTIR. The ethyl perxanthate molecule has been found to coordinate to iron (FeIII) at the goethite surface, and undergo a surface-catalysed decomposition process. In the presence of both PbII and goethite, a ternary surface complex is formed, where ethyl perxanthate is coordinated directly to surface adsorbed PbII atoms. The results obtained give some insight into the environmental fate of ethyl xanthate in tailings streams, and a basis on which to consider the environmental importance of such species in tailings dams. Strategies for the destruction of residual xanthate levels in waste water streams are discussed in terms of the likely reaction products.

Jan 1, 2002

The sedimentary basins of this region developed in the collision zone of thePacific Ocean plate and the continent. Stresses were transmitted thorough wedge-like lithospheric blocks, such as the Okotsk Sea, East Kamchatka, Aleutian and other smaller blocks. Compression and inversion were more active at the boundaries: ***INSERT EQ*** and ***INSERT EQ*** in places. Tension, rifting and the increase in the rate of sedimentation were marked in P1-2, P3, N12, and also in N2 û Q in places. Structural plan changes of the sedimentary basins and possible oil, gas and fluid migration occurred more actively at the boundaries: ***INSERT EQ***.

Jan 1, 1995

Flotation of Composite Synthetic Particles

Sep 13, 2010

The New Zealand Steel Ironsand Slurry Pipeline was successfully commissioned in February 1986. The project includes 18 km of high pressure, polyurethane lined buried pipe. McConnell Dowell Constructors Limited has developed a coupling which has allowed this pipeline to be fully welded. The design and development of the coupling and its application on this project is discussed.

Jan 1, 1986

By N Weerasekara, M Powell, P Toor

The effect of liner wear on SAG mill performance has gained much attention in recent years. It is commonly observed that the three key performance criteria of SAG milling; throughput, power and product size all improve as the liner wears.The increase in throughput is generally ascribed to the increase in the grate apertures and the increase in mill volume due to the wear of these components. Whilst the decrease in product size is attributed to the reduction in lifter height and angle, resulting in more breakage by means of attrition and abrasion.Though it is widely acknowledged that the wearing of liner components such as Lifters, Plates and Grates have a significant impact on mill performance, their individual contribution to changes in mill performance has been unclear, and resultantly lead to questions like; what percentage of the throughput increase can be attributed to the increase in mill volume (plate wear)? and how much can be attributed to the increase in grate aperture (grate wear)?It has been found that through the use of grinding surveys, analysis of production data and JKSimMet it was possible to separate the effects of changing liner profile, increasing mill diameter and increasing grate aperture on the mill performance allowing for the quantification of each.The outlined methodology allows for both troubleshooting of problem liner components which reduce milling efficiency in their wear life as well as providing a basis for a more quantitative approach to liner design and reline scheduling.CITATION:Toor, P, Powell, M, Hilden, M and Weerasekara, N, 2015. Understanding the effects of liner wear on semi-autogenous grinding mill performance, in Proceedings MetPlant 2015, pp 150–161 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By M E. Dunphy, P Silversmith

The Reefton Goldfield, both historically and potentially, represents a significant gold producing camp in the Westland province of New Zealand. Some two million ounces of gold have been produced from the Greenland Group host rocks between 1870 and 1951 with the most significant producers being the Blackwater and Globe Progress mines.   Steep terrain, high rainfall, poor outcrop, widespread fluvio-glacial deposits, tertiary cover and sometimes onerous environmental access conditions have proved a challenge to conventional exploration techniques. In addition classic exploration techniques have come up against a desire to reduce exploration cycle time and exploration costs while increasing both quality and quantity of geological information.   The trial, and subsequent implementation, of Wacker sampling has proved a highly successful and effective geochemical tool currently being utilised to target, discover, and define potential economic gold mineralisation in the Reefton Goldfield.

Jan 1, 1997

By G A. Blengini, S V. èolar

The minerals industry is faced with choices beginning in the exploration phase and extending over the life cycle of the mine. Firms examine the technical feasibility of alternative actions and typically rank them based on economic performance. Increasingly firms also consider alternativesÆ contribution to sustainable development. There are many visions of what a sustainable future should look like and much debate about what should be sustained. Sustainability is a process, a series of incremental actions, and each alternative course of action has the potential to further progress toward one or more sustainability goal. However, because it is not possible to sustain everything everywhere simultaneously, trade-offs and choices inevitably have to be made.Sustainable decision making before investment (ex ante decisions) should incorporate a broad suite of quantitative and qualitative information. One approach is to utilise an integrated sustainability assessment (ISA) framework that supplements traditional technical and financial tools with other tools such as objectives hierarchies (OH) and life cycle assessments (LCA). OH is a problem framing method that captures stakeholder and decision maker interests, objectives and values. LCA addresses material and energy flows, and environmental impacts. The outputs of these tools can be combined with additional qualitative measures and analysed using multi-criteria decision analysis (MCDA). MCDA models facilitate comparison of different alternatives on the basis of a set of criteria and indicators. Some can incorporate information on risk attitudes and preferences ( multi-attitribute value theory models) and others uncertainty about outcomes (multi-attribute utility models). Studies have been published describing and comparing tools for minerals sector decision analysis. Our paper extends this literature, discussing how a combined OH-LCA-MCDA can support ex ante sustainability assessment by incorporating preferences, risk attitudes, and monetised or non-monetised social and economic variables, in a manner that captures their inherent complexity. We also discuss how such a combined model would support trade-off analysis.

