Search Documents

By R Jia, J T. Waldram

"The Caijiaying lead zinc mine is located in China, north-west of Beijing, in Hebei Province. The region experiences severe winters, below -35°C, and warm summers, up to 30°C. The mine and concentrator commenced operations in the second half of 2005 with a conventional tailings disposal system consisting of a tailings dam with peripheral ring main discharge and central water recovery. A second similar dam sharing one common wall was added later. In view of the extreme winter conditions tailings lines and ring mains plus spigots, together with return water lines, require insulation and electrical trace heating. The volume of process water trapped as ice in the tailings dam ponds each winter is significant. This seasonal variation presents a major difficulty in the management of process water availability. Although Caijiaying is an underground mine there was no backfill plant at the start of operations. As plant throughput increased more quickly than originally anticipated, tailings storage capacity became a prime concern. The construction of a backfill plant in 2007 reduced the pressure on surface tailings storage area requirements, but as suitable land on which to construct further tailings storage was both expensive and difficult to acquire, a more efficient use of the available area was required. Dry tailings storage, where flotation tailings are filtered to provide an immediate return of process water plus ‘dry’ tailings filter cake for stacking, provided an answer to both the land area required, and the water management difficulties. The paper details the reasoning behind the change and the benefits obtained at Caijiaying by moving from ‘wet’ tailings storage to ‘dry’ tailings storage.Citation:Waldram, J T and Jia, R, 2016. Caijiaying Dry Tailings Storage, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 379–382 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By R L. Grogan

Regulators of deep-sea mining projects are becoming increasingly hesitant about the concept of adaptive management as a tool to facilitate compliance and continuous improvement. Adaptive management is a relevant and useful instrument to ensure that the mine plan is successfully implemented throughout the life of mine, in parallel with optimum environmental performance and compliance.CITATION:Grogan, R L, 2018. Adaptive management in deep sea mining – looking like you know what you’re doing when it’s never been done before, in Proceedings Life-of-Mine 2018, pp 20–22 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By M Rauer

With a worldwide growing population the demand for higher living standards, food and the development of new technology is rapidly rising. To allow for a continuous growth, larger quantities of minerals and raw materials are needed at a faster pace. Different methods have been developed to access or tap ore more quickly, such as improved drill and blast operations, mechanical mining methods using equipment such as roadheaders (RH), longwall miners and other technical equipment. Another possibility to access and develop mines faster is the use of a tunnel boring machine (TBM).The historical usage of TBMs is surprisingly long, but the opportunity for technology adoption by the majority of worldwide mining companies remains largely untapped. Dozens of full face TBMs have been used by mines around the world, including two that will begin operation soon in Australia. TBMs have been used to safely and rapidly gain access to the orebody, or to expand access to the orebody to increase output by running a TBM along the edge of the orebody for several kilometres. These machines have also been used for ventilation and for conveyor tunnels for ore removal. They have been used to quickly excavate long and winding declines giving access to an orebody at several levels in a short period of time.Tunnel boring technology can be used for mine declines, mine access tunnels and all sorts of different mine designs and set-ups. TBM technology simply needs to be adapted to the mine conditions and, if manufacturers are involved early on in the planning process for mine development, the operation can be very successful. In some cases, historically typical mine designs may need to be re-thought.One mine, the Stillwater Platinum mine in Nye, Montana, is currently employing its fourth TBM in 25 years. Two were used to create tunnels running alongside the orebody, rapidly expanding access to the orebody in many locations for increased output. Two were used to create parallel access tunnels to a mine expansion at the East Boulder orebody; one tunnel is for conveyor haulage and the other for vehicular access. TBMs have been employed successfully many times to rapidly drive vehicular decline tunnels to multiple mine levels, such as at the San Manuel – Magma Copper mine in the USA. While TBM technology may not seem to be optimal for every mine, these success stories show that the method can provide vast benefits for the right projects.Early use of TBMs in extremely hard rock metal mines, in the 1960s and 1970s, had limited success since performance was low. However there have been great improvements made over the years in the strength of rock which can be excavated by TBMs with high performance. Other important improvements involve the provision of a safe work environment, safely and rapidly supporting the rock and predicting geology ahead of the TBM.This paper will briefly note the more than 20 TBM mining projects and highlight some notable successes. It will then go on to give a status report on the two active TBM mining projects in Australia and the difference between a TBM operation versus other excavation methods such as drill and blast (D&B) or RH excavation.CITATION:Rauer, M, 2014. Tunnel boring machines in mines – a?brief review of past use with a status report on use today in Australia, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 663–670 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

