Mantle Terrains and Subduction Signals in Central America

9628251费根森该项目的重点将是限制中美洲岛弧火山的地球化学性质。中美洲以前的工作表明，哥斯达黎加北部和尼加拉瓜南部的火山显示出与两个地质历史不同的地幔地体之间的过渡相一致的地球化学成分。这项研究的第一部分将集中于沿弧形这一部分喷口的熔岩的铅同位素组成，目的是确定这一地幔地形边界，并评估大约9000万年前这部分板块通过加拉帕戈斯热点是否影响了下地幔。这项研究的第二个目标将是通过分析沉积物中的BA/La、B/La、U/Th、BA/Th和U/La，来测量紧靠岸上的弧段在过去2-3My期间俯冲特征的时间变化。这将提供必要的基本地层学和地球化学数据，以开发沉积物在汇聚边缘通过地幔循环的现实模型。

9628251 Feigenson This project will focus on providing constraints on the geochemical character of island-arc volcanoes in Central America. Previous work in Central America has indicated that the volcanoes in northern Costa Rica and southern Nicaragua display geochemical compositions that are consistent with a transition between two mantle terrains with different geological histories. The first part of this study will focus on the Pb isotopic composition of the lavas from the vents along this portion of the arc with the purpose of defining this mantle terrain boundary and to evaluate if the underlying mantle was affected by the passage of this portion of the plate over the Galapagos hot-spot at about 90 million years ago. The second objective of this study will be to measure the temporal variation in the subduction signature over the last 2-3 my at the segment of the arc immediately onshore by analysing a core of sediments (DSDP 495) for Ba/La, B/La, U/Th, Ba/Th and U/La. This will provide basic stratigraphic and geochemical data necessary to develop realistic models of recycling of sediments through to the mantle at convergent margins.