Chile’s El Teniente deposit is the largest known porphyry Cu-Mo orebody (>70 Mt Cu), and is genetically related to Late Miocene–Early Pliocene igneous activity on the western slopes of the Andean Cordillera (cf. Howell and Molloy, 1960, Camus, 1975, Cuadra, 1986, Skewes and Stern, 1995). The deposit is 2700 m long by 1000 to 1700 m wide and is elongated in a N-S direction, with a recognized vertical extent of about 1800 m. Approximately 80% of the copper at El Teniente is distributed within a stockwork of mineralized veinlets and minor hydrothermal breccias within pervasively altered andesites, basalts and gabbros that are part of the Upper Miocene country rocks. Two intrusive bodies occur within the deposit, the Sewell Diorite (actually a tonalite) in the southeast part of the orebody and the dacitic Teniente Porphyry in its northern part. The Teniente Porphyry occurs as a north-south trending dike 1500 m long and 200 m wide. Minor quartz-diorite or tonalite intrusions known as the Central Diorite and the Northern Diorite occur along the eastern side of the deposit. Hydrothermal breccias commonly occur along the contacts of intrusive bodies with the country rocks. The Braden Breccia is a conspicuous diatreme in the center of the deposit that forms a pipe 1200 m in diameter at the surface, narrowing to 600 m at a depth of 1800 m. The Braden diatreme pipe is poorly mineralized (~0.3% Cu), but it is surrounded by the copper-rich Marginal Breccia, a discontinuous rim of tourmalinematrix hydrothermal breccia.

Latite dikes intrude El Teniente, some forming altered ring dikes that encircle the Braden breccia pipe. After mineralization had ceased, the southern section of the deposit was cut by a 3.8 ± 0.3 Ma lamprophyre dyke, marking the end of igneous activity (Cuadra, 1986). Biotitedominated K-silicate alteration is widespread within the orebody. In contrast, pervasive phyllic alteration is restricted to ‘diorite’ intrusions, and to the Braden and Marginal breccias. Phyllic alteration primarily occurs as quartz-sericite haloes of quartz–sulfidesulfate veinlets within the perimeter of the orebody, and slightly overprints potassic alteration. Propylitic alteration occurs largely peripheral to ore-grade rock. The relatively restricted development of phyllic alteration and the occurrence of the central breccia conflict with the classic porphyry copper model of Lowell and Gilbert (1970), but El Teniente may be regarded as a “variation on a theme” of the classic model, as suggested by Gustafson and Hunt (1975).

A typical level model used at El Teniente mine: block caving, production, ventilation, transport and crushing.

Concentration
During the concentration process, which takes place in the industrial areas of the Colón and Sewell Divisions, the ore is reduced in size through the use of crushers and mills, where it is converted into a fine powder that is mixed with water and chemical reagents to form a slurry that enters the flotation stage. Here, a foam is produced to which copper and molybdenum particles adhere, separating them from the rest of the sterile material.

Smelting
In the smelter, the concentrate goes to a plant that extracts the humidity and, through a pneumatic transport system, it arrives at the Teniente Converters for the melting process. The main product of these converters is a white metal, which contains 75% copper. This white metal is then poured into the Pierce Smith converters, where the conversion process begins that gives rise to blister copper and from which fire-refined copper or RAF and anodic copper are finally obtained.