EAR-PF: A high-resolution 142Nd/144Nd record of mantle-derived rocks to constrain mantle stirring rate and tectonic regimes

Hyung Eugenia, Pasadena CA

Investigators

Abstract

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Dr. Eugenia Hyung has been granted an EAR Postdoctoral Fellowship to carry out research and education plans at Harvard University and University of Nevada Las Vegas. Dr. Hyung will use high precision measurements of the composition of rocks from deep in the Earth and deep in time to better understand Earth’s history. Plate tectonics – the movement of large rocky plates over the surface of the Earth – influences the fate of Earth’s evolution. Through plate tectonics, the surface of the Earth is shaped by the mantle below, influencing mountain building, creating the ocean floor, and generating many major earthquakes and volcanic eruptions. Yet the origin and history of plate tectonics is not well understood. Understanding how the mantle is shaped throughout time, will help to answer these questions. Because high-precision chemical data are missing from key time intervals throughout geologic history, questions remain about precise limits on how and at what rate the mantle becomes homogenous through time. This project aims to address these questions by acquiring high-precision data from rocks that are billions of years old to establish the stirring time of the mantle. The work will be carried out under the mentorship of Professor Stein B. Jacobsen (Harvard University) and Professor Shichun Huang (University of Nevada, Las Vegas). While conducting this research, Dr. Hyung will provide mentorship to both graduate and undergraduate students, be involved in developing teaching methods and courses, and engage in outreach activities that promote understanding and appreciation of the Earth in the context of current issues, as well as its evolution throughout time. The presence of 142Nd/144Nd variability well after the extinction of the short-lived 146Sm isotope has led to the idea that the mode of tectonics early in Earth’s history would have been fundamentally different from the present-day form of tectonics to have enabled the preservation of geochemical heterogeneity over billions of years. The mode of tectonics (mobile vs. stagnant lid) is thought to exert influence on the efficiency of mantle mixing, and homogenization of the silicate Earth. Through this project, PI Dr. Eugenia Hyung aims to constrain the stirring rate of the Earth’s mantle and to deduce the dominant mode of tectonics in the time frame in which this occurs, by (i) filling the gap in the 142Nd/144Nd isotope record by performing high-precision measurements on Proterozoic samples and (ii) derive the stirring rate of the mantle during this time period through modeling, using the data as constraints. PI Dr. Eugenia Hyung is well-positioned to undertake the proposed study, having previously developed the methods in measuring 142Nd/144Nd ratios at a very high degree of precision while having experience in modeling. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.