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| St Ives Gold MineTechnical Short Form Report St Ives Gold Mine represents a solid base for Gold Fields growth in Australia and is an important contributor to the Gold Fields’ vision, “To be the global leader in sustainable gold mining,” with a target contribution from the Australasia Region of ~1 Moz per annum. Reported Mineral Resources and Mineral Reserves at St Ives gold mine show a headline increase of 1,105 and 443 koz during F2009 respectively, inclusive of a depletion of 490 koz, indicating an underlying increase of 1,595 and 933 koz respectively. Changes from June 2008 were dominated by discoveries at Athena and Hamlet, and the impact of the higher declared gold price. The St Ives LoM has again been extended by a further 12 months following a year of continued exploration successes. The St Ives Gold Mining Company (Pty) Limited is wholly owned by Gold Fields Limited and is situated within the highly prospective Norseman-Wiluna Greenstone Belt in Western Australia. The St Ives operations are conducted within mining tenements comprised of 366 Mining Titles (69.919 ha), 9 Exploration Licences (15,530 ha), 47 Prospecting Licences (7,194 ha) and 19 Miscellaneous Licences (14,643 ha) for a total area of approximately 107,286 ha. This Technical Short Form Report reflects the latest Life of Mine plan, coupled with an updated Mineral Resource and Mineral Reserve statement as at 30 June 2009. All Mineral Resource and Mineral Reserve figures reported are managed unless otherwise stated and Mineral Resources are inclusive of Mineral Reserves. Salient Features
Key Features
Operating Statistics
Rounding off of figures presented in this report may result in minor computational discrepancies, where this occurs it is not deemed significant. Geological Setting and Mineralisation St Ives is situated in the Norseman-Wiluna Greenstone Belt, which is part of the Yilgarn Craton, a 2.6 Ga granite-greenstone terrane in Western Australia. In comparison to other greenstone belts in the Yilgarn Craton, the Norseman-Wiluna Belt is highly mineralised, particularly in gold and nickel. The rock-types in the belt comprise abundant tholeiitic and komatiitic volcanic rocks, chert, sulphidic and albitic sedimentary rocks, and a chain of discrete felsic volcanic centres. The gross structure is markedly linear with north-northwest trending strike-slip faults and other tectonic lineaments traceable for hundreds of kilometres, which disrupt the greenstone into fault-bounded domains. The generalised stratigraphic sequence comprises three mafic-ultramafic units, two felsic volcanic units, and an uppermost epiclastic sequence. There has been a complex and long-lasting history of structural deformation incorporating up to 7 significant stages (D0-D7) during and after regional metamorphism. The gold mineralising episodes are interpreted to have occurred during thrusting and faulting associated with the D2-D3 structural events. Metamorphism has affected all rock-types and ranges from low temperature prehnitepumpellyite facies to high temperature-pressure amphibolite and granulite facies. Flexures and irregularities in many local and regional shear zones are interpreted to be the major control on location of the majority of economic gold deposits in the belt. Much of the Yilgarn Craton is deeply weathered and partially covered by Tertiary and Quaternary regolith. Pre-Tertiary lateritic horizons are variably exposed, eroded or buried by later deposits that have in turn been lateritised. Local geology St Ives lies within the Kambalda Domain, a subset of the Norseman-Wiluna Belt. The Kambalda Domain is bound by the northnorthwest trending Boulder-Lefroy Fault (BLF) and Zuleika Shear. The region has undergone four compressional events pre-dated by early extension and has been metamorphosed to upper greenschist or lower amphibolite facies. The main structural feature of the St Ives area is the gently south plunging Kambalda Anticline, which extends 35 km from the south end of the Kambalda Dome to the Junction Mine. The majority of known gold deposits are proximal to the trace of the anticlinal axis. A major second order structure known as the Playa Shear splays off the BLF Shear Zone and can be traced through the St Ives field for a distance in excess of 10 km. Most of the St Ives orebodies mined to date are associated with third order splays off the Playa Shear – notable exceptions being Argo and Santa Ana which are situated on the western limb of the anticline. Mineralisation typically occurs where these structures intersect favourable rock units, with chemical or rheological contrasts combining with structural flexures to form the most important local controls to mineralisation. The interaction between structures and rock-types has produced a large number of individual deposits with at least 80 having been mined in the St Ives area. The stratigraphic succession in the Kambalda Domain comprises Kalgoorlie Group volcanic rocks and the Black Flag Group felsic volcanic and sedimentary rocks overlain by the posttectonic Merougil Beds unit. The most common host rocks of gold mineralisation are dolerites such as the Defiance, Condenser and Junction Dolerites. Granophyric dolerite and Kapai Slate tend to host the highest grade mineralisation. The Paringa Basalt and Kambalda Komatiite host deposits in discrete shear structures that are moderate in both tonnage and grade. Low to moderate grade, high tonnage mineralisation is commonly developed in porphyries, which are found in almost all deposits. The Kambalda Domain to the north is structurally complex. Multiple phases of deformation occurred during and after regional metamorphism. The domain is crossed by a network of variably striking and dipping first, second, third and fourth-order shears, faults and thrusts that control the location of the gold mineralisation. Hydrothermal alteration and associated gold mineralisation was synchronous with deformation on a network of shear zones. Alteration is concentrated in 10 cm to 300 m wide halos around shear zones. Gold is commonly associated with pyrite or granular pyrrhotite.
