Title: Investigating Geochemical Variability at the Super-Fast Spreading 17º20’S South East Pacific Rise

Program: Geoscience MS

Committee Chair: Dorsey Wanless

Committee: Dorsey Wanless, Darin Schwartz, Mark Schmitz

Abstract: Mid-Ocean Ridges (MORs) produce over 75% of Earth’s volcanic material, providing a window into the mantle composition, melt generation, and crustal accretion processes (Bennett et al., 2019). These magmatic processes are strongly correlated with seafloor spreading rates (Langmuir et al., 1992). Despite decades of research focused primarily at fast and slow spreading ridges, the geochemical variability of Mid-Ocean Ridge Basalts (MORBs) at super-fast spreading ridges is less well constrained (Sinton et al., 1991; 2002). This study investigates the geochemical variability of lavas erupted 17º20’S South East Pacific Rise (SEPR), a super-fast spreading ridge. In 2024, 126 lavas were collected from this segment of the SEPR using the HOV Alvin and wax coring. Major and trace element contents of the basalts are used to quantify spatial and compositional variability in MORBs along this segment. These geochemical data are combined with petrologic modeling to provide a comprehensive understanding of fractional crystallization, partial melting, and mantle source at a super-fast spreading ridge. Additionally, we will utilize the high resolution sampling to investigate how compositions vary spatially along and across the MOR axes. These results are compared to the fast-spreading ridge 9º50’N East Pacific Rise (EPR) and the slow-spreading ridge 14ºN Mid-Atlantic Ridge (MAR) to evaluate the relationship between spreading rate and magmatic processes. The results of this study provide a better understanding of how spreading rate relates to MORB formation and how it impacts the geochemical heterogeneity found along the ridge. This study will offer a reference point for future investigations of MORs with diverse spreading rates and different geochemical variability.