It is very rare in the underground hard rock environment to find a deposit that is ideally suited to a specific mining method. Usually the irregular shape of the orebody will allow the deposit to be extracted by more than one mining method. During the prefeasibility stage, a number of conceptual mine designs are generally evaluated to see which offers the best method of extraction for the deposit. The selected method is usually based on key decision criteria such as the overall extraction of the orebody, the amount of metal produced annually and the unit cost of production. Often the prefeasibility study document will state that the project has an NPV of æxÆ million dollars. This statement can be made without any quantitative consideration of the likely risks of the mining methods reviewed or the level of confidence in the estimation of the NPV. By assigning a probability of failure to each component of the mining cycle a measure of the risk for each method can be determined. One mining method may provide the highest NPV when it is performing well, however, there may be a higher risk of a major failure impacting on the performance of that method, eg the failure of a mass blast of a crown or rib pillar. This paper will present a flowsheet approach to the use of risk analysis for determining the likely production rates of different mining methods. This framework allows the annual metal output to be estimated and from this the NPV for each method. A level of confidence can be applied to the estimated NPV for each option. An example will be presented on how this technique has been used within the Normandy Group.

Jan 1, 1998

By D Stacey, J Matthews

Hunter Valley Operations in partnership with Orica Explosives designed a process to optimise coal extraction at depths greater than 65 m below the Hunter River in a safe and cost effective manner. The process involved a team approach to investigate the relationship between geology, mining sequence, vibration and blasting methods adopted. From this an optimum method for uncovering the coal was developed.

Jan 1, 2001

By S Dunham

For decades we’ve been focusing on reconciliation as a tool to validate mineral resource estimates. And for decades we’ve been misleading ourselves. The concept of reconciliation is simple. Predict, measure, compare and assess the quality of the prediction. This four-step process reflects the ideas of statistical process control and the plan-do-check-act cycle of Shewhart and Deming fame and our intuitive understanding of using system feedback to improve performance. In an ideal world where data is robust and dense this type of feedback loop can be useful. In the mining industry however, there are some fundamental flaws with the conceptual framework. At almost every stage of the process from pre-estimation through to final production the mining system is plagued by material challenges with data and measurement quality and quantity, system delays, and losses from a supposedly closed system. These issues can and do impact on the benefits sought from reconciliation. Instead of providing feedback leading to improved estimation, reconciliation can result in poor decisions, distracting investigations, and exacerbate the noise in an already noisy system. Before we can rely on reconciliation as a management tool, we need to address the multiple challenges present in our everyday practices. Some of the most critical issues are addressed in this paper.

May 24, 2023

The mill area of PT Freeport Indonesia is located in a valley surrounded by steep natural slope, characterised by extreme topography with mountains rising to above 4500 m within 100 km from the seashore. The valleys are deeply embedded into the mountainous terrain and bordered by steep natural slopes. Vertical or overhanging lime walls are interrupted by steep vegetated screen sections containing accumulated loose material from weathering processes and ancient rock falls and/or debris flows/avalanches. The climate can be best described as alpine subtropical with an accumulated rainfall of more than 5000 mm per year. Occasional snowfalls and superficial freezing above 4000 m elevation leads to heavy weathering of the superficial rock layers and along open joints and fractures. The mill area is a crucial and strategic infrastructure for the entire mining operation which is best characterised as a high density industrial area with facilities including water tanks, power generators, crusher, and concentrating facilities including office buildings and workshops as well as access tracks to the underground mining blocks. Considering the local topography, the restricted space conditions and the number of technical installations, the facilities are likely to be affected and highly vulnerable to rock fall from the surrounding slopes. In order to minimise the rock fall hazard three rock fence barriers area were constructed at the mill area. The 7.5 rock fence barriers were designed with the maximum capacity of 5000 kJ. These are the largest capacity of rock fall barriers ever constructed in Indonesia. The total length of the barriers for the three locations was 126 m. The biggest challenge of this project was the construction of the barrier at West Gulley, which was constructed at 300 m above ground level. For this site, construction access was undertaken using helicopter. This presentation discusses the design of the mitigation structures as well as the construction approach and stages of the barriers. Please note: This paper is abstract only.

