Tectono-magmatic controls at the Middle Miocene Esperanza copper porphyry deposit, Central Andes retro-arc, Argentina

Abstract

Esperanza is a porphyry-type prospect located in the retro-arc region of the Pampean flat-slab segment (27–33°S) genetically linked to Middle Miocene magmatism (∼16.7–16 Ma). The porphyry system consists of an early-mineral, an early intermineral and a late intermineral intrusion affected by calcic-sodic, potassic, chloritic - sericitic and sericitic alteration, with chalcopyrite - bornite - molybdenite mineralization. Whole-rock and zircon geochemistry of the mineralized intrusion reveal a high pressure (amphibole-bearing) residual mineralogy, a hydrous character and typical characteristics of fertile suites (high Sr/Y and V/Sc, Eu/Eu∗ > 0.36; 104 x (Eu/Eu∗)/Y > 1 and Dy/Yb < 0.247). The mineralizing magmas formed under a thickened crust after the peak of the compressional stage at ∼20-18 Ma that followed the break-up of the Farallón plate favoring the formation of fertile magmas in the proximal retro-arc region. The significant potential for undiscovered resources confirms the favorability of the Middle Miocene retro-arc magmatism for porphyry-type deposits exploration.