Antilla: a supergene enriched porphyry copper deposit in the Andahuaylas-Yauri belt, Peru

The Antilla porphyry copper deposit belongs to the Andahuaylas-Yauri belt of southeastern Peru. Discovery in 2003 was the result of a systematic, regional exploration program in which geology and geochemistry played key roles. An original copper-molybdenum stream geochemistry anomaly was rapidly followed-up by geologic mapping and, drilling. The deposit consists of a supergene enrichment blanket formed at the expense of well developed stockworks of D-type quartz-sulphide veinlets in clastic sedimentary rocks of the Mesozoic Soraya Formation. Hypogene mineralisation is genetically related to a composite porphyry copper-bearing stock and associated dikes with corresponding potassic, sericitic, chlorite-sericite and propylitic alteration zones. Both the potassic and sericitic events contributed copper and molybdenum. The age is constrained by K-Ar dates of between 35.3 +/- 1.0 and 32.3 +/- 0.8 Ma, which correspond to the regional middle Eocene to early Oligocene Andahuaylas-Yauri event. The deposit contains a mineral resource of 154.4 Mt at 0.47% Cu and 0.009% Mo.