Nov 25, 2010

By A A. Roberts, R F. Dewhirst

"Extensive literature surveys, research in the project environment and personal experiences both within and consulting to project teams have revealed some consistent ‘people factors’ that contribute most to ultimate project success. Outside of purely technical and business case issues, there are a small number of leadership characteristics – probably only ten – that if correctly applied can positively leverage a team’s impact on project success.Of the top seven project success characteristics that were consistently highly rated in a recent study, five of them were around leadership. The authors have focused on this topic, noting that good leaders need to display the following traits:passionate commitment to deliveryconsistent modelling and reinforcement of correct values and behaviourfocus on managing relationships well and energising teams and individualscarefully clarifying project vision from front-end loading stages onwardseffective decision making.Not every project manager can and does practise these behaviours all of the time, but being aware of them and receiving training or facilitation in improving their application of these skills can equip project managers with the essential tools to markedly improve their own performance and that of their teams.This paper draws upon experiences in the field and provides lessons – both good and bad – to illustrate. As well as examining leadership traits, the way in which a leader can establish, organise, motivate his or her team and ultimately lead them to success is examined. The paper shares methodologies that have been successfully used to track status within a team and generate appropriate recovery plans where required.In particular, the paper will examine a case study based on an amalgamation of real project issues in some challenging situations using virtual teams (ie physically distant teams located in different centres) to illustrate the importance of strong and positive leadership in achieving success across geographies, time zones and languages.CITATION:Roberts, A A and Dewhirst, R F, 2016. Leadership in projects – a recipe for success, in Proceedings Project Evaluation 2016, pp 49–58 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By B Chapman, B Gaida, L Drowley

The 372 MW Ulu Jelai Hydroelectric Project is a peaking power scheme located in the Cameron Highlands, Malaysia. The main features of the project include an 84 m high roller compacted concrete dam; two weirs which divert flows from adjacent catchments via transfer tunnels into the main reservoir; an underground power waterway; and an underground power station complex comprising three large caverns with connecting tunnels approximately 240 m below surface level. The project includes approximately 25 km of tunnels excavated in fresh granite rock mass with some distinct shear zones of weaker material. The majority of the tunnels are being excavated using drill and blast, with the two transfer tunnels being excavated with a tunnel boring machine (TBM).This paper focuses on the design and construction of the Telanok underground power station complex and also some aspects of the design for the headrace tunnel. Topics covered include geological site investigations including in situ measurements of rock stresses; development of a geological model and parameters for rock support design; three-dimensional modelling to assess interactions between the caverns to optimise rock support; design of a rock anchored crane beam; construction of the caverns and design of the unlined headrace tunnel taking into account hydraulic jacking and operational pressure fluctuations.CITATION:Drowley, L, Gaida, B and Chapman, B, 2014. Design and construction of large caverns in granite – Ulu Jelai Hydroelectric Project, Malaysia, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 361–368 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By J Stiefenhofer

"*This is an abstract only*Construction of geological models for kimberlites has historically largely been based on visual volcanic textures and features, with chemical data only collected on an ad-hoc basis depending on the level of perceived complexity observed in the geological data. The focus of this paper is a high-level view of the impact an initial absence (or lack) of relevant chemical data had on two kimberlite resource models as well as how the magnitude of the problem increased once the resource estimation process commenced (Stiefenhofer, 2013). The impact of ignoring chemical data on a project assessment where micro-diamond estimation techniques are employed, is also discussed. Resource estimates based on micro-diamond data are critically dependent on the use of the correct geological model since stationarity of the size frequency distribution is key to the generation of correct grade estimates. A multilevel approach is advocated where the volcanological/visual model is verified using chemical data and both are in turn verified by the diamond data.CITATION:Stiefenhofer, J, 2013. The use of chemical and metallurgical parameters to enhance the economic value of kimberlite resource models, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013, pp 101-104 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 29, 2013

