The Quellaveco deposit, located near the northern end of the Paleocene to early Eocene porphyry copper belt of the central Andes (Sillitoe, 1988; Clark et al., 1990), is centered on a multiphase quartz monzonite porphyry stock emplaced into an equigranular granodiorite pluton, which itself cuts rhyolitic volcanic rocks assigned to the Late Cretaceous to early Paleocene Toquepala Group (Estrada, 1975; Guerrero and Candiotti, 1979; Candiotti, 1995). The pluton, which crops out over >3 km2 in the vicinity of the Quellaveco stock, as well as extending northward beneath postmineral ignimbrite and gravel cover, is part of the granodioritic to monzogranitic Yarabamba superunit of the Coastal batholith (Pitcher, 1985). Phenocrysts in the porphyries are made up of abundant plagioclase, quartz, and biotite, plus scattered K-feldspar and hornblende, all surrounded by aplitic groundmass.

Potassic (biotite-K-feldspar) and sericitic (quartz-sericite) alteration, the former generally overprinted and partly obliterated by the latter, developed extensively throughout much of the quartz monzonite porphyry stock and immediately surrounding granodiorite, and both contain veinlet and disseminated chalcopyrite. The potassic alteration is transitional outward in the precursor granodiorite to a pyrite-bearing propylitic assemblage, which defines the periphery of the system (Estrada, 1975; Candiotti, 1995; Kihien, 1995). Fluid inclusion studies showed that the main potassic and sericitic ........

Mining from the Quellaveco deposit will involve excavation of a huge open-pit. The final pit dimensions are anticipated to be: approximately 3000m (N-S) by 1700m (E-W), and 930m deep.

Mining of the ore body by open pit methods will require diversion of the Asana River around the Quellaveco deposit via a canal and tunnel system 7.2 km long, returning the flow downstream of the proposed waste rock disposal area.

Excavation of the pit will produce more than a million tons of waste rock, which will be deposited in the Asana River riverbed, downgradient of the open pit and the subsequent pit lake. Waste rock piles will reach an average height of 320m.

After mine closure, the pit will fill with water forming a lake with a maximum depth of about 384m.

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The primary crusher will be located adjacent to the pit in the Quellaveco valley, from where ore will be conveyed to a coarse ore stockpile in the adjacent Papujune valley.

The processing will be similar to that used at other copper porphyry processing facilities around the world, and will be essentially the same as that performed at SPCC’s Cuajone and Toquepala facilities.

These facilities use cyanide as one of the main flotation reagents to separate the copper from molybdenum and selected other metals.

MQSA decides to commercially extract copper from the waste rock piles using leaching procedures.