Jan 1, 2009

By M Lentz

This paper will discuss the issues associated with blasting in an urban mining environment that have been addressed by Winstone Aggregates at the Mt Wellington Quarry. These issues include - control of vibration and air overpressure, repeatability of shot performance, fragmentation on an extremely low maximum instantaneous charge, compliance with Territorial Authority regulations and perception. Over the last two years, in order to address these issues, Winstone Aggregates have undertaken a programme of continuous improvement, which has included; ò implementation of new technology; ò revising site procedures; ò conducting an investigation into the structural response of local buildings; ò investigating safe extrapolation; ò extensive public consultation; ò establishing credibility during the consent process; ò identification of perception issues; and ò building relationships and trust with neighbours. The issues addressed at the Mt Wellington Quarry have increasing significance for traditionally rural mining operations, as the input of the local community being urban or rural, increases. New and existing operations have the potential to adopt best practice now, building trust with the community and raising the profile of the industry.  

Jan 1, 1999

Maintaining high carbon activity is vital to the efficiency of any Carbon-In-Leach or Carbon-In-Pulp process. Reduced activity can lead to longer residence times or gold losses in the tails. Regenerated carbon from the CIL circuit at Macraes Gold Mine was analysed for kinetic activity and composition over a 15 month period. An increase in kinetic activity during the time period was recorded, which was linked to reduced Na and Ca loadings. A laboratory simulation of the loading, stripping and regeneration of gold was developed and tested. Kinetic activities were obtained for synthetically fouled carbons following three circuits of the laboratory simulation. It was shown the competitive gold adsorption ability of xanthate fouled carbon (previously reported as a serious deactivator) could be significantly recovered following effective thermal regeneration. This ability was maintained in a subsequent circuit loading.

Jan 1, 1993

By D Craw

At Reefton, mesothermal gold deposits occur in the Ordovician Greenland Group basement and bituminous coal deposits occur in overlying Eocene Brunner Coal Measures. These different resource types occur in close proximity to one another in the same topography, vegetation and climate. Both types of resources have been mined for many years and as a result historic mining areas discharge water with chemistry reflecting the mineralogy of the deposits. Coal measures release natural acid rock drainage throughout the region due to oxidation of pyrite in coal and associated sediments. Levels of acidity are increased in mining areas, and pH near three is common. Gold mines contain pyrite, arsenopyrite and stibnite. Discharge waters from these sites have pH near seven because of the high acid neutralising capacity of the basement rocks. Both coal and gold mining sites have iron oxyhydroxide precipitates in drainage waters. These precipitates are more abundant at gold mining sites, and one deposit is up to 5 m thick. Iron oxyhydroxide at coal mine sites contain Zn (up to 89 ppm), Ni (up to 10 ppm), As (up to 163 ppm), Cr (up to 23 ppm), Pb (up to 16), and Cu (up to 11 ppm). Jarosite group minerals have been identified in the coalmine iron oxyhydroxide, although most of the material is amorphous. Gold mine iron oxyhydroxide contains Zn (up to 353 ppm), Ni (up to 592 ppm), Cr (up to 17 ppm), Cu (up to 72 ppm), Pb (up to 29 ppm), Sb (up to 230 ppm), and this material is particularly high in As (up to 20 wt per cent). Most of the material is amorphous but distinctive zones (mm scale) are As rich (up to 30 wt per cent As oxide). Pharmacosiderite, K2Fe4(As04)3 (OH)5.6.3H20, is a secondary mineral in one deposit. These iron oxyhydroxide deposits are useful indicators for the metals mobilised into the environment by oxidation in the historic workings.

Jan 1, 2003

Industries in the Kwinana area have embarked on a journey of improving the eco-efficiency of Western AustraliaÆs primary heavy industry area. The Kwinana Industrial Area has some unique characteristics that provide both opportunities and barriers. The Kwinana Industries Council and the Chamber of Commerce and Industry are working with the industries to identify a range of projects that can deliver improvements for both environmental and economic æbottom linesÆ, and to progress these projects using internal and external resources. The evolution of the process, its relationship to the ethos of operating companies, and the availability of resources to pursue projects, is an interesting study with lessons for others interested in taking the same course.

