The Loma Larga gold-copper-silver project is an underground multi-metals project being developed in Ecuador. INV Metals is developing the project, which has been selected by the Ecuadorian Government as one of the top five strategically important mining projects.
Feasibility study for the project was completed in November 2018 and a technical report was filed in January 2019. Construction of the project is expected to be started in early-2020, while first gold concentrate is scheduled to be produced by the end of 2021.
The project is expected to extract 2.6 million gold-equivalent ounces (Moz) per annum through its anticipated mine life of 12 years. It is expected to create 875 construction jobs and 450 operational jobs in Ecuador.
Loma Larga gold-copper-silver project location, geology, and mineralisation
The Loma Larga project area is broadly classified into three concessions namely Cerro Casco, Rio Falso, and Cristal, which extend in approximately 8,000ha. The Loma Larga deposit is entirely hosted in the Rio Falso concession and is surrounded by Gañarin and Girón faults.
The gold-silver-copper deposit and surrounding areas feature upper miocene volcanic and volcaniclastic rocks belonging to the Turi, Turupamba, Quimsacocha, and Tarqui formations. Majority of the rocks belong to the Quimsacocha formation, which comprise andesitic banded lava flows with phenocrysts.
The project is identified as a flat-lying, cigar-shaped body plunging in a western direction. It strikes in north-south direction and has a strike length of approximately 1,600m.
Mineralisation at Loma Larga is identified as high sulphidation epithermal style, containing hydrothermal fluids.
Loma Larga gold-copper-silver project reserves
The Loma Larga project is expected to contain reserves of approximately 13.98 million tonnes (Mt) grading 4.91g/t gold, 29.6g/t silver, and 0.29% copper. It is estimated to contain 2.2Moz of gold, 13.3Moz of silver, and 88 million pounds (Mlb) of copper.
Mining activities at Loma Larga
Transverse longhole stoping method of mining, followed by paste back-filling, will be used at the deposit. Drift and fill method is also proposed to be employed to extract ore from narrow edges.
Initial mining operation at Loma Larga is expected to be at the rate of 3,000 tonnes per day (tpd), which will be increased to 3,400tpd from the fifth year. The underground mine will be accessed through a 1.2km ramp, which will also be used for hauling waste and ore as well as for ventilation purposes.
Ore processing at Loma Larga project
Ore will be trucked approximately 3.5km from the portal to the process facilities, which will employ two stages of crushing – primary and secondary, followed by single-stage ball milling.
Operating in closed circuit with a pair of hydrocyclones, the ball mill will mix lime and low-pH process water to the crushed ore to achieve a standard mill pulp pH level. Underflow from the mill will be sent back to the grinding circuit, while the overflow will be sent to a grinding product thickener.
Underflow from the thickener will be treated with lime and forwarded to rougher flotation in conventional tank cells. The resulting rougher concentrate will be re-grinded in a vertically stirred media mill and forwarded to copper cleaner flotation. It will then be cleaned in two stages, with the resulting copper concentrate being thickened and filtered before being packaged in bags for shipment.
The copper tails thickener underflow will be mixed with low-pH process water at the pyrite rougher flotation conditioning tank, while the resulting overflow will be forwarded to the pyrite rougher flotation tank cells.
The produced rougher concentrate will be further re-grinded and cleaned in a flotation circuit featuring six air flotation cells. The final concentrate from the first cleaner cell will be thickened, pressure-filtered, dewatered and stored before shipping to customers in containers.
Infrastructure facilities at Loma Larga
Access to the Loma Larga gold-copper-silver project site is through an 11.6km-long main access road from San Gerardo, which is proposed to be upgraded in two phases. New roads will be built to connect the portal site, processing plant, and tailings storage facility.
Power for operations will be sourced from a 69kV/25MVA main supply line, owned by CENTROSUR, while power supply during construction will be sourced from the 2MVA, 22kV supply line from San Fernando.
Natural run-off will be the main source of water for the project, while mineral processing activities will be undertaken using the available contact water.
The feasibility study of the Loma Larga gold-silver-copper project was prepared by a consortium of consultants, including DRA Americas, RPA, Mine Design Engineering, Itasca Denver, NewFields, Paterson & Cooke, and SGS.