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| Cerro Corona MineTechnical Short Form Report The Cerro Corona Mine in the Gold Fields Limited South America Region, is located 40 km north of the Yanacocha mine, and 80 km by road north of the departmental capital of Cajamarca in northern Peru. The deposit is hosted by a sub-vertical, cylindrical shaped diorite porphyry (600 – 700 m in diameter), emplaced in mid-Cretaceous limestone, marls and siliclastic rocks. This Technical Short Form Report provides brief information on the mining and operational performance achieved during the first 10 months of operations and also presents an updated Mineral Resource and Mineral Reserve statement, as at 30 June 2009. Cerro Corona produces gold and copper by conventional open pit mining methods and beneficiation of sulphide ores by the extraction of a copper-gold flotation concentrate, which is trucked approximately 380 km to the Peruvian Port of Salaverry for shipment to smelters in Asia and Europe The Mine is expected to produce approximately 2.1 Moz of gold and 407 kt of copper in concentrate over a 15 year Life of Mine. At the declared commodity prices, the estimated copper and gold production is equal to a total of 4.5 million ounces gold equivalents (Moz Au Eq). The Metallurgical Process Plant has a treatment capacity of 18,000 tons of ore per day, or approximately 6.2 million tons of ore per year. LoM average total cash cost (exclusive of capital costs and taxes) is projected at US$358/oz AuEq. 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 The Cerro Corona Project is located in northern Peru on the eastern slope of the western mountain range of the Andes. The copper-gold deposit is a typical porphyrystyle of mineralisation situated within the Hualgayoc Mining District in the northern part of the Cajamarca Province, a metallogenic province hosting prolific epithermal, porphyry and polymetallic style mineralisation. The mining area is characterised by moderate to moderately steep mountainous terrain with elevations ranging from approximately 3,600 to 4,000 m above mean sea level. The Cerro Corona copper-gold porphyry is one of fourteen known Tertiary-aged porphyry Cu- Au-Mo deposits and nineteen epithermal Au-Ag deposits located in the Cajamarca Metallogenic Province (CMP) of northern Peru. There are two well mineralised districts within the CMP. These are the Yanacocha district in the south of the province, which is host to the largest producing gold mine in South America, and the Hualgayoc Mining District in the north which is one of the oldest mining districts in Peru, best known for its past silver production and more recent base metal production. This well known district has been an important silver producing area since Inca times, with more than 50 million ounces of silver and significant amounts of lead, zinc and copper produced from vein and manto-type deposits since the Spanish Conquest in the 16th Century. The Hualgayoc mining town was established in 1771. The regional structure is characterised by large open folds of Cretaceous-aged sedimentary units, predominately limestones, with axial planes striking approximately 315° and steep southwest dips. Faulting is generally restricted to normal and oblique slip faults with offsets of a few metres to a few tens of metres. Local geology The Cerro Corona copper-gold deposit is hosted by a 600 to 700 m diameter subvertical cylindrical-shaped diorite porphyry emplaced in mid-Cretaceous limestone, marls and siliclastic rocks. Within the porphyry, the copper-gold mineralisation is primarily associated with zones of stockwork quartz veining conforming to classic porphyry-type vein definition. The Cerro Corona porphyry is unusual in that it carries a very high gold content in comparison to other copper-gold deposits. There are at least two phases of diorite placement, only one of which is mineralised. The non-mineralised diorite is generally regarded as the last event, and is referred to as ‘barren core’. Most recent geological modelling strongly suggests that the Cerro Corona porphyry is probably comprised of four or five satellite stocks with the last two being barren. Early mineralisation was accompanied by moderate to strong potassic alteration which has been commonly overprinted by late, semi-pervasive argillic alteration and locally, by structurally controlled phyllic alteration assemblages (quartz-sericite-pyrite).
