EAGER: Recycled Carbonate-Rich Sediment in the Hawaiian Plume? Evidence from Ca Isotopes

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。拟议的EaGER（探索性研究早期拨款）旨在促进一种新的地球化学工具（Ca同位素）在地幔地球化学领域的应用，并以夏威夷熔岩为例进行研究。这是一项仍处于早期发展阶段的探索性研究，希望通过进一步的工作证明Ca同位素可以作为地幔源中再循环沉积物的可靠测试。该计划涉及哈佛大学的两位早期职业科学家（黄和法卡斯），他们将结合他们在不同领域的专业知识，并将在最先进的分析技术及其在地球科学中的应用方面教育和培训研究生和本科生。拟议的研究还将利用美国国家科学基金会以前的投资，使用由美国国家科学基金会项目资助的夏威夷科学钻探项目和库劳科学钻探项目中回收的样本。Ca是地球上含量第五丰富的元素，是地幔中存在的四种主要矿物中的三种的主要成分，它在我们理解地幔熔融和地幔对流中起着重要作用。Ca同位素分析的最新进展表明，现代和古代碳酸盐的同位素差异很大，古代碳酸盐的Ca同位素比值（低于44Ca/40Ca）明显低于现代地幔值。因此，古碳酸盐进入地幔的再循环可以引入幔源熔岩中Ca同位素的变化。夏威夷火山是地幔柱衍生火山作用的最好例子之一，对夏威夷熔岩的广泛的地球化学和同位素研究表明，夏威夷熔岩的岩石成因中有重要的古海洋地壳和沉积物的再循环。EaGER的最终目的是扩展初步分析，这些分析表明，一些夏威夷熔岩的44Ca/40Ca值略低于典型的地幔44Ca/40Ca值，这可能是由于再生碳酸盐沉积物的结合。如果完全成功，结果将对我们目前对地幔对流和全球碳酸盐旋回的理解以及岩浆过程中Ca同位素的行为产生重大影响。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5) The proposed EaGER (Early Grant for Exploratory Research) is designed to facilitate the application of a new geochemical tool (Ca isotopes) to the field of mantle geochemistry using the well-studied Hawaiian lavas as a case study. This is an exploratory study that is still in its early stages of development and, hopefully, will demonstrate through further work that Ca isotopes can be used as a reliable test of recycled sediments in mantle sources. This proposal involves two early career scientists (Huang and Farkas) at Harvard University who will combine their expertise in different fields, and will educate and train graduate and undergraduate students in state-of-the-art analytical techniques and their applications to geosciences. The proposed research will also leverage previous NSF investments by using samples recovered from Hawaii Scientific Drilling Project and Koolau Scientific Drilling Project that were funded via NSF programs. As the fifth most abundant element on the Earth, Ca is a major constituent of three out of the four major minerals present in the Earth's mantle, and it plays an important role in our understanding of mantle melting and mantle convection. Recent development in Ca isotopic analysis revealed large isotopic variations in modern and ancient carbonates, with ancient carbonates having significantly lighter Ca isotopic ratios (lower 44Ca/40Ca) than modern mantle values. Recycling of ancient carbonates into the mantle can, therefore, introduce Ca isotopic variations in mantle-derived lavas. Hawaiian volcanoes are one of the best examples of mantle plume-derived volcanism, and extensive geochemical and isotopic studies on Hawaiian lavas indicate that recycled ancient oceanic crust and sediments are important in the petrogenesis of Hawaiian lavas. The ultimate purpose of this EaGER is to expand preliminary analyses that have shown a slightly lower 44Ca/40Ca than typical mantle 44Ca/40Ca value for some Hawaiian lavas that could be due to the incorporation of recycled carbonate sediments. If fully successful, the results will have great impact on our current understanding of mantle convection and global carbonate cycles, as well as the behavior of Ca isotopes during magmatic processes.