Geology and geochronology of the Don Javier Cu-Mo porphyry deposit, southern Peru

Abstract

The Don Javier porphyry Cu-Mo deposit is located in the Yarabamba district of the Arequipa region, Peru, which represents the northwestern end of the Paleocene-early Eocene Cu belt of the central Andes, extending from northern Chile into southwestern Peru. The deposit occurs around the contacts of a dacite porphyry stock emplaced into the pre-mineralization and Yarabamba granodiorite batholith. The intrusions display a telescoped sequence of alteration, from shallow sericitic to deeper chloritic-sericitic, with minor remnant potassic assemblages, which are surrounded by propylitic zones. EB-, M-, EQ-, SQ-, and D-type veinlets occur in all alteration zones. The higher Cu and Mo grades are mainly associated with the widely distributed sulfide-quartz veinlets within the potassic and chlorite-sericite overlapping zones. The mineralized zone measures ∼500 m in width (NE-SW) by ∼800 m in length (NW-SE). Uranium-Pb zircon ages show that the Yarabamba granodiorite plutons were emplaced at ∼ 64.6 Ma and subsequently intruded by the inter-mineralization dacite porphyry intrusions at ∼ 59.9 to 59.5 Ma. Molybdenite Re-Os ages indicate that the deposit formed between ∼ 60.5 and 59.6 Ma. Younger molybdenite Re-Os ages (∼45.4 to 44.4 Ma) obtained in the deep parts of the altered rocks suggest that the deposit might have been overprinted by later hydrothermal activity in the Eocene. The success of exploration at Don Javier emphasizes that traditional methods such as geologic and geophysical mapping followed by timely drilling tests can still be effective in a mature metallogenic belt.