The Cerro Corona mine is located in northern Peru on the eastern slope of the western mountain range of the Andes.
- Solid platform for growth within the region
- Plant productivity increased to 832tph
- Important cost saving and productivity initiatives were implemented in key operating areas
- Total AIC/oz amounted to US$499/oz in 2016
- LoM extends to 2023 (seven years)
- 99.53% attributable to Gold Fields
Operational profile (Cerro Corona)
- Mineralisation hosted by a sub-vertical cylindrical shaped diorite porphyry
- Confined to well-defined intrusive body
- Mineralisation zones discontinuous with mid-range predictability
|General location||The Cerro Corona deposit, centred at longitude 78° 37’ W and latitude 6° 45’ S, is at elevations ranging from approximately 3,600m to 4,000m above mean sea level (amsl). It is located 1.5km west north-west of the village of Hualgayoc, some 80km by road north of the departmental capital of Cajamarca, and approximately 600km north north-west of the capital city of Lima.|
|Licence status and holdings||The mining concessions owned by Cerro Corona cover an area of 4,365ha while the surface rights cover 1,291ha. Cerro Corona is owned by GFLC, which holds 99.53% of the economic interest.|
|Operational infrastructure and mineral processing||Cerro Corona Mine operates one open pit and one copper-gold plant.
The processing plant at Cerro Corona includes the typical equipment for a copper flotation plant, with a design capacity of 6.7Mtpa. The crushing plant comprises two jaw crushers in parallel and two Avon Sizer in each line. Crushed product is conveyed to a two-stage grinding circuit consisting of a SAG mill and a ball mill, in closed circuit with cyclone cluster for classification. Cyclone overflow represents the final milled product and feeds the flotation plant. The rougher flotation produces a bulk concentrate, which is then reground and sent to cleaner flotation. The tails go to scavenger flotation, while the concentrate, with a grade of over 20% copper, goes to the next process.
The final concentrate is thickened and filtered before being stockpiled for road transport (380km) to the Salaverry port, for shipment to copper smelters in Japan, Germany and Bulgaria. The thickened rougher flotation tails and the tails from the cleaner-scavenger flotation are sent by gravity to the tailings storage facility.
|Climate||There are no extreme climate conditions that may affect mining operations.|
|Deposit type||The Cerro Corona copper-gold deposit is typical of porphyry-style mineralisation comprising stock work quartz-pyrite-marcasite-chalcopyrite ± bornite ± hematite ± magnetite veining, hosted by intensely altered intrusive lithologies of diorite to dacitic composition.|
|LoM||It is estimated that the current Mineral Reserve will be depleted in 2023 (seven years). Options for Mineral Reserve conversion to increase the LoM are under review.|
|Environmental, health and safety||No fatalities were recorded during 2016.
Cerro Corona maintained its ISO14001:2004 and OHSAS 18001:2007 certifications. In 2016, GFLC maintained its registration in the Official Register of Good Environmental Practices managed by the environmental regulator (Agency for Environmental Assessment and Enforcement – OEFA). GFLC did not have any findings in the audits done by the regulator in the last three years.
Brief history of Cerro Corona
In 1979, exploration identified porphyry-style mineralisation in the Cerro Corona area. During the period from 1992 to 1993, sampling by the Gubbins Group identified gold mineralisation in the leached cap of the Cerro Corona deposit. Copper-gold porphyry mineralisation was discovered through the drilling of nine diamond core holes and completion of an exploration audit into the mineralised zone.
From 1994 to 1996, Cerro Corona then held by Barrick, drilled 140 reverse circulation drill holes totalling 9,476m and 118 diamond core holes totalling 35,254m. A draft feasibility study was completed by Kilborn. From 1997 to 1998, RGC Limited drilled six diamond core holes totalling 2,760m and a preliminary feasibility study was completed by Fluor.
In 2001, Minproc completed a number of feasibility studies, which ultimately indicated a Mineral Reserve of ~95Mt. In 2003, Gold Fields, through a subsidiary, signed a definitive agreement with Sociedad Minera Corona S.A. for the purchase of the Cerro Corona deposit and adjoining mining concessions.
The environmental impact assessment was approved on 2 December 2005 and the purchase transaction for the Cerro Corona Project was completed in January 2006. Mine construction commenced in May 2006. Building of the Las Gordas tailings dam and quarrying for the relevant construction material commenced in 2007. The mine started production in September 2008, when the process plant started to operate.
Gold Fields Corona (BVI) Limited, awholly owned subsidiary of GFL, increased its economic interest in Gold Fields La Cima S.A. from the original 80% to 98.6% in 2012 and in 2013 to 99.53%.
Key developments and material issues
- Cerro Corona remained the lowest cost producer in Gold Fields (AIC at US$499/oz in 2016), producing high-margin gold and copper
- Additional work on assessing the potential to expand the LoM tonnage profile by configuring solutions to the current WSF and TSF constraints undertaken in 2016 will continue in 2017 to ensure the best possible long-term option is selected
- During 2015 and 2016, a number of projects that focused on enhancing the plant throughput, were implemented. As a result throughput averaged 832tph in 2016 versus 825tph in the plan
- An extensive geotechnical and geometallurgical relogging project was completed on 33km of core and a new geotechnical model is under construction encompassing the latest alteration model. This information will inform key pit design criteria as the pit develops deeper into the ore body
- An investigation into the viability of utilising gravity as a treatment option for the stockpiled oxide ore was conducted during 2016. The oxide ore has been stored in two stockpiles since 2008 pending identification of an optimal treatment process for the site. However, the results of the exercise did not meet expectations and this option was abandoned
- In parallel, a desktop study was completed, which showed that treating the oxides via a leach plant has a strong possibility of being economically viable. Consequently, a PFS will be completed in the first half of 2017. The oxide ore is estimated to contain approximately 300,000oz of gold that may be processed within five years and in parallel (partially or entirely) with the current flotation operation
- A PFS to include a gravity circuit and treat sulphide ore was completed in 2016 with positive results. Options are to separately filter and ship as high grade concentrate, or combine with current flotation concentrate. Implementation of this project will be confirmed during 2017
Plan of the Cerro Corona mining area