There are several styles of gold mineralisation at St Ives. The individual deposits may contain more than one of these styles:
Exploration and drilling The St Ives exploration strategy incorporates the integration of geological information and knowledge of ore forming systems to identify targets with the greatest potential for conversion from endowment, thus maintaining a high value project pipeline. This strategy includes:
Mining Gold mineralisation at St Ives is mined via both open pit and underground methods to depths generally not exceeding 500m below surface. As many of the operations involve mining deposits on or under Lake Lefroy (a shallow salt lake), extraction requires construction of berms and other earthworks to provide access, short-term stockpile areas and to prevent water intrusion. Mining methods Open pit mining by conventional drill and blast/truck and shovel is employed at all open pits. Grade control is generally by inclined RC drilling. Open pit projects may include 10 – 40 m of unconsolidated sedimentary overburden which does not require drill and blast, but requires hard rock to be imported for sheeting to provide equipment access during mining, and/or dewatering of the sedimentary overburden prior to mining. Load-and-haul is by 140t dump trucks and 150 – 250t excavators in backhoe and/or face shovel configuration. Mining benches vary from 5 – 10m which are excavated in 5 passes (flitches) of about 2.5m. Gold mineralisation is mined selectively to cut-offs and segregated into grade ranges as required to balance the ore production and processing capacities on site and maximise cash flow from operations. Underground mines at St Ives are commonly extensions of open pit mines. Underground operations are characterised by common features which allow a high level of standardisation in operating strategy, mine design, stoping methods, mining equipment and utilisation. Mines are accessed via declines, with additional development of raises for return airways and ladder-ways as second means of egress. Ore drives are developed to access the ore and future stoping production areas. Underground mining at St Ives is predominantly mechanised and is conducted by long hole open stoping (LHOS), with subordinate cut-and-fill and room-and-pillar for the shallower dipping orebodies. The use of paste fill in conjunction with LHOS is applied where mandated by geotechnical factors. Development and stoping utilises electric-hydraulic drilling jumbos and rubber-tyred diesel-powered LHDs and trucks are used for load and haul operations. Ore from both open pit and underground operations is transported with road trains from individual mining operations to the St Ives’ processing facilities.
Mine planning and scheduling Mineral Reserve definition processes for open pit and underground operations are essentially similar. Cut-off grades are applied to define potentially economic mining panels based on direct mining and/or processing costs, commodity prices and other parameters. The economic viability of future mining panels is then tested by determining whether the margin above cut-off is sufficient to cover the required capital development costs and provide a return on investment. Open pit planning entails the input of economic parameters and physical constraints into optimisation software to generate a series of nested pits, from which an optimal shell is selected. Detailed design is then undertaken to confirm the mineability of the optimised shell. The process is iterated until an acceptable level of correlation is achieved between the optimised shell and detailed design. Underground mining methods are largely determined by the geometry of the mineralised zones and the evaluation may involve review of more than one method. Mine design and scheduling is done utilising sophisticated software. Mine planning is based on three-dimensional block models of in-situ mineralisation, with allowances made for minimum mining widths, dilution and ore loss appropriate to the mining method being considered. Infrastructure, waste disposal and ore stockpile management requirements are incorporated into the planning process. Ore stockpile management at St Ives strives to optimise the metallurgical blend requirements to the Lefroy Mill and the Heap Leach, with regard to material types and grade management, to maximise cash flow from operations.
