The Galapagos Plume Geodynamics, a Geochemical Approach

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SaalEAR-0207136 The goals of this study are to provide additional constraints to improve our knowledge of the Galapagos plume and its interaction with the Galapagos Spreading Center. Two scientific issues pertaining to the geological evolution of the Galapagos will be addressed as part of this study. Firstly, in order to understand which processes are responsible for the geochemical variations of the Galapagos lavas and which current model is most suited to explain them, we propose a study that combines oxygen and radiogenic isotope analyses with major and trace elements compositions on the same sample set. Secondly, we propose to develop a geodynamic picture of the upwelling velocities and melting of the mantle beneath the Galapagos archipelago. Traditionally, geodynamic pictures of mantle upwelling and melting have been obtained through detailed geophysical studies. In the last 15 to 20 years, the study of U-series (238U-230Th, 230Th-226Ra, 235U-231Pa) has allowed scientists to image the mantle upwelling and melting using a geochemical tool. In contrast to other radiogenic isotope systems, the short half lives of the U-series will allow us to get a first look at the present-day mantle composition, the extent of melting represented by a suit of lavas and estimate the mantle upwelling at different points in the archipelago. The combination of U-series, oxygen and other radiogenic isotopes with major and trace elements contents measured in the same samples combined with ongoing geophysical studies, will provide our best opportunity to obtain a reliable geodynamic image of the Galapagos plume and the surrounding asthenosphere.