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By D Schwab, R M. Tosdal

The Quesnell-Stikine arcs, in the Canadian Cordillera, are host to Triassic and Early Jurassic alkalic porphyry Cu-Au and calc-alkalic porphyry Cu-(Mo-Au) deposits formed outboard of ancestralNorth America in island-arc tectonic settings (McMillan, 1991). The majority of the alkalic porphyry Cu-Au deposits are products of a discrete magmatic event at the end of the Triassic, with a second and smaller event in the Early Jurassic (Mortensen, Ghosh and Ferri, 1995). Of the Triassic complexes, the Galore Creek alkalic intrusive suite is one of the largest and most silica-undersaturated intrusive complexes, and host to the most significant undeveloped alkalic porphyry Cu-Au resource in North America (Lang, Stanley and Thompson, 1995). Because of the common presence of feldspathoidal-bearing rocks in the complex (Enns et al, 1995), Galore Creek likely represents an end member example of the alkalic porphyry Cu-Au class. The Galore Creek alkalic Cu-Au-Ag porphyry district, located in NW British Columbia (Canada), contains 12 mineralised prospects (Enns et al, 1995; Micko et al, 2007; Schwab et al, in press) with a total measured and indicated resources of 785.7 Mt at 0.52 per cent Cu, 0.29 g/t Au and 4.87 g/t Ag (NovaGold Resources Inc, February, 2008). The Central Zone is the largest and best delineated. Other economically important mineralised centres include the South-West, Bountiful, West Fork and Junction deposits. The South-West Zone, the focus of this contribution, is a Cu-Au-Ag breccia-centred deposit with a measured and indicated resource of 69 Mt grading 0.42 per cent Cu, 0.69 g/t Au, 2.67 g/t Ag. Hosted in brecciated intrusive rocks, the South-West Zone is distinctly younger than the Central Zone and most of the other mineralised centres (Enns et al, 1995; Schwab et al, in press). The South-West Zone therefore preserves the late stages of hydrothermal evolution at Galore Creek. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Revy T

A testwork program aimed to improve the assaying of underground face samples established that for an Accelerated Cyanidation Extraction using the LeachWELLTM 60X catalyst, followed by an Aqua Regia finish (to quantify non-cyanide-extractable gold): ò Assay results (including the aqua regia finish) from a full set of samples from one underground face can be returned within four hours. ò The reagent dose to make the method simple and 'bullet-proof' is 8 gm LeachWELLTM 60X and 20 gm NaCN per 200 gm sample (30 per cent solids). Pulverising is to 90 per cent passing 75 micron (compared to the standard of 90 per cent passing 150 micron), and cyanidation is completed within one hour - however both might be further optimised. ò The LeachWELLTM/Aqua Regia results demonstrate that Fire Assays suffer from a significant nugget effect which makes the Fire Assay data relatively unreliable. ò Original costs, specific to Bannockburn (viz including an Aqua Regia finish), handling approximately 20 000 to 25 000 per annum is estimated to be $5.40, ie about one-third less than fire assaying. Optimising is further reducing these costs. It is estimated that the LeachWELLT"'/Aqua Regia assay procedure has reduced the probable error limits of any given assay of this ore from the range 0.74x to 1.36x for Fire Assay, to an appreciably smaller range of 0.90x to 1.11x. Thus for a cut-off grade of 1.60 g Au/t, samples with Fire Assays ranging up to 2.18 g Au/t have 25 per cent chance of being below cut-off, while samples with Fire Assays as low as 1.18 g Au/t have an equal chance of actually exceeding cut-off grade. This 1 g Au/t range in uncertainty is generally unacceptable for many practicalgrade/tonnage relationships. By contrast, using LeachWELLTM + Aqua Regia assays, the estimated corresponding limits are 1.44 g Au/t and 1.78 g Auk respectively - a far more tolerable 0.34 g Au/t range of uncertainty. Subsequent data has demonstrated that sufficient accuracy for grade control is achieved by Accelerated Cyanidation alone, further halving the cost of assays.

Jan 1, 1994

By G Solly, S Parsons, P Leevers, S Ni

Hematite ore has been mined in the Southern Middleback Ranges as blast furnace feed for the steelworks at Whyalla, by what was then BHP, since 1991. With the floating of BHP Integrated Steel as OneSteel in 2001 and the subsequent loss of key mining personnel, breakdowns in grade control methods and procedures occurred. These were compounded by changes in orebody characteristics and grade distribution leading to poor reserve recovery and poor grade control, both which resulted in loss of control of ore specification and severe deviation from the mining schedule. As a result, a total review of grade control, mining method and scheduling procedures was undertaken as well as a review of contractor quality assurance. It was found that sampling methods were poor and unrepresentative, grade control blocking processes were outdated and did not reflect the geology of the deposit, the ore mining method was outdated and did not respect the geometry of the orebody, reconciliation methods were being completed globally and were not reflective of individual areas of the deposit, and that deviations from the mine plan were occurring due to access to high-grade areas outside the schedule in order to bring stockpiles back on grade. Based on these findings, updated sample splitter systems were fitted to drill hole rigs, double bench sampling was implemented (2 + 4 m samples as opposed to 1 + 8 m sample) and a three-dimensional cellular grade control system introduced to better reflect the geology and orientation of the deposit. At the same time ore mining was changed from front end loaders mining on 8 m benches to excavator mining on three lifts on 8 m benches; this aided selectivity and respected the geometry of the orebodies aiding cleaner recovery. Reconciliation is now completed on a blast-by-blast basis, which allows for quick and easy identification of poorly performing areas of the resource model that can then be incorporated back into resource model updates. Regular daily and weekly meetings are also held with emphasis on the mining schedule to ensure no deviation from the schedule in the long term. These improvements have resulted in a lift in reserve recovery both globally and locally associated at the same time with improvement in grade.

