Eclogitization of continental lithosphere from subduction zone devolatilization

Subduction zones are regions where one tectonic plate slides and sinks beneath another, and they have been a major focus of research in the field of Earth Science due to their association with mountain-building and with natural hazards like earthquakes and volcanic eruptions. Improving the understanding of processes involving the sinking of these rocks into the Earth's interior, known as foundering, holds valuable insights for subduction zones and continental crust research.

The foundering process requires the rocks are of greater density than their surroundings. This project will explore the processes controlling the transformation of rocks in the lower continental crust to greater density resulting from mineral transformations and the degree to which the process requires fluid-mediated reactions common in subduction zones.

The results of this modeling study will be compared to rocks found in Norway that are thought to have returned to the surface after undergoing this densification process. The research project is led by an early career investigator, who will gain valuable experience by spearheading this study and mentoring a postdoctoral scholar. To ensure transparency and encourage collaboration beyond this project, all the project's data and results will be made publicly accessible, and their findings will be presented at conferences both nationally and internationally to a variety of audiences.

This project will contribute to the training of undergraduate researchers, K-12 science teachers, and high school students from diverse backgrounds. This will be accomplished through providing hands-on research experience in Georgia Tech’s Summer Research Experiences for Undergraduates (REU) program, and collaboration with the Center for Education integrating Science, Mathematics, and Computing (CEISMC) to introduce coding and Earth Science concepts to K-12 students in the Atlanta Metro area.

The Georgia Intern Fellowships for Teachers (GIFT) program will provide funding to support a K-12 teacher and high school students, enabling them to develop grade-appropriate teaching materials and science projects. These educational resources will be showcased at local science fairs, with the goal to inspire young minds and foster an early interest in Earth Science and coding.

This project seeks to address a notable knowledge gap concerning the mechanisms behind mountain-building processes beneath the Earth's surface, known as orogenesis. The primary focus of this project is on understanding the role of reactive fluids and the thermodynamics of eclogitization in the deep crust. To accomplish this, the project aims to develop advanced models that integrate the thermodynamics of eclogitization with simulations of fluid flow.

These models will enable researchers to investigate the interactions between fluids and the eclogitization process and determine the timescales associated with metamorphism and the sinking of the lithosphere. The project will consist of two interconnected numerical modeling studies. First, models of disequilibrium thermodynamics will be developed to capture the behavior of key mineral phases and reactions.

These models will then be coupled with simulations of fluid flow and rock deformation. To validate and gain insights from the models, the researchers will compare the model outputs with the grain-scale to regional-scale structures observed in well-documented eclogites from Norway. This analysis will allow them to test the hypothesis that lithospheric foundering is a global phenomenon and a consequence of orogenesis.

Moreover, the models will provide valuable information about the specific conditions under which eclogitization becomes thermodynamically favorable and the timescales required for significant accumulations of eclogite in the lower crust. The researchers will explore these processes across a diverse range of initial rock compositions, representing the wide variety found in the Earth's continental crust.

Ultimately, the project aims to enhance our overall understanding of the complex metamorphic and metasomatic processes that occurs during mountain formation. This project was supported by both the Geophysics and the Petrology and Geochemistry programs.

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.