Silver, lead and zinc

Underground operation

Oyón, Lima

4,500 masl

Started in 1975

Located in the District of Oyón, Province of Oyón, Region of Lima, Uchucchacua (100% BVN) is an underground operation discovered by Buenaventura that produces silver, lead, and zinc. It commenced operations in 1975. To date, it has produced over 259 M ounces of silver.

Geology: This is a silver-bearing deposit with base metals and a high content of manganese hosted in the carbonate rock of the Jumasha Formation from the Upper Cretaceous, related to intrusives from the Miocene. It consists of veins and replacement bodies associated with systems of NE-SW, E-W, and NW-SE structures. Of particular note are the Uchucchacua, Socorro-Cachipampa, Rosa, and Sandra faults, among others. Mineralogy is varied and complex, with the occurrence of silver in sulfides and sulfosalts, with abundant alabandite and manganese calcium silicates. Lead and zinc increase in proximity to the intrusives. Work is being done in the Socorro, Carmen-Casualidad, and Huantajalla Mines.

Mining: There are three mines in exploitation—Socorro, Carmen, and Huantajalla—whose production is extracted via the Luz and Master shafts. The exploitation methods used include overhand cut and fill and bench and fill, both mechanized, using low-profile equipment. The ore is transported by rail using locomotives and mining cars to the loading areas in the shaft, and to the concentration plant. The main access tithe mining areas is gained through a descending ramp. The barren material is recirculated as backfill to the pits, and the excess material is transported to the barren material deposit located on the surface. For the ventilation of the work, there are three main fans with a capacity of 300,000 cfm, and secondary fans for the explorations and developments. For mine drainage, there are two water pumping stations in series, with a capacity of 1,000 and 750 l/s, respectively, that evacuate water to level 4120, which exits to the surface through the Patón Tunnel, which measures 4.2 km long.

Metallurgy: The metallurgical process at Uchucchacua consists of two circuits: Circuit 1 has a capacity of 2,810 T/D, and consists of primary crushing, milling, and ore flotation, obtaining lead-silver, zinc-silver, and pyrite concentrates; while Circuit 2 has a capacity of 1,100 T/D, and consists of primary crushing, milling, and ore flotation, obtaining lead-silver, zinc-silver, and pyrite concentrates. The pyrite concentrates from both circuits are sent to the cyanidation plant, which has a capacity of 300 T/D. The cyanidation process is performed in tanks and thickeners. The solution obtained is treated using the Merrill-Crowe process, and the precipitate obtained is dried and smelted to finally obtain high-purity silver bars. The concentrates with a high manganese content produced at Uchucchacua are treated at the Río Seco leaching plant, for subsequent sale.

Current Treatment Capacity: 3,910 MTD

Note: As of december 31st of the year indicated.