Jan 1, 2005

By M Darvall And R Fare, D Dormer

The Argo Archaean lode gold deposit is hosted within a structurally complex shear zone system, 70 km south of Kalgoorlie, and 3 km west of the crustal-scale Boulder û Lefroy Fault. Argo is an active underground mine currently producing at a rate of 120 koz pa with a Probable and Proven Reserve as at December 2005 of 2.19 Mt at 5.94 g/t Au (419 koz), a reduction on the December 2004 Probable and Proven Reserve of 4.58 Mt at 5.74 g/t Au (845 koz). This Reserve is hosted in six separate gold bearing lodes within the Argo shear system. Presently, a further six subeconomic shears are recognised. The 2005 Reserve figure represents a reduction of 426 koz compared to the 2004 Reserve as a result of a thorough review of the geological interpretation/resource model, and engineering factors applied to the Resource/Reserve, and depletion due to mining. Year on year Resource/Reserve figures at Argo had gradually increased as additional information on the system became available and mining methods were increasingly resolved with early production. The portal for Argo underground mine was cut in June 2002 within the highly profitable Argo open pit. The proposed æAvocaÆ bottom-up mining method required extensive lead time between development and the commencement of stoping in April 2004. During development considerable additional complexity in the Resource was encountered. Additional structures were identified, and complex splay interactions affecting the geology impacted on development. Intensive concurrent exploration in the footwall to the main lode during this period was the main cause of the increase in the Resource/Reserve figures during early development. As development progressed, lower grade continuity was observed than was previously interpreted. At the same time, drilling of deeper portions of the deposit and subsequent reinterpretation of the geological model significantly reduced strike lengths of economic mineralisation. Radical changes to the mining methods were required to improve productivities and to satisfy geotechnical considerations. The changes altered the engineering factors applied, which resulted in a reduction in the Reserve figures.

Jan 1, 2006

By Allnutt S. L, Carswell J. T, Mutton A. J

The Dugald River Zn-Pb-Ag deposit occurs within the complexly deformed and metamorphosed sediments of the Middle Proterozoic Cloncurry Terrane, Eastern Succession, Mount Isa Inlier. The sedimentary sequence comprises a thick package of variably carbonatic argillitic and siliciclastic sediments of the Corella Formation, Lady Clayre Dolomite and Knapdale Quartzite. A slate and calc-argillite unit locally referred to as the Dugald River Slates is the host to the economically significant deposit. The deformational history of the Dugald River area involved three phases of ductile deformation. The present geometry of the Dugald River Main Lode is recognised as a strike extensive steep westerly dipping tabular sheet, within which a steep north westerly plunging zone of pronounced thickening is evident. This zone is interpreted to have formed during folding via remobilisation of the sulphides into a shoot-like body, the geometry of which was controlled by stretching associated with the folding. Further modification of the shoot and sulphide re-distribution has resulted from late phase transgressive shears. The sulphide mineralisation is characterised by three distinctive sulphide types, laminated, banded and breccia, the distribution of which define two broad zones. The northern zone is a narrow I - 5 m thick stratabound unit comprising finely laminated and banded sulphide mineralisation within a well bedded fine grained argillite sequence. This is part of the Lady Clayre Dolomite sequence and is a predeformational precursor form of mineralisation. The southern zone comprises the thickest development of mineralisation (up to 30 m) characterised by slate-sulphide breccias and veins derived from complex polyphase remobilisation of the sulphide mineralisation. It is this zone which forms a stratabound locally transgressive body within the high strain Dugald River Slates and which contains the main body of economic mineralisation. Sulphide mineralogy comprises sphalerite, pyrite, pyrrhotite, galena and traces of chalcopyrite, pyrargyrite, tetrahedrite, marcasite and arsenopyrite. The present resource for the Dugald River deposit stands at 38 Mt grading 13.0 per cent Zn, 2.1 per cent Pb and 42 g/t AS. The Dugald River Zn-Pb-Ag deposit is regarded as an example of a syndiagenetic stratabound sulphide accumulation which, as the result of polyphase deformation and upper greenschist to middle amphibolite facies metamorphism, has undergone extensive remobilisation and Rccrystallisation.

