Cerro Corona

Overview

The Cerro Corona Mine is located within a copper mining district in the Hualgayoc of northern Peru. It is 40 km north of the Yanacocha Mine, and 80km by road north fo the departmental capital of Cajamarca.

It is a porphyry copper-gold deposit hosted by a subvertical, cylindrical-shaped diorite porphyry (600-700m in diameter), emplaced in mid Cretacesous limestone, marls and siliciclastic rocks.

Cerro Corona mine became operational in 2009. It produces gold and copper by conventional open pit mining methods and beneficiation of sulphide ores by the extraction of 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 approx 1.9 Moz saleable gold and 369 kt of saleable copper in concentrate over a 14-year life of the mine.

At the declared commodity prices, the estimated copper and gold mineral reserves are equal to a total of 5.3 Moz gold equivalents.

The plant has a production capacity of 18kt of ore per day, or about 6.2 Mt or ore per year.

Location

The Cerro Corona Mine is located within a copper mining district in the Hualgayoc mining district of northern Peru. It is 40km north of the Yanacocha Mine, and 80km by road north of the departmental capital of Cajamarca in Northern Peru. Cjamarca is the place where Francisco Pizarro and his conquistadores captured Atahualpa the 1532 Inca emperor.

The property covers 1,600 ha but the mine itself was developed over an area of only 940 ha.

The mine is located in the highest part of the Western Cordillera of Andes close to 4,000 masl elevations.

Geology & Mineralization

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 is a typical porphyry-style of mineralization situated within the Hualgayoc mining district in the northern part of the Cajamarca province, a metallogenic province hosting prolific epidermal, porphyry and poly-metallic style mineralization. The mining area is characterised by moderate to moderately steep mountainous terrain with elevations ranging fro approx 3600-4000m above mean sea level.

The Cerro Corona copper-gold porphyry is one of 14 known Tertiary-aged porphyry CuAuMo deposits and 19 epithermal Au Ag deposits located in the Cajamarca metallogenic province (CMP) of northern Peru. There are two well-mineralised districts within CMP. These are the Yanacocha district in the south of the province, which is host to the largest producing gold mines in South Amercia, and the Hualgaryoc mining district in the north which is one of the oldest mining district in Peru, best known for its past silver production and more recent base metal production. This well-know district has been an important silver producing area since Inca times, with more than 50 Moz 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 Cerro Corona gold-copper deposit is hosted by a 600- to 700-meter diameter sub-vertical cylindrical- shaped quartz diorite porphyry stock emplaced into mid-Cretaceous limestone and marls. Within the porphyry, gold-copper mineralization is primarily hosted by extensive zones of stockwork veining. There are at least two phases of diorite placement, only one of which is mineralized. The non-mineralized diorite is generally regarded as the last phase, and is referred to as “barren core.” The latest re-modeling suggests that the Cerro Corona porphyry is probably comprised of four or five satellite stocks with the last two being barren. The intrusive has been emplaced at the intersection of Andean-parallel and Andeannormal (transandean) structures. 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. 

Mining & Operation

Cerro Corona became operational in the first quarter of fiscal 2009.

The Cerro Corona deposit is mined by conventional surface mining methods. The Final surface mine area is expected to cover some 900 by 1000m. The mining operation is extending from the crest of the original Cerro Corona hill, which peaked at 3964mRl, to a final depth at around 3610mRl.

Cerro Corona is mined via open pit methodology by conventional drill and blast with a truck and front-end loader fleet. Load-and-haul is by 90t dump trucks and 100t front-end loaders.

Cerro Corona is a contract mining operation - Minera San Martin carries out mining operations under the supervision of La Cima's mining and geological department.

Processing

The plant has been operating at near-stable conditions with the only influence of 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 types of ore 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.

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 sage cleaner flotation section.

The ore is treated in a conventional milling and sulphide flotation concentrator capable of treating 6.2 million tons per annum of ore and producing between 100,000 and 140,000 tons per annum of copper and gold containing concentrate. In 2011, average recovery factor was 65% for gold and 83% for copper.

The final concentrated is thickened and filtered before bing stockpiled for final shipment to the smelters. The mine has contracts with Japanese South Korean and German refiners.

Electricity is sourced from the national power transmission system at which the mine is linked through a 34 km transmission line.

Environment & Community

Water is obtained by retention of rainfall and pit dewatering - water is continuously recycled.

During 2010, Cerro Corona obtained OHSAS 19001 and ISO 14001 certification and is fully compliant with the international Cyanide Code. The remote operation means that local communities are particularly reliant on Gold Fields for socio-economic development, as well as basic infrastructure, such as roads and telecommunication.