EAPSI: Using New Tools in Mantle Geochemistry to Interpret a Nickel Anomaly in Basalt in Niihau Island

海岛火山地球化学研究是研究地球--S地幔过程和特征的主要途径之一。海岛玄武岩中镍(Ni)的富集度是该领域一个重要的争议话题。该项目将试图通过分析玄武岩样品中发现的矿物橄榄石晶体中的铁和镁(铁和镁)同位素来确定这种镍浓缩的来源。中国科技大学将与我的东道主研究员黄芳博士合作，对几个橄榄石晶体进行铁-镁同位素分析。黄博士和他的几位同事已经开发出了在包括橄榄石在内的几个地质样本中检测铁镁同位素的精确方法。该项目的结果将确定在一个研究相对较少的海洋岛屿上橄榄石中镍的地幔来源。该项目将分析夏威夷尼豪岛玄武岩样品中的橄榄石晶体，以确定镍富集的岩浆来源。初步数据表明，在S橄榄石晶体中，当样品中的氧化镁成分给定时，铁镁互扩散过程可能导致镍的增加。为了确定这一过程是否有助于镍的富集，将使用新的地球化学方法对玄武岩样品中的几个橄榄石晶体进行Fe-Mg同位素分析。这项分析将在科大的多收集器电感耦合等离子体质谱仪(MC-ICPMS)上进行。这些分析的数字输出将显示Fe-Mg同位素在橄榄石晶体直径上的分布，从而有可能推断Nihau镍的富集源。该奖项由东亚和太平洋暑期学院项目资助一名美国研究生的暑期研究，由美国国家科学基金会和中国科技部联合资助。

The study of ocean-island volcanic geochemistry is one of the main gateways for investigating the processes and characteristics of the Earth?s mantle. One important disputed topic in the field is the enrichment of nickel (Ni) in ocean-island basalt. This project will attempt to determine the source of this Ni enrichment by analyzing iron and magnesium (Fe and Mg) isotopes within crystals of the mineral olivine found in a sample of basalt. Fe-Mg isotopic analysis of several olivine crystals will be conducted at the University of Science and Technology of China (USTC) in collaboration with my host researcher, Dr. Fang Huang. Dr. Huang and several of his colleagues have developed precise methods for detecting Fe-Mg isotopes in several geologic samples, including olivine. The outcome of this project will determine the mantle source of Ni enrichment in olivine at a relatively understudied ocean-island.This project will analyze olivine crystals in a basalt sample from the Hawaiian island of Niihau in order to determine the magmatic source for Ni enrichment. Preliminary data has indicated that the process of Fe-Mg interdiffusion likely contributed to an increase in Ni at a given magnesium oxide composition in the sample?s olivine crystals. In order to confirm whether this process contributed to Ni enrichment, Fe-Mg isotopic analysis of several olivine crystals from the basalt sample will be conducted using new methods in geochemistry. This analysis will be performed on a multi-collector inductively-coupled plasma mass-spectrometer (MC-ICPMS) at USTC. Digital output from these analyses will display distribution of Fe-Mg isotopes across the diameter of the olivine crystals, making it possible to infer the source for Ni enrichment at Niihau. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Chinese Ministry of Science and Technology.