Jan 1, 1993

By Andrews JRG

Chrysotile asbestos is a valuable resource. Used as a reinforcement in asbestos cement, products are obtained which are cheap, are not attacked by vermin, do not rot or support growth of fungi and are unaffected by water or humid conditions. Such products are of great value in the developing countries where inexpensive and durable building materials and pressure pipe are very important to development, housing and water supplies. Concern over the adverse effects of inhaling asbestos has led to the introduction of increasingly stringent controls world wide on the quantities of airborne asbestos per- missible in the occupational situation. Wet processing has the potential for virtually eliminating the environmental concerns with asbestos dust both in fibre production and in the materials handling section of the manufac- ture of asbestos cement products. In addition, high efficiencies associated with wet process- ing mean that better yields are obtained and that the tailings which are dumped have a lower residual asbestos content. Since early 1977, ICI Australia and Woodsreef Mines have been engaged in a programme of research to develop and evaluate a wet mill- ingprocess to produce, from ore and existing tailings, high grade fibre suitable for use in asbestos cement products. The process has been developed through microscopic studies, labora- tory bench scale experiments, work in a small scale semi-continuous plant and product evalua- tion on experimental size Hatschek asbestos cement machines. A prototype mill with a normal feed rate of 1z tonnes per hour and capable of producing pipe grade asbestos from Woodsreef ore has been constructed and was operational from January, 1982 to July, 1983. A range of asbestos cement products have been made successfully on full scale Hatschek machines using fibre from ore and tailings milled in the prototype mill. Economic evaluations indicate that a wet process mill would be cheaper to build, operate and maintain than an equivalent dry process plant. A commercial plant has been designed 1. Manager New Process Development, Woodsreef Mines Limited, Barraba, Australia. 2. Senior Lecturer, Department of Chemical Engineering, Monash University, Vic, Australia. formerly Senior Research Officer, Research Department, ICI Australia Limited

Jan 1, 1986

By Groves D. I

The Norseman-Wiluna Belt (Fig.1) is a richly mineralized (production 1900 tonnes Au), Archaean greenstone belt, up to 800km long and 200km wide, which forms the major part of the Eastern Goldfields Province within the Yilgam Block. The Belt evolved ca. 2700 Ma ago as an oblique-slip mobile belt between flanking portions of an older greenstone terrane. Volcano-sedimentary successions in the Belt represent two distinct tectono-stratigraphic associations. Sequences of metamorphosed caic-alkaline intermediate to silicic volcanic rocks interlayered with tholeiitic basalts probably represent the remains of a dissected Archaean volcanic arc (or arcs), and sequences composed dominantly of ultramafic to mafic lavas and intrusions, with minor interflow tuffaceous, sulphidic or cherty sediments are interpreted as remnants of the floor of an ensialic marginal basin (Barley and Groves, 1988). Ultramafic volcanism at Kambalda has been dated at 2692 ¦ 2 Ma (Claoue-Long et al., 1986). The dominantly volcanic associations are locally overlain by coarse clastic sedimentary succes- sions. The Belt is also typified by major north- to north-northwest-striking fault systems, shear zones, and tectonic lineaments, many of which are traceable for more than 300km. As well as defining the boundaries of the belt, these structures have accomodated much of the regional strain and acted as conduits for hydrothermal fluids during deformation, metamorphism and mineralization. As a result, most of the epigenetic gold deposits in the Belt occur in subsidiary structures related to these fault systems (Eisenlohr et al., 1988). Deformation involved oblique compression resulting in a closely spaced network of low-angle faults (thrusts) as well as upright folds and oblique- to strike-slip faults (Archibald, 1987; Veamcombe et al., 1988). This was accompanied by regional metamorphism and granitoid emplacement. At Kambalda, regional deformation and metamorphism were synchronous with the emplacement of the Kambalda Granodiorite which has been dated at 2662 ¦ 4 Ma (Hill and Compston, 1986), approximately 30 Ma after volcanism.The tectonic history and style of deformation of the Norseman-Wiluna Belt are similar to those of Phanerozoic oblique- slip mobile belts at continental margins, which are also a major source of hydrothermal gold mineralization.

Jan 1, 1988

By M Araos, I Onederra

A novel explosive formulation that substitutes the use of ammonium nitrate (AN) with hydrogen peroxide (HP) as the main oxidising agent has been developed and tested as part of an Australian Coal Industry Research Program (ACARP) project. The main objective was to provide a step-change solution that has the potential to completely eliminate NOx fumes in blasting. The development of this HP/fuel-based explosive started with a comprehensive detonation characterisation program, consisting of unconfined velocity of detonation (VOD) measurements of samples at different diameters, densities and void sensitisation techniques. VOD results showed that the HP/fuel-based explosive mixtures behaved similarly to non-ideal commercial explosives; in that way mixtures could be tailored to achieve specific detonation performance targets. The next stage of testing in this development involved preliminary confined tests to evaluate the rock breakage potential of the HP/fuel-based explosive mixtures. Fully instrumented single-hole tests were conducted in a limestone quarry. Results from these preliminary trials confirmed the rock breakage performance of HP/fuel-based explosive mixtures. The confined VOD measured in one of the tests was 5100 m/s in a 102 mm diameter blasthole at a density of 0.96 g/ml. The corresponding borehole pressure measurement of this HP charge was 2.61 GPa with a detonation temperature of 2921°C. Based on near-field accelerations, both HP and ANFO charges displayed similar attenuation characteristics in the test conditions. Post-blast observations indicated that the breakage performance of the HP mixtures clearly reflected the in-hole detonation performance measurements obtained, confirming the ability of these explosive mixtures to both fragment and effectively displace the rock mass under evaluation. Further research work continues with the future commissioning of a prototype mixing and delivery unit, the successful completion and analysis of data from multiple-hole trials, and further characterisation work associated with product stability, reliability and performance under different geotechnical conditions.CITATION:Onederra, I and Araos, M, 2015. Detonation and breakage performance of a hydrogen peroxide-based explosive formulation, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 565–574 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By A Kuras