By M J. Dunn

The geotechnical model is the cornerstone of any mining geotechnical design and as such the confidence level and reliability of the geotechnical model is paramount. The geotechnical model confidence level needs to be commensurate with the level of design that is being applied or study that is being undertaken. The geotechnical model is made up of several components and the reliability of the data underlying these components ultimately determines the reliability of the geotechnical model.Data reliability is linked to the quantity of data collected, the spatial distribution of the data collected, quality of the data collection and the interpretation of the data. In a typical project, there is an opportunity to improve data reliability through the scoping, prefeasibility, feasibility and final design and implementation stages.Currently, very little quantitative guidance exists in the literature on assessing the confidence level of geotechnical studies, although there have been attempts by various authors (Haile, 2004; Haines, Swart and Kruger, 2006; Read and Stacey, 2009; Dunn, Basson and Parrott, 2011) to qualitatively describe what level of geotechnical data is required. Recently a number of authors (Read, 2013; Fillion and Hadjigeorgiou, 2013; Thomas, 2013) have outlined methods that could be applied to assess the reliability of some types of geotechnical data that are used in the development of geotechnical models.This paper briefly discusses some of the factors influencing data reliability and the geotechnical model confidence and some of the tools available.CITATION:Dunn, M J, 2014. Geotechnical models and data confidence in mining geotechnical design, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 127–134 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By S Juras

The terms measured resources and proven reserves denote the highest level of estimation confidence in all of the major classification schemes. But what do they really bring to today’s project or mine with respect to production planning and expectations? Initial reserve declaration does not need measured resources, just indicated resources. Economic viability of a project is assessed on total reserves with nary a bonus for the amount of proven reserves. Production plans are based on grade and tonnage goals that may only coincidently correspond to proven reserves. So are the measured and proven categories still relevant? Historically, and almost exclusively in underground mines, companies only allowed mining in areas of proven reserves. Some companies still follow that philosophy. But many others will mine a mixture of probable and proven reserves without hesitation. Also what of the undeveloped project in a new district – what is to be made of their declared measured resources and proven reserves? Measured resources are commonly set either by some type of proximity to data scheme or a matter of ‘feel’ based on the qualified person’s experience. The parameters for reserve conversion focus on the project as a whole and then a portion becomes classified as proven reserves almost solely based on whether the resource category is measured. So should the mining industry continue to use these categories of resource and reserve classification? This paper will present arguments about making these categories once again more relevant. A more disciplined usage of these categories may re-introduce their relevancy in public disclosures of resources and reserves. As well a more consistent usage in operations may lead to increased confidence in managing production targets and costs.

Aug 22, 2011

By H Fletcher

Iron Ore Holdings Ltd (IOH) is an emerging junior iron ore company that is actively developing projects in the Central and Western Pilbara region of Western Australia. IOH commissioned URS Australia Pty Ltd (URS) in mid-2008 to prepare environmental assessment documents for the Phil’s Creek Project, which was rapidly moving into the development phase. This project comprised a small open cut iron ore mine that was expected to deliver approximately seven million tonnes over a five year mine life.IOH faced several challenges in the environmental assessment process for the Phil’s Creek Project. Although the Phil’s Creek Project attained approval but has now been placed on hold, it is a useful case study to discuss these challenges and how IOH addressed them. Several important lessons were learned through this process that can assist other proponents in addressing environmental challenges in a constructive and proactive manner.One major challenge faced by IOH related to the endangered northern quoll (Dasyurus hallucatus). Another challenge was the unusually high species richness of troglofauna recorded within the project area, with several species initially known only from within the proposed pit footprint.Meeting and overcoming these challenges has provided IOH with an increased understanding of the level of input required for consultation with government departments regarding environmental assessments, and this should stand the company in good stead for developing future tenements. Challenges in regards to the environmental assessment process may be faced during future developments, but IOH’s experiences to date and the lessons learned from the Phil’s Creek Project, will help pave the way for successfully overcoming them.

