Isotopic Geochemistry of Oceanic Mantle Sections and the Dating of Quaternary Volcanics

本文拟开展：1)深入研究基性岩和超基性岩中Re-Os、Sm-Nd、Rb-Sr体系和铂族元素的同位素地球化学特征，研究显生宙地幔源、分异产物及其演化；230Th等U、Th衰变系列中间子序列在全新世和晚更新世火山岩定年中的应用，以及这些火山岩与岩浆源和斑晶形成时代的关系。除了手头的样品外，还将在关键地点进行实地工作，以获得非常新鲜的材料。这些问题将在三年的时间里，利用新开发的铂族元素的负热离子质谱技术和新一代高透射度高丰度灵敏度质谱（丰度灵敏度优于5 × 10-10 / 2amu）来解决。最近开发的分析化学程序将用于分离超低浓度的元素，并且污染可以忽略不计。这项工作将导致对待研究岩石起源的新的科学认识，以及改进分析技术的发展。

This proposal is to conduct: 1) an in depth study of the isotopic geochemistry of the Re-Os, Sm-Nd and Rb-Sr systems and of platinum group elements in basic and ultramafic rocks for the purpose of studying mantle sources, their differentiation products,and their evolution over the Phanerozoic; and 2) the application of 230Th and other intermediate daughters of the U and Th decay series to the dating of Holocene and late Pleistocene volcanics and the relationship of these volcanics to magma sources and the times of formation of phenocrysts. In addition to samples at hand, filed work will be conducted to obtain very fresh materials at key localities. These problems will be attacked over a three-year period, using newly developed mass spectrometric techniques of negative thermal ion mass spectrometry of the platinum group elements and a new generation high abundance sensitivity mass spectrometer (abundance sensitivity better than 5 x 10-10 for 2 amu) with high transmission. Recently developed analytical chemical procedures will be used to separate elements at ultra low level concentrations efficiently and with negligible contamination. This work should result in new scientific understanding on the origins of the rocks to be studied, as well as the development of improved analytical techniques.