Crustal growth and modification by fringing arcs in the Northern Andes: insights from the Western Colombian Andes

The growth of continental margins by vertical addition of magmatic crust during extensional events and the formation of intra-arc, back-arc or fore-arc basins have shown to be a major element on the Cretaceous evolution of the Circum-Pacific margins. New field and geochronological data integrated with published geochemical and regional geology was used to understand the tectonic processes that built the Cretaceous to Early Paleocene western margin of the Northern Andes in Colombia. The new results suggest an early Albian-Aptian re-inception of subduction with a significant growth of fore-arc crust followd by the construction of an arc in a transpressive setting that continue until < 80 Ma. The margin began to be modified by the approach of a western allocthonous oceanic arc that end in an oblique Molucca-sea type collision of a divergent double subduction that seems to promote significat underthrusting of the arc-fore-arc sytem under the continental margin. By ca. 70 Ma alkaline magmatism and thick syn to late collisional turbidite sedimentation mainly derived from the continental plate filled the wester margin and maybe related to a late slab break-off event that follow collision.