The intrusive has been emplaced at the intersection of Andean-parallel and Andeannormal (transandean) structures, which is a typical feature of the Cajamarca Metallogenic Province. A dominant northeast-southwest trending fault system running through the intrusive is referred to as the Mariela Fault trend and has an important relationship with the distribution of mineralisation. There are three distinct mineralised zones within the deposit. These are identified as the Annulus Zone, the Northern Zone and the Southern Zone. Each of these is treated separately in geological and resource modelling. In addition to the mineralised zones, the deposit is characterised by several domains conforming to the degree of oxidation and weathering. Supergene oxidation and leaching processes at Cerro Corona have led to the development of a weak to moderate copper enrichment blanket, allowing for the subdivision of the deposit, from the surface downward, into an oxide zone, a mixed oxide-sulphide zone, a secondary enriched (supergene) sulphide zone and a primary (hypogene) sulphide zone.
Geological domains Oxidation,weathering,leaching and subsequent secondary enrichment has led to the formation of four mineral domains with distinctly different metallurgical behaviour. The top-most domain, the Oxide Domain, is characterised by the complete removal of copper mineralisation through the action of oxidation and leaching. Gold mineralisation within the Oxide Domain is characterised by some improvement in grade and is free milling due to the complete breakdown of primary sulphide minerals. All of the ore beneath the Oxide Domain comprises parts of the sulphide zone, which is separated into three domains on the basis of degree of oxidation and consequent change in sulphide mineralogical composition. The sulphide zone has three main domains, which from top to bottom are the Mixed Domain, the Supergene Domain and the Hypogene Domain. The Hypogene Domain is the primary sulphide zone. The Supergene Domain is an enriched copper blanket comprising chalcocitecovellite- chalcopyrite with grades in the range of 1% Cu. Exploration and drilling Exploration in the district continues on the 50:50 joint venture project with Compania de Minas Buenaventura S.A.A.
Mining The Cerro Corona deposit is mined by conventional surface mining methods. The final surface mine area is expected to cover some 900 x 500 m. The mining operation is extending from the crest of the original Cerro Corona hill, which peaked at 3,964 mRL, to a final depth at around 3,660 mRL. Bulk mining will utilise 10 m benches with loading planned by a combination of a diesel hydraulic face shovel (230 t) and a rubber tired front end loader (190 t) loading and six (150 t) dump trucks. At this stage it is assumed that all of the material requires drilling and blasting (with varying powder factors) utilising 200 mm holes for 10 m benches. Mine planning and scheduling Cerro Corona’s LoM plan is based on detailed Geological and Mineral Resource models. The LoM plan is established from detailed short term and long term mining design and schedules using specialised Xpac© software and a resource estimation model termed the Bivariate Local Uniform Conditioning model (BLUC) that has been developed by internal Gold Fields Limited geostatistical consultants. Geotechnical and geochemical models for waste materials have also been developed and are used in the LoM as an effective Acid Rock Drainage (ARD) management strategy. The planning cycle commences with the ratification of key input parameters prior to producing a compliant Mineral Resource statement. The planning process starts after the construction of the resource model and incorporates the following considerations:
Open pit optimisations are built using Whittle 4X© – (Multi-element standard mine design software) on the BLUC resource model. Multiple case scenarios are run using varying gold and copper prices, processing costs, mill recovery values, and inclusion/exclusion of inferred material to ensure that the optimal pit is selected. The work undertaken includes:
Projects The Cerro Corona Pit is considered to be the LoM project. The upside potential is controlled by the availability to place and store tailings. Efforts to find additional storage capacity are ongoing. Mineral Processing Commissioning and ramp-up of the processing plant was performed in parallel, to optimise the operational timing between these two activities. The ramp-up to full monthly production levels was achieved by December 2008. From January 2009, the plant has been operating at near stable conditions with the only influence on the optimal performance resulting from the high variability of the ore feed. This variability is attributed to the complexities arising from the varying degree of sulphide oxidation in the different mineral domains such as the Mixed Ore and the Supergene Ore. The various ore types from the mine are stockpiled on the Run of Mine pad. They are fed in appropriate blends by front end loader to the crushing plant. This comprises two mineral sizers in parallel, one of which is a standby unit. Mineral sizers facilitate crushing of soft, wet ore with clay components. The crusher feed design also makes provision for direct tipping of ore from the mine if necessary. Crushed product is conveyed to a two-stage grinding circuit consisting of a SAG mill and a ball mill in closed circuit with cyclones for classification. Cyclone overflow represents the final milled product which feeds the flotation plant consisting of two sections. The rougher-scavenger flotation produces a bulk concentrate, which is then reground and upgraded to smelter copper grade in the four-stage cleaner flotation section. The final concentrate is thickened and filtered before being stockpiled for final shipment to the smelters. The thickened rougher-scavenger flotation tails and the tails from the cleaner flotation are pumped to the tailings storage facility. Training of qualified plant operators has been successfully achieved at Cerro Corona. Sixty people from the DIA (Direct Influence Area) were selected for a comprehensive seven-month training program comprising theory/ practical training, and exposure to existing Peruvian copper operations. Sustainable Development Cerro Corona commenced implementing it’s Health and Safety Management System in July 2008 in accordance with OHSAS 18001 and Corporate requirements. The objective of the Health and Safety Management System is to prevent injuries, occupational illness, and property damage and process loss.
