Summary:
The Chuquicamata district includes the Chuquicamata and Radomiro Tomic megadeposits, the exotic copper deposit Mina Sur, the newly developed Ministro Hales mine (formerly known as Mansa Mina) located 5.5 km south of Chuquicamata, and the deposits of the Toki cluster (Toki, Genoveva, Quetena, Miranda, and Opache) located about 15 km SSW of Chuquicamata. Total identified resources for the Chuquicamata district are estimated at 107.4 Mt of fine copper considering a cutoff Cu grade of 0.2 wt% (Codelco Memoria Anual 2011). Inferred resources for the cluster are estimated at about 20 Mt of fine copper, with Toki contributing with ca. 11.2 Mt and Quetena with ~3.8 Mt (Camus 2003; Rivera et al. 2006).
The deposits of the district are located in the Late Eocene–Early Oligocene (43–31 Ma) porphyry copper belt that extends for about 1,400 km, from 18°S to 31°S (Sillitoe 1988; Sillitoe and Perelló 2005). The rocks in the area range in age from Paleozoic to Tertiary. The main structural feature observed is the West Fault, which is part of the Domeyko Fault System (Boric et al. 1990; Dilles et al. 1997) and divides the district in two domains: an eastern domain and a western domain.
The main copper oxide minerals in the Radomiro Tomic deposit are atacamite, copper clays, chrysocolla, and copper wad. Their relative abundance provides the basis for dividing the oxide zone into two major geologic units: the Upper Oxide unit and the Lower Oxide unit. Furthermore, the study of mineral abundances in the oxide zones allowed the definition of an oxide mineral zonation that consists of five mineral assemblages, based on the relative proportion of the three main copper oxide components: atacamite, copper clays, and chrysocolla. These classifications allow both an understanding of the distribution of copper minerals throughout the zone and an interpretation of the supergene processes that formed it.
The Upper Oxide unit is mineralogically heterogeneous. The copper content is furnished, on average, by 40 vol percent atacamite, 31 vol percent copper clays with minor chysocolla and copper wad. The Lower Oxide unit is more homogeneous. Atacamite accounts for 70 vol percent of the copper ore minerals with minor amounts of copper clays and chrysocolla. Copper and chlorine concentrations and porosity are greater in the Upper Oxide unit, whereas hematite, chalcocite, and molybdenite concentrations and specific gravity are greater in the Lower Oxide unit.
The vertical distribution of the Cl/Cu ratio shows a chlorine-deficient zone located between elevations of 2,780 and 2,870 m. Between these elevations, the proportion of atacamite is lower and the proportion of copper clays, chrysocolla, and copper wad is higher than in other portions of either the Upper Oxide or Lower Oxide units.