Hf-isotopes in Ocean Island Basalts and Meteorites

该项目将重点研究海洋岛玄武岩（OIB）和陨石的hf同位素，目的是表征地幔并了解非均质（交代成分、俯冲成分等）如何混合回环境地幔。Hf和Nd同位素的陆地变化表明，Lu-Hf和Sm-Nd体系具有良好的相关性，阵列回归得到eHf = 1.35 ？eNd + 3ehf。我建议通过分析来自“极端”同位素或微量元素环境的材料来测试Nd和Hf同位素组成之间的这种良好相关性。Hf和Nd同位素系统将在Nd和Hf系统有不同相关性的地方提供有趣和有力的信息。远洋沉积物、海洋地壳和碳酸盐岩的Lu-Hf-Sm-Nd特征表明，其演化线的坡度与陆相或海洋玄武岩阵列不同。这些独特的微量元素和Hf-Nd同位素特征可以相对容易地识别海洋玄武岩中的这些成分，并可以很好地估计这些成分分离的持续时间（地幔非均质性）。海洋岛屿玄武岩阵列如此明确的事实表明，将地幔成分从阵列中移动的过程或成分要么在体积上微不足道，要么在相对较短的时间尺度上混合回来。了解这些混合过程的第一步是识别玄武岩来源中的不同类型的物质（远洋沉积物、海洋地壳等）和过程（熔融、交代等）。我建议从萨摩亚岛链、夏威夷库劳火山和沃尔维斯岭获取玄武岩的hf同位素数据。该项目的第二个组成部分是确定球粒陨石中的Lu/Hf-Sm/Nd分异是否与地面阵列观测到的地球上的时间积分分异显著。目前有三种不同的hf - nd同位素空间中块状地球的同位素组成估算方法。现有资料表明，陨石的Hf和Nd同位素组成具有相关性，且陨石阵列与OIB阵列呈锐角。我建议分析一组陨石的Hf和Nd同位素组成，从而更好地定义陨石阵列。

SaltersEAR-0124965This project will focus on Hf-isotope studies of ocean island basalts (OIB) and meteorites with the goal of characterizing the mantle and understanding how heterogeneities (metasomatic component, subducted components etc.) are mixed back into the ambient mantle. The terrestrial variation in Hf and Nd isotopes indicates that the Lu-Hf and Sm-Nd system are well correlated and regression of the array leads to eHf = 1.35 ?eNd + 3 eHf. I propose to test this excellent correlation between Nd and Hf isotopic compositions by analyzing materials from "extreme" isotopic or trace element environments. The Hf and Nd isotope systematics will provide interesting and powerful information in places where the Nd and Hf systems are differently correlated. Lu-Hf-Sm-Nd characteristics of pelagic sediments, oceanic crust as well as carbonatites imply evolution lines that have a different slope than the terrestrial or ocean basalt array. These distinctive trace element and Hf-Nd isotopic characteristics allows for relatively easy recognition of these components in oceanic basalts as well as good estimates on the duration of isolation of these components (mantle heterogeneity). The fact that the oceanic island basalt array is so well defined indicates that processes or components that would move mantle compositions off the array are either insignificant in volume or are mixed back in on relatively short timescales. A first step towards understanding these mixing processes is recognition of the different type of materials (pelagic sediment, oceanic crust etc) and processes (melting, metasomatism etc) in the sources of the basalts. I propose to obtain Hf-isotope data for basalts from the Samoan Island chain, from Koolau volcano, Hawaii, and from Walvis Ridge. A second component of the project is the determination whether Lu/Hf-Sm/Nd fractionation in chondrites is significantly different then the time integrated fractionations in earth as observed by the terrestrial array. Presently there are three different estimates for the isotopic composition of bulk Earth in Hf-Nd-isotope space. The available data indicate that Hf and Nd isotopic compositions of meteorites are correlated and that the meteorite array is at sharp angle with the OIB array. I propose to analyze a suite of meteorites for Hf and Nd isotopic composition and thereby better define the meteorite array.