No fatalities were recorded in F2009. Only two Lost Time Injuries (LTI) were recorded during the year and 2.3 million Man Work Hours without any LTI’s were accumulated. The Lost Day Injury Frequency Rate (LDIFR) improved from 0.96 in F2008 to 0.25. Cerro Corona was awarded the Safety Mining Award (second place) for Peru, a competition that is organized by the Safety Mining Institute of Peru. Cerro Corona’s environmental objective is to achieve the ISO 14001 certification during this calendar year. The final certification audit is planned for October 2009. Mineral Resources and Mineral Reserves Mineral Resources are reported as in-situ and are inclusive of those Mineral Resources which have been modified to produce Mineral Reserves. The Measured, Indicated and Inferred Oxide and Sulphide Mineral Resource estimate has been calculated within the diorite intrusion above 3,300 mRL. Mineral Resource statements include Measured, Indicated and Inferred Mineral Resources. The Mineral Resources are reported from the Bivariate Localised Uniform Conditioned model at a Net Smelter Return (NSR) cut-off of US$10.92/t and constrained within an optimised Whittle Pit Shell, based on the same economic parameters as the NSR calculation. (For comparative purposes, the NSR cut-off applied to the current Mineral Resources is 30% higher than was declared in the June 2008 CPR at US$8.40/t). Gold equivalent ounces are defined as a quantity of metal (such as copper) converted to an amount of gold in ounces, based on accepted gold and other metal prices i.e. The accepted total value of the metal based on its weight and value thereof divided by the accepted value of one troy ounce of gold. Mineral Resources
* Oxide Mineral Resource contains gold only resulting in the difference in tonnage Modifying factors
* Whittle shells run at US$2.20/lb for Mineral Resources and US$1.75/lb for Mineral Reserves. However US$2.75/lb and US$2.2/lb were used to calculate equivalent gold ounces for Mineral Resources and Mineral Reserves and to compare cash flows. Grade tonnage curves Sulphide Mineral Resource
Oxide Mineral Resource
Mineral Reserves
Mineral Resources and Mineral Reserves Reconciliation year-on-year Mineral Resource Factors that affected Mineral Resource reconciliation:
Change in Gold Mineral Resource F2009 to F2010
Change in Copper Mineral Resource F2009 to F2010
Mineral Reserve Factors that affected Mineral Reserve reconciliation:
Change in Gold Mineral Reserve F2009 to F2010
Change in Copper Mineral Reserve F2009 to F2010
Mineral Reserve sensitivity Improved Mineral Resources and Mineral Reserves potential are influenced by increased commodity prices, but is limited by the size of the Tailings Storage Facility (94.1 Mt). The sensitivities are not based on detailed depletion schedules and should be considered on a relative and indicative basis only. Managed Mineral Reserve Sensitivity
Regulatory Codes SAMREC JSE Sarbanes-Oxley Act Environmental Competent Persons Julian Misiewicz: Consulting Geologist Alberto Cardenas: Mining Operations Manager Eddie Garcia: Chief Mining Engineer Hugo Solis: Long Term Engineer Oscar Retto Key Technical Staff
Cerro Corona History at a Glance
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