Projects The major mine expansion project at St Ives is the initiation of underground mining at the new Athena deposit. Portal and access development has commenced to provide exploration platforms and detailed mine design coupled with full feasibility studies are in progress. Ongoing infrastructure development to meet current and future mine extensions together with extending the individual mines through focused extensional exploration and development continue. Other future projects are: Heap Leach Expansion The remaining pad capacity of the Heap Leach is 0.4 million tons, or 2 months production at the current throughput rate. Consideration has been given to either the construction of a new pad or the removal of spent (leached) ore from the existing pads. Preliminary site trials indicated that removal of the current spent material and re-usage of the pads will be environmentally sound and economically viable. A strategy of flushing, removing, restacking and leaching will be employed to treat the remainder of the Heap Leach ore supply. Tailings Storage Facility A fourth tailings storage facility (TSF 4) may be constructed and commissioned by January 2013 to allow tailings deposition from the Lefroy Mill. TSF 2 has reached its renovation limit and is expected to reach deposition capacity by the end of 2009. It will be replaced as an alternate deposition to TSF 3 with North Orchin pit. Construction of TSF 4 will permit the continual implementation of this strategy beyond the current LoM. LoM Tailings Deposition
* Budget estimates including tailings lifts, TSF4 and North Orchin Construction
Mineral Processing St Ives employs two separate beneficiation processes, CIP plant and Heap Leach facility, for the treatment of mined ore and existing stockpiles. The Lefroy Mill was commissioned in December 2004 and achieved design capacity within seven months. It treats medium to high grade ore through a 4.8 Mtpa variable speed dual direction 13.5 MW SAG mill with wrap around motor. Oversize from the mill (scats) is in closed circuit with a 140 tphr pebble crusher. A gravity circuit recovers the gravity recoverable gold from the milling circuit and the concentrates are treated separately through to bullion form. The mill cyclone overflow product reports to a 5 stage leach circuit consisting of mechanical agitators, reagent addition and oxygen sparging. Leached slurry passes through the 6 stage carousel pump cell adsorption plant and subsequent 5 ton capacity acid wash, elution and electrowinning circuits which produce calcine ready for smelting. Bullion is shipped to the refinery. Tailings are alternately deposited on two tailings facilities which are constructed upstream and are of paddock type. The Heap Leach process was commissioned during 2000 and is used to at treat lower grade ore at a rate of 2.3 Mtpa. A three stage crushing circuit, of 900 kW installed comminution power, is currently used in a 24 hour operation to prepare -15 mm ores for agglomeration, stacking and leaching. A mobile oxide screen was recently introduced to the circuit to screen off oxides at 35 mm for direct feed into the agglomeration circuit thereby bypassing the comminution phase. The leach pads have been expanded in three stages of 5.5 Mt each with the third stage nearing full capacity. Alternate rehandling methods are currently under review for sustainable operation. Leaching on the heap is performed in 2 stages with typical solution application of 8-10 litres per m2 per hour. The second stage pregnant leach solution passes through a 6 stage carbon circuit for gold adsorption. Gold is stripped off the carbon, electro won and calcined at the Heap Leach wet plant prior to shipment to the Lefroy Gold room for smelting.
Sustainable Development St Ives strives to achieve and maintain outstanding health and safety performance through the participation of all employees and the application of safe, innovative processes and technologies, within a framework of OHSAS 18001, which is an international occupational health and safety management system standard against which our management systems are assessed and certified. At St Ives we strive to create a workplace culture of “zero harm” and to assist us in this pursuit for our people, we’ve embarked on a programme of ZIP (Zero Incident Process). ZIP is a process that gives the workplace the genuine opportunity to reach the goal of zero incidents. It is a process that empowers people to be able to take control of their personal safety. ZIP does this by giving them an insight into the way their brain works and how they can use it more effectively to keep themselves safe. At St Ives the consideration of our activities in a manner which minimises our environmental and stakeholder impacts is fundamental to our operations and the way we do business. The operation is committed to responsible stewardship of natural resources, proactive engagement with all stakeholders and behaving in an environmentally responsible manner. This is demonstrated through our commitment to continuous improvement of the site management systems and operational performance. This is evident through our ISO 14001:2004 certification and compliance with our licence to operate.
Mineral Resources and Mineral Reserves Mineral Resources The Mineral Resource statement for St Ives is summarised in the tables below. The following points apply to Mineral Resources presented in this report:
Modifying factors
Grade tonnage curves Underground
Open pits
Mineral Reserves The Mineral Reserve statement for St Ives is summarised in the tables below and these following points apply:
Surface sources are comprised of stockpiles. St Ives assumes that stockpiles are managed and monitored when mining occurs and are supported by adequate sampling, and are thus classified as Proved Mineral Reserves.
Mineral Reserve split by source between CIP Plant and Heap Leach facility
Mineral Resources and Mineral Reserves Reconciliation year-on-year Mineral Resource Factors that affected Mineral Resource reconciliation:
Change in Mineral Resource F2009 to F2010
Mineral Reserve Factors that affected Mineral Reserve reconciliation:
Change in Mineral Reserve F2009 to F2010
Mineral Reserve sensitivity Mineral Reserves are presented on a RoM basis delivered to the metallurgical processing facilities. To illustrate the impact of fluctuations in gold price and exchange rates on the current declaration, St Ives has generated sensitivities with respect to Mineral Reserves. These sensitivities (other than for the base case) are not supported by detailed plans and should only be considered on an indicative basis, specifically as such sensitivities assume 100% selectivity, without any operating cost increases. Managed Mineral Reserve Sensitivity
Regulatory Codes SAMREC JSE Sarbanes-Oxley Act Environmental
Competent Persons M Jolly: Manager: Mineral Resources M Briggs: Exploration Manager J. Donaldson, Principal Resource Geologist C Ferguson: Mine Geology Manager S Ellery: Resource Evaluation Supt
Key Technical Staff
St Ives History at a Glance
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