Petrogenesis of Hawaiian Tholeiites: Constraints from Non-Traditional Stable Isotopes

University Of Nevada Las Vegas, Las Vegas NV

Investigators

Abstract

This award will support an early career investigator to study the application of non-traditional stable isotopes, a novel tool, in the fields of high-temperature geochemistry and petrology. The ultimate goal of the project is to better understand the origin of Hawaiian volcanism. The proposed research involves educating and training graduate and undergraduate students in state-of-the-art analytical techniques and their applications to geosciences. The project will also help this early-career scientist build a state-of-the art laboratory that will support the research of a number of researchers and students not only at his own institution but also in other institutions allied to the Nevada System of Higher Education. The analytical geochemistry laboratory overseen by this investigator will serve a broad area of earth and environmental sciences, as well as to serve as regional infrastructure in an EPSCoR state. Finally, the proposed research will leverage previous NSF investments by using samples recovered from previous NSF funded programs, such as Hawaii Scientific Drilling Project. The Earth's mantle is thought to be composed of olivine-rich peridotite. However, the major element characteristics of some ocean island basalts (OIB), such as some Hawaiian lavas, cannot be produced by partial melting of peridotite. A variety of models have been suggested to explain the SiO2 variation in Hawaiian lavas, including melt-mantle reaction model, dacite magma model, and secondary pyroxenite model. On a global scale, Hawaiian lavas define the high-SiO2 endmember of the OIB compositional-isotopic spectrum. Consequently, understanding the origin of SiO2 variation within Hawaiian lavas is important in understanding the petrogenesis of global OIBs. Lavas from Mauna Kea, Koolau and Kahoolawe define two endmembers of the compositional-isotopic spectrum of Hawaiian lavas. The investigator proposes a detailed and systematic Mg and Fe isotopic study of Mauna Kea and Kahoolawe lavas to resolve this question. Koolau lavas have been extensively studied for Mg, Fe and Ca isotopic compositions. This effort expands on an ongoing study of the Ca isotopic compositions of these samples. It is suggested that non-traditional stable isotopic studies based on major elements such as Ca, Mg, and Fe may provide clues as to the nature of the compositional and isotopic variations shown in Hawaiian lavas. In the future, such approach can be applied to global OIBs to constrain their petrogenesis.