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Geology Quiulacocha TSF
Quiulacocha is a large TSF (surface area 114 ha) located to the south-west of the Raúl Rojas pit. The Quiulacocha TSF holds approximately 70 Mt of process tailings of the Cerro de Pasco mine. A copper concentrator plant entered production in January 1921 with tailings deposited directly into the Quiulacocha lagoon. Subsequently, the lagoon was used to store tailings from the processing of Zn, Pb, Ag mineralization in the Paragsha and San Expedito Process Plants until 1992. Geophysics undertaken in 2020 indicated depth of tailings up to 40m with average depth estimated between 20 to 25m.
The tailings are partially overlain by the Excelsior stockpile. Two different types of tailings were distinguished:
- Cu-rich sulphide tailings, and
- Zn-Pb-rich sulphidic tailings.
The Cu sulfide tailings are characterized by a mineralogy composed of pyrite, enargite, chalcopyrite, sphalerite and galena. The Zn-Pb-rich sulfidic tailings are defined by a mineralogy composed of pyrite, sphalerite, galena and pyrrhotite.
The Quiulacocha Tailings have developed an oxidation zone with a thickness ranging from several mm to a maximum 25 cm (pH =1.9 to 4.8). The mineralogy of the oxidation zone is characterized by residues of pyrite, quartz and secondary phases such as jarosite, gypsum, siderite, and Fe-hydroxides, mainly goethite.