Compositional Domains in Altered Oceanic Crust

大洋中脊玄武岩的产生、蚀变、俯冲和再循环导致了海水、地幔、火山弧和陆壳之间的一级化学迁移。研究这一海洋生物生命周期每个阶段的化学过程需要了解前一个阶段的知识。一个最重要的缺失环节是对俯冲前洋壳变化过程中的大量化学变化缺乏了解。这项研究将包括仔细记录原生和次生矿物学、模式丰度估计以及对DSDP 417A、417d和418A地点的样品进行综合化学和同位素分析。PI将确定一些蚀变敏感参数，包括K2O、H2O、CO2、B的浓度，以及三角洲O18、Sr87/86和DeltaB11的同位素比值。类似岩性的这些参数的概况将提供对海底变化影响随深度衰减的洞察力。通过监测地壳上部的这些参数，可以定量估计进入大洋地壳的海水数量。对417A、417D和418A点进行了广泛的研究，但没有关于稳定同位素或放射性同位素的数据，只有少数几种微量元素，对枕缘变化极大的分析也太少。私人投资总监将提供这些分析。

The generation, alteration, subduction and recycling of mid-ocean ridge basalts results in first order chemical transport between seawater, the mantle, volcanic arcs and continental crust. The study of chemical processes in each phase of this oceanc rustal life cycle requires knowledge of the previous one. A most significant missing link is the poor understanding of the bulk chemical changes during alteration of the oceanic crust prior to subduction. This study will involve careful documentation of the primary and secondary mineralogy, modal abundance estimates and an integrated chemcial and isotopic analysis of samples from DSDP Sites 417A, 417D, and 418A. The PIs will determine a number of alteration sensitive parameters, including the concentrations of K2O, H2O, CO2, B, and the isotopic ratios of delta O18, Sr87/86, and deltaB11. A profile of these parameters for similary lithologies will provde insights into the decay of the effects of seafloor alteration with depth. By monitoring these parameters in the upper portions of the crust, quantitative estimates of the amount of seawater entering the oceanic crust will be possible. Sites 417A, 417D, and 418A have been studied extensively, however, there is no data on stable or radiogenic isotopes and only a few trace elements, and there are too few analyses of extremely altered pillow margins. The PIs will provide these analyses.