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（探索性研究早期赠款）旨在促进一种新的地球化学工具（钙同位素）在地幔地球化学领域的应用，使用经过充分研究的夏威夷熔岩作为案例研究。这是一个探索性的研究，仍处于发展的早期阶段，并希望通过进一步的工作，将证明钙同位素可以作为一个可靠的测试回收的沉积物在地幔源。这项建议涉及哈佛大学的两名早期职业科学家（Huang和Farkas），他们将联合收割机结合他们在不同领域的专业知识，并将教育和培训研究生和本科生掌握最先进的分析技术及其在地球科学中的应用。拟议的研究还将利用NSF以前的投资，使用从夏威夷科学钻探项目和Koolau科学钻探项目中回收的样本，这些项目是通过NSF项目资助的。作为地球上第五丰富的元素，Ca是地球地幔中四种主要矿物中三种的主要成分，它在我们理解地幔熔融和地幔对流中起着重要作用。钙同位素分析的最新进展显示，现代和古代碳酸盐岩中存在较大的同位素变化，古代碳酸盐岩的钙同位素比值（44 Ca/40 Ca）明显低于现代地幔值。因此，古老的碳酸盐再循环到地幔中，可以在幔源熔岩中引入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地球化学和同位素研究表明，再循环的古洋壳和沉积物在夏威夷熔岩的岩石成因中很重要。EaGER的最终目的是扩展初步分析，初步分析表明，一些夏威夷熔岩的44 Ca/40 Ca值略低于典型的地幔44 Ca/40 Ca值，这可能是由于再循环碳酸盐沉积物的掺入。如果这一研究取得成功，将对我们目前对地幔对流和全球碳酸盐循环的认识，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.