Mina Justa is a $1.6bn greenfield copper project under construction near Marcona, approximately 400km south-east of Lima, in the Nazca province of Peru. The project is being developed by Marcobre, a joint venture between Minsur (60%), a mining company based in Peru, and Alxar (40%), a subsidiary of Empresas Copec.

The definitive feasibility study (DFS) for the Mina Justa project was completed in June 2009, whereas the construction was started after Marcobre secured $900m of project financing in August 2018.

Scheduled to commence operation in 2021, the Mina Justa copper project is expected to process 12 million tonnes (Mt) of oxide ore and 6Mt of sulphide ore a year to produce up to 102,000 tonnes per annum (tpa) of copper concentrates and 58,000tpa of copper cathode, over 16 years of mine life.

Mina Justa geology and  mineralization

The Mina Justa copper project consists of two deposits, namely Mina Justa and Magnetite Manto, in the Ica region of the southern Peruvian coastal belt. Separated from each other by 1km of barren ground, both the deposits are hosted within the Jurassic Upper Río Grande Formation.

The bigger Mina Justa deposit extends for 2.1km in north-south direction and 1.5km in west-east direction. The thickness of the ore body is up to 150m. The mineralization occurs near  surface in the northern and western parts of the deposit, while it extends up to 550m depth in the south-eastern parts.

The smaller Magnetite Manto deposit represents a tabular ore body measuring 700m-long and 350m-wide, with its thickness ranging between 25m and 35m.

Mining and ore processing

Mining will be carried out at two open-pits involving drill-load-blast-haul operations. The mining fleet will include crawler-mounted diesel drilling rigs, 20m³ backhoes, and 220t haul trucks.

The ore processing infrastructure includes a six million tonne per annum (Mtpa) copper sulphide concentrator for treating sulphide ore and a 12Mtpa vat leach solvent extraction and electro winning (SxEw) facility to treat oxide ore.

A common crushing circuit involving 11 crushers including jaw, gyratory, cone and high-pressure grinding roll (HPGR) types will be installed to provide ore feed for both the sulphide and oxide plants.

The Vat leaching train at the oxide plant will comprise 15 concrete vats measuring 46mx36mx14m each. The ore-loaded vats will be flooded with sulphuric acid to recover the copper for further processing.

Ore at the sulphide plant will undergo comminution, floatation, and concentration for the production of copper concentrates.

Infrastructure facilities

The Mina Justa mine site will be accessed via a new 10km-long road connecting the National Route 30. A construction camp to house 990 people has been built approximately 4.4km south-west of the plant area.

The water requirement for the project will be met through a 36km-long seawater pipeline originating near the Marcona Port.

The acid required for the plant will be received through shipments and stored in storage tanks near the Marcona Port, before being delivered to the site by trucks.

The electricity to the mine site will be transmitted through a dedicated 15km-long 220kV overhead power line connecting Red de Energía del Perú’s (REP) Marcona substation.

Financing for Mina Justa project

Marcobre secured $900m of multi-source debt financing for the development of the Mina Justa copper project in August 2018.

KfW IPEX-Bank, the mandated lead arranger, provides $300m for the project. The other lenders for the project include Export Development Canada (EDC), Export-Import Bank of Korea (KEXIM), Australia’s export credit agency Export Finance and Insurance Corporation (Efic), and six other international and Peruvian banks.

The Mina Justa financing was recognized as Americas Mining Deal of the Year 2018 by the Project Finance International (PFI).

Contractors involved

Ausenco is the engineering, procurement, construction, and management (EPCM) contractor for the Mina Justa copper project. Ausenco also carried out the pre-feasibility study (PFS) of the project previously.

GRD Minproc prepared the definitive feasibility study (DFS) report for the project in 2009.

Snowden Mining Industry Consultants was engaged for geology and resource modeling, while Transmin Metallurgical Consultants and Hydrometal provided metallurgical consultancy services during the feasibility study phase of the project.

Indec provided vat leaching design, while Knight Piesold was the consultant for geotechnical studies and the tailings storage facility of the project.

Drill hole collar and gyroscopic downhole surveys were conducted by independent surveying contractors Proyectistas Tecnicos y Servicios of Lima and Comprobe.

GMI was the consultant for infrastructure facilities, while Vector Peru carried out environmental and social impact assessment of the project.