Cenozoic magmatism in northwestern Colombia tends to become progressively younger from west to east, following an “Andean” model. It is possible to distinguish four sub-belts. The oldest is composed of the Paleocene-Eocene Mandé batholith, an island arc that was accreted to the South American continent in Miocene time as part of the Panamá-Baudó-Mandé terrane. After the collision, a subduction zone was formed at its present position at the Pacific margin, and it has been responsible for the other three sub-belts that are recognized: (1) a late Miocene sub-belt along the axis of the Western Cordillera, with small tonalitic, monzonitic, and dioritic stocks; (2) a late Miocene to Pliocene sub-belt in the Cauca Valley, characterized by explosive andesitic volcanism followed by intrusion of andesitic and dacitic plugs, as well as alkali-basalt dikes; and (3) a Pliocene to Quaternary volcanic arc along the axis of the Central Cordillera that forms part of the modern Northern Volcanic zone of the Andes.