Salares Norte is an open-pit gold-silver mine planned to be developed in the Atacama Region of Chile. Gold Fields, a South African gold mining company, is the owner and operator of the project.
Gold Fields discovered the Salares Norte epithermal gold and silver deposit in 2011 and carried out extensive drilling until 2017. A definitive feasibility study (DFS) outlining the maiden reserves estimates of the deposit was completed in December 2018.
The project is expected to produce 3.7 million ounces (Moz) of gold equivalent over an initial mine life of 11.5 years with an estimated capital expenditure of £640m ($834m).
The Atacama Environmental Assessment Commission approved the environmental impact assessment (EIA) report for the project in December 2019. The construction works are expected to commence in the fourth quarter of 2020 with the start of operations expected in the first quarter of 2023.
The Salares Norte gold-silver mine is expected to produce up to 450,000 ounces (oz) of gold equivalent a year during the first seven years of operation.
Location, geology, and mineralisation
The Salares Norte project is situated on the northern part of the Maricunga Belt in the Atacama Region of Chile, approximately 190km east of Diego de Almagro. The gold-rich Maricunga Belt lies in the Andean Cordillera in northern Chile and it predominantly comprises Cenozoic volcanic rocks composed of eroded strato-volcanos, pyroclastic rocks, and volcanic domes.
The Salares Norte project area consists of two deposits namely, Brecha Principal and Agua Amarga deposits that are separated by a distance of 500m.
The gold-silver mineralisation at Salares Norte is associated with high-sulphidation epithermal system with high-grade oxides. The mineralisation is found hosted in a breccia complex along two andesitic and dacitic volcanic domes.
Gold and silver reserves at Salares Norte
The total probable reserves at Salares Norte are estimated to be 21.1 million tonnes (Mt) grading 5.13g/t gold and 57.94g/t silver and containing 3.5Moz of gold and 39Moz of silver. The Brecha Principal deposit is estimated to hold 15.4Mt of ore reserves while the Agua Amarga deposit accounts for 5.7Mt.
The total indicated and inferred resources at both the deposits are estimated to be 25.5Mt grading 4.76g/t gold and 53.13g/t silver.
Mining and ore processing
Salares Norte will be a conventional open-pit mining operation involving drilling, blasting, loading and hauling methods for ore extraction.
The overburden will be pre-stripped at the rate of 50Mt per annum (Mtpa) during the first two years while the subsequent mining rate will also be 50Mtpa. Gold Fields in considering contract mining for the project.
The extracted ore will be sent to a nearby processing facility where it will undergo crushing, two-stage grinding and leaching before passing through counter-current decantation (CCD), carbon-in-pulp (CIP) and Merrill Crowe processes for the recovery of gold and silver. The tailings will be filtered and sent to a tailing storage facility.
The throughput capacity of the plant will be 2Mtpa and the life of mine (LOM) average recovery of gold and silver will be 92.7% and 67.5% respectively.
The Salares Norte project can be accessed from the El Salvador Airport located 180km away from the site.
The electricity requirement for the project will be met through a 17.5MW diesel power station at the site, while the water requirement will be met through underground boreholes in the vicinity.
The other infrastructure facilities for the project will include heavy mining equipment (HME) workshop, reagents warehouse, a tailings filter plant, a fuel storage area, as well as raw and potable water storage facilities.
Flour was the processing and infrastructure consultant while NCL provided mine design services for the project.
SRK Consulting provided geotechnical services as well as design services for the waste and tailings storage facilities.