U-Pb thermochronology, geochronology and geochemistry of NW South America: rift to drift transition, active margin dynamics and implications for the volume balance of continents

Abstract

We investigate the Permian – Early Cretaceous (~280 – 113 Ma) tectonic evolution of north-western South America. A new quantitative isotopic and geochemical dataset is presented, which includes, i) 53 U-Pb zircon dates of magmatic rocks and 8 detrital zircon U-Pb age spectra of metasedimentary rocks, ii) 49 weighted mean zircon Hf isotopic analyses of magmatic rocks, iii) 82 whole rock geochemical analyses, including Sr-Pb-Nd isotopic analyses, and iv) apatite U-Pb and 40Ar/39Ar thermochronological data. All of these new data have been acquired from the Eastern Cordillera of Ecuador and the Central Cordillera of Colombia. These data are used to investigate i) the mechanisms and timing of continental fragmentation from back-arc basin extension to the generation of oceanic lithosphere (Chapter 1), ii) the distinction between accretionary and in-situ growth at active continental margins and the implications for the volume balance of continental crust (Chapter 2), and iii) mechanisms of Pb loss in apatite, and the applications of high temperature (~370-570°C) thermochronology for studying the thermal history of the Earth's crust (Chapter 3).