Jul 11, 2011

By P Card

Some project managers accept unsatisfactory economic evaluation modelling because they are unaware of what constitutes good practice. They tend to leave it to the evaluation specialist or others to decide. The AusIMM has published on its website a draft set of guidelines for technical economic evaluation which will allow these project managers to take control and demand worldÆs best practices.The style of the guidelines is described and the source of a worked spreadsheet example in Excel is given.Economic evaluation in project management is described. A simple test for the acceptance or rejection of evaluation work is offered. The nature of modelling and evaluation in each of the three study phases of concept, prefeasibility and final feasibility are described. Suggestions on the selection of specialists for each phase are given. The three levels of evaluation thinking are described, namely, modelling, valuation and evaluation. Finally the meaning of æfinancial analysisÆ is explained.The conclusion is that æthe role of an economic evaluation specialist is to create models and evaluations for the whole project team to readily understand and use: it is not to create models for his/her own useÆ.CITATION:Card, P, 2012. What project managers must demand from an economic evaluation!, in Proceedings Project Evaluation 2012 , pp 173-176 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012

By S Viviers, G Ratner

Ventilation is part of all underground mine operations and is undertaken in order to introduce fresh, cool air to the workings and to remove stale, affected air. It is problematic to obtain efficient and accurate estimates of volume flow and static pressure in the installed operational configuration for the auxiliary axial flow fans.An empirical method was developed to estimate the static pressure and volume flow through a calibrated differential pressure port on axial flow fans. Prior to shipping, each fan is performance tested according to BS 848 (ISO 5801) to establish the fan performance curves. In addition to the standard required parameters captured to fully describe the performance, the differential pressure is measured across the fan rotor to enable correlation with the characteristic fan curve.The method was implemented on a ruggedised tablet PC platform. This compact platform is then used to calculate the volume flow rate from the differential pressure sensor measurement input via a USB port. The result is a real-time measurement of volume flow and operating point of the fan system. This can be used effectively in overall modelling of the mine auxiliary ventilation systems and calculation of system resistance could provide a health indication of the fan and duct system.CITATION:Ratner, G and Viviers, S, 2013. Underground auxiliary ventilation monitoring and diagnostic system, in Proceedings The Australian Mine Ventilation Conference , pp 57-62 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By N Meadows, M Rodriguez

A 200 000 tpa heap leach demonstration plant was approved by the Murrin Murrin Joint Venture (MMJV) in December 2005 and engineering commenced in January 2006. The demonstration plant will utilise stockpiled ore reject material (æscatsÆ) and extract nickel and cobalt. Limited production from the demonstration plant is expected by the end of 2006. The demonstration plant will enable the company to fully investigate and understand all associated technical issues over the next 12 to 18 months, including the potential to expand the heap leaching operation to a commercial scale. In parallel, the MMJV will continue a research and development program to improve and expand the application of its heap leaching technology.

Jan 1, 2006

By P Bonniwell

As a part of the Newcrest, Telfer Expansion Project, a consortium of Australian, Canadian and South African Mining Contractors in joint venture have been contracted to develop the hoisting shaft. The parties namely; Byrnecut Mining Pty Ltd, Murray and Roberts RUC and Thyssen Mining Construction of Canada Ltd have combined their individual expertise to excavate the shaft. There is a particular emphasis on the use of proven shaft sinking techniques from North America and in particular integrating electric hydraulic drilling equipment and personnel from the Canadian Mining industry. The Telfer hoist shaft when completed will have a finished diameter of 7.1 metres and extend to a depth of 1170 metres below the collar. The shaft will be fully concrete lined and will later be equipped for hoisting ore from the Telfer deeps at a rate of five million tonnes per annum. The shaft when completed will be the largest shaft ever completed in Australia on a volumetric basis. This paper will examine the technical aspects of the shaft sink, as well as exploring the integration of personnel and equipment from the frozen prairies of Saskatchewan, Canada into an operation in the Great Sandy Desert of Western Australia. What are the spin-off benefits for the development of other shafts within Australia?

