The Cerro Verde mine is operated by Freeport-McMoRan Inc. (FCX) through a majority owned subsidiary, Sociedad Minera Cerro Verde S.A.A. (SMCV).
FCX holds a 55.08% ownership interest in SMCV, with the remaining 44.92% held by SMM Cerro Verde Netherlands B.V. (SMM) (21.00%), Compañia de Minas Buenaventura S.A.A. (BV) (19.58%), and other stockholders whose Cerro Verde shares are publicly traded on the Lima Stock Exchange (4.34%).
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Summary:
The Cerro Verde mine is a porphyry copper deposit that has oxide and secondary sulfide mineralization, and primary sulfide mineralization. The predominant oxide copper minerals are brochantite, chrysocolla, malachite and copper “pitch.” Chalcocite and covellite are the most important secondary copper sulfide minerals. Chalcopyrite and molybdenite are the dominant primary sulfides.
The Cerro Verde mining district comprises a copper-molybdenum porphyry cluster that includes a series of deposits (CV, SR, and CN) which are related to calc-alkaline intrusions (dacite to monzonite porphyry) and quartz-tourmaline hydrothermal breccia bodies.
In general, these deposits are low grade and high tonnage, genetically related to igneous epizonal intrusions and characterized by multiple events from a parental magmatic chamber, which are distributed along the Incapuquio fault system corridor.
The three deposits are currently in production with each having similar characteristics. The deposits are differentiated by the level of erosion, alteration intensity and magmatic history.
The Cerro Verde mine encompasses the Cerro Verde (CV), Santa Rosa (SR), and Cerro Negro (CN) ore deposits.
The CV and SR deposits are located in the core of a gently folded west-northwest striking basement-cored anticline or southwest-tilted structural block. The anticlinal axis parallels the Tinajones fault system, a regional north 60-degree west to east-west striking fault zone/lineament. The influence of this structural zone is reflected in the copper grade distribution at depth.
A series of parallel north 60-degree east, steeply northwest dipping faults were mapped in the CV and SR pits. Copper contours at depth also define several north-south trends suggestive of underlying structural control. The general fault pattern in the district suggests a major left-lateral fault zone. No major offsets in copper grade contours have been noted, suggesting that post-mineral faulting was minor in the district. The northwest-trending and southwest-dipping Charcani Gneiss-Yarabamba Granodiorite contact played an important role in the localization of the productive porphyries in the Cerro Verde mine area.
Alteration and Mineralization
In the Cerro Verde mining district, mineralization is directly linked to multiple igneous intrusive events. The resulting hypogene mineralization is dominantly chalcopyrite with minor bornite. Retrograde events resulted in a slight increase in chalcopyrite and precipitation of molybdenite. Supergene processes formed a profile containing zones of leached capping, oxide copper mineralization, chalcocite enrichment, and a mixed chalcocite-hypogene transition zone.
The majority of the oxide and secondary sulfide mineralization at CV and SR has already been mined.
The hypogene ore grade shell with a 0.2% total copper grade (TCu) is larger and has a greater horizontal to vertical aspect ratio at SR than the CV deposit. The grade shell at CV is more compact with a greater vertical component. Encompassing both deposits, this grade shell measures approximately 5.6 kilometers in length trending northwestsoutheast, 1.6 kilometers in width and 2.0 kilometers in depth, based on current drill hole lengths.
There are several breccia types at CV and SR that typically contain elevated copper grades. Mineralization associated with breccias is more prevalent at SR.
Lead, zinc, and arsenic are associated mainly with mineralized faults, veins, and breccias. These elements are included in the geologic modelling because elevated values in the copper concentrates can result in smelter penalties.
CN has very well-developed oxide mineralization. The predominant mineral is chrysocolla with lesser amounts of tenorite and malachite. Mineralization occurs mainly in fractures. Moderate amounts of specularite occur as a replacement of the matrix or as fragments in the tourmaline breccia.