Geology, Alteration And Mineralization At The Cerro Del Medio Porphyry Au-Cu Deposit, Santa Cecilia Project, Maricunga Belt, Northern Chile

The Cerro del Medio system, situated within the Santa Cecilia-Caspiche district in the southern segment of the Maricunga Belt, exhibits a complex sequence of magmatic and hydrothermal processes that align with regional geological activity during the late Oligocene to early Miocene (25.2â??24.7 Ma). This study highlights the temporal and spatial (i.e., genetic) relationship between subvolcanic diorite porphyry intrusions, hydrothermal alteration, and copper-gold mineralization, providing a framework for future exploration.The hydrothermal system at Cerro del Medio is defined by four main alteration zones: biotite-magnetite (potassic), chlorite-white mica (chlorite-sericite), white mica (sericitic), and aluminosilicate (advanced argillic lithocap). These zones display a halo distribution, transitioning vertically from deep to shallow levels. The biotite-magnetite alteration, observed at depths of 730â??990 meters below the highest elevation, hosts higher grade copper mineralization, while shallow aluminosilicate (lithocap) alteration indicates potential underlying porphyry-style mineralization. Three mineralization stages were identified in this study at Cerro del Medio: (1) magnetite-quartz, marked by chalcopyrite-rich magnetite veinlets; (2) quartz-rich, associated with disseminated chalcopyrite in quartz veinlets; and (3) sulfide-sulfate stage, characterized by a pyrite and anhydrite veining overprint that appears to remobilize and dilute earlier mineralization. The impact on grade of the sulfide-sulfate stage highlights the importance of targeting domains within Cerro del Medio that are unaffected by this mineralization/alteration stage. Comparisons with the nearby Caspiche copper-gold deposit reveal similar alteration zonation and mineralization patterns. The spatial and temporal connection between the two porphyry copper deposits suggest a genetic link: a common magma chamber at depth, and the source of porphyritic intrusions genetically associated with the deposits. These findings support the role of regional magmatism in driving hydrothermal activity and emphasize the potential for additional higher-grade mineralization within the Cerro del Medio system and the Santa Cecilia property.