The Galapagos Plume Geodynamics, a Geochemical Approach

本研究的目标是提供额外的约束条件，以提高我们对加拉帕戈斯烟羽及其与加拉帕戈斯传播中心的相互作用的认识。与加拉帕戈斯群岛的地质演化有关的两个科学问题将作为本研究的一部分加以解决。首先，为了了解哪些过程导致了加拉帕戈斯熔岩的地球化学变化，以及哪种现有模型最适合解释这些变化，我们提出了一项将氧和放射性同位素分析与同一样品集的主要元素和微量元素组成相结合的研究。其次，我们建议发展加拉帕戈斯群岛下地幔上升流速度和融化的地球动力学图像。传统上，地幔上涌和熔融的地球动力学图像是通过详细的地球物理研究获得的。在过去的15到20年里，对u系列（238U-230Th, 230Th-226Ra, 235U-231Pa）的研究使科学家们能够利用地球化学工具绘制地幔上涌和融化的图像。与其他放射性成因同位素系统相比，u系列的短半衰期将使我们能够初步了解当今的地幔组成，由一套熔岩代表的融化程度，并估计群岛不同地点的地幔上涌。将u系列、氧和其他放射性同位素与同一样品中测量的主要元素和微量元素含量结合正在进行的地球物理研究，将为我们获得加拉帕戈斯群岛羽流及其周围软流圈的可靠地球动力学图像提供最好的机会。

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.