Petrogenesis of the Miocene Morro del Cobre Cu (Mo)-porphyry deposit in the Frontal Cordillera over the Pampean flat-slab segment, Argentina

Abstract

The Morro del Cobre porphyry (Cu-Mo-Au) deposit, genetically linked to the upper Miocene magmatism (~9–10 Ma), is located at the eastern margin of the Andean Frontal Cordillera of San Juan, Argentina, over the Pampean flat-slab segment (28–33°S) of the Central Andes. The petrogenetic analysis of these rocks reveals an arc affinity and an adakite-like signature with the source magmas evolving under thickened crust conditions which resulted in a high pressure (amphibole ± garnet) residual mineralogy. These mineralizing magmas, that evolved towards shallower magma chambers (<10 km) have hydrous and oxidant character, typical of fertile suites worldwide. The emplacement of Morro del Cobre coincides with the passage of the aseismic Juan Fernandez Ridge as many other Miocene productive porphyry deposits in this segment of the Andes.