The Neves-Corvo poly-metallic base metal mine is located 220km south-east of Lisbon, in the Castro Verde Municipality of the Alentejo region in Portugal. It is owned and operated by Lundin Mining’s Portuguese subsidiary Somincor.
The mine began copper production in 1989 and zinc production in 2006. It is estimated to produce up to 45,000t of copper and 79,000t of zinc in 2018.
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The Neves-Corvo mine was acquired by Lundin Mining as part of its merger with EuroZinc Mining in 2006. It includes five deposits namely Zambuja, Graca, Neves, Corvo, and Lombador Phase 1 (LP1) and Lombador Phase 2 (LP2).
Lundin Mining is currently working on a $298m Zinc Expansion Project (ZEP) at the mine to increase the zinc production to 150,000t per annum. Approved by the company in 2017, the ZEP development was granted Project of National Interest (PIN) status by the Portuguese government. A feasibility study on the project was completed in September 2018.
The full production of zinc at the Neves-Corvo is scheduled to start upon completion of the expansion in the fourth quarter of 2019.
Geology and mineralisation
The mine lies in the western part of the Iberian Pyrite Belt (IPB) and its mineral deposits are categorised as the volcano-sedimentary massive sulphide (VMS).
Neves, Corvo, Graca, Zambujal, Lombador, Semblana and Monte Branco are the seven massive sulphide mineralisation zones found in the area. Mineralisation occurs at zones at depths between 230m and 1,400m below the the surface.
It is classified into Rubane mineralisation consisting alternations of shales and breccias, as well as massive sulphide mineralisation, and stock-work sulphide mineralisation.
Neves-Corvo mine reserves
The proven and probable copper mineral reserves of the Neves-Corvo mine were estimated to be 30,349t grading 2.3% copper, 0.7% zinc, 0.2% lead and 35g/t silver, as of June 2018.
The proven and probable zinc reserves were estimated at 30,384t grading 0.3% copper, 7.7% zinc, 1.8% lead and 65g/t silver.
Mining methods
The Neves-Corvo mine uses underground mining techniques such as drift-and-fill and bench-and-fill stoping. It is accessible through the main ramp, which enables the movement of the workers and vehicles inside the mine.
Ore is transferred through a concrete shaft with a diameter 5m, depth 600m complete with rope guides, a double drum winder (2.5MW), and two skips of wet load capacity 17.8t.
The upper underground crusher facility located at the 700 Level contains four 1,500t storage bins and a 600t/h jaw crusher handling ore from the Upper Corvo, Neves, Zambujal and Graça deposits.
The lower section of the mine that stretches from 700 Level to 550 Level is serviced by a second crusher unit at the 550 Level. It crushes ore from the Lower Corvo and Lombador deposits.
The crushed ore is gathered by three storage bins, transferred to a short conveyor and then carried by a TP12 inclined conveyor to the 700 Level bins.
The underground mining at the new LP2 section of the mine involves optimised bench-and-fill method for zinc stopes, bench-and-fill for the copper stopes and limited drift-and-fill stopping technique.
Processing at Neves-Corvo poly-metallic mine
The processing facility at the mine includes a 2.6Mtpa copper plant and a 1.1Mtpa zinc plant. The zinc plant is currently undergoing a major expansion to more than double its processing capacity to 2.5Mtpa.
A crushing plant with a throughput of 350t/h crushes the run-of-mine (ROM) ore, which is then sent to a primary grinding circuit comprising a rod mill as well as primary and secondary ball mills with two hydrocyclones.
The secondary grinding circuit comprises a rod mill in open circuit and a primary ball mill in closed circuit with a hydrocyclones.
The slurry from the primary grinding circuit will be fed to the flotation circuit after passing through two aerator conditioners.
Two rows of additional zinc and lead rougher/scavenger flotation circuits will be added to the processing facility as part of the current expansion.
The three-stage copper cleaning uses 17m³ cells, producing a concentrate with approximately 24% copper. The final copper concentrate is sent to a 40m-diameter thickener, while the zinc concentrate is transferred to the zinc plant thickener.
The mine has covered warehouses with a storage capacity of 15,000 wet metric tonnes (wmt) for copper concentrates and 12,000wmt for zinc concentrates.
Infrastructure
Concentrates will be transported by rail to the private harbour and loading facility at Setúbal. The mine is also connected by a highway and Faro international airport, which is located 80km away from the mine site.
Cerro da Mina reservoir with a capacity of 1.4Mm³ was constructed to store the surplus water in the mine. A water treatment plant with a capacity of 950m³/h was also constructed in the site.
The mine receives power through a 22.5km-long, 150kV, 50MVA overhead line connected to the national grid.
Contractors involved with Neves-Corvo mine expansion
Amec Engineering was awarded an engineering and procurement contract by Lundin for the zinc expansion project.
Lundin signed a contract with Metso for the supply of a jaw crusher, flotation cells and filter presses, in September 2017.
The feasibility study for the Neves-Corvo ZEP was prepared by SOMINCOR in April 2017.
The environmental impact assessment (EIA) for the project was prepared by PROCESL in November 2016.
The environmental, health & safety and product stewardship audit was prepared by ERM in April 2017.
