Petrogenesis and age of the Peltetec Ophiolitic belt and the Tampanchi ultramafic-mafic complex, Cordillera Real (Ecuador)Geodynamic implications for the evolution of the Andean active margin

Résumé

The aim of this PhD Thesis is to address the geodynamic evolution of the active Andean continental margin during the Mesozoic, centered in the Northern Andean branch of the chain, by means of a petrological approach. Initially, two mafic - ultramafic complexes of nominally Cretaceous age were selected. One related to an oceanic environment (oceanic lithosphere) obducted onto the continental margin termed the Peltetec ophiolitic belt (Peltetec Unit) and a continental volcanic arc intrusion termed the Tampamchi ultramafic – mafic complex, both located in the Cordillera Real of Ecuador. However, the Triassic U-Pb zircon age obtained in this work allow discarding the previous published Ar-Ar plagioclase (albite) Cretaceous age of the Peltetec ophiolite, which must be considered an overprinting age. This unexpected result prevents considering the potential geodynamic relationship of the selected complexes.