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Location: 47 km SW from Cusco, Peru
Av. Pardo y Aliaga 699, Oficina 901B San IsidroLimaPeru
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The Ccalla and Azulccacca zones of the Cotabambas deposit are considered to be examples of porphyry copper deposits. The two host porphyries cover an area about 2.5 km long and 1.5 km wide.Mineralization occurs in hypogene, supergene enrichment and oxide zones. A welldeveloped leached cap hosts the oxide mineralization. Sulphide mineralization occurs below the base of the leached cap. This zonation is considered to be typical of porphyrystyle copper and porphyry-style copper–gold deposits.Hypogene mineralization in the Project area has been intersected at depths from approximately 20 m from surface to depths of over 500 m from surface.Hypogene copper–gold–silver mineralization is best developed with pyrite mineralization in quartz–sericite-altered quartz monzonite porphyry dykes running parallel to the north north-east trending structural corridors at Ccalla and Azulccacca. Mineralization occurs as disseminated chalcopyrite and pyrite, pyrite-chalcopyrite stringers or veinlets and quartz chalcopyrite pyrite veinlets. Local patches of hypogene mineralization are developed in diorite, peripheral to the quartz monzonite porphyry, where the north–northeast-trending structural system passes within 10 to 20 m of the diorite–porphyry contact. Chalcopyrite mineralization intensity decreases and disseminated pyrite mineralization increases distal to the higher grade parts of the hypogene zone. Sulphide mineralization consists of chalcopyrite and pyrite and gold grades are strongly correlated to copper grades in the hypogene zone. Some occurrences of bornite have been noted in deeper portions of the hypogene zones. Silver grades are not as strongly correlated to copper grades as they are to gold grades, but are generally elevated where copper–gold mineralization is present. Zones of high-grade chalcocite mineralization with lesser covellite and chalcopyrite occur at the top of the hypogene sulphide mineralization, and at the base of the leached cap. Supergene zones occur at Ccalla and Azulccacca and are characterized by high chalcocite content, correspondingly high cyanide-soluble copper assay grades and total copper grades that are generally >1%. Oxide mineralization occurs in the leached cap of the Ccalla and Azulccacca deposits. Iron oxides and oxy-hydroxides replace pyrite, and oxide copper–gold mineralization occurs as patches of green copper oxides, typically chrysoscolla, malachite and broncanthite. Copper oxides occur as coatings on disseminated chalcopyrite grains and as fill in fractures and veinlets. Lenses of oxide copper–gold mineralization having lateral extents of 100 to 200 m and thicknesses of 10 to 50 m have been mapped in outcrop and intersected in core drill holes.Oxide gold mineralization has been defined in a lens in the Azulccacca area, but has also been intersected in short, isolated 1 to 5 m intervals in other parts of the leached cap of the deposit. Oxide gold mineralization is associated with limonite and occurs near major structures cutting the hypogene sulphide zone that are associated with the quartz monzonite porphyry.
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