Segmental tunnel linings are becoming more common in Australia. One current project employing a segmental lining is the City West Cable Tunnel (CWCT) in Sydney. The project has been commissioned by Energy Australia and is currently being constructed by Thiess Pty Ltd. The project includes 1.6 km of tunnel boring machine (TBM) driven, segmentally lined tunnel. The majority of the CWCT will be excavated through Hawkesbury Sandstone. The tunnel is required to carry a 132 kV electrical circuit under SydneyÆs central business district (CBD), between Haymarket and Energy AustraliaÆs City North Substation on Sussex Street. The segmental lining has been designed as a 3.2 m internal diameter, 200 mm thick universal ring with six trapezoidal segments. The design and detailing of this segmental lining presents some noteworthy challenges, including exposure to saline groundwater, and the exclusive use of steel fibres for flexural and tensile concrete reinforcement. This paper describes some of the key elements of the segmental lining design. These include:the case for choosing segmental linings over other forms of tunnel construction;the major design checks required of a segmental lining including ground loading, hydrostatic loading, joint bearing, joint rotation, ram loading and the early strength lifting case;the benefits of using steel fibres over conventional steel reinforcement;the design approach used for steel fibre reinforced concrete;the application of 3D computer modelling in the design;the provision for components including connector dowels and gaskets;the design for passive fire resistance; andthe design for durability of steel fibre reinforced concrete in a saline environment. Segmental lining design requires the application of specialist design approaches. Input is required by the construction team, as the methods of demoulding, handling, transportation and installation impact on the lining design. As the segmental lining is functioning as immediate ground support and also a permanent lining, high standards of manufacture and construction quality control are required to ensure that the 100-year design life is met. The requirement for a watertight tunnel means that detailing and installation of the EPDM gaskets is of importance.

Jan 1, 2008

The first 12 m diameter rakeless thickener in the Australian gold mining industry was installed to treat plant tailings at the St Ives gold plant in April 2000. The plant processes approximately 3.2 M tonnes of ore producing about 430 000 oz of gold per annum using conventional crushing, grinding, gravity and carbon in pulp processing methods.The main benefit sought from the thickener was to improve water recovery in the plant and provide water for a 55 000 oz per annum heap leach operation. The thickener design indicated that more than 128 m3/h of overflow water could be returned directly into the plantÆs water circuit, relieving the demand on the borefields. The resultant surplus in the water circuit would then be available for the heap leach project. Based on laboratory and pilot plant scale tests conducted by EIMCO the thickener was designed to handle up to 700 m3/h of tailings slurry (450 tph of solids) with a 40 per cent oxide component in the ore blend. The normal plant throughput is 565 m3/h of slurry (400 tph of solids). Gold mineralisation in most areas at St Ives comprises quartz-sulphide vein and breccia lodes with common albite-biotite-chlorite alteration assemblages. There are well developed supergene gold horizons in the clay-oxide profile above most of the deposits (Osborne, 2002). This results in a wide variety of ore types being treated. At times 40 - 50 per cent of the ore may be oxide in nature. After some commissioning difficulties associated with instrumentation, the thickener has performed satisfactorily although it has not reached its design capacity. The maximum density achieved under normal operating conditions with 20 per cent oxide ore is about two per cent below the design. The thickenerÆs performance deteriorates further with increasing amounts of oxide ore in the blend. The thickener has provided sufficient water for the successful operation of the heap leach and has also provided some down stream benefits for the gold plant by way of pH and cyanide conditioned thickener overflow water.