Jan 1, 2002

By R J. deMelo, A, V Suckal, R A. Vilela

Massive hematite ore (MHO) is a special high-grade iron ore used as lump ore in the process of obtaining direct reduced iron (DRI). The influence of porosity on the reducibility was investigated using optical and scanning electron microscopes. Hematite is the main component of the samples and occurs as granular crystals (10 ¦m), microplates (1 ¦m) and euhedral martite (10 to 30 ¦m). Quartz, maghemite, kenomagnetite and goethite are minor components. Primary micropores (+ to 1 ¦m) are associated with microplaty crystals that fill cavities between granular hematite. Secondary micropores (+ to 5 ¦m) related to euhedral martite crystals are the most important. The total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 18 per cent, whereas unweathered samples have a porosity less than 2.5 per cent. Varajpo et al, 2002 showed that reducibility is strongly enhanced by porosity and this work shows that reducibility can be indirectly evaluated by bulk density.

Jan 1, 2002

By P M. Black, T Itaya

Arc-type volcanic activity has been a major feature of the late Cenozoic geological evolution of the Pacific-Australian plate boundary in the northernNew Zealand region. The time/space distribution patterns of arc-type rocks reflect changes in the nature of the plate boundary as it has evolved. Inception of volcanism began in the north during earliest Miocene times (26 Ma) following ophiolite emplacement and during the next 10 Ma developed into a volcanic arc segment extending south to the present position of the central North Island. The northern part of the arc became extinct about 15Ma ago, but activity continued in the central (Coromandel) part of the arc until about 5 Ma ago. In late Pliocene and Quaternary times volcanic activity has become concentrated in a northeast trending zone which is collinear with the Tonga-Kermadec Arc.   These time/space patterns can be interpreted in two ways. Firstly, if relative plate motion was essentially transform in the region prior to 26 Ma then a small change in the relative plate vectors may have initiated subduction and the associated volcanism. Southward evolution of the arc can then be seen as the straightening and extension of a single arc. Alternatively, the distribution of volcanic rocks can be interpreted as the capture of a relatively short lived arc by southward migration of the dominant Tonga-Kermadec subduction system.

Jan 1, 1995

Research on the Thermodynamics of Siderite Roast Decomposition and the Experiment of Magnetic Roasting-Separation

Sep 13, 2010

The Hyde-Macraes Shear Zone (HMSZ) is low angle, duplex thrust system that has developed in a graphitic pelite schist within the Otago schist belt, New Zealand . At Round Hill lateral ramps have developed parallel to the movement direction between+ the footwall and hangingwall shears. These structures exhibit normal oblique-slip displacement which has been an important mechanism for creating space in an otherwise compressional system. Gold-bearing quartz veins were emplaced along the boundary shears and lateral ramps during thrusting. Gold within the lateral ramps is coarse (up to 300 microns) however hanging wall cataclasite development in the boundary shears after the gold was deposited has reduced the grainzise of most of the gold to less than one micron. This bimodal gold distribution has metallurgical implications with respect to the maximisation of gold recovery at Macraes.

Jan 1, 1993

Based on relative CO2, N2, and 3He contents, geothermal systems of the Taupo Volcanic Zone, TVZ, can be subdivided into two major groups: arc-type systems, associated with andesitic magmatism along the eastern boundary of the TVZ, and rift-type systems over its western parts. The highly increased N2/3He, CO2/3He and CO2/Cl ratios of the former are ascribed to entrainment of large proportions of volatiles of subducted, marine sedimentary origin. The largely rhyolitic, rift-type magmas are assumed to have formed from volatile-depleted, residual melts. Correlations of Cl and CO2 with heat contents suggest that formation of the two types of source magmas involves mixing of two end member components: a low-volatile melt with a heat/Cl ratio of 25 Ml/mol (0.7 MJ/g), and a low Cl vapor with a heat/CO2 ratio of 5 Ml/mol. On the basis of these values, the heat associated with andesitic magmas is found to be carried in close to equal parts by both vapor and melt; for the rhyolitic melts the proportion contributed from the vapor is only about 2%. The heat/He ratios of the rhyolitic source magmas for the rift-type geothermal discharges from the TVZ of 0.12¦0.05 Ml/pmol is within the range of 0.05 to 0.2 Ml/pmol of the upper mantle. The higher heat/3He ratios for the arc-related magmas of 0.4¦0.2 Ml/pmol are likely to be due to the high proportions of heat carried in the form of a separate, low 3He vapor phase derived largely from subducted sediments.

Jan 1, 1995