Porphyry and Hydrothermal Cu-Au Deposits: A Global Perspective

The Radomiro Tomic (RT) porphyry copper deposit is located 5 km north of the giant Chuquicamata deposit and is concealed beneath 40 to 150 m of Neogene gravels. The orebody is hosted by the Chuqui Porphyry, a medium to coarse-grained granodioritic to monzogranitic intrusion elongated north-south, and 1 km wide, which intruded the Early Cretaceous Elena Granodiorite. Towards its western side the Elena Granodiorite is truncated by the West Fissure, a north-south striking, post-mineral wrench fault. The Chuqui Porphyry at RT is altered to a K-silicate assemblage containing A-type quartz-K feldspar veins and biotitized hornblende phenocrysts. Sericitic alteration is less developed and controlled mostly by NE-striking faults.
The deposit consists of a horizontal blanket of oxide copper minerals that extend for 4.3 km north-south and up to 800 m east-west, with a thickness varying between 180 and 200 m. Underlying this oxidation zone, there is an immature supergene enrichment zone characterized by weakly developed chalcocite and covellite. The underlying hypogene zone extends for >200 m in depth.
Oxide mineralization consists mainly of atacamite and chrysocolla that define two distinct horizons. The upper horizon, the Upper Oxide unit, is characterized by chrysocolla, copper clays and lesser atacamite. The underlying Lower Oxide unit is more homogenous and atacamite dominates over chrysocolla and copper clays.
A total geological resource of more than 1000 million tonnes averaging 0.56% total Cu is estimated for the RT deposit.