Americas region - Regional overview

Operational profile (Cerro Corona)

Mining method   Open pit
Infrastructure   One open pit. One standard sulphide flotation plant with a capacity of 6.9Mtpa
Mineralisation style   Porphyry (Cu-Au)
Mineralisation characteristics  
  1. Mineralisation hosted by a sub-vertical cylindrical shaped diorite porphyry
  2. Copper-gold mineralisation conforms to classic porphyry vein definition
  3. Mineralisation zones discontinuous with mid-range predictability

Regional overview

The Cerro Corona mine is located in northern Peru on the eastern slope of the western mountain range of the Andes. The copper-gold deposit exhibits a typical porphyry style of mineralisation and is situated within the Hualgayoc mining district in the northern part of the Cajamarca province. This metallogenic province hosts prolific epithermal-, porphyry- and polymetallic-style mineralisation. The mining area is characterised by moderate to reasonably steep mountainous terrain with elevations ranging from approximately 3,600m to 4,000m above mean sea level (amsl).

Regional geology

The Cerro Corona copper-gold porphyry is one of 14 known tertiary aged porphyry Cu-Au-Mo deposits and 19 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 what once was the largest producing gold mine in South America. The other is the Hualgayoc mining district in the north, which is one of the oldest mining districts in Peru and is best known for its historic 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 50Moz 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 315º and steep south-west dips. Faulting is generally restricted to normal and oblique slip faults with offsets of a few metres to tens of metres.

Exploration drilling and expenditure

The Cerro Corona Mineral Resource is defined by approximately 97,000m of exploration drilling. Towards the end of 2014, Gold Fields La Cima (GFLC) had drilled an additional 1,311m of diamond drill core in order to increase the confidence in the definition of the lithological contacts and reduce local variability related to grade distribution within the five-year mine plan.

In 2017 an additional 3,590m of infill diamond holes were drilled to improve the grade estimation accuracy and to better define the geometallurgical features, for the longer term. Other factors like ore hardness, processing throughput and mineralogical characteristics are being taken into account to optimise the mine plan.

The Americas region maintains rigorous QA/QC protocols on all its resource definition and exploration programmes. It draws on industry leading practice for data acquisition and utilises accredited laboratories, which are regularly reviewed both internally and externally. Analytical sampling QA/QC is maintained and monitored through the submission of blanks, certified reference material and duplicates, plus umpire laboratory checks.

Off lease exploration targets have been generated in proximity to the Cerro Corona mine with the objective of discovering additional high-quality porphyry style ore sources. Licensing, permitting, community engagement, geological mapping and geochemical sampling are scheduled prior to any initial drill testing taking place.

Americas region summary of the Mineral Resource and Mineral Reserve estimate1
Mineral Resources Mineral Reserves
  December 2017 Dec
2016
  Proved and Probable December 2017 Dec
2016
 
Measured, Indicated and Inferred Tonnes
(Mt)
Grade
(g/t)
(Moz) (Moz)     Tonnes
(Mt)
Grade
(g/t)
(Moz) (Moz)  
Cerro Corona 115.0 0.69 2.5 2.5 Cerro Corona 86.2 0.70 1.9 1.3  
Salares Norte 23.3 4.89 3.7 3.8 Salares Norte
Total gold 138.3 1.40 6.2 6.3 Total gold 86.2 0.70 1.9 1.3  
Salares Norte silver 23.3 66.03 49.5 43.8 Salares Norte silver
           
Tonnes
(Mt)
Grade
(%)
Copper (Mlb) Copper
(Mlb)
Tonnes
(Mt)
Grade
(%)
Copper
(Mlb)
Copper
(Mlb)
 
Cerro Corona copper 107.9 0.39 917 815 Cerro Corona copper 86.2 0.40 767 456  

Mineral Resources are inclusive of Mineral Reserves. All tonnes (t) relate to metric units. Rounding-off of figures may result in minor computational discrepancies, where this happens it is not deemed significant. The Mineral Resources and Mineral Reserves were determined using the Group approved metal prices as stated in the 'Assessment and Reporting Criteria' 1Managed, unless otherwise stated

1 Managed, unless otherwise stated

Regional geology and metallogeny of the Cajamarca Metallogenic Province