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

Valentine Alexander J, Las Vegas NV

Investigators

Abstract

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.