Jan 1, 2005

By K Ehrig

Two irrefutable facts in geology and metallurgy are: ore deposits are comprised of variable mixtures of minerals which are systematically distributed throughout the deposit, and mineralogy exerts the primary control on metallurgical performance. If the distribution of process critical minerals can be quantified and mapped, then a logical assumption is that metallurgical performance can be predicted across the deposit.Olympic Dam is a +9 billion tonne Fe-oxide Cu-U-Au-Ag deposit which is hosted entirely within a magmatic-hydrothermal breccia complex consisting of over seventy ore and gangue minerals. Each has a unique set of metallurgical performance properties. Fortunately, 15 of the 70 minerals accounts for >98 per cent of the total rock mass.The mineral mapping journey commenced in the early drilling days shortly after the discovery of Olympic Dam in 1975. Geologists quickly recognised that the copper-iron sulphides had a predictable zoned distribution. However, geological models reflected the presence or relative abundances, not quantitative concentrations, of the minerals. This type of mineral mapping remained relatively unchanged for ~20 years and was of limited use outside of geology.Several things changed during the mid-1990s: assaying costs decreased significantly, instruments capable of automatically measuring mineralogy became readily available, the recognition of two quantifiable relationships at OD (ie mineralogy is a function of chemical composition (ie assays), and metallurgical performance is a function of assays, mineralogy, texture and process conditions. The linkage of metallurgical performance to mineralogy and mineralogy back to assays allows for every assayed sample in the resource model to be assigned mineral concentrations and metallurgical performance predictors. At Olympic Dam, block models (ie 3D maps) are routinely produced for 27 elements, density, 15 process critical minerals and greater than 50 metallurgical performance variables. These geometallurgy-enabled resource models are used for mine planning, process plant design and process optimisation studies. *This is an abstract only. No paper was prepared for this abstract.*

Sep 5, 2011

By C N. Hatton, K Ward

Tailings operations are inherently reactive as operations personnel continuously contend with a concentrator reject feed (tailings) transient in physical and engineering properties, which places a constant constraint on capital and operational spending. It requires a unique skill set to manage the prescribed distribution of tailings under unenviable conditions. Enter the tailings operator, an oftenundervalued commodity and untapped resource that can provide benefits beyond the rigors of dayto- day operational support. Experience consistently demonstrates that skilled and committed operators can serve a vital function in the safe construction of a tailings storage facility. It takes a village to raise a tailings dam. An important part of this process is establishing a culture of operational accountability and ownership. Operator development training is nothing new. However, we find that many of the intrinsic operator skills are left unexploited, and an operator's experiential knowledge base and creativity are commonly overlooked and underutilized. With proper training and guidance, these skills can be harnessed, contributing to safe dam operations. Operator engagement, when properly facilitated, provides tangible benefits ranging from improved tailings engineering properties to reduced closure costs. One important benefit is helping transitioning tailings management from reactive to proactive. There are many processes involved in the reactive to proactive transition process. One element of that process includes engaging operators in the tailings management process and facilitating legacy ownership. The core of operational legacy ownership is measured and described using five-stage operator engagement rubrics. Levels of operator engagement are presented with a description of the incremental benefits of each stage. An important part of legacy engagement is providing the tools to operators necessary for managing the tailings. Therefore, the approach identifies specific methods used by operations personnel to control tailings distribution and in-place properties. The end goal of leveraging operator engagement is to facilitate committed ownership and transition tailings management from an inefficient, reactive process to an improved, cost-effective, proactive practice.

Jul 1, 2021

By E R. Ramanaidou, C Tessarolo, M Verrall

Garnierite mineralogy in saprolitic ore of the Goro lateritic nickel deposit, New Caledonia , was investigated using X-ray diffraction (XRD), optical and scanning electron microscopy (SEM) and electron microprobe (EMP) analyses. These conspicuously, green-coloured phases occur either as submillimetre to centimetresized veins or as æbookletsÆ arranged in, macroscopic (subcentimetre sized), accordionlike structures supported in an undifferentiated matrix of mixed ÿ7+ and ÿ10+ phases. Within the veins, nickel for Mg solid solution increased from ten wt per cent NiO at the edge to 34 wt per cent NiO at the core, with vein edges comprising Ni-kerolite with <1.5 Ni per formula unit (pfu) grading to pimelite containing >1.5 Ni pfu at vein cores. The æbookletsÆ comprised nTpouite of formula, (Mg0.67Ni1.59Fe3+0.05)(Si2.17Al0.22)O5(OH)4 and averaged 30 per cent NiO. SEM element mapping highlighted the distribution and mineralogical association of Ni and Mg and emphasised the inverse relationship between Ni and Mg at the macroscopic (thin-section) scale. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008