Jan 1, 2002

By O Otgonbayar, B Bayarmaa, D Batbyamba, S Amar-Amgalan, K H. Natsagdorj, J Nomin-Erdene, B Boldkhuu, T S. Sainzaya

The Argyle deposit in the Kimberley region of Western Australia was the world’s largest accumulation of natural diamonds. Following its discovery in 1979, the mining of associated alluvial diamonds commenced in 1983, followed by the pipe in late 1985. Over the life of the mine to its closure in November 2020, Argyle produced approximately 900 million carats of diamonds. Argyle diamonds are distinctive in having a predominance of brown colours and rare highly-prized pink diamonds, which are a signature of the deposit. The 3D geological model developed from mining and deep drilling shows that Argyle is a composite pipe formed by the coalescence of several steep-sided diatremes, each with their own feeder zones at depth, that were erupted along a NNE-trending fault. The ~1.2 Ga Argyle pipe is comprised of diamondiferous olivine lamproite volcaniclastic rocks and intruded by sparse olivine lamproite dykes. The volcaniclastic rocks are predominantly comprised of unconsolidated quartz-rich lapilli and coarse ash deposits formed by numerous phreatomagmatic eruptions of olivine lamproite magma through Mesoproterozoic water-rich sands and silts. Post-emplacement deformation has tilted the orebody 30° to the north and regional strike-slip faulting has offset, segmented, and elongated the orebody. Recent significant modifications of the geological model resulted from underground block cave operations, producing several critical lessons learnt. Diamond grade and quality reconciliation issues warranted a geological investigation which resulted in the recognition of new volcaniclastic olivine lamproite domains with a broad range of diamond grades, including some very high-grade units. The new lamproite domains had a significant effect on the block cave mining and resultant recovery of diamonds. The new findings enable a more coherent and detailed geological understanding of the volcanic emplacement and paragenetic sequence of the Argyle AK1 pipe. Structural modelling of the deposit also played a major role in the block cave mining tonnage recoveries and daily operations. The re-examination of the geology of the Argyle pipe and the results of this new information reinforces the need for ongoing robust geological work both in the early stages of mining a deposit and continued during the life of the mine.

Mar 22, 2022

The difficulty in screening of ores when the moisture contents reach certain critical levels has resulted in mining circuits using wet processes for screening. While this has been acceptable in past years it is no longer acceptable in certain countries and where the mining company is looking to reduce its impact on the surrounding environment.   Various mining companies have been looking at ways to remove the need of using water, with all its inherent drawbacks and to be able to produce its desired products in a dry process.   This would have the benefits of less environmental impact and cost, (due to not requiring wet processing equipment), less power consumption (reduced equipment needed), no corrosion issues, no contaminated waste waters and reduced maintenance activities.   Until recently this has proven elusive or with technical restrictions with current available acceptable technologies for high capacity plants.   One major mining company began seriously exploring ways to overcome this dilemma so that they did not replicate their current ways of operating for their new expansion plans.   They partnered with Metso Minerals to undertake extensive groundbreaking laboratory test work and provide potential solutions as to how to solve this. The laboratory test work proved interesting enough to design, manufacture and test on the actual mining site a prototype screening machine in the circuit.   This break through in screening technology reduces the environmental impact on the area in which the mine is located by: eliminating the storage and use of water, reduction in energy consumption due to having no pumps in the plant, reduction in plant costs and the upstream affects on the environment process used to manufacture and ship the materials the plant structure is built from, and no large tailings dams to take up land space and affect the environment through groundwater/ water table contamination and the negative effects on animals and ecosystems Laboratory test were conducted and a full size machine was installed at the plant site along side conventional machines. The screen size (2.4 m wide x 6.1 long double deck) was determined by the size of screens currently in operation at the mine. The parameters that were explored were: types of screen surface (polyurethane, woven wire etc), types of screen motion (linear, circular or elliptical), angle of motion ( 40,45,55,60 degrees etc), and throw (amplitude), speed and 'g' force.

Jun 1, 2010

By J D. Bryant

The Ernest Henry Copper-Gold mine, the third largest copper deposit in Australia, is located 35 km NE of Cloncurry in the Mt Isa-Cloncurry mineral district of NW Queensland. Ernest Henry Mining Pty Ltd (EHM), a wholly owned subsidiary of Xstrata Copper Australia, operates the mine. Approximately 10.2 Mt of ore grading 1.12 per cent Cu and 0.56 g/t Au were processed during the 2001 - 2002 financial year. The Ernest Henry plant produces copper-gold concentrate, which is trucked to Mt Isa for smelting. The Ernest Henry deposit is a member of the diverse Fe-oxide-(Cu-Au) class of deposits. The orebody is hosted within a sequence of moderately SSE-dipping, intensely altered Paleoproterozoic intermediate metavolcanic and metasedimentary rocks. Copper (chalcopyrite)-gold mineralisation occurs mainly within the magnetite-biotite-calcite ¦ pyrite matrix of a 250 m + 300 m pipe-like breccia body. The breccia pipe comprises two anastomosing lenses separated by a lower grade, clast-supported breccia zone. Several anastomosing brittle faults affect the macro-geometry of the orebody. Copper grade is proportional to the degree of matrix support in the breccia. The July 2002 Ore Reserve was 88.7 Mt @ 1.0 per cent Cu and 0.5 g/t Au. Resource estimation at Ernest Henry is based on a large database of predominantly diamond drill hole information. Drill spacing is typically 50 m + 50 m. Ordinary kriging is used to estimate Cu, Au, SG and IST (oxidation indicator) into model parent cells of dimension 20 m E + 20 m N + 16 m RL. The block model is comprised of five geological-geochemical domains represented by 3D wireframe surfaces. Zonal control, where samples and blocks are assigned the same domain number, is used to control grade estimation. The geometry of the domains defines hard grade boundaries across strike and soft boundaries along strike A Deep Drilling Project was initiated in August 2002 with the initial aim of testing the down-plunge extension of the orebody to a vertical depth of over 1 km. The encouraging intersections to date have resulted in a significant increase in the mineÆs open pit Mineral Resource together with the identification of an underground Mineral Resource. Added benefits of the project included an expanded and updated geological legend and an improved understanding of the host geological sequence.

