Early Paleogene magmatism in the northern Andes: Insights on the effects of Oceanic Plateau-continent convergence

Recognition of magmatic events in polyphase arc-continent collision margin is critical for proper tectonic reconstructions that trace the short and changing nature of the configuration of the continental margin. Additionally, the recognition of the origin of detrital volcanic zircons within continental basins becomes a challenge if only distant oceanic and continental magmatic arcs are considered as the only possible source. In this study we report U/Pb zircon ages in isolated plutons that support an early Paleogene magmatic arc that extended ca 700 km along the northern Andean continental margin. Additional detrital zircon Paleogene ages (45-65 Ma), from Paleocene-lower Eocene continental sandstones and volcaniclastic rocks in 19 localities from Colombian and Venezuela Andean basins, indicate that volcanic detritus were supplied from a magmatic arc striking parallel to the subduction zone and also show the existence of intraplate magmatism extending more than 400 km inland. The wide distribution of this Early Paleogene magmatism along the northern South America margin is related to subduction of the buoyant Caribbean plate; the relative short period of magmatism (<10 myr) and sudden stop in early middle Eocene time may be related to the difficulty of the thick plateau to subduct and the relative strike-slip movement of the South America and Caribbean plates since middle Eocene due to northward migration of those plates. (C) 2012 Elsevier B.V. All rights reserved.