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By L R. Marshall, M J. Rubenach, T G. Blenkinsop, J S. Cleverley

The source and transport regions of fluidised (transported) breccias outcrop in the Cloncurry Fe-oxide-Cu-Au district, providing insights into the origins of other fluidised magmatic-hydrothermal breccias such as kimberlites. Discordant dikes and pipes with rounded clasts of metasedimentary calc-silicate rocks and minor felsic and mafic intrusions extend several kilometres upwards and outwards from the contact aureole of the 1530 Ma Williams Batholith into overlying schists and amphibolites. The brecciation initiated at depths >10 km and may have resulted in surface breaching. We used analytical equations for particle transport to estimate clast velocities (eÆ 20 ms-1), approaching volcanic ejecta rates (up to 80 ms-1). The wide range of CO2 fluid inclusion densities (up to 150 MPa), the localisation of the base of the breccias in contact aureoles, and the scale and discordancy of the bodies suggests the breccia transport process was triggered by an abrupt release of overpressured fluid. At these depths, such extreme behaviour may have been achieved by release of dissolved fluids from crystallising magma, in combination with a strongly fractured and fluid-laden source, sitting under a strong, low permeability barrier, and such parameters may be analogous to the asthenosphere/lithosphere boundary in the case of kimberlite initiation. The relationship of these breccias to the Ernest Henry iron-oxide-Cu-Au deposit suggests they may have been either fertile or æfailedÆ orebody feeders.

Jan 1, 2005

By S Williams

The primary objective of most mining projects is to maximise the value delivered to the companyÆs shareholders. Achieving best practice performance and maintaining competitive advantage through low-cost production and high productivity is essential to achieving this aim. Benchmarking is an essential tool for the identification and implementation of best practice performance, and to realise continuous improvement by ensuring best practice becomes common practice. But to be successful, that is to deliver long-term value creation, benchmarking must be holistic and align operational performance with strategic intent. This paper outlines a rigorous and structured approach on how to conduct a successful benchmarking program that aligns operational performance with the businessÆs goals. Further it investigates the benefits that benchmarking can provide throughout the project life cycle and provides some key learnings from some of the worldÆs leading miners.

Jan 1, 2009

By P Blattner

The Late Miocene gold-silver bearing epithermal system at Waihi has some close similarities in its paleo-thermal and geochemical structure with modern, volcanic-hosted geothermal systems such as Ohaaki-Broadlands. At Waihi an extensive braided quartz vein system is enveloped by hydrothermally altered andesites with minor tuff breccias and tuffs. A main stage of vein filling consists of multiple phases of chalcedonic quartz and fine to medium grained quartz, which are accompanied by pyrite, sphalerite, galena, chalcopyrite and acanthite below the base of oxidation. Platy calcite is present locally. Fluid inclusion studies indicate that the main stage quartz was deposited at temperatures of 189¦-273¦C from dilute (Tm of -0.1 to -1.0¦C) fluids that were locally boiling. Homogenisation temperature Th versus Tm data points lie within the field enveloped by dilution and boiling/gas loss paths determined for the Ohaaki geothermal field, and indicates that the parent hydrothermal fluid for the Waihi epithermal system had a similar composition to that at Ohaaki, ie 0.2 wt% equiv NaCl and 3.3 wt% equiv CO2. The hydrothermal alteration mineralogy and the isotopic composition of vein calcite indicate that the hydrothermal fluid contained relatively high concentrations of CO2 , as at Ohaaki. Oxygen isotope analyses of main stage quartz range from 6.1 to 11.6 %0 and of vein calcite from 2.29 to 9.4%0. Calculated d18Owater values for the hydrothermal fluid that deposited the main stage quartz range from 2.0 to -5.7%0, with a trend to less negative values with depth. They are similar to those in the deep chloride fluid in active geothermal systems with a substantial fluid throughput. A high fluid throughput at Waihi system is also evident from the extensive high intensity hydrothermal alteration and large volume of quartz deposited in the vein system.