Jan 1, 2003

By H Holmstr÷m, A Widerlund, M Lindvall

At the Kristineberg mine in northern Sweden sulfide-rich, poorly buffered tailings have been deposited in five impoundments located along a valley. The tailings area has been remediated by applying a combination of till cover and flooding. A new method that has been applied to parts of the tailings area is to raise the groundwater table to saturate the tailings. By increasing pH by liming, thereby reducing metal mobility, a water-covered downstream impoundment is functioning as a trap for metals released from the till-covered impoundments upstream. In this paper the efficiency of the system approach used at Kristineberg is evaluated. Progressive changes of water quality from groundwater in the upstream till-covered impoundments via surface streams within the pond system to the water in the flooded downstream pond and its outlet are described. The results show that the system approach used in the design of the remediation programme of the tailings works as planned. The sulfide oxidation rate has decreased in the till-covered impoundments, and, as predicted, there is an out-flush of old weathering products which will continue for at least five years before equilibrium is reached. The groundwater in the till-covered impoundments has high concentrations of Fe, S, Mg and Zn, but the concentrations of metals such as Cu, Cd and Pb are much lower than before the till cover was applied. The limed pond is an efficient metal trap, with concentrations as high as 2.76 per cent Zn and 0.28 per cent Cu in the calcite-gypsum sludge developed on the tailings. The outlet from the flooded pond, and thus from the whole mining area, releases small amounts of metals to the recipient in comparison to the amounts that are in movement within the mining area. During the period May to November, 13 kg dissolved Zn and 111 kg particulate Zn was released to the recipient, whereas a total of 27 000 kg was transported by surface water within the impoundment system during the same period. The results from Kristineberg show that when planning remediation of complex mining areas, it is useful to adopt a system approach in which different methods are used on different parts of the area along the flow path of the drainage water, whereas flooding of the downstream pond is the key to the performance of the entire system.

Jan 1, 2003

The purpose of the Lower Lea Valley Cable Tunnel project is to relocate the overhead power lines circuits, which currently cross the proposed site for the 2012 London Olympics in East London. This was the first contract to be awarded as an Olympic project and is on the critical path for the proposed Olympic Park as the construction of the Olympic village, stadium and other venues cannot begin until the tunnels are complete, the cables installed and the overhead power lines removed. The tunnelling works for the scheme include two parallel tunnels between Hackney and West Ham. Each tunnel is approximately 6 km in length. One tunnel is 4.15 m ID and connects the National Grid substations. The other is 2.82 m ID and connects the EDF Energy substations. The tunnels were constructed through mixed ground using four earth pressure balance tunnel boring machines. These were driven simultaneously from two drive shafts within a single site. The 12 km of main tunnels were constructed within a year from start to finish, with completion in June 2007. The shafts range between 6 m and 15 m ID. These were constructed using a combination of caisson sinking and underpinning techniques. Dewatering was adopted to suit the groundwater conditions.Other works include the design and construction of the head house buildings, cable and ventilation culverts, mechanical and electrical (M&E) installations and all associated works. In addition to the above, a further 1 km of tunnel and two shafts were added to the project scope connecting the EDF Energy tunnel to the substation at Bow. These additional works provided further challenges to the project to ensure that these works were constructed within the program constraints for the 2012 London Olympics. This involved refurbishing one of the tunnel boring machines from the main EDF Energy tunnel drives and relaunching the machine to construct the Bow tunnel. The Bow tunnel was constructed within two and a half months, with the tunnel boring machine breaking through in August, ahead of schedule. The main challenge presented by this project is the program constraints. This project outlines the requirement for team work between the client, stakeholders, contractor and designer in order to provide program certainty. A close working relationship between the contractor and the designer is required to provide value engineered, time-saving solutions to mitigate the risks associated with the design and construction program.

