The mineral deposits of Panama: Arc metallogenesis on the trailing edge of the Caribbean large igneous province

Abstract

The mineral deposits of the Panama microplate are hosted by a composite volcano-plutonic island arc of Late Cretaceous to Quaternary age developed on an oceanic plateau, the Caribbean Large Igneous Province (CLIP), on the western, trailing edge of the Caribbean Plate. Large igneous provinces are formed by gold and chalcophile element-enriched, mantle plume-related magmas, which may explain the strong metal endowment of Panama of about 32 Mt copper and >984 t gold. The progressive collision of the Panama arc with South America since the middle Eocene resulted in deformation and oroclinal bending of the arc and metallogenic belts. In western Panama, the copper-gold belts young from south to north away from the subduction zone, whereas in eastern Panama the belts young from north to south. An Early Arc of late Campanian to Eocene age (71-34 Ma) developed related to northerly subduction of the Farallon Plate. It has submarine Si-Mn-Fe exhalite deposits in the Nombre de Dios and Montijo belts with showings of Au-rich VMS Cu-Zn mineralization. The San Blas porphyry Cu-Au belt formed in eastern Panama (Rio Pito and other porphyry Cu-Au prospects), while the western continuation, offset by 200 km sinistrally to the Azuero Belt, hosts high sulphidation epithermal Au-Cu deposits (Cerro Quema and others) in porphyry lithocaps.The arc migrated to the northern Azuero-Soná belt in the middle to late Eocene with the formation of epithermal Au-Ag-Pb-Cu mineralization, and a porphyry Au prospect (Soná). A Middle Arc developed in the Oligocene to lower Miocene (31-18 Ma) related to the NE-dipping subduction of the Farallon Plate followed by the Nazca Plate. In eastern Panama, the arc formed intermediate sulphidation epithermal Au deposits in high grade breccias (Espiritu Santo de Cana mine) and carbonates (Rio Mogue prospect), and porphyry Cu mineralization (Ipeti). The eastern Panama arc shut down in the lower Miocene as a result of the change of the Nazca Plate convergence to strike slip. The Middle Arc in western Panama, on the northern side of the Central Cordillera, hosts the Petaquilla belt of porphyry Cu (the supergiant Cobre Panama porphyry Cu-Mo-Au-Ag deposit) and epithermal Au (Molejon) deposits, and probably the epithermal Au deposits of the Veraguas belt. The Later Arc of Miocene to Quaternary age (18-0 Ma) of the Central Cordillera of western Panama hosts low sulphidation epithermal Au vein and breccia-hosted deposits (Capira, Remance, Santa Rosa), high sulphidation epithermal Au deposits (Cerro Lloron, Rio Liri), and porphyry Cu deposits (the supergiant Cerro Colorado porphyry Cu-Mo-Au-Ag deposit and the Cerro Chorcha porphyry Cu-Au deposit). Uplift of the young porphyries in the western part of the belt is related to the subduction of the Cocos aseismic oceanic ridge. Deposits formed by Quaternary weathering include lateritic bauxite and iron ore in the Chiriqui-Veraguas belt; heavy mineral Fe-Ti sands in beach/marine placer deposits in the Gulf of Panama; and extensive placer Au deposits in Northern Darien, Darien, Chepo, Coclé, Veraguas, western Azuero-Soná, and many other small deposits.