Resumen
- Marginal basins are the result of extensional tectonics along convergent margins. These basins include an early stage of seafloor spreading that, in some cases, is followed by tectonic inversion and deformation of the basin and the formation of a new magmatic arc front. The Early Cretaceous extensional tectonics along the South American Plate caused the development of multiple pre-Andean back-arc and marginal basins along the continental margin. These basins were inverted during the onset of the Andean orogeny in the Late Cretaceous. For instance, in the Northern Andes, the remnants of this Cretaceous history are found in the Central Cordillera, which can be used to understand the magmatic record associated with the birth and death of marginal basins. In this contribution, we integrate U-Pb zircon geochronology, whole-rock geochemistry, Hf and Nd isotopes from Cretaceous volcanic and plutonic rocks at the western margin of Colombia’s Central Cordillera, as well as new zircon U-Pb geochronology and Hf isotopes from the Santa Isabel Stock in the axis of this cordillera. Geochronological results and published data show a magmatic arc record between 78 and 99 Ma that followed the Albian-Aptian MORB-like and less enriched arc signatures associated with the early stages of marginal basin formation. Older pre-Cretaceous detrital and inherited zircons and the observed field relations confirm that this magmatism was built on a thinned continental crust encased by Triassic basement rocks. The documented spatiotemporal and compositional evolution of the Cretaceous arc-related rocks from the western flank of the Central Cordillera documents the transition from a seafloor spreading stage characterized by magmas sourced from an adiabatically melted mantle to the formation of a new arc front that becomes more enriched and influenced by continental crust as the sub-arc mantle is again responsible for magma generation processes.