Jan 1, 2008

By M Thomas, M Caccetta, C Laukamp, A Hacket, M Jones, A Rodger, M Verrall, R Hewson

A mineral systems approach was used to interpret precompetitive airborne mineral mapping geoscience data for iron oxide copper gold (IOCG) exploration in the Starra area, Eastern Succession, Mount Isa Inlier. Selected minerals were chosen to map possible source rocks/fluids as well as intersecting structural/fluid pathways that could have transported mineralising fluids into domains of contrasting rocks/fluids where there was potential for physicochemical gradients to precipitate metals. Ferric and ferrous iron contents and white mica abundance were useful mineral criteria to identify theMount Dore Granite of theWilliams-Naraku Batholith as a potential source of æoxidisedÆ fluids rich in Fe, K and potentially Cu-Au. The Mount Dore Shear Zone (MDSZ) intersects the western margin of this granite with the highest contents and changes in composition of the white mica are peripheral to this contact within the granite. This together, with the fact that the entire N-S length of the MDSZ in the study area (~16 km) is abundant in white mica are evidence of K-rich fluids had preferentially moved along this pathway. To the south, the MDSZ intersects a domain comprising massive ironstone bodies as well as numerous graphitic horizons. This interpreted æreducedÆ domain is well mapped using the æopaqueÆ mineral products, as well as by white mica, which is pervasively developed and extends 2 km either side of the MDSZ fault into the meta-sedimentary sequences. The chemistry of this white mica also changes progressively away from the MDSZ, becoming more Si-rich (longer wavelength) towards the contact with massive ironstone bodies in the west and the graphitic units in the east, both of which represent sites of known Cu-Au mineralisation. Beyond these contact zones of interpreted æoxidised fluidsÆ with reduced rocks/fluids, there is either a rapid change to Si-poor white mica and/or no white mica developed, ie major æchemicalÆ gradient change. These mineral mapping results provide evidence for a direct link between possible source rocks and sites of IOCG metal deposition as well as extending the associated alteration zonation which had previously been mapped/published at the metre-scale to the kilometre-scale. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

The Ranger Project Area covers 78.6sq km and is approximately six km east-west by 14km north-south (Fig. 1). The area is known to con- tain two uranium orebodies, Ranger No. 1 and No. 3, two uranium occurrences, Anomalies 4 and 5 and three significant radon anomalies, Ranger 18, 19 and 48. The Ranger No. 1 and No. 3 Orebodies con- tain approximately 120 000 tonnes of U308 in highly chloritised metasediments of the Lower Proterozoic Cahill Formation. The orebodies occur as suboutcrop and exhibit significant radiometric anomalies. These occur within approximately 400m vertically of the projected unconformity with the sandstone of the Middle Proterozoic Kombolgie Formation. Oxidised and reduced uranium minerals occur in quartz-rich schists containing variable muscovite, chlorite and sericite and in the chloritic matrix of chert breccia. Secondary uranium minerals namely saleeite, metatorbernite and gummite associated with earthy iron oxides occur from the surface to 50m depth in No. 1 Orebody and up to 80m depth in No. 3 Orebody. Below the oxidised zone, uranium occurs as pitchblende finely disseminated throughout sequences of quartz muscovite chlorite schist up to 150m thick and as open space fillings in zones of structural deformation. The uranium-bearing schists directly overlie up to 300m of dolomite and magnesite containing minor interbedded schist units and are themselves overlain by approximately 2 000m of more micaceous schists of the upper part of the Cahill Formation. Regional metamorphism has occurred to at least amphibolite facies and has been followed by retrograde metamorphism to a greenschist facies equivalent. The metasediments are intruded by granitic pegmatites and dolerites. Uranium is associated strongly with chlorite of which there are at least five textural varieties. Not all of the various generations of chlorite have associated uranium. Graphitic schist horizons occur which are often less than one metre thick and discontinuous. These are best developed at the base of the quartz chlorite schist sequence where uranium grades up to 1 000ppm U may extend for several hundred metres beyond the main ore zone. Uran- ium is not common in the carbonate sequences and only occurs in chlorite segregations in disrupted zones. The unoxidised ore contains sulphides, mostly pyrite, which are low in abundance (

Jan 1, 1984

Dr Eric Bumstead is to be commended for his recent paper on gold analysis, published in the March 1984 Proceedings. It is not often that someone in industry, rather than academia, takes the time to collect and report on such a volume of data, data which is of interest to everyone involved in gold exploration and development.After reading the paper I felt, as a geochemist and as ayer, that there was another side to this whole question of analysis that few people are aware of, i.e. the problem facing a laboratory and how the laboratory can try to give the customer maximum value for money spent.Analyses for gold are carried out for different reasons, depending on the aims of the geologist or metallurgist who presents the samples. These can broadly be separated into three classes, to answer the following questions.1. "Is there any gold in this sample?"2. "Approximately how much gold is there in this sample?"3. "How much gold is there in this sample?"In every case there is a different balance between accuracy and precision, cost and avoiding chemical problems. By "chemical problems", I mean such possibilities as samples containing high levels of sulphides, gold present as tellurides, cyanide being present, contamination with mercury, and other mineralogical oddities, plus problems such as samples containing grease.There is no such thing as one assay to cover all possibilities.Samples in category I come mostly from early stages of exploration.There are often large numbers of samples, their mineralogy is not well known and hence chemical problems could exist, but the explorer wants assays at a minimum level of precision and expects minimum cost. These characteristics do not easily come together, for although the precision required is low, the accuracy required is high at low levels. A small positive result when the true answer is nil could lead to a fruitless search and a waste of money. Conversely, a nil result, when the true answer is a small but significant level of gold, could lead to the passing over of an area that may warrant further work.Because there are conflicting requirements for this type of assay, the methods chosen must be a compromise and different assayers will balance these requirements differently and come to different conclusions. The methods cover sample preparation, assay sample size and variations in assay techniques.