Jan 1, 1995

An Ammonia Leaching-Solvent Extraction-Electrowinning-Flotation Process for Copper Oxidised Ore Treatment

Sep 13, 2010

By A Croll

A panel cave using LHDs for ore extraction came into production at Premier in 1990 at a depth of 630 metres below surface on the western side of the mine in the BA5 mining block. A post-undercut mining sequence was used with all development on both the undercut and production levels completed prior to the undercut being advanced over the pre-developed drawbells. Support and rock mass damage on the production level was extensive as the undercut moved overhead. Undercutting and coarse fragmentation created problems. The mining sequence was changed to an advance undercut with the minimum of development and support undertaken on the production level prior to the undercut moving overhead. Only once the abutment stresses had stabilised were drawbells developed and final support installed. The height of the undercut drill design was decreased from 18 to 13 metres. The changes resulted in markedly less rock mass and support damage on the production level. Lessons learned in the BA5 mining block on the 630 level were incorporated into planning and scheduling the BB1E mining block which came into production on the 732 metre level on the eastern side of the mine in 1996. An advance undercut mining sequence was planned, undercut height was minimised and undercutting parameters were optimised in terms of the BA5 experience. Numerous problems still occurred. As the undercut area increased in size severe spalling from the cave back resulted in vertical propagation of the cave to a height of 30 metres instead of the planned 13 metres. The resultant coarse fragmentation created secondary blasting problems and an excess of undercut ore that had to be loaded and trammed, slowed the rate of undercut advance. The planned mining sequence was compromised and considerable support and rock mass damage resulted on the production level below. Once these problems had been overcome the undercut advanced at the planned rate and continuous caving initiated at the predicted hydraulic radius. At a later stage the unexpected ingress of water hampered undercut drilling and slowed the rate of undercut advance in a section of the cave. Leads and lags between adjacent tunnels and the overall face shape could not be developed as planned. The rate of natural horizontal cave propagation exceeded the rate of undercut advance and three undercut drilling tunnels were extensively damaged. More tunnel development on the production level prior to undercutting than was planned resulted. The slow advance of the undercut and high abutment stresses caused extensive damage to installed support and the rock mass on the production level, 15 metres below. Experience in the BB1E mining block on the 732 metre level has taught that an advance undercut mining sequence reduces damage on the production level markedly. Extremely tight control on the rate of undercut advance, leads and lags between adjacent tunnels and overall undercut face shape as well as extraction ratio, tunnel development and support sequence on the production level below is required. Premier Mine plans to implement a block cave at a depth in excess of 1000 metres within the next decade. All the experience gained on current mining levels together with data collection and numerical modeling is being used to plan the proposed mining operation. The geotechnical challenge of mining at this depth in weak rock has been identified as the greatest risk to the project. Challenges centre around adopting the correct mining sequence, limiting the extent of rock mass damage associated with undercutting and effective support. The hydraulic radius needed to initiate caving, fragmentation, drawpoint spacing, secondary blasting and the possibility of seismicity are geotechnical concerns that are being addressed. Results to-date suggest that a pre-undercut mining sequence with all development and support on the production level carried out only after the undercut abutment stresses have passed overhead will have to be implemented.

Jan 1, 2000

Construction work on one of the world's largest landslide stabilisation projects is drawing to a close in Central Otago. Begun in mid 1990, major stabilisation work has been carried out on seven large rockslides which will be partially inundated when the Clyde dam reservoir (Lake Dunstan) is filled. The work has required the construction of 14.5 kilometres of tunnel, 60 kilometres of surface drilling, 78 kilometres of drilled drainage holes and five million cubic metres of earthworks. The stabilisation programme has been carried out by the Electricity Corporation of New Zealand as part of the Clyde Power Project, a hydroelectric development on the Clutha River.

