Lagunas Norte gold-silver mine is located in the District of Quiruvilca in the Santiago de Chuco province and the La Libertad region of north central Peru. Barrick owns and operates the mine through its Peruvian subsidiary Minera Barrick Misquichilca (MBM).
Operations at the gold-silver mine commenced in March 2005, and approximately nine million ounces (Moz) of gold and 9Moz of silver were produced until December 2015.
Barrick is currently undertaking a refractory project for expanding the Lagunas Norte mine and to process the sulphide resources below the oxide orebody in the current open pit.
Lagunas Norte mine extension details
The proposed Lagunas Norte extension project will be developed in two phases to extend the mine life up to 2029.
The first phase involves the construction of a grinding and carbon-in-leach processing circuit for treating the remaining carbonaceous oxide material at Lagunas Norte. The second phase will include the installation a flotation and autoclave processing circuit to treat refractory material.
Environmental permits for the first phase extension are already obtained with detailed engineering expected to be completed by 2019. Production from the first phase expansion is expected to start in 2021.
Detailed engineering and environmental permitting for the facilities under the second phase extension are expected by 2023, with construction and commissioning expected by 2026 and first production expected by 2027.
The scoping study for the refractory project was completed in June 2015, and a pre-feasibility study (PFS) was completed in December 2015.
The PFS of the refractory project supports the conversion of approximately 2.1Moz of measured and indicated refractory sulphide gold resources to mineral reserves.
Lagunas Norte geology and mineralisation
The Lagunas Norte mine is located on the Alto Chicama property in north-central Peru and lies approximately 90km east of the coastal city of Trujillo. It is located on the western edge of the Peruvian Andes at an elevation of 4,000 to 4,260 metres above sea level (masl).
A thick sequence of Mesozoic marine clastic and carbonate sedimentary rocks is found at the region. The deposit displays features of both tertiary volcanic rocks and basement Cretaceous sedimentary rocks with variable quantities of overlaid carbonaceous, fine grained sedimentary rocks.
Mineralisation of Lagunas Norte is finely disseminated and is contained within siliclastic sedimentary strata. It is believed to have formed through an occurrence of multiple volcanic and hydrothermal events.
Most of the mineralisation is hosted in both the tertiary volcanics of the Calipuy Group and the underlying Cretaceous sedimentary rocks of the Chimú Formation.
Lagunas Norte gold mine reserves
As of 31 December 2015, the Lagunas Norte Gold mine was estimated to contain proven and probable oxide reserves of 63.6 million tonnes (Mt). Contained gold and silver are estimated to be 3.07Moz grading 1.82g/t Au and 9.8Moz grading 4.77g/t Ag respectively.
Mining and ore processing at Lagunas Norte
Mining at Lagunas Norte is based on conventional open pit truck/shovel heap operation. The mining operations are conducted on a mountain top between elevations of 3,800masl and 4,200masl.
Ore at the Laguna Norte processing plant undergoes a two-stage crushing through a 42,000tpd conventional crushing circuit. The crushed ore is loaded into haul trucks and transported to the leach pad for heap leaching.
The pregnant leach solution is pumped to the Merrill Crowe and/or the carbon-in-column (CIC) plant before being sent to Merrill Crowe cementation plant for recovery of the precious metals.
A 6,000 tonnes per day (tpd) grinding-flotation-autoclave and carbon-in-leach processing facility will be installed for treating the refractory material. The processing facility will require an investment of approximately $640m.
The Lagunas Norte mine is accessed from Trujillo through public paved roads. Power supply for the mine is sourced from a privately owned power generation company through high-voltage power lines connected to the national power grid in Trujillo.
The new processing plant for the refractory mine extension project at Lagunas Norte will utilise the existing plant and water supply infrastructure.
The main source of water for the Lagunas Norte operation is the nearby Laguna Negra lake. A positive water balance is maintained by harvesting rain water into two small lakes for reuse. Water treatment facilities at the mine include a cyanide destruction plant, acid rock drainage facility and a treatment plant.
Offtake of gold and silver produced at Lagunas Norte
Barrick International (Barbados) Corporation (BIBC) will purchase the gold and silver doré produced at Lagunas Norte.
Roscoe Postle Associates prepared the independent technical report of the Lagunas Norte gold mine.
A water management group has been appointed for dewatering including pumping, distribution, delivery and disposal.