Jan 1, 1984

By J I Stewart

The Copper Canyon deposits, occur in proximity to the regionally distinctive formational boundary between the Staveley Formation and Marimo Shale. The mineralisation here is associated with breccias, veins, and alteration zones near the base of the Marimo Shale unit and in the underlying evaporitic dolomite-dololutite dominant Staveley Formation. The Marimo Shale unit, in its basal 60 metres, is highly carbonaceous and hosts ubiquitous but minor diagenetic (?) copper-pyrite, and on occasion, extensive albite-microcline alteration centres, pyritic (cobaltiferous)-quartz veins, and microcline-quartz_+plagioclase veins or veinlet arrays. The most significant mineralisation, such as at the Greenrnount prospect, consists of a shallowly dipping package of alteration zones overprinted by multiple generations of pink-orange microcline-quartz-chalcopyrite-pyrite-(arsenopyrite) and albite-calcite- phlogopite veins. Accessory mineralogies in most of these mineralisation styles consist of tourmaline, monazite, rutile, and apatite. Chalcopyrite (and secondary chalcocite) and gold are associated with each generation of alteration but are best developed in the later stages of veining. In the underlying Staveley Formation, which is a conformable transition between the Corella Formation limestones and the Marimo Shale, chalcopyrite (cobaltiferous)-pyrite mineralisation occurs as disseminations in pre- and syntectonic breccias, and with disaggregated silica pseudomorphs (after thinly bedded evaporitic sulphate beds) and associated dolomitised limestone-calcilutite. Although this mineralisation may be partly diagenetic in origin the 200 in thick evaporitic packages are also host to a locally widespread (2 to 4 km long and 200 to >500 metres wide) and pervasive 'redrock' styled microcline-dolomite¦hematite alteration. Within this gross alteration package there also seems to be a consistent association with narrow (10 to 100 metres wide), linear (stratabound) semi-massive magnetite-hematite-microcline and quartz-chalcedony replacement zones. Like much of the nearby Corella Formation the Staveley Formation, under the Marimo Shale, has undergone dissolution, paleo-solution karsting (breccias) and tectonic brecciation such that the precursor lithological details have been progressively obliterated. The post-diagenetic to post-tectonic fluid pathway development and metasomatic alteration history of this important lithostructural package of rocks has been traced from preliminary studies only. The ability to do so is largely due to the absence of significant regional and contact metamorphic overprinting, and the local preservation of precursor sediment profiles. It is proposed that both the base of the Marimo Shale and parts of the underlying evaporitic-limestone-dololutite have acted as conformable fluid pathways for hydrothermal and (perhaps) diagenetically derived, Cu-Au-(¦Co ¦As) K-Na-Ti-REE bearing, fluids and brines.

Jan 1, 1994

The West Fork project is located in Reynolds County, Missouri, in the mineralized zone referred to as the Viburnum Trend. The West Fork orebody has a calculated ore re- serve of 13 600 000 tonne (15 000 000 st) con- taining 5.5 per cent lead, 1.2 per cent zinc, and recoverable values of copper and silver. A total of 64 600 tonne (71 200 st) of lead concentrate and 11 300 tonne (12 500 st) of zinc concentrate will be produced annually. The mill was designed to operate at an average capacity of 3450 tonne/day (3800 st/day), based on a 95 per cent availability factor. The mill will operate 24 hours a day, 5 days a week, with maintenance performed, as needed, on weekends. The mine will operate on an identical schedule; but the underground, pri- mary crushing will operate on a six hour/shift, three shift/day schedule. The 1.07m x 1.22m (42in x 48in) jaw crusher will produce a minus 20cm (8 in) material at an average rate of 191 tonne/h (211 st/h). The jaw crusher has almost twice the throughput capacity required, but the decision to install that size of crusher was based on the need to handle over sized rock in the ore.The coarse crushed ore will discharge into a 180 tonne (200 st) skip pocket, which will allow up to a one hour surge capacity prior to hoisting. Hoisted ore will discharge into a 900 tonne (1000 st) storage bin located adjacent to the headframe. The skip pocket and coarse ore silo comprise the total ore storage capacity. The concept of having no intermediate fine ore storage between the secondary crushing and grinding sections was borrowed from the Brushy Creek Mill of St. Joe Minerals, which operates adjacent to the West Fork property. Integration of the secondary crushing and grinding circuits has worked ' successfully for years at the Brushy Creek Mill. The most obvious advantage to eliminating the intermediate fine ore storage is'capital expen- diture savings. The capital expenditure savings include the cost of silos, feeders, and the cost of additional conveyor length and eleva- tion. Savings in operating costs will also be gained, particularly in reduced maintenance costs. Other factors which influenced the decision to eliminate fine ore storage were the simplicity of the secondary crushing sec- tion and the limited area available for con struction of the facility

Jan 1, 1978