Jan 1, 1992

By T Graham

The invention of the traditional belt and idler conveyor system is attributed to Thomas Robins in 1892. This basic concept, ubiquitous in most mining operations, has not changed markedly in 125 years and still suffers from five forms of energy losses. Firstly, Wheeler, Roberts and Jones (2004) showed that indentation rolling losses, a consequence of the indentation a roller inflicts on the belt, consume 60 per cent of all energy. Secondly, Wheeler (2006) explained that bulk solid flexure resistance resulting from material interaction and movement absorbs 20 per cent. The remaining energy is lost by idler rotating resistance (5 per cent), belt flexure resistance (5 per cent) and secondary resistances (10 per cent).Traditional conveyor systems are continuous as opposed to batch systems, implying both positive and negative features. On one hand, continuous systems have high availability (available infers ‘ready to run’), but, on the other, utilisation of availability is often low; for example, when a conveyor is running empty or below capacity. This converts into reduced system OEE (overall effective efficiency). Many attempts have been made to mitigate energy losses and low OEE issues, including development of rail-based systems. The key drawbacks have been higher capital cost, low flexibility, poor availability and lack of market acceptance.A recent conceptual development known as the ‘autonomous rail conveyor’ (ARC) promises to address issues of energy loss and poor availability and provide increased flexibility by offering solutions for difficult applications. The ARC uses a series of interconnected skeletal bogies covered with a conventional conveyor belt as a load bed running on relocatable light rail. The bogeys have two axles, each driven by integrated variable speed-geared motor and brake systems, and are connected to previous/next bogeys by specialised couplers. Power is provided by a generator (located in a dedicated bogey) and ‘daisy chain’ plug in cables. Centralised redundant control is provided at a preferred point. Although the system is batch in nature, the number of carriages and trains is flexible, meaning that the system is effectively continuous. Loading is achieved by feeding the ARC from a perpendicularly oriented apron feeder, while material off-loading is accomplished by a twist-dump operation in which the belt is twisted through an angle of 50° below the horizontal, causing material to flow from the belt into a receiving conveyor.The ARC system can run multiple trains over any distance, although benefits are more significant in distances of over two kilometres. Capital and operating costs are predicted to be lower than competitive products, with planned maintenance being simple to perform.CITATION:Graham, T, 2017. The autonomous rail conveyor significantly reduces ore haulage costs, in Proceedings Iron Ore 2017, pp 467–472 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

How Particles Stick to Bubbles - The Influence of pH and Hydrophobicity in Flotation

Sep 13, 2010

Fast Adsorption Phenomena at Air/Liquid Interfaces

Sep 13, 2010

By M Sherman

The challenge facing the engineering provider is to calculate throughput rates when faced with disparate specific energies calculated by different testing methodologies. Typically, an ownerÆs team would expect that the throughput calculations be checked using more than one method, therefore it is inevitable that there will be differences, based on which methodology is used. This engineering challenge is exacerbated by the continuing evolution of contemporary circuit configurations such as two stage pebble crushing with or without high pressure grinding rolls (HPGRs) as the second stage, or second stage pebble crusher product reporting to the ball milling circuit, etc.This paper is a companion to the paper first presented at SAG 2011, which showed that the Bond Indices are an excellent tool for estimating the specific energy requirements for semi-autogenous grinding (SAG) mills in single-stage SAG milling (SSS) circuits, SAG and ball mill circuits (SAB) or SAG and ball mill circuits with pebble crushers (SABC). This paper presents how the Bond Indices have been used to calculate ball mill specific energies, and therefore throughput rates, for SAG mill based circuits. Once the ball milling specific energy is known, tower mill and vertimill energy requirements can also be calculated. It is noteworthy that the method presented in this paper does not require the use of any unpublished correction factors: the proposed method uses the Bond parameters and equations published by Rowland in 1982.CITATION:Sherman, M, 2013. 21st century bond, in Proceedings Iron Ore 2013 , pp 309-312 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By D Craw, P Upton

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Otago Schist belt of southern New Zealand hosts widespread orogenic gold deposits. Erosion of these orogenic gold deposits has led to the formation of numerous placer deposits distributed across and beyond the host schist belt. Numerical modelling of crustal scale deformation and geomorphic evolution has defined the key tectonic features that have controlled the severance of detrital gold deposits from their sources. Tectonic activity over the past 20 million years, during development of the modern Pacific-Australian plate boundary, has severed links between some placers and their sources. Detrital gold was transported south from the Otago Schist source region in two different river systems in the Miocene. Mesozoic orogenic gold deposits shed gold into rivers that flowed to the south. These rivers were terminated by the rise of north-west-trending basement ridges at the boundary between weak schist crust and strong greywacke crust, and the ridges were controlled by pre-existing faults at that rheological boundary. In contrast, rising mountains close to the developing plate boundary in the Miocene were the locus of new orogenic gold deposits hosted in extensional faults. These gold deposits were rapidly exhumed and contributed detrital gold to orogen-parallel Miocene rivers that flowed to the south-west. Pleistocene deformation on mainly north-west and north-east orientations, and associated river capture, has severed the links between these Miocene orogenic deposits and downstream detrital gold.CITATION:Craw, D and Upton, P, 2015. Tectonic severance of links between placer gold and its sources, southern New Zealand , in Proceedings PACRIM 2015 Congress, pp 541–544 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

