The annual average production from the Loma Larga mine is expected to be 139,958 ounces of gold, 794,561 ounces of silver and 5.1 million pounds of copper.
The Loma Larga underground mine is expected to commence production in 2022.
The Loma Larga project is located near the city of Cuenca in Ecuador. Image courtesy of H.Morisse.

Loma Larga is an underground gold-copper-silver project located in the Azuay province of Ecuador. INV Metals, a Canadian mineral resource company, is the owner and developer of the multi-metals project.

The feasibility study (FS) for the project was completed in November 2018 followed by the publication of a technical report in January 2019, while the results of an updated feasibility study were announced in March 2020.

The Loma Larga project is expected to produce 139,958 ounces (oz) of gold, 794,561oz of silver and 5.1 million pounds (Mlb) of copper annually over an estimated mine life of 12 years.

The initial pre-production capital expenditure for the project is estimated to be £255m ($316m).

The environmental impact study (EIS) report for the project is expected to be submitted to the Ministry of Environment (MAE), Ecuador in 2020, while the construction works are expected to be started in 2021 with the start of production expected in 2022.

Location, geology, and mineralisation 

The Loma Larga gold-copper-silver property is situated approximately 30km southwest of Cuenca, the capital city of Azuay province, Ecuador, while the town of Giron is located approximately 15km south of the project site.

The Loma Larga project comprises three concessions including Cerro Casco, Rio Falso, and Cristal that are spread over a total area of approximately 8,000ha. 

The Loma Larga deposit is located in the southern part of the Chaucha continental terrane, within the Cordilleran physiographic province.

Situated between the Gañarin fault to the northwest and the Girón fault to the southeast, the Loma Larga ore body lies beneath the Upper Miocene volcanic and volcaniclastic rocks, of the Turi, Turupamba, Quimsacocha, and Tarqui formations.

Loma Larga is a north-south striking, cigar-shaped ore body characterised by high sulphidation epithermal gold-copper-silver mineralisation that occurs starting from 120m beneath the surface along a strike length of 1.6km. The thickness of the mineralised zone is up to 60m. 

Loma Larga gold, copper and silver reserves 

The Loma Larga project is estimated to hold 13.9 million tonnes (Mt) of proven and probable ore reserves grading 4.91g/t of gold, 29.6g/t of silver and 0.29% copper.

The underground mine is estimated to contain  2.2 million ounces (Moz) of gold, 13.27Moz of silver and 88Mlb of copper.

Mining at Loma Larga  

The long-hole stoping method with 20m-wide, 25m-high and 20m-long stope sizes will be employed for extracting the majority of ore materials in the underground mine, while drift-and-fill mining method will be employed for certain narrow mineralised zones in the lower portion of the deposit.

The Loma Larga underground mine will be accessed through a 1.2km-long, 5m-high and  5m-wide ramp which will also be used for the haulage of waste and ore,  as well as for ventilation.

Ore extraction at the underground mining will be carried out at a rate of 3,000 tonnes per day (tpd) during the initial four years of operation which is planned to be increased to 3,400tpd from the fifth year onwards. 

Ore processing  

The run-of-the-mine (ROM) ore will be trucked via road to a nearby processing plant located outside the Giron canton.

The ore material will undergo two-stage crushing and a ball mill before passing through a two-stage sequential flotation circuit to recover gold, silver, and copper into two separate saleable concentrates.

The floatation circuit at the processing plant will involve two stages of copper cleaner flotation and one stage of pyrite cleaner flotation.

The tailings from the processing plant will be filtered and sent to a tailings storage facility (TSF) or it will be sent to the paste backfill circuit for reuse as mine backfill. 

Infrastructure facilities 

The Loma Larga project can be accessed through an 11.6km-long main access road connecting San Gerardo. New roads will also be built to connect the mine site, processing plant, and the TSF.   

The electricity for the project will be sourced through a connection with the CENTROSUR-owned 69kV/25MVA transmission line between Lentag and Victoria del Portete.

The main substation is planned to be built at the processing plant site where the electricity will be stepped down to 22kV for distribution to other facilities at the mine site. 

The water requirement for the operation will be mostly met through mine dewatering.

Contractors involved 

DRA Americas provided mineral reserves estimates, mining and financial modeling, as well as consulting services related to metallurgy and ore processing, while Rock Engineering Consulting Services provided geotechnical design services.

Roscoe Postle Associates (RPA) provided the mineral resources estimate for the project.

Itasca Denver was engaged for hydrogeology and water quality studies, while NewFields provided the tailings storage facility design and Paterson & Cooke was the paste backfill consultant.

Other consultants engaged for the feasibility study of the project were Environmental Resources Management (ERM) and SGS Canada.