Atlas Copco Construction and Mining Australia identified a number of issues in regard to the skill levels, labour turnover and productivity of our service technicians. In 1994 we were experiencing a labour turnover rate of 42 per cent per annum amongst our technicians. Exit interviews were held with each individual and one of the major areas of dissatisfaction was the degree of product training provided on our equipment, compared to what is required to be competent across the range of our products. These tradespersons were prepared to accept the reduced remuneration that an OEM offers, for the benefit of comprehensive, professional training that, in theory, could be provided. The truth is that we were achieving approximately 40 per cent of our target for training hours because of the demands of field service, pre-deliveries, etc. So, the summary was the same as the industry was experiencing at that time because of skilled labour shortages, production demands, etc people were employed and thrown in at the deep end. A recipe for failure that will be successful every time.

Jan 1, 1998

By G J. Corbett, T M. Leach

Approximately 42 t of mercury were produced from Puhipuhi from the late nineteenth century until the end of World War II, with no significant gold or silver production. Sinter, eruption breccias and veins, mined for mercury at Puhipuhi and essentially barren of gold, are inferred in many geological models to represent the surficial levels of adularia-sericite style low sulfidation gold-silver systems. These systems may contain economic gold-silver mineralisation at depth. Conceptual geological models have been employed at Puhipuhi in the search for buried gold mineralisation. Homestake Mining utilised a McLaughlin model for exploration from 1982 to 1987, targeting mainly the vicinity of the sinter deposits. From 1987 to 1989 BHP sought deeper structurally controlled gold mineralisation within the basement greywackes, utilising models derived from studies of Round Mountain, USA and Hishikari, Japan. Macraes Mining Company Limited have accessed the previous work and applied a conceptual geological which invokes a north-south structural control for the emplacement of high-level felsic intrusions at depth. Dextral movement on these structures associated with oblique convergence facilitated the formation of a pull-apart basin in which lacustrine sediments overlie basement greywackes and are in tum overlain by Pliocene basalts. Continued activation of the NS structures created a series of inferred NE-trending dilational structures, which are targeted as fluid upflow centres for the surficial outflows. Upflows occur as eruption breccias (e.g., Plumduff) and outflow as silica sinters (eg Mt Mitchell, Williams) which are also partly obscured by the basalt cover. Argillic alteration and mercury mineralisation occur at elevated crustal levels (eg Puhipuhi mine). Modelling from structure and alteration zonations have targeted a fluid upflow in the vicinity of Bush Hill, which was not accessed by previous workers. This target was subsequently supported by surface geology and multi-element soil geochemistry.

Jan 1, 1997

By J M. Shekiro

In the chloride process to manufacture TiO2 pigment, feedstocks containing higher TiO2 contents (high-grade ores or HGOs) are favoured in order to minimise production of undesirable by-products. Most of today’s HGOs are produced through the smelting or reduction and leaching of ilmenite, processes which consume significant energy and/or produce large volumes of non-titanium materials that may have to be landfilled. In order to improve the economic and environmental sustainability of its TiO2 business, the DuPont Company, working with Kobe Steel Ltd, has developed an innovative process called TiRON for making HGO. Using a rotary hearth furnace, the process reduces ilmenite to a high TiO2 slag and metallic iron granules. The TiO2 slag is suitable for TiO2 pigment manufacture, and the iron is suitable for steel making. TiRON can process sand or rock ilmenite of varying compositions and particle sizes. Fossil fuel instead of electricity supplies the energy for the reduction. Dusts and off-spec materials are recycled. These process attributes, together with capital requirements estimated to be significantly lower, give TiRON substantial economic, environmental, and process flexibility advantages over conventional ilmenite upgrading processes. TiRON has been demonstrated at the semi-works scale, and preparations are being made to bring it to the pilot scale.

Oct 5, 2011

By F K. Buckley

Currently, Kanieri Gold Dredging Limited operates the only large scale gold dredging operation in New Zealand. It dredges a claim in the Taramakau River using the bucket dredge 'Kanieri'. This dredge, a 'Yuba' type, was designed and built in the 1930s. On the current claim it works about 12 hectares of ground a year. Because of its design, the tailings from the 'Kanieri' make land restoration difficult. This was unimportant until it commenced its new claim ML-32-310 in 1978. The conditions, attached to this licence required it to restore the land for afforestation, the designated use fur the Crown land being mined. With the company planning to work future claims on the Grey River, it decided to undertake restoration work on the Taramakau to demonstrate its capability of establishing pasture land on tailings, a more difficult task than restoring the land for afforestation. After two years and the restoration of two blocks totalling 22 hectares, reasonable pasture establishment has been achieved. Much has been learned to date and further refinement of the techniques used will take place over the next two years. The quality of the tailings produced has improved as a result of the limited modifications possible on the existing dredge. This has been significant in achieving better results. The knowledge gained will be taken into account in future dredge design. Both the Company and its Consultant are confident of achieving satisfactory restoration of dredge tailings for pasture land.

Jan 1, 1981

The Barmac autogenous crushing mill is one of the most successful new comminution technologies to become available to the mining and industrial minerals industries in this decade.   The Barmac autogenous crushing mill is an innovative Vertical Shaft Impactor which operates in essence like a high intensity dry ore centrifugal pump with the reduction occurring primarily as a result of high velocity rock to rock impact in a fully rock lined crushing chamber.   With applications in a wide range of mining and industrial minerals operations the Barmac autogenous crushing mill presents an opportunity to enhance reduction and liberation whilst providing many cost savings and production increases in new and existing plants.   This paper briefly describes the operation of the Barmac autogenous crushing mill and reviews its benefits.

Jan 1, 1990

The range of environments which control the level of ground support required vary greatly in terms of rock type, rock structure and the mining method used. At the operating mines visited during this review the level of ground support was such that incidence of rock-fall- related accidents were rare. It was also found that methods existed to support most of the conditions encountered. The main problem areas were weak rock, major geological structures, areas of heavy jointing, high development density and areas affected by high mining-induced stresses and blasting. With stope support the level of success was much lower than that achieved in development; the larger spans and more rapid changes in geometry of open stopes compared with cut and fill stoping (where cables were originally used) led to significant problems. Before a useable design method for cable support of stope walls and pillars can be obtained the precise failure mode of the walls and pillars, and the interaction of the support and the rock mass must be investigated.

Jan 1, 1982

This paper considers the application of recent laboratory gas sorption data to the understanding outburst phenomena in underground coal mining. Previous use of threshold limits based on gas content and coal rank are placed in perspective. Although this work focuses on overseas research and experience, parallels can be drawn for New Zealand coal settings, taking into account localised mining and geological factors.

Jan 1, 1994

Jan 1, 2004

By R R. Large

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The formation of orogenic gold deposits is commonly a two-stage process. The first stage involves preconcentration of gold in a suitable source rock, such as carbonaceous black shales, felsic volcaniclastics or komatiitic volcanics. The second stage involves the release of gold (commonly with arsenic and/or tellurium) from the source rocks during metamorphism or magmatic intrusive events, accompanied by the replacement of source rock pyrite by pyrrhotite. Recent research suggests that synsedimentary gold trapped in the structure of diagenetic arsenian pyrite in reduced carbonaceous facies of continental margin sedimentary basins is an ideal source of gold for many orogenic and Carlin-style gold deposits. The conversion of diagenetic arsenian pyrite to pyrrhotite during basin closure and greenschist facies metamorphism is the key process releasing gold and arsenic to the metamorphic fluid, with metal deposition in structural trap sites to form the deposits.CITATION:Large, R R, 2015. Orogenic gold deposits – a two-stage process of gold enrichment, in Proceedings PACRIM 2015 Congress, pp 335–340 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015